CN115395778A - DC-DC converter - Google Patents
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- CN115395778A CN115395778A CN202211191531.4A CN202211191531A CN115395778A CN 115395778 A CN115395778 A CN 115395778A CN 202211191531 A CN202211191531 A CN 202211191531A CN 115395778 A CN115395778 A CN 115395778A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
- H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
- H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
- H02M3/1566—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators with means for compensating against rapid load changes, e.g. with auxiliary current source, with dual mode control or with inductance variation
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0003—Details of control, feedback or regulation circuits
- H02M1/0009—Devices or circuits for detecting current in a converter
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0003—Details of control, feedback or regulation circuits
- H02M1/0025—Arrangements for modifying reference values, feedback values or error values in the control loop of a converter
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
- H02M1/088—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
- H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
- H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
- H02M3/157—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators with digital control
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
- H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
- H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
- H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
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Abstract
A DC-DC converter, characterized by: the converter comprises a mode switching unit, a first current detection unit, a second current detection unit, a third current detection unit and a logic module; the mode switching unit is used for comparing a reference voltage with an output voltage Vea of the error amplifier to obtain a first control signal OUT1; the first current detection unit is used for generating a second control signal OUT2, and the second current detection unit and the third current detection unit are used for generating a third control signal OUT3; and the logic unit is used for realizing the conversion of the light-load or heavy-load working state of the converter based on the first control signal OUT1 and realizing the control of the on-off state of a power tube in the converter under the light-load working state of the converter based on the second control signal OUT2 and the third control signal OUT3. The invention makes the DC-DC enter the light load working mode at a reasonable fixed load current point.
Description
Technical Field
The present invention relates to the field of integrated circuits, and more particularly, to a DC-DC converter.
Background
A DC-DC (Direct Current-Direct Current) converter is widely used in an integrated circuit as a voltage converter capable of converting an input voltage and effectively outputting a fixed voltage. In the case of a step-up converter,
the DC-DC converter can provide two different working modes of light load and heavy load so as to improve the adaptability of the DC-DC converter and meet the power supply requirements of more different types of rear-stage loads. In the prior art, when the DC-DC converter operates in a light load state, a peak value of an inductor current is clamped on a fixed minimum threshold current Ntrip and is not reduced, and meanwhile, an on or off state of a power tube in the converter is controlled by a light load operation mode, so that the inductor current is normally output in one period, and the inductor current is shielded from being output in the next period, and the output voltage is stably controlled by a cyclic reciprocation. In the present invention, a period in which the inductor current is normally output is referred to as an output interval, and a period in which the inductor current cannot be output is referred to as a non-output interval.
In the prior art, the switching point of the DC-DC converter for realizing the light load and heavy load operation modes varies with the input and output voltages. Since the output ripple of the DC-DC converter is large when the DC-DC converter is operated under light load, which affects the application, some applications may require the switching point of the DC-DC converter under light load and heavy load to be constant. The prior art is not satisfactory for this particular application.
Therefore, a new DC-DC converter is needed.
Disclosure of Invention
In order to solve the defects in the prior art, an object of the present invention is to provide a DC-DC converter, which can enter a light load operation mode at a reasonable fixed load current point by reasonably adjusting the minimum value of the inductor current.
The invention adopts the following technical scheme.
The invention relates to a DC-DC converter, which comprises a clock generating circuit, a logic unit, a delay unit, a power tube, an inductor, an output capacitor, a divider resistor and an error amplifier, and also comprises a mode switching unit, a first current detection unit, a second current detection unit, a third current detection unit and a logic module; the mode switching unit is used for comparing a reference voltage with an output voltage Vea of the error amplifier to obtain a first control signal OUT1; the first current detection unit is used for generating a second control signal OUT2, and the second current detection unit and the third current detection unit are used for generating a third control signal OUT3; and the logic unit is used for realizing the conversion of the light-load or heavy-load working state of the converter based on the first control signal OUT1 and realizing the control of the on-off state of the power tube in the converter under the light-load working state of the converter based on the second control signal OUT2 and the third control signal OUT3.
Preferably, when the first control signal OUT1 is in a high level state, the logic unit controls the converter to enter a light load working state, and the inductor current is shielded or output at a set interval; when the inductor current is in the output interval, the second control signal OUT2 and the third control signal OUT3 control the high-side power transistor to be turned on and the low-side power transistor to be turned off, so as to increase the amplitude of the inductor current, or control the high-side power transistor to be turned off and the low-side power transistor to be turned on, so as to decrease the amplitude of the inductor current.
Preferably, the mode switching unit includes a first comparator COMP1, a positive phase input end of the comparator COMP1 is connected to the reference voltage V1, a negative phase input end of the comparator COMP1 is connected to the output voltage Vea of the error amplifier, and an output end of the comparator COMP1 generates the first control signal OUT1.
Preferably, the first current detection unit includes a current amplification circuit and a second comparator COMP2; the current amplifying circuit is used for acquiring the inductive current, converting the inductive current into a detection voltage OUT4 and outputting the detection voltage OUT4 to a positive phase input end of a second comparator COMP2; the negative phase input end of the second comparator is connected with the output voltage Vea of the error amplifier, the output end of the second comparator generates a second control signal OUT2 which is input to the logic module, preferably, the second current detection unit is used for collecting inductive current and converting the inductive current according to a conversion coefficient K 1 It is converted into an amplified current I2, and the amplified current is input to the third current detection unit.
Preferably, the third current detection unit comprises an output voltage acquisition unit, an input voltage acquisition unit, a comparison unit and an output mirror image unit; the input ends of the output voltage acquisition unit and the input voltage acquisition unit are respectively connected with the output voltage of the converter and the input voltage of the converter; the output ends of the output voltage acquisition unit and the input voltage acquisition unit are respectively connected to the two input ends of the comparison unit; the comparison unit generates a comparison current ICQ4 after the comparison is realized, and generates a detection current I1 after passing through the output mirror image unit.
Preferably, the third current detection unit further comprises two inverters connected in series, and input ends of the inverters are respectively connected to an output end of the second current detection unit and an output end of the third current detection unit; the output end of the inverter is connected with the logic unit.
Preferably, the output voltage acquisition unit includes an operational amplifier OPA1, a voltage dividing resistor R1 and a mirror MOS transistor, and is configured to generate a first comparison current Vout/R1 based on a positive phase input signal Vout of the operational amplifier OPA 1; the input voltage acquisition unit comprises an operational amplifier OPA2, a voltage division resistor R2 and a mirror MOS (metal oxide semiconductor) transistor and is used for generating a second comparison current Vin/R2 based on a positive phase input signal Vin of the operational amplifier OPA 2.
Preferably, the comparison unit comprises a base control tube, first-stage symmetrical tubes Q2 and Q3, second-stage symmetrical tubes Q1 and Q4, a first-stage current source Iref and a second-stage current source Ix; the grid electrode of the base electrode control tube is connected with the output end of the output voltage acquisition unit, the drain electrode of the base electrode control tube is connected with power supply voltage, the source electrode of the base electrode control tube is respectively connected with the base electrodes of the first-stage symmetrical tubes Q2 and Q3 and one end of a first-stage current source Iref, and the other end of the first-stage current source Iref is grounded; collectors of the first-stage symmetrical tubes Q2 and Q3 are connected with power supply voltage, an emitter of the Q2 is grounded after passing through a second-stage current source Ix, and a collector of the Q3 is connected with the output end of the input voltage acquisition unit; bases of the secondary symmetrical tubes Q1 and Q4 are respectively connected with emitters of the primary symmetrical tubes Q2 and Q3, the emitters are respectively grounded, a collector of the Q1 is connected with an output end of the output voltage acquisition unit and a grid of the base control tube, and a collector of the Q4 is connected with an input end of the output mirror image unit; the output mirror image unit comprises a mirror image MOS tube.
Preferably, the output current of the comparison unit is
Wherein,
I x is the output current of the secondary current source.
Preferably, the maximum magnitude of the inductor current is limited to be such that the converter is in a light load mode of operation
And the maximum amplitude of the load current is limited to a constant value
Compared with the prior art, the DC-DC converter has the beneficial effects that the DC-DC converter can enter a light-load working mode at a reasonable fixed load current point by reasonably adjusting the minimum value of the inductive current.
The beneficial effects of the invention also include:
1. the invention only adopts a plurality of current detection modules to realize the control of the on-off state of the power tube, and covers the control signal of the on-off state of the power tube under the light load state by matching with the original working logic of the switching of the heavy load working mode and the light load working mode of the logic module, thereby realizing the dynamic control of the output amplitude of the inductive current. The method ensures that the inductance current can still adjust the amplitude of the inductance current according to the output voltage and the input voltage even in a light load state, thereby ensuring the matching of the converter to a load circuit in the light load state.
2. In the invention, the conservation between the input power and the output power of the converter is considered, so that the parameters of each element in the third current detection unit are skillfully designed, the converter can turn over when the load current is equal to a preset fixed current value, the aim of predicting which load point enters a light load mode is fulfilled, the load point can be accurately avoided by the application sensitive to output ripples, and the influence of input and output voltages is not required to be considered.
Drawings
Fig. 1 is a schematic diagram of an output voltage ripple of a DC-DC converter according to the prior art;
FIG. 2 is a schematic diagram of a DC-DC converter according to the present invention;
FIG. 3 is a schematic circuit diagram of a first current detecting unit in a DC-DC converter according to the present invention;
FIG. 4 is a schematic circuit diagram of a second current detecting unit in a DC-DC converter according to the present invention;
FIG. 5 is a schematic diagram of a partial circuit of a third current detecting unit in a DC-DC converter according to the present invention;
fig. 6 is a schematic diagram of an output of a third control signal in a third current detecting unit in a DC-DC converter according to the present invention.
Detailed Description
The present application is further described below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present application is not limited thereby.
Fig. 1 is a schematic diagram of an output voltage ripple of a DC-DC converter according to the prior art. As shown in fig. 1, in the prior art, the DC-DC converter can realize two different operation modes of light load and heavy load based on the state of the load. When the DC-DC converter works in a heavy load state, the amplitude of the inductor current can be adjusted according to the magnitude of the load current, and the output voltage is kept stable in the mode. When the power required by the rear-stage load is small, the DC-DC converter may enter a light-load state in which the magnitude of the inductor current is clamped to the minimum threshold current Ntrip, and the inductor current cannot be made smaller in order to maintain the operating state of the rear-stage load. At this time, in order to prevent the output voltage from rising, the DC-DC converter can ensure that the total output power is low by the interval output of the inductor current.
Therefore, in fig. 1, the inductor current oscillates to be output during the output interval period, and the output voltage slowly rises accordingly. In the non-output interval period, the inductor current is shielded, and the output voltage is slowly reduced accordingly. Under the cyclic reciprocating condition of a plurality of output intervals and non-output intervals, the output voltage has certain fluctuation, namely the ripple wave of the output voltage is larger than the ripple wave of the output voltage under the heavy load mode. For some applications sensitive to output ripple, the light load mode needs to be avoided, but the load current point entering the light load mode in the prior art varies with the input and output voltages, and the load current point entering the light load mode cannot be accurately predicted.
In the present invention, a circuit designer desires to accurately realize switching of the on or off state of the power transistor in the converter under the light load operating state according to the states of the input voltage and the output voltage, so as to ensure that the converter enters the light load mode under a fixed load current. . Accordingly, the present invention provides a new DC-DC converter.
Fig. 2 is a schematic diagram of a DC-DC converter according to the present invention. As shown in fig. 2, a DC-DC converter includes a clock generating circuit, a logic unit, a delay unit, a power tube, an inductor, an output capacitor, a voltage dividing resistor, and an error amplifier, and further includes a mode switching unit, a first current detecting unit, a second current detecting unit, a third current detecting unit, and a logic module; a mode switching unit for comparing a reference voltage with an output voltage Vea of the error amplifier to obtain a first control signal OUT1; the first current detection unit is used for generating a second control signal OUT2, and the second current detection unit and the third current detection unit are used for generating a third control signal OUT3; and the logic unit is used for realizing the conversion of the light-load or heavy-load working state of the converter based on the first control signal OUT1 and realizing the control of the on-off state of the power tube in the converter under the light-load working state of the converter based on the second control signal OUT2 and the third control signal OUT3.
It is understood that in the circuit shown in fig. 2, the first control signal OUT1 has a similar function to the switching control signal of the light load and heavy load operation states in the prior art, and can control the circuit to switch between the light load state and the heavy load state.
On the premise that the first control signal OUT1 controls the circuit to enter the light load mode, the second control signal OUT2 and the third control signal OUT3 can adjust the time length of the rising process and the time length of the falling process of the inductive current in each clock cycle, so that the converter can realize the reasonable output in the light load state in a self-adaptive manner no matter the rear-stage load is in any state.
Preferably, when the first control signal OUT1 is in a high level state, the logic unit controls the converter to enter a light load working state, and the inductor current is shielded or output at a set interval; when the inductor current is in the output interval, the second control signal OUT2 and the third control signal OUT3 control the high-side power tube to be turned on and the low-side power tube to be turned off and enable the amplitude of the inductor current to rise, or control the high-side power tube to be turned off and the low-side power tube to be turned on and enable the amplitude of the inductor current to fall.
It can be understood that, when the converter is in a light load state, in the idea of the present invention, it is desirable to compare the second control signal OUT2 containing information about the magnitude of the inductor current with the third control signal OUT3 containing information about the input voltage and the output voltage, so that when the ratio of the output voltage to the input voltage of the circuit is higher than a certain degree, the on or off state of the power tube in the circuit changes, and the inductor current changes from gradually increasing to gradually decreasing.
In this way, the second control signal OUT2 and the third control signal OUT3 control the state of the power transistor, thereby adjusting the maximum amplitude of the inductor current in each output period. Fundamentally, the product of the output voltage and the load current of the converter is equal to the product of the input voltage and the inductor current according to the conservation of power. Therefore, the proportional change of the output voltage and the input voltage and the change of the maximum amplitude value of the inductive current are offset to a certain extent, so that the circuit can realize accurate control of the maximum amplitude value of the load current in each period after flexibly controlling the amplitude value of the inductive current in each period.
Preferably, the mode switching unit includes a first comparator COMP1, a positive phase input end of the comparator COMP1 is connected to the reference voltage V1, a negative phase input end of the comparator COMP1 is connected to the output voltage Vea of the error amplifier, and an output end of the comparator COMP1 generates the first control signal OUT1.
In this circuit, the mode switching unit can achieve the acquisition of the feedback voltage Vfb by means of an error amplifier already present in the converter. Vfb is compared to a reference voltage Vref to achieve the error amplifier output Vea. The output voltage Vea realizes the output of the first control signal after comparison with the reference voltage V1.
Specifically, when Vfb, i.e., the divided voltage of the output voltage Vout is large, the first control signal OUT1 is in a high level state, and the circuit is switched from a heavy load state to a light load state. When the output voltage is low, the output of the first control signal OUT1 is also in a low level state, and the low level control logic unit implements a heavy load operation mode of the circuit. In other words, when the first control signal OUT1 is in a high state, the first control signal can simultaneously shield the control signals of the high-side power transistor and the low-side power transistor, so that both are in a cut-off state, and at this time, the inductor current is not output, and the circuit is in a non-output interval.
Preferably, the first current detection unit includes a current amplification circuit and a second comparator COMP2; the current amplifying circuit is used for acquiring the inductive current, converting the inductive current into a detection voltage OUT4 and outputting the detection voltage OUT4 to a positive phase input end of a second comparator COMP2; the negative phase input end of the second comparator is connected with the output voltage Vea of the error amplifier, and the output end of the second comparator generates a second control signal OUT2 which is input into the logic module.
Fig. 3 is a circuit diagram of a first current detecting unit in a DC-DC converter according to the present invention. As shown in fig. 3, the current amplifying circuit may be a circuit composed of a current mirror and a voltage dividing resistor. The MOS transistor Mn2 at one end of the current mirror is connected with the low-end power transistor Mn0 of the converter in a mirror image mode, namely the grids of the Mn0 and the Mn2 are connected with each other, and the sources are grounded. Therefore, the current mirror can receive the proportional current of the low-side power tube, namely the proportional current of the inductance current. After the current passes through the voltage dividing resistor, the voltage dividing resistor can realize the detection voltage OUT4 based on the change of the inductor current. Comparing the detection voltage with the output voltage Vea of the error amplifier, the second control signal OUT2 may be generated.
Specifically, assume that the amplification factor of the output voltage of the first current detection unit to the inductor current is K 1 When the inductor current I is L After input, the output voltage of the first current detection unit is K 1 ·I L . Therefore, when K 1 ·I L If the voltage is greater than Vea, the second control signal OUT2 is high, otherwise it is low. When the second control signal OUT2 is at a low level, the logic module in the circuit executes the original logic to realize the switching of the power tube. When the output of the second control signal OUT2 is high, it is necessary to determine the state of the other control signal OUT3.
For the present invention, the first current detection unit may also be implemented by using other circuits in the prior art as long as the current detection function can be implemented.
Preferably, the second current detection unit is configured to collect an inductor current, convert the inductor current into an amplified current I2, and input the amplified current to the third current detection unit.
Fig. 4 is a circuit diagram of a second current detecting unit in a DC-DC converter according to the present invention. As shown in fig. 4, the second current detecting unit may be formed by a mirror unit, which may mirror the drain current of the low-side power transistor of the converter, i.e. mirror the inductor current to the amplified current I2. In an embodiment of the invention, it can be assumed that the amplification factor of the second current detecting unit is K 2 So that the output of the cell then becomes I 2 ＝K 2 ·I L 。
Preferably, the third current detection unit comprises an output voltage acquisition unit, an input voltage acquisition unit, a comparison unit and an output mirror image unit; the input ends of the output voltage acquisition unit and the input voltage acquisition unit are respectively connected with the output voltage of the converter and the input voltage of the converter; the output ends of the output voltage acquisition unit and the input voltage acquisition unit are respectively connected to the two input ends of the comparison unit; the comparison unit generates a comparison current ICQ4 after realizing comparison, and generates a detection current I1 after passing through the output mirror image unit.
It can be understood that the third current detecting unit is designed to output the detecting current I1 through the output voltage, the input voltage and a current source with a fixed magnitude, and the detecting current I1 can be compared with the amplifying current I2 so that the circuit can output the control signal OUT3 with a state reversal based on whether the amplifying current is larger than the detecting current I1.
Preferably, the third current detection unit further comprises two inverters connected in series, and input ends of the inverters are respectively connected to an output end of the second current detection unit and an output end of the third current detection unit; the output end of the inverter is connected with the logic unit.
Fig. 6 is a schematic diagram of an output of a third control signal in a third current detecting unit in a DC-DC converter according to the present invention. As shown in fig. 6, the third control signal OUT3 may realize a low state after a time delay when the detection current I1 is greater than the amplification current I2, and the third control signal OUT3 is high if the detection current I1 is less than the amplification current I2. When the third control signal OUT3 is at a low level, the circuit implements a working state according to the original logic of the logic unit. If the energy at the input end of the converter is higher than that at the output end when the second and third control signals OUT2 and OUT3 are both at a high level, the logic unit controls the gate of the power transistor to turn off the high-side power transistor (i.e., mp 0) and turn on the low-side power transistor (i.e., mn 0), and at this time, the inductor current of the converter will gradually decrease. When the clock signal reaches the next periodic pulse, the high-side power tube is turned on again, and the low-side power tube is turned off again, so that the inductor current rises again.
It should be noted that when OUT1 is high, the power transistors NMOS and PMOS are turned off simultaneously. When OUT1 is low, OUT2 and OUT3 function as described in the preceding paragraphs.
Fig. 5 is a schematic diagram of a part of a circuit in a third current detecting unit of a DC-DC converter according to the present invention. As shown in fig. 5, preferably, the output voltage acquisition unit includes an operational amplifier OPA1, a voltage dividing resistor R1 and a mirror MOS transistor, and is configured to generate a first comparison current Vout/R1 based on a non-inverting input signal Vout of the operational amplifier OPA 1; the input voltage acquisition unit comprises an operational amplifier OPA2, a voltage division resistor R2 and a mirror MOS (metal oxide semiconductor) transistor and is used for generating a second comparison current Vin/R2 based on a positive phase input signal Vin of the operational amplifier OPA 2.
It can be understood that in the output voltage acquisition unit, the OPA1 negative feedback mode is connected with the gate and the source of the MOS transistor, when the positive phase input end voltage of the OPA1 is Vout, the MOS transistor is conducted, so that the negative phase input end voltage is also equal to Vout, and the unit can generate V under the action of the resistor out /R 4 Is constant current. Similarly, the current input to the voltage acquisition unit is V in /R 5 。
Preferably, the comparing unit comprises a base electrode control tube, first-stage symmetrical tubes Q2 and Q3, second-stage symmetrical tubes Q1 and Q4, a first-stage current source Iref and a second-stage current source Ix; the grid electrode of the base electrode control tube is connected with the output end of the output voltage acquisition unit, the drain electrode of the base electrode control tube is connected with power supply voltage, the source electrode of the base electrode control tube is respectively connected with the base electrodes of the first-stage symmetrical tubes Q2 and Q3 and one end of a first-stage current source Iref, and the other end of the first-stage current source Iref is grounded; collectors of the first-stage symmetrical tubes Q2 and Q3 are connected with power supply voltage, an emitter of the Q2 is grounded after passing through a second-stage current source Ix, and a collector of the Q3 is connected with an output end of the input voltage acquisition unit; bases of the second-level symmetrical tubes Q1 and Q4 are respectively connected with emitting electrodes of the first-level symmetrical tubes Q2 and Q3, the emitting electrodes are respectively grounded, a collector electrode of the Q1 is connected with an output end of the output voltage acquisition unit and a grid electrode of the base electrode control tube, a collector electrode of the Q4 is connected with an input end of the output mirror image unit, and the output mirror image unit comprises a mirror image MOS tube.
For this circuit, the comparison unit may input and compare the first comparison current and the second comparison current generated above. Specifically, according to the connection mode of the circuit, the source voltage controlled by the base can be calculated by two different methods. This voltage is equal to the sum of Vbe of the base emitters of the symmetrical tubes Q1 and Q2, on the one hand, and also to the sum of Vbe of the symmetrical tubes Q3 and Q4, on the other hand.
Thus, the following equation can be listed:
V be-Q1 +V be-Q2 ＝V be-Q3 +V be-Q4
because the base control tube keeps opening under the effect of the output end of the output voltage acquisition unit, the source voltage of the base control tube is higher, and the opening of the symmetrical tubes Q1 to Q4 can be fully ensured, therefore, the emitter current of Q1 is approximately equal to the base current of Q1, namely the output current V of the output voltage acquisition unit out /R 4 While the emitter current of Q2 is equal to the current of current source Ix. Similarly, the emitter current of Q3 is equal to the output current V of the input voltage acquisition unit in /R 5 The source current of Q4 is determined by Q1 and Q2, Q3.
In addition, V be Is calculated by the formula
Wherein V T Is the threshold voltage of the transistor, I C Is collector current, I S Is a saturation current. It can be assumed that the four transistors Q1 to Q4 are identical in model, and therefore the magnitudes of the threshold voltage and the saturation current are also identical.
Thus, the above formula can be converted as follows:
V be-Q1 +V be-Q2 ＝V be-Q3 +V be-Q4
by simplifying the above formula, we can obtain
Thus, can obtain
If the output mirror image unit also has a certain amplification ratio, the amplification ratio is equal to
Multiplying by a ratio K equal to the current mirror 3 The output current of the output mirror unit may be
Comparing the amplified current I2 with the detected current I1, it can be found that when the amplified current I2 and the detected current I1 are equal, there is a difference
Therefore, the circuit should have the time point of the conversion between the output interval and the non-output interval in the light load mode
According to the conservation of power of the converter, there are
Therefore, the number of the first and second electrodes is increased,
due to the fact that
And I x Are controllable, are fixed and are independent of input and output voltages, and therefore, I when entering a light load mode load The size is fixed.
Preferably, the maximum magnitude of the inductor current is limited to be such that the converter is in a light load mode of operation
The point of load Iload entering the light load mode is therefore limited to a constant value
Wherein, K 3 To output the mirror unit
The product of (a).
Compared with the prior art, the DC-DC converter has the beneficial effects that the minimum value of IL can be reasonably adjusted, so that the circuit enters a light-load working mode at a fixed load current point. The fixed load point is not changed along with the input and output voltage, so that the application of a later stage is more convenient.
The present applicant has described and illustrated embodiments of the present invention in detail with reference to the accompanying drawings, but it should be understood by those skilled in the art that the above embodiments are merely preferred embodiments of the present invention, and the detailed description is only for the purpose of helping the reader to better understand the spirit of the present invention, and not for limiting the scope of the present invention, and on the contrary, any improvement or modification made based on the spirit of the present invention should fall within the scope of the present invention.
Claims (10)
1. A DC-DC converter comprises a clock generation circuit, a logic unit, a delay unit, a power tube, an inductor, an output capacitor, a divider resistor and an error amplifier, and is characterized in that:
the converter further comprises a mode switching unit, a first current detection unit, a second current detection unit, a third current detection unit and a logic module;
the mode switching unit is used for comparing a reference voltage with an output voltage Vea of the error amplifier to obtain a first control signal OUT1;
the first current detection unit is used for generating a second control signal OUT2, and the second current detection unit and the third current detection unit are used for generating a third control signal OUT3;
the logic unit is used for realizing the conversion of the light-load or heavy-load working state of the converter based on the first control signal OUT1 and realizing the control of the on-off state of a power tube in the converter under the light-load working state of the converter based on the second control signal OUT2 and the third control signal OUT3.
2. A DC-DC converter according to claim 1, wherein:
when the first control signal OUT1 is in a high level state, the logic unit controls the converter to enter a light load working state, and the inductor current is shielded or output at a set interval;
when the inductor current is in the output interval, the second control signal OUT2 and the third control signal OUT3 control the high-side power transistor to be turned on and the low-side power transistor to be turned off, so as to increase the amplitude of the inductor current, or control the high-side power transistor to be turned off and the low-side power transistor to be turned on, so as to decrease the amplitude of the inductor current.
3. A DC-DC converter according to claim 2, wherein:
the mode switching unit comprises a first comparator COMP1, a positive phase input end of the comparator COMP1 is connected with a reference voltage V1, a negative phase input end of the comparator COMP1 is connected with an output voltage Vea of the error amplifier, and an output end of the comparator COMP1 generates a first control signal OUT1.
4. A DC-DC converter according to claim 3, wherein:
the first current detection unit comprises a current amplification circuit and a second comparator COMP2; wherein,
the current amplifying circuit is used for converting the inductor current into a detection voltage OUT4 after acquiring the inductor current and outputting the detection voltage OUT4 to a positive phase input end of a second comparator COMP2;
the negative phase input end of the second comparator is connected to the output voltage Vea of the error amplifier, and the output end of the second comparator generates a second control signal OUT2 which is input into the logic module;
the second current detection unit is used for collecting the inductive current and converting the inductive current according to a conversion coefficient K 1 Converts it into an amplified current I2, and inputs the amplified current to the third current detection unit.
5. A DC-DC converter according to claim 4, wherein:
the third current detection unit comprises an output voltage acquisition unit, an input voltage acquisition unit, a comparison unit and an output mirror image unit; wherein,
the input ends of the output voltage acquisition unit and the input voltage acquisition unit are respectively connected to the output voltage of the converter and the input voltage of the converter;
the output ends of the output voltage acquisition unit and the input voltage acquisition unit are respectively connected to the two input ends of the comparison unit;
the comparison unit generates a comparison current ICQ4 after comparison, and generates the detection current I1 after passing through the output mirror image unit.
6. A DC-DC converter according to claim 5, wherein:
the third current detection unit also comprises two inverters which are connected in series, and the input ends of the inverters are respectively connected with the output end of the second current detection unit and the output end of the third current detection unit;
the output end of the phase inverter is connected with the logic unit.
7. A DC-DC converter according to claim 5, wherein:
the output voltage acquisition unit comprises an operational amplifier OPA1, a voltage division resistor R1 and a mirror MOS (metal oxide semiconductor) tube and is used for generating a first comparison current Vout/R1 based on a positive phase input signal Vout of the operational amplifier OPA 1;
the input voltage acquisition unit comprises an operational amplifier OPA2, a voltage division resistor R2 and a mirror MOS (metal oxide semiconductor) transistor and is used for generating a second comparison current Vin/R2 based on a positive phase input signal Vin of the operational amplifier OPA 2.
8. A DC-DC converter according to claim 7, wherein:
the comparison unit comprises a base electrode control tube, primary symmetrical tubes Q2 and Q3, secondary symmetrical tubes Q1 and Q4, a primary current source Iref and a secondary current source Ix; wherein,
the grid electrode of the base electrode control tube is connected with the output end of the output voltage acquisition unit, the drain electrode of the base electrode control tube is connected with power supply voltage, the source electrode of the base electrode control tube is respectively connected with the base electrodes of the first-stage symmetrical tubes Q2 and Q3 and one end of a first-stage current source Iref, and the other end of the first-stage current source Iref is grounded;
the collector electrodes of the first-stage symmetrical tubes Q2 and Q3 are connected with a power supply voltage, the emitter electrode of the Q2 is grounded after passing through a second-stage current source Ix, and the collector electrode of the Q3 is connected with the output end of the input voltage acquisition unit;
bases of the second-stage symmetrical tubes Q1 and Q4 are respectively connected with emitting electrodes of the first-stage symmetrical tubes Q2 and Q3, the emitting electrodes are respectively grounded, a collector electrode of the Q1 is connected with an output end of the output voltage acquisition unit and a grid electrode of the base electrode control tube, and a collector electrode of the Q4 is connected with an input end of the output mirror image unit;
the output mirror image unit comprises a mirror image MOS tube.
9. A DC-DC converter according to claim 8, wherein:
the output current of the comparison unit is
Wherein,
I x is the output current of the secondary current source.
10. A DC-DC converter according to claim 9, wherein:
maximum amplitude of the inductor current when the converter is in a light load operating modeThe value is limited to
And the maximum amplitude of the load current is limited to a constant value
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211191531.4A CN115395778A (en) | 2022-09-28 | 2022-09-28 | DC-DC converter |
| PCT/CN2023/120353 WO2024067343A1 (en) | 2022-09-28 | 2023-09-21 | Dc-dc converter |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202211191531.4A CN115395778A (en) | 2022-09-28 | 2022-09-28 | DC-DC converter |
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| WO2024067343A1 (en) * | 2022-09-28 | 2024-04-04 | 圣邦微电子(苏州)有限责任公司 | Dc-dc converter |
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| CN101510721B (en) * | 2009-03-18 | 2012-04-25 | 浙江大学 | Single inductance switch DC voltage converter and three mode control method |
| CN102497103B (en) * | 2011-12-24 | 2014-03-19 | 西安启芯微电子有限公司 | High efficiency DC-DC conversion device in light load |
| CN113839556B (en) * | 2020-06-24 | 2023-08-22 | 圣邦微电子（北京）股份有限公司 | DC-DC converter and control circuit thereof |
| CN115395778A (en) * | 2022-09-28 | 2022-11-25 | 圣邦微电子(苏州)有限责任公司 | DC-DC converter |
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2022
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| WO2024067343A1 (en) * | 2022-09-28 | 2024-04-04 | 圣邦微电子(苏州)有限责任公司 | Dc-dc converter |
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