A conversion circuit controller for converting air conditioning expansion valve from 12V to 24V drive.

By designing a conversion circuit controller that includes a 24V switching power supply and a step-down protection circuit, the problem of high power and high efficiency that existing DC-DC step-down circuits cannot achieve in a small size is solved. This enables reliable driving of the air conditioning expansion valve and simplifies maintenance, thereby improving the safety and reliability of the air conditioning system.

CN116169636BActive Publication Date: 2026-06-02ZHEJIANG HENGSEN IND GROUP
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Patents(China)
Current Assignee / Owner
ZHEJIANG HENGSEN IND GROUP
Filing Date
2022-12-12
Publication Date
2026-06-02

AI Technical Summary

Technical Problem

Existing DC-DC step-down circuits are difficult to achieve high power, high efficiency, and high input voltage in a small size, and lack overvoltage protection, which can easily lead to load burnout, severe EMI interference, and the inability to drive the electronic expansion valve when it is stuck or cannot be opened, making maintenance difficult.

Method used

Design a conversion circuit controller that includes a 24V switching power supply, a current signal detection circuit, an overcurrent detection circuit, an optocoupler isolation circuit, and an N-MOS drive circuit. Through current signal detection and overcurrent protection, it achieves voltage conversion and signal isolation, provides a 24V power drive signal, and includes a buck protection circuit to prevent load overcurrent or short circuit.

Benefits of technology

It enables direct connection to the outdoor unit of the air conditioner for voltage reduction, reduces maintenance workload, improves safety and reliability, prevents load damage, simplifies the maintenance process, has a simple circuit structure, strong anti-interference ability, and provides flexible gate-source voltage control.

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Abstract

This invention discloses a conversion circuit controller for driving an air conditioner expansion valve from 12V to 24V, relating to the field of increasing power supply voltage to drive the expansion valve. It includes a 220V AC power input terminal, a 24V switching power supply, a power current signal detection circuit, a current signal amplification circuit, an overcurrent detection circuit, an overcurrent cutoff circuit, a 12V expansion valve drive signal optocoupler isolation input circuit, and an N-MOS drive circuit for the 24V power supply. It can be directly connected to the outdoor unit of an air conditioner. The controller enables voltage boosting and increases the driving force of the expansion valve, significantly reducing maintenance workload and facilitating repair. Simply fix the controller to the outdoor unit and connect it to the 220V power supply inside the unit. One end connects to the original expansion valve interface on the main board, and the other end connects to the expansion valve to achieve the operation of driving the expansion valve by increasing the power supply voltage.
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Description

Technical Field

[0001] This invention relates to the field of power supply voltage boosting for expansion valve technology, and more particularly to a conversion circuit controller for converting air conditioning expansion valve from 12V to 24V drive and its voltage reduction regulation method. Background Technology

[0002] Existing DC-DC buck converter circuits struggle to achieve high power, high efficiency, high input voltage, and low ripple within a small footprint. Conventional DC-DC buck converters rarely exceed 50V input voltage; applying higher voltages can damage the entire circuit. Similarly, increased current leads to severe heat generation, including inductor and power control IC overheating, increasing circuit ripple. Furthermore, conventional DC-DC circuits lack independent overvoltage protection; a circuit malfunction can cause high voltage to burn out the load. EMI (electromagnetic interference) is often neglected, leading to high-frequency interference signals spreading to other devices. Both safety and reliability are difficult to guarantee.

[0003] When existing electronic expansion valves fail to work, they are usually repaired manually, typically by disassembling and troubleshooting. However, in most cases, electronic expansion valves are stuck or cannot be opened. In such cases, the original control logic of the air conditioner cannot drive the electronic expansion valve to continue working, and external intervention is required, which is achieved by reducing the pressure. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a conversion circuit controller and its voltage reduction regulation method for realizing the conversion from 12V drive to 24V drive of air conditioner expansion valve, which addresses the shortcomings of the prior art. A controller can be directly connected to the outdoor unit of the air conditioner, and the voltage reduction operation is realized by the controller, which greatly reduces the workload of maintenance, lowers the cost, and facilitates maintenance. It is only necessary to fix the controller on the outdoor unit and connect it to the power supply inside the outdoor unit to realize the voltage reduction operation of the input power.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A conversion circuit controller for converting an air conditioner expansion valve from 12V to 24V drive includes a 220V AC power input terminal, a 24V switching power supply, a current signal detection circuit, a current signal amplification circuit, an overcurrent detection circuit, an overcurrent cut-off circuit, an optocoupler isolation circuit, and an N-MOS drive circuit.

[0007] The 24V switching power supply is connected to the 220V AC power input terminal to convert the voltage of the 220V AC power supply to the 24V power output.

[0008] The 24V switching power supply is connected to the overcurrent cutoff circuit through the current signal detection circuit, the current signal amplification circuit, and the overcurrent detection circuit, and is used to provide a protective 24V power input for the N-MOS drive circuit.

[0009] Optical isolation circuit, used for opto-isolation of input signals;

[0010] The MOS driver circuit is used to provide 4 or 8 expansion valve drive signals from a 24V power supply.

[0011] As a further preferred embodiment of the present invention, a conversion circuit controller for converting the 12V drive to 24V drive of an air conditioning expansion valve includes the following components: resistor R30, resistor R31, resistor R32, resistor R33, resistor R34, resistor R35, resistor R36, resistor R37, resistor R40, resistor R41, resistor R42, resistor R47, resistor R48, resistor R49; capacitor C30, capacitor C35, capacitor C40; operational amplifier IC30A, operational amplifier IC30D, operational amplifier IC30C; diode D40; transistor Q47; and N-MOS transistor Q30.

[0012] In this configuration, one end of resistor R30 is connected to the 24V voltage terminal and one end of resistor R31. The other end of one end of resistor R30 is connected to one end of resistor R33 and one end of resistor R49. The other end of resistor R31 is connected to one end of resistor R32 and the non-inverting input terminal of operational amplifier IC30A. The positive power supply terminal of operational amplifier IC30A is connected to one end of capacitor C30 and the 24V voltage terminal. The other end of capacitor C30 is grounded. The other end of resistor R32 is grounded. The other end of resistor R33 is connected to the inverting input terminal of operational amplifier IC30A and one end of resistor R34. The other end of resistor R34 is connected to the output terminal of operational amplifier IC30A. The negative power supply terminal of operational amplifier IC30A is grounded. The other end of resistor R35 is connected to one end of capacitor C35 and the non-inverting input terminal of operational amplifier IC30D. The other end of capacitor C35 is grounded and connected to one end of resistor R36 and one end of resistor R37. One end of resistor R36 is connected to the 24V voltage terminal, and the other end of resistor R37 is grounded. The output terminal of operational amplifier IC30D is connected to the positive terminal of diode D40. The negative terminal of diode D40 is connected to one end of capacitor C40, one end of resistor R40, and the inverting input terminal of operational amplifier IC30C. The non-inverting input terminal of operational amplifier IC30C is connected to one end of resistor R41 and one end of resistor R42. The other end of resistor R41 is connected to the 24V power supply terminal, and the other end of resistor R42 is grounded. The output terminal of operational amplifier IC30C is connected to one end of resistor R47. The other end of resistor R47 is connected to the base of transistor Q47. The emitter of transistor Q47 is grounded. The collector of transistor Q47 is connected to one end of resistor R48. The other end of resistor R48 is connected to the other end of resistor R49 and one end of N-MOS transistor Q30. The other end of N-MOS transistor Q30 is connected to the 24V power supply input for protection.

[0013] As a further preferred embodiment of the present invention, a conversion circuit controller for converting the 12V drive to 24V drive of an air conditioning expansion valve includes a resistor R11, a resistor R21, a diode D11, an N-MOS transistor Q11, and a protection 24V power input terminal. The protection 24V power input terminal is connected to one end of the resistor R11 and the negative terminal of the diode D11. The other end of the resistor R11 is connected to the collector of the optocoupler IC1. The emitter of the optocoupler IC1 is connected to one end of the resistor R21 and one end of the N-MOS transistor Q11. The other end of the resistor R21 is grounded. The other end of the N-MOS transistor Q11 is connected to the positive terminal of the diode D11 and grounded.

[0014] As a further preferred embodiment of the present invention, a conversion circuit controller for converting the air conditioner expansion valve from 12V drive to 24V drive, the optocoupler isolation circuit includes resistors R1, R2, R3, R4, R5, R6, R7, R8, and optocoupler IC1. Resistors R1, R2, R3, R4, R5, R6, R7, and R8 are respectively connected to the cathode of optocoupler IC1, and the anode of optocoupler IC1 is respectively connected to the 12V voltage terminal.

[0015] As a further preferred embodiment of the present invention, which implements a conversion circuit controller for switching an air conditioning expansion valve from 12V to 24V, the 24V switching power supply includes a step-down circuit module and a step-down protection circuit, wherein the step-down circuit module is connected to the step-down protection circuit.

[0016] The step-down circuit module is used to realize the voltage conversion of the power supply.

[0017] The step-down protection circuit is used to protect the output voltage value and the rate of voltage drop of the circuit, and realizes the control of the MOSFET gate voltage and timely protection of the load in case of overcurrent or short circuit.

[0018] As a further preferred embodiment of the present invention, a conversion circuit controller for converting the air conditioner expansion valve from 12V drive to 24V drive, the voltage reduction protection circuit includes a first-stage voltage reduction unit, a second-stage voltage reduction unit, a third-stage voltage reduction unit, and a voltage reduction speed regulation circuit.

[0019] The output terminal of the first-stage step-down unit is connected to the input terminal of the second-stage step-down unit, the input terminal of the step-down speed regulation circuit, and the output terminal of the step-down circuit module, respectively.

[0020] The output terminal of the second-stage step-down unit is connected to the input terminal of the third-stage step-down unit, the input terminal of the step-down speed regulation circuit, and the output terminal of the step-down circuit module, respectively.

[0021] The output terminal of the third-stage step-down unit is connected to the input terminal of the step-down speed regulation circuit and the output terminal of the step-down circuit module, respectively.

[0022] As a further preferred embodiment of the present invention, a conversion circuit controller for converting the 12V drive to 24V drive of an air conditioning expansion valve, when an overcurrent signal occurs, the first-stage buck protection unit in the buck protection circuit is activated, reducing the gate voltage of the protected power transistor to a set value to pre-protect the protected power transistor. At this time, the protected power transistor is in an edge state of being about to be fully turned on. Simultaneously, the first-stage buck gate voltage unit generates the delayed start-up voltage required by the second-stage buck gate voltage unit. If the overcurrent signal disappears within a fixed time delay, the protected power transistor returns to a fully turned-on state; if... If the overcurrent signal persists after a fixed delay, the second-stage gate voltage unit is activated to reduce the gate voltage of the protected power transistor to the gate turn-on voltage value corresponding to the rated load current, thus protecting the power transistor. Simultaneously, the second-stage buck unit generates the delayed start-up voltage required by the third-stage buck unit. If the overcurrent signal disappears within a fixed delay, the protected power transistor returns to a fully conducting state. If the overcurrent signal persists after a fixed delay, the third-stage buck unit is activated to slowly reduce the gate voltage of the protected power transistor to 0V, at which point the protected power transistor is in a turned-off state.

[0023] As a further preferred embodiment of the present invention, which implements a conversion circuit controller for the air conditioning expansion valve from 12V to 24V drive, the gate voltage reduction speed adjustment circuit consists of an RC delay circuit, used to slowly output the result of the step-down unit, with the purpose of adjusting the rise or fall rate of the MOSFET power transistor gate voltage; the formula for calculating the voltage rise or fall time is:

[0024]

[0025] Where R is the delay resistor, C is the delay capacitor, and U is the voltage used to charge the capacitor. c It is the voltage across the capacitor when it is charging.

[0026] As a further preferred embodiment of the present invention, which is a conversion circuit controller for converting the air conditioning expansion valve from 12V to 24V, the optocoupler IC1 is a 4-channel or 8-channel optocoupler.

[0027] A buck regulation and protection method based on a controller that implements a buck input power supply is as follows:

[0028] Step 1: Input 220V voltage through the power supply circuit;

[0029] Step 2: The voltage of the power supply is converted through a step-down circuit module to achieve a DC24V output.

[0030] Step 3: By using a step-down protection circuit to protect the output voltage value and the rate of voltage drop, voltage control and timely protection of the load in case of overcurrent or short circuit are achieved.

[0031] Compared with the prior art, the present invention, employing the above technical solution, has the following technical effects:

[0032] 1. This invention provides a conversion circuit controller for converting the 12V drive to 24V drive of an air conditioner expansion valve. It includes a 220V AC power input terminal, a 24V switching power supply, a current signal detection circuit, a current signal amplification circuit, an overcurrent detection circuit, an N-MOS drive circuit, and an optocoupler isolation circuit. It can be directly connected to the outdoor unit of an air conditioner. This controller enables voltage reduction, significantly reducing maintenance workload, lowering costs, and facilitating repairs. Simply fix the controller to the outdoor unit and connect it to the power supply inside the outdoor unit to achieve voltage reduction of the input power.

[0033] 2. The 24V switching power supply of this invention is connected to the input terminal of a 220V AC power supply to convert the voltage of the 220V AC power supply to a 24V power output. The 24V switching power supply is connected to an N-MOS drive circuit through a current signal detection circuit, a current signal amplification circuit, and an overcurrent detection circuit for overcurrent detection and disconnection after overcurrent, recovery after 2-3 seconds, and providing a 24V power input for protection of the N-MOS drive circuit. The N-MOS drive circuit provides 24V power and outputs 4 or 8 expansion valve drive signals. The optocoupler isolation circuit is used for signal isolation or optoelectronic isolation.

[0034] 3. The step-down protection circuit of this invention is used to protect the output voltage value and the rate of voltage drop of the circuit, thereby realizing the control of the MOSFET gate voltage and timely protection of the load in case of overcurrent or short circuit.

[0035] 4. The gate voltage reduction protection circuit of this invention controls the gate voltage of the MOSFET power transistor according to the design when the load is overcurrent or short-circuited, effectively preventing malfunctions and reducing the induced voltage generated when the protected power transistor is turned off, so that the protected power transistor can be protected with high reliability.

[0036] 5. The present invention has a simple circuit structure, small size, high precision, strong anti-interference ability, flexible gate-source voltage Vs setting, adjustable gate voltage reduction speed, and simple circuit debugging, thus realizing the control of MOSFET gate voltage. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the structural principle of a conversion circuit controller for realizing the conversion from 12V drive to 24V drive of an air conditioner expansion valve according to the present invention;

[0038] Figure 2 This is a circuit diagram of the current signal detection circuit, the current signal amplification circuit, and the overcurrent detection circuit of the present invention;

[0039] Figure 3This is a circuit diagram of the N-MOS driving circuit and optocoupler isolation circuit of the present invention;

[0040] Figure 4 This is a schematic diagram of the step-down protection circuit of the present invention. Detailed Implementation

[0041] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings:

[0042] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, they are provided so that the description of this disclosure will be more complete and fully convey the concept of the exemplary embodiments to those skilled in the art. The drawings are merely illustrative of this disclosure and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted.

[0043] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more exemplary embodiments. Numerous specific details are provided in the following description to give a full understanding of exemplary embodiments of this disclosure. However, those skilled in the art will recognize that the technical solutions of this disclosure can be practiced with one or more of the specific details omitted, or other methods, components, steps, etc., can be employed. In other instances, well-known structures, methods, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this disclosure.

[0044] A conversion circuit controller for converting air conditioning expansion valves from 12V to 24V drive, such as... Figure 1 As shown, it includes a 220V AC power input terminal, a 24V switching power supply, a current signal detection circuit, a current signal amplification circuit, an overcurrent detection circuit, an overcurrent cut-off circuit, an optocoupler isolation circuit, and an N-MOS drive circuit.

[0045] The 24V switching power supply is connected to the 220V AC power input terminal to convert the voltage of the 220V AC power supply to the 24V power output.

[0046] The 24V switching power supply is connected to the overcurrent cutoff circuit through the current signal detection circuit, the current signal amplification circuit, and the overcurrent detection circuit, and is used to provide a protective 24V power input for the N-MOS drive circuit.

[0047] Optical isolation circuit, used for opto-isolation of input signals;

[0048] The MOS driver circuit is used to provide 4 or 8 expansion valve drive signals from a 24V power supply.

[0049] This invention discloses a conversion circuit controller for converting the 12V drive to 24V drive of an air conditioner expansion valve. It includes a 220V AC power input terminal, a 24V switching power supply, a current signal detection circuit, a current signal amplification circuit, an overcurrent detection circuit, an N-MOS drive circuit, and an optocoupler isolation circuit. It can be directly connected to the outdoor unit of the air conditioner. This controller performs voltage reduction, significantly reducing maintenance workload, lowering costs, and facilitating repairs. Simply fix the controller to the outdoor unit and connect it to the power supply inside the outdoor unit to achieve voltage reduction of the input power.

[0050] like Figure 2 As shown, the current signal detection circuit, current signal amplification circuit, and overcurrent detection circuit include resistors R30, R31, R32, R33, R34, R35, R36, R37, R40, R41, R42, R47, R48, and R49; capacitors C30, C35, and C40; operational amplifiers IC30A, IC30D, and IC30C; diode D40; transistor Q47; and N-MOS transistor Q30.

[0051] In this configuration, one end of resistor R30 is connected to the 24V voltage terminal and one end of resistor R31. The other end of one end of resistor R30 is connected to one end of resistor R33 and one end of resistor R49. The other end of resistor R31 is connected to one end of resistor R32 and the non-inverting input terminal of operational amplifier IC30A. The positive power supply terminal of operational amplifier IC30A is connected to one end of capacitor C30 and the 24V voltage terminal. The other end of capacitor C30 is grounded. The other end of resistor R32 is grounded. The other end of resistor R33 is connected to the inverting input terminal of operational amplifier IC30A and one end of resistor R34. The other end of resistor R34 is connected to the output terminal of operational amplifier IC30A. The negative power supply terminal of operational amplifier IC30A is grounded. The other end of resistor R35 is connected to one end of capacitor C35 and the non-inverting input terminal of operational amplifier IC30D. The other end of capacitor C35 is grounded and connected to one end of resistor R36 and one end of resistor R37. One end of resistor R36 is connected to the 24V voltage terminal, and the other end of resistor R37 is grounded. The output terminal of operational amplifier IC30D is connected to the positive terminal of diode D40. The negative terminal of diode D40 is connected to one end of capacitor C40, one end of resistor R40, and the inverting input terminal of operational amplifier IC30C. The non-inverting input terminal of operational amplifier IC30C is connected to one end of resistor R41 and one end of resistor R42. The other end of resistor R41 is connected to the 24V power supply terminal, and the other end of resistor R42 is grounded. The output terminal of operational amplifier IC30C is connected to one end of resistor R47. The other end of resistor R47 is connected to the base of transistor Q47. The emitter of transistor Q47 is grounded. The collector of transistor Q47 is connected to one end of resistor R48. The other end of resistor R48 is connected to the other end of resistor R49 and one end of N-MOS transistor Q30. The other end of N-MOS transistor Q30 is connected to the 24V power supply input for protection.

[0052] like Figure 3 As shown, the N-MOS driving circuit includes resistors R11 and R21, diode D11, N-MOS transistor Q11, and a 24V protection power input terminal. The 24V protection power input terminal is connected to one end of resistor R11 and the cathode of diode D11. The other end of resistor R11 is connected to the collector of optocoupler IC1. The emitter of optocoupler IC1 is connected to one end of resistor R21 and one end of N-MOS transistor Q11. The other end of resistor R21 is grounded. The other end of N-MOS transistor Q11 is connected to the anode of diode D11 and grounded. The optocoupler isolation circuit includes resistors R1, R2, R3, R4, R5, R6, R7, and R8, and optocoupler IC1. Resistors R1, R2, R3, R4, R5, R6, R7, and R8 are connected to the cathode of optocoupler IC1, and the anode of optocoupler IC1 is connected to a 12V voltage terminal.

[0053] The 24V switching power supply includes a step-down circuit module and a step-down protection circuit, wherein the step-down circuit module is connected to the step-down protection circuit.

[0054] The step-down circuit module is used to realize the voltage conversion of the power supply.

[0055] The step-down protection circuit is used to protect the output voltage value and the rate of voltage drop of the circuit, and realizes the control of the MOSFET gate voltage and timely protection of the load in case of overcurrent or short circuit.

[0056] like Figure 4 As shown, the step-down protection circuit includes a first-stage step-down unit, a second-stage step-down unit, a third-stage step-down unit, and a step-down speed regulation circuit.

[0057] The output terminal of the first-stage step-down unit is connected to the input terminal of the second-stage step-down unit, the input terminal of the step-down speed regulation circuit, and the output terminal of the step-down circuit module, respectively.

[0058] The output terminal of the second-stage step-down unit is connected to the input terminal of the third-stage step-down unit, the input terminal of the step-down speed regulation circuit, and the output terminal of the step-down circuit module, respectively.

[0059] The output terminal of the third-stage step-down unit is connected to the input terminal of the step-down speed regulation circuit and the output terminal of the step-down circuit module, respectively.

[0060] When an overcurrent signal occurs, the first-stage buck unit in the buck protection circuit starts, reducing the gate voltage of the protected power transistor to a set value to pre-protect it. At this time, the protected power transistor is on the verge of fully conducting. Simultaneously, the first-stage buck unit generates the delayed start-up voltage required by the second-stage buck unit. If the overcurrent signal disappears within a fixed delay, the protected power transistor returns to a fully conducting state. If the overcurrent signal still exists after a fixed delay, the second-stage buck unit starts, reducing the gate voltage of the protected power transistor to the gate turn-on voltage value corresponding to the rated load current, thus protecting the power transistor. At the same time, the second-stage buck unit generates the delayed start-up voltage required by the third-stage buck unit. If the overcurrent signal disappears within a fixed delay, the protected power transistor returns to a fully conducting state. If the overcurrent signal still exists after a fixed delay, the third-stage buck unit starts, slowly reducing the gate voltage of the protected power transistor to 0V, at which point the protected power transistor is in a turned-off state.

[0061] The gate voltage reduction speed adjustment circuit consists of an RC delay circuit, used to slowly output the result from the buck unit, with the aim of regulating the rise or fall rate of the MOSFET power transistor gate voltage; the formula for calculating the voltage rise or fall time is:

[0062]

[0063] Where R is the delay resistor, C is the delay capacitor, and U is the voltage used to charge the capacitor. c It is the voltage across the capacitor when it is charging.

[0064] The optocoupler IC1 is a 4-channel or 8-channel optocoupler.

[0065] The buck protection circuit of this invention is used to protect the output voltage value and the rate of voltage drop of the circuit, and realizes the control of the MOSFET gate voltage and timely protection of the load in case of overcurrent or short circuit.

[0066] The gate voltage reduction protection circuit of this invention controls the gate voltage of the MOSFET power transistor according to the design when the load is overcurrent or short-circuited, effectively preventing malfunctions and reducing the induced voltage generated when the protected power transistor is turned off, thus providing highly reliable protection for the protected power transistor.

[0067] The present invention has a simple circuit structure, small size, high precision, strong anti-interference ability, flexible setting of gate-source voltage Vs, adjustable gate voltage reduction speed, and simple circuit debugging, thus realizing the control of MOSFET gate voltage.

[0068] A buck regulation and protection method based on a controller that implements a buck input power supply is as follows:

[0069] Step 1: Input 220V voltage through the power supply circuit;

[0070] Step 2: The voltage of the power supply is converted through a step-down circuit module to achieve a DC24V output.

[0071] Step 3: By using a step-down protection circuit to protect the output voltage value and the rate of voltage drop, voltage control and timely protection of the load in case of overcurrent or short circuit are achieved.

[0072] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A conversion circuit controller for converting air conditioner expansion valves from 12V to 24V drive, characterized in that: It includes a 220V AC power input terminal, a 24V switching power supply, a current signal detection circuit, a current signal amplification circuit, an overcurrent detection circuit, an overcurrent cut-off circuit, an optocoupler isolation circuit, and an N-MOS drive circuit. The 24V switching power supply is connected to the 220V AC power input terminal to convert the voltage of the 220V AC power supply to the 24V power output. The 24V switching power supply is connected to the overcurrent cutoff circuit through the current signal detection circuit, the current signal amplification circuit, and the overcurrent detection circuit, and is used to provide a protective 24V power input for the N-MOS drive circuit. Optical isolation circuit, used for opto-isolation of input signals; N-MOS driver circuit, used to provide 4 or 8 expansion valve drive signals for 24V power supply output; The 24V switching power supply includes a step-down circuit module and a step-down protection circuit. The step-down circuit module is connected to the step-down protection circuit. The step-down circuit module is used to realize the voltage conversion of the power supply. The step-down protection circuit is used to protect the output voltage value and the rate of voltage drop of the circuit, and realizes the control of the MOSFET gate voltage and timely protection of the load in case of overcurrent or short circuit. The step-down protection circuit includes a first-stage step-down unit, a second-stage step-down unit, a third-stage step-down unit, and a step-down speed regulation circuit. The output terminal of the first-stage step-down unit is connected to the input terminal of the second-stage step-down unit, the input terminal of the step-down speed regulation circuit, and the output terminal of the step-down circuit module, respectively. The output terminal of the second-stage step-down unit is connected to the input terminal of the third-stage step-down unit, the input terminal of the step-down speed regulation circuit, and the output terminal of the step-down circuit module, respectively. The output of the third-stage buck unit is connected to the input of the buck speed regulation circuit and the output of the buck circuit module, respectively. When an overcurrent signal occurs, the first-stage buck unit in the buck protection circuit starts, reducing the gate voltage of the protected power transistor to a set value to pre-protect the power transistor. At this time, the protected power transistor is in an edge state of being about to be fully turned on. Simultaneously, the first-stage buck unit generates the delayed start voltage required by the second-stage buck unit. If the overcurrent signal disappears within a fixed time delay, the protected power transistor returns to a fully turned-on state; if the overcurrent signal disappears within a fixed time delay, the protected power transistor returns to a fully turned-on state. If the overcurrent signal persists after the time delay, the second-stage buck unit is activated to reduce the gate voltage of the protected power transistor to the gate turn-on voltage value corresponding to the rated load current, thus protecting the power transistor. At the same time, the second-stage buck unit generates the delayed start-up voltage required by the third-stage buck unit. If the overcurrent signal disappears within a fixed time delay, the protected power transistor returns to a fully conducting state. If the overcurrent signal persists after a fixed time delay, the third-stage buck unit is activated to slowly reduce the gate voltage of the protected power transistor to 0V, at which point the protected power transistor is in a turned-off state.

2. The conversion circuit controller for converting an air conditioning expansion valve from 12V to 24V drive according to claim 1, characterized in that: The current signal detection circuit, current signal amplification circuit, and overcurrent detection circuit include resistors R30, R31, R32, R33, R34, R35, R36, R37, R40, R41, R42, R47, R48, and R49; capacitors C30, C35, and C40; operational amplifiers IC30A, IC30D, and IC30C; diode D40; transistor Q47; and N-MOS transistor Q30. In this configuration, one end of resistor R30 is connected to the 24V voltage terminal and one end of resistor R31. The other end of one end of resistor R30 is connected to one end of resistor R33 and one end of resistor R49. The other end of resistor R31 is connected to one end of resistor R32 and the non-inverting input terminal of operational amplifier IC30A. The positive power supply terminal of operational amplifier IC30A is connected to one end of capacitor C30 and the 24V voltage terminal. The other end of capacitor C30 is grounded. The other end of resistor R32 is grounded. The other end of resistor R33 is connected to the inverting input terminal of operational amplifier IC30A and one end of resistor R34. The other end of resistor R34 is connected to the output terminal of operational amplifier IC30A. The negative power supply terminal of operational amplifier IC30A is grounded. The other end of resistor R35 is connected to one end of capacitor C35 and the non-inverting input terminal of operational amplifier IC30D. The other end of capacitor C35 is grounded and connected to one end of resistor R36 and one end of resistor R37. One end of resistor R36 is connected to the 24V voltage terminal, and the other end of resistor R37 is grounded. The output terminal of operational amplifier IC30D is connected to the positive terminal of diode D40. The negative terminal of diode D40 is connected to one end of capacitor C40, one end of resistor R40, and the inverting input terminal of operational amplifier IC30C. The non-inverting input terminal of operational amplifier IC30C is connected to one end of resistor R41 and one end of resistor R42. The other end of resistor R41 is connected to the 24V power supply terminal, and the other end of resistor R42 is grounded. The output terminal of operational amplifier IC30C is connected to one end of resistor R47. The other end of resistor R47 is connected to the base of transistor Q47. The emitter of transistor Q47 is grounded. The collector of transistor Q47 is connected to one end of resistor R48. The other end of resistor R48 is connected to the other end of resistor R49 and one end of N-MOS transistor Q30. The other end of N-MOS transistor Q30 is connected to the 24V power supply input for protection.

3. The conversion circuit controller for converting air conditioning expansion valve from 12V to 24V drive according to claim 1, characterized in that: The N-MOS driving circuit includes resistor R11, resistor R21, diode D11, N-MOS transistor Q11, and a 24V protection power input terminal. The 24V protection power input terminal is connected to one end of resistor R11 and the cathode of diode D11. The other end of resistor R11 is connected to the collector of optocoupler IC1. The emitter of optocoupler IC1 is connected to one end of resistor R21 and one end of N-MOS transistor Q11. The other end of resistor R21 is grounded, and the other end of N-MOS transistor Q11 is connected to the anode of diode D11 and grounded.

4. A conversion circuit controller for converting an air conditioning expansion valve from 12V to 24V drive, as described in claim 1, is characterized in that: The optocoupler isolation circuit includes resistors R1, R2, R3, R4, R5, R6, R7, R8, and optocoupler IC1. Resistors R1, R2, R3, R4, R5, R6, R7, and R8 are respectively connected to the cathode of optocoupler IC1, and the anode of optocoupler IC1 is respectively connected to a 12V voltage terminal.

5. A conversion circuit controller for converting an air conditioning expansion valve from 12V to 24V drive according to claim 1, characterized in that: The buck speed control circuit consists of an RC delay circuit, used to slowly output the result from the buck unit, with the aim of regulating the rise or fall rate of the MOSFET power transistor gate voltage; the formula for calculating the voltage rise or fall time is: Where R is the delay resistor, C is the delay capacitor, U is the voltage used to charge the capacitor, and Uc is the voltage across the capacitor when it is charging.

6. A conversion circuit controller for converting an air conditioning expansion valve from 12V to 24V drive, as described in claim 4, is characterized in that: The optocoupler IC1 is a 4-channel or 8-channel optocoupler.

7. A method for step-down regulation and protection of a conversion circuit controller for an air conditioning expansion valve that converts 12V drive to 24V drive, based on any one of claims 1 to 6, characterized in that: Specifically, the steps are as follows: Step 1, input 220V voltage through the power supply circuit; Step 2: The voltage of the power supply is converted through a step-down circuit module to achieve a DC24V output. Step 3: By using a step-down protection circuit to protect the output voltage value and the rate of voltage drop, voltage control and timely protection of the load in case of overcurrent or short circuit are achieved.