CN109039085B - Control circuit and switching power supply using same - Google Patents
Control circuit and switching power supply using same Download PDFInfo
- Publication number
- CN109039085B CN109039085B CN201810888306.3A CN201810888306A CN109039085B CN 109039085 B CN109039085 B CN 109039085B CN 201810888306 A CN201810888306 A CN 201810888306A CN 109039085 B CN109039085 B CN 109039085B
- Authority
- CN
- China
- Prior art keywords
- voltage
- output voltage
- port
- power supply
- feedback
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 238000004804 winding Methods 0.000 claims abstract description 56
- 238000005070 sampling Methods 0.000 claims abstract description 14
- 230000008859 change Effects 0.000 claims description 43
- 238000001514 detection method Methods 0.000 claims description 40
- 238000000034 method Methods 0.000 claims description 15
- 238000004891 communication Methods 0.000 claims description 6
- 230000003247 decreasing effect Effects 0.000 claims description 4
- 230000009191 jumping Effects 0.000 claims description 4
- 230000008569 process Effects 0.000 description 9
- 239000003990 capacitor Substances 0.000 description 8
- 238000010586 diagram Methods 0.000 description 8
- 230000005540 biological transmission Effects 0.000 description 6
- 238000002955 isolation Methods 0.000 description 5
- 238000004364 calculation method Methods 0.000 description 3
- 238000004146 energy storage Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 230000006978 adaptation Effects 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 230000005347 demagnetization Effects 0.000 description 1
- 238000012938 design process Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- BINCGEGLXIMJFO-JQSLHUNDSA-N rfa-2 Chemical compound C1([C@H]2N[C@H](CC3(N=C4C=5C6=C7O[C@](C6=O)(C)O/C=C/[C@@H]([C@H]([C@@H](OC(C)=O)[C@@H](C)[C@@H](O)[C@H](C)[C@@H](O)[C@@H](C)\C=C\C=C(C)/C(=O)NC(=C4N3)C(=O)C=5C(O)=C7C)C)OC)C2)C=2C=CC(F)=CC=2)=CC=C(F)C=C1 BINCGEGLXIMJFO-JQSLHUNDSA-N 0.000 description 1
Classifications
-
- 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
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33507—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters
- H02M3/33523—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters with galvanic isolation between input and output of both the power stage and the feedback loop
-
- 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
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Dc-Dc Converters (AREA)
Abstract
The invention discloses a control circuit and a switching power supply using the same, wherein the control circuit is suitable for an isolating switching power supply with a primary circuit formed by a primary winding of a transformer and a secondary circuit formed by a secondary winding of the transformer, and comprises the following components: the power supply system is characterized by also comprising a current source module for extracting a voltage division sampling point of the upper resistor for detecting the voltage of the auxiliary winding and the lower resistor for detecting the voltage of the auxiliary winding, and the output voltage decoding feedback module.
Description
Technical Field
The invention relates to a switching power supply control circuit, in particular to a magnetically isolated high-output voltage secondary side feedback control circuit and a switching power supply using the same.
Background
In order to avoid the interference and damage of the load to the power supply input terminal, an isolated switching power supply has become an indispensable part of various power supply systems. The output voltage is stabilized at a set value while the output voltage is isolated from the input voltage, and the output voltage is necessarily fed back to the input side by an isolating device for adjustment and control. FIG. 1 is a schematic diagram of a common secondary feedback control technique, in which the task of isolating feedback is carried out by an isolation amplifier composed of a device TL431, an optocoupler and an auxiliary device. The basic principle is as follows: the transconductance amplifier formed by TL431, sampling resistors R1, R2 and other elements amplifies an error voltage signal of an output voltage and a reference voltage into a current signal, when the output voltage is higher, the current flowing through TL431 is larger, namely the current flowing through an optocoupler is larger, the voltage of a controller FB port is smaller, so that the output duty ratio of a controller GATE port is smaller, a transformer transmits smaller energy to a secondary side output end, and the output voltage starts to be reduced; conversely, if the output voltage is lower, the transmission energy of the transformer is increased by feeding back an error signal to the increase of the primary control duty cycle, so that the output voltage is increased. The control is repeatedly and continuously adjusted to stabilize the output voltage at the set value. This feedback technique is referred to as secondary side feedback because its detection and comparison links are on the secondary side of the switching power supply, i.e., the load side. This way of directly detecting the output voltage has the characteristic of high precision, but it is obvious that there is no advantage in terms of cost and volume because the presence of these detection, amplifier, isolated feedback devices increases the space of the power supply system board. Particularly, the optocoupler cannot work at high temperature and is easy to age, so that the high-temperature service life of the power supply is short, and the power supply cannot meet certain high-temperature application occasions.
In order to solve the above-mentioned technical problems, the invention application with publication number CN 105610306A, entitled "secondary side feedback control method and control circuit thereof", proposes a novel secondary side feedback circuit, which is suitable for an isolated switching power supply having a primary side circuit formed by a primary side winding of a transformer and a secondary side circuit formed by a secondary side winding of the transformer. Fig. 2 is a diagram of fig. 6 from the fourth embodiment of the application, fig. 3 is a diagram of the operating state of the feedback switch of the circuit of fig. 2 and the voltage waveform at 124, and the secondary feedback switch power supply of fig. 2 includes: a three-winding transformer comprising three windings, a primary winding NP, a secondary winding NS, and an auxiliary winding NA, wherein winding NP comprises a first port 102 and a second port 103, winding NS comprises a first port 104 and a second port 105, and winding NA comprises a first port 106 and a second port 107. The secondary side modulator is composed of an output voltage coding control module and a detection judging module. A secondary side degaussing circuit comprising two ports, a first port 110 and a second port 111; an output capacitor comprising two ports, a first port 131 and a second port 132; a feedback switch comprising three ports, a drain port 133, a source port 135 and a gate port 134. An output voltage coding control module comprising three ports, a first port 112, a second port 113, and a third port 114; the detection judging module comprises five ports, namely a first port 115, a second port 116, a third port 117, a fourth port 118 and a fifth port 119; an auxiliary winding voltage sense upper resistor comprising a first port 120 and a second port 121; an auxiliary winding voltage sense resistor comprising a first port 122 and a second port 123; a feedback switch state detection module comprising a first port 124 and a second port 125; an output voltage decoding feedback module comprising two ports, a first port 126 and a second port 127; a duty cycle modulation circuit comprising three ports, a first port 128, a second port 129, and a third port 130.
The connection relation is as follows: port 102 is connected to positive terminal 101 of the input power, and port 103 is connected to port 130; port 104, port 131, port 119 are connected together, the connection point forming the positive port 108 of the switching power supply output voltage; port 105, port 110, drain port 133 of the feedback switch, port 115 are connected together; port 111, port 118, source port 135 of the feedback switch, port 132 are connected together, the connection point forming negative port 109 of the switching power supply output voltage; the gate port 134 of the feedback switch is connected with port 112; port 113 is connected to port 116; port 114 is connected to port 117; port 120 is connected to port 106; port 121, port 122, port 124 are connected together; port 125 is connected with port 126; port 127 is connected together with port 128; port 129, port 123, port 107 are connected together with the connection point forming the negative terminal of the input power source. The exciting process of the flyback power supply switching power supply is the same as that of the traditional flyback power supply switching power supply, and the difference is how to feed back the change information of the output voltage from the secondary side to the primary side in the demagnetizing stage. The specific working principle is shown in the 0086-0090 section of the related specification.
The feedback control simplification process of the scheme is as follows: the secondary side detection judging module samples output voltage, the output voltage coding control module codes, the control feedback switch resistance state change, the primary side feedback switch state detecting module detects the resistance state change of the feedback switch, the output voltage decoding feedback module decodes, and the duty ratio modulating circuit generates voltage modulation duty ratio. The scheme does not need an optocoupler device or other additional isolation transmission devices, so that not only are some inherent defects brought by the devices avoided, but also devices added for assisting the devices to work are avoided, the volume and cost can be reduced, the volume, the cost and the performance are optimized, and the application range is wider. Meanwhile, the problems that the output voltage of the primary side feedback technology is low in precision and the output voltage cannot be changed by control on the secondary side are solved.
However, the above scheme should ensure that the output voltage variation set point Δvvref is smaller than the voltage variation value Δv 124 detected at the port 124, that is, the feedback switch state detection module can determine the voltage abrupt change. If the power system outputs voltage V OUT =12v, voltage V 124 =3v detected at port 124, output voltage change set value Δv ref =0.1v, voltage V BE =0.4v between the base and the emitter of the feedback switch, and feedback switch conduction voltage drop V sdon =0.06V.
The formula is:
It can be derived that:
At this time, ΔV ref＞ΔV124 is caused. Therefore, when the output voltage is high, the feedback switch state detection module is difficult to detect whether the conduction state of the feedback switch is changed, and the output voltage decoding feedback module and the duty ratio modulation circuit cannot finish the decoding of the conduction state of the feedback switch and the adjustment of the duty ratio, so that the power supply system cannot work normally; in order to improve the highest voltage which can be processed by the feedback switch state detection module, a high-voltage resistant device needs to be added into the feedback switch state detection module, the high-voltage device can increase extra cost, and the high-voltage device also has certain voltage-resistant limit.
Disclosure of Invention
In view of the above, the present invention provides a secondary feedback control circuit suitable for high output voltage and a switching power supply using the same.
The technical scheme of the control circuit provided by the invention for solving the technical problems is as follows:
A control circuit for an isolated switching power supply having a primary circuit formed from a primary winding of a transformer and a secondary circuit formed from a secondary winding of the transformer, comprising: the detection judging module, the output voltage coding control module and the feedback switch are positioned on the secondary side; the auxiliary winding is positioned on the primary side, the auxiliary winding voltage detection upper resistor, the auxiliary winding voltage detection lower resistor, the feedback switch state detection module, the output voltage decoding feedback module and the duty ratio modulation circuit are arranged on the primary side;
The feedback switch is connected in parallel with a secondary side demagnetizing circuit of the isolating switch power supply; one end of the auxiliary winding is used for connecting with the negative electrode end of the input power supply of the isolating switch power supply, the other end of the auxiliary winding is connected with the negative electrode end of the input power supply of the isolating switch power supply after passing through an upper resistor for detecting the voltage of the auxiliary winding and a lower resistor for detecting the voltage of the auxiliary winding in sequence, and the connection point of the upper resistor for detecting the voltage of the auxiliary winding and the lower resistor for detecting the voltage of the auxiliary winding is a partial pressure sampling point;
The detection judging module detects the output voltage of the isolating switch power supply, compares the voltage with the internal reference voltage to generate output voltage change information, and sends the output voltage change information to the output voltage coding control module;
The output voltage coding control module codes according to the received voltage change information and the agreed communication protocol, and sends the codes to the control end of the feedback switch to control the working state of the feedback switch;
The feedback switch state detection module samples the voltage of the auxiliary winding through the voltage division of the upper resistor and the lower resistor of the voltage detection of the auxiliary winding at the appointed time of the degaussing stage of each switch period, compares the current detected voltage with the voltage detected before, obtains the change amplitude of the voltage and the change direction of the voltage, outputs the information of the change of the working state of the feedback switch, and sends the information to the output voltage decoding feedback module;
The output voltage decoding feedback module receives the information of the change of the working state of the feedback switch, decodes according to a contracted communication protocol, judges whether the output voltage is higher or lower, outputs a modulation voltage, and sends the modulation voltage to the duty ratio modulation circuit;
The duty ratio modulation circuit receives the modulation voltage and modulates the duty ratio according to the magnitude of the voltage, the duty ratio is increased when the modulation voltage is increased, and the duty ratio is decreased when the modulation voltage is decreased otherwise;
The method is characterized in that: the voltage of the divided sampling point is stabilized at a set value by adjusting the current of the divided sampling point extracted by the current source module, so that the voltage of the divided sampling point is not increased along with the increase of the output voltage of the isolating switch power supply.
Preferably, the feedback switch working state change information is that the increasing amplitude exceeds a set value, and the feedback switch is regarded as jumping from a low resistance state to a high resistance state; otherwise, if the change information of the working state of the feedback switch is that the reduced amplitude exceeds the set value, the working state of the feedback switch is regarded as jumping from the high-resistance state to the low-resistance state.
Preferably, the output voltage decoding feedback module decodes the output voltage in the period that the output voltage is higher, and gradually reduces the modulation voltage until the output voltage is lower; otherwise, if the decoding result in the present period is "the output voltage is low", the modulation voltage is gradually increased until "the output voltage of the switching power supply is high".
Preferably, the feedback switch is a MOS transistor.
Correspondingly, the invention also provides a switching power supply applying the control circuit, which is characterized in that: the duty cycle of the switching power supply main power switch tube is provided by a duty cycle modulation circuit.
The above related terms are explained as follows:
Secondary side demagnetizing circuit: the secondary side demagnetizing circuit provides a path for demagnetizing the transformer of the isolating switch power supply. The secondary side degaussing circuit is in a conducting state in a transformer degaussing stage, and provides a path for energy storage of the transformer to charge an output capacitor; and the transformer is in a high-resistance state in a non-demagnetizing stage, so that the charge of the output capacitor is prevented from flowing backwards.
Agreed communication protocol: the method is to number the sampled output voltage of the switching power supply according to a preset rule, and default the coding rule in the decoding process of the primary side, so as to judge whether the output voltage is higher or lower. The specific encoding and decoding process may be understood by a detailed explanation of the embodiments.
The contracted time of the degaussing stage: the secondary side feedback switch is defined to act at a certain moment or time period of the degaussing stage, and the primary side detection module senses the action for a preset time period to be considered effective.
The control end of the feedback switch: the port for controlling the on and off of the feedback switch, such as the grid electrode of the MOS tube; by triode, it is meant the base of the triode.
The on-current inflow end of the feedback switch: after the feedback switch is conducted, a port into which current flows, such as a drain electrode of the MOS tube, is referred to as an N channel, a P channel, an enhancement type or a depletion type MOS tube, and when the feedback switch is conducted, the current flows from the drain electrode with high voltage to the source electrode with low voltage; the triode is referred to as collector of the triode, and when conducting, current flows from collector with high voltage to emitter with low voltage.
The on-current outflow end of the feedback switch: after the feedback switch is conducted, a port from which current flows, such as a source electrode of the MOS tube, is referred to as the MOS tube; by triode is meant the emitter of the triode.
Conduction state: the feedback switch is driven by proper driving voltage to work in high-resistance state or low-resistance state, the high-resistance state and the low-resistance state are opposite rather than setting absolute limit, and the difference is only that whether the control voltage generated by the feedback switch is detected at the primary side and the change of the resistance state can be correctly judged.
In particular, in order to make it easier to understand the working principle of the present invention, the logic relationship in the encoding process in the embodiment is represented by a specific form, for example, the information that the "output voltage is higher" is represented by the "feedback switch is in a high-resistance state", and in the actual product implementation, the information that the "output voltage is higher" may also be carried by the "feedback switch is in a low-resistance state", which is only for better illustrating the present invention, not for limiting the present invention.
Compared with the prior art, the invention has the following beneficial effects:
(1) Compared with the traditional technical scheme that the auxiliary side control is realized by the isolation amplifier consisting of the TL431, the optocoupler and the auxiliary device, the application does not need the optocoupler device or other additional isolation transmission devices, thereby not only avoiding some inherent defects caused by the devices, but also avoiding devices added for assisting the devices to work, reducing volume and cost, optimizing volume, cost and performance, and having wider application range.
(2) Compared with the existing hotter primary side feedback technology, the problems that the output voltage of the primary side feedback technology is low in precision and the output voltage can not be changed by control on the secondary side are solved.
(3) The current source module is added, and the current of the divided sampling point is extracted by the current source module, so that the voltage of the divided sampling point is stabilized at a set value, and the voltage of the divided sampling point is not increased along with the increase of the output voltage of the isolating switch power supply. Using a voltage consistent with a low output voltage at a high output voltageThe voltage change value DeltaV 124 detected at port 124 still complies with the formula/>The voltage change value of the output voltage change set value DeltaV ref is ensured to be smaller than the voltage change value of the partial pressure sampling point, so that the power supply system stably works, the secondary side feedback control circuit with high output voltage is realized, and meanwhile, the feedback switch state detection module only needs to adopt a low-voltage device, and the cost of the power supply system can be reduced.
The relevant principle analysis is illustrated in the examples section with specific switching power supply designs and calculations.
Drawings
FIG. 1 is a schematic diagram of a typical circuit of a switching power supply employing a conventional secondary side feedback controller;
FIG. 2 is a schematic diagram of a novel switching power supply employing a secondary feedback control circuit;
FIG. 3 is a graph of the voltage waveform at node 124 for the circuit feedback switch of FIG. 2;
Fig. 4 is a schematic block diagram of a switching power supply to which the secondary side feedback control circuit of the first embodiment of the present invention is applied.
Detailed Description
In order that the invention may be more readily understood, a more particular description thereof will be rendered by reference to specific embodiments that are illustrated in the appended drawings. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
Example 1
As shown in fig. 4, a circuit diagram of the switching power supply of the present embodiment is a flyback converter, which includes: a three-winding transformer comprising three windings, primary winding NP, secondary winding NS, and auxiliary winding NA, wherein primary winding NP comprises a first port 102 and a second port 103, secondary winding NS comprises a first port 104 and a second port 105, and auxiliary winding NA comprises a first port 106 and a second port 107. The secondary side modulator consists of a pressurizing module and an output voltage coding control module, wherein the pressurizing module comprises a secondary side demagnetizing circuit and a feedback switch, the feedback switch is a pressurizer, and the secondary side demagnetizing circuit comprises a first port 110 and a second port 111; an output capacitor C OUT comprising two ports, a first port 131 and a second port 132; a feedback switch comprising three ports, a drain port 133, a source port 135 and a gate port 134. An output voltage coding control module comprising three ports, a first port 112, a second port 113, and a third port 114; the secondary side sampler adopts a detection judging module, and comprises five ports, namely a first port 115, a second port 116, a third port 117, a fourth port 118 and a fifth port 119; an auxiliary winding voltage sense upper resistor R FA1 comprising a first port 120 and a second port 121; an auxiliary winding voltage sense resistor R FA2 comprising a first port 122 and a second port 123; a current source module comprising a first port connected to port 133; a feedback switch state detection module comprising a first port 124 and a second port 125; an output voltage decoding feedback module comprising two ports, a first port 126 and a second port 127; a duty cycle modulation circuit comprising three ports, a first port 128, a second port 129, and a third port 130.
The connection relation is as follows: port 102 is connected to positive terminal 101 of the input power, and port 103 is connected to port 130; port 104, port 131, port 119 are connected together, the connection point forming the positive port 108 of the switching power supply output voltage; port 105, port 110, drain port 133 of the feedback switch, port 115 are connected together; port 111, port 118, source port 135 of the feedback switch, port 132 are connected together, the connection point forming negative port 109 of the switching power supply output voltage; port 113 is connected to port 116; port 114 is connected to port 117; port 120 is connected to port 106; port 121, port 122, port 124, port 133 are connected together; port 125 is connected with port 126; port 127 is connected together with port 128; port 129, port 123, port 107 are connected together with the connection point forming the negative terminal of the input power source.
It should be noted that, fig. 4 is a schematic block diagram, in the actual circuit design process, a main power switch tube of a switching power supply is connected between the port 103 and the port 130, and the port 130 is connected to a control end of the main power switch tube of the switching power supply, which is also the same as fig. 3.
In fig. 4, the feedback switch is a MOS transistor, so that the voltage drop at two ends of the secondary demagnetization circuit can be reduced by using the low-resistance characteristic of the MOS transistor when the MOS transistor is turned on; and the voltage drop at the two ends of the secondary side demagnetizing circuit is increased by utilizing the high-resistance characteristic when the MOS tube is not opened.
The exciting process of the flyback power converter is the same as that of a conventional flyback converter, and the difference is how to feed back the change information of the output voltage from the secondary side to the primary side in the demagnetizing stage. The specific working principle is as follows:
The secondary side degaussing circuit acts as: in a conducting state in a transformer degaussing stage, a path is provided for charging an output capacitor C OUT by energy storage of the transformer; the transformer is in a high-resistance state in a non-demagnetizing stage, and the charge of the output capacitor C OUT is prevented from flowing backwards.
Two detection functions of the detection judging module: first, the output voltage of the switching power supply is detected through the port 119, and the voltage is compared with the internal reference voltage, and the comparison result can determine whether the feedback switching MOS transistor is turned on in the transformer degaussing stage. If the output voltage of the switching power supply is lower than the internal reference voltage through the port 119, the feedback switch MOS tube is turned on in the transformer degaussing stage; if the output voltage of the switching power supply is detected to be higher than the internal reference voltage through the port 119, the feedback switch MOS transistor is not turned on in the transformer degaussing stage; second, the conduction voltage drop of the degaussing path is detected through the 110 port and the 111 port, and the voltage drop of the port 110 is smaller than that of the port 111 in the degaussing stage, so that the power supply system is judged to be in the degaussing stage.
Two functions of the output voltage coding control module: first, the coding effect is agreed with coding rules, namely when the output voltage changes from a higher state to a lower state, the feedback switch needs to change from a high resistance state to a low resistance state, otherwise, when the output voltage changes from the lower state to the higher state, the feedback switch needs to change from the low resistance state to the high resistance state. Then, when the output voltage is higher, the feedback switch is in a high resistance state, and the driving level of the feedback switch is coded as a low level; when the output voltage is low, the feedback switch should be in a low resistance state, and the feedback switch driving level is coded as a high level. Second, the control function controls the feedback switch gate to be at the corresponding coding level in the degaussing stage, that is, the port 112 outputs a low level when the output voltage is higher, and the port 112 outputs a high level when the output voltage is lower.
The preferred encoding rules are: the feedback switch working state change information is that the increasing amplitude exceeds a set value, and the feedback switch is considered to jump from a low resistance state to a high resistance state; otherwise, if the change information of the working state of the feedback switch is that the reduced amplitude exceeds the set value, the working state of the feedback switch is regarded as jumping from the high-resistance state to the low-resistance state.
The reason for selecting the above coding rule is that: in a general flyback circuit, when the output voltage is higher, the modulation voltage is gradually reduced, and the output voltage starts to drop to a set value; when the output voltage is lower, the modulation voltage is gradually increased, and the output voltage starts to rise to the set value. By adjusting the modulation voltage, the output voltage of the power supply system can be maintained stable.
The transmission process of the transformer comprises the following steps: because the output capacitor C OUT has the energy storage function, the output voltage of the converter cannot be greatly suddenly changed in one or even a few periods, so that the change of the voltage V OUT of the capacitor C OUT can be ignored in a short time. According to the present invention, it is now necessary to superimpose a control voltage on V OUT, for which purpose we use rectifier diodes as secondary degaussing paths, as shown in fig. 4, which is the simplest and most common way. Because of the junction voltage drop V BE of the diode, when the feedback switch MOS tube is not opened in the degaussing stage, the minimum value of the pressure difference between the port 104 and the port 105 of the secondary winding N S is (V OUT+VBE); when the feedback switch MOS tube is opened in the degaussing stage, the pressure difference value between the port 104 and the port 105 of the secondary winding N S is (V OUT+Vsdon), wherein V sdon is the pressure difference between the source electrode and the drain electrode when the feedback switch MOS tube is conducted, and because the internal resistance of the feedback switch MOS tube is small, V sdon is smaller than V BE. Therefore, the voltage difference between the two ends of the winding is greatly changed due to the conduction and non-conduction of the feedback switch MOS tube in the degaussing stage, and the voltage change at the port 124 of the feedback switch state detection module is as follows: Wherein/> Is the ratio of the number of windings NA to NS.
And the detection and judgment process of the feedback switch state detection module comprises the following steps: in order to make the transmission more intuitive, a power converter is specifically designed for illustration. Selecting V BE =0.4v, the feedback switch MOS transistor turns on the voltage drop V sdon =0.06V, Then the feedback MOS switch is on and off and the voltage change detected at port 124 is Δv 124 = (0.4V-0.06V) ×3×0.2=0.2V. If the voltage obtained in the current period is higher than the voltage in the previous period by the output voltage change set value Δvref=0.1v, the voltage of the detection port 124 in each period can determine that the feedback switch is changed from the low resistance region to the high resistance region; otherwise, it can be judged that the feedback switch is changed from the high-resistance region to the low-resistance region. In order to make this determination correct, it is ensured by the following two requirements, firstly ΔVref < ΔV 124, i.e. the detection module is able to determine this voltage jump; the second is that the compared voltage cannot be excessively large in the number of periods of the interval, because the change of the voltage of V OUT can be ignored only in a short time, and erroneous judgment caused by the larger change of V OUT is avoided.
If V OUT = 12V, The voltage of V 124 reaches 7.2V, and the highest voltage which can be processed by the feedback switch state detection module is 4V. In order to improve the highest voltage which can be processed by the feedback switch state detection module, a high-voltage resistant device needs to be added into the feedback switch state detection module, the high-voltage device can increase extra cost, and the high-voltage device also has certain voltage-resistant limit.
V 124 increases with V OUT, and a common means for those skilled in the art is to add a higher voltage resistant device to the feedback switch status detection module; the inventors have abandoned conventional solutions and sought breakthrough by adding a current source module at node 124, ensuring that V 124 =3v at an output voltage V OUT =12v or higher, with the following specific calculation formula:
is available in the form of
The value R FA1＝40K,RFA2＝10K,VBE =0.4v, V OUT＝12V,V124 = 3V, calculated as I = 0.555mA. For higher output voltage V OUT, set/> V 124 = 3V. Through the calculation formula, the current I at the position of the current source module extraction 124 is calculated, the DeltaVref is ensured to be smaller than DeltaV 124, and the secondary feedback control circuit which is applicable to high output voltage, namely the switching power supply of the application switching circuit, is realized.
Under high output voltage, the feedback switch state detection module can detect whether the conducting state of the feedback switch is changed, and the decoding and duty ratio modulation module finishes decoding of the conducting state of the feedback switch and adjustment of the duty ratio, so that the normal work of the power supply system is realized.
Decoding and duty cycle modulation process: according to the coding rule agreed in the coding process, the decoding rule should be agreed that when the judgment result of the feedback switch changing from the high-resistance state to the low-resistance state is received, the output voltage is correspondingly decoded to change from the higher state to the lower state, whereas when the judgment result of the feedback switch changing from the low-resistance state to the high-resistance state is received, the output voltage is correspondingly decoded to change from the lower state to the higher state. If the decoding result is that the output voltage is changed from a higher state to a lower state, the output voltage is higher before the change, and the current output voltage is lower until the opposite state change is received again; conversely, it can be known that the current output voltage is high. It can be seen that the magnitude of the secondary output voltage of the isolation transformer can be fed back to its primary side as long as control and transmission is performed in accordance with the communication protocol constituted by these two conventions. Gradually reducing the modulation voltage when the output voltage is higher, wherein the modulation voltage controls the duty ratio to gradually reduce, so that the output voltage is reduced; conversely, when the output voltage is lower, the duty ratio is gradually increased so as to rise again. The above steps are repeated to stabilize the output voltage at the set value.
The preferred decoding and duty cycle modulation schemes are: the output voltage decoding feedback module decodes the output voltage in the period to be higher, and gradually reduces the modulation voltage until the output voltage is lower; otherwise, if the decoding result in the present period is "the output voltage is low", the modulation voltage is gradually increased until "the output voltage of the switching power supply is high".
The reason for selecting the decoding and duty cycle modulation scheme is that: in a general flyback circuit, when the output voltage is higher, the modulation voltage is gradually reduced, and the output voltage starts to drop to a set value; when the output voltage is lower, the modulation voltage is gradually increased, and the output voltage starts to rise to the set value. By adjusting the modulation voltage, the output voltage of the power supply system can be maintained stable.
The foregoing is merely a preferred embodiment of the present invention, and it should be noted that the above-mentioned preferred embodiment should not be construed as limiting the invention, and the scope of the invention should be defined by the appended claims. It will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the spirit and scope of the invention, and such modifications and adaptations are intended to be comprehended within the scope of the invention.
Claims (5)
1. A control circuit for an isolated switching power supply having a primary circuit formed from a primary winding of a transformer and a secondary circuit formed from a secondary winding of the transformer, comprising: the detection judging module, the output voltage coding control module and the feedback switch are positioned on the secondary side; the auxiliary winding is positioned on the primary side, the auxiliary winding voltage detection upper resistor, the auxiliary winding voltage detection lower resistor, the feedback switch state detection module, the output voltage decoding feedback module and the duty ratio modulation circuit are arranged on the primary side;
The feedback switch is connected in parallel with a secondary side demagnetizing circuit of the isolating switch power supply; one end of the auxiliary winding is used for connecting with the negative electrode end of the input power supply of the isolating switch power supply, the other end of the auxiliary winding is connected with the negative electrode end of the input power supply of the isolating switch power supply after passing through an upper resistor for detecting the voltage of the auxiliary winding and a lower resistor for detecting the voltage of the auxiliary winding in sequence, and the connection point of the upper resistor for detecting the voltage of the auxiliary winding and the lower resistor for detecting the voltage of the auxiliary winding is a partial pressure sampling point;
The detection judging module detects the output voltage of the isolating switch power supply, compares the voltage with the internal reference voltage to generate output voltage change information, and sends the output voltage change information to the output voltage coding control module;
The output voltage coding control module codes according to the received voltage change information and the agreed communication protocol, and sends the codes to the control end of the feedback switch to control the working state of the feedback switch;
The feedback switch state detection module samples the voltage of the auxiliary winding through the voltage division of the upper resistor and the lower resistor of the voltage detection of the auxiliary winding at the appointed time of the degaussing stage of each switch period, compares the current detected voltage with the voltage detected before, obtains the change amplitude of the voltage and the change direction of the voltage, outputs the information of the change of the working state of the feedback switch, and sends the information to the output voltage decoding feedback module;
The output voltage decoding feedback module receives the information of the change of the working state of the feedback switch, decodes according to a contracted communication protocol, judges whether the output voltage is higher or lower, outputs a modulation voltage, and sends the modulation voltage to the duty ratio modulation circuit;
The duty ratio modulation circuit receives the modulation voltage and modulates the duty ratio according to the magnitude of the voltage, the duty ratio is increased when the modulation voltage is increased, and the duty ratio is decreased when the modulation voltage is decreased otherwise;
The method is characterized in that: the voltage of the divided sampling point is stabilized at a set value by adjusting the current of the divided sampling point extracted by the current source module, so that the voltage of the divided sampling point is not increased along with the increase of the output voltage of the isolating switch power supply.
2. The control circuit of claim 1, wherein: the feedback switch working state change information is that the increasing amplitude exceeds a set value, and the feedback switch is considered to jump from a low resistance state to a high resistance state; otherwise, if the change information of the working state of the feedback switch is that the reduced amplitude exceeds the set value, the working state of the feedback switch is regarded as jumping from the high-resistance state to the low-resistance state.
3. The control circuit of claim 1, wherein: the output voltage decoding feedback module decodes the output voltage in the period to be higher, and gradually reduces the modulation voltage until the output voltage is lower; otherwise, if the decoding result in the present period is "the output voltage is low", the modulation voltage is gradually increased until "the output voltage of the switching power supply is high".
4. The control circuit of claim 1, wherein: the feedback switch is a MOS tube.
5. A switching power supply employing the control circuit of any one of claims 1 to 4, characterized in that: the duty cycle of the switching power supply main power switch tube is provided by a duty cycle modulation circuit.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810888306.3A CN109039085B (en) | 2018-08-07 | 2018-08-07 | Control circuit and switching power supply using same |
| PCT/CN2019/084987 WO2020029614A1 (en) | 2018-08-07 | 2019-04-29 | Control circuit and switched-mode power supply using circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810888306.3A CN109039085B (en) | 2018-08-07 | 2018-08-07 | Control circuit and switching power supply using same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN109039085A CN109039085A (en) | 2018-12-18 |
| CN109039085B true CN109039085B (en) | 2024-05-17 |
Family
ID=64649866
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201810888306.3A Active CN109039085B (en) | 2018-08-07 | 2018-08-07 | Control circuit and switching power supply using same |
Country Status (2)
| Country | Link |
|---|---|
| CN (1) | CN109039085B (en) |
| WO (1) | WO2020029614A1 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109039085B (en) * | 2018-08-07 | 2024-05-17 | 广州金升阳科技有限公司 | Control circuit and switching power supply using same |
| CN109831107B (en) * | 2019-02-28 | 2021-06-22 | 华为技术有限公司 | Power conversion device and method for controlling output impedance of power conversion device |
| CN110212777A (en) * | 2019-06-19 | 2019-09-06 | 杰华特微电子（杭州）有限公司 | The control circuit and control method for cascading circuit of reversed excitation, cascading circuit of reversed excitation |
| CN116488433B (en) * | 2023-06-21 | 2023-09-12 | 成都智融微电子有限公司 | Auxiliary power supply circuit of switching power supply and control method thereof |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102832806A (en) * | 2012-09-14 | 2012-12-19 | 成都芯源***有限公司 | Switch voltage stabilizing circuit and voltage feedback method thereof |
| CN103746566A (en) * | 2014-01-21 | 2014-04-23 | 成都芯源***有限公司 | Primary side controlled switching power supply and control method thereof |
| CN105099203A (en) * | 2015-07-24 | 2015-11-25 | 矽力杰半导体技术(杭州)有限公司 | Voltage sampling control circuit, voltage sampling control method and isolated converter |
| CN105610306A (en) * | 2016-03-01 | 2016-05-25 | 深圳南云微电子有限公司 | Secondary feedback control method and secondary feedback control circuit |
| CN208571931U (en) * | 2018-08-07 | 2019-03-01 | 广州金升阳科技有限公司 | A kind of control circuit and the Switching Power Supply using the circuit |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN2783627Y (en) * | 2004-11-29 | 2006-05-24 | 崇贸科技股份有限公司 | Switching type controller |
| US8125799B2 (en) * | 2009-10-23 | 2012-02-28 | Bcd Semiconductor Manufacturing Limited | Control circuits and methods for switching mode power supplies |
| CN102055341B (en) * | 2009-10-29 | 2014-02-05 | Bcd半导体制造有限公司 | Control circuit of switching power supply and switching power supply |
| CN105471270A (en) * | 2016-01-22 | 2016-04-06 | 矽力杰半导体技术(杭州)有限公司 | Control circuit and control method with self-adaptive blanking time |
| CN109039085B (en) * | 2018-08-07 | 2024-05-17 | 广州金升阳科技有限公司 | Control circuit and switching power supply using same |
-
2018
- 2018-08-07 CN CN201810888306.3A patent/CN109039085B/en active Active
-
2019
- 2019-04-29 WO PCT/CN2019/084987 patent/WO2020029614A1/en active Application Filing
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102832806A (en) * | 2012-09-14 | 2012-12-19 | 成都芯源***有限公司 | Switch voltage stabilizing circuit and voltage feedback method thereof |
| CN103746566A (en) * | 2014-01-21 | 2014-04-23 | 成都芯源***有限公司 | Primary side controlled switching power supply and control method thereof |
| CN105099203A (en) * | 2015-07-24 | 2015-11-25 | 矽力杰半导体技术(杭州)有限公司 | Voltage sampling control circuit, voltage sampling control method and isolated converter |
| CN105610306A (en) * | 2016-03-01 | 2016-05-25 | 深圳南云微电子有限公司 | Secondary feedback control method and secondary feedback control circuit |
| CN208571931U (en) * | 2018-08-07 | 2019-03-01 | 广州金升阳科技有限公司 | A kind of control circuit and the Switching Power Supply using the circuit |
Also Published As
| Publication number | Publication date |
|---|---|
| WO2020029614A1 (en) | 2020-02-13 |
| CN109039085A (en) | 2018-12-18 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN109039085B (en) | Control circuit and switching power supply using same | |
| US11527960B2 (en) | Auxiliary power supply apparatus and method for isolated power converters | |
| CN105610306B (en) | Secondary side feedback control method and its control circuit | |
| US20180159437A1 (en) | Control method and control apparatus for flyback circuit | |
| US10003271B2 (en) | Systems and methods for constant voltage control and constant current control | |
| US8064229B2 (en) | Method of forming a series resonant switching power supply control circuit and structure therefor | |
| JP4613100B2 (en) | Method and apparatus for extending the operating range of a fly forward converter | |
| CN104967317B (en) | Power switch converter | |
| CN103944374A (en) | PFC constant-voltage driving control circuit for primary side feedback and control method | |
| US20150303816A1 (en) | Power switching converter | |
| JP2009273329A (en) | Switching power supply unit | |
| US9083259B2 (en) | Bridgeless power factor correction circuit with improved critical mode (CRM) operation | |
| CN1905341A (en) | Power overload detection method and structure therefor | |
| TW201005461A (en) | Voltage regulator and control method thereof | |
| WO2019019814A1 (en) | Secondary side feedback control circuit and switching power supply using the same | |
| JP2009284667A (en) | Power supply device, its control method, and semiconductor device | |
| TW201429133A (en) | Switching power conversion device | |
| US7457138B2 (en) | Single pin multi-function signal detection method and structure therefor | |
| US20110013424A1 (en) | Forward converter with secondary side post-regulation and zero voltage switching | |
| US20090231883A1 (en) | Dc-dc converter | |
| CN114759809A (en) | Switching power supply and method for use in a switching power supply | |
| CN208571931U (en) | A kind of control circuit and the Switching Power Supply using the circuit | |
| CN207069913U (en) | The Switching Power Supply of secondary side feedback control circuit and the application circuit | |
| CN103066847B (en) | Supply unit and image forming apparatus | |
| US9077256B2 (en) | Method of forming a low power dissipation regulator and structure therefor |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |