Surge protection circuit control method, system and air conditioning equipment

Abstract

The present invention relates to the field of surge protection circuit control technology, and specifically provides a control method, system and air conditioning equipment for a surge protection circuit, aiming to solve the technical problem of avoiding the heating caused by the residual current of the air conditioner compressor or the fan flowing through the PTC resistor, thereby inducing the frequency conversion module to be unable to power on normally. To this end, the method of the present invention includes the following steps: when the DC bus voltage of the inverter is undervoltage and / or the phase loss detection circuit detects a phase loss fault, after stopping the operation of the compressor or the fan and turning off the output of the PWM pulse width modulation, the power relay is disconnected after a delay period of time, so that the residual current of the compressor or the fan passes through the relay. When the above method is adopted, the present invention can not only better realize the surge protection function, but also avoid the heating caused by the residual current of the air conditioner compressor or the fan flowing through the PTC resistor, resulting in the air conditioner being unable to power on normally, thereby ensuring the safe, reliable and normal operation of the air conditioning circuit.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit control, and in particular to a control method and system for a surge protection circuit and air conditioning equipment. Background Art

[0002] Among major air conditioner manufacturers, surge protection solutions are already very mature technologies, and each company has also achieved good results in suppressing surge currents. When the air conditioner inverter module has a surge protection function, most surge protection circuits use relays + thermistors PTC / cement resistors. When powered on, the PTC / cement resistor is first connected to the main circuit to prevent excessive charging current from impacting the rectifier diode and causing damage. After the electrolytic capacitor in the main circuit is charged, the relay is attracted to short-circuit the PTC / cement resistor, thus achieving the surge protection function. However, other problems caused by the surge protection circuit need to be considered in detail. The surge protection function is also used in the case of a phase loss in the power grid or a low voltage in the power grid. That is, when the grid loses a phase or the grid voltage is too low, the power relay is disconnected and the PTC is reconnected to prevent a large inrush current. Since the power relay is disconnected, the PTC is connected to the main circuit. At this time, the current of the air-conditioning compressor or the current of the fan may still remain. This current flowing through the PTC will cause the PTC to heat up. If the room temperature is high and this is repeated several times, the temperature of the PTC will rise a lot, resulting in failure to charge normally and the frequency conversion module cannot be powered on and run normally.

[0003] Therefore, it is necessary to propose a control scheme with surge protection function, which can not only realize the surge protection function better, but also avoid the problem of heating caused by the air-conditioning compressor current or the residual current of the fan flowing through the PTC resistor, thereby inducing the problem of the frequency conversion module failing to power on normally, so as to ensure the safe, reliable and normal operation of the air-conditioning circuit. Summary of the invention

[0004] In order to overcome the above defects, the present invention is proposed to solve or at least partially solve the technical problem of how to avoid the frequency conversion module from being unable to power on normally due to heating caused by residual current of the air-conditioning compressor or the fan flowing through the PTC resistor while achieving a better anti-surge function. The present invention provides a control method, system and air-conditioning equipment for an anti-surge circuit to solve the above technical problems.

[0005] In a first aspect, a control method for a surge protection circuit is provided, comprising:

[0006] When the inverter's DC bus voltage is undervoltage and / or the phase loss detection circuit detects a phase loss fault,

[0007] After stopping the operation of the compressor or fan and turning off the PWM pulse width modulation output, a delay is made before disconnecting the power relay to allow the residual current of the compressor or fan to pass through the relay.

[0008] Among them, undervoltage means that the bus voltage of the DC bus after rectification and filtering in the inverter is lower than the rated voltage;

[0009] Among them, the phase failure means that one phase of the three-phase input power supply of the frequency conversion module is missing;

[0010] If the DC bus voltage of the inverter is lower than a preset threshold voltage, it indicates that undervoltage occurs;

[0011] If the phase loss detection circuit detects that there is a phase loss fault when the three-phase power supply is input and outputs a phase loss fault alarm signal, it means that a phase loss fault is detected;

[0012] The threshold voltage is -30% of the rated voltage value, and the rated voltage is the optimal voltage when the frequency converter works normally for a long time.

[0013] Among them, "delaying a period of time before disconnecting the power relay" specifically includes:

[0014] The built-in timer is used to start timing, and after a delay of 10ms, the power relay is controlled to disconnect through the amplifier circuit.

[0015] Wherein, the amplifying circuit comprises: two triodes and one or more resistors;

[0016] Short circuit refers to a method of connecting power in a circuit by a partial short circuit that does not damage the electronic components but temporarily stops the electronic components from working.

[0017] A PTC resistor is a thermistor with a positive temperature coefficient whose resistance value increases as the temperature increases.

[0018] Delay for a period of time before disconnecting the power relay to allow the residual current of the compressor or fan to pass through the relay, including:

[0019] During the delay of 10 ms, the two transistors control the switch of the power relay to be in a closed state, short-circuiting the PTC resistor of the surge protection circuit, and the residual current of the compressor or fan flows through the switch of the power relay;

[0020] After the delay of 10 ms, the switch of the power relay controlled by the two transistors is in an off state;

[0021] When the power is turned on again, the PTC resistor is connected to the main circuit;

[0022] When the electrolytic capacitor in the main circuit is fully charged, the switch of the power relay is closed to short-circuit the PTC resistor again.

[0023] In a second aspect, a control system of a surge protection circuit is provided, wherein the surge protection circuit specifically comprises:

[0024] A PTC resistor, one end of which is connected to the main circuit, and the PTC resistor is connected in parallel with the switch of the power relay;

[0025] The power relay has one end connected to the amplifier circuit, and the power relay is connected in parallel with the rectifier diode D1;

[0026] When the DC bus voltage of the inverter is undervoltage and / or the phase loss detection circuit detects a phase loss fault, after stopping the operation of the compressor or fan and turning off the PWM pulse width modulation output, the power relay is controlled by the amplifier circuit to be disconnected after a delay period of time, so that the residual current of the compressor or fan passes through the relay.

[0027] Among them, undervoltage means that the bus voltage of the DC bus after rectification and filtering in the inverter is lower than the rated voltage;

[0028] Among them, the phase failure means that one phase of the three-phase input power supply of the frequency conversion module is missing;

[0029] If the DC bus voltage of the inverter is lower than a preset threshold voltage, it indicates that undervoltage occurs;

[0030] If the phase loss detection circuit detects that there is a phase loss fault when the three-phase power supply is input and outputs a phase loss fault alarm signal, it means that a phase loss fault is detected;

[0031] The threshold voltage is -30% of the rated voltage value, and the rated voltage is the optimal voltage when the frequency converter works normally for a long time.

[0032] Among them, “controlling the power relay to disconnect after a delay period of time through the amplifier circuit” specifically includes:

[0033] The built-in timer is used to start timing, and after a delay of 10ms, the power relay is controlled to disconnect through the amplifier circuit;

[0034] During the delay of 10 ms, the two transistors of the amplifier circuit control the switch of the power relay to be in a closed state, short-circuiting the PTC resistor, and the residual current of the compressor or fan flows through the switch of the power relay;

[0035] When the power is turned on again, the PTC resistor is connected to the main circuit;

[0036] When the electrolytic capacitor in the main circuit is fully charged, the switch of the power relay is closed to short-circuit the PTC resistor again.

[0037] Wherein, in the amplifying circuit, the two transistors and one or more resistors constitute a switching circuit;

[0038] Among them, the drain of the first transistor Q1 and the drain of the second transistor Q2 of the two transistors are connected to one end of the power relay; resistors are connected between the gate and source of the first transistor Q1 and the second transistor Q2, respectively, and the source of the second transistor Q2 is grounded, and the gate of the first transistor Q1 is connected to other resistors;

[0039] After the delay of 10 ms, the switch circuit enters the cut-off state to disconnect the switch of the power relay.

[0040] In a third aspect, a computer-readable storage medium is provided, wherein a plurality of program codes are stored in the storage medium, and the program codes are suitable for being loaded and run by a processor to execute the control method of the surge protection circuit described in any one of the above;

[0041] Alternatively, a control device comprises a processor and a memory, wherein the memory device is suitable for storing a plurality of program codes, and the program codes are suitable for being loaded and run by the processor to execute any of the control methods for surge protection circuits described above.

[0042] In a fourth aspect, an air conditioning device is provided, the air conditioning device comprising a control system of a surge protection circuit;

[0043] or,

[0044] The air conditioning equipment comprises: an air conditioning inverter and the control device as described above.

[0045] The invention of one or more of the above technical solutions has at least one or more of the following

[0046] Beneficial effects:

[0047] The present invention relates to the field of surge protection circuit control technology, and specifically provides a control method, system and air conditioning equipment for a surge protection circuit. When the DC bus voltage of the frequency converter is undervoltage and / or the phase loss detection circuit detects a phase loss fault, after stopping the operation of the compressor or fan and turning off the output of PWM pulse width modulation, the power relay is disconnected after a delay period of time to allow the residual current of the compressor or fan to pass through the relay. When the above method is adopted, the present invention can not only better realize the surge protection function, but also avoid the residual current of the air conditioner compressor or fan flowing through the PTC resistor to cause heating, resulting in the air conditioner being unable to power on normally, thereby ensuring the safe, reliable and normal operation of the air conditioner circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 A main flow chart of an embodiment of a method for controlling a surge protection circuit according to the present invention;

[0049] Figure 2 A structural block diagram of an embodiment of a control system of a surge protection circuit according to the present invention;

[0050] Figure 3 FIG. 1 is a schematic diagram of an embodiment of a control circuit of a surge protection circuit according to a solution of the present invention. DETAILED DESCRIPTION

[0051] To facilitate understanding of the invention, the present invention will be described more comprehensively and meticulously below in conjunction with the accompanying drawings and examples. However, those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0052] In the description of the present invention, "module" and "processor" may include hardware, software or a combination of the two. A module may include hardware circuits, various suitable sensors, communication ports, and memories, and may also include software parts, such as program codes, or a combination of software and hardware. The processor may be a central processing unit, a microprocessor, an image processor, a digital signal processor, or any other suitable processor. The processor has data and / or signal processing functions. The processor may be implemented in software, hardware, or a combination of the two. Non-temporary computer-readable storage media include any suitable medium that can store program codes, such as a magnetic disk, a hard disk, an optical disk, a flash memory, a read-only memory, a random access memory, and the like. The term "A and / or B" means all possible combinations of A and B, such as only A, only B, or A and B. The term "at least one A or B" or "at least one of A and B" has a similar meaning to "A and / or B", and may include only A, only B, or A and B. The singular terms "one" and "the" may also include plural forms.

[0053] DC bus voltage: The DC bus is the bus voltage that converts AC into DC after rectification in the frequency converter, and converts DC into AC in the inverter; the DC bus voltage is the bus voltage after rectification and filtering.

[0054] PWM pulse width modulation: Pulse width modulation is an analog control method that modulates the bias of the transistor base or MOS tube gate according to the change of the corresponding load to achieve the change of the transistor or MOS tube conduction time, thereby achieving the change of the output of the switching regulated power supply.

[0055] Phase loss fault: refers to the loss of one phase of the three-phase input power supply of the frequency converter module.

[0056] Combine the following Figure 1 The main flow chart of an embodiment of a method for controlling a surge protection circuit of the present invention is shown to describe the implementation of the present invention.

[0057] Step S110, determining that the DC bus voltage of the inverter is undervoltage and / or the phase loss detection circuit detects a phase loss fault;

[0058] In one embodiment, if the DC bus voltage of the inverter is lower than a preset threshold voltage, it indicates that undervoltage has occurred; or, if the phase loss detection circuit detects a phase loss fault when a three-phase power supply is input and outputs a phase loss fault alarm signal, it indicates that a phase loss fault has been detected; wherein the threshold voltage is -30% of the rated voltage value, and the rated voltage is the optimal voltage when the inverter works normally for a long time.

[0059] Furthermore, if a DC bus voltage detection circuit detects an undervoltage, or a phase loss detection circuit detects a phase loss signal, that is, an undervoltage occurs or a phase loss fault is found, it indicates that the power grid fluctuates or stops instantly.

[0060] In one example, when the grid voltage fluctuates and / or loses power momentarily, if the DC bus voltage detection circuit detects that the DC bus voltage is lower than a preset threshold voltage, it indicates that undervoltage has occurred; wherein the threshold voltage is -30% of the rated voltage value, and the rated voltage is the optimal voltage for the inverter to work normally for a long time; if the rated voltage value of the inverter is 220 volts, when the DC bus voltage value is detected to be 150 volts, which is lower than -30% of the threshold voltage value, it is determined that undervoltage has occurred.

[0061] Step S120, according to the determined undervoltage or phase failure, after stopping the operation of the compressor or fan and turning off the PWM pulse width modulation output, the power relay is disconnected after a delay period of time to allow the residual current of the compressor or fan to pass through the relay.

[0062] In one embodiment, once a grid fluctuation or instantaneous outage occurs, that is, an undervoltage or phase loss fault is detected, the microcontroller unit MCU can be used for control, such as controlling the compressor or fan and other operating structures to shut down and disconnect the pulse width modulation, and further, the power relay before the PTC of the surge protection circuit is connected to the main circuit needs to be disconnected. The disconnection method can be to use a built-in timer to time, delay 10ms, and then control the power relay to disconnect through the amplifier circuit.

[0063] The amplifying circuit comprises: two triodes and one or more resistors;

[0064] Among them, short circuit refers to a method of connecting electricity by a local short circuit that does not damage electronic components in the circuit but makes the electronic components temporarily unable to work;

[0065] A PTC resistor is a thermistor with a positive temperature coefficient whose resistance value increases as the temperature increases.

[0066] Delay for a period of time before disconnecting the power relay to allow the residual current of the compressor or fan to pass through the relay, including:

[0067] During the delay of 10 ms, the two transistors control the switch of the power relay to be in a closed state, short-circuiting the PTC resistor of the surge protection circuit, and the residual current of the compressor or fan flows through the switch of the power relay;

[0068] After the delay of 10 ms, the switch of the power relay controlled by the two transistors is in an off state;

[0069] When the power is turned on again, the PTC resistor is connected to the main circuit;

[0070] When the electrolytic capacitor in the main circuit is fully charged, the switch of the power relay is closed to short-circuit the PTC resistor again.

[0071] Specifically, after the microcontroller unit MCU stops the operation of the compressor or fan and turns off the output of the PWM pulse width modulation, during the delay of 10ms, the microcontroller unit MCU outputs a high level, the two transistors are turned on, and the driving current is output to the power relay through the two transistors, the switch of the power relay is controlled to be in a closed state, the PTC resistor of the surge protection circuit is short-circuited, and the residual current of the compressor or fan flows through the switch of the power relay; after the delay of 10ms, the microcontroller unit MCU outputs a low level, the two transistors are cut off, and the switch of the power relay is controlled to be in an open state; when the power is turned on again, the PTC resistor is connected to the main circuit; when the electrolytic capacitor in the main circuit is charged, the switch of the power relay is attracted, and the PTC resistor is short-circuited again. Among them, the electrolytic capacitor in the main circuit is used to filter and smooth the voltage waveform.

[0072] Next, combine Figure 2 This is a structural block diagram of an embodiment of a control system of a surge protection circuit according to the present invention, which illustrates the implementation of the present invention. The system at least includes:

[0073] The surge protection circuit specifically includes: a PTC resistor 210, one end of which is connected to the main circuit, and the other end is connected to the power supply voltage VCC, and the PTC resistor is connected in parallel with the switch of the power relay; the power relay 220, one end of which is connected to the amplifier circuit 230, and the other end is connected to the DC power supply, and the power relay is connected in parallel with the rectifier diode D1;

[0074] In one example, Figure 3 It is a schematic diagram of an embodiment of a control circuit of a surge protection circuit according to the solution of the present invention; a PTC1 resistor, one end of which is connected to a main circuit, and the other end is connected to a power supply voltage VCC, and the PTC1 resistor is connected in parallel with a switch of a power relay RY4; the power relay RY4, one end of which is connected to an amplifier circuit, and the other end is connected to a 12V DC power supply, and the power relay RY4 is connected in parallel with a rectifier diode D1.

[0075] In one embodiment, when the DC bus voltage of the inverter is undervoltage and / or the phase loss detection circuit detects a phase loss fault due to grid fluctuation or momentary power outage, the operation of the compressor or fan is stopped and the output of the PWM pulse width modulation is turned off, and then the power relay is controlled by the amplifier circuit to be disconnected after a delay period, so that the residual current of the compressor or fan passes through the relay.

[0076] In one embodiment, if the DC bus voltage of the inverter is lower than a preset threshold voltage, it indicates that undervoltage occurs; if the phase loss detection circuit detects a phase loss fault when a three-phase power supply is input and outputs a phase loss fault alarm signal, it indicates that a phase loss fault is detected; wherein the threshold voltage is -30% of the rated voltage value, and the rated voltage is the optimal voltage when the inverter works normally for a long time.

[0077] In one example, when the grid voltage fluctuates and / or loses power momentarily, if the DC bus voltage detection circuit detects that the DC bus voltage is lower than a preset threshold voltage, it indicates that undervoltage has occurred; wherein the threshold voltage is -30% of the rated voltage value, and the rated voltage is the optimal voltage for the inverter to work normally for a long time; if the rated voltage value of the inverter is 220 volts, when the DC bus voltage value is detected to be 150 volts, which is lower than -30% of the threshold voltage value, it is determined that undervoltage has occurred.

[0078] In one embodiment, in the amplifier circuit, the two transistors and one or more resistors constitute a switching circuit; wherein the drain of the first transistor Q1 and the drain of the second transistor Q2 of the two transistors are connected to one end of the power relay; resistors are respectively connected between the gate and source of the first transistor Q1 and the second transistor Q2, and the source of the second transistor Q2 is grounded, and the gate of the first transistor Q1 is connected to other resistors; after the delay of 10ms, the switching circuit enters a cut-off state to disconnect the switch of the power relay.

[0079] In one implementation, a built-in timer is used to start timing, and after a delay of 10 ms, the power relay is controlled to disconnect through an amplifier circuit.

[0080] The amplifying circuit comprises: two triodes and one or more resistors;

[0081] Among them, short circuit refers to a method of connecting electricity by a local short circuit that does not damage electronic components in the circuit but makes the electronic components temporarily unable to work;

[0082] A PTC resistor is a thermistor with a positive temperature coefficient whose resistance value increases as the temperature increases.

[0083] Delay for a period of time before disconnecting the power relay to allow the residual current of the compressor or fan to pass through the relay, including:

[0084] During the delay of 10 ms, the two transistors control the switch of the power relay to be in a closed state, short-circuiting the PTC resistor of the surge protection circuit, and the residual current of the compressor or fan flows through the switch of the power relay;

[0085] After the delay of 10 ms, the switch of the power relay controlled by the two transistors is in an off state;

[0086] When the power is turned on again, the PTC resistor is connected to the main circuit;

[0087] When the electrolytic capacitor in the main circuit is fully charged, the switch of the power relay is closed to short-circuit the PTC resistor again.

[0088] Specifically, after the microcontroller unit MCU stops the operation of the compressor or fan and turns off the output of the PWM pulse width modulation, during the delay of 10ms, the microcontroller unit MCU outputs a high level, the two transistors are turned on, and the two transistors output drive current to the power relay, controlling the switch of the power relay to be in a closed state, short-circuiting the PTC resistor of the surge protection circuit, and the residual current of the compressor or fan flows through the switch of the power relay; after the delay of 10ms, the microcontroller unit MCU outputs a low level, the two transistors are cut off, and the switch of the power relay is controlled to be in an open state; when the power is turned on again, the PTC resistor is connected to the main circuit; when the electrolytic capacitor in the main circuit is charged, the switch of the power relay is attracted, and the PTC resistor is short-circuited again. Among them, the electrolytic capacitor in the main circuit is used to filter and smooth the voltage waveform.

[0089] Further, in an embodiment of a computer-readable storage medium of the present invention, a plurality of program codes are stored in the storage medium, and the program codes are suitable for being loaded and run by a processor to execute any of the control methods for surge protection circuits described above; or, a control device, the control device includes a processor and a memory, and the storage device is suitable for storing a plurality of program codes, and the program codes are suitable for being loaded and run by the processor to execute any of the control methods for surge protection circuits described above.

[0090] Further, in an embodiment of an air-conditioning device of the present invention, the air-conditioning device includes the control system of the aforementioned surge protection circuit; or, the air-conditioning device includes: an air-conditioning inverter and the control device as described above.

[0091] An example of an application scenario of the technical solution of the present invention is described below to further illustrate the implementation of the present invention:

[0092] like Figure 3 As shown, the surge protection circuit of a certain air conditioner includes: a PTC1 resistor, one end of which is connected to the main circuit, and the other end is connected to the power supply voltage VCC, and the PTC1 resistor is connected in parallel with the switch of the power relay RY4; the power relay RY4, one end of which is connected to the amplifier circuit, and the other end is connected to the 12V DC power supply, and the power relay RY4 is connected in parallel with the rectifier diode D1. The amplifier circuit, such as a Darlington circuit, includes the two transistors and one or more resistors to form a switch circuit; wherein the drain of the first transistor Q1 and the drain of the second transistor Q2 of the two transistors are connected to one end of the power relay; resistors are connected between the gate and source of the first transistor Q1 and the second transistor Q2, respectively, and the source of the second transistor Q2 is grounded, and the gate of the first transistor Q1 is connected to other resistors.

[0093] If the rated voltage value of an air conditioner inverter is 220 volts, when the DC bus voltage value is detected to be 150 volts, which is lower than -30% of the threshold voltage value, it is determined that undervoltage occurs. Or the phase-loss detection circuit detects that there is a phase-loss fault when the three-phase power supply is input and outputs a phase-loss fault alarm signal, which indicates that a phase-loss fault is detected; at this time, after the microcontroller unit MCU stops the operation of the compressor or fan and turns off the output of the PWM pulse width modulation, during the delay of 10ms, the microcontroller unit MCU outputs a high level, the two transistors are turned on, and the two transistors output drive current to the power relay, controlling the switch of the power relay to be in a closed state, short-circuiting the PTC1 resistor of the surge protection circuit, and the residual current of the compressor or fan flows through the switch of the power relay; after the delay of 10ms, the microcontroller unit MCU outputs a low level, the two transistors are turned off, and the switch of the power relay is controlled to be in an open state; when the power is turned on again, the PTC1 resistor is connected to the main circuit; when the electrolytic capacitor in the main circuit is charged, the switch of the power relay is attracted, and the PTC1 resistor is short-circuited again.

[0094] It is understood by those skilled in the art that the present invention implements all or part of the processes in the method of the above embodiment, and can also be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a computer-readable storage medium, and when the computer program is executed by the processor, the steps of each of the above method embodiments can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device, medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory, random access memory, electric carrier signal, telecommunication signal and software distribution medium, etc. that can carry the computer program code.

[0095] Further, it should be understood that since the setting of each module is only for illustrating the functional units of the system of the present invention, the physical devices corresponding to these modules can be the processor itself, or a part of the software in the processor, a part of the hardware, or a part of the combination of software and hardware. Therefore, the number of each module in the figure is only schematic.

[0096] Those skilled in the art will appreciate that the modules in the system may be adaptively split or merged. Such splitting or merging of specific modules will not cause the technical solution to deviate from the principle of the present invention, and therefore, the technical solutions after splitting or merging will fall within the protection scope of the present invention.

[0097] So far, the technical solution of the present invention has been described in conjunction with an embodiment shown in the accompanying drawings, but it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A method for controlling a surge protection circuit, characterized in that: When the DC bus voltage of the inverter is undervoltage and / or the phase failure detection circuit detects a phase failure, after stopping the operation of the compressor or fan and turning off the PWM pulse width modulation output, the power relay is disconnected after a delay, so that the residual current of the compressor or fan passes through the power relay; "Delay for a period of time before disconnecting the power relay", specifically includes: The built-in timer is used to start timing, and after a delay of 10ms, the power relay is controlled to disconnect through the amplifier circuit; The amplifying circuit comprises: two triodes and one or more resistors; PTC resistor refers to a thermistor with a positive temperature coefficient whose resistance value increases as the temperature increases. One end of the PTC resistor is connected to the main circuit, and the PTC resistor is connected in parallel with the switch of the power relay; In the amplifying circuit, the two transistors and one or more resistors form a switching circuit; wherein the drain of the first transistor Q1 and the drain of the second transistor Q2 of the two transistors are connected to one end of the power relay; resistors are connected between the gate and source of the first transistor Q1 and the second transistor Q2, respectively, and the source of the second transistor Q2 is grounded, and the gate of the first transistor Q1 is connected to other resistors; After the delay of 10 ms, the switch circuit enters the cut-off state to disconnect the switch of the power relay.

2. The method according to claim 1, characterized in that in, Undervoltage means that the bus voltage of the DC bus after rectification and filtering in the inverter is lower than the rated voltage; Among them, the phase failure means that one phase of the three-phase input power supply of the frequency conversion module is missing; If the DC bus voltage of the inverter is lower than a preset threshold voltage, it indicates that undervoltage occurs; If the phase loss detection circuit detects that there is a phase loss fault when the three-phase power supply is input and outputs a phase loss fault alarm signal, it means that a phase loss fault is detected; The threshold voltage is -30% of the rated voltage value, and the rated voltage is the optimal voltage when the frequency converter works normally for a long time.

3. The method according to claim 1, It is characterized in that Among them, short circuit refers to a method of connecting electricity by a local short circuit that does not damage electronic components in the circuit but makes the electronic components temporarily unable to work; Delay for a period of time before disconnecting the power relay to allow the residual current of the compressor or fan to pass through the relay, including: During the delay of 10 ms, the two transistors control the switch of the power relay to be in a closed state, short-circuiting the PTC resistor of the surge protection circuit, and the residual current of the compressor or fan flows through the switch of the power relay; After the delay of 10 ms, the switch of the power relay controlled by the two transistors is in an off state; When the power is turned on again, the PTC resistor is connected to the main circuit; When the electrolytic capacitor in the main circuit is fully charged, the switch of the power relay is closed to short-circuit the PTC resistor again.

4. A control system for a surge protection circuit, characterized in that: The surge protection circuit specifically includes: A PTC resistor, one end of which can be connected to the main circuit, and the PTC resistor is connected in parallel with the switch of the power relay; The power relay has one end connected to the amplifier circuit, and the power relay is connected in parallel with the rectifier diode D1; When the DC bus voltage of the inverter is undervoltage and / or the phase failure detection circuit detects a phase failure, after stopping the operation of the compressor or fan and turning off the output of the PWM pulse width modulation, the power relay is controlled by the amplifier circuit to be disconnected after a delay period of time, so that the residual current of the compressor or fan passes through the power relay; "Controlling the power relay to disconnect after a delay period of time through the amplifier circuit" specifically includes: The built-in timer is used to start timing, and after a delay of 10ms, the power relay is controlled to disconnect through the amplifier circuit; The amplifying circuit comprises: two triodes and one or more resistors; PTC resistor refers to a thermistor with a positive temperature coefficient whose resistance value increases as the temperature increases. In the amplifying circuit, the two transistors and one or more resistors form a switching circuit; wherein the drain of the first transistor Q1 and the drain of the second transistor Q2 of the two transistors are connected to one end of the power relay; resistors are connected between the gate and source of the first transistor Q1 and the second transistor Q2, respectively, and the source of the second transistor Q2 is grounded, and the gate of the first transistor Q1 is connected to other resistors; After the delay of 10 ms, the switch circuit enters the cut-off state to disconnect the switch of the power relay.

5. The system according to claim 4, characterized in that in, Undervoltage means that the bus voltage of the DC bus after rectification and filtering in the inverter is lower than the rated voltage; Among them, the phase failure means that one phase of the three-phase input power supply of the frequency conversion module is missing; If the DC bus voltage of the inverter is lower than a preset threshold voltage, it indicates that undervoltage occurs; If the phase loss detection circuit detects that there is a phase loss fault when the three-phase power supply is input and outputs a phase loss fault alarm signal, it means that a phase loss fault is detected; The threshold voltage is -30% of the rated voltage value, and the rated voltage is the optimal voltage when the frequency converter works normally for a long time.

6. The system according to claim 4, characterized in that During the delay of 10 ms, the two transistors of the amplifier circuit control the switch of the power relay to be in a closed state, short-circuiting the PTC resistor, and the residual current of the compressor or fan flows through the switch of the power relay; When the electrolytic capacitor in the main circuit is fully charged, the switch of the power relay is closed to short-circuit the PTC resistor again.

7. A computer-readable storage medium, characterized in that: The storage medium stores a plurality of program codes, and the program codes are suitable for being loaded and run by a processor to execute the control method of the surge protection circuit according to any one of claims 1 to 3.

8. A control device, comprising a processor and a memory, wherein the memory is suitable for storing a plurality of program codes, characterized in that: The program code is suitable for being loaded and run by the processor to execute the control method of the surge protection circuit according to any one of claims 1 to 3.

9. An air conditioning device, characterized in that: The air conditioning device includes a control system of a surge protection circuit according to any one of claims 4 to 6; or, The air conditioning equipment comprises: an air conditioning inverter and a control device as claimed in claim 8.

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