Negative voltage switch control circuit and test system
By designing the PMOS transistor and filter module in the negative voltage switch control circuit, the problem of damage to the negative voltage power supply chip was solved, and safe control and stable operation of the power supply were achieved. Combined with positive voltage switch control, the control efficiency and safety of the power supply were improved.
Patent Information
- Application Number
- CN202422720290.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-08
- Publication Date
- 2025-11-18
- Estimated Expiration
- 2034-11-08
AI Technical Summary
In existing testing systems, when the negative voltage power supply chip outputs a negative voltage, it is directly connected to the input pin via GPIO. This causes the output voltage to exceed the GPIO threshold, resulting in controller damage and subsequent circuit failure.
A negative voltage switch control circuit is adopted, which uses a PMOS transistor and a step-down resistor to protect the controller. The gate grounding design of the PMOS transistor avoids damage caused by excessive current, and the filtering module reduces noise interference. Combined with a positive voltage switch control circuit, different control circuits are selected for on/off control according to the power supply output level signal.
It achieves safe control of the power supply, avoids power supply damage caused by overcurrent and overvoltage, improves the safety and stability of the circuit, and ensures the normal operation of the power supply.
Smart Images
Figure CN223566054U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to the switch control field especially, and it relates to a negative voltage switch control circuit and test system. BACKGROUND
[0002] In the prior art test system, the power supply in the test system usually needs to be controlled to meet the test requirements.
[0003] The commonly used switch control method is to control the input pin of the power supply chip through the GPIO of the controller, but when the negative voltage power supply chip works to output negative voltage, directly connecting the GPIO with the input pin will cause the output voltage to exceed the threshold value of the GPIO and damage the controller, and further cause circuit failure. SUMMARY
[0004] The utility model discloses at least one of the technical problems in the prior art is solved, and therefore the utility model provides a negative voltage switch control circuit, which can realize power supply negative voltage switch control and protect the control circuit.
[0005] The first aspect embodiment of the utility model provides a negative voltage switch control circuit for controlling the on-off of power supply output negative voltage signal, and the negative voltage switch control circuit comprises: a first controller, the first controller is used for outputting a first level signal, a first switch control module, one end of the first switch control module is connected with the output end of the first controller, and the first switch control module is used for receiving the first level signal sent by the first controller, and the other end is connected with the enable end of the power supply, and the first switch control module is used for sending the corresponding on-off signal to the power supply according to the first level signal.
[0006] The negative voltage switch control circuit provided by the utility model embodiment has at least the following beneficial effects: when the power supply outputs negative voltage signal, the first switch control module sends the corresponding on-off signal to the power supply according to the level signal sent by the first controller, so that the control of the power supply opening and closing is realized, and the damage of the power supply caused by excessive current can be avoided, and the safety of circuit operation is improved.
[0007] In some embodiments of the utility model, the first switch control module comprises: a PMOS tube, the source of the PMOS tube is connected with the output end of the first controller and is used for receiving the first level signal sent by the first controller, the drain of the PMOS tube is connected with the enable end of the power supply and is used for outputting the corresponding switch signal to the power supply according to the first level signal, and the gate of the PMOS tube is grounded.
[0008] In some embodiments of the utility model, the first switch control module further includes: a voltage drop resistor, one end of the voltage drop resistor is connected with the drain of the PMOS tube, and the other end is connected with the enable end of the power supply.
[0009] In some embodiments of the utility model, the negative voltage switch control circuit further includes: a first filter module, an output end of the first filter module is connected with an input end of the power supply, and the other end of the first filter module is grounded.
[0010] In some embodiments of the utility model, the first filter module includes: a voltage source, a positive pole of the voltage source is connected with the input end of the power supply, and a negative pole is grounded;A first capacitor is connected with the voltage source in parallel, and is used for processing the voltage signal output by the voltage source.
[0011] In some embodiments of the utility model, the negative voltage switch control circuit further includes: a second filter module, one end of the second filter module is connected with an output end of the power supply, the other end of the second filter module is connected with an input end of the power supply, and the other end is grounded.
[0012] In some embodiments of the utility model, the first filter module includes: a second capacitor, one end of the second capacitor is connected with an output end of the power supply, the other end of the second capacitor is connected with an input end of the power supply, and the other end is connected with a load resistor, and the load resistor is connected with the second capacitor in parallel.
[0013] The second aspect embodiment of the utility model provides a test system, which comprises: a power supply, the power supply is used for outputting negative voltage signals or positive voltage signals;The negative voltage switch control circuit of the first aspect embodiment of the utility model, the negative voltage switch control circuit is used for controlling the on-off of the power supply when the power supply outputs negative voltage signals;And a positive voltage switch control circuit, the positive voltage switch control circuit includes a positive voltage control module, and the positive voltage switch control circuit is used for controlling the on-off of the power supply when the power supply outputs positive voltage signals.
[0014] The test system provided by the utility model has at least the following technical effects: the test system includes a power supply, a negative voltage switch control circuit and a positive voltage switch control circuit, the negative voltage switch control circuit and the positive voltage switch control circuit can be connected with different control circuits for on-off control according to different power supply output level signals, the control efficiency of the power supply is improved, the power supply and the control circuit can be protected, the damage of the power supply caused by overcurrent, overvoltage and the like is avoided, and the normal operation of the power supply is ensured.
[0015] In some embodiments of the utility model, the power supply includes: control chip, the control chip is used for receiving and according to the switch signal is opened and closed operation, first NMOS pipe, the grid of first NMOS pipe is connected with the second control pin of control chip, the source is connected with the ground pin of control chip, the drain is grounded, second NMOS pipe, the grid of second NMOS pipe is connected with the first control pin of control chip, the source is grounded, the drain is connected with external voltage source, inductance, be arranged between the first NMOS pipe, second NMOS pipe and ground, one end of inductance is connected with the drain of first NMOS pipe, the source of second NMOS pipe, the other end is grounded, and the inductance is used to store the electric energy generated by the power supply.
[0016] In some embodiments of the utility model, the positive voltage switch control circuit includes: a second controller for outputting a second level signal, and a second switch control module for sending a corresponding on-off signal to the power supply according to the second level signal, wherein the second switch control module includes: an NMOS transistor, a grid of the NMOS transistor is connected with an output end of the second controller, for receiving a second level signal sent by the second controller, a drain of the NMOS transistor is connected with an enable end of the power supply, and a user outputs a corresponding switch signal to the power supply according to the second level signal, and a source of the NMOS transistor is grounded.
[0017] Additional aspects and advantages of the utility model will be partially given in the following description, some will become apparent from the following description, or be understood by the practice of the utility model. BRIEF DESCRIPTION OF DRAWINGS
[0018] In order to more clearly illustrate the technical scheme in the embodiments of the utility model or related technologies, the following will briefly introduce the drawings needed to be used in the description of the embodiments of the utility model or related technologies, and obviously, the drawings in the following description are only some embodiments of the utility model, and for those skilled in the art, other related drawings can also be obtained according to these drawings without creating labor.
[0019] Figure 1 It is the connection schematic diagram of negative voltage switch control circuit of the utility model embodiment;
[0020] Figure 2 It is the circuit schematic diagram of negative voltage switch control circuit of the utility model embodiment;
[0021] Figure 3 It is the connection schematic diagram of test system of the utility model embodiment;
[0022] Figure 4The utility model discloses a circuit schematic drawing in the positive voltage switch control circuit of the embodiment test system.
[0023] Reference signs:
[0024] The first switch control module 100, the power supply 200, the control chip 210, the first controller 300, the first filter module 400, the second filter module 500, the second switch control module 600 and the second controller 700. DETAILED DESCRIPTION
[0025] The embodiments of the utility model are described in detail below, and the examples of the embodiments are shown in the drawings, wherein the same or similar reference signs represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary, only for explaining the utility model, and cannot be understood as limiting the utility model.
[0026] In the description of the present application, if the first, the second is described only for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features or the sequence of indicated technical features.
[0027] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "exemplary embodiment", "example", "specific example" or "some examples" means that the specific features, structures, materials or characteristics described in combination with the embodiment or example are included in at least one embodiment or example of the present application. In the specification, the exemplary description of the above terms does not necessarily mean the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable way.
[0028] The following refers to Figure 1 The negative voltage switch control circuit according to the embodiment of the utility model is described.
[0029] As Figure 1 As shown in the figure, the negative voltage switch control circuit includes a first controller 300 and a first switch control module 100, which is used for controlling the on-off of the power supply 200 output negative voltage signal, the first controller 300 is used for outputting the first level signal, one end of the first switch control module 100 is connected with the output end of the first controller 300, which is used for receiving the first level signal sent by the first controller 300, and the other end is connected with the enable end of the power supply 200, which is used for sending the corresponding on-off signal to the power supply 200 according to the first level signal.
[0030] In the prior art, the controller is usually connected with the enable pin of the power supply 200, and the controller is used to control the switch of the power supply 200, but in this way, when the power supply 200 outputs a negative voltage, the controller will be damaged due to the negative voltage value exceeding the threshold value of the controller, and the whole circuit cannot work normally. Therefore, the negative voltage switch control circuit is provided with a first switch control module 100, one end of which is connected with the first controller 300, and the other end is connected with the enable end of the power supply 200, and the first switch control module 100 controls the on-off of the power supply 200 according to the level signal sent by the first controller 300. The setting mode of the utility model can avoid the direct contact of the first controller 300 and the power supply 200, so as to protect the first controller 300 from being damaged due to overvoltage.
[0031] The negative voltage switch control circuit provided by the utility model has at least the following beneficial effects: when the power supply 200 outputs a negative voltage signal, the first switch control module 100 sends the corresponding on-off signal to the power supply 200 according to the level signal sent by the first controller 300, so as to realize the control of the opening and closing of the power supply 200, and at the same time, the damage of the power supply 200 due to excessive current can be avoided, and the safety of the circuit operation is improved.
[0032] In some embodiments of the utility model, reference is made to Figure 1 and Figure 2 The first switch control module 100 includes a PMOS tube, the source of the PMOS tube is connected with the output end of the first controller 300, is used for receiving the first level signal sent by the first controller 300, the drain of the PMOS tube is connected with the enable end of the power supply 200, is used for outputting the corresponding switch signal to the power supply 200 according to the first level signal, and the gate of the PMOS tube is grounded.
[0033] Specifically, when the first level signal sent by the first controller 300 is a low level signal, since the source of the PMOS tube is connected with the output end of the first controller 300, the source voltage is 0V. At this time, the source voltage of the PMOS tube is equal to the gate voltage, and the PMOS tube is not conductive. When the PMOS tube is not conductive, the drain is in a high resistance state, and no current is transmitted to the enable end of the power supply 200, so that the power supply 200 does not work at this time.
[0034] When the first level signal sent by the first controller 300 is a high level signal, the voltage of the source of the PMOS tube will be pulled high, for example, the level signal is 3.3V, that is, the voltage of the source will rise to 3.3V. At this time, the voltage of the source is greater than the voltage of the gate, the PMOS tube is turned on, and the voltage of the drain is pulled high to 3.3V as the PMOS tube is turned on. It can be understood that the size of the first level signal sent by the first controller 300 can be set according to actual use requirements. Since the drain of the PMOS tube is connected to the enable end of the power supply 200, when the voltage of the drain rises to 3.3V, the power supply 200 is turned on and starts to generate a negative voltage. With the generation of the negative voltage, the enable end of the power supply 200 also appears a negative voltage, but because the PMOS tube normally works when the voltage of the source is greater than the voltage of the drain, the power supply 200 can still work normally, and damage to the PMOS tube and the power supply 200 is avoided, thereby playing a circuit protection role.
[0035] In some embodiments of the utility model, as shown in Figure 2 The first switch control module 100 further includes a voltage reduction resistor R1, one end of the voltage reduction resistor R1 is connected to the drain of the PMOS tube, and the other end is connected to the enable end of the power supply 200.
[0036] Specifically, in order to avoid damage to the PMOS tube and the negative voltage switch control circuit caused by the continuous rise of the voltage of the enable end of the power supply 200, the first switch control module 100 provided by the utility model further includes a voltage reduction resistor R1, one end of the voltage reduction resistor R1 is connected to the drain of the PMOS tube, and the other end is connected to the enable end of the power supply 200. Since the resistance value of the voltage reduction resistor R1 is very large, the current flowing from the PMOS tube to the enable end of the power supply 200 is very small, which avoids damage to the PMOS tube caused by excessive current, thereby preventing the situation that the power supply 200 cannot be controlled from occurring, and further achieving protection of the entire circuit. It can be understood that in the embodiment, the resistance value of the voltage reduction resistor R1 is 1kΩ, and the specific resistance value can be set according to actual use requirements.
[0037] In some embodiments of the utility model, as shown in Figure 1 The negative voltage switch control circuit further includes a first filter module 400, one end of the first filter module 400 is connected to the input end of the power supply 200, and the other end of the first filter module 400 is grounded.
[0038] Specifically, the negative voltage switch control circuit provided by the utility model further includes a first filter module 400, one end of the first filter module 400 is connected to the input end of the power supply 200, and the other end of the first filter module 400 is grounded. By arranging the first filter module 400, noise filtering and other operations can be performed on the input voltage input to the power supply 200, thereby reducing the influence of voltage fluctuation, noise interference and other problems on the output of the power supply 200.
[0039] In some embodiments of the utility model, as shown in Figure 2 The first filter module 400 includes a voltage source U and a first capacitor C in The positive electrode of the voltage source U is connected with the input end of the power supply 200, and the negative electrode is grounded; the first capacitor C in Is connected in parallel with the voltage source U, and is used for processing the voltage signal output by the voltage source U.
[0040] Specifically, the first filter module includes a voltage source U and a first capacitor C in , wherein the negative electrode of the voltage source U is grounded, and the positive electrode is connected with the input end of the power supply 200, for delivering voltage to the power supply 200 to ensure the normal operation of the power supply 200. The first capacitor C in Is connected in parallel with the voltage source U, for eliminating the high-frequency interference of the voltage signal output by the voltage source U, so as to achieve the effect of filtering. It can be conceived that other circuit structures with similar functions such as inductive filtering and complex filtering can also be used.
[0041] In some embodiments of the utility model, as shown in Figure 2 The negative voltage switch control circuit further includes a second filter module 500, one end of the second filter module 500 is connected with the output end of the power supply 200, the other end is connected with the input end of the power supply 200, and the other end is grounded. By setting the second filter module, the output voltage of the power supply 200 can be filtered, so as to improve the stability and reliability of the entire circuit.
[0042] In some embodiments of the utility model, as shown in Figure 2 The second filter module 500 includes a second capacitor C out And a load resistor R2, one end of the second capacitor C out Is connected with the output end of the power supply 200, the other end is connected with the input end of the power supply 200, and the other end is grounded; the load resistor R2 is connected in parallel with the second capacitor C out .
[0043] Specifically, the second filter module includes a second capacitor C out And a load resistor R2, the positive electrode of the second capacitor C out Is connected with the input end of the power supply 200 and the ground respectively, and the negative electrode is connected with the output end of the power supply 200. The second capacitor C out Is used for filtering the noise and alternating current signal of the output voltage of the power supply 200, so as to ensure the stability of the output voltage, and further improve the stability and reliability of the circuit system.
[0044] The utility model also provides a test system, as shown in Figure 3As shown, the detection system comprises a power supply 200, a positive voltage switch control circuit and the negative voltage switch control circuit of the utility model. The power supply 200 is used to output a negative voltage signal or a positive voltage signal; the negative voltage switch control circuit is used to control the on-off of the power supply 200 when the power supply 200 outputs the negative voltage signal; and the positive voltage switch control circuit comprises a positive voltage control module, and the positive voltage switch control circuit is used to control the on-off of the power supply 200 when the power supply 200 outputs the positive voltage signal.
[0045] Specifically, the detection system comprises a power supply 200, a negative voltage switch control circuit and a positive voltage switch control circuit. The on-off of the power supply 200 is controlled by the negative voltage switch control circuit when the power supply 200 outputs a negative voltage; and the on-off of the power supply 200 is controlled by the positive voltage switch control circuit when the power supply 200 outputs a positive voltage. Different switch control circuits are used for control according to the positive and negative of the output voltage, so that the damage of the power supply 200 and the control circuit caused by overcurrent and overvoltage can be effectively reduced, thereby ensuring the normal operation of the power supply 200 and the whole detection system.
[0046] The test system provided by the utility model has at least the following technical effects: the test system comprises a power supply 200, a negative voltage switch control circuit and a positive voltage switch control circuit, the negative voltage switch control circuit and the positive voltage switch control circuit are connected to different control circuits for on-off control according to the different output level signals of the power supply 200, the control efficiency of the power supply 200 is improved, the power supply 200 and the control circuit can be protected, the damage of the power supply 200 caused by overcurrent and overvoltage is avoided, and the normal operation of the power supply 200 is ensured.
[0047] In some embodiments of the utility model, as shown in Figures 1 to 4 As shown, the power supply 200 comprises a control chip 210, a first NMOS tube (NMOS1), a second NMOS tube (NMOS2) and an inductor L1. The control chip 210 is used to receive and perform on-off operation according to a switch signal. The gate of the first NMOS tube (NMOS1) is connected with the second control pin Ctrl2 of the control chip 210, the source is connected with the ground pin GND of the control chip 210, and the drain is grounded. The gate of the second NMOS tube (NMOS2) is connected with the first control pin Ctrl1 of the control chip 210, the source is grounded, and the drain is connected with an external voltage source U. The inductor L1 is arranged between the first NMOS tube (NMOS1), the second NMOS tube (NMOS2) and the ground. One end of the inductor L1 is connected with the drain of the first NMOS tube (NMOS1) and the source of the second NMOS tube (NMOS2), and the other end is grounded, and is used to store the electric energy generated by the power supply 200.
[0048] Specifically, the power supply 200 includes a control chip 210, a first NMOS tube (NMOS1), a second NMOS tube (NMOS2) and an inductor L1. The two NMOS tubes are synchronous out-of-phase switches, and the inductor L1 can store energy of an electric signal emitted by the power supply 200, and the energy stored and released by the inductor L1 is controlled through the NMOS1 and the NMOS2, so that the voltage conversion of rising and falling can be realized, for example, the voltage of 12V input is converted into the voltage of 3V for output, so as to meet the use demand of users for different output voltages and improve the versatility of the product.
[0049] In some embodiments of the utility model, reference Figure 4 The positive voltage switch control circuit includes a second controller 700 and a second switch control module 600, the second controller 700 is used to output a second level signal, and the second switch control module 600 is used to send a corresponding on-off signal to the power supply 200 according to the second level signal, wherein the second switch control module 600 includes an NMOS tube (NMOS3), the gate of the NMOS tube (NMOS3) is connected with the output end of the second controller 700, is used to receive the second level signal emitted by the second controller 700, the drain of the NMOS tube (NMOS3) is connected with the enable end of the power supply 200, the user outputs the corresponding switch signal to the power supply 200 according to the second level signal, and the source of the NMOS tube (NMOS3) is grounded.
[0050] Specifically, when the power supply 200 outputs a positive voltage signal, the on-off of the power supply 200 is controlled by the positive voltage switch control circuit. The positive voltage switch control circuit is composed of a second controller 700 and a second switch control module 600, and the second switch control module 600 includes an NMOS tube (NMOS3), the gate of the NMOS tube (NMOS3) is connected with the output end of the second controller 700, the drain is connected with the enable end of the power supply 200 and connected with an external voltage source, and the source is grounded.
[0051] When the second level signal emitted by the second controller 700 is a high level signal, the gate of the NMOS tube (NMOS3) will be pulled up, for example, the level signal is 3.3V, that is, the voltage of the gate will rise to 3.3V, at this time, the gate voltage is greater than the source voltage, and the NMOS tube (NMOS3) will be turned on. With the conduction of the NMOS tube (NMOS3), the drain voltage will approach 0V, and since the drain of the NMOS tube (NMOS3) is connected with the enable end of the power supply 200, the power supply 200 cannot work at this time.
[0052] When the second level signal sent by the second controller 700 is a low level signal, the gate of the NMOS transistor (NMOS3) is 0V, at this time the gate voltage is equal to the source voltage, and the NMOS transistor (NMOS3) is not turned on. Since the drain of the NMOS transistor (NMOS3) is also connected to an external voltage source, the voltage of the drain will be pulled up to the output voltage of the voltage source, such as 3.3V, at this time the power supply 200 will be turned on and start to generate a positive voltage. With the generation of the positive voltage, the enable end of the power supply 200 will also appear a positive voltage, but because the NMOS transistor (NMOS3) normally works when the drain voltage is greater than the source voltage, the power supply 200 can still work normally, and will not damage the NMOS transistor (NMOS3) and the power supply 200, thereby playing a circuit protection role, and meeting the working requirements when the power supply 200 outputs a positive voltage.
[0053] The embodiments of the utility model are explained in detail above in combination with the drawings, but the utility model is not limited to the above-mentioned embodiments, and various changes can be made within the knowledge range possessed by the ordinary skilled in the art without departing from the purpose of the utility model. In addition, the embodiments of the utility model and the features in the embodiments can be combined with each other without conflict.
Claims
1. A negative voltage switch control circuit, characterized by, The negative voltage switch control circuit comprises: a first controller configured to output a first level signal; a first switch control module connected at one end to the output end of the first controller and configured to receive the first level signal output by the first controller, and connected at the other end to the enable end of the power supply and configured to send a corresponding on-off signal to the power supply according to the first level signal.
2. The negative voltage switch control circuit according to claim 1, characterized by The first switch control module comprises: a PMOS tube, the source of which is connected to the output end of the first controller and configured to receive the first level signal output by the first controller, the drain of which is connected to the enable end of the power supply and configured to output a corresponding switch signal to the power supply according to the first level signal, and the gate of which is grounded.
3. The negative voltage switch control circuit of claim 2, wherein, The first switch control module further comprises: a voltage drop resistor, one end of which is connected to the drain of the PMOS tube and the other end of which is connected to the enable end of the power supply.
4. The negative voltage switching control circuit according to claim 1 or 2, characterized by The negative voltage switch control circuit further comprises: a first filter module, the output end of which is connected to the input end of the power supply, and the other end of which is grounded.
5. The negative voltage switch control circuit according to claim 4, characterized by The first filter module comprises: a voltage source, the positive pole of which is connected to the input end of the power supply and the negative pole of which is grounded; a first capacitor, which is connected in parallel to the voltage source and configured to process the voltage signal output by the voltage source.
6. The negative voltage switching control circuit according to claim 1 or 2, characterized by The negative voltage switch control circuit further comprises: a second filter module, one end of which is connected to the output end of the power supply and the other end of which is connected to the input end of the power supply and grounded.
7. The negative voltage switch control circuit according to claim 6, characterized by The second filter module comprises: a second capacitor, one end of which is connected to the output end of the power supply and the other end of which is connected to the input end of the power supply and grounded; a load resistor, which is connected in parallel to the second capacitor.
8. A test system, characterized by The negative voltage switch control circuit comprises: a power supply configured to output a negative voltage signal or a positive voltage signal; the negative voltage switch control circuit according to any one of claims 1 to 7, configured to control the on-off of the power supply when the power supply outputs a negative voltage signal; and a positive voltage switch control circuit comprising a positive voltage control module, configured to control the on-off of the power supply when the power supply outputs a positive voltage signal.
9. The test system of claim 8, wherein, The power supply comprises: a control chip configured to receive and perform on-off operation according to a switch signal; a first NMOS tube, the gate of which is connected to the second control pin of the control chip, the source of which is connected to the ground pin of the control chip, and the drain of which is grounded; a second NMOS tube, the gate of which is connected to the first control pin of the control chip, the source of which is grounded, and the drain of which is connected to an external voltage source; An inductor is arranged between the first NMOS transistor, the second NMOS transistor and the ground, one end of the inductor is connected with the drain of the first NMOS transistor and the source of the second NMOS transistor, and the other end is grounded, and the inductor is used for storing the electric energy generated by the power supply.
10. The test system of claim 9, wherein, The positive voltage switch control circuit comprises: a second controller configured to output a second level signal; a second switch control module configured to send a corresponding on-off signal to the power supply according to the second level signal; The second switch control module comprises an NMOS transistor, the gate of the NMOS transistor is connected with the output end of the second controller, and is configured to receive the second level signal sent by the second controller, the drain of the NMOS transistor is connected with the enable end of the power supply, and the NMOS transistor is configured to output a corresponding switch signal to the power supply according to the second level signal, and the source of the NMOS transistor is grounded.