Switching power supply circuit, working method thereof, switching power supply and electric appliance

Abstract

The invention provides a switching power supply circuit and a working method thereof, a switching power supply and an electric appliance, the circuit comprises a power supply input end, a transformer, a main control circuit, a current detection circuit and an adjustable inductor, and the power supply input end is electrically connected with a primary winding of the transformer; the input end of the current detection circuit is used for obtaining load current of a secondary winding of the transformer, the output end of the current detection circuit is electrically connected with the main control circuit, the adjustable inductor is connected between the power input end and the primary winding in series, and the control end of the adjustable inductor is electrically connected with the main control circuit; the main control circuit is used for sending an inductance value adjusting signal to the control end of the adjustable inductor. The method comprises the following steps: acquiring a load current in a working state of a switching power supply circuit; when it is confirmed that the load is in the heavy load state according to the load current, the current inductance compensation amount of the adjustable inductor is obtained, and an inductance adjusting signal is sent to the control end of the adjustable inductor according to the current inductance compensation amount. The inductance value of the primary winding of the transformer can be adjusted, and stable operation of a unit is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of switching power supplies, and in particular, to a switching power supply circuit, a switching power supply using the switching power supply circuit, an electrical appliance using the switching power supply, and a working method of the switching power supply circuit. Background Art

[0002] At present, high-frequency transformers are mostly used in the switching power supply circuits of commercial air-conditioning controllers to convert DC bus voltage into multiple outputs to power various loads. However, high-frequency transformers are subject to technical constraints and may cause the inductance of the primary winding to decrease in harsh working environments. For example, factors such as temperature and humidity changes, aging, and excessive load current can cause the inductance to decrease. The decrease in inductance will lead to reduced efficiency, power output fluctuations, and long-term saturation leading to a shortened transformer life.

[0003] In an existing power supply regulation circuit, the number of turns on the primary side of the transformer can be adjusted to match the most suitable turns ratio and inductance value for the power supply, thereby expanding the input voltage range of the transformer and being compatible with multiple voltage levels.

[0004] However, this solution does not consider the impact of factors such as temperature and humidity changes, aging, and excessive load current on the transformer, and cannot solve the problem caused by the decrease in transformer inductance.

[0005] Therefore, a more optimized switching power supply circuit needs to be considered. Summary of the invention

[0006] The first object of the present invention is to provide a switching power supply circuit capable of adjusting the inductance of the primary winding of a transformer to ensure stable operation of the unit.

[0007] The second object of the present invention is to provide a switching power supply capable of adjusting the inductance of the primary winding of the transformer to ensure stable operation of the unit.

[0008] The third object of the present invention is to provide an electrical appliance capable of adjusting the inductance of the primary winding of the transformer to ensure stable operation of the unit.

[0009] A fourth object of the present invention is to provide a method for operating a switching power supply circuit that can adjust the inductance of the primary winding of the transformer to ensure stable operation of the unit.

[0010] In order to achieve the above-mentioned first purpose, the switching power supply circuit provided by the present invention includes a power input terminal and a transformer, and the power input terminal is electrically connected to the primary winding of the transformer; the switching power supply circuit also includes a main control circuit, a current detection circuit and an adjustable inductor, the input terminal of the current detection circuit is used to obtain the load current of the secondary winding of the transformer, the output terminal of the current detection circuit is electrically connected to the main control circuit, the adjustable inductor is connected in series between the power input terminal and the primary winding, and the control terminal of the adjustable inductor is electrically connected to the main control circuit; the main control circuit is used to send an inductance adjustment signal to the control terminal of the adjustable inductor.

[0011] It can be seen from the above scheme that the switching power supply circuit of the present invention connects an adjustable inductor in series before the primary winding of the transformer and sets a current detection circuit to obtain the load current of the secondary winding, so that the main control circuit is used to send an inductance adjustment signal to the control end of the adjustable inductor, change the core position of the adjustable inductor, and compensate for the inductance change of the transformer, thereby ensuring stable operation of the unit.

[0012] In a further solution, the current detection circuit includes a current transformer and a first amplifier circuit, the current transformer obtains the load current, the input end of the first amplifier circuit is electrically connected to the output end of the current transformer, and the output end of the first amplifier circuit is electrically connected to the main control circuit.

[0013] It can be seen that the current detection circuit can improve the accuracy of current detection by providing the first amplification circuit to amplify the load current obtained by the current transformer.

[0014] In a further solution, the first amplifying circuit includes a first amplifier, a first input end of the first amplifier is electrically connected to an output end of the current transformer, and an output end of the first amplifier is electrically connected to the main control circuit.

[0015] In a further embodiment, the first amplifier circuit also includes a second amplifier, the first input terminal of the second amplifier is electrically connected to the output terminal of the second amplifier, the second input terminal of the second amplifier is electrically connected to the first voltage bias circuit, and the output terminal of the second amplifier is electrically connected to the second input terminal of the first amplifier.

[0016] It can be seen that, by setting the first amplifier and the second amplifier, the first amplifier can amplify the current signal obtained by the current transformer through the first amplifier, and the second amplifier provides a bias voltage to the second amplifier.

[0017] In a further solution, the control end of the adjustable inductor is electrically connected to the main control circuit via a second amplifying circuit.

[0018] In a further solution, the second amplifier circuit includes a third amplifier, a first input terminal of the third amplifier is electrically connected to the main control circuit, a second input terminal of the third amplifier is electrically connected to the second bias voltage circuit, and an output terminal of the third amplifier is electrically connected to the control terminal of the adjustable inductor.

[0019] It can be seen that the main control circuit sends a control signal to the control end of the adjustable inductor through the second amplifying circuit, which can improve the control accuracy.

[0020] In a further solution, the switching power supply circuit also includes a temperature and humidity sensor, which is electrically connected to the main control circuit; the temperature and humidity sensor is used to obtain the temperature and humidity values ​​of the environment in which the transformer is located; the main control circuit adjusts the compensation inductance of the adjustable inductor according to the temperature and humidity values.

[0021] It can be seen that by setting the temperature and humidity sensors to obtain the temperature and humidity values ​​of the transformer environment, the compensation inductance of the adjustable inductor can be adjusted according to the temperature and humidity values, thereby reducing the impact of the working environment on the transformer.

[0022] In order to achieve the second objective of the present invention, the switching power supply provided by the present invention is provided with a switching power supply circuit, and the switching power supply circuit applies the above-mentioned switching power supply circuit.

[0023] In order to achieve the third purpose of the present invention, the electrical appliance provided by the present invention is provided with a switching power supply, and the switching power supply applies the above-mentioned switching power supply.

[0024] In order to achieve the fourth purpose of the present invention, the working method of the switching power supply circuit provided by the present invention includes: when the switching power supply circuit is in a working state, obtaining the load current; when confirming that it is in a heavy load state according to the load current, obtaining the current inductance compensation amount of the adjustable inductor, and sending an inductance adjustment signal to the control end of the adjustable inductor according to the current inductance compensation amount.

[0025] It can be seen from the above scheme that the working method of the switching power supply circuit of the present invention obtains the load current of the secondary winding, and when it is confirmed to be in a heavy load state, obtains the current inductance compensation amount of the adjustable inductance, compensates for the inductance change of the transformer, avoids excessive load power, and causes saturation of the high-frequency transformer core, thereby ensuring stable operation of the unit.

[0026] In a further solution, the step of obtaining the current inductance compensation amount of the adjustable inductor includes: obtaining the current temperature value and the current humidity value of the environment in which the transformer is located, and determining the current inductance compensation amount according to the current temperature value and the current humidity value.

[0027] It can be seen that by obtaining the temperature and humidity values ​​of the environment in which the transformer is located, the compensation inductance of the adjustable inductor can be adjusted according to the temperature and humidity values, thereby reducing the impact of the working environment on the transformer.

[0028] In a further solution, the step of obtaining the current inductance compensation amount of the adjustable inductor includes: obtaining the accumulated operating time of the transformer; and determining the current inductance compensation amount according to the accumulated operating time.

[0029] It can be seen that by obtaining the cumulative operating time of the transformer, the current inductance compensation amount can be further adjusted according to the aging degree of the transformer to improve the regulation accuracy.

[0030] In a further scheme, the step of obtaining the current inductance compensation amount of the adjustable inductor includes: obtaining the current temperature value and the current humidity value of the environment in which the transformer is located, and obtaining the cumulative operating time of the transformer; determining the current inductance compensation amount based on the cumulative operating time, the current temperature value and the current humidity value.

[0031] It can be seen that by determining the current inductance compensation amount according to the accumulated operating time, the current temperature value and the current humidity value, various factors affecting the inductance of the transformer can be integrated to improve the accuracy of the inductance compensation amount.

[0032] In a further scheme, the step of determining the current inductance compensation amount based on the accumulated operating time, the current temperature value and the current humidity value includes: determining a first inductance compensation amount based on the current temperature value and the current humidity value; determining a second inductance compensation amount based on the accumulated operating time; and taking the sum of the first inductance compensation amount and the second inductance compensation amount as the current inductance compensation amount.

[0033] It can be seen that the adjustment accuracy can be improved by superimposing the first inductance compensation amount determined by the current temperature value and the current humidity value and the second inductance compensation amount determined according to the accumulated running time to obtain the current inductance compensation amount. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 1 is a circuit schematic diagram of an embodiment of a switching power supply circuit of the present invention.

[0035] Figure 2 It is a circuit schematic diagram of the first amplifier circuit in the switching power supply circuit embodiment of the present invention.

[0036] Figure 3 It is a circuit schematic diagram of the second amplifier circuit in the switching power supply circuit embodiment of the present invention.

[0037] Figure 4 It is a flow chart of an embodiment of a working method of a switching power supply circuit of the present invention.

[0038] The present invention is further described below in conjunction with the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0039] Switching power supply circuit embodiment:

[0040] In this embodiment, see Figure 1The switching power supply circuit includes a power input terminal 1, a transformer T1, a main control circuit 2, a current detection circuit 3 and an adjustable inductor L1. The power input terminal 1 is electrically connected to the primary winding T11 of the transformer T1. The input terminal of the current detection circuit 3 is used to obtain the load current of the secondary winding T12 of the transformer T1. The output terminal of the current detection circuit 3 is electrically connected to the main control circuit 2. The adjustable inductor L1 is connected in series between the power input terminal 1 and the primary winding T11. The control terminal of the adjustable inductor L1 is electrically connected to the main control circuit 2. The main control circuit 2 is used to send an inductance adjustment signal to the control terminal of the adjustable inductor L1.

[0041] In this embodiment, see Figure 2 The current detection circuit 3 includes a current transformer L2 and a first amplifier circuit 31. The current transformer L2 obtains the load current. The input end of the first amplifier circuit 31 is electrically connected to the output end of the current transformer L2. The output end of the first amplifier circuit 31 is electrically connected to the main control circuit 2. The current detection circuit 3 amplifies the load current obtained by the current transformer L2 by setting the first amplifier circuit 31, thereby improving the accuracy of current detection.

[0042] In this embodiment, the first amplifier circuit 31 includes a first amplifier U1 and a second amplifier U2, the first input end of the first amplifier U1 is electrically connected to the output end of the current transformer L2, and the output end of the first amplifier U1 is electrically connected to the main control circuit 2. The first input end of the second amplifier U2 is electrically connected to the output end of the second amplifier U2, the second input end of the second amplifier U2 is electrically connected to the first voltage bias circuit 311, and the output end of the second amplifier U2 is electrically connected to the second input end of the first amplifier U1. The first amplifier circuit 31 is provided with the first amplifier U1 and the second amplifier U2, and the current signal obtained by the current transformer L2 can be amplified by the first amplifier U1, and the second amplifier U2 provides a bias voltage to the second amplifier U2. The amplification factor of the first amplifier U1 is adjusted by the resistor R1, the resistor R2, the resistor R3 and the resistor R4. The first voltage bias circuit 311 is provided with resistors R5 and R6, and the DC voltage bias of the current transformer signal is formed by adjusting the resistance values ​​of the resistors R5 and R6, which can be adjusted according to the output type of the current transformer.

[0043] In this embodiment, the control end of the adjustable inductor L1 is electrically connected to the main control circuit 2 through the second amplifier circuit 4. Figure 3The second amplifier circuit 4 includes a third amplifier U3, a first input end of the third amplifier U3 is electrically connected to the main control circuit 2, a second input end of the third amplifier U3 is electrically connected to the second bias voltage circuit 41, and an output end of the third amplifier U3 is electrically connected to the control end of the adjustable inductor L1. The resistor R7 and the resistor R8 in the second bias voltage circuit 41 are used to adjust the amplification factor of the third amplifier U3. The main control circuit 2 sends a control signal to the control end of the adjustable inductor L1 through the second amplifier circuit 4, which can improve the control accuracy.

[0044] In this embodiment, the switching power supply circuit further includes a temperature and humidity sensor 5, which is electrically connected to the main control circuit 2. The temperature and humidity sensor 5 is used to obtain the temperature and humidity values ​​of the environment in which the transformer T1 is located. The main control circuit 2 is used to adjust the compensation inductance of the adjustable inductor L1 according to the temperature and humidity values. By setting the temperature and humidity sensor 5 to obtain the temperature and humidity values ​​of the environment in which the transformer T1 is located, the compensation inductance of the adjustable inductor L1 can be adjusted according to the temperature and humidity values, thereby reducing the influence of the working environment on the transformer T1.

[0045] In addition, in the present embodiment, the switching power supply circuit is provided with a feedback circuit 6, a switching power supply chip 7 and an RCD absorption loop 8. The switching power supply chip 7 obtains the feedback signal detected by the secondary winding T12 through the feedback circuit 6, and controls the primary winding T11 loop, so that the output of the transformer T1 is more stable. At the same time, the RCD absorption loop 8 can suppress the resonant voltage spike on the primary winding T11 side to ensure stability. The feedback circuit 6, the switching power supply chip 7 and the RCD absorption loop 8 are well-known circuit modules in the flyback switching power supply, and will not be described in detail here. The transformer T1 can also be provided with multiple secondary windings T12 to provide multiple voltage outputs.

[0046] See also Figure 4 When the switching power supply circuit of this embodiment is working, step S1 is first performed to obtain the load current when the switching power supply circuit is in working state. In order to avoid excessive load power, long-term overload will cause permanent demagnetization of the magnetic core and cause irreversible damage. Therefore, it is necessary to detect the load current so as to adjust the inductance of the transformer T1. The main control circuit 2 can obtain the load current through the current detection circuit 3.

[0047] After the load current is obtained, step S2 is executed to determine whether the load current is confirmed to be in a heavy load state. When determining whether the load current is in a heavy load state, it is determined whether the load current is greater than a preset current value. If so, it is considered to be in a heavy load state, otherwise it is considered to be in a light load state. The preset current value can be pre-set according to experimental data.

[0048] If it is confirmed that the load current is in a heavy load state, step S3 is executed to obtain the current inductance compensation amount of the adjustable inductor L1. If it is confirmed that the load current is in a heavy load state, the inductance of the transformer T1 needs to be adjusted. Since the operating environment and operating time of the transformer T1 may cause the inductance of the transformer T1 to decrease, it is necessary to confirm the current inductance compensation amount of the adjustable inductor L1 to compensate the inductance of the transformer T1.

[0049] In an optional embodiment, the step of obtaining the current inductance compensation amount of the adjustable inductor L1 includes: obtaining the current temperature value and the current humidity value of the environment in which the transformer T1 is located, and determining the current inductance compensation amount according to the current temperature value and the current humidity value. By obtaining the temperature value and the humidity value of the environment in which the transformer T1 is located, the compensation inductance amount of the adjustable inductor L1 can be adjusted according to the temperature value and the humidity value, thereby reducing the impact of the working environment on the transformer T1. When determining the current inductance compensation amount according to the current temperature value and the current humidity value, the current inductance compensation amount can be obtained by looking up a table, and the corresponding inductance compensation amounts under different temperatures and humidities are recorded in a storage device according to the characteristics of the transformer T1. For example, the corresponding inductance compensation amounts under different temperature and humidity conditions are shown in the following table:

[0050]

[0051]

[0052] In an optional embodiment, the step of obtaining the current inductance compensation amount of the adjustable inductor L1 includes: obtaining the cumulative operating time of the transformer T1; determining the current inductance compensation amount according to the cumulative operating time. By obtaining the cumulative operating time of the transformer T1, the current inductance compensation amount can be further adjusted according to the aging degree of the transformer T1 to improve the adjustment accuracy. The inductance reduction value of the transformer T1 caused by the cumulative operating time is tested by an aging experiment, so as to determine the inductance compensation amount corresponding to different cumulative operating times, and store it in a storage device. When determining the inductance compensation amount according to the cumulative operating time, the inductance compensation amount corresponding to the cumulative operating time can be obtained by looking up a table.

[0053] In this embodiment, the step of obtaining the current inductance compensation amount of the adjustable inductor L1 includes: obtaining the current temperature value and the current humidity value of the environment in which the transformer T1 is located, and obtaining the cumulative operating time of the transformer T1; determining the current inductance compensation amount according to the cumulative operating time, the current temperature value and the current humidity value. By determining the current inductance compensation amount according to the cumulative operating time, the current temperature value and the current humidity value, the factors that cause the inductance of the transformer T1 to decrease can be comprehensively considered to improve the accuracy of the compensation. When determining the current inductance compensation amount according to the cumulative operating time, the current temperature value and the current humidity value, the current inductance compensation amount can be obtained by looking up a table. For example, the inductance compensation amounts corresponding to the cumulative operating time, the temperature value and the humidity value are shown in the following table:

[0054]

[0055] In an optional embodiment, the step of determining the current inductance compensation amount according to the accumulated operating time, the current temperature value and the current humidity value includes: determining a first inductance compensation amount according to the current temperature value and the current humidity value; determining a second inductance compensation amount according to the accumulated operating time; and taking the sum of the first inductance compensation amount and the second inductance compensation amount as the current inductance compensation amount. The current inductance compensation amount is obtained by superimposing the first inductance compensation amount determined by the current temperature value and the current humidity value and the second inductance compensation amount determined according to the accumulated operating time, which can improve the adjustment accuracy.

[0056] After obtaining the current inductance compensation amount, step S4 is executed to send an inductance adjustment signal to the control end of the adjustable inductor L1 according to the current inductance compensation amount. After confirming the current inductance compensation amount, the main control circuit 2 sends a corresponding control signal to the adjustable inductor L1, thereby adjusting the inductance of the adjustable inductor L1 to compensate for the inductance of the transformer T1.

[0057] When executing step S2, if the load current is not confirmed to be in a heavy load state, step S5 is executed to maintain the current inductance. In the light load state, there is no need to adjust the inductance of the adjustable inductor L1 to compensate the inductance of the transformer T1, so the current inductance can be maintained.

[0058] As can be seen from the above, the switching power supply circuit of the present invention connects the adjustable inductor L1 in series before the primary winding T11 of the transformer T1, and sets the current detection circuit 3 to obtain the load current of the secondary winding T12, so that the main control circuit 2 is used to send an inductance adjustment signal to the control end of the adjustable inductor L1, change the magnetic core position of the adjustable inductor L1, and compensate for the inductance change of the transformer T1, thereby ensuring the stable operation of the unit. At the same time, the working method of the switching power supply circuit of the present invention obtains the load current of the secondary winding T12, and when it is confirmed to be in a heavy load state, obtains the current inductance compensation amount of the adjustable inductor L1, compensates for the inductance change of the transformer T1, avoids excessive load power, and causes the saturation of the magnetic core of the high-frequency transformer T1, thereby ensuring the stable operation of the unit.

[0059] Switching power supply embodiment:

[0060] In this embodiment, the switching power supply is provided with a switching power supply circuit, and the switching power supply circuit applies the switching power supply circuit of the above embodiment.

[0061] Electrical appliance embodiment:

[0062] In this embodiment, the electrical appliance is provided with a switching power supply, and the switching power supply is the switching power supply of the above embodiment.

[0063] It should be noted that the above are only preferred embodiments of the present invention, but the design concept of the invention is not limited thereto, and any non-substantial modifications made to the present invention using this concept also fall within the protection scope of the present invention.

Claims

1. A switching power supply circuit, comprising a power input terminal and a transformer, wherein the power input terminal is electrically connected to a primary winding of the transformer; characterized in that: The switching power supply circuit also includes a main control circuit, a current detection circuit and an adjustable inductor, wherein the input end of the current detection circuit is used to obtain the load current of the secondary winding of the transformer, the output end of the current detection circuit is electrically connected to the main control circuit, the adjustable inductor is connected in series between the power input end and the primary winding, and the control end of the adjustable inductor is electrically connected to the main control circuit; The main control circuit is used to send an inductance adjustment signal to the control end of the adjustable inductor.

2. The switching power supply circuit according to claim 1, characterized in that: The current detection circuit includes a current transformer and a first amplifier circuit. The current transformer obtains the load current. The input end of the first amplifier circuit is electrically connected to the output end of the current transformer. The output end of the first amplifier circuit is electrically connected to the main control circuit.

3. The switching power supply circuit according to claim 2, characterized in that: The first amplifying circuit includes a first amplifier, a first input end of the first amplifier is electrically connected to an output end of the current transformer, and an output end of the first amplifier is electrically connected to the main control circuit.

4. The switching power supply circuit according to claim 3, characterized in that: The first amplifier circuit also includes a second amplifier, a first input terminal of the second amplifier is electrically connected to an output terminal of the second amplifier, a second input terminal of the second amplifier is electrically connected to a first voltage bias circuit, and an output terminal of the second amplifier is electrically connected to a second input terminal of the first amplifier.

5. The switching power supply circuit according to any one of claims 1 to 4, characterized in that: The control end of the adjustable inductor is electrically connected to the main control circuit through a second amplifier circuit.

6. The switching power supply circuit according to claim 5, characterized in that: The second amplifier circuit includes a third amplifier, a first input end of the third amplifier is electrically connected to the main control circuit, a second input end of the third amplifier is electrically connected to the second bias voltage circuit, and an output end of the third amplifier is electrically connected to the control end of the adjustable inductor.

7. The switching power supply circuit according to any one of claims 1 to 4, characterized in that: The switching power supply circuit also includes a temperature and humidity sensor, which is electrically connected to the main control circuit; The temperature and humidity sensor is used to obtain the temperature and humidity values ​​of the environment in which the transformer is located; The main control circuit adjusts the compensation inductance of the adjustable inductor according to the temperature value and the humidity value.

8. A switching power supply, provided with a switching power supply circuit, characterized in that: The switching power supply circuit applies the switching power supply circuit according to any one of claims 1 to 7.

9. An electrical appliance, provided with a switching power supply, characterized in that: The switching power supply applies the switching power supply described in claim 8.

10. A working method of a switching power supply circuit, the switching power supply circuit comprising a power input terminal and a transformer, the power input terminal being electrically connected to a primary winding of the transformer; characterized in that: The switching power supply circuit also includes a main control circuit, a current detection circuit and an adjustable inductor, wherein the input end of the current detection circuit is used to obtain the load current of the secondary winding of the transformer, the output end of the current detection circuit is electrically connected to the main control circuit, the adjustable inductor is connected in series between the power input end and the primary winding, and the control end of the adjustable inductor is electrically connected to the main control circuit; The main control circuit is used to send an inductance adjustment signal to the control end of the adjustable inductor; The method is applied to the main control circuit; The method comprises: When the switching power supply circuit is in a working state, obtaining the load current; When it is confirmed according to the load current that the load is in a heavy load state, obtaining a current inductance compensation amount of the adjustable inductor; An inductance adjustment signal is sent to a control terminal of the adjustable inductor according to the current inductance compensation amount.

11. The operating method of the switching power supply circuit according to claim 10, characterized in that: The switching power supply circuit also includes a temperature and humidity sensor, which is used to obtain the temperature and humidity values ​​of the environment in which the transformer is located; The step of obtaining the current inductance compensation amount of the adjustable inductor comprises: The current temperature value and the current humidity value of the environment in which the transformer is located are obtained, and the current inductance compensation amount is determined according to the current temperature value and the current humidity value.

12. The operating method of the switching power supply circuit according to claim 10, characterized in that: The step of obtaining the current inductance compensation amount of the adjustable inductor comprises: Obtaining the cumulative operating time of the transformer; The current inductance compensation amount is determined according to the accumulated operating time.

13. The operating method of the switching power supply circuit according to claim 10, characterized in that: The step of obtaining the current inductance compensation amount of the adjustable inductor comprises: Obtaining the current temperature value and the current humidity value of the environment in which the transformer is located, and obtaining the accumulated operating time of the transformer; The current inductance compensation amount is determined according to the accumulated operating time, the current temperature value, and the current humidity value.

14. The operating method of the switching power supply circuit according to claim 13, characterized in that: The step of determining the current inductance compensation amount according to the accumulated operating time, the current temperature value and the current humidity value comprises: determining a first inductance compensation amount according to the current temperature value and the current humidity value; determining a second inductance compensation amount according to the accumulated running time; The sum of the first inductance compensation amount and the second inductance compensation amount is used as the current inductance compensation amount.

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