CN109818328B - A switching power supply overvoltage protection circuit - Google Patents

Abstract

The invention discloses an overvoltage protection circuit of a switching power supply, which mainly includes a power supply circuit, a voltage acquisition module and a voltage processing module. The collection end of the voltage collection module is connected to the input end of the inductor in the power supply circuit, and is used to collect the front-end voltage of the inductor. The normal operation and abnormal short circuit of the power supply circuit can be displayed in the voltage waveform of the front-end of the inductor. Therefore, by collecting the voltage value at the front end of the inductor, the overvoltage and short circuit conditions in the power supply circuit can be accurately detected; at the same time, the feedback point of increasing the voltage at the front end of the inductor can eliminate the delay caused by the voltage caused by the inductor and the capacitor because the current does not pass through the inductor and capacitor. , to improve the response speed of overvoltage protection, the voltage processing module and the voltage acquisition module cooperate to detect abnormal voltage waveforms, and adjust the control signal of the controller according to the detection results, which can achieve accurate and rapid detection of power circuit overvoltage, thereby reducing Power circuit overvoltage losses.

Description

A switching power supply overvoltage protection circuit

technical field

The invention relates to the technical field of server motherboards, in particular to an overvoltage protection circuit of a switching power supply.

Background technique

Server motherboards have high requirements for stability, and the stability of the power supply is the basis for the stability of the motherboard. Figure 1 shows a circuit diagram of a power supply circuit. The switching power supply realizes switching control by driving two switching tubes (such as MosFETs) to turn on alternately. In fact, due to the structure of MosFETs, the possibility of short circuit is very high. In actual production It also happens from time to time.

At present, the switching power supply of the server motherboard usually has a large voltage difference between the input voltage and the output voltage. For example, when 12V is used as the input, the output is about 1.05V, 1V, 0.95V, etc., where the MosFET is short-circuited and powered on, which is devastating to the power module. If 12V is directly connected to the load, it is also devastating to the chip. For example, for a chip rated at 1V, 12V has far exceeded its withstand voltage value, which greatly increases the possibility of short-circuit and burnout; and the server motherboard switching power supply usually requires Supply power to low-voltage chips such as CPU, PCH, and HD expansion chips. These load chips are expensive, and easy damage will greatly increase the cost.

At present, the stability of the switching power supply can be improved by increasing the voltage protection circuit. The protection circuit with increased voltage can not only protect the power module itself, but also protect the next-level load chip, which is a more commonly used switching power supply protection method at present.

The traditional voltage protection circuit is to control the switching power supply to turn off to achieve protection when the fault of the switching power supply is detected, which causes the output voltage to rise abnormally, which is higher than the preset upper limit value. This method can realize overvoltage protection, but since the voltage detection point is at the output end, the response speed is slow, and this time delay will still cause great damage to the circuit itself.

Therefore, how to improve the response speed of the overvoltage protection is a technical problem to be solved by those skilled in the art.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a switching power supply overvoltage protection circuit, which can realize the accurate and rapid detection of the overvoltage of the power supply circuit and reduce the overvoltage loss of the power supply circuit.

In order to solve the above technical problems, the present invention provides a switching power supply overvoltage protection circuit, including: a power supply circuit, a voltage acquisition module and a voltage processing module;

The collection end of the voltage collection module is connected to the input end of the inductor in the power supply circuit, and is used to collect the front-end voltage of the inductor. When the front-end voltage is a normal square wave, a first signal is output; when the front-end voltage is a normal square wave, a first signal is output; When the voltage is an abnormal short-circuit high-level waveform, the second signal is output;

The output end of the voltage acquisition module is connected to the input end of the voltage processing module, and the voltage processing module is used to perform signal identification processing on the received signal, and when the received signal is the first signal, output normal operation control signal; when the received signal is the second signal, output a short circuit cut signal;

The output end of the voltage processing module is connected to the control end of the controller, and the controller is configured to control the working state of the switch tube in the power supply circuit according to the signal output by the voltage processing module.

Optionally, the voltage acquisition module includes: a first resistor and a second resistor;

The first end of the second resistor is connected to the input end of the inductor in the power supply circuit, and the second end of the second resistor and the first end of the first resistor are connected to the voltage processing module. a first end, the second end of the first resistor is grounded;

Correspondingly, the first signal is a square wave signal with a normal duty cycle, and the second signal is an abnormally high level signal.

Optionally, the voltage processing module is specifically: an analog-to-digital converter and an abnormal signal judger;

The input end of the analog-to-digital converter is connected to the second end of the second resistor, and the output end is connected to the input end of the abnormal signal judger, for converting the received digital signal into an analog signal and outputting;

The output end of the abnormal signal judgment device is connected to the control end of the controller, and is used for abnormal judgment of the received signal.

Optionally, the abnormal signal determiner is specifically a signal determiner constituting the controller.

Optionally, the voltage acquisition module further includes: a third resistor, a diode and a capacitor;

The first end of the third resistor is connected to the first end of the second resistor, the second end of the third resistor is connected to the first end of the diode, and the second end of the diode is connected to the first end of the diode. The first end of the capacitor is connected to the first end of the voltage processing module, and the second end of the capacitor is connected to the second end of the first resistor;

Correspondingly, the first signal is a periodic charging and discharging waveform, the second signal is a charging waveform whose voltage value is positively correlated with the charging time, and the voltage processing module is used to perform the received voltage with a preset reference voltage. By comparison, when the received voltage is not higher than the preset reference voltage, a normal operation control signal is output; when the received voltage is higher than the preset reference voltage, a short circuit cut signal is output.

Optionally, the voltage processing module is specifically: a voltage comparator.

Optionally, the diode is a bond diode.

Optionally, the capacitor is a mica capacitor.

Optionally, the input terminal of the voltage processing module is further connected to the voltage output terminal of the power supply circuit.

Optionally, the second end of the first resistor is connected to the source-level ground end of the lower MOS transistor in the power supply circuit.

The switching power supply overvoltage protection circuit provided by the present invention mainly includes a power supply circuit, a voltage acquisition module and a voltage processing module. Among them, the acquisition terminal of the voltage acquisition module is connected to the input terminal of the inductor in the power supply circuit, and is used to collect the front-end voltage of the inductor. The normal operation of the power supply circuit and abnormal short circuit can be displayed in the voltage waveform of the front-end of the inductor. When the power supply circuit When normal, the front-end voltage is a normal square wave, and when the power circuit is abnormally short-circuited, the front-end voltage is an abnormally short-circuit high-level waveform. Therefore, by collecting the voltage value of the front-end of the inductor, the overvoltage and short-circuit conditions in the power circuit can be accurately detected; Since the current does not pass through the inductor and capacitor, the voltage feedback point can eliminate the voltage delay caused by the inductor and capacitor, and improve the response speed of the overvoltage protection. The voltage processing module cooperates with the voltage acquisition module to detect abnormal voltage waveforms. As a result, by adjusting the control signal of the controller, accurate and rapid detection of the overvoltage of the power supply circuit can be realized, thereby reducing the overvoltage loss of the power supply circuit.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only It is an embodiment of the present invention. For those of ordinary skill in the art, other drawings can also be obtained according to the provided drawings without creative work.

Fig. 1 is a circuit diagram of a power supply circuit;

Figure 2 is a schematic diagram of a commonly used traditional overvoltage protection circuit;

3 is a circuit diagram of a switching power supply overvoltage protection circuit provided by an embodiment of the present invention;

4 is a circuit diagram of another overvoltage protection switching power supply circuit provided by an embodiment of the present invention;

FIG. 5 is a circuit diagram of another overvoltage protection switching power supply circuit according to an embodiment of the present invention.

Detailed ways

The core of the present invention is to provide a switching power supply overvoltage protection circuit, which can realize accurate and rapid detection of the overvoltage of the power supply circuit and reduce the overvoltage loss of the power supply circuit.

In order to make the purposes, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments These are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Figure 1 shows a circuit diagram of a commonly used power supply circuit. The main functional components in the power supply circuit include a controller, a switch tube, an inductor and a capacitor. It should be noted that the power supply circuit may further include other auxiliary functional devices. 1 is only one of the circuit forms. Of course, the switching power supply circuit with the same switching principle as the circuit diagram shown in FIG. 1 (that is, it is controlled by a switch tube and contains inductance and/or capacitance) is also applicable to the overvoltage protection provided by the present invention. Switching power supply circuit, in the present invention only

The power supply circuit form shown in FIG. 1 is introduced as an example, and other power supply circuit forms can be referred to the introduction of the present invention, which will not be repeated here.

At present, the switching power supply usually needs to have an over-voltage protection function for the output. The over-voltage protection function refers to the abnormal increase of the output voltage caused by the detection of the fault of the switching power supply, which is higher than the upper limit set in advance, and the switching power supply is controlled to turn off to achieve Protect.

Figure 2 shows a schematic diagram of a commonly used traditional over-voltage protection circuit. The over-voltage protection circuit detects the terminal voltage of the output capacitor of the power supply, and is connected to the comparator integrated inside the switching power supply chip through the voltage feedback line. voltage for comparison. The output of the comparator is connected to the enable terminal of the main control of the switching power supply chip. When the feedback voltage is higher than the reference voltage, the output of the comparator is reversed, from output high to output low, so that the controller is turned off to achieve protection.

This method can realize overvoltage protection, but since the point of voltage detection is at the output end of the power supply, if the upper switch tube (such as the upper mosfet) is short-circuited, considering the path of energy transfer (input-inductor-output capacitor), at the output The voltage feedback on the capacitor is basically at the end of the entire energy transfer, and the response of the inductor, capacitor, and controller has a delay, resulting in a slow response speed, and it cannot immediately respond to the short circuit of the upper mosfet.

The invention provides an overvoltage protection circuit of a switching power supply. The circuit adds a voltage feedback point at the input end of the inductor, so that the delay caused by the voltage caused by the inductor and the capacitor can be eliminated, and the response delay of the controller can be avoided at the same time. Response speed of overvoltage protection.

Example 1:

FIG. 3 shows a circuit diagram of an overvoltage protection circuit of a switching power supply provided by an embodiment of the present application. The circuit mainly includes: a power supply circuit, a voltage acquisition module and a voltage processing module.

The power supply circuit in the switching power supply overvoltage protection circuit takes the circuit structure shown in Figure 1 as an example. The collecting terminal of the voltage acquisition module is connected to the input terminal of the inductor in the power supply circuit. The voltage waveform is a square wave with a certain duty cycle (the duty cycle is determined by the ratio of the output voltage to the input voltage, usually less than 50%), the high level is the input voltage, and the low level is 0V.

The voltage acquisition module is used to collect the front-end voltage of the inductor. When the front-end voltage is a normal square wave, it outputs the first signal; when the front-end voltage is an abnormal short-circuit high-level waveform, it outputs the second signal. The first signal and the second signal respectively refer to the normal inductor front-end voltage waveform and the abnormal inductor front-end voltage waveform (in this embodiment, the abnormality refers to the short circuit of the switch tube), which may be the original front-end voltage waveform signal directly collected, or may be a pair of The waveform signal processed by the original voltage is not limited here. When the switch tube in the power supply circuit is short-circuited, the waveform of the front end of the inductor will change. After the voltage acquisition module is used for voltage acquisition, the abnormality in the circuit will be reflected in the voltage waveform output by the voltage acquisition module, resulting in abnormal voltage waveform output by the voltage acquisition module. , the subsequent power supply circuit abnormality judgment can be performed based on the waveform.

In this embodiment, the voltage acquisition module is arranged at the front end of the inductor, and a voltage feedback point is added at the input end of the inductor to collect the voltage at the front end of the inductor and the capacitor, so that the delay caused by the voltage caused by the inductor and the capacitor can be eliminated, especially when the upper switch tube is In the case of short circuit, the response speed of the overvoltage protection can be accelerated.

The specific circuit form of the voltage acquisition module is not limited here, and the voltage acquisition at the front end of the inductance can be realized. For example, it can be directly connected to the front end of the inductance to connect wires and set a protection resistor, or set up devices such as capacitors for voltage acquisition, etc.

The output end of the voltage acquisition module is connected to the input end of the voltage processing module. The voltage processing module is used for signal identification processing on the received signal, when the received signal is the first signal, it outputs a normal operation control signal; when the received signal is the second signal, it outputs a short circuit cut signal.

The output terminal of the voltage processing module is connected to the control terminal of the controller. At present, the controller in the power supply circuit needs to receive analog signals to perform normal processing. Therefore, the voltage processing module needs to perform abnormal judgment on the collected voltage to determine whether the power circuit has a short circuit, etc. abnormal conditions, and finally generate an analog signal input to the control terminal of the controller. Specifically, the voltage processing module may be an AD converter, a voltage judgment circuit, or a circuit form such as a voltage comparator, which can implement the above functions.

The controller in the power supply circuit is used to control the working state of the switch tube in the power supply circuit according to the signal output by the voltage processing module. For the specific control process of the switch tube by the controller, reference may be made to the related introduction of the existing switch tube circuit, which will not be repeated here.

Based on the above technical solutions, the switching power supply overvoltage protection circuit provided by the embodiment of the present invention mainly includes a power supply circuit, a voltage acquisition module, and a voltage processing module. Among them, the acquisition terminal of the voltage acquisition module is connected to the input terminal of the inductor in the power supply circuit, and is used to collect the front-end voltage of the inductor. The normal operation of the power supply circuit and abnormal short circuit can be displayed in the voltage waveform of the front-end of the inductor. When the power supply circuit When normal, the front-end voltage is a normal square wave, and when the power circuit is abnormally short-circuited, the front-end voltage is an abnormally short-circuit high-level waveform. Therefore, by collecting the voltage value of the front-end of the inductor, the overvoltage and short-circuit conditions in the power circuit can be accurately detected; Since the current does not pass through the inductor and capacitor, the voltage feedback point can eliminate the voltage delay caused by the inductor and capacitor, and improve the response speed of the overvoltage protection. The voltage processing module cooperates with the voltage acquisition module to detect abnormal voltage waveforms. As a result, by adjusting the control signal of the controller, accurate and rapid detection of the overvoltage of the power supply circuit can be realized, thereby reducing the overvoltage loss of the power supply circuit.

Embodiment 2:

The specific circuit form of the voltage acquisition module is not limited in the above embodiment. In this embodiment, the voltage acquisition module includes: a first resistor and a second resistor as an example for description.

The first end of the second resistor is connected to the input end of the inductor in the power supply circuit, the second end of the second resistor and the first end of the first resistor are connected to the first end of the voltage processing module, and the second end of the first resistor is grounded .

The first resistor and the second resistor mainly play the role of current divider, and the voltage at the front end of the inductor is lowered for detection, so as to avoid its overvoltage influence on the subsequent voltage processing module.

When the voltage acquisition module is the first resistor and the second resistor, since the normal voltage signal at the front end of the inductor is a square wave signal with a normal duty cycle, the corresponding first signal is also a square wave signal with a normal duty cycle; when When the power supply circuit is short-circuited, the front end of the inductor is a continuous high-level signal, and accordingly, the second signal is an abnormally high-level signal.

The voltage processing module cooperates with the voltage acquisition module. When the voltage acquisition module is the first resistor and the second resistor, the voltage processing module is used to distinguish the square wave signal with normal duty cycle and the abnormal high level signal, generate the identification result and It is converted into an analog input to the controller. Specifically, the voltage processing module can use an analog-to-digital converter and an abnormal signal judger, or can also use a voltage comparator to perform analog-to-digital conversion and then use the controller to judge the abnormal type, which is not limited here.

It should be noted that, in this embodiment, the resistance values of the first resistor and the second resistor need to be determined according to the parameters of other components in the circuit, and the specific calculation method can refer to the related art, which will not be repeated here.

Since the use of the analog-to-digital converter and the abnormal signal judger as the voltage processing module can quickly screen and judge without changing the original power circuit, the analog-to-digital converter and the abnormal signal judger are used as examples to introduce. Specifically, the input end of the analog-to-digital converter is connected to the second end of the second resistor, and the output end is connected to the input end of the abnormal signal judger, for converting the received digital signal into an analog signal and outputting; the abnormal signal judgment The output end of the controller is connected to the control end of the controller, and is used to judge the abnormality of the received signal.

Among them, in order to reduce the components in the circuit and reduce the cost, preferably, the controller in the original power supply circuit can be used as the signal judge. Specifically, a code input for judging the corresponding signal type can be performed on the controller, so that the controller has a corresponding signal processing function (for this part, reference may be made to the implementation method of the related art).

Embodiment three:

The voltage acquisition module in the second embodiment realizes the direct acquisition of the front-end voltage of the inductor. In order to reduce the time delay caused by the analog or digital judgment of the subsequent signal and avoid the delay of the controller response, preferably, the voltage acquisition module in the may further include: a third resistor, a diode and a capacitor,

FIG. 4 shows a circuit diagram of an overvoltage protection switching power supply circuit provided in this embodiment, and the circuit structure of the voltage acquisition module is shown in the dotted box in FIG. 4 .

The voltage acquisition module in the circuit includes current limiting resistors R1, R2, R3 (R2>R1>>R3), a reverse cut-off diode D1 and a voltage detection capacitor C1, and the voltage processing module is a voltage comparator that inputs a preset reference voltage in the forward direction , the terminal voltage of C1 is connected to the negative input terminal of the comparator as a voltage feedback line.

The first end of the second resistor (R2) in the voltage acquisition module is connected to the input end of the inductor in the power supply circuit, and the second end of the second resistor and the first end of the first resistor (R1) are connected to the voltage processing module (comparator). ) of the positive input terminal, the second terminal of the first resistor is grounded.

The first end of the third resistor (R3) is connected to the first end of the second resistor (R2), the second end of the third resistor (R3) is connected to the first end of the diode (D1), and the second end of the diode is connected to The first end of the capacitor (C1) is connected to the first end of the voltage processing module, and the second end of the capacitor is connected to the second end of the first resistor.

When the power supply circuit is in a normal state, when point A is at a high level. The D1 path is reversely cut off, and the high level charges the C1 capacitor through the voltage divider of R1 and R2, and the C1 capacitor voltage rises (normally the comparator will not be triggered); when point A is at a low level, since R2 and R1 are much larger than R3 , and D1 is forward biased, so C1 discharges through D1 and R3 to start the next cycle. Correspondingly, the first signal is a periodic charge and discharge waveform. The above circuit ensures that the charge and discharge of the C1 capacitor reaches a balance within one cycle.

The voltage processing module compares the received voltage with a preset reference voltage, and outputs a normal operation control signal (eg, output 1) when the received voltage is not higher than the preset reference voltage.

The switching power supply works in an abnormal normal state (such as the short circuit of the upper mosfet), which causes the voltage at point A to remain at a high level (approximately equal to the input voltage), and continues to charge C1. Correspondingly, the second signal is a positive voltage value and charging time. For the relevant charging waveform, the voltage processing module compares the received voltage with the preset reference voltage. With the extension of the charging time, the voltage of C1 will exceed the reference voltage of the comparator, and the comparator outputs a short-circuit cut signal (for example, output 0) , compared with the protection on the output capacitor, the above circuit form has a higher protection point and a faster response. Among them, the response time is determined by the time constant of R3 and C1.

In the overvoltage protection switching power supply circuit provided by this embodiment, the power supply circuit works in an abnormal normal state (the upper mosfet is short-circuited), so that the voltage at point A is maintained at a high level (equal to the input voltage), and C1 is continuously charged. Correspondingly, the first The second signal is a charging waveform with a positive correlation between the voltage value and the charging time. Eventually, the voltage of C1 will exceed the reference voltage of the comparator to initiate protection. The response time is determined by the time constant of R3 and C1. Compared with the protection on the output capacitor, this kind of protection has a more advanced protection point and a faster response, and only needs to add some lines to the current switching power supply circuit to achieve fast OVP protection, and the device is simple to implement. low cost.

C₁电容充电电压，V_in：电源输入电压，f_sw：电源开关频率，

二极管D₁压降，V_out：电源输出电压，各阻容值需满足以下条件：It should be noted that the size of the resistance-capacitance value in this embodiment needs to ensure the normal operation of each component in the circuit. Specifically, V _ref : reference voltage,

C ₁ capacitor charging voltage, V _in : power supply input voltage, f _sw : power switching frequency,

Diode D ₁ voltage drop, V _out : the output voltage of the power supply, each resistance and capacitance value must meet the following conditions:

其中，

in,

其中，

in,

Wherein, since the voltage comparator can realize the voltage analog-to-digital conversion and also can realize the comparison between the test voltage value and the preset standard voltage value, preferably, the voltage processing module can specifically select the voltage comparator.

In order to improve the response speed, the diode can be a key diode, and the capacitor can be a mica capacitor.

In addition, in this embodiment, the second end of the first resistor needs to be grounded. In order to reduce the setting of the ground terminal, preferably, the second end of the first resistor can be connected to the source-level ground terminal of the lower MOS transistor in the power supply circuit.

Embodiment 4:

In order to realize the double monitoring of the power supply circuit, improve the detection efficiency, and avoid the influence of the accidental failure of the single inspection method on the abnormal judgment, preferably, on the basis of the third embodiment, the input end of the voltage processing module can be further connected to the power supply circuit. Figure 5 shows the circuit diagram of an overvoltage protection switching power supply circuit provided in this embodiment. On the basis of Figure 4, only one wire is added. If a device in the front-end voltage acquisition module fails, The collection of the output voltage and the comparison with the preset reference voltage value can also realize the abnormal monitoring of the power supply circuit, complete the double protection of the power supply circuit, the implementation method is simple, and the detection is improved without adding additional device costs. Effect.

Of course, the wire arrangement in this embodiment may not be performed, which is not limited here.

The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the various embodiments can be referred to each other. It should also be noted that, in this specification, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply these entities or operations. There is no such actual relationship or sequence between operations. Moreover, the terms "comprising", "comprising" or any other variation thereof are intended to encompass a non-exclusive inclusion such that a process, method, article or device that includes a list of elements includes not only those elements, but also includes not explicitly listed or other elements inherent to such a process, method, article or apparatus. Without further limitation, an element qualified by the phrase "comprising a..." does not preclude the presence of additional identical elements in the process, method, article, or device that includes the element.

The above description of the disclosed embodiments enables any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (8)

1. an overvoltage protection switching power supply circuit, characterized in that, comprising: a power supply circuit, a voltage acquisition module and a voltage processing module; The collection end of the voltage collection module is connected to the input end of the inductor in the power supply circuit, and is used to collect the front-end voltage of the inductor. When the front-end voltage is a normal square wave, a first signal is output; when the front-end voltage is a normal square wave, a first signal is output; When the voltage is an abnormal short-circuit high-level waveform, the second signal is output; The output end of the voltage acquisition module is connected to the input end of the voltage processing module, and the voltage processing module is used to perform signal identification processing on the received signal, and when the received signal is the first signal, output normal operation control signal; when the received signal is the second signal, output a short circuit cut signal; The output end of the voltage processing module is connected to the control end of the controller, and the controller is used for controlling the working state of the switch tube in the power supply circuit according to the signal output by the voltage processing module; The voltage acquisition module includes: a first resistor, a second resistor, a third resistor, a diode and a capacitor; wherein, the first end of the second resistor is connected to the input end of the inductor in the power supply circuit, and the second resistor The second end of the resistor and the first end of the first resistor are connected to the first end of the voltage processing module, the second end of the first resistor is grounded; the first end of the third resistor is connected to the The first end of the second resistor and the second end of the third resistor are connected to the first end of the diode, and the second end of the diode and the first end of the capacitor are connected to the voltage processing module The first end of the capacitor is connected to the second end of the first resistor; correspondingly, the first signal is a periodic charge and discharge waveform, and the second signal is the voltage value and charging time A positively correlated charging waveform, the voltage processing module is used to compare the received voltage with a preset reference voltage, and output a normal operation control signal when the received voltage is not higher than the preset reference voltage; When the obtained voltage is higher than the preset reference voltage, a short circuit cut signal is output. 2. The overvoltage protection switching power supply circuit according to claim 1, wherein the voltage processing module is specifically: an analog-to-digital converter and an abnormal signal judger; The input end of the analog-to-digital converter is connected to the second end of the second resistor, and the output end is connected to the input end of the abnormal signal judger, for converting the received digital signal into an analog signal and outputting; The output end of the abnormal signal judgment device is connected to the control end of the controller, and is used for abnormal judgment of the received signal. 3 . The switching power supply circuit for overvoltage protection according to claim 2 , wherein the abnormal signal judging device is a signal judging device constituting the controller. 4 . 4. The overvoltage protection switching power supply circuit according to claim 1, wherein the voltage processing module is specifically a voltage comparator. 5 . The overvoltage protection switching power supply circuit of claim 1 , wherein the diode is a key diode. 6 . 6. The overvoltage protection switching power supply circuit of claim 1, wherein the capacitor is a mica capacitor. 7 . The overvoltage protection switching power supply circuit according to claim 1 , wherein the input terminal of the voltage processing module is further connected to the voltage output terminal of the power supply circuit. 8 . 8 . The switching power supply circuit for overvoltage protection according to claim 1 , wherein the second end of the first resistor is connected to the source-level grounding end of the lower MOS transistor in the power supply circuit. 9 .

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