Protection circuit of switching power supply and switching power supply

Abstract

The utility model discloses a switching power supply protection circuit and a switching power supply, through introducing a voltage detection circuit and a self-locking circuit, the voltage detection circuit can accurately monitor the output voltage of the switching power supply, and the self-locking circuit can output a driving signal when detecting that the voltage exceeds a set threshold value. And a preset voltage which is in a preset relationship with the voltage of the power supply end is superposed to the input end of the circuit, so that the voltage value for triggering the self-locking circuit to input a trigger signal is further increased, the self-locking circuit completes self-locking to continuously output a driving signal to the first switching circuit, and then the first switching circuit is controlled to output a non-enable signal, so that the self-locking of the circuit is realized. The switching power supply is deactivated. It can be seen that accurate detection of the switching power supply is completed through the voltage detection circuit, the preset voltage is fed back to the input end of the self-locking circuit through the self-locking circuit, so that the self-locking circuit continuously outputs the driving signal to enable the switching power supply to stop outputting, the output capacitor is automatically discharged to the preset restart value through the self-locking circuit, and then circuit reconduction is achieved.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of switching power supply, especially a protection circuit of switching power supply and switching power supply. BACKGROUND

[0002] The existing switching power supply chip is widely applied in industrial control and consumer field, but due to the imperfect internal protection mechanism, external circuit is often needed to assist to realize soft start, open loop and short circuit protection. In the process of realizing the present invention, the inventor found that at least the following problems exist in the prior art, the traditional technology realizes short circuit and switching protection by detecting the COMP pin voltage or using a series resistor of zener diode, but the actual output voltage in the circuit cannot be known and the circuit cannot be automatically turned on again by detecting the COMP pin voltage and using a series resistor of multiple zener diodes. SUMMARY

[0003] The utility model discloses a protection circuit of switching power supply and switching power supply, solve the problem that the actual output voltage in the circuit cannot be known and the circuit cannot be automatically turned on again when the traditional technology realizes short circuit and switching protection.

[0004] To solve the above technical problems, the utility model provides a protection circuit of switching power supply, including:

[0005] Voltage detection circuit, its input end is connected with the output capacitor of switching power supply, is used for detecting the output voltage of switching power supply;

[0006] Self locking circuit, its input end is connected with the output end of voltage detection circuit and the feedback end of itself respectively, its power supply end is connected with its power supply or the output capacitor of switching power supply, is used for output drive signal when the detection voltage of voltage detection circuit reaches voltage threshold value, adds the preset voltage to the input end of itself through the feedback end of itself, and the preset voltage and the voltage of power supply are in preset relationship;

[0007] First switching circuit, its input end is connected with the output end of self locking circuit, its output end is connected with the enable end of switching power supply, is used for moving when receiving drive signal, to output the unenabled signal to the enable end of switching power supply, makes switching power supply stop output;

[0008] Wherein, when switching power supply stops output, the output capacitor is discharged automatically through self locking circuit, and switching power supply is restarted when the output capacitor is discharged to the preset restart value.

[0009] Optionally, the self locking circuit includes:

[0010] First zener chip, second switching circuit;

[0011] The first end of the first voltage stabilizing chip is connected with the output end of the voltage detection circuit and the first end of the second switch circuit respectively, the second end of the first voltage stabilizing chip is connected with the control end of the second switch circuit, the third end of the first voltage stabilizing chip is grounded, the second end of the second switch circuit is connected with the power supply or the output capacitor, and the third end of the second switch circuit is connected with the input end of the first switch circuit.

[0012] The first voltage stabilizing chip is configured to turn on the second end and the third end of the first voltage stabilizing chip when the voltage at the first end of the first voltage stabilizing chip reaches the voltage threshold set internally.

[0013] The second switch circuit is configured to turn on the first path between the second end and the first end of the second switch circuit and the second path between the second end and the third end of the second switch circuit when the second end and the third end of the first voltage stabilizing chip are turned on.

[0014] Optionally, the second switch circuit comprises:

[0015] a first controllable switch and a first diode.

[0016] The control end of the first controllable switch is connected with the second end of the first voltage stabilizing chip, the first end of the first controllable switch is connected with the power supply or the output capacitor, the third end of the first controllable switch is connected with the input end of the first switch circuit and the anode of the first diode respectively, and the cathode of the first diode is connected with the first end of the first voltage stabilizing chip.

[0017] Optionally, the second switch circuit further comprises:

[0018] four resistors, the first end of a first resistor is connected with the control end of the first controllable switch, the first end of a second resistor is connected with the first end of the first controllable switch, the second end of the second resistor is connected with the second end of the first resistor and the second end of the first voltage stabilizing chip respectively, the first end of a third resistor is connected with the cathode of the first diode, the second end of the third resistor is connected with the first end of the first voltage stabilizing chip, the first end of a fourth resistor is connected with the second end of the first controllable resistor, and the second end of the fourth resistor is connected with the input end of the first switch circuit.

[0019] Optionally, the application further comprises:

[0020] a voltage dividing circuit, the first end of the voltage dividing circuit is connected with the first end of the first controllable switch, and the second end of the voltage dividing circuit is connected with the power supply or the output capacitor, so as to share voltage when the first controllable switch is turned on.

[0021] Optionally, the voltage dividing circuit comprises:

[0022] At least one zener diode, an anode of the zener diode is connected with the first end of the first controllable switch, and a cathode of the zener diode is connected with the power supply.

[0023] Optionally, the voltage detection circuit comprises:

[0024] A fifth resistor and a sixth resistor;

[0025] The first end of the fifth resistor is connected with the output end of the switching power supply, the second end of the fifth resistor is connected with the first end of the sixth resistor and serves as the output end of the voltage detection circuit, and the second end of the sixth resistor is grounded.

[0026] Optionally, the first switch circuit comprises:

[0027] An optocoupler and a seventh resistor;

[0028] The first end of the optocoupler is connected with the first end of the seventh resistor and the output end of the self-locking circuit respectively, the second end of the optocoupler and the second end of the seventh resistor are both grounded, the third end of the optocoupler is grounded, and the fourth end of the optocoupler, as the output end of the first switch circuit, is connected with the enable end of the switching power supply.

[0029] To solve the above technical problems, the utility model provides a kind of switching power supply, including the protection circuit of the switching power supply described above.

[0030] The utility model provides a kind of protection circuit of switching power supply and switching power supply, by introducing voltage detection circuit and self-locking circuit, voltage detection circuit can accurately monitor the output voltage of switching power supply, self-locking circuit can output drive signal when detecting that voltage exceeds set threshold value, and preset voltage with the voltage of power supply end into preset relationship is added to itself input end, to further increase the voltage value of trigger self-locking circuit input signal, so that self-locking circuit completes self-locking, to continuously output drive signal to first switch circuit, and then control first switch circuit output is not enabled signal, so that switching power supply is deactivated.Visibly, the application is accurately detected to switching power supply by voltage detection circuit, and preset voltage is fed back to itself input end by self-locking circuit, to make self-locking circuit continuously output drive signal to make switching power supply stop output, and output capacitor is automatically discharged to preset restart value by self-locking circuit, to further realize circuit re-conduction. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present application, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings described below are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained without creative labor on the basis of these drawings.

[0032] Figure 1 A schematic diagram of a protection circuit of a switching power supply provided by the present application;

[0033] Figure 2 A specific circuit schematic diagram of a protection circuit of a switching power supply provided by the present application;

[0034] Figure 3 A schematic diagram of a switching power supply and peripheral circuit provided by the present application;

[0035] Figure 4 A specific circuit schematic diagram of a protection circuit of a switching power supply provided by the present application, including a voltage stabilizing diode. DETAILED DESCRIPTION

[0036] The core of the present application is to provide a protection circuit of a switching power supply and a switching power supply. The precise detection of the switching power supply is completed through a voltage detection circuit. The preset voltage is fed back to the input end of the self-locking circuit, so that the self-locking circuit continuously outputs the driving signal to stop the output of the switching power supply. The output capacitor is automatically discharged to the preset restart value through the self-locking circuit, thereby realizing the re-conduction of the circuit.

[0037] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0038] To solve the above technical problems, as shown in Figure 1 The present application provides a protection circuit of a switching power supply, comprising:

[0039] A voltage detection circuit 11, the input end of which is connected with the output capacitor of the switching power supply, for detecting the output voltage of the switching power supply;

[0040] The self-locking circuit 12 has an input end connected with the output end of the voltage detection circuit 11 and a feedback end of itself respectively, and a power supply end connected with the output capacitor of the power supply or the switching power supply, for outputting a driving signal when the detection voltage of the voltage detection circuit 11 reaches a voltage threshold, and superimposing a preset voltage on the input end of itself through the feedback end, the preset voltage having a preset relationship with the voltage of the power supply;

[0041] The first switching circuit 13 has an input end connected with the output end of the self-locking circuit 12, and an output end connected with the enable end of the switching power supply, for acting when receiving the driving signal to output a disable signal to the enable end of the switching power supply, so as to stop the switching power supply from outputting;

[0042] When the switching power supply stops outputting, the output capacitor is automatically discharged through the self-locking circuit, and the switching power supply is restarted when the output capacitor is discharged to a preset restart value.

[0043] The protection circuit of the switching power supply significantly improves the monitoring accuracy and protection effect of the output voltage of the switching power supply by introducing the voltage detection circuit 11 and the self-locking circuit 12.

[0044] The main function of the voltage detection circuit 11 is to monitor the output voltage of the switching power supply in real time, to ensure that the voltage exceeding the preset threshold can be captured in time. When the output voltage is detected to reach or exceed this threshold, the self-locking circuit 12 will respond immediately to output a driving signal to activate the subsequent protection mechanism. The unique feature of the self-locking circuit 12 is that it can not only output a driving signal, but also feed back a preset voltage having a preset relationship with the voltage of the power supply to its input end. This feedback mechanism effectively enhances the triggering voltage of the self-locking circuit 12, ensuring that it can continuously output the driving signal when the voltage exceeds the set value. This self-locking function enables the self-locking circuit 12 to maintain its state independently, preventing false actions caused by transient fluctuations. After receiving the driving signal from the self-locking circuit 12, the first switching circuit 13 will output a disable signal, and then stop the switching power supply from working, thereby realizing effective protection of the switching power supply. Through this process, the protection circuit can accurately and reliably monitor and control the power supply state, greatly improving the accuracy and stability of the protection mechanism, and meeting the high standard requirements of industrial control and consumer fields for power supply chips.

[0045] It needs to be understood that the output voltage of the switching power supply is the voltage of the output capacitor, and during the discharging process of the output capacitor, the output voltage of the switching power supply gradually decreases, and when the sum of the output voltage and the preset voltage decreases to the voltage threshold value, the self-locking circuit 12 stops outputting the driving signal, and the first switching circuit 13 stops outputting the unenabled signal, so that the switching power supply restarts to work. The time interval between the time when the output voltage reaches the voltage threshold value and the time when the switching power supply stops working is called the hiccup time. According to the above principle, by adjusting the voltage of the power supply or the corresponding relationship between the power supply and the preset voltage, the hiccup time can be adjusted.

[0046] In a specific embodiment, as shown in Figure 2 and Figure 3 , the switching power supply is a power supply chip U3, at this time SS is the signal output by the protection circuit, at this time Q2 is turned on, and then the COMP pin of U3 is pulled low. U3 does not work.

[0047] This protection mechanism can effectively prevent faults caused by overvoltage through automatic detection and reaction, and improves the reliability and stability of the switching power supply. Through the voltage detection circuit, accurate detection of the switching power supply is completed, and the preset voltage is fed back to the input end of the self-locking circuit through the self-locking circuit, so that the self-locking circuit continuously outputs the driving signal to make the switching power supply stop outputting, and the output capacitor is automatically discharged to the preset restart value through the self-locking circuit, thereby realizing the re-conduction of the circuit.

[0048] As shown in Figure 2 , as a preferred embodiment, the self-locking circuit 12 comprises:

[0049] a first voltage stabilizing chip U1 and a second switching circuit;

[0050] The first end of the first voltage stabilizing chip U1 is connected with the output end of the voltage detection circuit 11 and the first end of the second switching circuit respectively, the second end of the first voltage stabilizing chip U1 is connected with the control end of the second switching circuit, the third end of the first voltage stabilizing chip U1 is grounded, the second end of the second switching circuit is connected with the power supply or the output capacitor, and the third end of the second switching circuit is connected with the input end of the first switching circuit 13;

[0051] The first voltage stabilizing chip U1 is used to turn on the second end and the third end of itself when the voltage at the first end of itself reaches the internal set voltage threshold value;

[0052] The second switching circuit is used to turn on the first path between the second end and the first end of itself and turn on the second path between the second end and the third end of itself when the second end and the third end of the first voltage stabilizing chip U1 are turned on.

[0053] In this preferred embodiment, the self-locking circuit 12 realizes effective protection of the switching power supply through the cooperation of the first voltage stabilizing chip U1 and the second switching circuit. First, the first voltage stabilizing chip U1 monitors the output voltage from the voltage detection circuit 11, and when the voltage reaches the set voltage threshold (the trigger voltage threshold of the first voltage stabilizing chip U1 itself), the first voltage stabilizing chip U1 is turned on. This on state forms a current path between the second end and the third end of the first voltage stabilizing chip U1, thereby activating the second switching circuit. The second switching circuit works based on the on state of the first voltage stabilizing chip U1. When the second end and the third end of the first voltage stabilizing chip U1 are turned on, the second switching circuit will simultaneously open two paths: the first path connects its second end and first end to turn on the first controllable switch control part. The other path connects its second end and third end, thereby outputting a driving signal to the first switching circuit 13 through the third end, and feeding back the voltage of the power supply (or a preset voltage in a preset relationship with the voltage of the power supply) to the first end of the first voltage stabilizing chip U1, forming a positive feedback, so that the second end and the third end of the first voltage stabilizing chip U1 can be continuously and reliably turned on.

[0054] Through the opening of the two paths, the second switching circuit can make the first switching circuit 13 continuously receive the driving signal, further ensuring that the output of the switching power supply is effectively cut off, and the safe operation of the circuit is protected. Overall, this mechanism realizes fast response and automatic locking to abnormal voltage state, thereby improving the reliability of the switching power supply system.

[0055] As a preferred embodiment, the second switching circuit comprises:

[0056] The first controllable switch Q1 and the first diode D1;

[0057] The control end of the first controllable switch Q1 is connected with the second end of the first voltage stabilizing chip U1, the first end of the first controllable switch Q1 is connected with the power supply or the output capacitor, the second end of the first controllable switch Q1 is connected with the input end of the first switching circuit 13 and the anode of the first diode D1 respectively, and the cathode of the first diode D1 is connected with the first end of the first voltage stabilizing chip U1.

[0058] In the preferred embodiment, the second switch circuit enhances the function of the self-locking circuit 12 through the combination of the first controllable switch Q1 and the first diode D1. First, the control end of the first controllable switch Q1 is connected to the second end of the first voltage stabilizing chip U1. When the first voltage stabilizing chip U1 is turned on, the control signal will activate the first controllable switch Q1, making it enter the conduction state. At this time, the first end of the first controllable switch Q1 is connected to the power supply, ensuring the provision of stable power supply voltage, while its second end is simultaneously connected to the input end of the first switch circuit 13 and the anode of the first diode D1. In this way, the first controllable switch Q1 can directly transmit the voltage of the power supply to the input end of the first switch circuit 13 (i.e. V1Q1R4U2), ensuring that the first switch circuit 13 can continuously receive the required driving signal to maintain the operation of the protection circuit. In addition, the anode of the first diode D1 is connected to the second end of the first controllable switch Q1, and its cathode is connected to the first end of the first voltage stabilizing chip U1, forming a positive feedback loop. When the output voltage of the switching power supply is abnormal, the first diode D1 ensures the stable direction of current flow while the first voltage stabilizing chip U1 is turned on, preventing the voltage detection circuit 11 from directly driving the first switch circuit before reaching the pre-value of the first voltage stabilizing chip U1, and positively feeding the voltage of the power supply to the first end of the first voltage stabilizing chip U1 to ensure the reliable conduction between the second end and the third end of the first voltage stabilizing chip U1.

[0059] In summary, the design of the second switch circuit not only improves the response speed and stability of the circuit, but also achieves effective protection of the output of the switching power supply through precise signal control.

[0060] As a preferred embodiment, the second switch circuit further comprises:

[0061] The first end of the first resistor R1 is connected with the control end of the first controllable switch Q1, the first end of the second resistor R2 is connected with the second end of the first controllable switch Q1, the second end of the second resistor R2 is connected with the second end of the first resistor R1 and the second end of the first voltage stabilizing chip U1 respectively, the first end of the third resistor R3 is connected with the cathode of the first diode D1, the second end of the third resistor R3 is connected with the first end of the first voltage stabilizing chip U1, the first end of the fourth resistor R4 is connected with the second end of the first controllable switch, and the second end of the fourth resistor R4 is connected with the input end of the first switch circuit 13. In this circuit design, the four resistors cooperate with each other to ensure the normal work of the first controllable switch Q1 and other components. First, the first resistor R1 is used to limit the current flowing through the control end to protect the first controllable switch Q1 and ensure its stable conduction. The second resistor R2 provides voltage feedback to the second end of the first voltage stabilizing chip U1 by transmitting the voltage of the power supply to the second end of the second resistor R2, which helps to determine the conduction state of the first voltage stabilizing chip U1. The third resistor R3 limits the current. The fourth resistor R4 transmits signals to the input end of the first switch circuit 13, and through its connection with the second end of the first controllable switch Q1, forms a signal feedback loop to ensure that the first switch circuit 13 can always obtain appropriate driving signals. This design not only enhances the reliability of the circuit, but also improves the response capability to abnormal voltage, and realizes effective power protection.

[0062] As a preferred embodiment, it further comprises a voltage dividing circuit, the first end of which is connected with the first end of the first controllable switch Q1, and the second end of which is connected with the power supply or the output capacitor, for sharing voltage when the first controllable switch Q1 is turned on.

[0063] Specifically, the introduction of the voltage dividing circuit is used to optimize the working performance of the self-locking circuit 12. For example, when the power supply multiplexing switch power supply output voltage and the output voltage of the switch power supply is large, the voltage dividing circuit effectively reduces the voltage fed back to the second end of the first voltage stabilizing chip U1 by sharing part of the voltage. Specifically, the first end of the voltage dividing circuit is connected with the power supply, and the second end is connected with the first controllable switch Q1, forming a voltage dividing network. When the first controllable switch Q1 is off, the second end and the third end of the first voltage stabilizing chip U1 are also in the off mode, and the first voltage stabilizing chip U1 is generally TL431, and its withstand voltage is generally 36V. When the normal output voltage of the switch power supply is greater than 36V, the second end and the third end of the first voltage stabilizing chip U1 do not conduct and bear all the output voltage, which has the risk of breakdown. By connecting the voltage stabilizing tube in series, the power supply voltage adaptability of the circuit can be improved. The voltage dividing circuit can prevent the first voltage stabilizing chip U1 from being broken down due to excessive voltage, thereby ensuring stable operation of the system under high voltage output. This design further improves the protection effect of the switch power supply, ensuring that the system can work stably when the output voltage of the power supply is high.

[0064] As shown in Figure 4 a preferred embodiment, the voltage dividing circuit comprises at least one zener diode D2, the anode of which is connected to the first terminal of the first controllable switch Q1, and the cathode of which is connected to the power supply.

[0065] Specifically, the voltage dividing circuit uses at least one zener diode D2 to achieve the function of voltage sharing. When the output voltage of the switching power supply is high, the zener diode D2 and the first voltage stabilizing chip U1 are connected in series to adapt to the demand for higher output voltage. Specifically, the voltage adaptability of the self-locking circuit is improved to the sum of the breakdown voltage of the zener diode D2 and the breakdown voltage of the second and third terminals of the first voltage stabilizing chip U1. The zener diode protects the first voltage stabilizing chip U1 from being broken down by the output voltage of the power supply exceeding 36V in the off state.

[0066] It should be understood that if there is no second zener diode, the voltage fed back to the first terminal of the first voltage stabilizing chip U1 is the voltage of the power supply (i.e. the output voltage of the switching power supply), and after the second zener diode is set, the circuit will fail only when the output voltage reaches the sum of the breakdown voltages of the second zener diode and the first voltage stabilizing chip U1.

[0067] As a preferred embodiment, the voltage detection circuit 11 comprises:

[0068] a fifth resistor R5 and a sixth resistor R6;

[0069] The first terminal of the fifth resistor R5 is connected to the output terminal of the switching power supply, the second terminal of the fifth resistor R5 is connected to the first terminal of the sixth resistor R6 and serves as the output terminal of the voltage detection circuit 11, and the second terminal of the sixth resistor R6 is grounded.

[0070] Specifically, the voltage detection circuit 11 is composed of the fifth resistor R5 and the sixth resistor R6, and is designed to effectively monitor the output voltage of the switching power supply. The function of the fifth resistor R5 is to obtain a proportional value of the output voltage through the principle of voltage division. When the switching power supply is working, the output voltage will produce a voltage drop on the fifth resistor R5, and then form a voltage dividing network by connecting with the sixth resistor R6. The sixth resistor R6 further reduces the detected voltage and guides it to the output terminal of the voltage detection circuit 11, while the second terminal of the sixth resistor R6 is grounded to ensure that the voltage detection circuit 11 can obtain a stable reference voltage.

[0071] Through such a voltage dividing structure, the voltage detection circuit 11 can convert the relatively high output voltage of the switching power supply into a relatively low and controllable voltage value, so that the subsequent circuit can analyze and process the voltage.

[0072] It needs to be understood that by precisely setting the resistance values of the fifth resistor R5 and the sixth resistor R6, the detection accuracy of the voltage detection circuit 11 can be improved, the stable trigger self-locking circuit 12 can be ensured, and the reliable control of the enable end of the switching power supply can be realized.

[0073] As a preferred embodiment, the first switching circuit 13 comprises:

[0074] the optical coupler U2 and the seventh resistor R7;

[0075] The first end of the optical coupler U2 is connected with the first end of the seventh resistor R7 and the output end of the self-locking circuit 12 respectively, the second end of the optical coupler U2 and the second end of the seventh resistor R7 are both grounded, the third end of the optical coupler U2 is grounded, and the fourth end of the optical coupler U2 is connected with the enable end of the switching power supply as the output end of the first switching circuit 13.

[0076] Specifically, the first switching circuit 13 mainly consists of the optical coupler U2 and the seventh resistor R7, and the purpose is to realize signal isolation and control in the protection mechanism of the switching power supply. When the self-locking circuit 12 outputs a driving signal, the optical coupler U2 can receive the signal and convert it into an optical signal. The working principle of the optical coupler U2 is to use the characteristics of photoelectric isolation to keep the high-voltage and low-voltage circuits electrically isolated, thereby improving the safety of the system. The seventh resistor R7 works together with the optical coupler U2 to play a shunt role, improving the anti-interference ability of the optical coupler U2. The second end of the optical coupler U2 and the second end of the seventh resistor R7 are both grounded, ensuring the stable operation of the optical coupler U2. When the first end of the optical coupler U2 receives the driving signal from the self-locking circuit 12, the photoelectric element inside the optical coupler U2 will be activated, so that the fourth end of the optical coupler U2 outputs a control signal to the enable end of the switching power supply. At this time, the output signal of the optical coupler U2 will determine the working state of the switching power supply, ensuring that when the voltage detection circuit 11 detects abnormal voltage, it can quickly cut off the output of the switching power supply, realizing effective protection. This design not only improves the response speed of the circuit, but also enhances the overall reliability and safety of the system.

[0077] As a preferred embodiment, it further comprises an eighth resistor R8, the first end of which is connected with the fourth end of the optical coupler U2, and the second end thereof is connected with the enable end of the switching power supply as the output end of the first switching circuit 13.

[0078] As shown in Figure 2 , Figure 4 , in one specific embodiment, the working process includes:

[0079] When the output voltage is lower than 36V, V1 voltage and VOUT voltage directly sample the output voltage, because the cathode voltage of TL431 (the model of the first voltage stabilizing chip U1) cannot be greater than 36V. When the output voltage is greater than 36V, VOUT connects the output voltage of the switching power supply, V1 is separately powered or connected to the output voltage in series with a diode, to ensure that the maximum voltage of the cathode of TL431 does not exceed 36V. The output voltage enters the 1 pin of U1 TL431 through resistors R5 and R6, when the voltage value of the 1 pin is high voltage 2.495V, the 2 pin and the 3 pin of TL431 are turned on, and then the PNP triode Q1 (that is, the first controllable switch) is turned on. After the PNP triode Q3 is turned on, the V1 voltage is fed back through D1 and R3, so that the voltage value of the 1 pin of U1 TL431 is higher. U1 will be continuously turned on. In addition, after Q1 is turned on, the V1 voltage drives the optocoupler U2 to be turned on through R4, so as to control the soft start SS discharge of the power supply chip U3. Because of the existence of the output capacitor, the output voltage will not be immediately discharged. By designing reasonable resistance values of R3, R5 and R6, the power supply open loop time can be set, and when the output capacitor value is lower than a certain value, the power supply can be restarted, that is, the hiccup time can be set. When the output voltage is greater than 36V, VOUT directly connects the output voltage, and V1 connects the output voltage in series with a voltage stabilizing diode D2, to ensure that the maximum voltage of the cathode of TL431 does not exceed 36V, so that the sampling of the output voltage higher than 36V can be realized without the second power supply voltage.

[0080] It can be seen that, by the high-precision reference of TL431, the precise control of the overvoltage of the power supply after the open loop is realized, and the damage of the output voltage to the rear-end load is prevented. The stored energy of the output capacitor is utilized, the self-locking after the overvoltage of the power supply is realized, the hiccup time is set through resistors R15, R6 and R14, and the loss of the power supply after the open loop is reduced.

[0081] To solve the above technical problems, the utility model provides a kind of switching power supply, including the protection circuit of the switching power supply described above. For other introduction of switching power supply, please refer to the above embodiment, this application will not be described here.

[0082] It is also important to note that the use of relational terms such as first and second, and the like, are used solely to distinguish one from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises... a" does not, without more constraints, exclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

[0083] The above description of disclosed embodiments provides enabling concepts for practicing or using the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application 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

1. A protection circuit for a switching power supply, characterized by include: A voltage detection circuit, the input terminal of which is connected to the output capacitor of the switching power supply, is used to detect the output voltage of the switching power supply. The self-locking circuit has its input terminals connected to the output terminal of the voltage detection circuit and its own feedback terminal, respectively, and its power supply terminal connected to the output capacitor of the power supply or the switching power supply. It is used to output a drive signal when the detection voltage of the voltage detection circuit reaches the voltage threshold, and to superimpose a preset voltage onto its own input terminal through its own feedback terminal. The preset voltage has a preset relationship with the voltage of the power supply. The first switching circuit has its input terminal connected to the output terminal of the self-locking circuit and its output terminal connected to the enable terminal of the switching power supply. It is used to operate when the drive signal is received to output an disabled signal to the enable terminal of the switching power supply, so that the switching power supply stops outputting. When the switching power supply stops outputting, the output capacitor automatically discharges through the self-locking circuit. When the output capacitor discharges to a preset restart value, the switching power supply restarts.

2. The protection circuit for a switching power supply according to claim 1, wherein The self-locking circuit includes: First voltage regulator chip, second switching circuit; The first terminal of the first voltage regulator chip is connected to the output terminal of the voltage detection circuit and the first terminal of the second switching circuit, the second terminal of the first voltage regulator chip is connected to the control terminal of the second switching circuit, the third terminal of the first voltage regulator chip is grounded, the second terminal of the second switching circuit is connected to the power supply or the output capacitor, and the third terminal of the second switching circuit is connected to the input terminal of the first switching circuit. The first voltage regulator chip is used to turn on its second and third terminals when the voltage at its first terminal reaches an internally set voltage threshold. The second switching circuit is used to conduct a first path between its own second and first ends, and a second path between its own second and third ends, when the second and third ends of the first voltage regulator chip are turned on.

3. The protection circuit for a switching power supply according to claim 2, wherein The second switching circuit includes: The first controllable switch and the first diode; The control terminal of the first controllable switch is connected to the second terminal of the first voltage regulator chip, the first terminal of the first controllable switch is connected to the power supply or output capacitor, the second terminal of the first controllable switch is connected to the input terminal of the first switch circuit and the anode of the first diode, and the cathode of the first diode is connected to the first terminal of the first voltage regulator chip.

4. The protection circuit for a switching power supply according to claim 3, wherein The second switching circuit also includes: Four resistors are provided. The first end of the first resistor is connected to the control terminal of the first controllable switch. The first end of the second resistor is connected to the first terminal of the first controllable switch. The second end of the second resistor is connected to the second terminal of the first resistor and the second terminal of the first voltage regulator chip. The first end of the third resistor is connected to the cathode of the first diode. The second end of the third resistor is connected to the first terminal of the first voltage regulator chip. The first end of the fourth resistor is connected to the second terminal of the first controllable switch. The second end of the fourth resistor is connected to the input terminal of the first switch circuit.

5. The protection circuit for a switching power supply according to claim 3, wherein Also includes: A voltage dividing circuit, a first end of which is connected to a first end of the first controllable switch, and a second end of which is connected to the power supply or an output capacitor, for sharing voltage when the first controllable switch is turned on.

6. The protection circuit for a switching power supply according to claim 5, wherein The voltage dividing circuit comprises: At least one zener diode, an anode of which is connected to the first end of the first controllable switch, and a cathode of which is connected to the power supply.

7. The protection circuit for a switching power supply according to claim 1, wherein The voltage detecting circuit comprises: A fifth resistor and a sixth resistor; A first end of the fifth resistor is connected to an output end of the switching power supply, a second end of the fifth resistor is connected to a first end of the sixth resistor and serves as an output end of the voltage detecting circuit, and a second end of the sixth resistor is grounded.

8. The protection circuit for a switching power supply as claimed in any one of claims 1 to 7, characterized in that, The first switching circuit comprises: An optocoupler and a seventh resistor; A first end of the optocoupler is connected to a first end of the seventh resistor and an output end of the self-locking circuit respectively, a second end of the optocoupler and a second end of the seventh resistor are both grounded, a third end of the optocoupler is grounded, and a fourth end of the optocoupler, serving as an output end of the first switching circuit, is connected to an enable end of the switching power supply.

9. The protection circuit for a switching power supply according to claim 8, wherein Further comprising: An eighth resistor, a first end of which is connected to the fourth end of the optocoupler, and a second end of which, serving as an output end of the first switching circuit, is connected to the enable end of the switching power supply.

10. A switching power supply, characterized by comprising: A protection circuit of a switching power supply comprising any one of the protection circuits according to claims 1-9.

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