Power control circuit and power control method of an induction heating paint removal machine

Abstract

The present invention discloses a power control circuit for an induction heating paint remover. The circuit includes a main circuit, a frequency control circuit, a power control circuit, a current sampling circuit, and a voltage sampling circuit. The frequency control circuit is used to control the inverter circuit, the power control circuit is used to control the chopper circuit, the current sampling circuit obtains the real-time current value of the alternating current output by the inverter circuit, and the voltage sampling circuit obtains the real-time voltage across the parallel capacitor. The output terminals of the current sampling circuit and the voltage sampling circuit are commonly connected to the frequency control circuit, and the output terminal of the voltage sampling circuit is also connected to the power control circuit. The present invention also provides a power control method for an induction heating paint remover. By applying the technical solution provided by the present invention, with the three loops of the frequency control loop, the power control loop, and the current control loop running in parallel, the output power of the control circuit changes with the specific working conditions during the heating process, ensuring the stability of the entire heating and paint removal process and obtaining a stable, reliable, and consistent heating and paint removal effect.

Description

Technical Field

[0001] The present invention belongs to the technical field of induction heating, and particularly relates to an induction heating paint remover. Background Art

[0002] Since the development of induction heating technology to date, it has been applied in more and more industrial occasions. Specifically in the occasion of removing paint from the surfaces of large steel structures such as ships and warships, the paint remover manufactured based on the principle of induction heating has also received extensive attention due to its advantages such as good controllability, high efficiency, and cleanliness.

[0003] In traditional induction heating paint removers, a power supply and an inductor are usually provided, and transformers are arranged in pairs on the power supply and the inductor to transmit electric energy from the power supply to the inductor in the form of first boosting voltage and reducing current and then reducing voltage and increasing current, in order to obtain a large current in the remote induction coil. The induction heating paint removers constructed in this way generally have defects such as excessive self-weight, serious heating, and clumsy movement. When applied to the paint removal operation on the surface of a large-area steel structure, it is very difficult to obtain a good user experience.

[0004] In response to the above problems, the inventor proposed "a composite resonance heating circuit" in 2019 (patent application number: 201921591283.6). In this patent application document, the inventor proposed that a remote resonance unit is formed by connecting a heating inductor and a parallel capacitor in parallel, and a proximal resonance unit is formed by connecting a series capacitor and the distributed inductance on the cable. By controlling the alternating current frequency f output by the power converter so that it is equal to the natural resonance frequency f0 of the remote resonance unit, that is, f = f0, the transformers in pairs or even in the prior art can be completely replaced, and a desired large current can be obtained on the heating inductor.

[0005] The circuit structure of the composite resonance heating is disclosed in the above patent application document. However, it should be noted that when applying the above circuit to the specific paint removal scenario on the surface of a ship or a warship, the operator should push the heating inductor to move slowly and gradually cover all target areas. Affected by factors such as the change in the moving speed of the heating inductor during the moving process, the change in the steel texture of the working area, and the change in the distance between the heating inductor and the target steel, the current flowing through the heating inductor will show a state of changing at any time. This will mean that the output power on the heating inductor will change accordingly, and the heating temperature of the entire induction heating paint removal device will also change at all times, and the heating effect will also change accordingly. How to control the output power of the entire heating circuit and obtain a stable, reliable, ideal, and consistent heating and paint removal effect during the entire induction heating paint removal process is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0006] To solve the above problems, the object of the present invention is to provide a power control circuit for an induction heating paint remover, which circuit monitors the current magnitude of the heating inductor in real time and adjusts the output power in real time according to the current magnitude, so as to ensure that the induction heating circuit achieves a consistent induction heating effect during the entire working process.

[0007] Another object of the present invention is to provide a power control method for an induction heating paint remover. This method has three parallel control loops, namely a frequency control loop, a power control loop, and a current control loop. The output power of the control circuit changes with the specific working conditions during the heating process, ensuring the stability of the entire paint removal process by heating and obtaining a stable, reliable, ideal, and consistent paint removal effect by heating.

[0008] To achieve the above object, the technical solution of the present invention is as follows:

[0009] A power control circuit for an induction heating paint remover, which circuit includes a main circuit, a frequency control circuit, a power control circuit, a current sampling circuit, and a voltage sampling circuit;

[0010] Among them, the main circuit includes a rectifier circuit, a chopper circuit, an inverter circuit, a series capacitor, a cable parasitic inductor, a parallel capacitor, and a heating inductor; the external industrial frequency mains power is connected to the rectifier circuit and becomes a direct current with a fixed voltage after being processed by the rectifier circuit. The output end of the rectifier circuit is connected to the chopper circuit. The chopper circuit changes the on-off state of its internal switching elements to convert the direct current with a fixed voltage into another direct current with a fixed voltage value or an adjustable voltage value after chopping. The output end of the chopper circuit is connected to the inverter circuit. The inverter circuit changes the on-off state of its upper and lower bridge arms to convert the direct current input by the chopper circuit back into an alternating current and outputs it between its two output ends; one output end of the inverter circuit is connected to one end of the series capacitor, the other end of the series capacitor is connected to one end of the cable parasitic inductor, the other end of the cable parasitic inductor is connected to one end of the parallel capacitor, the other end of the parallel capacitor is connected to the other output end of the inverter circuit, and both ends of the heating inductor are respectively connected to both ends of the parallel capacitor. The parallel capacitor and the heating inductor form a parallel resonance structure, and this resonance structure has a natural resonance frequency f0;

[0011] The frequency control circuit is used to control the inverter circuit and adjust the frequency f of the alternating current output by the inverter circuit; the power control circuit is used to control the chopper circuit and adjust the voltage amplitude U of the direct current output by the chopper circuit.

[0012] The current sampling circuit is arranged at the output end of the inverter circuit to sample the real-time current value of the alternating current output by the inverter circuit; the voltage sampling circuit is arranged at the parallel capacitor to sample the real-time voltage across the parallel capacitor; the output ends of the current sampling circuit and the voltage sampling circuit are jointly connected to the frequency control loop, and the output end of the frequency control loop is connected to the inverter circuit; the output end of the voltage sampling circuit is also connected to the power control loop, and the output end of the power control loop is connected to the chopper circuit.

[0013] Specifically, the frequency control loop includes a current zero-crossing detector, a voltage zero-crossing detector, a phase comparator, a VF voltage-frequency converter, and a PF pulse-frequency generator; the output end of the current sampling circuit is connected to the current zero-crossing detector, the output end of the voltage sampling circuit is connected to the voltage zero-crossing detector, the output ends of the current zero-crossing detector and the voltage zero-crossing detector are jointly connected to the phase comparator, the output end of the phase comparator is connected to the VF voltage-frequency converter, the output end of the VF voltage-frequency converter is connected to the PF pulse-frequency generator, and the output end of the PF pulse-frequency generator is connected to the inverter circuit.

[0014] Correspondingly, the power control loop includes a voltage setting circuit, a voltage rectifying amplifier, a voltage comparator, a PID controller, and a PWM driver;

[0015] Among them, the voltage setting circuit includes: a speed sensor, and a speed-voltage converter for converting the speed signal into a voltage signal according to a predetermined functional relationship; the speed sensor is arranged at the heating inductor to obtain the moving speed of the heating inductor, the output end of the speed sensor is connected to the speed-voltage converter, and the output end of the speed-voltage converter is connected to the power control loop.

[0016] The output end of the voltage sampling circuit is connected to the voltage rectifying amplifier, the output end of the voltage rectifying amplifier is connected to the voltage comparator, and the output end of the speed-voltage converter is also jointly connected to the voltage comparator; the output end of the voltage comparator is connected to the PID controller, the output end of the PID controller is connected to the PWM driver, and the output end of the PWM driver is connected to the chopper circuit.

[0017] The power control loop further includes a current rectifying amplifier, a current setter, and a current comparator; the output end of the current setter outputs a current value with a predetermined magnitude; the output end of the current sampling circuit is connected to the current rectifying amplifier, and the output ends of the current rectifying amplifier and the current setter are jointly connected to the current comparator, and the output end of the current comparator is connected to the PID controller.

[0018] Based on the above power control circuit of the induction heating paint stripper, the present invention also provides a power control method for the induction heating paint stripper, and the method includes the following steps:

[0019] S1: The voltage sampling circuit samples the real-time voltage across the parallel capacitor, denoted as U. C ; The current sampling circuit samples the real-time current of the alternating current output at the output end of the inverter circuit, denoted as I.

[0020] S2: Connect U C and I into the frequency control loop together. The frequency control loop adjusts the frequency f of the alternating current output by the inverter circuit according to the phase difference between U C and I, such that f = f0.

[0021] S3: The voltage given circuit acquires the moving speed of the heating inductor, denoted as v L , v L After being input into the speed-voltage converter, the speed-voltage converter converts it into a given voltage of corresponding magnitude according to the magnitude of v L according to the established functional relationship, denoted as U GD ; It should be noted that the conversion relationship between the moving speed v L of the heating inductor and the given voltage U GD belongs to the prior art. Those skilled in the art stipulate and implement the function between the two according to the requirements of the specific application scenario. This functional relationship is not the core of the protection of the present invention and is not within the scope of protection required by this application.

[0022] S4: Connect U C into the power control loop. The power control loop adjusts the voltage amplitude of the direct current output by the chopper circuit according to the difference between U C and U GD .

[0023] The power control method of the induction heating paint remover provided by the present invention constructs three closed loops for the power control of the induction heating paint remover.

[0024] First is the frequency control loop: This closed loop is mainly implemented by S2. The specific steps of S2 are:

[0025] S21: Connect U C to the voltage zero-crossing detector. The voltage zero-crossing detector outputs a voltage zero-crossing pulse at its output terminal at each zero-crossing moment of U C .

[0026] S22: Connect I to the current zero-crossing detector. The current zero-crossing detector outputs a current zero-crossing pulse at its output terminal at each zero-crossing moment of I.

[0027] S23: Connect the voltage zero-crossing pulse and the current zero-crossing pulse to the phase comparator, and the phase comparator compares to obtain the phase difference between the two.

[0028] S24: The VF voltage-frequency converter converts the phase difference output by the phase comparator and sends it to the PF pulse-frequency generator. The PF pulse-frequency generator generates two drive pulses to drive the on / off states of the upper and lower bridge arms of the inverter circuit respectively;

[0029] The voltage U across the parallel capacitor is sampled at both ends, C and the real-time current I of the alternating current output at the output end of the inverter circuit is obtained. Then, after processing U C and I, the phase difference between them is the voltage-current phase difference of the alternating current connected to the parallel structure. This phase difference is sent into the VF voltage-frequency converter and the PF pulse-frequency generator, and the generated drive pulses act on the inverter circuit, which will change the on / off states of the upper and lower bridge arms of the inverter circuit, and then change the frequency f of the alternating current output at the output end of the inverter circuit. By continuously repeating the above process, a complete frequency control loop can be constructed, and finally f = f0 can be achieved to realize the closed-loop control of the frequency f of the alternating current output by the inverter circuit.

[0030] Secondly, it is the power control loop. This closed loop is mainly implemented by S4. The specific steps of S4 are as follows:

[0031] S41: U C is connected to a voltage rectifying amplifier for rectifying and amplifying processes to obtain the corresponding signal U′ C ;

[0032] S42: U′ C and U GD are sent into a voltage comparator together to obtain the difference between them;

[0033] S42: After the difference between U′ C and U GD is calculated by a PID controller, the operation result is sent to a PWM driver. The PWM driver issues a drive waveform to drive the on / off states of the corresponding switching elements in the chopper circuit, changing the voltage magnitude output by the chopper circuit;

[0034] As mentioned above, when applying the main circuit described above to a specific induction heating paint removal scenario, the operator should slowly move the heating inductor to gradually cover all target areas. During this process, high-frequency large current flows into the heating inductor, and the heating inductor converts it into a high-frequency alternating magnetic field. This high-frequency alternating magnetic field is coupled to the steel surface of the target area to generate eddy current, and then Joule heat is generated in the steel of the target area. The larger the eddy current and the longer the action time, the greater the heat generated by the steel.

[0035] It can be seen that if the heating inductor outputs at a constant power, the faster the moving speed of the heating inductor, the less heat is generated in the steel in the working area per unit time, which may cause insufficient heating of the paint layer on the surface of the steel in the working area and cannot be completely stripped; correspondingly, if the heating inductor outputs at a constant power, the slower the moving speed of the heating inductor, the longer the heating inductor stays in the same working area, and the greater the heat generated in the steel in the working area, which may cause excessive heating of the paint layer on the surface of the steel in the working area and the paint layer is charred and pollutes the environment. Therefore, the moving speed of the heating inductor should be obtained, and the moving speed is associated with the output power of the heating inductor, so that the output power of the heating inductor changes with its moving speed, so as to obtain a stable, reliable, ideal and consistent heating and paint removal effect during the entire induction heating and paint removal process. In the control method provided by the present invention, the voltage given circuit cooperates with the speed sensor and the speed-voltage converter to collect the moving speed v of the heating inductor L , and the moving speed v L is converted into a corresponding given voltage U of a corresponding magnitude according to a predetermined functional relationship GD , and the given voltage U GD represents the ideal output power magnitude of the heating inductor at the current moving speed of the heating inductor. When f = f0 is obtained in the circuit, the parallel resonance structure presents a pure resistive property, and then the given voltage U GD will also represent the ideal output current magnitude of the heating inductor at the current moving speed of the heating inductor at the same time.

[0036] Analyzing the circuit structure of the power control circuit of the induction heating and paint removal machine described above, when the frequency f of the alternating current output by the inverter circuit satisfies f = f0, the parallel resonance structure formed by the parallel capacitor and the heating inductor will reach its resonance point. At this time, the entire parallel resonance structure presents a pure resistive property, and the currents on the parallel capacitor and the heating inductor change alternately, and the current flowing through the parallel capacitor is numerically approximately equal to the current flowing through the heating inductor. Therefore, a voltage sampling circuit is set up, and the real-time voltage across the parallel capacitor is sampled by the voltage sampling circuit and denoted as U C . When f = f0 is obtained in the circuit, the magnitude of U C will also represent the actual current magnitude on the heating inductor at the same time.

[0037] Compare U C with U GDA difference comparison is performed, and the comparison result is the difference between the actual current on the current heating inductor and the ideal output current of the current heating inductor. The difference is sent to the PID controller, and the drive waveform output by the PWM driver is further adjusted according to the calculation result of the PID controller to control the on-off status of the switching elements in the chopper circuit and change the voltage amplitude U of the DC power output by the chopper circuit. By continuously repeating the above process, a complete power control loop can be constructed to achieve closed-loop control of the output power of the entire circuit.

[0038] The last part is the current control loop: This closed loop is mainly implemented by S5. The specific steps of S5 are:

[0039] S51: The current setter outputs a given current value of a given size, recorded as I GD ;

[0040] S52: Connect I to the current rectifier amplifier for rectification and amplification to obtain the corresponding signal I′, and compare I′ with I GD They are sent to the current comparator together to get the difference between the two;

[0041] S53: I′ and I GD The difference is calculated by the PID controller and the result is sent to the PWM driver. Once I′≥I GD , the PWM driver controls the chopper circuit to stop working.

[0042] Define the given current value I output by the current setter GD The rated current value of the circuit output is the real-time current value I of the AC power collected by the current sampler at the output end of the inverter circuit. After processing, the real-time current value I is compared with the given current value I. GD The difference in the comparison directly indicates whether the real-time current in the inverter circuit meets the rated current of the entire circuit. If it exceeds this value, the PWM driver controls the chopper circuit to stop operation, protecting the various electronic components in the circuit. Repeating this cycle builds a complete power control loop and achieves closed-loop current control.

[0043] To sum up, compared with the existing technology, the power control circuit and power control method of the induction heating paint remover provided by the present invention support each other. During the operation of the induction heating paint remover, a circuit architecture of three parallel loops, namely, a frequency control loop, a power control loop and a current control loop, is constructed for the main loop. The control circuit maintains the parallel resonant structure always operating at its resonant point, and the output power on the heating inductor changes with its moving speed, ensuring the stability of the entire heating paint removal process. When applied to specific large-scale steel structure surface paint removal scenarios, a stable, reliable, ideal and consistent heating paint removal effect can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a schematic diagram of the circuit structure of the power control circuit of the induction heating paint remover implemented in the specific implementation manner. Specific implementation manner

[0045] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0046] To achieve the above object, the technical solution of the present invention is as follows:

[0047] Please refer to Figure 1 .

[0048] In this specific implementation manner, a power control circuit of an induction heating paint remover is provided. The circuit includes a main circuit, a frequency control circuit, a power control circuit, a current sampling circuit, and a voltage sampling circuit;

[0049] Among them, the main circuit includes a rectifier circuit, a chopper circuit, an inverter circuit, a matching transformer T, a series capacitor C1, a cable parasitic inductance L1, a parallel capacitor C2, and a heating inductance L2; the external industrial frequency mains is connected to the rectifier circuit, and after being processed by the rectifier circuit, it becomes a direct current with a fixed voltage. The output end of the rectifier circuit is connected to the chopper circuit. The chopper circuit changes the on-off state of its internal switching element, and the direct current with a fixed voltage is chopped to become another direct current with a fixed voltage value or an adjustable voltage value. The output end of the chopper circuit is connected to the inverter circuit. The inverter circuit changes the on-off state of its internal upper and lower bridge arms, and reconverts the direct current input by the chopper circuit into an alternating current, which is output between its two output ends; one output end of the inverter circuit is connected to one end of the series capacitor C1, the other end of the series capacitor is connected to one end of the cable parasitic inductance, the other end of the cable parasitic inductance is connected to one end of the parallel capacitor C2, the other end of the parallel capacitor C2 is connected to the other output end of the inverter circuit, and both ends of the heating inductance L2 are respectively connected to both ends of the parallel capacitor C2. The parallel capacitor C2 and the heating inductance L2 are combined to form a parallel resonance structure, and this resonance structure has an inherent resonance frequency f0;

[0050] The frequency control circuit is used to control the inverter circuit and adjust the frequency f of the alternating current output by the inverter circuit; the power control circuit is used to control the chopper circuit and adjust the voltage amplitude U of the direct current output by the chopper circuit.

[0051] The current sampling circuit is arranged at the output end of the inverter circuit to sample the real-time current value of the alternating current output by the inverter circuit; the voltage sampling circuit is arranged at the parallel capacitor C2 to sample the real-time voltage across the parallel capacitor C2; the output ends of the current sampling circuit and the voltage sampling circuit are commonly connected to the frequency control loop, and the output end of the frequency control loop is connected to the inverter circuit; the output end of the voltage sampling circuit is also connected to the power control loop, and the output end of the power control loop is connected to the chopper circuit.

[0052] Specifically, the frequency control loop includes a current zero-crossing detector, a voltage zero-crossing detector, a phase comparator, a VF voltage-frequency converter, and a PF pulse-frequency generator; the output end of the current sampling circuit is connected to the current zero-crossing detector, the output end of the voltage sampling circuit is connected to the voltage zero-crossing detector, the output ends of the current zero-crossing detector and the voltage zero-crossing detector are jointly connected to the phase comparator, the output end of the phase comparator is connected to the VF voltage-frequency converter, the output end of the VF voltage-frequency converter is connected to the PF pulse-frequency generator, and the output end of the PF pulse-frequency generator is connected to the inverter circuit.

[0053] Correspondingly, the power control loop includes a voltage setting circuit, a voltage rectifying amplifier, a voltage comparator, a PID controller, and a PWM driver;

[0054] Among them, the voltage setting circuit includes: a speed sensor, and a speed-voltage converter for converting the speed signal into a voltage signal according to a predetermined functional relationship; the speed sensor is arranged at the heating inductor L2 to obtain the moving speed of the heating inductor L2, the output end of the speed sensor is connected to the speed-voltage converter, and the output end of the speed-voltage converter is connected to the power control loop.

[0055] The output end of the voltage sampling circuit is connected to the voltage rectifying amplifier, the output end of the voltage rectifying amplifier is connected to the voltage comparator, and the output end of the speed-voltage converter is also jointly connected to the voltage comparator; the output end of the voltage comparator is connected to the PID controller, the output end of the PID controller is connected to the PWM driver, and the output end of the PWM driver is connected to the chopper circuit.

[0056] The power control loop further includes a current rectifying amplifier, a current setter, and a current comparator; the output end of the current setter outputs a current value with a predetermined magnitude; the output end of the current sampling circuit is connected to the current rectifying amplifier, and the output ends of the current rectifying amplifier and the current setter are jointly connected to the current comparator, and the output end of the current comparator is connected to the PID controller.

[0057] Based on the above power control circuit of the induction heating paint stripper, this specific embodiment further provides a power control method for the induction heating paint stripper, and the method includes the following steps:

[0058] S1: The voltage sampling circuit samples the real-time voltage across the parallel capacitor C2, denoted as U C ; The current sampling circuit samples the real-time current of the alternating current output at the output end of the inverter circuit, denoted as I;

[0059] S2: Connect U C and I into the frequency control loop together. The frequency control loop adjusts the frequency f of the alternating current output by the inverter circuit according to the phase difference between U C and I, so that f = f0;

[0060] S3: The voltage given circuit acquires the moving speed of the heating inductor L2, denoted as v L , v L is input into the speed-voltage converter. The speed-voltage converter converts it into a given voltage of corresponding magnitude according to the established functional relationship according to the magnitude of v L , denoted as U GD ;

[0061] S4: Connect U C into the power control loop. The power control loop adjusts the voltage amplitude of the direct current output by the chopper circuit according to the difference between U C and U GD .

[0062] Specifically, the specific steps of S2 are as follows:

[0063] S21: U C is connected to the voltage zero-crossing detector. The voltage zero-crossing detector outputs a voltage zero-crossing pulse at its output end at each zero-crossing moment of U C ;

[0064] S22: I is connected to the current zero-crossing detector. The current zero-crossing detector outputs a current zero-crossing pulse at its output end at each zero-crossing moment of I;

[0065] S23: The voltage zero-crossing pulse and the current zero-crossing pulse are connected to the phase comparator together. The phase comparator compares and obtains the phase difference between the two;

[0066] S24: The VF voltage-frequency converter converts the phase difference output by the phase comparator and sends it to the PF pulse-frequency generator. The PF pulse-frequency generator generates two drive pulses to drive the on and off of the upper and lower bridge arms of the inverter circuit respectively;

[0067] Specifically, the specific steps of S4 are as follows:

[0068] S41: U C is connected to the voltage rectifying amplifier for rectifying and amplifying processes to obtain the corresponding signal U' C ;

[0069] S42: Feed U' C and U GD into a voltage comparator together to obtain the difference between the two;

[0070] S42: The difference between U' C and U GD is calculated by a PID controller, and the operation result is sent to a PWM driver. The PWM driver issues a driving waveform to drive the on / off of the corresponding switching element in the chopper circuit, thereby changing the magnitude of the voltage output by the chopper circuit;

[0071] The power control method of the induction heating paint remover provided in this specific embodiment further includes S5. The specific steps of S5 are as follows:

[0072] S51: The current setter outputs a given current value with a predetermined magnitude, denoted as I GD ;

[0073] S52: Connect I to a current rectifier amplifier for rectification and amplification to obtain a corresponding signal I'. Feed I' and I GD into a current comparator together to obtain the difference between the two;

[0074] S53: After the difference between I' and I GD is calculated by a PID controller, the operation result is sent to a PWM driver. Once I≥I GD , the PWM driver controls the chopper circuit to stop working.

[0075] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A power control circuit for an induction heating paint remover, the power control circuit including a main circuit, the main circuit including a rectifier circuit, a chopper circuit, an inverter circuit, a series capacitor, a cable parasitic inductance, a parallel capacitor, and a heating inductor; an external industrial frequency mains power supply is connected to the rectifier circuit, the output end of the rectifier circuit is connected to the chopper circuit, the output end of the chopper circuit is connected to the inverter circuit, one output end of the inverter circuit is connected to one end of the series capacitor, the other end of the series capacitor is connected to one end of the cable parasitic inductance, the other end of the cable parasitic inductance is connected to one end of the parallel capacitor, the other end of the parallel capacitor is connected to the other output end of the inverter circuit, both ends of the heating inductor are respectively connected to both ends of the parallel capacitor, the parallel capacitor and the heating inductor are joined to form a parallel resonance structure, and this resonance structure has an inherent resonance frequency f0; It is characterized in that The power control circuit further includes: A frequency control loop for controlling the inverter circuit and adjusting the frequency f of the alternating current output by the inverter circuit; A power control loop for controlling the chopper circuit and adjusting the voltage amplitude U of the direct current output by the chopper circuit; A current sampling circuit and a voltage sampling circuit; The current sampling circuit is arranged at the output end of the inverter circuit to sample the real-time current value of the alternating current output by the inverter circuit; the voltage sampling circuit is arranged at the parallel capacitor to sample the real-time voltage of the parallel capacitor; The output ends of the current sampling circuit and the voltage sampling circuit are commonly connected to the frequency control loop, and the output end of the frequency control loop is connected to the inverter circuit; The output end of the voltage sampling circuit is further connected to the power control loop, and the output end of the power control loop is connected to the chopper circuit; The power control loop includes a voltage setting circuit; The voltage setting circuit includes a speed-voltage converter for converting a speed signal into a voltage signal according to a predetermined functional relationship; The control method of the power control circuit is: S1: The voltage sampling circuit samples the real-time voltage across the parallel capacitor, denoted as U. C ; The current sampling circuit samples the real-time current of the alternating current output at the output end of the inverter circuit, denoted as I. S2: Connect U C and I into the frequency control loop together. The frequency control loop adjusts the frequency f of the alternating current output by the inverter circuit according to the phase difference between U C and I, so that f = f0; S3: The voltage setting circuit acquires the moving speed of the heating inductor, denoted as v L , v L After inputting into the speed-voltage converter, the speed-voltage converter converts it into a corresponding given voltage of a corresponding magnitude, denoted as U, according to the magnitude of the v L value according to a predetermined functional relationship GD ; S4: Connect U C to the power control loop, and the power control loop adjusts the voltage amplitude of the direct current output by the chopper circuit according to the difference between U C and U GD .

2. The power control circuit of the induction heating paint removal machine according to claim 1, characterized in that The frequency control loop includes a current zero-crossing detector, a voltage zero-crossing detector, a phase comparator, a VF voltage-frequency converter, and a PF pulse-frequency generator; The output end of the current sampling circuit is connected to the current zero-crossing detector, the output end of the voltage sampling circuit is connected to the voltage zero-crossing detector, the output ends of the current zero-crossing detector and the voltage zero-crossing detector are jointly connected to the phase comparator, the output end of the phase comparator is connected to the VF voltage-frequency converter, the output end of the VF voltage-frequency converter is connected to the PF pulse-frequency generator, and the output end of the PF pulse-frequency generator is connected to the inverter circuit.

3. The power control circuit of the induction heating paint remover as claimed in claim 2, wherein, The voltage reference circuit includes: a speed sensor; the speed sensor is disposed at the heating inductor to obtain the moving speed of the heating inductor, the output end of the speed sensor is connected to the speed-voltage converter, and the output end of the speed-voltage converter is connected to the power control loop.

4. The power control circuit of the induction heating paint remover according to claim 3, characterized in that, The power control loop further includes a voltage rectifying amplifier, a voltage comparator, a PID controller, and a PWM driver; The output end of the voltage sampling circuit is connected to the voltage rectifying amplifier, the output end of the voltage rectifying amplifier is connected to the voltage comparator, and the output end of the speed-voltage converter is also connected to the voltage comparator; the output end of the voltage comparator is connected to the PID controller, the output end of the PID controller is connected to the PWM driver, and the output end of the PWM driver is connected to the chopper circuit.

5. The power control circuit of the induction heating paint removal machine according to claim 4, characterized in that The power control loop further includes a current rectifying amplifier, a current reference, and a current comparator; the output end of the current reference outputs a given current value with a predetermined magnitude; the output end of the current sampling circuit is connected to the current rectifying amplifier, and the output ends of the current rectifying amplifier and the current reference are connected to the current comparator together, and the output end of the current comparator is connected to the PID controller.

6. The power control circuit of the induction heating paint removal machine according to claim 5, characterized in that The control method of this circuit further includes S5, and specifically, S5 is: S51: The current setter outputs a given current value with a predetermined magnitude, denoted as I GD ; S52: Connect I to the current rectifier amplifier for rectification and amplification to obtain the corresponding signal I ` , and connect I ` and I GD to the current comparator together to compare and obtain the difference between the two; S53: I ` The difference from I GD is calculated by the PID controller, and the operation result is sent to the PWM driver. Once I ` ≥ I GD , the PWM driver controls the chopper circuit to stop working.

7. The power control circuit of the induction heating paint stripping machine according to claim 5, characterized in that Specifically, S2 is: S21: U C Connect to the zero-crossing voltage detector, and the zero-crossing voltage detector outputs a zero-crossing voltage pulse at its output terminal at each zero-crossing moment of U C ; S22: I is connected to the current zero-crossing detector, and the current zero-crossing detector outputs a current zero-crossing pulse at its output end at each zero-crossing moment of I; S23: The voltage zero-crossing pulse and the current zero-crossing pulse are connected to the phase comparator together, and the phase comparator compares to obtain the phase difference between the two; S24: The VF voltage-frequency converter converts the phase difference output by the phase comparator and sends it to the PF pulse-frequency generator, and the PF pulse-frequency generator generates two drive pulses to respectively drive the on and off of the upper and lower bridge arms of the inverter circuit.

8. The power control circuit of the induction heating paint removal machine according to claim 6, characterized in that, Specifically, S4 is: S41: U C It is connected to the voltage rectifying amplifier for rectifying and amplifying processes to obtain the corresponding signal U ' C ; S42: Send U ' C and U GD into the voltage comparator together to obtain the difference between the two by comparison; S42: U ' C The difference from U GD is calculated by the PID controller, and the operation result is sent to the PWM driver. The PWM driver issues a driving waveform to drive the on and off of the corresponding switching element in the chopper circuit, thereby changing the magnitude of the voltage output by the chopper circuit.

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