CN108347157B

CN108347157B - Synchronous rectification control device and synchronous rectification control circuit thereof

Info

Publication number: CN108347157B
Application number: CN201710911260.8A
Authority: CN
Inventors: 赵鑫; 宗强; 刘准; 管磊
Original assignee: Shenzhen Xinmao Microelectronics Co Ltd
Current assignee: Shenzhen Xinmao Microelectronics Co Ltd
Priority date: 2017-09-29
Filing date: 2017-09-29
Publication date: 2020-01-17
Anticipated expiration: 2037-09-29
Also published as: CN108347157A

Abstract

The invention relates to a synchronous rectification control device and a synchronous rectification control circuit thereof. The synchronous rectification control device comprises: the device comprises a power supply module, a reference module, a comparator module, a primary side opening judgment module, a logic module and a synchronous rectifier tube module. The reference module generates a first reference signal and a second reference signal based on a voltage signal provided by the power supply module. The comparator module generates a comparison decision signal based on the first reference signal, the second reference signal, and the D-terminal voltage signal. The primary side opening judging module generates a primary side opening judging signal based on the D end voltage signal. And the logic module generates a logic control signal for controlling the synchronous rectifier tube module to be switched on or switched off based on the comparison judgment signal and the primary side switching-on judgment signal. The invention can effectively avoid the misoperation of the synchronous rectifier tube caused by the resonance when the system works in the discontinuous mode, thereby avoiding the problems of serious heating and efficiency loss caused by insufficient power supply.

Description

Synchronous rectification control device and synchronous rectification control circuit thereof

Technical Field

The invention relates to the field of synchronous rectification control, in particular to a synchronous rectification control circuit of a synchronous rectification control device.

Background

At present, the purpose of isolated synchronous rectification is mainly to replace a secondary schottky rectifier tube on the output occasion of low voltage and large current, so as to obtain better efficiency, smaller application volume and lower system cost. The forward conduction voltage drop of the Schottky tube with low conduction voltage drop is about 0.2-0.3V, and the conduction voltage drop of the synchronous rectifier tube can be below 0.15V under the condition of reasonable design, so that the loss of the rectifier tube per se is greatly reduced, and the system efficiency is improved.

The existing synchronous rectification technology has two difficulties, firstly, when judging the conduction of the synchronous rectification tube, the conduction of the synchronous rectification tube is shielded for a period of time only after the synchronous rectification tube is turned off, and then whether the source voltage of the synchronous rectification tube reaches negative pressure or not is detected. When the chip works in an intermittent mode, the source voltage of the synchronous rectifier tube generates resonance, the resonance voltage can reach negative voltage after shielding time, and the false opening can occur at the moment, so that the primary side and the secondary side are penetrated, the chip can generate heat abnormally, and the primary side chip can be burnt even in severe cases. Secondly, in high-power application, the driving current required by the chip is large, the power supply may be insufficient, so that the driving voltage is reduced, the conduction impedance of the synchronous rectifier tube is increased, and the chip generates heat seriously.

Therefore, the existing synchronous rectification control circuit cannot accurately work under the condition of facing complex system work, the working efficiency is low, and even serious consequences of a fryer can be caused. Meanwhile, in high-power application, the problem of chip heating caused by insufficient power supply is difficult to solve.

Disclosure of Invention

The present invention provides a synchronous rectification control circuit of a synchronous rectification control device, aiming at solving the problems of the prior synchronous rectification control circuit that the original side open identification mechanism is lacked, which causes the misoperation of the synchronous rectification tube, and the problems of serious heating and efficiency loss caused by insufficient power supply.

The technical scheme adopted by the invention for solving the technical problems is as follows: a synchronous rectification control device is constructed, including: the synchronous rectifier tube module comprises a power supply module, a reference module, a comparator module, a primary side opening judging module, a logic module and a synchronous rectifier tube module, wherein the reference module generates a first reference signal and a second reference signal based on a voltage signal provided by the power supply module, the comparator module generates a comparison judging signal based on the first reference signal, the second reference signal and a D terminal voltage signal, the primary side opening judging module generates a primary side opening judging signal based on the D terminal voltage signal, and the logic module generates a logic control signal for controlling the synchronous rectifier tube module to be opened or closed based on the comparison judging signal and the primary side opening judging signal.

In the synchronous rectification control device according to the present invention, the comparator module includes an on comparator that generates a first on determination signal based on the D-terminal voltage signal and the first reference signal, and a first off comparator that generates a first off determination signal based on the D-terminal voltage signal and the second reference signal.

In the synchronous rectification control device of the present invention, the logic module generates an on logic control signal for controlling the synchronous rectification tube module to be on based on the first on determination signal and the primary side on determination signal, and generates an off logic control signal for controlling the synchronous rectification tube module to be off based on the first off determination signal.

In the synchronous rectification control device according to the present invention, the reference module further generates a third reference signal based on the voltage signal provided by the power supply module, and the comparator module includes a second turn-off comparator that generates a second turn-off determination signal based on the D-terminal voltage signal and the third reference signal.

In the synchronous rectification control device according to the present invention, the logic module generates a shutdown logic control signal for controlling shutdown of the synchronous rectification tube module based on the first shutdown determination signal and/or the second shutdown determination signal.

In the synchronous rectification control device of the present invention, the primary side switching-on determination module includes a first comparator, a second comparator, a first switch tube, a second switch tube, a third switch tube, a first current source, a second current source, a first capacitor, a second capacitor, a first resistor and a second resistor, a first input terminal of the first comparator receives a reference voltage signal, a second input terminal of the first comparator receives the D-side voltage signal, and an output terminal of the first comparator is connected to the first end of the first switch tube, a second end of the first switch tube is connected to the first end of the second current source and the second end of the third switch tube, a third end of the first switch tube is grounded via the first current source, a first end of the second switch tube is connected to the third end of the first switch tube, a second end of the second switch tube is connected to the second end of the second current source and the first end of the second switch tube, the third end of the third switching tube is grounded through the first resistor and the second resistor, the first input end of the second comparator is grounded, the second input end of the second comparator is connected with the connection point of the first resistor and the second resistor, the output end of the second comparator is connected with the logic module, the second capacitor is connected between the first end of the second switching tube and the ground, and the first capacitor is connected between the second input end of the first comparator and the second input end of the second comparator.

In the synchronous rectification control device of the present invention, the power supply module includes a power supply unit and a clamping unit electrically connected to the power supply unit, the clamping unit includes a fourth switching tube and a fifth switching tube, a first end and a third end of the fifth switching tube are grounded, a second end of the fifth switching tube is connected to a second end and a first end of the fourth switching tube, a third end of the fourth switching tube is connected to a power supply terminal of the synchronous rectification control device, and a second end of the fourth switching tube is connected to a frequency conversion terminal of the synchronous rectification control device.

In the synchronous rectification control device of the present invention, the synchronous rectification tube module includes a driving unit, a clamp circuit and a synchronous rectification tube, an input end of the driving unit is connected to an output end of the logic module, an output end of the driving unit is connected to a first end of the synchronous rectification tube, a second end of the synchronous rectification tube is connected to a power supply, a third end of the synchronous rectification tube is grounded, and the clamp circuit is connected between the first end and the third end of the synchronous rectification tube.

Another technical solution adopted by the present invention to solve the technical problem is to construct a synchronous rectification control circuit, which includes a transformer, a first secondary capacitor, a second secondary capacitor, a third secondary capacitor and the synchronous rectification control device, wherein the first secondary capacitor and the synchronous rectification control device are connected in series and then connected to the secondary side of the transformer, the second secondary capacitor is connected between a power supply end and a first end of the synchronous rectification control device, and the third secondary capacitor is connected between a frequency conversion end and a second end of the synchronous rectification control device.

In the synchronous rectification control circuit, a first end of the synchronous rectification control device is connected with a first end of a secondary side of the transformer, a second end of the secondary side of the transformer is grounded, and a first end of the first secondary side capacitor is connected with a second end of the secondary side of the transformer; or the first end of the synchronous rectification control device is grounded through the first secondary capacitor, the second end of the synchronous rectification control device is connected with the first secondary end of the transformer, and the second secondary end of the transformer is grounded.

The synchronous rectification control circuit of the synchronous rectification control device can effectively avoid misoperation of the synchronous rectification tube caused by resonance when the system works in an intermittent mode by arranging the primary side switching-on judging module, thereby avoiding the problems of serious heating and efficiency loss caused by insufficient power supply.

Drawings

The invention will be further described with reference to the accompanying drawings and examples, in which:

FIG. 1 is a functional block diagram of a first embodiment of a synchronous rectification control apparatus of the present invention;

FIG. 2 is a functional block diagram of a second embodiment of the synchronous rectification control apparatus of the present invention;

FIG. 3 is a functional block diagram of a third embodiment of the synchronous rectification control apparatus of the present invention;

FIG. 4 is a circuit schematic of a preferred embodiment of a primary side turn-on decision module of the synchronous rectification control device shown in FIG. 3;

FIG. 5 is a circuit schematic of a preferred embodiment of a power supply module of the synchronous rectification control device shown in FIG. 3;

FIG. 6 is a circuit schematic of a first embodiment of the synchronous rectification control circuit of the present invention;

FIG. 7 is a circuit schematic of a second embodiment of the synchronous rectification control circuit of the present invention;

FIG. 8 is a waveform diagram of each node of the synchronous rectification control device of the present invention;

fig. 9 is a waveform diagram of each node of the synchronous rectification control circuit of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Fig. 1 is a schematic block diagram of a first embodiment of a synchronous rectification control apparatus of the present invention. As shown in fig. 1, the synchronous rectification control apparatus of the present invention includes: the circuit comprises a power supply module 100, a reference module 200, a comparator module 300, a primary side switching-on judging module 400, a logic module 500 and a synchronous rectifier tube module 600. As shown in fig. 1, the reference module 200 generates a first reference signal and a second reference signal based on the voltage signal provided by the power supply module 100. The comparator module 300 generates a comparison decision signal based on the first reference signal, the second reference signal, and the D-terminal voltage signal. The primary side turn-on determination module 400 generates a primary side turn-on determination signal based on the D-terminal voltage signal. The logic module 500 generates a logic control signal for controlling the synchronous rectifier tube module 600 to be turned on or off based on the comparison determination signal and the primary side turn-on determination signal.

In a preferred embodiment of the present invention, the power supply module 100 may be connected to a power supply, the synchronous rectifier module 600 and the reference module 200, so as to provide voltage for the reference module 200 and the synchronous rectifier module 600. The reference module 200 generates a first reference signal and a second reference signal based on the voltage signal provided by the power supply module 100 and then transmits them to the comparator module 300. The comparator module 300 compares the first reference signal and the second reference signal with a D-terminal voltage signal in a synchronous rectification control circuit in which the synchronous rectification control device is located, generates a first on determination signal based on a comparison result of the first reference signal and the D-terminal voltage signal, and generates a first off determination signal based on a comparison result of the second reference signal and the D-terminal voltage signal. The primary side turn-on determining module 400 also receives the D-terminal voltage signal, generates a primary side turn-on determining signal by determining the falling slope thereof, and transmits the primary side turn-on determining signal to the logic module 500. At this time, when the logic module 500 generates a logic control signal for controlling the synchronous rectifier tube module 600 to be turned on based on the received primary side turn-on determination signal and the first turn-on determination signal. Meanwhile, the logic module 500 generates a logic control signal for controlling the synchronous rectifier tube module 600 to turn off based on the reception of the first turn-off determination signal. In the present invention, when the logic module 500 receives a primary side turn-on determination signal indicating that the slope of the voltage at the D terminal decreases from the primary side turn-on determination module 400 and a first turn-on determination signal indicating that the voltage at the D terminal is negative from the comparator module 300 at the same time, a logic control signal for controlling the synchronous rectifier tube module 600 to turn on is generated.

In this embodiment, the power supply module 100, the reference module 200, the comparator module 300, the primary side on-state determination module 400, the logic module 500, and the synchronous rectifier module 600 may be implemented by any circuit, module, software, or chip known in the art. In this embodiment, the first reference signal and the second reference signal can be generated by a person skilled in the art by selecting an appropriate reference module 200 according to actual needs, and thus, the description is not repeated here.

Therefore, the synchronous rectification control device provided by the invention can effectively avoid misoperation of the synchronous rectification tube caused by resonance when the system works in an intermittent mode by arranging the primary side switching-on judgment module, thereby avoiding the problems of serious heating and efficiency loss caused by insufficient power supply.

Fig. 2 is a schematic block diagram of a second embodiment of the synchronous rectification control apparatus of the present invention. As shown in fig. 2, the synchronous rectification control apparatus of the present invention includes: the circuit comprises a power supply module 100, a reference module 200, a comparator module 300, a primary side switching-on judging module 400, a logic module 500 and a synchronous rectifier tube module 600. In the embodiment shown in fig. 2, the comparator module 300 comprises an on comparator 301 and a first off comparator 302. As shown in fig. 2, the reference module 200 generates a first reference signal and a second reference signal based on the voltage signal provided by the power supply module 100. The turn-on comparator 301 generates a first turn-on determination signal based on the D-terminal voltage signal and the first reference signal. The first turn-off comparator 302 generates a first turn-off decision signal based on the D-terminal voltage signal and the second reference signal. The primary side turn-on determining module 400 also receives the D-terminal voltage signal, generates a primary side turn-on determining signal by determining the falling slope thereof, and transmits the primary side turn-on determining signal to the logic module 500. At this time, when the logic module 500 generates a logic control signal for controlling the synchronous rectifier tube module 600 to be turned on based on the received primary side turn-on determination signal and the first turn-on determination signal. Meanwhile, the logic module 500 generates a logic control signal for controlling the synchronous rectifier tube module 600 to turn off based on the reception of the first turn-off determination signal. In the present invention, when the logic module 500 receives a primary side turn-on determination signal indicating that the slope of the voltage at the D terminal decreases from the primary side turn-on determination module 400 and a first turn-on determination signal indicating that the voltage at the D terminal is negative from the comparator module 300 at the same time, a logic control signal for controlling the synchronous rectifier tube module 600 to turn on is generated.

In this embodiment, the power supply module 100, the reference module 200, the on comparator 301, the first off comparator 302, the primary side on determination module 400, the logic module 500, and the synchronous rectifier module 600 may be implemented by any circuit, module, software, or chip known in the art. In this embodiment, the first reference signal and the second reference signal can be generated by a person skilled in the art by selecting an appropriate reference module 200 according to actual needs, and thus, the description is not repeated here.

Fig. 3 is a schematic block diagram of a third embodiment of the synchronous rectification control apparatus of the present invention. As shown in fig. 3, the synchronous rectification control apparatus of the present invention includes: the circuit comprises a power supply module 100, a reference module 200, a comparator module 300, a primary side switching-on judging module 400, a logic module 500 and a synchronous rectifier tube module 600. In the preferred embodiment shown in fig. 3, the comparator module 300 comprises a turn-on comparator 301, a first turn-off comparator 302 and a second turn-off comparator 303; the synchronous rectifier module 600 includes a driving unit 601, a clamping circuit 602, and a synchronous rectifier 603.

As shown in fig. 3, one end of the power supply module 100 is connected to the synchronous rectifier module 600, and the other end is connected to the power source VCC and the reference module 200. The reference module 200 generates a first reference signal, a second reference signal and a third reference signal based on the voltage signal provided by the power supply module 100. The turn-on comparator 301 generates a first turn-on determination signal based on the D-terminal voltage signal and the first reference signal. The first turn-off comparator 302 generates a first turn-off decision signal ON1 based ON the D-terminal voltage signal and the second reference signal. The second turn-off comparator 303 generates a second turn-off decision signal based on the D-terminal voltage signal and the third reference signal. In a preferred embodiment of the present invention, the D-terminal voltage signals may be D-terminal voltage signals of different time periods. And the second reference signal and the third reference signal correspond to the reference voltage signals of the D terminal voltage signals in different time periods. For example, when the collected D-terminal voltage signal is a time period of T1, the first turn-off comparator 302 may be adopted to generate a first turn-off determination signal based on the D-terminal voltage signal and the second reference signal during the time period of T1. When the collected D-terminal voltage signal is in a time period of T2, the second turn-off comparator 303 may be adopted to generate a second turn-off determination signal based on the D-terminal voltage signal in the time period of T2 and the third reference signal. For another example, when the D-terminal voltage signal of the time period T1 is collected and the D-terminal voltage signal of the time period T2 is collected, one or two of the signals may be selected and compared with the second reference signal and the third reference signal, respectively, so as to generate the first OFF decision signal OFF1 and/or the second OFF decision signal OFF 2. Generally, the first OFF decision signal OFF1 and/or the second OFF decision signal OFF2 representing OFF may be generated when the D-terminal voltage signal of the T1 and/or T2 time period is higher than the second reference signal and/or the third reference signal. The primary side ON determination module 400 also receives the D-terminal voltage signal, generates a primary side ON determination signal ON2 by determining the falling slope thereof, and transmits the primary side ON determination signal to the logic module 500.

At this time, when the logic module 500 generates a logic control signal for controlling the synchronous rectifier tube module 600 to be turned ON based ON the received primary side ON determination signal ON2 and the first ON determination signal ON 1. Meanwhile, the logic module 500 generates a logic control signal for controlling the synchronous rectifier module 600 to turn OFF based on receiving the first turn-OFF decision signal OFF1 and/or the second turn-OFF decision signal OFF 2. In the present invention, when the logic module 500 receives a primary side turn-on determination signal indicating that the slope of the voltage at the D terminal decreases from the primary side turn-on determination module 400 and a first turn-on determination signal indicating that the voltage at the D terminal is negative from the comparator module 300 at the same time, a logic control signal for controlling the synchronous rectifier tube module 600 to turn on is generated. In the present invention, the logic module 500 generates the logic control signal for controlling the synchronous rectifier module 600 to turn off as long as a turn-off determination signal indicating that the voltage at the D-side is higher than the reference signal is received from at least one of the first turn-off comparator 302 and the second turn-off comparator 303.

As further shown in fig. 3, an input terminal of the driving unit 601 is connected to an output terminal of the logic module 500, and an output terminal of the driving unit 601 is connected to a gate of the synchronous rectifier 603. The drain of the synchronous rectifier 603 is connected to the power VCC, the source is grounded, and the clamp 602 is connected between the gate and the source of the synchronous rectifier 603. In this way, the driving unit 601 can control the synchronous rectifier 603 according to the on or off logic control signal generated by the logic module 601.

In this embodiment, the power supply module 100, the reference module 200, the on comparator 301, the first off comparator 302, the second comparator 303, the primary side on determination module 400, the logic module 500, and the synchronous rectifier module 600 may be implemented by any circuit, module, software, or chip known in the art. Fig. 4-5 below show schematic circuit diagrams of a preferred primary side on decision module 400 and power supply module 100 of the present invention.

As shown in fig. 4, the primary side on determination module 400 includes a first comparator CMP1, a second comparator CMP2, a MOS transistor MP1, a transistor PNP1, a transistor NPN1, a first current source I1, a second current source I2, a first capacitor C1, a second capacitor C2, a first resistor R1, and a second resistor R2. As shown in fig. 4, the inverting input terminal of the first comparator CMP1 receives the reference voltage signal, the forward input terminal receives the D-terminal voltage signal, and the output terminal is connected to the gate of the MOS transistor MP 1. The drain of the MOS transistor MP1 is connected to the first terminal of the second current source I2 and the collector of the triode NPN 1. The source of the MOS transistor MP1 is grounded via the first current source I1. The base of the transistor PNP1 is connected to the source of the MOS transistor MP1, and the emitter of the transistor PNP1 is connected to the second terminal of the second current source I2 and the base of the transistor NPN 1. The emitter of the transistor NPN1 is grounded via the first resistor R1 and the second resistor R2, the inverting input terminal of the second comparator CMP2 is grounded, the forward input terminal is connected to the connection point of the first resistor R1 and the second resistor R2, and the output terminal is connected to the logic module 500, the second capacitor C2 is connected between the first terminal of the transistor PNP1 and ground, and the first capacitor C1 is connected between the forward input terminal of the first comparator CMP1 and the forward input terminal of the second comparator CMP 2.

As shown in fig. 5, the power supply module 100 includes a power supply unit and a clamping unit electrically connected to the power supply unit. The clamping unit includes a transistor Q1 and a transistor Q2. The base and the collector of the transistor Q2 are grounded, and the emitter is connected with the base and the collector of the transistor Q1. An emitting electrode of the triode Q1 is connected with a power supply end VCC, and a collecting electrode of the triode Q1 is also connected with a frequency conversion end CVF of the synchronous rectification control device.

The advantages and principles of the present invention will be described in detail below in a synchronous rectification control circuit including the synchronous rectification control device, and will not be described in detail herein.

Fig. 6 to 7 show two application modes of the synchronous rectification control device of the present invention, i.e., first and second embodiments of the synchronous rectification control circuit to which the synchronous rectification control device of the present invention is applied. Fig. 8 is a waveform diagram of each node of the synchronous rectification control device of the present invention. Fig. 9 is a waveform diagram of each node of the synchronous rectification control circuit of the present invention.

As shown in fig. 6, the synchronous rectification control circuit includes a transformer T1, a first secondary capacitor C11, a second secondary capacitor C12, a third secondary capacitor C13, and any one of the synchronous rectification control devices IC 1. As shown in fig. 6, the first secondary capacitor C11 and the synchronous rectification control device IC1 are connected in series and then connected to the secondary side of the transformer T1, the second secondary capacitor C12 is connected between the power supply terminal VCC and the first terminal S of the synchronous rectification control device, and the third secondary capacitor C13 is connected between the frequency conversion terminal CVF and the second terminal D of the synchronous rectification control device. As further shown in fig. 6, the first terminal D of the synchronous rectification control device is connected to the first terminal of the secondary side of the transformer T1, and the second terminal S thereof is grounded, and the first terminal of the first secondary capacitor C11 is connected to the second terminal of the secondary side of the transformer T1, and the second terminal thereof is grounded.

As shown in fig. 7, the synchronous rectification control circuit includes a transformer T1, a first secondary capacitor C11, a second secondary capacitor C12, a third secondary capacitor C13, and any one of the synchronous rectification control devices IC 1. As shown in fig. 7, the first secondary capacitor C11 and the synchronous rectification control device IC1 are connected in series and then connected to the secondary side of the transformer T1, the second secondary capacitor C12 is connected between the power supply terminal VCC and the first terminal S of the synchronous rectification control device, and the third secondary capacitor C13 is connected between the frequency conversion terminal CVF and the second terminal D of the synchronous rectification control device. As further shown in fig. 7, the first terminal D of the synchronous rectification control device is grounded via the first secondary capacitor C11, the second terminal S is connected to the first terminal of the secondary side of the transformer T1, and the second terminal of the secondary side of the transformer T1 is grounded.

Those skilled in the art will appreciate that in the embodiments shown in fig. 6-7, the synchronous rectification control device described in any of the above embodiments may be used. To better illustrate the principles of the present invention, the primary side on decision module 400 shown in fig. 4, the power supply module 100 shown in fig. 5, and any one of the synchronous rectification control circuits shown in fig. 6-7 are used to explain the principles of the present invention as follows.

Firstly, the positive input terminal of the first comparator CMP1 receives a D-terminal voltage signal of the D-terminal of the synchronous rectification control device in the synchronous rectification control circuit, and when the primary side of the transformer T1 of the synchronous rectification control circuit is turned on, that is, the PWM signal is turned to high level, the D-terminal voltage signal is also turned to high level, the MOS transistor MP1 is turned off, the current source I1 pulls down the capacitor voltage of the second capacitor C2, the voltage VA at the base a point of the triode PNP1 will slowly drop, at this time, the voltage VB at the connection point B of the first resistor R1 and the second resistor R2 will drop along with the voltage VA, and when the PWM signal is changed from high to low. The secondary inductor of the transformer T1 connected to the synchronous rectification control device starts to flow current, and the voltage signal at the D terminal rapidly decreases from high, at which time the voltage VB is pulled down to a negative voltage by the first capacitor C1, and the second comparator CMP2 outputs a high level. At this time, the primary side on determination module 400 generates a primary side on determination signal indicating that the slope of the voltage at the D terminal decreases. At this time, the turn-on comparator 310 compares the D-terminal voltage signal with a first reference voltage signal (e.g., 0 voltage), and if the D-terminal voltage signal is determined to be less than the first reference voltage signal, it indicates that the D-terminal voltage signal is negative. At this time, when the logic module 500 receives the primary side turn-on determination signal indicating that the slope of the D-terminal voltage decreases and the first turn-on determination signal from the primary side turn-on determination module 400 at the same time, it generates a logic control signal for controlling the synchronous rectifier tube module 600 to turn on. Therefore, misoperation of the synchronous rectifier tube caused by resonance of the system in an intermittent mode can be effectively avoided, and the problems of serious heating and efficiency loss caused by insufficient power supply are avoided.

Further, when the synchronous rectifier 410 is turned on, the voltage signal at the voltage D becomes low level, the voltage VCVF at the frequency conversion terminal CVF of the synchronous rectifier control device will be clamped at about negative 0.7V by the transistor Q2, and the second secondary capacitor C12 discharges. When the primary side of the transformer T1 is conducted, the voltage signal at the D end is raised, the voltage at the CVF point of the third secondary capacitor C13 is clamped at VCC + VQ1, the voltage signal VD at the D end is pulled up to Vin/n + VC12, the voltage of the third secondary capacitor VC13 becomes Vin/n + VC12- (VCC + VQ1), and VCC is charged at the same time. The charge quantity Q of once charging every PWM switch is C12(Vin/n + VC12-VCC-VQ1)

Therefore, the synchronous rectification control circuit of the synchronous rectification control device can effectively avoid misoperation of the synchronous rectification tube caused by resonance when the system works in an intermittent mode by arranging the primary side switching-on judging module, thereby avoiding the problems of serious heating and efficiency loss caused by insufficient power supply.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims

1. A synchronous rectification control device, comprising: a power supply module (100), a reference module (200), a comparator module (300), a primary side opening judgment module (400), a logic module (500) and a synchronous rectifier tube module (600), wherein the reference module (200) generates a first reference signal and a second reference signal based on a voltage signal provided by the power supply module (100), the comparator module (300) generates a comparison decision signal based on the first reference signal, the second reference signal and a drain terminal voltage signal of a drain terminal of the synchronous rectifier tube module (600), the primary side turn-on determination module (400) generates a primary side turn-on determination signal based on the drain terminal voltage signal, the logic module (500) generates a logic control signal for controlling the synchronous rectifier tube module (600) to be switched on or switched off based on the comparison judgment signal and the primary side switching-on judgment signal; wherein the primary side open-circuit determination module (400) comprises a first comparator (CMP1), a second comparator (CMP2), a first switch tube (MP1), a second switch tube (PNP1), a third switch tube (NPN1), a first current source (I1), a second current source (I2), a first capacitor (C1), a second capacitor (C2), a first resistor (R1) and a second resistor (R2), a first input terminal of the first comparator (CMP1) receives a reference voltage signal, a second input terminal of the first comparator (CMP 6384) receives the drain terminal voltage signal, and an output terminal of the first comparator (CMP1) is connected to the first terminal of the first switch tube (MP1), a second terminal of the first switch tube (MP1) is connected to the first terminal of the second current source (I2) and the second terminal of the third switch tube (NPN1), a third terminal of the first switch tube (MP1) is grounded via the first current source (I1), and a first terminal of the second switch tube (PNP1) is connected to the third terminal of the first switch tube (MP1), a second terminal of the second switch tube (PNP1) is connected to the second terminal of the second current source (I2) and the first terminal of the third switch tube (NPN1), and a third terminal of the second switch tube (PNP1) is grounded; the third terminal of the third switch tube (NPN1) is grounded through the first resistor (R1) and the second resistor (R2), the first input terminal of the second comparator (CMP2) is grounded, the second input terminal is connected with the connection point of the first resistor (R1) and the second resistor (R2), and the output terminal is connected with the logic module (500), the second capacitor (C2) is connected between the first terminal of the second switch tube (PNP1) and the ground, and the first capacitor (C1) is connected between the second input terminal of the first comparator (CMP1) and the second input terminal of the second comparator (CMP 2).

2. The synchronous rectification control device of claim 1, wherein the comparator module (300) comprises an on comparator (301) and a first off comparator (302), the on comparator (301) generating a first on decision signal based on the drain terminal voltage signal and the first reference signal, the first off comparator (302) generating a first off decision signal based on the drain terminal voltage signal and the second reference signal.

3. The synchronous rectification control device of claim 2, wherein the logic module (500) generates an on logic control signal for controlling the synchronous rectifier tube module (600) to be turned on based on the first on determination signal and the primary side on determination signal, and generates an off logic control signal for controlling the synchronous rectifier tube module (600) to be turned off based on the first off determination signal.

4. The synchronous rectification control device of claim 3, wherein the reference module (200) further generates a third reference signal based on a voltage signal provided by the power supply module (100), and the comparator module (300) comprises a second turn-off comparator (303), and the second turn-off comparator (303) generates a second turn-off decision signal based on the drain terminal voltage signal and the third reference signal.

5. The synchronous rectification control device according to claim 4, wherein the logic module (500) generates a shutdown logic control signal for controlling the synchronous rectification pipe module (600) to shut down based on the first shutdown determination signal and/or the second shutdown determination signal.

6. The synchronous rectification control device according to any one of claims 1 to 5, wherein the power supply module (100) comprises a power supply unit and a clamping unit electrically connected with the power supply unit, the clamping unit comprises a fourth switching tube (Q1) and a fifth switching tube (Q2), the first end and the third end of the fifth switching tube (Q2) are grounded, the second end is connected with the second end and the first end of the fourth switching tube (Q1), the third end of the fourth switching tube (Q1) is connected with a power supply terminal (VCC) of the synchronous rectification control device, and the second end of the fourth switching tube (Q1) is connected with a frequency conversion terminal (CVF) of the synchronous rectification control device.

7. The synchronous rectification control device according to any one of claims 1 to 5, wherein the synchronous rectification module (600) comprises a driving unit (601), a clamping circuit (602) and a synchronous rectification tube (603), an input end of the driving unit (601) is connected with an output end of the logic module (500), an output end of the driving unit (601) is connected with a first end of the synchronous rectification tube (603), a second end of the synchronous rectification tube (603) is connected with a power supply end (VCC) of the synchronous rectification control device through the power supply module (100), a third end of the synchronous rectification control device is grounded, and the clamping circuit (602) is connected between the first end and the third end of the synchronous rectification tube (603); the second end of the synchronous rectifier tube (603) is the drain end of the synchronous rectifier tube module (600).

8. A synchronous rectification control circuit, comprising a transformer (T1), a first secondary side capacitor (C11), a second secondary side capacitor (C12), a third secondary side capacitor (C13) and the synchronous rectification control device as claimed in any one of claims 1 to 7, wherein the first secondary side capacitor (C11) and the synchronous rectification control device are connected in series and then connected to the secondary side of the transformer (T1), the second secondary side capacitor (C12) is connected between the power supply terminal (VCC) and the S terminal of the synchronous rectification control device, the third secondary side capacitor (C13) is connected between the variable frequency terminal (CVF) and the D terminal of the synchronous rectification control device, and the D terminal of the synchronous rectification control device is the drain terminal of the synchronous rectification module (600).

9. The synchronous rectification control circuit of claim 8, wherein the D terminal of the synchronous rectification control device is connected to the first terminal of the secondary side of the transformer (T1), the S terminal is grounded, the first terminal of the first secondary side capacitor (C11) is connected to the second terminal of the secondary side of the transformer (T1), and the second terminal is grounded; or the D end of the synchronous rectification control device is grounded through the first secondary capacitor (C11), the S end of the synchronous rectification control device is connected with the first secondary end of the transformer (T1), and the second secondary end of the transformer (T1) is grounded.