CN209105014U - Inductive type switch power converter and its load current detection circuit - Google Patents

Abstract

In inductive type switch power converter and its load current detection circuit, obtains in A and inductive current rises or falls the period and is denoted as T respectively in B switching signal period_AAnd T_B, obtain the B inductive current and rise or fall the start time of period by 0.5T_APoint moment T in i.e. first at the time of afterwards_MBThe start time for rising or falling the period with the C inductive current rises by 0.5T_BPoint moment T in i.e. second at the time of afterwards_MC；Sampling hold circuit point moment T in first_MBWith second in point moment T_MCSample load current, the point moment T in first_MBTo point moment T in second_MCPeriod is sampled using distinct methods according to switch power converter type and operating mode difference and keeps the load current sampled value, and is used as load current of the switch power converter in a switch periods.

Description

Inductive type switch power converter and its load current detection circuit

Technical field

The utility model relates to the technical fields of switch power converter circuit, and in particular to a kind of inductive type Switching Power Supply Converter load electric current detecting method and circuit improve load current while reducing load current detection circuit complexity The accuracy of detection.

Background technique

Switch power converter circuit is one of most important type in power supply voltage converter, is primarily adapted for use in voltage change The situation changed, the circuit form of DC/DC switch power converter include the charge pump circuit realized with capacitor, also include using inductance Voltage-dropping type Buck switching circuit, booster type Boost circuit and the negative electricity volt circuit Buck-Boost circuit of realization.In order to switch Electric current is accurately controlled in converter circuitry of power, needs accurately to detect load current.

In the prior art, common load current detection method first is that technical solution as shown in Fig. 2, in inductance One inspection leakage resistance of series connection on current path realizes that load current is examined by voltage on operational amplifier amplification inspection leakage resistance It surveys, in the scheme of external inspection leakage resistance, operational amplifier needs to constantly detect the voltage at resistance both ends, to the speed of operational amplifier Degree and required precision are high.

In technical solution as shown in Fig. 2, it is assumed that circuit terminal V1 is the input terminal of external power supply, and V2 is switch The power output terminal of power adapter, the switch power converter is the Switching Power Supply conversion based on Buck type circuit at this time Device.Conversely, V2 is the input terminal of external power supply if circuit terminal V1 is the power output terminal of switch power converter, this When the switch power converter be switch power converter based on Boost type circuit.

When switch power converter work under Buck type circuit-mode, flow through the electric current on load detecting resistance Rsen Also inductance is flowed through, so amplifier can to detect indirectly and flow through inspection by the voltage on detection load detecting resistance Rsen The electric current of leakage resistance Rsen and inductance.The circuit of this structure needs to connect a load detecting resistance Rsen to inductance, this The efficiency of switch power converter is lost, and needs the voltage at additional pin detection resistance both ends, and high-precision inspection is flowed Resistance is more expensive.

In the prior art, common load current detection method second is that as shown in Fig. 3 passes through power tube current mirror The technical solution for detecting load current is surveyed in the method for load current by power tube current microscopy, needs a mirror image pipe Q3, The ratio of mirror image pipe Q3 and power tube Q1 are 1:K.For the switch power converter based on Buck type circuit, stream The sum of electric current of overpower pipe Q1 and power tube Q2 is load current.If power tube Q1 and power tube Q2 will be detected, Circuit will be extremely complex.Although the electric current of Buck type switch power converter circuit is continuous, if two power tubes are opened The electric current for closing pipe and continued flow tube will detect, and need two sets of load current detection circuits, and testing cost is relatively high, implement multiple It is miscellaneous.

In the certain load detecting circuits of the prior art, using any one in detection power tube Q1 or power tube Q2 The peak point current of power tube, and using the load current kept to peak point current sampling as a switch periods.Such as Fig. 4 and Shown in 5, it is obvious that there are shades between the electric current and true load current kept according to the sampling of power tube Q1 peak point current Partial error.In ccm mode, error has compared for switch power converter work based on Buck type circuit Greatly, error is as shown in the dash area in Fig. 4；When load current is smaller and smaller, after DCM mode, as shown in figure 5, The ratio for the area that its error, that is, shaded area accounts for whole figure is bigger, and detection circuit error is also bigger.

In conclusion in Buck type switch power converter circuit, if only with one of power tube is detected as switched Peak point current during pipe conducting, and the electric current calculated during continued flow tube is connected is simulated with this, the error of simulation is very big, and also Need operational amplifier that all there is good responding ability within the period of entire load detecting, to guarantee the accuracy of inspection stream； According to general operational amplifier, the error of the above method can be bigger.

The size that load current is detected by the electric current of mirror image switch pipe, in Boost type switch power converter circuit In also have limitation；As shown in Fig. 6, the dash area in figure is negative current-carrying error, is limited by amplifier finite bandwidth, There will be an error at the beginning of detection.In Boost type switch power converter circuit, due to load current right and wrong Continuously, therefore it is required that the response of operational amplifier is fast and precision is high, using the load current of common operational amplifier detection Error is big.Further, in technical solution shown in Fig. 3, if after continued flow tube is substituted by diode, the electricity of current mirror framework Road would be unavailable for the detection of the load current of asynchronous rectification.

Explanation of nouns:

The meaning of Buck type switch power converter in this application is the decompression DC/ using Buck REGULATOR mode DC transformation system；Its input voltage is greater than output voltage；

The meaning of Boost type switch power converter in this application is the boosting using Boost REGULATOR mode DC/DC transformation system；Its output voltage is greater than input voltage；

The meaning of Buck-Boost type switch power converter in this application is using Buck-Boost REGULATOR The negative pressure DC/DC transformation system of mode；

PWM is the abbreviation of English Pulse Width Modulation, and Chinese meaning is pulse width modulation；Pulsewidth width Modulation system (PWM) switch power converter be in the case where control circuit output frequency is constant, by adjusting its duty ratio, from And achieve the purpose that stabilize the output voltage；

PFM is the abbreviation of English Pulse Frequency Modulation, and Chinese meaning is pulse frequency modulated；Pulse Warbled (PFM) switching mode voltage regulator circuit is " wide frequency modulation " mode, i.e., the chopping frequency of adjustment circuit is to reach steady Determine the purpose of output voltage.

CCM is the abbreviation of English Continuous Conduction Mode, and Chinese meaning is continuous conduction mode, is referred to Power tube is alternately to be continuously turned on that the electric current in inductance is made to be the operating mode of consecutive variations in Boost circuit；

DCM: being the abbreviation of English Discontinuous Conduction Mode, and Chinese meaning is discontinuous conduction mode, Refer to that power tube is alternately to close one of them in Boost circuit, making the electric current in inductance is the work of non-consecutive variations Operation mode.

Utility model content

The technical problem to be solved by the present invention is to avoid the deficiency of above-mentioned prior art, and propose one kind The load current detection method and circuit of inductive type switch power converter, greatly reduce and put to operation in load current detection The requirement of big device transient state step response, reduces the complexity of load current detection circuit, also improves load current detection Accuracy.

It is a kind of inductive type switch power converter that the utility model, which solves technical solution used by the technical problem, Load current detection circuit, including inductive current rise period or decline period midpoint detection circuit and for load current sample The sampling hold circuit of holding；The inductive current rise period or decline period midpoint detection circuit, for obtaining at A Inductive current rise period or decline period are denoted as T in switch periods_A, it is also used to obtain the inductance electricity in the B switch periods Stream rise period or decline period are denoted as T_B, B is equal to A+N；The inductive current rise period or decline period midpoint detection electricity Road is also used to obtain point moment T in first in the B switch periods_MBWith point moment in second in the C switch periods T_MC；Point moment T in described first_MBIt is risen for inductive current rise period in the B switch periods or the start time for declining the period By 0.5T_AAt the time of afterwards；Point moment T in described second_MCFor inductive current rise period or decline in the C switch periods The start time of period, which rises, passes through 0.5T_BAt the time of afterwards；Wherein C is equal to B+M；A, B, C, N and M are the nature more than or equal to 1 Number；The inductive current rise period or decline period midpoint detection circuit and sampling hold circuit electrical connection, the electricity Inducing current rise period declines period midpoint detection circuit output midpoint time-ofday signals to sampling hold circuit；When the midpoint Carving signal includes point moment T in first_MBWith second in point moment T_MCInformation；Point moment T in sampling hold circuit sampling first_MB Load current, and the load current sampled is kept into renewable time i.e. second point moment T_MC；The point moment in first T_MBTo point moment T in second_MCIn this period, if switch power converter is Buck type switch power converter, in inductance Electric current rising and falling time section all output load current sampled signals；If switch power converter is Boost type or Buck- Boost type switch power converter, then in the period output load current sampled signal of inductive current decline.

The inductive type switch power converter load current detection circuit, further includes low-pass filter；The low pass Filter and sampling hold circuit electrical connection；The load current sampled signal warp of low-pass filter is input to from sampling hold circuit It is exported after the low pass filtered.

The inductive current rise period or decline period midpoint detection circuit include that the first midpoint detection switchs, in second Point detection switch, third midpoint detection switch, the 4th midpoint detection switch, the first midpoint detection capacitor, the second midpoint detection electricity Appearance, midpoint detection operational amplifier, two an equal amount of current sources i.e. the first current source and the second current source, wherein the first electricity Stream source is used for Injection Current, and the second current source is for exporting electric current；The output terminal of first current source passes through the first midpoint detection The reversed input terminal of switch and midpoint detection operational amplifier is electrically connected, and the output terminal of the first current source also passes through in second The electrical connection of the in-phase input terminal of point detection switch and midpoint detection operational amplifier；The input terminal of second current source passes through the The reversed input terminal of three midpoint detections switch and midpoint detection operational amplifier is electrically connected, and the input terminal of the second current source is also It is electrically connected by the in-phase input terminal of the 4th midpoint detection switch and midpoint detection operational amplifier；Midpoint detection operation amplifier The electrical connection of one end of the in-phase input terminal of device and the second midpoint detection capacitor, the other end ground connection of the second midpoint detection capacitor； The electrical connection of one end of the reversed input terminal of midpoint detection operational amplifier and the first midpoint detection capacitor, the first midpoint detection electricity The other end of appearance is grounded；The capacitance of first midpoint detection capacitor and the second midpoint detection capacitor is identical；First midpoint detection switch It is switched with the 4th midpoint detection and receives the control signal control of the first midpoint detection；When the first midpoint detection control signal is high level When, the first midpoint detection switch and the 4th midpoint detection switch are all closed, and connect switch ends；When the first midpoint detection controls When signal is low level, the first midpoint detection switch and the 4th midpoint detection switch are all opened, and disconnect switch ends；The Two midpoint detections switch and third midpoint detection switch receive the control signal control of the second midpoint detection；When the second midpoint detection control When signal processed is high level, the second midpoint detection switch and third midpoint detection switch are all closed, and connect switch ends；When When two midpoint detections control signal is low level, the second midpoint detection switch and third midpoint detection switch are all opened, and make to switch Both ends disconnect；First midpoint detection controls signal or upper second midpoint detection control signal turns equal to inductive type Switching Power Supply The switching signal of parallel operation；When switching signal is in the odd number period, the first midpoint detection control signal high level with The high level of switching signal is identical；When switching signal is in the even number period, the second midpoint detection controls the height of signal Level is identical as the high level of switching signal；The output terminal of midpoint detection operational amplifier exports the first midpoint time-ofday signals, The first midpoint time-ofday signals are sent to the sampling hold circuit, control the sampling instant of sample circuit.

The inductive current rise period or decline period midpoint detection circuit further include d type flip flop and XOR gate；The D The switching signal for the control of inductive type switch power converter that the clock signal of trigger is an externally input；The D triggering The electrical connection of second output terminal of the first input end of device and the d type flip flop, the first lead-out terminal of the d type flip flop are defeated Out signal to XOR gate an input terminal；The output terminal of midpoint detection operational amplifier exports the first midpoint time-ofday signals To another input terminal of XOR gate, the output terminal of XOR gate exports the second midpoint time-ofday signals, the point moment in second Signal is sent to the sampling hold circuit, controls the sampling instant of sample circuit.

The first lead-out terminal of the d type flip flop outputs signal to first and door, with inductive type switch power converter control The switching signal of system carries out and operation, and the first midpoint detection of output controls signal；Second output terminal of the d type flip flop exports Signal carries out with the switching signal of inductive type switch power converter control to second and door and operation, the second midpoint of output is examined Observing and controlling signal.

The sampling hold circuit keeps opening including the second sample-hold switch, the second sampling holding capacitor, third sampling It closes, third sampling holding capacitor and sampling keep operational amplifier；One end of second sample-hold switch is used for and external electricity The connection of electrification current detection circuit obtains load current sampled signal, and the other end of the second sample-hold switch is sampled with second simultaneously One end of holding capacitor and one end electrical connection of third sample-hold switch, the other end ground connection of the second sampling holding capacitor； The other end of third sample-hold switch is simultaneously and sampling keeps the in-phase input terminal of operational amplifier and third sampling to keep One end of capacitor is electrically connected, and third samples the other end ground connection of holding capacitor；Sampling keeps the inverting input terminal of operational amplifier Son and sampling keep the output terminal electrical connection of operational amplifier；Second sample-hold switch is controlled by the second midpoint time-ofday signals Non-signal, when the non-signal of the second midpoint time-ofday signals be high level when, the second sample-hold switch closure make switch ends It connects, when the non-signal of the second midpoint time-ofday signals is low level, the second sample-hold switch opening disconnects switch ends Connection；Third sample-hold switch is controlled by the second midpoint time-ofday signals, when the second midpoint time-ofday signals are high level, third Sample-hold switch closure connects switch ends, when the second midpoint time-ofday signals are low level, third sample-hold switch Opening disconnects switch ends.

The inductive type switch power converter load current detection circuit further includes inductive current zero-crossing examination electricity Road, for obtaining low-pass filtering switch control signal.

It is switched and is electrically connected by low-pass filtering between the low-pass filter and sampling hold circuit；The low-pass filtering is opened Close the low-pass filtering switch control signal for being controlled by and exporting from inductive current zero-crossing detection circuit；When inductive current is zero, Low-pass filtering switch control signal controls the low-pass filtering switch and opens, and disconnects switch ends, so that described It is disconnected between low-pass filter and sampling hold circuit, and the input grounding of low-pass filter；It is in inductive current When non-zero, low-pass filtering switch control signal, which controls the low-pass filtering and closes the switch, connects switch ends, to make described It is electrically connected between low-pass filter and sampling hold circuit.

The inductive type switch power converter load current detection circuit further includes low-pass filtering input drop-down MOS Pipe, after disconnecting between low-pass filter and sampling hold circuit, drags down the input of the low-pass filter, thus So that the low-pass filter input is zero.

The low-pass filter includes one or more levels low-pass filter.

When the low-pass filter is level-one RC low-pass filter, level-one RC low-pass filter includes low-pass filtering resistance With low-pass filtering capacitor；One end electrical connection of one end of the low-pass filtering resistance and low-pass filtering switch, meanwhile, this is described low The source electrode electrical connection of one end of pass filter resistance and low-pass filtering input drop-down metal-oxide-semiconductor, the grid of low-pass filtering input drop-down metal-oxide-semiconductor The non-signal of low-pass filtering switch control signal, the grounded drain of low-pass filtering input drop-down metal-oxide-semiconductor are accessed in pole；The low pass filtered The other end of wave resistance is used as the output terminal of low-pass filter, while the other end of the low-pass filtering resistance is also and low pass One end of filter capacitor is electrically connected, the other end ground connection of low-pass filtering capacitor.

The inductive type switch power converter load current detection circuit further includes obtaining load current for sampling Inductive current detection circuit；The inductive current detection circuit and sampling hold circuit electrical connection；Inductive current detection Circuit is to sampling hold circuit output load current signal.

The utility model, which solves technical solution used by the technical problem, can also be a kind of inductive type Switching Power Supply Converter circuit includes switch power converter load current detection circuit described in above-mentioned any one.

The inductive type switch power converter circuit further includes logic control circuit；The logic control circuit is for producing The basic switching signal of raw inductive type switch power converter timing control；The logic control circuit is according to basic switching signal Generate the first control signal GP and second control signal GN for controlling two power switch tubes；First control signal GP is height When level, one of power tube is opened；When first control signal GP is low level, another power tube is opened；First control Signal GP processed is the synchronous transformation signal of basic switching signal with second control signal GN；Inductive current rise time section and inductance Downslope time section is to be synchronized with first control signal GP and second control signal GN；To inductive current rise time section It is also synchronous with inductive current fall time section with basic switching signal.

Compared with the existing technology compared with, the beneficial effects of the utility model are: 1, by cleverly timing control, according to having died It removes the inductive current rise period of switch periods or declines the time of period, when obtaining the rising of current switch period inductance to simulate Section or decline the period midpoint, and dexterously the moment carry out sampling keep, take full advantage of inductive current rise or Decline cycle is the feature of linear change, while when load current is constant, and the midpoint that inductive current rises is equal to inductance The midpoint of electric current decline, therefore load detecting circuit can be greatly simplified；2, simultaneously because the sampling instant is nearly or approximately The midpoint of period or continued flow tube conducting period is connected in switching tube, and sample rate current size is usually the best response area to work in amplifier Between in range, therefore the accuracy of whole load current detection is also improved, and not only avoids complicated circuit design, The detection accuracy for improving load current reduces the complexity and design difficulty of circuit；3, circuit structure is simply ingenious, is applicable in Property can use by force the various DC/DC switch power converters of Buck, Boost and Buck-Boost；Either switching tube or afterflow Pipe, can restore the size of load current, strong flexibility with this method；It is also applied for synchronous and asynchronous rectification circuit, It is common to the detection of power tube proportional current, series resistance current detection circuit；In Application of integrated circuit, it is easy to application deployment, Save chip area.

Detailed description of the invention

Fig. 1 is the schematic block diagram of the utility model load current detection circuit preferred embodiment；

Fig. 2 is that principle of the prior art load current detection circuit in the application of DC/DC switch power converter circuit is shown One of meaning block diagram；

Fig. 3 is that principle of the prior art load current detection circuit in the application of DC/DC switch power converter circuit is shown The two of meaning block diagram；

Fig. 4 is the correspondence timing of circuit the work inductive current and load current detection under Buck type CCM mode in Fig. 3 With error note schematic diagram；

Fig. 5 is the correspondence timing of circuit the work inductive current and load current detection under Buck type DCM mode in Fig. 3 With error note schematic diagram；

Fig. 6 be circuit in Fig. 3 work under Boost type CCM mode inductive current and load current detection to it is corresponding when Sequence and error note schematic diagram；

Fig. 7 is the inductive current signature analysis figure of inductive type switch power converter；

Fig. 8 is the inductive current time diagram of inductive type switch power converter；

Fig. 9 is that the utility model load current detection circuit is preferred in the application of DC/DC switch power converter circuit The schematic block diagram of embodiment；

Figure 10 is the circuit theory schematic diagram that inductive current rises or falls midpoint detection circuit preferred embodiment in Fig. 1；

Figure 11 is each signal sequence relational graph in Figure 10 in Buck type switch power converter application example；

Figure 12 is the circuit theory schematic block diagram of the utility model load current detection circuit preferred embodiment；It is shown in figure Sampling hold circuit 34 and low-pass filter 35；

Figure 13 is the electrical block diagram of the preferred embodiment of low-pass filter 35；

Figure 14 is the relationship of the transient response curve of operational amplifier sampled current signals and load current in the prior art Schematic diagram；

It is Buck type switch power converter that Figure 15 and 16, which is the utility model in switch power converter, and Buck type is opened The signal sequence relational graph of powered-down source converter work in ccm mode；In Figure 15, the current sample moment is located on inductive current Rise the period；In Figure 16, the current sample moment is located at the inductive current decline period；

It is Buck type switch power converter that Figure 17 and 18, which is the utility model in switch power converter, and Buck type is opened The signal sequence relational graph of powered-down source converter work in dcm mode；In Figure 17, the current sample moment is located on inductive current Rise the period；In Figure 18, the current sample moment is located at the inductive current decline period；

It is Boost type or Buck-Boost type Switching Power Supply that Figure 19 and 20, which is the utility model in switch power converter, Converter, and the signal sequence relational graph of switch power converter work in ccm mode；In Figure 18, the current sample moment Decline the period positioned at inductive current；In Figure 19, the current sample moment is located at inductive current rise period；

It is Boost type or Buck-Boost type Switching Power Supply that Figure 21 and 22, which is the utility model in switch power converter, Converter, and the signal sequence relational graph of switch power converter work in dcm mode；In Figure 21, the current sample moment Decline the period positioned at inductive current；In Figure 22, the current sample moment is located at inductive current rise period.

Specific embodiment

The embodiments of the present invention is further described below in conjunction with each attached drawing.

Inductive type switch power converter, basic principle are all to realize voltage change using the energy storage characteristic of inductance, The change rate of inductive current is equal to voltage across the inductor divided by inductance Henry value, is expressed as using equationInductive current Variation is linear process, the voltage and electricity of the variation speed, that is, inductive current linear change slope and inductance both ends of inductive current Feel one timing of applied voltage that inductance value is related, at inductance both ends, when inductance inductance value also determines, the raising and lowering of inductive current Slope is also fixed.

The foundation characteristic of signified switch power converter includes: the switch electricity under CCM operating mode in the utility model Source converter controls two power switch tube alternate conductions by logic control circuit, one switch periods includes inductance electricity Flow rise time section and inductive current fall time section；In dcm operating modes, switch power converter passes through logic control electricity Road controls two power switch tube alternate conductions and is spaced closing, that is, in a switch periods, including on inductive current Rise the period that period, inductive current fall time section and inductive current are zero.

Logic control circuit in switch power converter not only generates the basic switching signal of switch power converter, such as Pwm switching signal also generates first control signal GP, second control signal GN for controlling two power switch tubes；First When control signal GP is high level, one of power tube is opened；When second control signal GN is low level, another power Pipe is opened；The first control signal GP of control switch pipe and the second control signal GN of control continued flow tube are by pwm switching signal Based on generate, therefore first control signal GP, second control signal GN are the transformation signal of pwm signal, are between each signal Synchronous.Inductive current rise time section and inductive current fall time section are to be synchronized with the control of first control signal GP and second Signal GN's processed；And first control signal GP, second control signal GN are synchronous with pwm switching signal, therefore can be adopted Inductive current rise time section and inductive current fall time section are obtained with the low and high level period of pwm switching signal.

As shown in fig. 7, the inductive current of inductive type switch power converter is a triangular wave, it can be seen that inductance Electric current from T0 to T1, climb upwards by the moment, and the 0.5T1 moment is the middle point moment that inductive current climbs；The moment inductance electricity from T1 to T3 The lower decline of flow direction, T2 is the middle point moment of its decline.When load current is constant, in each switch periods, inductance electricity The starting point that stream rises is equal to the terminal of decline, if, if it is not, the terminal declined every time all compares the high starting point of rising, Inductive current will become larger always, otherwise just become smaller always.Therefore, at T0 moment and T3 moment, inductive current size is one Sample.If the midpoint of inductance rising edge is connected with the midpoint of decline, this line segment is parallel to X-axis, i.e., inductive current is upper The midpoint that midpoint is equal to inductive current decline is risen, so the midpoint of sampling inductive current rise period and sampling inductive current decline The midpoint of period is equivalence changes.

As shown in fig. 7, if the starting point size of current of inductive current rise period is equal to the terminal electricity of inductance decline period Size is flowed, and there is a peak point current, then is presented in Fig. 7, the area of the first triangle 1 is equal to the face of the second triangle 2 Product, the area of third triangle 3 are equal to the area of the 4th triangle 4.Any type of inductive type for having used inductance is opened For powered-down source converter, in this section be the feature of linear change according to inductive current, if find the 0.5T1 moment or The size of T2 moment inductive current, and sampling holding is carried out to the electric current of sampling instant, so that it may by simple calculations, change It is counted as the size of load current.If obtained under middle point moment 0.5T1 moment or the inductive current of inductive current rising edge Point moment T2 in drop, the i.e. inductive current of the middle point moment of inductive current triangular wave, so that it may which this, which is calculated, obtains entire switch week The load current of phase, therefore above-mentioned two moment, this was the key point of sample rate current.Obtain the inductance electricity of current switch period The rise period of stream or the midpoint for declining the period often require the real-time characteristic of circuit very high；In the present invention, it first obtains Take inductive current rise period in the switch periods passed or decline the total time T of period, further according to since the period to The middle point moment of current period is substituted at the time of 0.5T, and the tactful load for obtaining the full switch period is kept by sampling accordingly Electric current.

As shown in fig. 7, the midpoint electric current of sampling is I for Buck type switch power converter circuit_h, due to Inductive current all externally exports energy during raising and lowering, so,As shown in fig. 7, For Boost or One Buck-Boost converter body, only during inductive current decline, just externally output electric discharge, therefore

As shown in figure 8, being Ta, the second week in the rising total time of a cycle inductive current when n is 1 The total time that phase inductive current rises is Tb, and the total time that third period inductive current rises is Tc.In second period Midpoint: T_MB=T1+0.5Ta, and the midpoint in third period: T_MC=T2+0.5Tb.Similarly, can also with same method come The midpoint of acquisition decline period.When load current is constant, the peak value and valley of inductive current are also constant, therefore inductance electricity The rise period midpoint of stream with decline period midpoint be as, can be according to practical application come flexible choice.

It is that the utility model realizes that the load current detection circuit of load current detection method is opened in DC/DC as shown in Figure 9 Close the schematic block diagram in converter circuitry of power application.

In Fig. 9, if circuit terminal V1 is external power input of switch power converter, circuit terminal V2 connects electricity When holding the output terminal as switch power converter, which is Buck type switch power converter, Transistor Q1 in figure is that PMOS tube is used as switching tube, and the transistor Q2 in figure is that NMOS tube is used as continued flow tube.

In Fig. 9, if circuit terminal V2 is external power input of switch power converter, circuit terminal V1 is used as The output terminal of switch power converter, then the switch power converter is Boost type switch power converter, the crystalline substance in figure Body pipe Q2 is that NMOS tube is used as switching tube, and the transistor Q1 in figure is that PMOS tube is used as continued flow tube.

The electric current midpoint sample holding circuit of 41 meaning of label in Fig. 9 i.e. the Switching Power Supply of the utility model meaning Converter load current detection circuit.

In Fig. 9, inductive current is input to electric current midpoint sample holding circuit 41, and electric current midpoint sample holding circuit 41 is defeated Load current signal, that is, IFB signal out, 40 output voltage feedback signals of output voltage sampling circuit, that is, VFB signal, load current Signal, that is, IFB signal and output voltage feedback signal, that is, VFB signal and reference voltage VBG signal are sent to interior together Portion's CC/CV error amplifier 42, CC/CV error amplifier 42 outputs signal to PWM comparator 44；CC/CV error amplifier 42 Output signal and slope compensation circuit 43 output signal be input to jointly control PWM comparator 44, PWM comparator 44 export Pwm control signal is to Logic control module 45, by the output of control PWM comparator 44 to control logic control module 45 Output, so that the pwm signal in each period is controlled by the load current signal fed back, to control power output stage to control most Big output load current, to play the purpose of constant maximum output current.Fig. 9 has been merely given as the Switching Power Supply of PWM mode Converter embodiment, in fact, technical solutions of the utility model are also equally applicable to the switch power converter electricity of PFM mode Road.

As shown in Figure 1, be the circuit block diagram of one of the preferred embodiment in the utility model, including inductive current rise period or Decline period midpoint detection circuit 32, inductive current detection circuit 30, inductive current zero cross detection circuit 31, sampling hold circuit 34 and low-pass filter 35.

Inductive current rise period as shown in Figure 1 or decline period midpoint detection circuit 32 obtain Switching Power Supply conversion Inductive current rise period or decline period of the device in the A switch periods are denoted as T total time_A, in the B switch periods Inductive current rise period or the decline period total time be denoted as T_B.The B inductive current rise period declines the period Start time, which rises, passes through 0.5T_APoint moment T in i.e. first at the time of afterwards_MBLoad current is sampled, is kept by sampling hold circuit The load current sampled value is to point moment T in second_MC；Point moment T in second_MCFor the C switch periods, inductive current rises Period or the starting point for declining the period pass through 0.5T_BAt the time of afterwards；The point moment T in first_MBTo point moment T in second_MCPeriod, Sampling keeps point moment T in first_MBSampled current value.Wherein A, B and C are the natural number more than or equal to 1, B=A+1, C =B+1；

The application to the utility model in Buck type switch power converter is described in detail below.Assuming that Buck type Switch power converter work is equal to the mean value of inductive current in CCM mode, that is, continuous operation mode, output load current.Do not having In the presence of having load current sampling resistor, it is difficult directly to sample the electric current on inductance, but inductive current is divided into two Point, when a portion is that switching tube is opened, the electric current that switching tube flows through is equal to the electric current of inductance, then flows through the electricity of continued flow tube Stream is 0, and when another part of inductive current is that continued flow tube is opened, the electric current that continued flow tube flows through is equal to the electric current of inductance, is flowed through out The electric current for closing pipe is 0, therefore load current is the mean value for flowing through the sum of switching tube and afterflow tube current.It is constant in load current When, the electric current that each switch periods flow through switching tube is the electric current linearly increased；Accordingly in the present invention, first The time T that a cycle switching tube is opened in acquisition, when current period switching tube opening time continue for T/2, sampling Inductive current, that is, load current, and the load current sampled value at this moment is remained into next cycle switching tube turn-on time At the time of reaching a cycle switch pipe turn-on time half.Assuming that the work of Buck type switch power converter is in DCM mode Discontinuous operating mode, it is only necessary at the time of sampled value remained to continued flow tube closing, switching tube and continued flow tube not At the time of conducting, no electric current flows out to load, only maintains output voltage by output capacitance；It is not led in switching tube and continued flow tube The sampling retention value of sampling hold circuit does not export externally at the time of logical.

For Boost type or Buck-Boost type switch power converter, same method can also be used to sample afterflow The load current at period midpoint is connected in pipe, and carries out sampling holding to the load current sampled value；In the continuous of current switch period In the period that flow tube is opened, the load current sampled value that a cycle sampling is kept in output, until current switch period is continuous As soon as the half moment of starting point supreme conducting period in period is connected in flow tube, refresh the load current sampled value of current period. Finally, being exported after the load current signal that sampling is kept is passed through low-pass filter, as switch power converter in the period Interior load current.The utility model does not need the accurate sampling that the complete period is carried out to entire switch periods inductive current, only needs Will be in this switch periods, sampling is negative at the time of period half was connected to a upper period since the start time of this switch periods Electric current is carried, and load current sampled value sampling is kept to next renewable time, can accurately obtain the load in complete period Electric current.Requirement in this way to load current detection circuit, sample circuit all substantially reduces, and reduces circuit complexity and improves simultaneously The precision of load detecting.Especially within the complete period of switching tube and continued flow tube alternate conduction, the electric current of switching tube and continued flow tube Variation usually require experience one linearly increase to peak point current from zero or from base current during, accurately to obtain switch The size of current of pipe and continued flow tube, it is very high to the operational amplifier requirement in current detection circuit, need operational amplifier to have The responding ability of full frequency band is otherwise inevitable in the current sample error in complete period.

In PWM switch power converter circuit, the rise period of inductive current or decline period have been corresponded to by switching tube The conducting period and close the period；And the pulsewidth of pwm switching signal is equal to the turn-on time of switching tube or continued flow tube, control switch First control signal GP, the second control signal GN of pipe and continued flow tube based on pwm switching signal by generating, therefore the first control Signal GP processed, second control signal GN are the transformation signal of pwm signal, are synchronous between each signal.Furthermore in switching tube or Continued flow tube is from opening to closing, and inductive current is linear rise in this period, so during inductive current rises or falls Point is exactly the position of the half of PWM, GP or GN switching signal pulsewidth.Therefore in the pulsewidth for only needing to detect pwm switching signal Point moment, so that it may find the middle point moment of inductive current.After sampling hold circuit obtains the information of point moment among the above, just The electric current of point moment in this can be sampled, and samples holding output, until next pwm switching signal cycle switch pipe is connected The middle point moment of time.

In the present invention, using in a upper pwm switching signal period switching tube be connected period half at the time of come At the time of substituting switching tube conducting period half in the current pwm switching signal period, in pwm switching signal cycle stability, energy The control of sampling instant is completed using very ingenious and simple circuit.Even if during pwm switching signal mechanical periodicity, by In the conducting period information closed in the period using two, therefore PWM only falls behind inductive current and changes one or several open The period is closed, accomplishes real-time detection substantially, load current will could also obtain after subsequent low-pass filter is average, to inductance The precision of current detecting does not influence.

As shown in Figure 10, the inductive current rise period of the utility model or decline one of period midpoint detection circuit 32 In specific embodiment, including two an equal amount of first current source I1 and the second current source I2, there are one midpoint detections to transport Amplifier OP1 is calculated, four midpoint detection switches are the first midpoint detection switch, the second midpoint detection switch, third midpoint detection Switch and the 4th midpoint detection switch and the identical first midpoint detection capacitor CA of two capacitances and the second midpoint detection capacitor CB.Figure 11 is each signal sequence relational graph in Figure 10.

As shown in FIG. 10 and 11, wherein the first midpoint detection control signal Phi 1 and the second midpoint detection control signal Phi 1B It is the signal generated after being converted by the pwm switching signal of switch power converter；As shown in Figure 10, the first midpoint detection control letter Number Φ 1 and the second midpoint detection control signal Phi 1B is first control signal GP or second control signal GN respectively behind cloud The signal of acquisition.When pwm switching signal is in the odd number period, the first midpoint detection controls the high level of signal Phi 1 It is identical as the high level of pwm switching signal；When pwm switching signal is in the even number period, the control of the second midpoint detection The high level of signal Phi 1B and the high level of pwm switching signal are identical.First midpoint detection controls signal Phi 1 and the second midpoint Relationship between detection control signal Phi 1B is: the first midpoint detection controls signal Phi 1 or upper second midpoint detection control signal Φ 1B is equal to pwm switching signal.

As shown in FIG. 10 and 11, the first current source I1 and the second current source I2 is an equal amount of current source, wherein first Current source I1 is used for Injection Current, and the second current source I2 is for exporting electric current；Assuming that in the first midpoint detection capacitor CA and second The capacitance of point detection capacitor CB is equal, and the initial value above earth potential on ungrounded terminal is all 0, i.e. midpoint detection operation amplifier Voltage VC1=VC2=0 on positive input and negative input of device OP1, in first pwm switching signal Pulse width period, it is high level Φ 1=1 that the first midpoint detection, which controls signal Phi 1, and it is low electricity that the second midpoint detection, which controls signal Phi 1B, Flat i.e. Φ 1B=0, the first midpoint detection capacitor CA are started to charge to VC1=Vch, and the second midpoint detection capacitor CB discharges into VC2 =0；Controlling signal Phi 1 and the second midpoint detection control signal Phi 1B in the first midpoint detection is all low level i.e. Φ 1=Φ 1B When=0, the voltage VC2 on the voltage VC1 and the second midpoint detection capacitor CB on the first midpoint detection capacitor CA is kept；Second In the pulse width period of a period pwm switching signal, it is high level that the first midpoint detection, which controls signal Phi 1,Second midpoint Detection control signal Phi 1B is low levelVoltage VC1 on first midpoint detection capacitor CA discharges since Vch, Voltage VC2 on second midpoint detection capacitor CB is started to charge from 0.Due to CA=CB and I1=I2, so when VC1=VC2's At the moment, the level overturning of the MID signal of midpoint detection operational amplifier output, which is exactly one on pwm switching signal The PWM pulsewidth midpoint in period.

It as shown in figure 12, is the circuit theory signal of one of the utility model load current detection circuit preferred embodiment Scheme, inductive current rise period or decline period midpoint detection circuit 32, inductive current detection circuit 30, inductance are shown in figure Current over-zero detection circuit 31, sampling hold circuit 34 and low-pass filter 35.

As shown in figure 12, the sampling hold circuit 34 include the second sample-hold switch, second sampling holding capacitor C2, Third sample-hold switch, third sampling holding capacitor C3, sampling keep operational amplifier；One end of second sample-hold switch For obtaining load current sampled signal with the external connection of inductive current detection circuit 30, the second sample-hold switch it is another End is simultaneously and one end electrical connection of one end of the second sampling holding capacitor and third sample-hold switch, the second sampling keep electricity The other end of appearance is grounded；The other end of third sample-hold switch keeps the in-phase input terminal of operational amplifier with sampling simultaneously And one end electrical connection of third sampling holding capacitor, third sample the other end ground connection of holding capacitor；Sampling keeps operation to put The reversed input terminal of big device and sampling keep the output terminal electrical connection of operational amplifier；Second sample-hold switch is controlled by The non-signal of second midpoint time-ofday signalsWhen the non-signal of the second midpoint time-ofday signalsWhen for high level, Two sample-hold switch closure connects switch ends, and when the non-signal of the second midpoint time-ofday signals is low level, second is adopted Sample, which keeps switch to open, disconnects switch ends；Third sample-hold switch is controlled by the second midpoint time-ofday signals D50C, When the second midpoint time-ofday signals D50C is high level, third sample-hold switch closure connects switch ends, in second When point moment signal D50C is low level, third sample-hold switch opening disconnects switch ends.

As shown in figure 12, it is electrically connected between the low-pass filter 35 and sampling hold circuit 34 by low-pass filtering switch It connects；The low-pass filtering switch is controlled by the low-pass filtering switch control signal exported from inductive current zero-crossing detection circuit 31 The non-signal of ZCSwitch power converter load current detection circuit further includes inductive current zero-crossing detection circuit at this time 31, for obtaining low-pass filtering switch control signal ZC and its non-signalFor the logic non-signal of ZC.

For Buck type switching power circuit, low-pass filtering switch control signal ZC is low when inductive current is zero Pass filter switch control signal controls the low-pass filtering switch and opens, and disconnects switch ends, so that described low It is disconnected between bandpass filter 35 and sampling hold circuit 34；When inductive current is non-zero, low-pass filtering switch control letter Number control low-pass filtering, which closes the switch, connects switch ends, so that the low-pass filter 35 and sampling keep electricity It is electrically connected between road 34.

For Boost or Buck-Boost type switching power circuit, ZC is in inductance for low-pass filtering switch control signal It is height when electric current is zero or switching tube is connected, low-pass filtering switch control signal ZC controls the low-pass filtering switch and beats It opens, so that being disconnected between the low-pass filter 35 and sampling hold circuit 34, and low-pass filter input is drawn to ground； When inductive current is non-zero and when continued flow tube is connected, low-pass filtering switch control signal controls the low-pass filtering switch and closes It closes, so that being electrically connected between the low-pass filter 35 and sampling hold circuit 34.

As shown in figure 12, the low-pass filter 35 includes low-pass filtering resistance and low-pass filtering capacitor；Sampling keeps electricity Road 34 further includes the low-pass filtering input drop-down metal-oxide-semiconductor for controlling low-pass filter input when inductive current is zero；It is described One end of low-pass filtering resistance and low-pass filtering switch one end electrical connection, meanwhile, one end of the low-pass filtering resistance and The source electrode electrical connection of low-pass filtering input drop-down metal-oxide-semiconductor, the grid access low-pass filtering switch of low-pass filtering input drop-down metal-oxide-semiconductor Control signal ZC, the grounded drain of low-pass filtering input drop-down metal-oxide-semiconductor；The other end of the low-pass filtering resistance is used as low pass filtered The output terminal of wave device 35, while the other end of the low-pass filtering resistance is also electrically connected with one end of low-pass filtering capacitor, The other end of low-pass filtering capacitor is grounded.

As shown in figure 13, in the embodiment of another low-pass filter, there is the RC of same circuit parameter including two-stage Low-pass filter, resistance and capacitor in each dual stage filter are respectively 1M Ω and 4pF, are suitable for switching signal The case where 500MHz.The parameter of low-pass filter can make a choice according to the actual situation, such as according to different maximum load currents, The suitable low-pass filtering parameter of the selections such as the loop gain of current sample ratio, switching signal and related circuit.

In conjunction with sampling hold circuit 34 as shown in figure 12, it is assumed that switch power converter turns for Buck type Switching Power Supply Parallel operation and Buck type switch power converter work in CCM mode, after sampling hold circuit 34 detects inductor current signal, The second midpoint time-ofday signals D50C is obtained by midpoint detection circuit, in the first half cycle of pwm switching signal, the second sampling is kept Capacitor C2 samples inductive current size, when reaching at the time of midpoint detection circuit provides, that is, the second midpoint time-ofday signals After the first sampling instant that D50C is provided reaches, the second sampling holding capacitor C2 and third sampling holding capacitor C3 pass through switch Short circuit, wherein C2 > > C3, the upper voltage and second of such third sampling holding capacitor C3 sample holding capacitor C2 in sampling instant Voltage be consistent.The sampling instant in next pwm switching signal period is remained to by sampling holding operational amplifier, the Electrical connection between three sampling holding capacitor C3 and the second sampling holding capacitor C2 disconnects, and the second sampling holding capacitor C2 goes to sample The inductive current size in a new pwm switching signal period.

In conjunction with sampling hold circuit 34 as shown in figure 12, it is assumed that switch power converter turns for Buck type Switching Power Supply Parallel operation and Buck type switch power converter work in DCM mode, other working sequences and Buck type switch power converter It works identical in CCM mode, different is exactly needs when inductive current becomes zero, that is, low-pass filtering switch control The ZC=1 when signal of signal is high level, control low-pass filtering switch is opened, so that sampling hold circuit 34 and low-pass filtering Electrical connection between device 35 disconnects, and inputs drop-down MOS pipe by low-pass filtering and draw the input of low-pass filter to ground, this The size for the electric current energy exact representation switch power converter load current that sample low-pass filter 35 exports.

In conjunction with sampling hold circuit 34 as shown in figure 12, it is assumed that switch power converter is Boost type or Buck- Boost type switch power converter and the switch power converter work in CCM mode, other working sequences and Buck type Switch power converter work is identical in CCM mode, and difference is only to carry out adopting for load current during continued flow tube conducting Sample is kept, and within the period of switching tube conducting, the signal high level of low-pass filtering switch control signal, i.e. ZC=1 can be made, To disconnect the connection of sampling hold circuit and low-pass filter 35, the electric current that sampling is kept in this way is only the electricity of continued flow tube Stream, averaged out by low-pass filter be exactly Boost type or Buck-Boost type switch power converter in ccm mode The size of load current.

In conjunction with sampling hold circuit 34 as shown in figure 12, it is assumed that switch power converter is Boost type or Buck- Boost type switch power converter and switch power converter work is in DCM mode, other working sequence Boost types or The work of Buck-Boost type switch power converter is identical in ccm mode, and difference is also when inductance becomes zero Make the signal high level i.e. ZC=1 of low-pass filtering switch control signal, control low-pass filtering switch is opened, disconnects sampling and keep Circuit and low-pass filter 35 connect, and the output of low-pass filter 35 is drawn to ground, and do not have to open the moment until switching tube The signal of low-pass filtering switch control signal is just set as high level, what such low-pass filter 35 exported be exactly Boost type or The size of Buck-Boost type switch power converter real load electric current in dcm mode.

As Figure 14 in the prior art operational amplifier response curve and with the relation schematic diagram of load current；Dotted line table in figure The actual transient response curve for showing operational amplifier, during the load current that zero crossings rise, the operation of the prior art Amplifier needs trace detection to export the inductive current size in entire rise time section, when the finite gain and response of amplifier Between, certain response time is needed, initial stage inductive current detection error is larger, also can therefore influence negative in whole cycle Carry the accuracy of current detecting；Since the utility model is only needed in midpoint sample, from inductive current from low spot climb to There has been enough time at midpoint to establish operational amplifier response in this period, initial stage amplifier response error does not influence to adopt The precision of sample electric current.Therefore, the design difficulty of operational amplifier and requirement are greatly lowered.

Figure 15 is that the utility model works for Buck type switch power converter in CCM mode in switch power converter Under, and signal sequence relationship of the Buck type switch power converter when inductive current rise period carries out load current sampling Figure；In figure as it can be seen that after first inductive current rise period T1 starts, upper a cycle midpoint current sampling data is first exported The input signal Vsen2 of Vsen1, low-pass filter are equal to Vsen1, reach upper inductive current rise period T0's when the time When half, inductive current sampling value Vsen1 is updated, while this signal is output to low-pass filter, low-pass filter is defeated Enter voltage Vsen2 equal to Vsen1, until next inductive current rise period T2 reaches the 0.5T1 moment.It is reached when the T2 period At the time of 0.5T1, sample rate current again, and the midpoint current sampling data Vsen1 updated, remaining to the T3 period reaches 0.5T2's Moment；In cycles, it is not repeating.Because when switching tube and continued flow tube are connected, switch power converter is all defeated to loading Electric current out, so load current I_loadIt should be the sum of switching tube and afterflow tube current.Current feedback signal IFB is that sampling is protected in figure The load current value held exports the load current signal of characterization load current size after low-pass filter filters.

Figure 16 is that the utility model works for Buck type switch power converter in CCM mode in switch power converter Under, and signal sequence relationship of the Buck type switch power converter when the inductive current decline period carrying out load current sampling Figure.Different with Figure 15, sampling hold circuit declines the midpoint sample of period in inductive current and updates current sample Value Vsen1, until the midpoint of next inductive current decline period samples again and updates current sampling data.

Figure 17 is that the utility model works for Buck type switch power converter in DCM mode in switch power converter Under, and signal sequence relationship of the Buck type switch power converter when inductive current rise period carries out load current sampling Figure；After first inductive current rise period T1 starts, first output keeps the midpoint sample signal Vsen1 of upper a cycle, The input Vsen2 of low-pass filter is equal to Vsen1, adopts when the time reaching the half of upper inductive current rise period T0 Sample updates midpoint current sampling data Vsen1, when having served as zero detection circuit of inductive current and detect that inductive current drops to zero, makes Obtain low-pass filter input signal Vsen2=0.When next inductive current rise period T2 arrives, the T1 period is first exported Midpoint sample current sampling data Vsen1, at the time of reaching 0.5T1, sampling updates midpoint current sampling data Vsen1 again, and protects Continued flow tube closing is held, then the input signal Vsen2 of low-pass filter is drawn to ground.In cycles, it is not repeating.In list In a switch periods, output load current size I_load, should be the square in a switch periods in Figure 17 with identical hacures Shape area, that is, load current integrated value divided by integration time time.In dcm mode, inductive current can drop to zero, electricity Inducing current be it is discrete, therefore inductive current sampling be also it is discrete, load current is that this discontinuous current is averaged Value, therefore load current I in this mode_loadSize can be less than midpoint sample size of current.

Figure 18 is that the utility model works for Buck type switch power converter in DCM mode in switch power converter Under, and Buck type switch power converter carries out the signal sequence relational graph of load current sampling in the inductive current decline period. Different with Figure 17, sampling hold circuit declines the midpoint sample of period in inductive current and updates sample rate current.

Figure 19 is that the utility model is converted in switch power converter for Boost type or Buck-Boost type Switching Power Supply Device works in ccm mode, and the switch power converter is in the signal of the decline period sampling load current of inductive current Order relation figure；After first inductive current decline period T1 starts, upper a cycle midpoint current sampling data is first exported Vsen1, the input signal Vsen2=Vsen1 of low-pass filter, reaching the 0.5T0 moment just updates inductive current sampling value Vsen1, while this electric current being kept to be output to low-pass filter, low-pass filter input signal Vsen2=Vsen1, until this The inductive current decline period terminates.After second inductive current decline period T2 arrives, first export under an inductive current The sampled current value for dropping the period T1+0.5T0 moment samples more again at the time of the inductive current decline period reaching 0.5T1 New current sampling data Vsen1, and remain to the inductive current decline period and terminate.In cycles, it is not repeating.Because of Boost The switch power converter circuit of type only just exports electric current toward output capacitance when continued flow tube is connected, so load current Equal to the size that continued flow tube flows through electric current.Therefore, output sample rate current only exports when continued flow tube is connected, I_loadIt is big It is small be the rectangular area i.e. integrated value of load current in a switch periods with identical hacures divided by integration time when Between.

Figure 20 is that the utility model is converted in switch power converter for Boost type or Buck-Boost type Switching Power Supply Device works in ccm mode, and in the signal sequence relational graph of inductive current rise period sampling load current.In this period electricity After inducing current rise period T1 starts, the input Vsen2 of low-pass filter is pulled down to 0, and sampled current value Vsen1 is proportional to inductance Size of current；Sampled current value Vsen1 holding Vsen1 is just obtained when reaching the estimated midpoint 0.5T0 moment, at this moment low pass filtered The input signal Vsen2 of wave device is still equal to 0；From at the time of inductive current is begun to decline, switch makes low pass after opening Filter input signal Vsen2=Vsen1, until the switch periods terminate, this Vsen1 is inductive current rise period T1 In the inductive current sampling value of the 0.5T0 instance sample of the period.As the inductive current rise period T2 of next switch periods After arrival, the entire period that inductive current rises, the input signal Vsen2 of low-pass filter is pulled low, when arrival inductance The electric current rise period 0.5T1 moment samples inductive current and updates current sampling data Vsen1 and keep, but not to low-pass filtering Device output；When inductive current is begun to decline, just make the input signal Vsen2=Vsen1 of low-pass filter, until this is opened End cycle is closed, this Vsen1 is inductive current sampling of the inductive current rise period T2 in the 0.5T1 instance sample of the period Value.In cycles, it is not repeating.

Figure 21 is that the utility model is converted in switch power converter for Boost type or Buck-Boost type Switching Power Supply Device works in dcm mode, and in the signal sequence relational graph of the failing edge of inductive current sampling load current.In first electricity After inducing current decline period T1 starts, the current sampling data Vsen1 an of switch periods is first exported, the T1+0.5T0 moment is reached With regard to sample rate current, updates current sampling data Vsen1 and be output to low-pass filter, the input signal Vsen2=of low-pass filter Vsen1, while this current sampling data being kept to drop to 0 until inductive current, disconnect sampling hold circuit and low-pass filter Electrical connection and the input signal Vsen2 of low-pass filter is dragged down.

Figure 22 is that the utility model is converted in switch power converter for Boost type or Buck-Boost type Switching Power Supply Device works in dcm mode, and in the signal sequence relational graph of the rising edge of inductive current sampling load current.In current switch After period inductive current rise period T1 starts, sample rate current is not exported externally first；When reaching the estimated midpoint 0.5T0 moment just Sample rate current obtains rising edge midpoint current sampling data Vsen1 and keeps, but do not export sampled current signals, low-pass filtering The input signal Vsen2 of device remains as 0 during inductance rises；From at the time of inductive current is begun to decline, so that low pass The input Vsen2=Vsen1, Vsen1 of filter are electricity of the inductive current rise period T1 in the 0.5T0 instance sample of the period Inducing current signal value；Sampling hold circuit exports current sampling data Vsen1 to low-pass filter, until inductive current drops to 0, The electrical connection of sampling hold circuit and low-pass filter disconnects, and the input signal Vsen2 level of low-pass filter is dragged down.One Kind switch power converter load current detection method is the following steps are included: obtain switch power converter in A and B Inductive current rise period or the total time T for declining the period_AAnd T_B, B is equal to A+1；The B inductive current rise period or under The start time for dropping the period, which rises, passes through 0.5T_AAt the time of afterwards, i.e., point moment T in first_MBLoad current is sampled, and is protected by sampling Holding circuit keeps the load current sampled value to point moment T in second_MC；Point moment T in described second_MCFor the C inductance electricity It flows rise period or declines the start time of period and rise by 0.5T_BAt the time of afterwards；The point moment T in first_MBTo the second midpoint Moment T_MCIn this period, the current sampling signal kept using sampling, according to different types of circuit and different Working moulds Formula is transformed to load current signal.Load current sampled signal obtains switch power converter after low-pass filter is smooth Load current signal.No matter which kind of type circuit, the time not output load current sampled value for being zero in inductive current.

By cleverly timing control, when by inductive current rise period in the switching signal period passed or decline For the simulation of current period inductive current rise period or the middle point moment for declining the period, and dexterously exist the total time of section The sampling that the moment carries out is kept, and takes full advantage of and the line of inductive current in period or continued flow tube conducting period is connected in switching tube Property feature, simplifies load detecting circuit；Simultaneously because the sampling instant is nearly or approximately switching tube conducting period or afterflow Pipe be connected the period midpoint, sample rate current size be usually in the best response interval range that amplifier work, therefore entirety Load current detection accuracy is also improved, and is not only avoided complicated circuit design, is also improved the detection of load current Precision reduces the complexity and difficulty of circuit；Circuit structure is simply ingenious, strong applicability can with Buck, Boost and The various DCDC switch power converters of Buck-Boost；Either switching tube or continued flow tube can be restored with this method The size of load current, strong flexibility；Also it is common to the detection of power tube proportional current, series resistance current detection circuit, it is synchronous Or asynchronous rectification circuit；In Application of integrated circuit, it is easy to application deployment, saves chip area.

The above description is only the embodiments of the present invention, and therefore it does not limit the scope of the patent of the utility model, all Using equivalent structure or equivalent flow shift made by utility model specification and accompanying drawing content, it is applied directly or indirectly in it His relevant technical field, is also included in the patent protection scope of the utility model.

Claims (14)

1. a kind of inductive type switch power converter load current detection circuit, it is characterised in that:

It is adopted including inductive current rise period or decline period midpoint detection circuit (32) and for what load current sampling was kept Sample holding circuit (34)；

The inductive current rise period or decline period midpoint detection circuit (32), for obtaining in the A switch periods Inductive current rise period or decline period are denoted as T_A, it is also used to obtain the inductive current rise period in the B switch periods Or the decline period is denoted as T_B, B is equal to A+N；

The inductive current rise period or decline period midpoint detection circuit (32), are also used to obtain in the B switch periods First in point moment T_MBWith point moment T in second in the C switch periods_MC；Point moment T in described first_MBIt is B The start time of inductive current rise period or decline period, which rise, in switch periods passes through 0.5T_AAt the time of afterwards；In described second Point moment T_MCIt rises for inductive current rise period in the C switch periods or the start time for declining the period by 0.5T_BAfterwards Moment；Wherein C is equal to B+M；A, B, C, N and M are the natural number more than or equal to 1；

The inductive current rise period or decline period midpoint detection circuit (32) and the sampling hold circuit (34) are electrically connected It connects, the inductive current rise period or decline period midpoint detection circuit (32) output midpoint time-ofday signals to sampling keep electricity Road (34)；The midpoint time-ofday signals include point moment T in first_MBWith second in point moment T_MCInformation；Sampling hold circuit (34) point moment T in sampling first_MBLoad current, and the load current sampled is kept to renewable time i.e. the second midpoint Moment T_MC；The point moment T in first_MBTo point moment T in second_MCIn this period,

If switch power converter is Buck type switch power converter, all exported in inductive current rising and falling time section Load current sampled signal；If switch power converter is Boost type or Buck-Boost type switch power converter, in electricity The period output load current sampled signal of inducing current decline.

2. inductive type switch power converter load current detection circuit as described in claim 1, it is characterised in that:

It further include low-pass filter (35)；

The low-pass filter (35) and sampling hold circuit (34) electrical connection；

The load current sampled signal of low-pass filter (35) is input to through the low-pass filter from sampling hold circuit (34) (35) it is exported after low-pass filtering.

3. inductive type switch power converter load current detection circuit as described in claim 1, it is characterised in that:

The inductive current rise period or decline period midpoint detection circuit (32) include that the first midpoint detection switchs, in second Point detection switch, third midpoint detection switch, the 4th midpoint detection switch, the first midpoint detection capacitor, the second midpoint detection electricity Appearance, midpoint detection operational amplifier, two an equal amount of current sources i.e. the first current source and the second current source, wherein the first electricity Stream source is used for Injection Current, and the second current source is for exporting electric current；

The inverting input terminal that the output terminal of first current source passes through the first midpoint detection switch and midpoint detection operational amplifier Son electrical connection, the output terminal of the first current source also pass through the same phase of the second midpoint detection switch and midpoint detection operational amplifier Input terminal electrical connection；The input terminal of second current source passes through third midpoint detection switch and midpoint detection operational amplifier Reversed input terminal electrical connection, the input terminal of the second current source also passes through the 4th midpoint detection switch and midpoint detection operation is put The in-phase input terminal electrical connection of big device；

The electrical connection of one end of the in-phase input terminal of midpoint detection operational amplifier and the second midpoint detection capacitor, the inspection of the second midpoint Survey the other end ground connection of capacitor；One end of the reversed input terminal of midpoint detection operational amplifier and the first midpoint detection capacitor electricity Connection, the other end ground connection of the first midpoint detection capacitor；The capacitance phase of first midpoint detection capacitor and the second midpoint detection capacitor Together；

First midpoint detection switch and the 4th midpoint detection switch receive the first midpoint detection control signal (Φ 1) control；When When one midpoint detection control signal is high level, the first midpoint detection switch and the 4th midpoint detection switch are all closed, and make to switch Both ends are connected；When the first midpoint detection control signal is low level, the first midpoint detection switch and the 4th midpoint detection switch It all opens, disconnects switch ends；

Second midpoint detection switch and third midpoint detection switch receive the second midpoint detection control signal (Φ 1B) control；When When two midpoint detections control signal is high level, the second midpoint detection switch and third midpoint detection switch are all closed, and make to switch Both ends are connected；When the second midpoint detection control signal is low level, the second midpoint detection switch and third midpoint detection switch It all opens, disconnects switch ends；

First midpoint detection controls signal (Φ 1) or upper second midpoint detection control signal (Φ 1B) is equal to inductive type Switching Power Supply The switching signal of converter；When switching signal is in the odd number period, the first midpoint detection controls the height of signal (Φ 1) Level is identical as the high level of switching signal；When switching signal is in the even number period, the second midpoint detection control letter The high level of number (Φ 1B) is identical as the high level of switching signal；

The output terminal of midpoint detection operational amplifier exports the first midpoint time-ofday signals, which is sent to The sampling hold circuit (34), controls the sampling instant of sample circuit.

4. inductive type switch power converter load current detection circuit as claimed in claim 3, it is characterised in that:

The inductive current rise period or decline period midpoint detection circuit (32) further include d type flip flop and XOR gate；

The switching signal for the control of inductive type switch power converter that the clock signal of the d type flip flop is an externally input； Second output terminal sub (Qn) electrical connection of the first input end (D) and the d type flip flop of the d type flip flop, the d type flip flop First lead-out terminal (Q) output signal to an input terminal of XOR gate；

The output terminal of midpoint detection operational amplifier exports another input terminal of the first midpoint time-ofday signals to XOR gate, The output terminal of XOR gate exports the second midpoint time-ofday signals, which is sent to the sampling hold circuit (34), the sampling instant of sample circuit is controlled.

5. inductive type switch power converter load current detection circuit as claimed in claim 4, it is characterised in that:

The first lead-out terminal (Q) of the d type flip flop outputs signal to first and door, controls with inductive type switch power converter Switching signal carry out and operation, output the first midpoint detection control signal (Φ 1)；

The second output terminal of the d type flip flop (Qn) outputs signal to second and door, with inductive type switch power converter control The switching signal of system carries out and operation, output the second midpoint detection control signal (Φ 1B).

6. inductive type switch power converter load current detection circuit as claimed in claim 4, it is characterised in that:

The sampling hold circuit (34) keeps opening including the second sample-hold switch, the second sampling holding capacitor, third sampling It closes, third sampling holding capacitor and sampling keep operational amplifier；

One end of second sample-hold switch, which is used to connect with external inductive current detection circuit, obtains load current sampling letter Number, the other end of the second sample-hold switch is simultaneously and one end of the second sampling holding capacitor and third sample-hold switch One end electrical connection, the other end ground connection of the second sampling holding capacitor；The other end of third sample-hold switch is protected with sampling simultaneously The in-phase input terminal of operational amplifier and one end electrical connection of third sampling holding capacitor are held, third samples the another of holding capacitor One end ground connection；Sampling keeps the reversed input terminal of operational amplifier and sampling that the output terminal of operational amplifier is kept to be electrically connected It connects；

Second sample-hold switch is controlled by the non-signal of the second midpoint time-ofday signals, when the non-signal of the second midpoint time-ofday signals When for high level, the second sample-hold switch closure connects switch ends, when the non-signal of the second midpoint time-ofday signals is low When level, the second sample-hold switch opening disconnects switch ends；

Third sample-hold switch is controlled by the second midpoint time-ofday signals, when the second midpoint time-ofday signals are high level, third Sample-hold switch closure connects switch ends, when the second midpoint time-ofday signals are low level, third sample-hold switch Opening disconnects switch ends.

7. inductive type switch power converter load current detection circuit as claimed in claim 2, it is characterised in that:

It further include inductive current zero-crossing detection circuit (31), for obtaining low-pass filtering switch control signal.

8. inductive type switch power converter load current detection circuit as claimed in claim 7, it is characterised in that:

It is switched and is electrically connected by low-pass filtering between the low-pass filter (35) and sampling hold circuit (34)；The low pass filtered Wave switch is controlled by the low-pass filtering switch control signal exported from inductive current zero-crossing detection circuit (31)；

When inductive current is zero, low-pass filtering switch control signal controls the low-pass filtering switch and opens, and makes switch ends It disconnects, so that being disconnected between the low-pass filter (35) and sampling hold circuit (34), and low pass The input grounding of filter (35)；When inductive current is non-zero, low-pass filtering switch control signal controls the low-pass filtering Closing the switch connects switch ends, to make to be electrically connected between the low-pass filter (35) and sampling hold circuit (34).

9. inductive type switch power converter load current detection circuit as claimed in claim 8, it is characterised in that:

It further include low-pass filtering input drop-down metal-oxide-semiconductor, for the interruption in low-pass filter (35) and sampling hold circuit (34) After opening connection, the input of the low-pass filter (35) is dragged down, so that the low-pass filter (35) input is zero.

10. inductive type switch power converter load current detection circuit as claimed in claim 9, it is characterised in that:

The low-pass filter (35) includes one or more levels low-pass filter.

11. inductive type switch power converter load current detection circuit as claimed in claim 10, it is characterised in that:

When the low-pass filter (35) is level-one RC low-pass filter, level-one RC low-pass filter includes low-pass filtering resistance With low-pass filtering capacitor；

One end electrical connection of one end of the low-pass filtering resistance and low-pass filtering switch, meanwhile, the low-pass filtering resistance One end and low-pass filtering input drop-down metal-oxide-semiconductor source electrode electrical connection, low-pass filtering input drop-down metal-oxide-semiconductor grid access low pass Filtered switch controls the non-signal of signal, the grounded drain of low-pass filtering input drop-down metal-oxide-semiconductor；

The other end of the low-pass filtering resistance is used as the output terminal of low-pass filter (35), while the low-pass filtering electricity The other end of resistance is also electrically connected with one end of low-pass filtering capacitor, the other end ground connection of low-pass filtering capacitor.

12. inductive type switch power converter load current detection circuit as described in claim 1, it is characterised in that:

It further include for sampling the inductive current detection circuit (30) for obtaining load current；

The inductive current detection circuit (30) and the sampling hold circuit (34) electrical connection；

Inductive current detection circuit (30) is to sampling hold circuit (34) output load current signal.

13. a kind of inductive type switch power converter, it is characterised in that:

Include the electricity of inductive type switch power converter load current detection described in any one of the claims 1 to 12 Road.

14. inductive type switch power converter as claimed in claim 13, it is characterised in that:

It further include logic control circuit；The logic control circuit is for generating inductive type switch power converter timing control Basic switching signal；

The logic control circuit generates the first control signal for controlling two power switch tubes according to basic switching signal GP and second control signal GN；When first control signal GP is high level, one of power tube is opened；First control signal GP When for low level, another power tube is opened；First control signal GP and second control signal GN is basic switching signal Synchronous transformation signal；The inductive current rise time section and inductive current fall time section be synchronized with first control signal GP and Second control signal GN；To which inductive current rise time section and inductive current fall time section and basic switching signal are also same Step.