CN211018252U

CN211018252U - Switching power supply over-temperature protection circuit and switching power supply

Info

Publication number: CN211018252U
Application number: CN201922242430.5U
Authority: CN
Inventors: 刘政
Original assignee: SHENZHEN LONGYUN LIGHTING ELECTRIC APPLIANCES CO Ltd
Current assignee: SHENZHEN LONGYUN LIGHTING ELECTRIC APPLIANCES CO Ltd
Priority date: 2019-12-13
Filing date: 2019-12-13
Publication date: 2020-07-14
Anticipated expiration: 2029-12-13

Abstract

The utility model discloses a switching power supply excess temperature protection circuit and switching power supply, switching power supply excess temperature protection circuit includes rectifier module, temperature detection module, partial pressure module, filtering module and protection module; the rectifying module rectifies the alternating-current voltage and outputs the direct-current voltage to the voltage dividing module through the temperature detection module, the voltage dividing module divides the direct-current voltage for sampling, and the filtering module outputs the sampled voltage to the protection module; the temperature detection module detects the current working temperature of the control module, controls the sampling voltage to be greater than the threshold voltage of the protection module when the current working temperature is greater than the preset temperature, and controls the sampling voltage to be less than the threshold voltage when the current working temperature is less than the preset temperature; the protection module is used for conducting when the sampling voltage is larger than the threshold voltage and controlling the control module to be closed; the protection module is also used for closing when the sampling voltage is smaller than the threshold voltage, and controlling the control module to restart, so that the over-temperature protection of the switching power supply is realized, and the safety is improved.

Description

Switching power supply over-temperature protection circuit and switching power supply

Technical Field

The utility model relates to a switching power supply field, in particular to switching power supply excess temperature protection circuit and switching power supply.

Background

In the middle of the power supply work, when the working voltage or the environmental temperature is abnormal, the temperature of components in the power supply product is higher, and the condition that the service life of the product is reduced or even the product is damaged can occur after the power supply product lasts for a long time. Some chips on the market are integrated with an over-temperature protection function, the over-temperature protection threshold value of the chips is basically over 120 ℃, but the chips are not integrated with high-power consumption devices, the heating is not serious, the control is only carried out by detecting the temperature on a PCB (printed Circuit Board), the chips are sensitive, and the chips are far away from a heating source and an interference source when the product is designed, so the significance of the over-temperature protection function is not great; when the temperature of some components such as a switch tube and an electrolytic capacitor is too high, the condition that the product is damaged or the service life is reduced can occur due to the fact that the chip cannot detect the component, and the power utilization safety of the product cannot be guaranteed.

Thus, the prior art has yet to be improved and enhanced.

SUMMERY OF THE UTILITY MODEL

In view of the foregoing prior art's weak point, the utility model aims to provide a switching power supply excess temperature protection circuit and switching power supply can effectually directly detect control chip's in the switch unit power current operating temperature, realizes the excess temperature protection to control chip, and sensitivity is high and circuit structure is simple.

In order to achieve the purpose, the utility model adopts the following technical proposal:

a switching power supply over-temperature protection circuit is connected with a control module of a switching power supply and comprises a rectification module, a temperature detection module, a voltage division module, a filtering module and a protection module; the rectifying module is used for rectifying alternating-current voltage and outputting direct-current voltage to the voltage dividing module through the temperature detection module, and the voltage dividing module is used for dividing and sampling the direct-current voltage and outputting sampling voltage to the filtering module; the filtering module is used for filtering the sampling voltage and outputting the filtered sampling voltage to the protection module; the temperature detection module is used for detecting the current working temperature of the control module, controlling the sampling voltage to be larger than the threshold voltage of the protection module when the current working temperature is larger than a preset temperature, and controlling the sampling voltage to be smaller than the threshold voltage when the current working temperature is smaller than the preset temperature; the protection module is used for conducting when the sampling voltage is larger than the threshold voltage and controlling the control module to be closed; the protection module is further used for closing when the sampling voltage is smaller than the threshold voltage, and controlling the control module to restart.

In the switching power supply over-temperature protection circuit, the protection module comprises a reference voltage source, the cathode of the reference voltage source is connected with the control module, the anode of the reference voltage source is grounded, and the reference end of the reference voltage source is connected with the filtering module and the voltage division module.

In the switching power supply over-temperature protection circuit, the rectification module comprises a first diode, the anode of the first diode is connected with the alternating-current voltage input end, and the cathode of the first diode is connected with the temperature detection module.

In the switching power supply over-temperature protection circuit, the temperature detection module comprises a thermistor, one end of the thermistor is connected with the negative electrode of the first diode, and the other end of the thermistor is connected with the voltage division module.

In the switching power supply over-temperature protection circuit, the voltage division module comprises a first resistor, a second resistor, a third resistor and a fourth resistor; one end of the first resistor is connected with the other end of the thermistor, the other end of the first resistor is connected with one end of the third resistor, one end of the fourth resistor and the filtering module through the second resistor, and the other end of the third resistor and the other end of the fourth resistor are both grounded.

In the switching power supply over-temperature protection circuit, the filtering module comprises a first capacitor, one end of the first capacitor is connected with one end of the third resistor, one end of the fourth resistor and the protection module, and the other end of the first capacitor is grounded.

A switching power supply comprises the switching power supply over-temperature protection circuit, and further comprises a rectifier bridge, a control module, a PFC voltage output module and an LL C resonance module, wherein the control module comprises a PFC control unit and a LL C control unit, the switching power supply over-temperature protection circuit is used for controlling the control module to be closed to carry out over-temperature protection according to the change of the current working temperature of the control module, the rectifier bridge is used for rectifying alternating-current voltage and then outputting direct-current voltage to the PFC control unit and the LL C control unit, the PFC control unit is used for controlling the PFC voltage output module to output PFC voltage to the LL C resonance module, and the LL C control unit is used for controlling the LL C resonance module to convert the PFC voltage into preset output voltage to be output to a load.

In the switching power supply, the PFC control unit comprises a first control chip, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, a twelfth resistor, a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, a sixteenth resistor, a seventeenth resistor, an eighteenth resistor, a nineteenth resistor, a twentieth resistor, a twenty-first resistor, a twenty-second resistor, a twenty-third resistor, a third diode, a second capacitor, a third capacitor, a fourth capacitor and a seventh capacitor; one end of the twenty-first resistor is connected with the rectifier bridge, the other end of the twenty-first resistor is connected with one end of the twentieth resistor through the twenty-second resistor and the nineteenth resistor, the other end of the twentieth resistor is connected with one end of the twenty-third resistor, one end of the seventh capacitor and the 3 rd pin of the first control chip, and the other ends of the twenty-third resistor and the seventh capacitor are grounded; one end of the second capacitor and one end of the sixth resistor are connected with a pin 4 of the first control chip, the other end of the sixth resistor and one end of the fifth resistor are connected with the PFC voltage output module, and the other end of the fifth resistor and the other end of the second capacitor are both grounded; one end of the sixteenth resistor is connected with the PFC voltage output module, the other end of the sixteenth resistor is connected with one end of the twelfth resistor through the fifteenth resistor, the fourteenth resistor and the thirteenth resistor, the other end of the twelfth resistor is connected with one end of the third capacitor, one end of the fourth capacitor, the 1 st pin of the first control chip, one end of the seventeenth resistor and one end of the eighteenth resistor, the other end of the third capacitor is connected with the 2 nd pin of the first control chip through the seventh resistor, the other end of the fourth capacitor is connected with the 2 nd pin of the first control chip, and the other ends of the seventeenth resistor and the eighteenth resistor are grounded; the negative electrode of the third diode and one end of the ninth resistor are both connected with the pin 7 of the first control chip, and the positive electrode of the third diode and the other end of the ninth resistor are connected with the PFC voltage output module through the eighth resistor; and the 5 th pin of the first control chip is connected with the PFC voltage output module through the tenth resistor.

In the switching power supply, the PFC voltage output module comprises a first transformer, an MOS (metal oxide semiconductor) tube, a fifth diode and a fourteenth capacitor; a 4 th pin of the first transformer is connected with the rectifier bridge, a 1 st pin of the first transformer is grounded, a 3 rd pin of the first transformer is connected with the anode of the fifth diode and the drain of the MOS tube, and a 2 nd pin of the first transformer is connected with the PFC control unit; the grid electrode of the MOS tube is connected with the PFC control unit, and the source electrode of the MOS tube is connected with the PFC control unit; and the cathode of the fifth diode is connected with one end of the fourteenth capacitor, and the other end of the fourteenth capacitor is grounded.

In the switching power supply, the LL C resonance module comprises a second transformer, a first inductor and a sixth capacitor, one end of the first inductor is connected with the PFC voltage output module, the other end of the first inductor is connected with a 1 st pin of the second transformer, one end of the sixth capacitor is connected with the LL C control unit, and the other end of the sixth capacitor is connected with a 2 nd pin of the second transformer.

Compared with the prior art, the utility model provides a switching power supply excess temperature protection circuit and switching power supply, switching power supply excess temperature protection circuit includes rectifier module, temperature detection module, partial pressure module, filtering module and protection module; the rectifying module is used for rectifying alternating-current voltage and outputting direct-current voltage to the voltage dividing module through the temperature detection module, and the voltage dividing module is used for dividing and sampling the direct-current voltage and outputting sampling voltage to the filtering module; the filtering module is used for filtering the sampling voltage and outputting the filtered sampling voltage to the protection module; the temperature detection module is used for detecting the current working temperature of the control module, controlling the sampling voltage to be larger than the threshold voltage of the protection module when the current working temperature is larger than a preset temperature, and controlling the sampling voltage to be smaller than the threshold voltage when the current working temperature is smaller than the preset temperature; the protection module is used for conducting when the sampling voltage is larger than the threshold voltage and controlling the control module to be closed; the protection module is also used for closing when the sampling voltage is smaller than the threshold voltage, controlling the control module to restart, further realizing the over-temperature protection of the switching power supply, improving the safety of the switching power supply, and automatically starting the switching power supply after the temperature is recovered to be normal.

Drawings

Fig. 1 is a block diagram of a switching power supply according to the present invention;

fig. 2 is a structural diagram of the over-temperature protection circuit of the switching power supply provided by the present invention;

fig. 3 is a schematic circuit diagram of the over-temperature protection circuit of the switching power supply provided by the utility model.

Detailed Description

The utility model provides a switching power supply excess temperature protection circuit and switching power supply can effectively detect control chip's current operating temperature in the switch unit power, realizes having improved switching power supply's security to control chip's excess temperature protection, and can be at the normal back automatic start switching power supply of temperature recovery.

In order to make the objects, technical solutions and effects of the present invention clearer and clearer, the following description of the present invention will refer to the accompanying drawings and illustrate embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the invention.

Referring to fig. 1, the switching power supply of the present invention includes a switching power supply over-temperature protection circuit 10, a rectifier bridge 20, a control module 30, a PFC voltage output module 40, and an LL C resonant module 50, where the control module 30 includes a PFC control unit 31 and a LL C control unit 32, the switching power supply over-temperature protection circuit 10 is respectively connected to the PFC control unit 31 and the LL C control unit 32, the PFC control unit 31 is connected to the PFC voltage output module 40, the PFC voltage output module 40 is further connected to the LL C resonant module 50, and the LL C resonant module 50 is further connected to the LL C control unit 32, where the rectifier bridge 20 is a prior art, and thus detailed descriptions of a specific circuit connection structure thereof are omitted in this embodiment.

The switching power supply over-temperature protection circuit 10 is configured to control the PFC control unit 31 and the LL C control unit 32 to be turned off for over-temperature protection according to changes of current operating temperatures of the PFC control unit 31 and the LL C control unit 32, the rectifier bridge 20 is configured to rectify an alternating current voltage and output the rectified direct current voltage to the PFC control unit 31 and the LL C control unit 32, respectively supply power to the PFC control unit 31 and the LL C control unit 32 to ensure normal operation of the PFC control unit 31 and the LL C control unit 32, the PFC control unit 31 is configured to control the PFC voltage output module 40 to output a PFC voltage to the LL C resonance module 50, the LL C control unit 32 is configured to control the LL C resonance module 50 to convert the PFC voltage into a preset output voltage to a load and provide power for the load, and the switching power supply over-temperature protection circuit 10 can effectively and directly detect the current operating temperatures of the PFC control unit 31 and the LL C control unit 32 to realize over-temperature protection of the PFC control unit 31 and the LL C control unit 32.

In specific implementation, referring to fig. 2, the switching power supply over-temperature protection circuit 10 includes a rectification module 100, a temperature detection module 200, a voltage division module 300, a filtering module 400 and a protection module 500, where the rectification module 100 is connected to an alternating current power supply and the temperature detection module 200, the temperature detection module 200 is further connected to the filtering module 400 through the voltage division module 300, the filtering module 400 is further connected to the protection module 500, and the protection module 500 is respectively connected to the PFC control unit 31 and the LL C control unit 32.

The rectifier module 100 is configured to output a dc voltage to the voltage divider module 300 through the temperature detection module 200 after rectifying an ac voltage, the voltage divider module 300 is configured to divide and sample the dc voltage and output a sampled voltage to the filter module 400, the filter module 400 is configured to filter the sampled voltage and output the filtered sampled voltage to the protection module 500, eliminate an interference signal in the sampled voltage to avoid a malfunction of the protection module 500, the temperature detection module 200 is configured to detect a current working temperature of the control module, and when the current working temperature is greater than a preset temperature, the sampled voltage is greater than a threshold voltage of the protection module 500, and when the current working temperature is less than the preset temperature, the sampled voltage is less than the threshold voltage, the protection module 500 is configured to turn on when the sampled voltage is greater than the threshold voltage, so that the control module is turned off, and when the sampled voltage is less than the threshold voltage, the protection module 500 is further configured to turn off, so that the control module is turned on again, and the power over-temperature protection circuit 10 effectively and directly detects an over-temperature of the PFC control unit 31 and LL, thereby avoiding a disadvantage that a power supply over-temperature of a product cannot be detected safely.

Further, referring to fig. 3, the protection module 500 includes a reference voltage source S1, a cathode of the reference voltage source S1 is connected to the PFC control unit 31 and the LL C control unit 32, an anode of the reference voltage source S1 is grounded, a reference terminal of the reference voltage source S1 is connected to the filter module 400 and the voltage dividing module 300, when the sampled voltage output by the filter module 400 does not reach a threshold voltage, the reference voltage source S1 is turned off, the PFC control unit 31 and the LL C control unit 32 are controlled to continue to operate, when the sampled voltage is greater than the threshold voltage, the reference voltage source S1 is turned on, the PFC control unit 31 and the LL C control unit 32 are controlled to turn off and stop operating, and the switching power supply stops operating, a current operating temperature corresponding to the current operating temperature is also reduced, when the current temperature is reduced below a preset temperature, the sampled voltage output by the filter module 400 is smaller than the threshold voltage, the voltage source S1 is turned off, so that the PFC control unit 400 and the reference control unit 31 and the LL and the PFC control unit 31 and the normal control unit 31 and the over-start-up and the PFC control unit 5832 automatically.

Further, the rectifying module 100 includes a first diode D1, an anode of the first diode D1 is connected to an ac voltage input end, a cathode of the first diode D1 is connected to the temperature detecting module 200, and the first diode D1 rectifies the ac voltage and then outputs the dc voltage to the temperature detecting module 200, so that the voltage dividing module 300 can obtain the sampled voltage.

Further, the temperature detecting module 200 includes a thermistor NTC1, one end of the thermistor NTC1 is connected to the negative electrode of the first diode D1, the other end of the thermistor NTC1 is connected to the voltage dividing module 300, after the PFC control unit 31 and the LL C control unit 32 operate, the difference of the current operating temperature may cause the difference of the resistance value of the thermistor NTC1, and further change the voltage dividing value of the voltage dividing module 300, so that the magnitude of the sampling voltage changes, thereby achieving the purpose of temperature detection.

Further, the voltage dividing module 300 includes a first resistor R1, a second resistor R2, a third resistor R3 and a fourth resistor R4; one end of the first resistor R1 is connected with the other end of the thermistor NTC1, the other end of the first resistor R1 is connected with one end of the third resistor R3, one end of the fourth resistor R4 and the filtering module 400 through the second resistor R2, the third resistor R3 and the other end of the fourth resistor R4 are all grounded, and the voltage output by the temperature detection module 200 is sampled by the first resistor R1, the second resistor R2, the third resistor R3 and the fourth resistor R4 to obtain the sampling voltage so as to judge whether to trigger over-temperature protection according to the sampling voltage.

Further, the filtering module 400 includes a first capacitor C1, one end of the first capacitor C1 is connected to one end of the third resistor R3, one end of the fourth resistor R4 and the protection module 500, the other end of the first capacitor C1 is grounded, when the resistance value of the NTC1 changes with the current operating temperature, the voltage of the first capacitor C1 changes with the change of the operating temperature, the higher the current operating temperature is, the higher the voltage of the first capacitor C1 is, when the voltage of the first capacitor C1, that is, the sampling voltage is greater than the threshold voltage, the reference voltage source S1 is turned on, the power supply voltages of the PFC control unit 31 and the LL C control unit 32 are pulled down to stop operating, and then when the current operating temperature decreases, the resistance value of the NTC1 correspondingly increases, the voltage of the first capacitor C1 gradually decreases to be lower than the threshold voltage, so that the voltage source S1 is turned off, the switch resumes operating again, and the protection purpose of the product automatically resumes after the current operating temperature decreases.

Furthermore, with reference to fig. 3, the PFC control unit 31 includes a first control chip U, a fifth resistor R, a sixth resistor R, a seventh resistor R, an eighth resistor R, a ninth resistor R, a tenth resistor R, a twelfth resistor R, a thirteenth resistor R, a fourteenth resistor R, a fifteenth resistor R, a sixteenth resistor R, a seventeenth resistor R, an eighteenth resistor R, a nineteenth resistor R, a twentieth resistor R, a twenty-first resistor R, a twenty-second resistor R, a twenty-third resistor R, a third diode D, a second capacitor C, a third capacitor C, a fourth capacitor C and a seventh capacitor C, one end of the twenty-first resistor R is connected to the rectifier bridge 20, the other end of the twenty-first resistor R is connected to one end of the twenty-third resistor R, one end of the seventh capacitor C and one end of the first control chip R through the twenty-second resistor R and the nineteenth resistor R, the other end of the twenty-third resistor R is connected to the output voltage of the PFC module through the first resistor R, the resistor R652, the resistor R is connected to the sixth resistor R, the resistor R is connected to the output voltage of the PFC module, the PFC module is connected to the output voltage control module through the eighth resistor R, the resistor R is connected to the eighth resistor R, the sixth resistor R, the resistor R is connected to the sixth resistor R to the output terminal of the PFC module, the output module, the PFC module, the eighth resistor R is connected to the eighth resistor R, the output terminal of the eighth resistor R, the PFC module, the eighth resistor R40, the eighth resistor R is connected to the eighth resistor R, the resistor R is connected to the resistor R, the resistor R module, the resistor R is connected to the resistor R, the resistor R to the resistor R, the resistor R40, the resistor R is connected to the resistor R, the resistor R to the resistor R, the resistor R to the resistor R, the.

Specifically, a voltage sampling signal obtained by a resistor divider formed by the sixteenth resistor R16, the fifteenth resistor R15, the fourteenth resistor R14, the thirteenth resistor R13, the twelfth resistor R12, the seventeenth resistor R17 and the eighteenth resistor R18 is connected to the 1 st pin of the first control chip U1 to obtain a preset PFC output voltage value, and the 1 st pin of the first control chip U1 further forms a compensation network between the seventh resistor R7 and the 2 nd pin of the first control chip U1 through the third capacitor C3, the fourth capacitor C4 and the seventh resistor C7 to obtain a stable voltage control loop and ensure a high power factor and low total harmonic distortion; a resistor voltage divider consisting of the twenty-first resistor R21, the twenty-second resistor R22, the first nineteen resistor R19, the twentieth resistor R20 and the twenty-third resistor R23 is connected to the 3 rd pin of the first control chip U1 through being connected to the rectified mains voltage, so as to obtain a sinusoidal reference signal of a current loop; the 4 th pin of the first control chip U1 is used for detecting the current flowing through the MOS transistor M1 through a connected fifth resistor R5 and forming a voltage signal, and the voltage signal is compared with a sinusoidal reference signal generated by a multiplier inside the first control chip U1 through the sixth resistor R6 and the second capacitor C2 to control the on and off of the MOS transistor M1; a pin 5 of the first control chip U1 is an input terminal for zero current detection, a negative edge signal can trigger the MOS transistor M1 to be turned on through a tenth resistor R10, a pin 6 of the first control chip U1 is grounded, and a current loop is provided for an internal signal current and a gate driver of the first control chip U1; the 7 th pin of the first control chip U1 is the output end of the internal gate driver of the first control chip U1, and the MOS transistor M1 is provided with a driving signal through the third diode D3, the ninth resistor R9 and the eighth resistor R8 to control the on and off of the MOS transistor M1.

Further, the PFC voltage output module 40 includes a first transformer T1, a MOS transistor M1, a fifth diode D5, and a fourteenth capacitor C14; the 4 th pin of the first transformer T1 is connected to the rectifier bridge 20, the 1 st pin of the first transformer T1 is grounded, the 3 rd pin of the first transformer T1 is connected to the anode of the fifth diode D5 and the drain of the MOS transistor M1, and the 2 nd pin of the first transformer T1 is connected to the PFC control unit 31; the gate of the MOS transistor M1 is connected to the PFC control unit 31, and the source of the MOS transistor M1 is connected to the PFC control unit 31; a cathode of the fifth diode D5 is connected to one end of the fourteenth capacitor C14, and the other end of the fourteenth capacitor C14 is grounded. After the first control chip U1 is started to work, the MOS transistor M1 is controlled to be turned on and off, when the MOS transistor M1 is turned on, the electric energy is converted into magnetic energy to be stored in the first transformer T1, and when the MOS transistor M1 is turned off, the magnetic energy is converted into electric energy and charges the fourteenth capacitor C14 together with rectified mains supply through the fifth diode D5, so that the boosting function of the PFC voltage output module 40 is completed.

Further, referring to fig. 3, the LL C resonant module 50 includes a second transformer T2, a first inductor L1, and a sixth capacitor C6, wherein one end of the first inductor L1 is connected to the PFC voltage output module 40, the other end of the first inductor L1 is connected to the 1 st pin of the second transformer T2, one end of the sixth capacitor C6 is connected to the LL C control unit 32, the other end of the sixth capacitor C6 is connected to the 2 nd pin of the second transformer T2, and a resonant network is formed by the second transformer T2, the first inductor L1, and the sixth capacitor C6 to provide a required output voltage, i.e., a preset output voltage, to the load according to the PFC voltage.

Further, the periphery of the first control chip U1 is also provided with a corresponding peripheral circuit, and it should be noted that the peripheral circuit of the first control chip U1 is the prior art, and therefore, details of a specific connection manner of the peripheral circuit of the first control chip U1 are not described in this embodiment; a twenty-fourth resistor R24, a twenty-fifth resistor R25, a twenty-sixth resistor R26 and an eighth capacitor C8 which are connected in series with one another are connected to the 8 th pin of the first control chip U1, starting current is provided for the first control chip U1 through the twenty-fourth resistor R24, the twenty-fifth resistor R25 and the twenty-sixth resistor R26, and the first control chip U1 starts to work when the voltage on the eighth capacitor C8 reaches 12.5V; a second diode D2, a first voltage-stabilizing diode ZD1, a fifth capacitor C5 and an eleventh resistor R11 are further connected to the pin 8 of the first control chip U1, and the voltage on the auxiliary winding of the first transformer T1 is reduced by the eleventh resistor R11 and the fifth capacitor C5 and is clamped by the first voltage-stabilizing diode ZD1 to provide working energy after starting for the first control chip U1; the 8 th pin of the first control chip U1 is further connected to the cathode of the reference voltage source S1, and when the reference voltage source S1 is turned on, the voltage of the 8 th pin is pulled down to stop the operation of the first control chip U1, thereby implementing over-temperature protection.

Further, with reference to fig. 3, the LL C control unit 32 includes a second control chip U2, a corresponding peripheral circuit is disposed on a periphery of the second control chip U2, it is to be noted that the peripheral circuit of the second control chip U2 is the prior art, a specific connection mode of the peripheral circuit is not described in this embodiment, the model of the second control chip U2 in this embodiment is RED2601, it is needless to say that in other embodiments, other second control chips U2 having the same function may also be selected, which is not limited in this embodiment, the first pin of the second control chip U2 is connected to a twenty-seventh resistor R2, a twenty-eighth resistor R2, a twenty-ninth resistor R2, a ninth capacitor C2, a fourth diode D2 and a tenth capacitor C2, the twenty-eighth resistor R2, the ninth capacitor C2, the seventh resistor R2 and the ninth capacitor C2 are connected in parallel to the seventh capacitor C2, the twenty-ninth capacitor C2, the twenty-eighth resistor R2 is connected to the fifth capacitor C2, the thirty-fifth capacitor C2, the resistor R2 and the fifth capacitor C2 is connected to the fifth capacitor C2, the thirty-fifth capacitor C2, the resistor R2 is connected to the thirty-fifth capacitor C2, the switch 2, the resistor R2 is connected to the thirty-fifth capacitor C2, the resistor R2 is connected to the resistor R2, the thirty-fifth capacitor C2, the resistor R2 is connected to the resistor C2, the resistor C2 is connected to the resistor R2, the resistor C2 is connected to the resistor C2, the resistor C2 is connected to the resistor C2, the resistor C2 is connected in series connected in parallel to the resistor C2, the resistor C2.

Furthermore, a pin 6 of the second control chip U2 is connected to the thirty-second resistor R32, the twelfth capacitor C12, the second zener diode ZD2, the thirty-third resistor R33 and the thirty-fourth resistor R34, wherein a cathode of the second zener diode ZD2 is connected to a cathode of the reference voltage source S1, the pin 6 is a power pin, after the first control chip U1 enters an operating state, the twelfth capacitor C12 is charged by the eighth capacitor C8 through the second zener diode ZD2 and the thirty-second resistor R32 to start up, and after the second control chip U2 starts up to enter the operating state, power is supplied by the primary side auxiliary winding through the fourth diode D4, the tenth capacitor C10, the thirty-third resistor R33 and the thirty-fourth resistor R34; the 7 th pin of the second control chip U2 is grounded to provide a current loop for an internal current signal; the 8 th pin of the second control chip U2 is a primary side current detection input end, and is connected with a thirty-fifth resistor R35, a thirty-sixth resistor R36, a thirty-seventh resistor R37, a thirty-eighth resistor R38, a thirty-ninth resistor R39 and a thirteenth capacitor C13, the thirty-fifth resistor R35, the thirty-sixth resistor R36, the thirty-seventh resistor R37 and the thirty-eighth resistor R38 are connected in parallel and then connected in series with the thirty-ninth resistor R39, one end of the thirteenth capacitor C13 is connected to the 8 th pin of the second control chip U2, the other end of the thirteenth capacitor C13 is grounded, and a primary side current flows through a thirty-fifth resistor R35, a thirty-sixth resistor R36, a thirty-seventh resistor R37 and a thirty-eighth resistor 38 to generate a voltage signal, and the voltage signal is compared with the internal reference signal of the second control chip U2 through a thirty-ninth resistor R39, a thirteenth capacitor C13 to the 8 th pin to calibrate an output current and provide an overcurrent protection function; the negative electrode of the second zener diode ZD2 is connected to the cathode of the reference voltage source S1, the eighth capacitor C8 provides a starting current for the second control chip U2 through the second zener diode ZD2 and the thirty-second resistor R32, a proper resistance value of the thirty-second resistor R32 is selected to ensure that the second control chip U2 starts to operate after the voltage on the fourteenth capacitor C14 of the bus is stabilized, and when the reference voltage source S1 is turned on, the voltage of the power pin, i.e., the 6 th pin, of the second control chip U2 is pulled down to stop the operation of the second control chip U2, so that the over-temperature protection of the switching power supply is realized, and the safety of the switching power supply is further improved.

The utility model also provides a switching power supply excess temperature protection circuit, because the above has carried out detailed description to this switching power supply excess temperature protection circuit, no longer give unnecessary details here.

In summary, the utility model provides a switching power supply over-temperature protection circuit and switching power supply, switching power supply over-temperature protection circuit includes rectifier module, temperature detection module, voltage division module, filtering module and protection module; the rectifying module is used for rectifying alternating-current voltage and outputting direct-current voltage to the voltage dividing module through the temperature detection module, and the voltage dividing module is used for dividing and sampling the direct-current voltage and outputting sampling voltage to the filtering module; the filtering module is used for filtering the sampling voltage and outputting the filtered sampling voltage to the protection module; the temperature detection module is used for detecting the current working temperature of the control module, enabling the sampling voltage to be larger than the threshold voltage of the protection module when the current working temperature is larger than a preset temperature, and enabling the sampling voltage to be smaller than the threshold voltage when the current working temperature is smaller than the preset temperature; the protection module is used for conducting when the sampling voltage is larger than the threshold voltage, so that the control module is closed; the protection module is also used for closing when the sampling voltage is smaller than the threshold voltage, so that the control module is restarted, thereby realizing the over-temperature protection of the switching power supply, improving the safety of the switching power supply, and automatically starting the switching power supply after the temperature is recovered to be normal.

It should be understood that equivalent alterations and modifications can be made by those skilled in the art according to the technical solution of the present invention and the inventive concept thereof, and all such alterations and modifications should fall within the scope of the appended claims.

Claims

1. The over-temperature protection circuit of the switching power supply is connected with a control module of the switching power supply and is characterized by comprising a rectification module, a temperature detection module, a voltage division module, a filtering module and a protection module; the rectifying module is used for rectifying alternating-current voltage and outputting direct-current voltage to the voltage dividing module through the temperature detection module, and the voltage dividing module is used for dividing and sampling the direct-current voltage and outputting sampling voltage to the filtering module; the filtering module is used for filtering the sampling voltage and outputting the filtered sampling voltage to the protection module; the temperature detection module is used for detecting the current working temperature of the control module, controlling the sampling voltage to be larger than the threshold voltage of the protection module when the current working temperature is larger than a preset temperature, and controlling the sampling voltage to be smaller than the threshold voltage when the current working temperature is smaller than the preset temperature; the protection module is used for conducting when the sampling voltage is larger than the threshold voltage and controlling the control module to be closed; the protection module is further used for closing when the sampling voltage is smaller than the threshold voltage, and controlling the control module to restart.

2. The switching power supply over-temperature protection circuit according to claim 1, wherein the protection module comprises a reference voltage source, a cathode of the reference voltage source is connected to the control module, an anode of the reference voltage source is grounded, and a reference end of the reference voltage source is connected to the filtering module and the voltage dividing module.

3. The switching power supply over-temperature protection circuit according to claim 1, wherein the rectifying module comprises a first diode, an anode of the first diode is connected to the alternating voltage input terminal, and a cathode of the first diode is connected to the temperature detection module.

4. The switching power supply over-temperature protection circuit according to claim 3, wherein the temperature detection module comprises a thermistor, one end of the thermistor is connected to the negative electrode of the first diode, and the other end of the thermistor is connected to the voltage division module.

5. The switching power supply over-temperature protection circuit according to claim 4, wherein the voltage dividing module comprises a first resistor, a second resistor, a third resistor and a fourth resistor; one end of the first resistor is connected with the other end of the thermistor, the other end of the first resistor is connected with one end of the third resistor, one end of the fourth resistor and the filtering module through the second resistor, and the other end of the third resistor and the other end of the fourth resistor are both grounded.

6. The switching power supply over-temperature protection circuit according to claim 5, wherein the filter module comprises a first capacitor, one end of the first capacitor is connected to one end of the third resistor, one end of the fourth resistor and the protection module, and the other end of the first capacitor is grounded.

7. A switching power supply is characterized by comprising the switching power supply over-temperature protection circuit as claimed in any one of claims 1 to 6, and further comprising a rectifier bridge, a control module, a PFC voltage output module and an LL C resonance module, wherein the control module comprises a PFC control unit and a LL C control unit, the switching power supply over-temperature protection circuit is used for controlling the control module to be turned off to carry out over-temperature protection according to the change of the current working temperature of the control module, the rectifier bridge is used for rectifying an alternating current voltage and then outputting the direct current voltage to the PFC control unit and the LL C control unit, the PFC control unit is used for controlling the PFC voltage output module to output a PFC voltage to the LL C resonance module, and the LL C control unit is used for controlling the LL C resonance module to convert the PFC voltage into a preset output voltage and output the preset output voltage to a load.

8. The switching power supply according to claim 7, wherein the PFC control unit comprises a first control chip, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, a twelfth resistor, a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, a sixteenth resistor, a seventeenth resistor, an eighteenth resistor, a nineteenth resistor, a twentieth resistor, a twenty-first resistor, a twenty-second resistor, a twenty-third resistor, a third diode, a second capacitor, a third capacitor, a fourth capacitor and a seventh capacitor; one end of the twenty-first resistor is connected with the rectifier bridge, the other end of the twenty-first resistor is connected with one end of the twentieth resistor through the twenty-second resistor and the nineteenth resistor, the other end of the twentieth resistor is connected with one end of the twenty-third resistor, one end of the seventh capacitor and the 3 rd pin of the first control chip, and the other ends of the twenty-third resistor and the seventh capacitor are grounded; one end of the second capacitor and one end of the sixth resistor are connected with a pin 4 of the first control chip, the other end of the sixth resistor and one end of the fifth resistor are connected with the PFC voltage output module, and the other end of the fifth resistor and the other end of the second capacitor are both grounded; one end of the sixteenth resistor is connected with the PFC voltage output module, the other end of the sixteenth resistor is connected with one end of the twelfth resistor through the fifteenth resistor, the fourteenth resistor and the thirteenth resistor, the other end of the twelfth resistor is connected with one end of the third capacitor, one end of the fourth capacitor, the 1 st pin of the first control chip, one end of the seventeenth resistor and one end of the eighteenth resistor, the other end of the third capacitor is connected with the 2 nd pin of the first control chip through the seventh resistor, the other end of the fourth capacitor is connected with the 2 nd pin of the first control chip, and the other ends of the seventeenth resistor and the eighteenth resistor are grounded; the negative electrode of the third diode and one end of the ninth resistor are both connected with the pin 7 of the first control chip, and the positive electrode of the third diode and the other end of the ninth resistor are connected with the PFC voltage output module through the eighth resistor; and the 5 th pin of the first control chip is connected with the PFC voltage output module through the tenth resistor.

9. The switching power supply according to claim 8, wherein the PFC voltage output module comprises a first transformer, a MOS transistor, a fifth diode and a fourteenth capacitor; a 4 th pin of the first transformer is connected with the rectifier bridge, a 1 st pin of the first transformer is grounded, a 3 rd pin of the first transformer is connected with the anode of the fifth diode and the drain of the MOS tube, and a 2 nd pin of the first transformer is connected with the PFC control unit; the grid electrode of the MOS tube is connected with the PFC control unit, and the source electrode of the MOS tube is connected with the PFC control unit; and the cathode of the fifth diode is connected with one end of the fourteenth capacitor, and the other end of the fourteenth capacitor is grounded.

10. The switching power supply according to claim 9, wherein the LL C resonant module comprises a second transformer, a first inductor and a sixth capacitor, one end of the first inductor is connected to the PFC voltage output module, the other end of the first inductor is connected to pin 1 of the second transformer, one end of the sixth capacitor is connected to the LL C control unit, and the other end of the sixth capacitor is connected to pin 2 of the second transformer.