阅读说明：本技术 一种感应加热除漆机的功率控制电路及其功率控制方法 (Power control circuit of induction heating paint remover and power control method thereof ) 是由 张海永 冯亚菲 雷剑利 李亮 赵伊 褚广哲 王戈 张寒露 于 2021-08-08 设计创作，主要内容包括：本发明公开了一种感应加热除漆机的功率控制电路,该电路包括有主回路、频率控制回路、功率控制回路、电流采样电路以及电压采样电路；频率控制回路用于控制逆变电路,功率控制回路用于控制斩波电路,电流采样电路获取逆变电路输出交流电的实时电流值；电压采样电路获取并联电容两端的实时电压；电流采样电路与电压采样电路的输出端共同接入频率控制回路；电压采样电路的输出端还接入功率控制回路。本发明还提供一种感应加热除漆机的功率控制方法。应用本发明提供的技术方案,以频率控制环、功率控制环以及电流控制环三环并行,控制电路的输出功率随加热过程的具体工况变化而变化,保证整个加热除漆过程稳定,获得稳定、可靠、一致的加热除漆效果。(The invention discloses a power control circuit of an induction heating paint remover, which comprises a main loop, a frequency control loop, a power control loop, a current sampling circuit and a voltage sampling circuit, wherein the main loop is connected with the frequency control loop; the frequency control loop is used for controlling the inverter circuit, the power control loop is used for controlling the chopper circuit, and the current sampling circuit acquires the real-time current value of the alternating current output by the inverter circuit; the voltage sampling circuit acquires real-time voltages at two ends of the parallel capacitor; the output ends of the current sampling circuit and the voltage sampling circuit are jointly connected to a frequency control loop; the output end of the voltage sampling circuit is also connected to a power control loop. The invention also provides a power control method of the induction heating paint remover. By applying the technical scheme provided by the invention, the frequency control loop, the power control loop and the current control loop are in parallel, the output power of the control circuit is changed along with the change of specific working conditions in the heating process, the stability of the whole heating and paint removing process is ensured, and the stable, reliable and consistent heating and paint removing effect is obtained.)

1. A power control circuit of an induction heating paint remover comprises a main loop, wherein the main loop comprises a rectifying circuit, a chopper circuit, an inverter circuit, a series capacitor, a cable parasitic inductor, a parallel capacitor and a heating inductor; the external power frequency commercial power is connected into the rectifying circuit, the output end of the rectifying circuit is connected into the chopper circuit, the output end of the chopper circuit is connected into the inverter circuit, one output end of the inverter circuit is connected with one end of the series capacitor, the other end of the series capacitor is connected with one end of the cable parasitic inductor, the other end of the cable parasitic inductor is connected with one end of the parallel capacitor, the other end of the parallel capacitor is connected with the other output end of the inverter circuit, two ends of the heating inductor are respectively connected with two ends of the parallel capacitor, the parallel capacitor and the heating inductor are connected to form a parallel resonance structure, and the resonance structure has inherent resonance frequency f₀；

It is characterized in that the circuit also comprises:

the frequency control loop is used for controlling the inverter circuit and adjusting the frequency f of the alternating current output by the inverter circuit;

the power control loop is used 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 and is used for sampling to obtain the real-time current value of the alternating current output by the inverter circuit; the voltage sampling circuit is arranged at the parallel capacitor and is used for sampling to obtain the real-time voltage of 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.

2. The power control circuit of an induction heating paint remover according to claim 1, wherein said 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 current zero-crossing detector and the output end of the voltage zero-crossing detector are connected to the phase comparator together, 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 an induction heating paint remover as claimed in claim 2, wherein said power control loop includes a voltage setting circuit;

the voltage setting circuit comprises: a speed sensor, and a speed-to-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.

4. The power control circuit of an induction heating paint remover as claimed in claim 3, wherein said power control loop further comprises a voltage rectifier 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 with the PID controller, the output end of the PID controller is connected with the PWM driver, and the output end of the PWM driver is connected with the chopper circuit.

5. The power control circuit of an induction heating paint remover as claimed in claim 4, wherein said power control loop further comprises a current rectifying amplifier, a current setter and a current comparator; the output end of the current setter outputs a given current value with a set size; the output end of the current sampling circuit is connected to the current rectifying amplifier, the current rectifying amplifier and the output end of the current setter are connected to the current comparator together, and the output end of the current comparator is connected to the PID controller.

6. A method for controlling the power of an induction heating paint remover, which is based on the power control circuit of the induction heating paint remover as claimed in claims 1-5; the method is characterized by comprising the following steps:

s1: the voltage sampling circuit samples to obtain the voltage across the parallel capacitorReal time voltage, denoted as U_C(ii) a The current sampling circuit samples to obtain real-time current of alternating current output at the output end of the inverter circuit, and the real-time current is marked as I;

s2: will U_CIs connected with I into the frequency control loop according to U_CThe phase difference between the I phase and the I phase adjusts the frequency f of the alternating current output by the inverter circuit, so that f is f₀；

S3: the voltage setting circuit acquires the moving speed of the heating inductor and records the moving speed as v_L，v_LAfter being input into the speed-voltage converter, the speed-voltage converter is according to v_LThe value is converted into a given voltage with corresponding value according to a predetermined functional relationship, and is marked as U_GD；

S4: will U_CAccessing the power control loop according to U_CAnd U_GDThe difference between the two is used for adjusting the voltage amplitude of the direct current output by the chopper circuit.

7. The power control method of the induction heating paint remover as claimed in claim 6, characterized in that the method further comprises S5, wherein S5 is specifically as follows:

s51: the current setter outputs a given current value with a given magnitude, denoted as I_GD；

S52: connecting I into the current rectifier amplifier for rectification and amplification to obtain corresponding signal I ', and connecting I' with I_GDSending the current signals into the current comparator together, and comparing to obtain a difference value of the current signals and the current signal;

s53: i' and I_GDAfter the difference value is calculated by the PID controller, the operation result is sent to the PWM driver, and once I' is greater than or equal to I_GDAnd the PWM driver controls the chopper circuit to stop working.

8. The power control method of the induction heating paint remover as claimed in claim 6, wherein said S2 is specifically:

S21：U_Cswitching in the voltage zero crossingA detector of zero crossing of voltage at U_CAt each zero-crossing point instant of time, outputting a voltage zero-crossing pulse at its output;

s22: i is connected into the current zero-crossing detector, and the current zero-crossing detector outputs a current zero-crossing pulse at the output end of the current zero-crossing detector at each zero-crossing moment of I;

s23: the voltage zero-crossing pulse and the current zero-crossing pulse are connected into the phase comparator together, and the phase comparator compares the voltage zero-crossing pulse and the current zero-crossing pulse to obtain the phase difference between the voltage zero-crossing pulse and the current zero-crossing pulse;

s24: the VF voltage frequency converter converts the phase difference output by the phase comparator and then sends the phase difference to the PF pulse frequency generator, and the PF pulse frequency generator generates two paths of driving pulses to respectively drive the upper bridge arm and the lower bridge arm of the inverter circuit to be switched on and off.

9. The power control method of the induction heating paint remover according to claim 7, wherein said S4 is specifically:

S41：U_Cconnecting the voltage rectification amplifier to carry out rectification processing and amplification processing to obtain a corresponding signal U'_C；

S42: is U'_CAnd U_GDSending the voltage signals into the voltage comparator together, and comparing to obtain a difference value of the voltage signals and the voltage signal;

S42：U′_Cand U_GDAfter the difference value between the two is calculated by the PID controller, the operation result is sent to the PWM driver, the PWM driver sends out a driving waveform to drive the on-off of a corresponding switch element in the chopper circuit, and the voltage output by the chopper circuit is changed.

Technical Field

The invention belongs to the technical field of induction heating, and particularly relates to an induction heating paint remover.

Background

Induction heating technology has been developed to date and has found application in an increasing number of industrial settings. Particularly, in the occasion of paint removing treatment of the surfaces of large steel structures such as ships and naval vessels, the paint remover manufactured based on the induction heating principle also draws attention with the advantages of good controllability, high efficiency, cleanness and the like.

The traditional induction heating paint remover is usually provided with a power supply and an inductor, the power supply and the inductor are provided with transformers in pairs, electric energy is transmitted from the power supply to the inductor in a mode of firstly boosting, reducing and then boosting, and large current is expected to be obtained in a far-end induction coil.

In view of the above problems, the inventor proposed a "composite resonant heating circuit" (patent application No. 201921591283.6) in 2019, in which the inventor proposed that a heating inductor and a parallel capacitor are connected in parallel to form a far-end resonant unit, a series capacitor is connected with a distributed inductor on a cable to form a near-end resonant unit, and the frequency of the alternating current output from the power converter is controlledf, making it resonant with the natural resonant frequency f of the remote resonant unit₀I.e. f ═ f₀The transformer can completely replace even paired transformers in the prior art, and the expected large current can be obtained on the heating inductor.

The above patent application document discloses a circuit structure of the composite resonance heating, but it should be noted that when the above circuit is applied to a specific ship and naval vessel surface paint removal scene, an operator should push the heating inductor to move slowly to gradually cover all target areas, and along with the influence of factors such as the movement speed change of the heating inductor in the moving process, the steel texture change of an operation area, the distance change of the heating inductor and the target steel, the current flowing through the heating inductor will be in a state of changing at any time, which means that the output power on the heating inductor will change accordingly, the heating temperature of the whole induction heating paint removal equipment will also change constantly, and the heating effect will also change accordingly. How to control the output power of the whole heating circuit and obtain stable, reliable, ideal and consistent heating and paint removing effects in the whole induction heating and paint removing process is a technical problem which needs to be solved urgently by technical personnel in the field.

Disclosure of Invention

In order to solve the above problems, an object of the present invention is to provide a power control circuit for an induction heating paint remover, which monitors the current of a heating inductor in real time, and adjusts the output power in real time according to the current, so as to ensure that the induction heating circuit obtains a consistent induction heating effect in the whole working process.

The invention also aims to provide a power control method of the induction heating paint remover, which is characterized in that a frequency control loop, a power control loop and a current control loop are connected in parallel, the output power of a control circuit is changed along with the change of specific working conditions of a heating process, the stability of the whole heating paint removing process is ensured, and a stable, reliable, ideal and consistent heating paint removing effect is obtained.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a power control circuit of an induction heating paint remover comprises a main loop, a frequency control loop, a power control loop, a current sampling circuit and a voltage sampling circuit;

the main loop comprises a rectifying circuit, a chopper circuit, an inverter circuit, a series capacitor, a cable parasitic inductor, a parallel capacitor and a heating inductor; the external power frequency commercial power is connected to a rectifying circuit, and becomes direct current with fixed voltage after being processed by the rectifying circuit, the output end of the rectifying circuit is connected to a chopper circuit, the chopper circuit changes the on-off condition of a switch element inside the chopper circuit, the direct current with the original fixed voltage is chopped into direct current with another fixed voltage value or adjustable voltage value, the output end of the chopper circuit is connected to an inverter circuit, and the inverter circuit converts the direct current input by the chopper circuit into alternating current again by changing the on-off condition of an upper bridge arm and a lower bridge arm inside the inverter circuit, and outputs the alternating current between the two output ends of the inverter circuit; one of the output ends of the inverter circuit is connected with one of the ends of the series capacitor, the other end of the series capacitor is connected with one of the ends of the parasitic inductance of the cable, the other end of the parasitic inductance of the cable is connected with one of the ends of the parallel capacitor, the other end of the parallel capacitor is connected with the other output end of the inverter circuit, two ends of the heating inductance are respectively connected with two ends of the parallel capacitor, the parallel capacitor and the heating inductance are jointed to form a parallel resonance structure, and the resonance structure has a natural resonance frequency f₀；

The frequency control loop is used for controlling the inverter circuit and adjusting the frequency f of the alternating current output by the inverter circuit; the power control loop is used for controlling the chopper circuit and adjusting the voltage amplitude U of the direct current output by the chopper circuit;

the current sampling circuit is arranged at the output end of the inverter circuit and samples to obtain the real-time current value of the alternating current output by the inverter circuit; the voltage sampling circuit is arranged at the parallel capacitor and samples to obtain real-time voltages at two ends of the parallel capacitor; the output ends of the current sampling circuit and the voltage sampling circuit are jointly connected to a frequency control loop, and the output end of the frequency control loop is connected to an inverter circuit; the output end of the voltage sampling circuit is also connected with a power control loop, and the output end of the power control loop is connected with a chopper circuit.

Specifically, the frequency control loop comprises 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 with a current zero-crossing detector, the output end of the voltage sampling circuit is connected with a voltage zero-crossing detector, the current zero-crossing detector and the output end of the voltage zero-crossing detector are connected with a phase comparator, the output end of the phase comparator is connected with a VF voltage frequency converter, the output end of the VF voltage frequency converter is connected with a PF pulse frequency generator, and the output end of the PF pulse frequency generator is connected with an inverter circuit.

Correspondingly, the power control loop comprises a voltage setting circuit, a voltage rectifying amplifier, a voltage comparator, a PID controller and a PWM driver;

wherein, voltage given circuit includes: a speed sensor and a speed-to-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.

The output end of the voltage sampling circuit is connected with a voltage rectifying amplifier, the output end of the voltage rectifying amplifier is connected with a voltage comparator, and the output end of the speed-voltage converter is also connected with the voltage comparator; the output end of the voltage comparator is connected with the PID controller, the output end of the PID controller is connected with the PWM driver, and the output end of the PWM driver is connected with the chopper circuit.

The power control loop also comprises a current rectifying amplifier, a current setter and a current comparator; the output end of the current setter outputs a current value with a set size; the output end of the current sampling circuit is connected with a current rectifying amplifier, the current rectifying amplifier and the output end of the current setter are connected into a current comparator together, and the output end of the current comparator is connected with a PID controller.

Based on the power control circuit of the induction heating paint remover, the invention also provides a power control method of the induction heating paint remover, which comprises the following steps:

s1: the voltage sampling circuit samples to obtain the real-time voltage at two ends of the parallel capacitor, which is recorded as U_C(ii) a The current sampling circuit samples to obtain real-time current of alternating current output at the output end of the inverter circuit, and the real-time current is marked as I;

s2: will U_CIs connected with I into a frequency control loop, and the frequency control loop is connected with I into a frequency control loop according to U_CThe phase difference between the I phase and the I phase adjusts the frequency f of the alternating current output by the inverter circuit, so that f is f₀；

S3: the voltage is given and circuit acquisition obtains the moving speed of the heating inductor, and is recorded as v_L，v_LAfter being input into the speed-voltage converter, the speed-voltage converter is based on v_LThe value is converted into a given voltage with corresponding value according to a predetermined functional relationship, and is marked as U_GD(ii) a It should be noted that the moving speed v of the heating inductor_LWith a given voltage U_GDThe conversion relationship between the two belongs to the prior art, and those skilled in the art are the requirements of specific application scenarios, and specify and implement the function between the two as required, and the functional relationship is not the protection core of the present invention and is not within the protection scope claimed in the present application.

S4: will U_CIs connected to a power control loop according to U_CAnd U_GDThe difference between the two is used for adjusting the voltage amplitude of the direct current output by the chopper circuit.

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

First, a frequency control loop: the closed loop is mainly realized by S2, and the specific steps of S2 are as follows:

S21：U_Cis connected to a voltage zero-crossing detector in U_CAt each zero-crossing point instant of time, outputting a voltage zero-crossing pulse at its output;

s22: the I is connected into a current zero-crossing detector, and the current zero-crossing detector outputs a current zero-crossing pulse at the output end of the current zero-crossing detector at each zero-crossing moment of the I;

s23: the voltage zero-crossing pulse and the current zero-crossing pulse are connected into a phase comparator together, and the phase comparator compares the voltage zero-crossing pulse and the current zero-crossing pulse to obtain the phase difference between the voltage zero-crossing pulse and the current zero-crossing pulse;

s24: the VF voltage frequency converter converts the phase difference output by the phase comparator and then sends the phase difference to the PF pulse frequency generator, and the PF pulse frequency generator generates two paths of driving pulses to respectively drive the upper bridge arm and the lower bridge arm of the inverter circuit to be switched on and switched off;

sampling at two ends of parallel capacitor to obtain voltage U at two ends_CAnd the real-time current I of the alternating current output at the output end of the inverter circuit is opposite to U_CAfter I is processed, the phase difference between the two is the voltage and current phase difference of the alternating current accessed to the parallel structure, the phase difference is sent to a VF voltage frequency converter and a PF pulse frequency generator, the generated driving pulse acts on an inverter circuit, the on-off conditions of an upper bridge arm and a lower bridge arm of the inverter circuit are changed, the frequency f of the alternating current output at the output end of the inverter circuit is changed, the process is continuously circulated, a complete frequency control loop can be constructed, and finally f is obtained₀And the closed-loop control of the alternating current frequency f output by the inverter circuit is realized.

Followed by a power control loop. The closed loop is mainly realized by S4, and the specific steps of S4 are as follows:

S41：U_Cconnected into a voltage rectification amplifier for rectification and amplification to obtain a corresponding signal U'_C；

S42: is U'_CAnd U_GDSending the voltage difference and the voltage difference into a voltage comparator together, and comparing to obtain a difference value of the two values;

S42：U′_Cand U_GDAfter the difference value between the two is calculated by the PID controller, the operation result is sent to the PWM driver, the PWM driver sends out a driving waveform to drive the on-off of a corresponding switch element in the chopper circuit, and the voltage output by the chopper circuit is changed;

when the main loop described above is applied to a specific induction heating paint removal scene, an operator should push the heating inductor to move slowly to gradually cover all target areas, in the process, a high-frequency large current flows into the heating inductor, the heating inductor converts the high-frequency large current into a high-frequency alternating magnetic field, the high-frequency alternating magnetic field is coupled to the surface of steel in the target areas to generate eddy current, and then joule heat is generated in the steel in the target areas, and the larger the eddy current is, the longer the action time is, and the larger the heat productivity of the steel is.

Therefore, if the heating inductor is kept to output with constant power, the faster the moving speed of the heating inductor is, the less the heat productivity of the steel in the working area in unit time is, and the paint layer on the surface of the steel in the working area is possibly heated insufficiently and cannot be completely peeled off; correspondingly, when the heating inductor is kept to output at a constant power, the slower the moving speed of the heating inductor is, the longer the retention time of the heating inductor in the same operation area is, the larger the calorific value of the steel in the operation area is, which may cause excessive heating of the paint layer on the surface of the steel in the operation area, and the environment polluted by the scorched paint layer. Therefore, the moving speed of the heating inductor is obtained, and is related to the output power of the heating inductor, so that the output power of the heating inductor is changed along with the change of the moving speed of the heating inductor, and the stable, reliable, ideal and consistent heating and paint removing effects can be obtained in the whole induction heating and paint removing process. In the control method provided by the invention, the voltage setting circuit acquires the moving speed v of the heating inductor by the cooperation of the speed sensor and the speed-voltage converter_LThe moving speed v is adjusted_LConverted into a given voltage U of corresponding magnitude according to a predetermined functional relationship_GDThe given voltage U_GDThat is, the ideal output power of the heating inductor is represented at the current moving speed of the heating inductor, and when f is obtained in the circuit, f is f₀When the parallel resonance structure presents pure resistance, the given voltage U is_GDThe ideal output current of the heating inductor at the current moving speed of the heating inductor can be represented at the same time.

As can be seen from the above-mentioned circuit structure of the power control circuit of the induction heating paint remover, when the frequency f of the ac power outputted from the inverter circuit satisfies f ═ f₀When the heating resistor is connected with the parallel capacitor, the parallel resonance structure formed by the connection of the parallel capacitor and the heating inductor reaches the resonance point, the whole parallel resonance structure is pure resistance, the current on the parallel capacitor and the heating inductor changes alternately, and the current flowing on the parallel capacitor and the heating resistor are numerically changedThe magnitude of the current flowing across the inductor is approximately equal. Therefore, a voltage sampling circuit is arranged, and the real-time voltage at two ends of the parallel capacitor is obtained by sampling through the voltage sampling circuit and is marked as U_CWhen f is obtained in the circuit₀While, U_CWill also characterize the actual current magnitude across the heating inductor.

Will U_CAnd U_GDAnd comparing the difference value, wherein the comparison result is the difference value between the actual current on the current heating inductor and the ideal output current of the current heating inductor, sending the difference value to the PID controller, further adjusting the driving waveform output by the PWM driver according to the operation result of the PID controller, controlling the on-off condition of a switching element in the chopper circuit, changing the voltage amplitude U of the direct current output by the chopper circuit, and continuously circulating the process to construct a complete power control loop so as to realize the closed-loop control of the output power of the whole circuit.

And finally, a current control loop: the closed loop is mainly realized by S5. The specific steps of S5 are:

s51: the current setter outputs a given current value of a given magnitude, denoted as I_GD；

S52: connecting I into a current rectifier amplifier for rectification and amplification to obtain a corresponding signal I ', and connecting I' with I_GDSending the signals into a current comparator together, and comparing to obtain the difference value of the two signals;

s53: i' and I_GDAfter the difference value is calculated by the PID controller, the operation result is sent to the PWM driver, and once I' is more than or equal to I_GDAnd the PWM driver controls the chopper circuit to stop working.

Defining a given current value I of a current setter output_GDThe current sampler outputs the real-time current value I of the collected alternating current at the output end of the inverter circuit for the rated current value output by the circuit, and the real-time current value I is processed and then is matched with the given current value I_GDAnd the compared difference value directly represents whether the real-time current in the inverter circuit is the rated current of the full circuit or not, and once the real-time current exceeds the rated current, the PWM driver controls the chopper circuit to stop working and protects each electronic component in the circuit. Repeating the above cycle process to construct complete powerAnd the control loop realizes current closed-loop control.

In summary, compared with the prior art, the power control circuit and the power control method of the induction heating paint remover provided by the invention support each other, a three-loop parallel circuit architecture of the frequency control loop, the power control loop and the current control loop is constructed for the main loop in the working process of the induction heating paint remover, the control circuit keeps the parallel resonance structure working at the resonance point all the time, the output power of the heating inductor changes along with the change of the moving speed, the stability of the whole heating paint removing process is ensured, and the stable, reliable, ideal and consistent heating paint removing effect can be obtained when the power control circuit is applied to the specific large steel structure surface paint removing occasions.

Drawings

FIG. 1 is a schematic circuit diagram of a power control circuit of an induction heating paint remover, as implemented in the detailed description.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

In order to achieve the purpose, the technical scheme of the invention is as follows:

please refer to fig. 1.

In this embodiment, a power control circuit of an induction heating paint remover is provided, which includes a main circuit, a frequency control circuit, a power control circuit, a current sampling circuit, and a voltage sampling circuit;

the main circuit comprises a rectifying circuit, a chopper circuit, an inverter circuit, a matching transformer T, a series capacitor C1, a cable parasitic inductor L1, a parallel capacitor C2 and a heating inductor L2; the external power frequency commercial power is connected into the rectification circuit and becomes direct current with fixed voltage after being processed by the rectification circuit, the output end of the rectification circuit is connected into the chopper circuit, and the chopper circuit changes the direct current with fixed voltage into another direct current after being chopped by changing the on-off condition of the switch element in the chopper circuitThe direct current with a fixed voltage value or an adjustable voltage value is connected with the output end of the chopper circuit, and the inverter circuit converts the direct current input by the chopper circuit into alternating current again by changing the on-off conditions of an upper bridge arm and a lower bridge arm inside the inverter circuit and outputs the alternating current from the two output ends of the inverter circuit; one output end of the inverter circuit is connected with one end of a series capacitor C1, the other end of the series capacitor is connected with one end of a cable parasitic inductor, the other end of the cable parasitic inductor is connected with one end of a parallel capacitor C2, the other end of the parallel capacitor C2 is connected with the other output end of the inverter circuit, two ends of a heating inductor L2 are respectively connected with two ends of a parallel capacitor C2, a parallel capacitor C2 and the heating inductor L2 are connected to form a parallel resonance structure, and the resonance structure has inherent resonance frequency f₀；

The frequency control loop is used for controlling the inverter circuit and adjusting the frequency f of the alternating current output by the inverter circuit; the power control loop is used for controlling the chopper circuit and adjusting the voltage amplitude U of the direct current output by the chopper circuit;

the current sampling circuit is arranged at the output end of the inverter circuit and samples to obtain 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 and is used for sampling to obtain real-time voltages at two ends of the parallel capacitor C2; the output ends of the current sampling circuit and the voltage sampling circuit are jointly connected to a frequency control loop, and the output end of the frequency control loop is connected to an inverter circuit; the output end of the voltage sampling circuit is also connected with a power control loop, and the output end of the power control loop is connected with a chopper circuit.

Specifically, the frequency control loop comprises 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 with a current zero-crossing detector, the output end of the voltage sampling circuit is connected with a voltage zero-crossing detector, the current zero-crossing detector and the output end of the voltage zero-crossing detector are connected with a phase comparator, the output end of the phase comparator is connected with a VF voltage frequency converter, the output end of the VF voltage frequency converter is connected with a PF pulse frequency generator, and the output end of the PF pulse frequency generator is connected with an inverter circuit.

Correspondingly, the power control loop comprises a voltage setting circuit, a voltage rectifying amplifier, a voltage comparator, a PID controller and a PWM driver;

wherein, voltage given circuit includes: a speed sensor and a speed-to-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 and is used for acquiring the moving speed of the heating inductor L2, the output end of the speed sensor is connected with the speed-voltage converter, and the output end of the speed-voltage converter is connected with the power control loop.

The output end of the voltage sampling circuit is connected with a voltage rectifying amplifier, the output end of the voltage rectifying amplifier is connected with a voltage comparator, and the output end of the speed-voltage converter is also connected with the voltage comparator; the output end of the voltage comparator is connected with the PID controller, the output end of the PID controller is connected with the PWM driver, and the output end of the PWM driver is connected with the chopper circuit.

The power control loop also comprises a current rectifying amplifier, a current setter and a current comparator; the output end of the current setter outputs a current value with a set size; the output end of the current sampling circuit is connected with a current rectifying amplifier, the current rectifying amplifier and the output end of the current setter are connected into a current comparator together, and the output end of the current comparator is connected with a PID controller.

Based on the power control circuit of the induction heating paint remover, the specific embodiment also provides a power control method of the induction heating paint remover, which comprises the following steps:

s1: the voltage sampling circuit samples to obtain real-time voltage at two ends of the parallel capacitor C2, which is recorded as U_C(ii) a The current sampling circuit samples to obtain real-time current of alternating current output at the output end of the inverter circuit, and the real-time current is marked as I;

s2: will U_CIs connected with I into a frequency control loop, and the frequency control loop is connected with I into a frequency control loop according to U_CThe phase difference between the I phase and the I phase adjusts the frequency f of the alternating current output by the inverter circuit, so that f is f₀；

S3: voltage setting circuitThe moving speed of the heating inductor L2 is acquired and recorded as v_L，v_LAfter being input into the speed-voltage converter, the speed-voltage converter is based on v_LThe value is converted into a given voltage with corresponding value according to a predetermined functional relationship, and is marked as U_GD；

S4: will U_CIs connected to a power control loop according to U_CAnd U_GDThe difference between the two is used for adjusting the voltage amplitude of the direct current output by the chopper circuit.

Specifically, the specific step of S2 is:

S21：U_Cis connected to a voltage zero-crossing detector in U_CAt each zero-crossing point instant of time, outputting a voltage zero-crossing pulse at its output;

s22: the I is connected into a current zero-crossing detector, and the current zero-crossing detector outputs a current zero-crossing pulse at the output end of the current zero-crossing detector at each zero-crossing moment of the I;

s23: the voltage zero-crossing pulse and the current zero-crossing pulse are connected into a phase comparator together, and the phase comparator compares the voltage zero-crossing pulse and the current zero-crossing pulse to obtain the phase difference between the voltage zero-crossing pulse and the current zero-crossing pulse;

s24: the VF voltage frequency converter converts the phase difference output by the phase comparator and then sends the phase difference to the PF pulse frequency generator, and the PF pulse frequency generator generates two paths of driving pulses to respectively drive the upper bridge arm and the lower bridge arm of the inverter circuit to be switched on and switched off;

specifically, the specific step of S4 is:

S41：U_Cconnected into a voltage rectification amplifier for rectification and amplification to obtain a corresponding signal U'_C；

S42: is U'_CAnd U_GDSending the voltage difference and the voltage difference into a voltage comparator together, and comparing to obtain a difference value of the two values;

S42：U′_Cand U_GDAfter the difference value between the two is calculated by the PID controller, the operation result is sent to the PWM driver, the PWM driver sends out a driving waveform to drive the on-off of a corresponding switch element in the chopper circuit, and the voltage output by the chopper circuit is changed;

the power control method of the induction heating paint remover provided in the present embodiment further includes S5, and the specific steps of S5 are:

s51: the current setter outputs a given current value of a given magnitude, denoted as I_GD；

S52: connecting I into a current rectifier amplifier for rectification and amplification to obtain a corresponding signal I ', and connecting I' with I_GDSending the signals into a current comparator together, and comparing to obtain the difference value of the two signals;

s53: i' and I_GDAfter the difference value is calculated by the PID controller, the operation result is sent to the PWM driver, and once I is more than or equal to I_GDAnd the PWM driver controls the chopper circuit to stop working.

The present invention is not limited to the above preferred embodiments, and any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.