Inverter circuit
By introducing power supply detection and short-circuit detection modules into the inverter circuit, automatic short-circuit detection and protection of the output port is solved, and the problem of the inverter cannot be detected before starting is improved. The security of the inverter is improved .
Patent Information
- Application Number
- CN202420860879.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-04-24
- Publication Date
- 2025-01-14
- Estimated Expiration
- 2034-04-24
AI Technical Summary
The existing inverter circuit cannot automatically perform short-circuit detection of the output port before starting, resulting in low safety and easy burnout due to short-circuit output.
An inverter circuit was designed, including a power supply module, a power supply detection module, an auxiliary power control module, an input protection module, an output protection module and a short circuit detection module. Through power supply detection and delay control, logic calculation and level adjustment, it can realize Short circuit detection and protection of the output ports ensure self-testing before inverting.
Perform output short-circuit self-test before the inverter is started, which improves the safety of the circuit, avoids damage caused by short-circuit failure, and ensures the normal operation of the inverter.
Smart Images
Figure CN222355958U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of inverters, in particular to an inverter circuit. Background Art
[0002] An inverter is a converter that converts direct current into constant frequency and constant voltage or frequency and voltage modulated alternating current. To avoid the inverter from burning out due to a short circuit in the inverter output, most existing inverter circuits will perform short circuit detection on the power output port and disconnect the power supply when a short circuit occurs. It is impossible to automatically perform short circuit detection and protection on the power output port before the inverter is started. The circuit has low safety and needs to be improved. Utility Model Content
[0003] The embodiment of the utility model provides an inverter circuit to solve the problems raised in the above background technology.
[0004] In order to achieve the above purpose, the utility model provides the following technical solutions:
[0005] An inverter circuit comprises: a power supply module, a power supply detection module, an auxiliary power control module, an input protection module, an inverter module, an output protection module, an output module and a short circuit detection module;
[0006] A power module is used to receive AC power and perform rectification and filtering on the AC power;
[0007] A power supply detection module, connected to the power supply module, for performing isolated power supply detection on the electric energy output after being processed by the power supply module, and delaying output of a first control signal;
[0008] an auxiliary power control module, connected to the power module, the power supply detection module and the output module, for reducing the voltage of the AC power connected to the power module and transmitting the reduced voltage power to the output module, and for receiving the first control signal and stopping the power transmission;
[0009] An input protection module, connected to the power module, the inverter module, the power supply detection module and the short-circuit detection module, for level-adjusting the first control signal and outputting a second control signal, for performing logic calculation on the second control signal and a third control signal output by the short-circuit detection module, and for outputting a fourth control signal when the power supply detection module detects that the power module is in a power supply state and the short-circuit detection module does not detect a short circuit, for transmitting the electric energy output by the power module to the inverter module;
[0010] Inverter module, used for inverting and filtering the input electric energy;
[0011] an output protection module, connected to the inverter module, the output module and the input protection module, and configured to receive a fourth control signal and transmit the electric energy output by the inverter module to the output module;
[0012] An output module is used for receiving electric energy and for connecting with an electric load;
[0013] The short-circuit detection module is connected to the output module, and is used to set a short-circuit threshold and perform short-circuit detection on the electric energy transmitted by the output module, and is used to output a third control signal when the output module is short-circuited.
[0014] As a further solution of the utility model: the power module includes a power interface, a first rectifier and a first capacitor; the auxiliary power control module includes a fourth resistor, a third capacitor, a fifth resistor, a first thyristor and a first switch tube; the output module includes a load interface;
[0015] Preferably, the first end of the power interface is connected to the first input end of the first rectifier and one end of the third capacitor, and is connected to the other end of the third capacitor, one end of the fifth resistor and one end of the first thyristor through the fourth resistor, the other end of the first thyristor is connected to the first end of the load interface, the other end of the fifth resistor is connected to the control end of the first thyristor and the collector of the first switching tube, the emitter of the first switching tube is grounded, the base of the first switching tube is connected to the power supply detection module, the second end of the power interface is connected to the second input end of the first rectifier, and the first output end of the first rectifier is connected to the ground end and the second output end of the first rectifier through the first capacitor.
[0016] As a further solution of the utility model: the input protection module includes a first relay switch; the inverter module includes a first inverter, a first inductor and a fourth capacitor; the output protection module includes a second relay switch; the short circuit detection module includes a sixth resistor;
[0017] Preferably, the moving end of the first relay switch is connected to the first output end of the first rectifier, the fixed end of the first relay switch is connected to the first input end of the first inverter, the second input end of the first inverter is grounded, the first output end of the first inverter is connected to one end of the fourth capacitor and the first moving end of the second relay switch through the first inductor, the first fixed end of the second relay switch is connected to the first end of the load interface, the other end of the fourth capacitor is connected to the second output end of the first inverter and the second moving end of the second relay switch, and the second fixed end of the second relay switch is connected to the second end of the load interface through the sixth resistor.
[0018] As a further solution of the utility model: the short circuit detection module also includes a seventh resistor, a first diode, a fifth capacitor, a second switch tube, an eighth resistor and a second power supply;
[0019] Preferably, the cathode of the first diode is connected to the second end of the load interface through the seventh resistor, the anode of the first diode is connected to the base of the second switching tube and the emitter and ground of the second switching tube through the fifth capacitor, and the collector of the second switching tube is connected to the input protection module and connected to the second power supply through the eighth resistor.
[0020] As a further solution of the utility model: the power supply detection module includes a first resistor, a first optical coupler, a first power supply, a second resistor, a second capacitor and a third resistor;
[0021] Preferably, the first end of the first optocoupler is connected to the first output end of the first rectifier through the first resistor, the second end of the first optocoupler is grounded, the third end of the first optocoupler is connected to the first power supply, the fourth end of the first optocoupler is connected to the first end of the third resistor, one end of the second resistor and the other end of the second resistor and the ground through the second capacitor, and the second end of the third resistor is connected to the input protection module and the base of the first switching tube.
[0022] As a further solution of the utility model: the input protection module also includes a third power supply, a third switch tube, a ninth resistor, a fourth switch tube and a first logic chip;
[0023] Preferably, the collector of the third switch tube and one end of the first relay are both connected to the third power supply, the emitter of the third switch tube is connected to the first end of the first logic chip and grounded through a ninth resistor, the second end of the first logic chip is connected to the collector of the second switch tube, the third end of the first logic chip is connected to the base of the fourth switch tube, the emitter of the fourth switch tube is grounded, and the collector of the fourth switch tube is connected to the other end of the first relay.
[0024] As a further solution of the utility model: the output protection module also includes a second relay and a fifth switch tube;
[0025] Preferably, one end of the second relay is connected to the third power supply, the other end of the second relay is connected to the collector of the fifth switch tube, the emitter of the fifth switch tube is grounded, and the base of the fifth switch tube is connected to the third end of the first logic chip.
[0026] Compared with the prior art, the beneficial effect of the utility model is as follows: after the power module of the inverter circuit of the utility model is connected to AC power, the power supply detection module performs power supply detection and delays the control of the auxiliary power control module to provide low-voltage AC power to the output module, and at the same time, the short-circuit detection module performs short-circuit detection on the output module. If the output module does not have a short-circuit fault at this time, the input protection module and the output protection module control the inverter module to start the inverter operation, and during the operation of the inverter module, if the output module has a short-circuit fault, the short-circuit detection module controls the input protection module and the output protection module to perform power-off protection, and the output short-circuit self-detection protection can be performed before the inverter operation, thereby improving the safety of the inverter circuit. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] In order to more clearly illustrate the technical solutions of the embodiments of the utility model, the drawings required for use in the description of the embodiments of the utility model will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.
[0028] Figure 1 The present invention provides a schematic block diagram of an inverter circuit.
[0029] Figure 2 A circuit diagram of an inverter circuit provided in an example of the utility model.
[0030] Figure 3 This is a connection circuit diagram of the input protection module and the output protection module provided by the example of the utility model. DETAILED DESCRIPTION
[0031] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.
[0032] In another embodiment, see Figure 1 , an inverter circuit, comprising: a power supply module 1, a power supply detection module 2, an auxiliary power control module 3, an input protection module 4, an inverter module 5, an output protection module 6, an output module 7 and a short circuit detection module 8;
[0033] Specifically, the power module 1 is used to receive AC power and perform rectification and filtering on the AC power;
[0034] A power supply detection module 2, connected to the power supply module 1, for performing isolated power supply detection on the electric energy output after being processed by the power supply module 1, and delaying output of a first control signal;
[0035] The auxiliary power control module 3 is connected to the power module 1, the power supply detection module 2 and the output module 7, and is used to reduce the voltage of the AC power connected to the power module 1 and transmit the reduced voltage power to the output module 7, and is used to receive the first control signal and stop the power transmission work;
[0036] An input protection module 4, connected to the power module 1, the inverter module 5, the power supply detection module 2 and the short-circuit detection module 8, for level-adjusting the first control signal and outputting a second control signal, for performing logic calculation on the second control signal and a third control signal output by the short-circuit detection module 8, for outputting a fourth control signal when the power supply detection module 2 detects that the power module 1 is in a power supply state and the short-circuit detection module 8 does not detect a short circuit, for transmitting the electric energy output by the power module 1 to the inverter module 5;
[0037] The inverter module 5 is used to invert and filter the input electric energy;
[0038] The output protection module 6 is connected to the inverter module 5, the output module 7 and the input protection module 4, and is used to receive the fourth control signal and transmit the electric energy output by the inverter module 5 to the output module 7;
[0039] Output module 7, used for receiving electric energy and for connecting to an electric load;
[0040] The short-circuit detection module 8 is connected to the output module 7 and is used to set a short-circuit threshold and perform short-circuit detection on the electric energy transmitted by the output module 7, and is used to output a third control signal when the output module 7 is short-circuited.
[0041] In a specific embodiment, the power supply module 1 may adopt a power supply circuit composed of a power supply interface, a rectifier and a capacitor, which may be connected to AC power and perform rectification and filtering on the AC power; the power supply detection module 2 may adopt a power supply detection circuit composed of a photocoupler, a resistor, a capacitor, etc., which may perform power supply detection on the DC power output after processing by the power supply module 1, and the capacitor may perform power supply detection to delay control of the power-off work of the auxiliary power control module 3 and the protection work of the input protection module 4; the auxiliary power control module 3 may adopt an auxiliary power control circuit composed of a capacitive resistor circuit, a thyristor, etc., which may step down the input AC power and provide the output module 7 with the power required for short-circuit detection, and the power supply detection module 2 may disconnect the transmission power; the input protection module 4 may adopt a logic chip, a transistor, a relay, etc. The input protection circuit is formed to perform logical calculations on the signals output by the power supply detection module 2 and the short-circuit detection module 8, so as to control the electric energy of the input inverter module 5 and the operation of the output protection module 6 when the power supply detection module 2 detects that the power supply module 1 is in the power supply state and the short-circuit detection module 8 does not detect a short circuit; the above-mentioned inverter module 5 can adopt an inverter circuit composed of an inverter group, an inductor, and a capacitor to achieve inversion and filtering; the above-mentioned output protection module 6 can adopt an output protection circuit composed of a transistor, a relay, etc. to transmit the electric energy output by the inverter module 5 to the output module 7; the above-mentioned output module 7 can adopt a load interface to be connected to an electrical load; the above-mentioned short-circuit detection module 8 can adopt a short-circuit detection circuit composed of a sampling resistor, a diode, a transistor, etc. to perform short-circuit detection on the output module 7 and output a high-level signal when no short circuit occurs.
[0042] In another embodiment, see Figure 1 , Figure 2 and Figure 3 The power module 1 includes a power interface, a first rectifier T1 and a first capacitor C1; the auxiliary power control module 3 includes a fourth resistor R4, a third capacitor C3, a fifth resistor R5, a first thyristor SCR1 and a first switch tube VT1; the output module 7 includes a load interface;
[0043] Specifically, the first end of the power interface is connected to the first input end of the first rectifier T1 and one end of the third capacitor C3, and is connected to the other end of the third capacitor C3, one end of the fifth resistor R5 and one end of the first thyristor SCR1 through the fourth resistor R4. The other end of the first thyristor SCR1 is connected to the first end of the load interface, the other end of the fifth resistor R5 is connected to the control end of the first thyristor SCR1 and the collector of the first switch tube VT1, the emitter of the first switch tube VT1 is grounded, and the base of the first switch tube VT1 is connected to the power supply detection module 2. The second end of the power interface is connected to the second input end of the first rectifier T1, and the first output end of the first rectifier T1 is connected to the ground end and the second output end of the first rectifier T1 through the first capacitor C1.
[0044] In a specific embodiment, the power interface is connected to an AC power supply, which will not be elaborated here; the fourth resistor R4 and the third capacitor C3 form a capacitive-resistance circuit; the first thyristor SCR1 can be a bidirectional thyristor, which is triggered to turn on by the fifth resistor R5 and triggered to turn off by the first switch tube VT1, wherein the first switch tube VT1 can be an NPN transistor.
[0045] Further, the input protection module 4 includes a first relay switch K1-1; the inverter module 5 includes a first inverter T2, a first inductor L1 and a fourth capacitor C4; the output protection module 6 includes a second relay switch K2-1; the short circuit detection module 8 includes a sixth resistor R6;
[0046] Specifically, the moving end of the first relay switch K1-1 is connected to the first output end of the first rectifier T1, the fixed end of the first relay switch K1-1 is connected to the first input end of the first inverter T2, the second input end of the first inverter T2 is grounded, the first output end of the first inverter T2 is connected to one end of the fourth capacitor C4 and the first moving end of the second relay switch K2-1 through the first inductor L1, the first fixed end of the second relay switch K2-1 is connected to the first end of the load interface, the other end of the fourth capacitor C4 is connected to the second output end of the first inverter T2 and the second moving end of the second relay switch K2-1, and the second fixed end of the second relay switch K2-1 is connected to the second end of the load interface through the sixth resistor R6.
[0047] In a specific embodiment, the first relay switch K1-1 may be a normally open switch; the first inverter T2 may be an inverter composed of IGBT, which will not be described in detail here; the second relay switch K2-1 may be a double-pole double-throw normally open switch; and the sixth resistor R6 is used as a sampling resistor.
[0048] Furthermore, the short circuit detection module 8 further includes a seventh resistor R7, a first diode D1, a fifth capacitor C5, a second switch tube VT2, an eighth resistor R8 and a second power supply VCC2;
[0049] Specifically, the cathode of the first diode D1 is connected to the second end of the load interface through the seventh resistor R7, the anode of the first diode D1 is connected to the base of the second switch tube VT2 and the emitter and the ground of the second switch tube VT2 through the fifth capacitor C5, and the collector of the second switch tube VT2 is connected to the input protection module 4 and connected to the second power supply VCC2 through the eighth resistor R8.
[0050] In a specific embodiment, the seventh resistor R7 and the first diode D1 provide a short-circuit threshold, the fifth capacitor C5 stores energy and delays the cut-off of the second switch tube VT2, and the second switch tube VT2 can be an NPN transistor.
[0051] Further, the power supply detection module 2 includes a first resistor R1, a first optical coupler U1, a first power supply VCC1, a second resistor R2, a second capacitor C2 and a third resistor R3;
[0052] Specifically, the first end of the first optocoupler U1 is connected to the first output end of the first rectifier T1 through the first resistor R1, the second end of the first optocoupler U1 is grounded, the third end of the first optocoupler U1 is connected to the first power supply VCC1, the fourth end of the first optocoupler U1 is connected to the first end of the third resistor R3, one end of the second resistor R2 and the other end of the second resistor R2 and the ground through the second capacitor C2, and the second end of the third resistor R3 is connected to the input protection module 4 and the base of the first switch tube VT1.
[0053] In a specific embodiment, the above-mentioned first optocoupler U1 can be a PC817 photoelectric coupler. When the first end of the first optocoupler U1 is energized, the third end and the fourth end of the first optocoupler U1 are turned on, and the second capacitor C2 stores energy, and the second resistor R2 and the third resistor R3 step down the voltage. When the electric energy stored in the second capacitor C2 reaches a certain value, the first switch tube VT1 and the input protection module 4 will be triggered to achieve delay control.
[0054] Furthermore, the input protection module 4 also includes a third power supply VCC3, a third switch tube VT3, a ninth resistor R9, a fourth switch tube VT4 and a first logic chip U2;
[0055] Specifically, the collector of the third switch tube VT3 and one end of the first relay are both connected to the third power supply VCC3, the emitter of the third switch tube VT3 is connected to the first end of the first logic chip U2 and is grounded through the ninth resistor R9, the second end of the first logic chip U2 is connected to the collector of the second switch tube VT2, the third end of the first logic chip U2 is connected to the base of the fourth switch tube VT4, the emitter of the fourth switch tube VT4 is grounded, and the collector of the fourth switch tube VT4 is connected to the other end of the first relay.
[0056] In a specific embodiment, the third switch tube VT3 and the fourth switch tube VT4 can both be NPN transistors; the first logic chip U2 can be selected from logic chips, and the specific model is not limited; the first relay controls the closing and opening of the first relay switch K1-1 by magnetic attraction.
[0057] Furthermore, the output protection module 6 also includes a second relay K2 and a fifth switch tube VT5;
[0058] Specifically, one end of the second relay K2 is connected to the third power supply VCC3, the other end of the second relay K2 is connected to the collector of the fifth switch tube VT5, the emitter of the fifth switch tube VT5 is grounded, and the base of the fifth switch tube VT5 is connected to the third end of the first logic chip U2.
[0059] In a specific embodiment, the fifth switch tube VT5 can be an NPN transistor; the second relay K2 controls the closing and opening of the second relay switch K2-1 by magnetic attraction.
[0060] In an inverter circuit of the present embodiment, a power interface is connected to AC power. When AC power is connected, the third capacitor C3 and the fourth resistor R4 perform a voltage reduction process and trigger the first thyristor SCR1 to turn on so as to provide low-voltage AC power for the load interface. At this time, the sixth resistor R6 performs current sampling, and the seventh resistor R7 and the first diode D1 perform short-circuit judgment. When the load interface is in a short-circuit state, the second switch tube VT2 is turned on, the second end of the first logic chip U2 is at a low level, the first relay and the second relay K2 do not work, the first relay switch K1-1 and the second relay switch K2-1 remain in a disconnected state, and at the same time, the first rectifier T1 and the first capacitor C1 perform rectification and filtering, the first optical coupler U1 is turned on, and the second capacitor C2 stores energy. When the electric energy stored in the second capacitor C2 reaches the first switch tube VT1 and the third switch tube VT3 After the trigger voltage, the first switch tube VT1 and the third switch tube VT3 are turned on, and the first thyristor SCR1 is turned off. If the load interface is not short-circuited during the time period when the electric energy stored in the second capacitor C2 does not reach the trigger voltage, when the second capacitor C2 triggers the first switch tube VT1 and the third switch tube VT3 to turn on, the first thyristor SCR1 is turned off, and the first end of the first logic chip U2 is high level. The first logic chip U2 controls the fourth switch tube VT4 and the fifth switch tube VT5 to turn on, so that the first relay controls the first relay switch K1-1 to close, and the second relay K2 controls the second relay switch K2-1 to close, and the first inverter T2 starts working. When the load interface is short-circuited, the second switch tube VT2 is turned on, the first logic chip U2 outputs a low level, and the first relay switch K1-1 and the second relay switch K2-1 are disconnected for short-circuit protection.
Claims
1. An inverter circuit, characterized in that: The inverter circuit includes: a power supply module, a power supply detection module, an auxiliary power control module, an input protection module, an inverter module, an output protection module, an output module and a short circuit detection module; The power module is used to receive AC power and perform rectification and filtering on the AC power; The power supply detection module is connected to the power supply module and is used to perform isolated power supply detection on the electric energy output after being processed by the power supply module, and delay output of the first control signal; The auxiliary power control module is connected to the power module, the power supply detection module and the output module, and is used to reduce the voltage of the AC power connected to the power module and transmit the reduced voltage power to the output module, and is used to receive the first control signal and stop the power transmission work; The input protection module is connected to the power module, the inverter module, the power supply detection module and the short-circuit detection module, and is used to adjust the level of the first control signal and output the second control signal, and is used to perform logic calculation on the second control signal and the third control signal output by the short-circuit detection module, and is used to output a fourth control signal when the power supply detection module detects that the power module is in a power supply state and the short-circuit detection module does not detect a short circuit, and is used to transmit the electric energy output by the power module to the inverter module; The inverter module is used to invert and filter the input electric energy; The output protection module is connected to the inverter module, the output module and the input protection module, and is used to receive the fourth control signal and transmit the electric energy output by the inverter module to the output module; The output module is used for receiving electric energy and for connecting to an electric load; The short-circuit detection module is connected to the output module, and is used to set a short-circuit threshold and perform short-circuit detection on the electric energy transmitted by the output module, and is used to output a third control signal when the output module is short-circuited.
2. The inverter circuit according to claim 1, characterized in that: The power module includes a power interface, a first rectifier and a first capacitor; the auxiliary power control module includes a fourth resistor, a third capacitor, a fifth resistor, a first thyristor and a first switch tube; the output module includes a load interface; The first end of the power interface is connected to the first input end of the first rectifier and one end of the third capacitor, and is connected to the other end of the third capacitor, one end of the fifth resistor and one end of the first thyristor through the fourth resistor. The other end of the first thyristor is connected to the first end of the load interface, the other end of the fifth resistor is connected to the control end of the first thyristor and the collector of the first switch tube, the emitter of the first switch tube is grounded, and the base of the first switch tube is connected to the power supply detection module. The second end of the power interface is connected to the second input end of the first rectifier, and the first output end of the first rectifier is connected to the ground end and the second output end of the first rectifier through the first capacitor.
3. The inverter circuit according to claim 2, characterized in that: The input protection module includes a first relay switch; the inverter module includes a first inverter, a first inductor and a fourth capacitor; the output protection module includes a second relay switch; the short circuit detection module includes a sixth resistor; The moving end of the first relay switch is connected to the first output end of the first rectifier, the fixed end of the first relay switch is connected to the first input end of the first inverter, the second input end of the first inverter is grounded, the first output end of the first inverter is connected to one end of the fourth capacitor and the first moving end of the second relay switch through the first inductor, the first fixed end of the second relay switch is connected to the first end of the load interface, the other end of the fourth capacitor is connected to the second output end of the first inverter and the second moving end of the second relay switch, and the second fixed end of the second relay switch is connected to the second end of the load interface through the sixth resistor.
4. The inverter circuit according to claim 3, characterized in that: The short circuit detection module also includes a seventh resistor, a first diode, a fifth capacitor, a second switch tube, an eighth resistor and a second power supply; The cathode of the first diode is connected to the second end of the load interface through the seventh resistor, the anode of the first diode is connected to the base of the second switch tube and the emitter and the ground terminal of the second switch tube through the fifth capacitor, and the collector of the second switch tube is connected to the input protection module and the second power supply through the eighth resistor.
5. The inverter circuit according to claim 4, characterized in that: The power supply detection module includes a first resistor, a first optical coupler, a first power supply, a second resistor, a second capacitor and a third resistor; The first end of the first optocoupler is connected to the first output end of the first rectifier through the first resistor, the second end of the first optocoupler is grounded, the third end of the first optocoupler is connected to the first power supply, the fourth end of the first optocoupler is connected to the first end of the third resistor, one end of the second resistor and the other end of the second resistor and the ground through the second capacitor, and the second end of the third resistor is connected to the input protection module and the base of the first switch tube.
6. The inverter circuit according to claim 5, characterized in that: The input protection module also includes a third power supply, a third switch tube, a ninth resistor, a fourth switch tube and a first logic chip; The collector of the third switch tube and one end of the first relay are both connected to the third power supply, the emitter of the third switch tube is connected to the first end of the first logic chip and is grounded through a ninth resistor, the second end of the first logic chip is connected to the collector of the second switch tube, the third end of the first logic chip is connected to the base of the fourth switch tube, the emitter of the fourth switch tube is grounded, and the collector of the fourth switch tube is connected to the other end of the first relay.
7. The inverter circuit according to claim 6, characterized in that: The output protection module also includes a second relay and a fifth switch tube; One end of the second relay is connected to the third power supply, the other end of the second relay is connected to the collector of the fifth switch tube, the emitter of the fifth switch tube is grounded, and the base of the fifth switch tube is connected to the third end of the first logic chip.