DCDC power supply synchronous rectification and closed-loop control circuit

Abstract

The invention relates to a DCDC power supply synchronous rectification and closed-loop control circuit, belongs to the technical field of switching power supplies, and solves the problems of low output voltage precision, complex control logic and high cost of an output branch in an existing DCDC power supply control circuit. Comprising an input module which is used for performing power conversion on an input DC voltage and then transmitting the converted DC voltage to the transformer; the transformer is used for converting the received converted voltage into energy through the primary winding and transmitting the energy to each secondary winding; the main closed-loop output branch is used for rectifying and filtering the received energy transmitted by the corresponding secondary winding, then carrying out direct-current voltage-stabilizing output, and carrying out driving control on the input module based on the output voltage to realize closed-loop control of the voltage; and the non-main closed-loop output branch is used for rectifying and filtering the received energy transmitted by the corresponding secondary winding, then carrying out direct-current voltage-stabilizing output, and carrying out synchronous rectification and closed-loop control on the self non-main closed-loop output branch based on the output voltage.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of switching power supply, in particular to a DCDC power supply synchronous rectification and closed-loop control circuit. BACKGROUND

[0002] The multi-output flyback DCDC power supply is widely used in electrical equipment requiring multi-output power supply due to its small size, simple structure and low cost. However, the traditional multi-output flyback DCDC power supply can only control the output voltage of one output port in a closed loop, and the output voltages of the other ports are set by the turns ratio of the transformer. Therefore, the output voltages of the other ports are not accurate, especially in applications with low input voltage and few turns of the transformer. In addition, the multi-output flyback switching power supply also has the problem of cross-regulation between multiple outputs, which further affects the accuracy of the output voltage and may cause damage to the downstream equipment. Moreover, the traditional multi-output flyback DCDC power supply usually uses diode rectification, and the forward voltage drop of ordinary diodes is generally 0.7-1.0V. Even if a Schottky diode is used, the forward voltage drop cannot be controlled below 0.3V. The diode conduction loss accounts for a large proportion of the total loss, which seriously affects the efficiency and reliability of the power supply.

[0003] A traditional multi-output flyback circuit is shown in FIG. 1, which uses diode rectification on the secondary side, resulting in high diode operating loss and low system efficiency. In terms of control, a certain branch is usually controlled in a closed loop to ensure the accuracy of the output voltage of that branch, while the other branches are in an open loop state, resulting in low output voltage accuracy, especially when the loads are inconsistent. The output voltages of these branches vary greatly, and the load regulation rate does not meet the requirements. Figure 1 Another traditional multi-output flyback circuit based on synchronous rectification is shown in FIG. 2, which uses MOSFET instead of traditional diodes for rectification to improve the efficiency of the system. However, it uses a dedicated synchronous rectification chip to drive the synchronous rectification tubes of each branch, which requires special attention to timing control and is costly. At the same time, its closed-loop control strategy is consistent with that of FIG. 1, and only one branch is controlled in a closed loop, resulting in poor output voltage accuracy and load regulation rate for the other branches. Figure 2 In addition, there is another weighted closed-loop control strategy suitable for multi-output, as shown in FIG. 3. Figure 1 Figure 3 ​As shown, the working principle is to connect the multi-output voltage to each other after connecting the resistors in series, and then send it into the closed loop for modulation. By changing the size of the series resistance, the weight of each input voltage can be changed, so as to realize the balance of the precision of each output voltage. However, in this way, the smaller the weight of the branch, the lower the voltage precision, so this method can only realize the relative balance of the output voltage precision of each output branch, and cannot guarantee the high precision of each output.

[0004] Therefore, the output voltage precision of the output branch in the existing DCDC power supply control circuit is not high, the control logic is complex, and the cost is high. SUMMARY

[0005] In view of the above analysis, the embodiments of the present application aim to provide a DCDC power supply synchronous rectification and closed loop control circuit to solve the problem of low output voltage precision of the output branch in the existing DCDC power supply control circuit, complex control logic and high cost.

[0006] The embodiments of the present application provide a DCDC power supply synchronous rectification and closed loop control circuit, comprising an input module, a transformer, a main closed loop output branch, and at least one non-main closed loop output branch.

[0007] The input module is used to transmit the input DC voltage to the transformer after power conversion.

[0008] The transformer is used to convert the received converted voltage into energy through the primary winding and transmit it to each secondary winding. Each secondary winding is connected to the main closed loop output branch and each non-main closed loop output branch.

[0009] The main closed loop output branch is used to rectify and filter the energy transmitted by the corresponding secondary winding, and then output DC voltage. Based on the output voltage, the input module is driven and controlled to realize closed loop control of the voltage.

[0010] The non-main closed loop output branch is used to rectify and filter the energy transmitted by the corresponding secondary winding, and then output DC voltage. Based on the output voltage, the non-main closed loop output branch is synchronized and controlled.

[0011] Further, the non-main closed loop output branch is synchronized and controlled by the synchronous rectification and closed loop control circuit. The synchronous rectification and closed loop control circuit comprises a first control module, a second control module and a branch control module.

[0012] The first control module is used to sample the output voltage of the non-main closed loop output branch, and generate a first PWM control signal based on the sampled voltage.

[0013] The second control module is provided with an auxiliary winding, and a voltage control signal is generated based on the auxiliary winding;

[0014] The branch control module generates a branch control signal based on the first PWM control signal and the voltage control signal, and drives and controls the non-main closed-loop output branch through the branch control signal.

[0015] Further, the branch control module generates the branch control signal in the following manner:

[0016] If the voltage control signal is a high-level signal and the first PWM control signal is a high-level signal, the branch control signal is a high-level signal; otherwise, the branch control signal is a low-level signal.

[0017] Wherein, when the branch control signal is a high-level signal, the non-main closed-loop output branch conducts and outputs a voltage; otherwise, the non-main closed-loop output branch does not conduct.

[0018] Further, the number of turns n of the auxiliary winding C is represented as:

[0019]

[0020] In the formula, n A , n B are the number of turns of the primary winding of the transformer and the corresponding secondary winding of the non-main closed-loop output branch, respectively, V in , V O are the input voltage of the input module and the output voltage of the non-main closed-loop output branch, respectively.

[0021] Further, the main closed-loop output branch drives and controls the input module in the following manner:

[0022] The output voltage of the main closed-loop output branch is sampled, and the sampled voltage is compensated;

[0023] After the compensated voltage is isolated and transmitted, a second PWM control signal is generated by a PWM controller;

[0024] After power amplification of the second PWM control signal, a first input control signal and a second input control signal are generated and output to the input module for driving control.

[0025] Further, the first control module includes first, second, third, fourth, fifth, sixth, seventh and tenth resistors, a PWM control chip, second and third capacitors, and a triode.

[0026] The first resistor and the fifth resistor are connected in series between the positive pole and the negative pole of the output voltage of the non-closed loop output branch, and the first resistor is connected with the positive pole of the voltage; one end of the third resistor is connected with the connection end of the first resistor and the fifth resistor, and the other end is connected with the inverting input terminal of the error amplifier of the PWM control chip through the second capacitor and the second resistor, and the other end of the third resistor is also connected with the reference voltage terminal of the error amplifier of the PWM control chip;

[0027] One end of the sixth resistor is connected with the negative pole of the output voltage of the non-closed loop output branch, and the other end is connected with the input terminal of the current comparator of the PWM control chip, and the other end of the sixth resistor is also connected with the emitter of the transistor through the tenth resistor; the collector of the transistor is connected with the base through the seventh resistor, and the collector is also connected with the chip reference voltage terminal of the PWM control chip; the base of the transistor is also connected with the oscillation timing terminal of the PWM control chip and one end of the third capacitor; the other end of the third capacitor is connected with the negative pole of the output voltage of the non-closed loop output branch;

[0028] The power supply terminal of the PWM control chip is connected with the positive pole of the output voltage of the non-closed loop output branch, the grounding terminal is connected with the negative pole of the output voltage of the non-closed loop output branch, and the output terminal outputs the first PWM control signal through the fourth resistor.

[0029] Further, the second control module comprises an auxiliary winding, an eighth resistor and a ninth resistor;

[0030] The same name end of the auxiliary winding is connected with one end of the eighth resistor, and the other end outputs a voltage control signal, and the other end of the eighth resistor is also connected with the different name end of the auxiliary winding through the ninth resistor; the different name end of the auxiliary winding is also connected with the negative pole of the output voltage of the non-closed loop output branch.

[0031] Further, the branch control module comprises a stabilizing diode; the negative pole of the stabilizing diode receives the first PWM control signal, and the positive pole receives the voltage control signal, and the positive pole of the stabilizing diode also outputs a branch control signal.

[0032] Further, the non-main closed loop output branch outputs direct current voltage stabilization through a secondary output branch; the secondary output branch comprises a first NMOS tube and a first capacitor;

[0033] One end of the first capacitor is connected with the same name end of the corresponding auxiliary winding of the non-main closed loop output branch, and also serves as the positive pole of the output voltage of the non-main closed loop output branch; the other end of the first capacitor is grounded, and also serves as the negative pole of the output voltage of the non-main closed loop output branch;

[0034] The source of the first NMOS tube is connected with the other end of the first capacitor, the drain is connected with the opposite end of the corresponding secondary winding of the non-main closed loop output branch, and the gate receives a branch control signal.

[0035] Further, the main closed loop output branch is outputted by a main output branch in direct current voltage stabilization; the main output branch comprises a third diode and a fourth capacitor;

[0036] One end of the fourth capacitor is connected with the negative electrode of the third diode, and also serves as the positive electrode of the output voltage of the main closed loop output branch; the positive electrode of the third diode is connected with the same end of the corresponding secondary winding of the main closed loop output branch;

[0037] The other end of the fourth capacitor is connected with the opposite end of the corresponding secondary winding of the main closed loop output branch, and the other end of the fourth capacitor is grounded, and also serves as the negative electrode of the output voltage of the main closed loop output branch.

[0038] Compared with the prior art, the present application can achieve at least one of the following beneficial effects:

[0039] The DCDC power supply synchronous rectification and closed loop control circuit provided by the present application comprises an input module, a transformer, a main closed loop output branch and a non-main closed loop output branch; the input module is used for transmitting the input direct current voltage to the transformer after power conversion; the transformer is used for transmitting the energy converted by the primary winding to each secondary winding; the main closed loop output branch is used for outputting the energy transmitted by the corresponding secondary winding in direct current voltage stabilization after rectification and filtering, and driving and controlling the input module based on the output voltage, so as to realize the closed loop control of the voltage; the non-main closed loop output branch is used for outputting the energy transmitted by the corresponding secondary winding in direct current voltage stabilization after rectification and filtering, and performing synchronous rectification and closed loop control on the non-main closed loop output branch based on the output voltage, so as to be suitable for synchronous rectification and closed loop control of other output branches except the main closed loop output branch in the DCDC power supply, and to ensure the high working efficiency of the power supply in the multi-output state, and to ensure the accuracy of the output voltage of the controlled branch; the synchronous rectification and closed loop control circuit can realize the dual functions of synchronous rectification and closed loop control by coupling between the auxiliary winding and the common PWM controller on the market, without complex logic timing control and peripheral circuit design, so the cost is low and the implementation is easy.

[0040] The technical solutions described above can be combined with each other in the present application to realize more preferred combination solutions. Other features and advantages of the present application will be described in the subsequent description, and some advantages will become apparent from the description, or will be understood by implementing the present application. The purposes and other advantages of the present application can be realized and obtained from the contents specifically indicated in the description and the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0041] The accompanying drawings are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and are not intended to limit the scope of the application, and together with the description serve to explain the principles of the application.

[0042] Figure 1 A schematic diagram of a conventional multi-output flyback circuit;

[0043] Figure 2 A schematic diagram of a multi-output flyback circuit based on synchronous rectification;

[0044] Figure 3 A schematic diagram of a conventional weighted closed-loop suitable for multi-output;

[0045] Figure 4 A principle block diagram of a DCDC power supply synchronous rectification and closed-loop control circuit provided by Embodiment 1 of the application;

[0046] Figure 5 A circuit connection schematic diagram of a DCDC power supply synchronous rectification and closed-loop control circuit provided by Embodiment 2 of the application. DETAILED DESCRIPTION

[0047] The preferred embodiments of the application will be described in detail below with reference to the drawings, wherein the drawings constitute a part of this application and serve to explain the principles of the embodiments of the application, but are not intended to limit the scope of the application.

[0048] Embodiment 1

[0049] One specific embodiment of the application discloses a DCDC power supply synchronous rectification and closed-loop control circuit, as shown in the figure, comprising an input module, a transformer, a main closed-loop output branch, and at least one non-main closed-loop output branch. Figure 4

[0050] The input module is configured to transmit the input DC voltage to the transformer after power conversion.

[0051] The transformer is configured to transmit the received converted voltage to each secondary winding after conversion by the primary winding.

[0052] The main closed-loop output branch is configured to perform DC voltage stabilization output after rectification and filtering of the energy transmitted by the corresponding secondary winding, and to drive and control the input module based on the output voltage to realize closed-loop control of the voltage.

[0053] The non-main closed-loop output branch is configured to perform DC voltage stabilization output after rectification and filtering of the energy transmitted by the corresponding secondary winding, and to perform synchronous rectification and closed-loop control of the non-main closed-loop output branch based on the output voltage. ​

[0054] In implementation, the main closed-loop output branch drives and controls the input module in the following way:

[0055] The output voltage of the main closed-loop output branch is sampled and the sampled voltage is compensated;

[0056] After the compensated voltage is isolated and transmitted, a second PWM control signal is generated by the PWM controller;

[0057] After the second PWM control signal is power amplified, a first input control signal and a second input control signal are generated and output to the input module for driving control.

[0058] In specific implementation, the input module includes a second NMOS tube, a third NMOS tube, a first diode, and a second diode;

[0059] The drain of the second NMOS tube is connected to the positive pole of the high-voltage DC power supply, the gate receives the first input control signal output by the main closed-loop output branch, and the source is connected to the opposite-phase end of the primary winding of the transformer;

[0060] The drain of the third NMOS tube is connected to the same-phase end of the primary winding of the transformer, the gate receives the second input control signal output by the main closed-loop output branch, and the source is connected to the negative pole of the high-voltage DC power supply;

[0061] The anode of the first diode is connected to the drain of the third NMOS tube, and the cathode is connected to the drain of the second NMOS tube; the anode of the second diode is connected to the source of the third NMOS tube, and the cathode is connected to the source of the second NMOS tube.

[0062] It can be understood that the input module accesses the high-voltage DC power supply, and through the common power conversion of the second NMOS tube and the third NMOS, the first diode and the second diode, and the primary winding of the transformer, the DC power is "chopped" into high-frequency switching components for energy storage.

[0063] In specific implementation, the main closed-loop output branch outputs DC voltage stabilization through a main output branch; the main output branch includes a third diode and a fourth capacitor;

[0064] One end of the fourth capacitor is connected to the negative pole of the third diode and also serves as the positive pole of the output voltage of the main closed-loop output branch; the positive pole of the third diode is connected to the same-phase end of the corresponding secondary winding of the main closed-loop output branch;

[0065] The other end of the fourth capacitor is connected to the opposite-phase end of the corresponding secondary winding of the main closed-loop output branch, and the other end of the fourth capacitor is grounded and also serves as the negative pole of the output voltage of the main closed-loop output branch.

[0066] It can be understood that the corresponding secondary winding of the main closed loop output branch will transmit energy after isolation, and then rectify and convert through the third diode and filter the direct current pulse through the fourth capacitor to output the direct current voltage.

[0067] In the embodiment, the main closed loop output branch drives and controls the input module through the control module; the control module comprises eleventh, twelfth, thirteenth and fourteenth resistors, fifth and sixth capacitors, a three-terminal voltage regulator, an optocoupler, a PWM controller, and a driver.

[0068] One end of the eleventh resistor and the twelfth resistor is connected to the positive pole of the output voltage of the main closed loop output branch; the other end of the twelfth resistor is connected to the cathode of the optocoupler through the fifth capacitor, and the other end is also connected to the cathode of the optocoupler through the series connection of the thirteenth resistor and the sixth capacitor; the other end of the twelfth resistor is also connected to the negative pole of the output voltage of the main closed loop output branch through the fourteenth resistor, and the other end is also connected to the adjusting end of the three-terminal voltage regulator; the positive pole of the three-terminal voltage regulator is connected to the negative pole of the output voltage of the main closed loop output branch, and the negative pole is connected to the cathode of the optocoupler.

[0069] The anode of the optocoupler is connected to the other end of the eleventh resistor, the emitter is connected to the negative pole of the high-voltage direct current power supply input by the input module, and the collector is connected to the input end of the PWM controller; the output end of the PWM controller is connected to the input end of the driver; the first output end of the driver outputs the first input control signal, and the second output end outputs the second input control signal.

[0070] It can be understood that the output voltage of the main closed loop output branch is sampled and sent to the three-terminal voltage regulator for compensation, and then sent to the PWM controller through the optocoupler isolation transmission to generate the second PWM control signal, and then the power amplifier is performed through the driver to drive the second NMOS tube and the third NMOS tube in the input module, so as to control the output voltage value of the main closed loop output branch, and realize the closed loop control of the main closed loop output branch. In addition, in the embodiment, the second NMOS tube and the third NMOS tube work in series to realize "voltage sharing", which can reduce the voltage stress of the second NMOS tube and the third NMOS tube, and ensure the reliability of the device.

[0071] In the embodiment, the non-main closed loop output branch is subjected to synchronous rectification and closed loop control through the synchronous rectification and closed loop control circuit, and the synchronous rectification and closed loop control circuit comprises a first control module, a second control module and a branch control module.

[0072] The first control module is configured to sample the output voltage of the non-main closed loop output branch, and generate a first PWM control signal based on the sampled voltage.

[0073] The second control module is provided with an auxiliary winding, and a voltage control signal is generated based on the auxiliary winding;

[0074] The branch control module is configured to generate a branch control signal based on the first PWM control signal and the voltage control signal, and drive and control the non-main closed-loop output branch thereof by using the branch control signal.

[0075] Specifically, the branch control module generates the branch control signal in the following manner:

[0076] If the voltage control signal is a high-level signal and the first PWM control signal is a high-level signal, the branch control signal is a high-level signal; otherwise, the branch control signal is a low-level signal.

[0077] When the branch control signal is a high-level signal, the non-main closed-loop output branch is turned on to output a voltage; otherwise, the non-main closed-loop output branch is not turned on.

[0078] Specifically, the number of turns n of the auxiliary winding in the second control module C is represented as:

[0079]

[0080] In the formula, n A , n B are the numbers of turns of the primary winding of the transformer and the corresponding secondary winding of the non-main closed-loop output branch, respectively, V in , V O are the input voltage of the input module and the output voltage of the non-main closed-loop output branch, respectively.

[0081] In a specific implementation, the first control module includes first, second, third, fourth, fifth, sixth, seventh and tenth resistors, a PWM control chip, second and third capacitors, and a triode.

[0082] The first resistor and the fifth resistor are connected in series between the positive and negative poles of the output voltage of the non-main closed-loop output branch, and the first resistor is connected to the positive pole of the voltage. One end of the third resistor is connected to the connection end of the first resistor and the fifth resistor, and the other end is connected to the inverting terminal of the error amplifier of the PWM control chip via the second capacitor and the second resistor. The other end of the third resistor is also connected to the reference voltage terminal of the error amplifier of the PWM control chip.

[0083] One end of the sixth resistor is connected with the negative pole of the non-closed loop output branch output voltage, and the other end is connected with the current comparator input end of the PWM control chip, and the other end of the sixth resistor is also connected with the emitter of the transistor through the tenth resistor; the collector of the transistor is connected with the base through the seventh resistor, and the collector is also connected with the chip reference voltage end of the PWM control chip; the base of the transistor is also connected with the oscillation timing end of the PWM control chip and one end of the third capacitor; the other end of the third capacitor is connected with the negative pole of the non-closed loop output branch output voltage;

[0084] The power supply end of the PWM control chip is connected with the positive pole of the non-closed loop output branch output voltage, the grounding end is connected with the negative pole of the non-closed loop output branch output voltage, and the output end outputs the first PWM control signal after the fourth resistor.

[0085] Specifically, the PWM control chip is a current type PWM controller.

[0086] The working principle is that the output voltage of the non-closed loop output branch is divided by the first resistor and the fifth resistor, and then sampled into the error amplifier reference voltage end of the PWM control chip, and the resistance-capacitance elements second resistor, third resistor and second capacitor and the error amplifier inside the PWM control chip constitute a PI type operational amplifier to improve the gain and frequency characteristics of the control loop; the oscillation timing end of the PWM control chip generates a fixed frequency oscillation signal according to the parameters of the external seventh resistor and the third capacitor to determine the working frequency, in addition, this end and the transistor, the sixth resistor and the tenth resistor constitute an emitter follower, wherein the collector of the transistor is connected to the chip reference voltage end, the sawtooth wave signal of the base can be power amplified through the chip reference voltage and output through the emitter, and after being divided by the sixth resistor and the tenth resistor, it is sent to the current comparator input end of the PWM control chip, so as to generate a fixed frequency and amplitude sawtooth wave signal, which is compared with the output modulation voltage of the above-mentioned PI type operational amplifier, so as to generate a rectangular wave signal with variable duty cycle and constant frequency, that is, the first PWM control signal, and output by the output end.

[0087] In specific implementation, the second control module includes an auxiliary winding, an eighth resistor and a ninth resistor.

[0088] The same name end of the auxiliary winding is connected with one end of the eighth resistor, the other end of the eighth resistor outputs a voltage control signal, and the other end of the eighth resistor is also connected with the different name end of the auxiliary winding through the ninth resistor; the different name end of the auxiliary winding is also connected with the negative pole of the non-closed loop output branch output voltage.

[0089] It can be understood that the auxiliary winding determines the number of turns according to the primary winding of the transformer and the corresponding secondary winding of the non-closed loop output branch, and outputs a voltage control signal based on the energy transmitted by the transformer to participate in the control of the non-closed loop output branch.

[0090] In specific implementation, the branch control module includes a Zener diode; the anode of the Zener diode receives the first PWM control signal, and the cathode receives the voltage control signal; and the anode of the Zener diode also outputs the branch control signal.

[0091] In specific implementation, the non-main closed loop output branch performs direct current voltage stabilization output through a secondary output branch; the secondary output branch includes a first NMOS tube and a first capacitor.

[0092] One end of the first capacitor is connected to the same-named end of the corresponding secondary winding of the non-main closed loop output branch, and also serves as the positive pole of the output voltage of the non-main closed loop output branch; the other end of the first capacitor is grounded, and also serves as the negative pole of the output voltage of the non-main closed loop output branch.

[0093] The source of the first NMOS tube is connected to the other end of the first capacitor, the drain is connected to the different-named end of the corresponding secondary winding of the non-main closed loop output branch, and the gate receives the branch control signal.

[0094] It can be understood that the corresponding secondary winding of the non-main closed loop output branch transmits energy in isolation, and then performs rectification conversion through the first NMOS tube and direct current ripple filtering through the first capacitor to perform direct current voltage stabilization output.

[0095] It should be noted that the first control module, the second control module and the branch control module jointly constitute an AND gate logic for controlling the on-off of the first NMOS tube, so as to achieve driving control of the non-main closed loop output branch, specifically:

[0096] If the auxiliary winding voltage is low and the PWM control chip output is low, the driving voltage of the first NMOS tube is low; wherein the driving voltage of the first NMOS tube is the voltage between the gate and the source;

[0097] If the auxiliary winding voltage is low and the PWM control chip output is high, the Zener diode is subjected to positive voltage and thus turned on, and the anode voltage of the Zener diode is pulled low, i.e. the driving voltage of the first NMOS tube is low;

[0098] If the auxiliary winding voltage is high and the PWM control chip output is low, the Zener diode is subjected to reverse voltage and thus cut off, and the driving voltage of the first NMOS tube is the output voltage of the PWM control chip, which is low;

[0099] If the auxiliary winding voltage is high level, the PWM control chip output is high level, at this time if the negative voltage of the stabilizing diode is higher than the positive electrode, the stabilizing diode is cut off, the driving voltage of the first NMOS tube is provided by the PWM control chip, and is high level, if the negative voltage of the stabilizing diode is lower than the positive electrode, the stabilizing diode is turned on, the output voltage of the PWM control chip is pulled down to be consistent with the negative electrode of the stabilizing diode, and the driving voltage of the first NMOS tube is provided by the auxiliary winding, and is still high level.

[0100] It can be understood that the output signal of the auxiliary winding and the output signal of the PWM control chip are subjected to "and" operation and then drive and control the first NMOS tube, so that the first NMOS tube is turned on when the auxiliary winding and the PWM control chip are both high level, the circuit significance is that the branch in which the first NMOS tube is located is "chopped" by the primary side circuit in a cycle, the secondary winding starts to transfer energy to the branch (corresponding to the high level of the auxiliary winding), and the first NMOS tube is turned on to perform power conversion after the output high level driving voltage of the closed loop control circuit is modulated, so as to realize voltage output; and the first NMOS tube is turned off when the auxiliary winding and the PWM control chip are low level, the circuit significance is that the first NMOS tube is turned off to stop power conversion as long as the secondary winding completes energy transfer to the branch (corresponding to the low level of the auxiliary winding) or the low level driving voltage of the closed loop control circuit is modulated, so as to realize dynamic adjustment; through the periodic alternation of the above two working modes, the synchronous rectification control of the first NMOS tube and the closed loop adjustment of the branch can be realized, so as to reduce the working loss of the first NMOS tube and improve the working efficiency of the circuit. In addition, the closed loop control is introduced in the non-main closed loop output branch, so that the precision of the output voltage is greatly improved.

[0101] Compared with the prior art, the embodiment provides a DCDC power supply synchronous rectification and closed-loop control circuit, which comprises an input module, a transformer, a main closed-loop output branch and one non-main closed-loop output branch.

[0102] Embodiment 2

[0103] The present application provides one specific embodiment 2, taking a two-way flyback power supply as an example, that is, in addition to the branch participating in the main closed-loop output, only one output branch not participating in the main closed-loop is contained, as shown in Figure 5 The embodiment 1 is described.

[0104] The DCDC power supply synchronous rectification and closed-loop control circuit comprises an input module, a transformer, a main closed-loop output branch and one non-main closed-loop output branch. The transformer primary winding T1A, secondary winding T1B and T1D.

[0105] The non-main closed-loop output branch comprises a secondary output branch and a synchronous rectification and closed-loop control circuit; the secondary output branch comprises a first NMOS tube (Q1) and a first capacitor (C1); the synchronous rectification and closed-loop control circuit comprises a first control module, a second control module and a branch control module.

[0106] The first control module comprises a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor and a tenth resistor (R1, R2, R3, R4, R5, R6, R7, R10), a PWM control chip (N1), a second capacitor and a third capacitor (C2, C3) and a triode (VT1).

[0107] Taking resistors R1 and R5 as an example, the first resistor and the fifth resistor for output voltage sampling satisfy:

[0108]

[0109] wherein, V O1 R1 is usually several kΩ to several tens of kΩ.

[0110] For example, the second resistance, the third resistance and the second capacitor are selected according to the actual circuit debugging, and R2 / R3 is usually 2-50, R3 is usually several kΩ to several tens of kΩ, and C2 is usually 0.1 nF-1 uF.

[0111] For example, the seventh resistance and the third capacitor satisfy:

[0112]

[0113] wherein, f c R7 is usually several kΩ to several tens of kΩ.

[0114] For example, the sixth resistance and the tenth resistance satisfy: R10 / R6 is 2-5, and R10 is usually several kΩ.

[0115] For example, the fourth resistance is usually several Ω to several tens of Ω.

[0116] The second control module includes an auxiliary winding (T1C), an eighth resistance (R8) and a ninth resistance (R9); the branch control module includes a voltage stabilizing diode (VD1).

[0117] For example, the eighth resistance and the ninth resistance satisfy: R8 / R9 is usually several kΩ.

[0118] Specifically, the PWM control chip adopts a current type PWM controller; for example, UCC2803D chip.

[0119] The main closed loop output branch includes a main output branch and a control module; the main output branch includes a third diode (VD2) and a fourth capacitor (C4); the control module includes eleventh, twelfth, thirteenth and fourteenth resistances (R11, R12, R13 and R14), fifth and sixth capacitors (C5, C6), a three-terminal voltage regulator (VZ1), an optical coupler (BO1), a PWM controller (U2), and a driver (U1).

[0120] Specifically, the three-terminal voltage regulator adopts TL431.

[0121] The input module includes a second NMOS tube (Q2), a third NMOS tube (Q3), a first diode (D1) and a second diode (D2).

[0122] In the embodiment, the selection mode of each component in the specific circuit is given, and the DCDC power synchronous rectification and closed-loop control are realized through the setting.

[0123] Those skilled in the art can understand that all or part of the processes of the above-mentioned embodiment methods can be completed by a computer program instructing relevant hardware, and the program can be stored in a computer readable storage medium, wherein the computer readable storage medium is a disk, an optical disc, a read-only memory or a random access memory, etc.

[0124] The above merely describes the preferred embodiments of the present application, but the protection scope of the present application is not limited to this. Any changes or replacements within the technical scope disclosed by the present application can be easily conceived by those skilled in the art, and should be covered within the protection scope of the present application.

Claims

1. A DCDC power supply synchronous rectification and closed loop control circuit, characterized in that, The input module, the transformer, the main closed-loop output branch, and at least one non-main closed-loop output branch are included. The input module is configured to transmit the input DC voltage to the transformer after power conversion. The transformer is configured to convert the received converted voltage into energy through the primary winding and transmit the energy to each secondary winding. The main closed-loop output branch is configured to perform DC voltage stabilization output on the energy transmitted by the corresponding secondary winding after rectification and filtering, and drive control the input module based on the output voltage to realize closed-loop control of the voltage. The non-main closed-loop output branch is configured to perform DC voltage stabilization output on the energy transmitted by the corresponding secondary winding after rectification and filtering, and perform synchronous rectification and closed-loop control of the non-main closed-loop output branch based on the output voltage.

2. The DCDC power supply synchronous rectification and closed loop control circuit of claim 1, wherein, The non-main closed-loop output branch performs synchronous rectification and closed-loop control of the non-main closed-loop output branch through a synchronous rectification and closed-loop control circuit, which includes a first control module, a second control module, and a branch control module. The first control module is configured to sample the output voltage of the non-main closed-loop output branch and generate a first PWM control signal based on the sampled voltage. The second control module is provided with an auxiliary winding and generates a voltage control signal based on the auxiliary winding. The branch control module is configured to generate a branch control signal based on the first PWM control signal and the voltage control signal, and drive control the non-main closed-loop output branch through the branch control signal.

3. The DCDC power supply synchronous rectification and closed loop control circuit of claim 2, wherein, The branch control module generates the branch control signal in the following manner: If the voltage control signal is a high-level signal and the first PWM control signal is a high-level signal, the branch control signal is a high-level signal; otherwise, the branch control signal is a low-level signal. When the branch control signal is a high-level signal, the non-main closed-loop output branch is turned on to output the voltage; otherwise, the non-main closed-loop output branch is not turned on.

4. The DCDC power supply synchronous rectification and closed loop control circuit of claim 2, wherein, The number of turns n of the auxiliary winding C is represented as: In the formula, n A , n B are the number of turns of the primary winding of the transformer and the corresponding secondary winding of the non-main closed-loop output branch, respectively, V in , V O are the input voltage of the input module and the output voltage of the non-main closed-loop output branch, respectively.

5. The DCDC power supply synchronous rectification and closed loop control circuit of claim 1, wherein, The main closed-loop output branch drives the input module in the following manner: Sample the output voltage of the main closed-loop output branch and compensate the sampled voltage. Isolate and transmit the compensated voltage, and generate a second PWM control signal through a PWM controller. Power amplify the second PWM control signal to generate a first input control signal and a second input control signal, and output them to the input module for drive control.

6. The DCDC power supply synchronous rectification and closed loop control circuit of claim 2, wherein, The first control module includes a first, second, third, fourth, fifth, sixth, seventh, and tenth resistor, a PWM control chip, a second and third capacitor, and a triode. The first resistor and the fifth resistor are connected in series between the positive pole and the negative pole of the non-closed loop output branch output voltage, and the first resistor is connected with the positive pole of the voltage; one end of the third resistor is connected with the connection end of the first resistor and the fifth resistor, and the other end is connected with the inverting input terminal of the error amplifier of the PWM control chip through the second capacitor and the second resistor, and the other end of the third resistor is also connected with the reference voltage terminal of the error amplifier of the PWM control chip; One end of the sixth resistor is connected with the negative pole of the non-closed loop output branch output voltage, and the other end is connected with the input terminal of the current comparator of the PWM control chip, and the other end of the sixth resistor is also connected with the emitter of the transistor through the tenth resistor; the collector of the transistor is connected with the base through the seventh resistor, and the collector is also connected with the chip reference voltage terminal of the PWM control chip; the base of the transistor is also connected with the oscillation timing terminal of the PWM control chip and one end of the third capacitor; the other end of the third capacitor is connected with the negative pole of the non-closed loop output branch output voltage; The power supply terminal of the PWM control chip is connected with the positive pole of the non-closed loop output branch output voltage, the grounding terminal is connected with the negative pole of the non-closed loop output branch output voltage, and the output terminal outputs the first PWM control signal through the fourth resistor.

7. The DCDC power supply synchronous rectification and closed loop control circuit of claim 2, wherein, The second control module comprises an auxiliary winding, an eighth resistor and a ninth resistor; The same name end of the auxiliary winding is connected with one end of the eighth resistor, and the other end outputs a voltage control signal, and the other end of the eighth resistor is also connected with the different name end of the auxiliary winding through the ninth resistor; the different name end of the auxiliary winding is also connected with the negative pole of the non-closed loop output branch output voltage.

8. The DCDC power supply synchronous rectification and closed loop control circuit of claim 2, wherein, The branch control module comprises a stabilizing diode; the negative pole of the stabilizing diode receives the first PWM control signal, and the positive pole receives the voltage control signal, and the positive pole of the stabilizing diode also outputs a branch control signal.

9. The DCDC power supply synchronous rectification and closed loop control circuit of claim 1, wherein, The non-main closed loop output branch outputs direct current and stabilizes voltage through a secondary output branch; the secondary output branch comprises a first NMOS tube and a first capacitor; One end of the first capacitor is connected with the same name end of the corresponding secondary side winding of the non-main closed loop output branch, and also serves as the positive pole of the output voltage of the non-main closed loop output branch; the other end of the first capacitor is grounded, and also serves as the negative pole of the output voltage of the non-main closed loop output branch; The source of the first NMOS tube is connected with the other end of the first capacitor, the drain is connected with the different name end of the corresponding secondary side winding of the non-main closed loop output branch, and the gate receives a branch control signal.

10. The DCDC power supply synchronous rectification and closed loop control circuit of claim 1, wherein, The main closed loop output branch outputs direct current and stabilizes voltage through a main output branch; the main output branch comprises a third diode and a fourth capacitor; One end of the fourth capacitor is connected with the negative pole of the third diode, and also serves as the positive pole of the output voltage of the main closed loop output branch; the positive pole of the third diode is connected with the same name end of the corresponding secondary side winding of the main closed loop output branch; The other end of the fourth capacitor is connected with the different name end of the corresponding secondary side winding of the main closed loop output branch, and the other end of the fourth capacitor is grounded, and also serves as the negative pole of the output voltage of the main closed loop output branch.

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