Synchronous rectification control device and isolated switching power supply circuit

Abstract

The embodiment of the utility model provides a synchronous rectification control device and an isolation type switching power supply circuit, the synchronous rectification control device comprises an over-temperature protection circuit, and the over-temperature protection circuit comprises a power supply module, a temperature detection module and an output control module; the power supply module is electrically connected with the temperature detection module and the output control module; the temperature detection module is used for detecting temperature information of the synchronous rectification control device; the output end of the temperature detection module is electrically connected with the output control module; the output end of the output control module can be electrically connected with a feedback control module or an upper computer of the isolation type switching power supply circuit, and the output control module is used for controlling the primary side current of the isolation type switching power supply circuit to be reduced at least according to the temperature information. The synchronous rectification control device has a reliable over-temperature protection function.

Description

Technical Field

[0001] The utility model relates to the technical field of power management, in particular to a synchronous rectification control device with temperature control and an isolated switching power supply circuit.

Background Art

[0002] The information provided in this part is only background information related to the present disclosure, and it is not necessarily prior art.

[0003] For a conventional power management chip, an over-temperature protection circuit (OTP circuit) is usually designed inside the chip. The working principle of the OTP circuit is that when it detects that the temperature inside the chip is higher than the set value, it turns off the drive output of the chip through the internal logic of the chip, making the whole system stop working, and then resumes working when the temperature drops, so as to prevent damage caused by overheating of the chip or potential safety hazards such as fire, thereby improving the reliability of the whole system.

[0004] However, in some chip applications, the function of the traditional OTP circuit will produce more adverse effects than without the OTP circuit. For example, Figure 1 As shown, for the control chip (SR chip) of the synchronous rectifier diode Qs, at high ambient temperatures, if the OTP circuit of the SR chip is protected due to overload, causing Qs to turn off, at this time, a large output overload current flows through the body diode of Qs to the output side. Since the voltage drop of the body diode of Qs is much higher than the voltage drop when Qs is conducting, the power consumption generated by Qs is greater, the temperature of the synchronous rectifier diode Qs is higher, and greater potential safety hazards are generated. In some synchronous rectification control chips, the OTP function is shielded or the over-temperature protection point is raised to a very high value. This method still has potential safety hazards for the reliability and safety of the system.

Content of the Utility Model

[0005] In view of this, the utility model provides a synchronous rectification control device and an isolated switching power supply circuit, which can perform effective protection actions when the temperature changes and improve the system safety.

[0006] The present application adopts the following technical solutions:

[0007] A synchronous rectification control device, applicable to an isolated switching power supply circuit, includes an over-temperature protection circuit, and the over-temperature protection circuit includes a power supply module, a temperature detection module, and an output control module; the power supply module is electrically connected to the temperature detection module and the output control module; the temperature detection module is used to detect the temperature information of the synchronous rectification control device; the output end of the temperature detection module is electrically connected to the output control module; the output end of the output control module can be electrically connected to the feedback control module of the isolated switching power supply circuit or an upper computer, and is used to control the reduction of the primary current of the isolated switching power supply circuit at least according to the temperature information.

[0008] When the synchronous rectification tube on the secondary side of this synchronous rectification control device is over-temperature, the primary current can be controlled to decrease (including controlling it to directly drop to 0), and further the current of the synchronous rectification tube on the secondary side also decreases, thereby realizing over-temperature protection of the synchronous rectification tube. In addition, further, in specific use, this over-temperature protection circuit can also replace an external temperature detection device to realize system over-temperature protection, which is beneficial to reducing system cost.

[0009] An isolated switching power supply circuit includes a primary unit, a secondary unit, and a feedback control unit; the primary unit includes a main switching tube; the secondary unit includes a synchronous rectification tube; the isolated switching power supply circuit further includes a primary control unit and the synchronous rectification control device as described above; the output end of the synchronous rectification control device is electrically connected to the feedback control unit or an upper computer; the output end of the feedback control unit is electrically connected to the input end of the primary control unit, and the output end of the primary control unit is electrically connected to the main switching tube.

[0010] The synchronous rectification control device of this isolated switching power supply circuit can control the primary current to decrease (including controlling it to directly drop to 0) when the synchronous rectification tube on the secondary side is over-temperature, and further the current of the synchronous rectification tube on the secondary side also decreases, thereby realizing over-temperature protection of the synchronous rectification tube, which is beneficial to improving the control safety of the circuit.

Description of the Drawings

[0011] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to these drawings, but they should fall within the protection scope of this application.

[0012] Figure 1 It is a schematic diagram of an isolated switching power supply circuit in the prior art;

[0013] Figure 2Schematic diagram of an isolated switching power supply circuit disclosed in this application;

[0014] Figure 3 Over-temperature protection circuit block diagram of a synchronous rectification control device disclosed in this application;

[0015] Figure 4 Another over-temperature protection circuit block diagram of a synchronous rectification control device disclosed in this application;

[0016] Figure 5 Another over-temperature protection circuit block diagram of a synchronous rectification control device disclosed in this application;

[0017] Figure 6 Another over-temperature protection circuit block diagram of a synchronous rectification control device disclosed in this application;

[0018] Figure 7 Another over-temperature protection circuit block diagram of a synchronous rectification control device disclosed in this application;

[0019] Figure 8 Schematic diagram of an over-temperature protection circuit of a synchronous rectification control device disclosed in this application;

[0020] Figure 9 Another schematic diagram of an over-temperature protection circuit of a synchronous rectification control device disclosed in this application;

[0021] Figure 10 Schematic diagram of an isolated switching power supply circuit disclosed in this application.

Specific embodiments

[0022] For a better understanding of the technical solutions of the present invention, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0023] It should be clear that the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0024] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms of "a", "the" and "said" used in the embodiments of the present invention and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise. Electrical connection includes direct electrical connection and indirect electrical connection.

[0025] It should be understood that the term "and / or" used herein is merely a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, both A and B exist simultaneously, and B exists alone. Additionally, the character " / " in this text generally indicates that the associated objects before and after are in an "or" relationship.

[0026] In one example, the synchronous rectifier diode Qs and the synchronous rectifier control chip SR shown in Figure 1 are encapsulated into one chip. In this way, since the heat generated by Qs will be quickly conducted to the synchronous rectifier control chip, the shielding over-temperature protection function mentioned in the background art will make the problems of system reliability and safety more prominent.

[0027] In another example, as shown in Figure 2 adding an external OTP circuit to the system will increase components, cost, and system complexity.

[0028] On this basis, the present application provides a synchronous rectifier control device. The synchronous rectifier control device includes an over-temperature protection circuit 1, which is applicable to an isolated switching power supply circuit. The over-temperature protection circuit 1 is as shown in Figure 3 and includes a power supply module 11, a temperature detection module 12, and an output control module 13. The power supply module 11 is electrically connected to the temperature detection module 12 and the output control module 13 for supplying power to the temperature detection module 12 and the output control module 13. The temperature detection module 12 is used to detect the temperature information of the synchronous rectifier control device, which can specifically be a triode, a temperature-sensitive resistor, a temperature detection chip, etc. The output end of the temperature detection module 12 is electrically connected to the output control module 13. The output end of the output control module 13 can be electrically connected to the feedback control module 2 of the isolated switching power supply circuit or an upper computer, and is used to control the reduction of the primary current of the isolated switching power supply circuit at least according to the temperature information. Controlling the reduction of the primary current includes turning off the primary circuit current or putting the system on standby so that the primary current directly drops to 0. The temperature sampling signal V output by the temperature detection signal T characterizes the temperature information. When the temperature information characterized by V T indicates that the synchronous rectifier control device has overheated, the output control module 13 generates a control signal V T according to V OTPO . This control signal V OTPO can control the feedback control module or indirectly control the primary control circuit through other systems (upper computer) to stop the primary system from working, completely turn off the primary circuit current, or limit the maximum current output by the system, so that the current of the secondary synchronous rectifier diode also decreases, realizing over-temperature protection of the synchronous rectifier diode. The feedback control module 2 can be Figure 1 or the feedback control and optocoupler isolation module shown in 2.

[0029] The synchronous rectification control device disclosed in this application can be used to improve the reliability and safety of the system. In one embodiment, the synchronous rectification control device can be packaged as an integrated circuit (i.e., IC). As Figure 10 shown, the over-temperature protection circuit 1 (OTP) is integrated in the IC. The over-temperature protection circuit in the IC can replace the external temperature detection device to achieve system over-temperature protection, which is beneficial to reducing the system cost. Of course, further, the synchronous rectifier tube can also be integrated in the IC. When the synchronous rectification control device and the synchronous rectifier tube are encapsulated in one IC package, the over-temperature protection circuit can more directly detect the temperature of the synchronous rectifier tube, which is beneficial to reducing the over-temperature risk of the secondary synchronous rectifier tube.

[0030] Further, in one embodiment, the output control module 13 includes a comparison circuit; the sampling terminal of the comparison circuit is electrically connected to the output terminal of the temperature detection module to receive the temperature sampling signal; the temperature sampling signal represents the temperature information of the synchronous rectifier tube; the reference terminal of the comparison circuit is electrically connected to the reference signal, and the reference signal represents the temperature value for entering over-temperature protection; the comparison circuit is used to turn off the primary main switch tube of the isolated switching power supply circuit through the feedback control module or the host computer when the temperature sampling signal is greater than or equal to the reference signal, so that the primary current directly decreases to 0.

[0031] In one embodiment, as Figure 8 shown, the synchronous rectification control device further includes a reference voltage generation circuit 131; the comparison circuit includes a comparator U1;

[0032] Among them, the reference generation circuit 131 includes a switching transistor PM11, a switching transistor PM12, a switching transistor PM13, an operational amplifier OPA, a resistor R11, a resistor R13, a resistor R14, a triode Q11, a triode Q12, a switching transistor PM13 and a resistor R15;

[0033] The temperature detection module 12 includes a switching transistor PM14 and a triode Q13;

[0034] Among them, switching transistors PM11, PM12, PM13, and PM14 form a current mirror; switching transistor PM11, resistor R11, and triode Q11 are connected in series between the output terminal VDD of the power supply module and the reference ground GND in sequence, and resistor R13 is connected in parallel with the series branch of resistor R11 and triode Q11; switching transistor PM12 and triode Q12 are connected in series between the output terminal VDD of the power supply module and the reference ground GND in sequence; switching transistor PM13 and resistor R15 are connected in series between the output terminal VDD of the power supply module and the reference ground GND in sequence; two input terminals of operational amplifier OPA are electrically connected to the common terminal of switching transistor PM11 and resistor R11 and the common terminal of switching transistor PM12 and triode Q12 respectively; the output terminal of operational amplifier OPA is electrically connected to the control terminal of switching transistor PM11; the voltage at the common terminal of switching transistor PM14 and resistor R15 is the reference voltage VREF, which represents the over-temperature protection value of the synchronous rectifier tube, and this point is connected to the reference terminal of comparator U1;

[0035] Switching transistor PM14 and triode Q13 are connected in series between the output terminal VDD of the power supply module and the reference ground GND; a signal Vbe (also V T ) representing temperature information is generated at the common terminal of switching transistor PM14 and triode Q13, and is connected to the sampling terminal of comparator U1.

[0036] In this embodiment, Q11 / 12 / 13 are all temperature sensing devices, PM11 / 12 / 13 / 14 are current mirrors, and the currents flowing through them are the same or proportional to each other. ICST1 = ΔVbe / R11 + Vbe / R13, Vbe is negatively correlated with temperature, ΔVbe is the difference between the Vbe of Q11 and the Vbe of Q12, and is positively correlated with temperature. By setting an appropriate ratio of R11 and R13, a current source independent of temperature can be obtained for ICST1; the Vbe of Q13 is a voltage negatively correlated with temperature. By setting different VREF voltages as the comparator reference, flag signals OTP_flag at different temperature points can be obtained. That is, by comparing the reference voltage VREF and the Vbe of Q13, an OTP_flag signal is generated to achieve over-temperature protection.

[0037] Furthermore, as Figure 4 shown, the comparison circuit is a hysteresis comparison circuit; in addition to the above-mentioned reference terminal, the hysteresis comparison circuit also has a second reference terminal, and the second reference terminal is electrically connected to the second reference signal V th2 , and the second reference signal V th2 represents the temperature value for exiting over-temperature protection; among them, the second reference signal V th2 is less than the reference signal V th1; The hysteresis comparison circuit is also used to control the primary main switch tube of the isolated switching power supply circuit to resume normal operation through the feedback control module or the host computer 3 when the temperature sampling signal is less than or equal to the second reference signal. In this embodiment, when V T ≥V th1 , it indicates that there is a risk of overheating of the synchronous rectifier tube. The output signal OTP_flag of the hysteresis comparison circuit is 1, and the system does not work; while when it is detected that V T ≤V th2 , it indicates that the overheating risk is lifted. The output signal OTP_flag of the hysteresis comparison circuit is 0, and the system resumes operation; thus, the temperature monitoring and overheating control of the synchronous rectifier tube are realized to ensure the safety of the system or circuit.

[0038] In order to enable the host computer to monitor the temperature change of the IC in real time and take corresponding protection measures or power reduction processing according to the temperature, the embodiment of the present application also provides an overheating protection circuit as shown in Figure 5 、 Figure 6 and Figure 7 ; Similarly, the temperature information can be represented by the temperature sampling signal V T sampled by the temperature detection module 12.

[0039] Figure 5 In TO (which is a specific implementation of the control signal V OTPO ); among them, the adjustment voltage V TO is positively correlated with the temperature information, and the temperature information is also positively correlated with the real-time temperature of the synchronous rectifier tube. In this embodiment, by changing the magnitude of the temperature sampling signal V T output by the temperature detection module 12 into the adjustment voltage V TO , further enabling the feedback control module 2 or the host computer 3 to control the primary current according to the magnitude of this adjustment voltage. Specifically, the larger the adjustment voltage, the smaller the controlled primary current, so that the synchronous rectifier tube current also decreases and the heat generation reduces, thereby realizing overheating protection. Specifically, the voltage adjustment circuit can be implemented by linear voltage adjustment, switching voltage adjustment or a voltage adjustment chip. The present application does not limit its specific form.

[0040] Figure 6 In TO (which is a specific implementation of the control signal V OTPO ). Among them, the adjustment duty ratio is positively correlated with the temperature information. The temperature information is also positively correlated with the real-time temperature of the synchronous rectifier tube. In this embodiment, by using the temperature sampling signal V output by the temperature detection module 12T is converted into a control signal including the duty cycle D TO , so that the feedback control module 2 or the host computer 3 controls the primary current according to the magnitude of the duty cycle D TO . Specifically, the larger the duty cycle D TO , the smaller the controlled primary current, so that the current of the synchronous rectifier tube also decreases and the heat generation is reduced, thereby realizing over-temperature protection. Specifically, the fixed-frequency duty cycle modulation circuit can be implemented by a duty cycle adjustment chip, digital devices, analog devices, or a combination of analog and digital. The present application does not limit its specific form.

[0041] Figure 7 , the output control module 13 includes a frequency adjustment circuit; the frequency adjustment circuit is used to generate an adjustment frequency f TO (which is a specific implementation of the control signal V OTPO ) according to the temperature information. Among them, the adjustment frequency is positively correlated with the temperature information, and the temperature information is also positively correlated with the real-time temperature of the synchronous rectifier tube. In this embodiment, by converting the temperature sampling signal V T output by the temperature detection module 12 into a control signal including the adjustment frequency f TO , so that the feedback control module 2 or the host computer 3 controls the primary current according to the magnitude of the adjustment frequency f TO . Specifically, the larger the adjustment frequency f TO , the smaller the controlled primary current, so that the current of the synchronous rectifier tube also decreases and the heat generation is reduced, thereby realizing over-temperature protection. Specifically, the adjustment frequency f TO can be implemented by a frequency adjustment chip, digital devices, analog devices, or a combination of analog and digital. The present application does not limit its specific form.

[0042] In one embodiment, as Figure 9 shown, the temperature detection module 12 includes a switching transistor PM21, a switching transistor PM22, an operational amplifier OPB, a resistor R21, a triode Q21, and a triode Q22; the switching transistor PM22 and the triode Q22 are connected in series between the output terminal VDD of the power supply module and the reference ground GND in sequence;

[0043] the switching transistor PM21, the resistor R21, and the triode Q21 are connected in series between the output terminal VDD of the power supply module and the reference ground GND in sequence; two input terminals of the operational amplifier OPB are electrically connected to the common terminal of the switching transistor PM21 and the resistor R21 and the common terminal of the switching transistor PM12 and the triode Q22 respectively; the output terminal of the operational amplifier OPB is electrically connected to the control terminal of the switching transistor PM21.

[0044] The frequency adjustment circuit 13 includes a switching transistor PM23, a switching transistor PM24, a switching transistor PM25, a switching transistor PM26, a switching transistor NM21, a switching transistor NM22, a capacitor C21, a capacitor C22, a resistor R22, a triode Q210, a comparator U21, a comparator U22, an RS flip-flop, and an inverter;

[0045] Among them, the switching transistors PM21, PM22, PM23, and PM24 form a current mirror; the switching transistor PM25 and the switching transistor NM21 are connected in series to form a first charge and discharge control branch for controlling the charge and discharge of the capacitor C21 according to the output signal of the Q terminal of the RS flip-flop; the capacitor C21 is connected in parallel with the switching transistor NM21; the switching transistor PM26 and the switching transistor NM22 are connected in series to form a second charge and discharge control branch for controlling the charge and discharge of the capacitor C22 according to the output signal of the inverter; the capacitor C22 is connected in parallel with the switching transistor NM22; the first charge and discharge control branch and the second charge and discharge control branch are connected in parallel between the output terminal of the switching transistor PM23 and the reference ground; the switching transistor PM24, the resistor R22, and the triode Q210 are connected in series between the output terminal VDD of the power supply module and the reference ground GND; the high-potential terminal of the capacitor C21 is electrically connected to the positive input terminal of the comparator U21, and the high-potential terminal of the capacitor C22 is electrically connected to the positive input terminal of the comparator U22; the negative input terminals of the comparator U21 and the comparator U22 are electrically connected and then connected to the common terminal of the switching transistor PM24 and the resistor R22; the output terminals of the comparator U21 and the comparator U22 are respectively electrically connected to the set terminal and the reset terminal of the RS flip-flop; the Q output terminal of the RS flip-flop is electrically connected to the input terminal of the inverter; the input terminal of the inverter is electrically connected to the control terminals of the switching transistor PM25 and the switching transistor NM21; the output terminal of the inverter is electrically connected to the control terminals of the switching transistor PM26 and the switching transistor NM22.

[0046] In this embodiment, the temperature detection module 12 converts the temperature information into relevant current information and then inputs it into the frequency adjustment circuit 13 through the current mirror to generate frequency information that changes with temperature; Q21 / 22 / 210 are temperature sensing devices, and PM21 / 22 / 23 / 24 are current mirrors, and the flowing currents are the same or proportional to each other; VREF = K * I1 * R22 + Vbe is a voltage reference independent of temperature; I1 = ΔVbe / R21, where ΔVbe is the difference between the Vbe of Q21 and the Vbe of Q22, which is positively correlated with temperature, and I1 is a current positively correlated with temperature; the charging period of I1 for C21 / C22 is half of the final output clock period, and the output signal VO2 of the inverter (i.e., V T ) The clock frequency is positively correlated with temperature. The host computer can control the primary current according to the clock frequency of VO2 to achieve over-temperature protection of the complex variable synchronous rectifier tube.

[0047] Based on the above embodiments, in order to further improve the accuracy and reliability of over-temperature protection, two over-temperature protection circuits as described above are designed on the synchronous rectification control device. As long as any one of the OTP circuits triggers protection, the system will be triggered to perform protection. In one embodiment, these two over-temperature protection circuits are both integrated within the integrated circuit package of the synchronous rectification control device.

[0048] As Figure 10 shown, an embodiment of the present application also provides an isolated switching power supply circuit, including a primary side unit P, a secondary side unit S, and a feedback control unit 21; the primary side unit includes a main switching transistor Qp; the feedback control unit 21 is used to implement feedback control and opto-isolation, and output a feedback signal to the primary side control unit 22 according to the secondary side sampling signal; the secondary side unit S includes a synchronous rectification transistor Qs; the isolated switching power supply circuit further includes a primary side control unit 22 and the synchronous rectification control device in any of the above embodiments; the output end of the synchronous rectification control device is electrically connected to the feedback control unit 21 or the host computer (in a specific embodiment, the host computer can be a USB PD controller 31); the output end of the feedback control unit 21 is electrically connected to the input end of the primary side control unit 22, and the output end of the primary side control unit 22 is electrically connected to the main switching transistor, and is used to control the main switching transistor according to the feedback signal and the control signal V generated by the over-temperature protection circuit 1 OTPO Not only can it achieve conventional circuit control, but also can effectively protect the synchronous rectification transistor against overcurrent, which is beneficial to improving control safety.

[0049] It should be noted that Figure 10 the flyback converter shown is only an example of the isolated switching power supply circuit. In practice, the above-mentioned synchronous rectification control device is applicable to the control of all synchronous rectification transistors on the secondary side, such as the synchronous rectification control of LLC converters, the synchronous rectification control of asymmetric flyback converters, the synchronous rectification control of forward continuation converters, etc.; the present application does not make any limitations in this regard.

[0050] The above-disclosed are only the preferred embodiments of the present application, and the scope of rights of the present application cannot be limited thereby. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of this specification still fall within the scope covered by the present application.

Claims

1. A synchronous rectification control device, suitable for an isolated switching power supply circuit, characterized in that: It includes an over-temperature protection circuit, which includes a power supply module, a temperature detection module and an output control module; the power supply module is electrically connected to the temperature detection module and the output control module; the temperature detection module is used to detect the temperature information of the synchronous rectification control device; the output end of the temperature detection module is electrically connected to the output control module; the output end of the output control module can be electrically connected to the feedback control module or the host computer of the isolated switching power supply circuit, and is used to control the primary current of the isolated switching power supply circuit to reduce according to at least the temperature information.

2. The synchronous rectification control device according to claim 1, characterized in that: The output control module includes a comparison circuit; the sampling end of the comparison circuit is electrically connected to the output end of the temperature detection module to receive a temperature sampling signal; the temperature sampling signal represents the temperature information; the reference end of the comparison circuit is electrically connected to a reference signal, and the reference signal represents the temperature value for entering the over-temperature protection; The comparison circuit is used to control the primary main switch tube of the isolated switching power supply circuit to be turned off through the feedback control module or the host computer when the temperature sampling signal is greater than or equal to the reference signal.

3. The synchronous rectification control device according to claim 2, characterized in that: The comparison circuit is a hysteresis comparison circuit; the second reference end of the hysteresis comparison circuit is electrically connected to a second reference signal, and the second reference signal represents the temperature value for exiting the over-temperature protection; wherein the second reference signal is less than the reference signal; the hysteresis comparison circuit is also used to control the primary main switch tube of the isolated switching power supply circuit to operate normally through the feedback control module or the host computer when the temperature sampling signal is less than or equal to the second reference signal.

4. The synchronous rectification control device according to claim 1, characterized in that: The output control module includes a voltage regulation control circuit; the voltage regulation control circuit is used to generate a regulation voltage according to the temperature information; the regulation voltage is positively correlated with the temperature information.

5. The synchronous rectification control device according to claim 1, characterized in that: The output control module includes a fixed-frequency duty cycle modulation circuit; the fixed-frequency duty cycle modulation circuit is used to generate an adjusted duty cycle according to the temperature information; the adjusted duty cycle is positively correlated with the temperature information.

6. The synchronous rectification control device according to claim 1, characterized in that: The output control module includes a frequency adjustment circuit; the frequency adjustment circuit is used to generate an adjustment frequency according to the temperature information; the adjustment frequency is positively correlated with the temperature information.

7. The synchronous rectification control device according to claim 2, characterized in that: It also includes a reference voltage generating circuit; the comparison circuit includes a comparator U1; The reference generation circuit includes a switch tube PM11, a switch tube PM12, a switch tube PM13, an operational amplifier OPA, a resistor R11, a resistor R13, a resistor R14, a transistor Q11, a transistor Q12, a switch tube PM13 and a resistor R15; The temperature detection module includes a switch tube PM14 and a transistor Q13; Among them, the switch tube PM11, the switch tube PM12, the switch tube PM13 and the switch tube PM14 are current mirrors; the switch tube PM11, the resistor R11 and the transistor Q11 are connected in series between the output end of the power supply module and the reference ground in sequence, and the resistor R13 is connected in parallel with the series branch of the resistor R11 and the transistor Q11; the switch tube PM12 and the transistor Q12 are connected in series between the output end of the power supply module and the reference ground in sequence; the switch tube PM13 and the resistor R15 are connected in series between the output end of the power supply module and the reference ground in sequence; the two input ends of the operational amplifier OPA are electrically connected to the common end of the switch tube PM11 and the resistor R11 and the common end of the switch tube PM12 and the transistor Q12 respectively; the output end of the operational amplifier OPA is electrically connected to the control end of the switch tube PM11; the common end voltage of the switch tube PM14 and the resistor R15 is a reference voltage, which is connected to the reference end of the comparator U1; The switch tube PM14 and the transistor Q13 are connected in series between the output end of the power supply module and the reference ground in sequence; the common end of the switch tube PM14 and the transistor Q13 generates the temperature information and is connected to the sampling end of the comparator U1.

8. The synchronous rectification control device according to claim 6, characterized in that: The temperature detection module includes a switch tube PM21, a switch tube PM22, an operational amplifier OPB, a resistor R21, a transistor Q21 and a transistor Q22; the switch tube PM22 and the transistor Q22 are connected in series between the output end of the power supply module and the reference ground in sequence; The switch tube PM21, the resistor R21, and the transistor Q21 are connected in series between the output end of the power supply module and the reference ground in sequence; the two input ends of the operational amplifier OPB are electrically connected to the common end of the switch tube PM21 and the resistor R21 and the common end of the switch tube PM12 and the transistor Q22 respectively; the output end of the operational amplifier OPB is electrically connected to the control end of the switch tube PM21; The frequency adjustment circuit includes a switch tube PM23, a switch tube PM24, a switch tube PM25, a switch tube PM26, a switch tube NM21, a switch tube NM22, a capacitor C21, a capacitor C22, a resistor R22, a transistor Q210, a comparator U21, a comparator U22, an RS trigger and an inverter; the switch tube PM21, the switch tube PM22, the switch tube PM23 and the switch tube PM24 are current mirrors; the switch tube PM25 is connected in series with the switch tube NM21 to form a first charge and discharge control branch; the capacitor C21 is connected in parallel with the switch tube NM21; the switch tube PM26 is connected in series with the switch tube NM22 to form a second charge and discharge control branch; the capacitor C22 is connected in parallel with the switch tube NM22; the first charge and discharge control branch and the second charge and discharge control branch are connected in parallel between the output end of the above-mentioned switch tube PM23 and the reference ground The switch tube PM24, the resistor R22 and the transistor Q210 are connected in series between the output end of the power supply module and the reference ground; the high potential end of the capacitor C21 is electrically connected to the positive input end of the comparator U21, and the high potential end of the capacitor C22 is electrically connected to the positive input end of the comparator U22; the reverse input ends of the comparator U21 and the comparator U22 are electrically connected to the common end of the switch tube PM24 and the resistor R22; the output ends of the comparator U21 and the comparator U22 are electrically connected to the set end and the reset end of the RS trigger respectively; the output end of the RS trigger is electrically connected to the input end of the inverter; the input end of the inverter is electrically connected to the control end of the switch tube PM25 and the switch tube NM21; the output end of the inverter is electrically connected to the control end of the switch tube PM26 and the switch tube NM22.

9. The synchronous rectification control device according to any one of claims 1 to 8, characterized in that: The temperature detection module includes a triode or a temperature sensitive resistor; or, The synchronous rectification control device includes two over-temperature protection circuits; or, The synchronous rectification control device is packaged as an integrated circuit, and the over-temperature protection circuit and / or the synchronous rectification tube are integrated into the integrated circuit.

10. An isolated switching power supply circuit, characterized in that: It includes a primary unit, a secondary unit and a feedback control unit; the primary unit includes a main switch tube; the secondary unit includes a synchronous rectifier tube; the isolated switching power supply circuit also includes a primary control unit and a synchronous rectification control device as described in any one of claims 1-9; the output end of the synchronous rectification control device is electrically connected to the feedback control unit or the host computer; the output end of the feedback control unit is electrically connected to the input end of the primary control unit, and the output end of the primary control unit is electrically connected to the main switch tube.

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