CN210725393U - Heating control circuit and electromagnetic heating device - Google Patents

Abstract

The application discloses heating control circuit and electromagnetic heating device, this heating control circuit includes: a resonant heating module; a rectification filtering module; a power switch tube; a power switching tube driving circuit; the driving voltage transformation circuit enables the power switch tube to be switched on in a voltage reduction mode when the power switch tube is switched on; the voltage of the power switch tube which is reduced and switched on is a first driving voltage, and the voltage of the power switch tube which is switched on when the driving voltage transformation circuit is switched off is a second driving voltage; the power supply module is connected with the driving transformation circuit, is provided with a first voltage source and a second voltage source, and provides a first driving voltage and a second driving voltage for the switching-on of the power switching tube; the main control module is used for sending a driving signal to the power switching tube driving circuit so as to drive the power switching tube to be switched on and off; and sending a driving transformation signal to the driving transformation circuit, and selecting one of the first voltage source and the second voltage source to control the power switch tube to be switched on under the first or second driving voltage.

Description

Heating control circuit and electromagnetic heating device

Technical Field

The application relates to the technical field of electromagnetic heating, in particular to a heating control circuit and an electromagnetic heating device.

Background

With the development of electromagnetic heating technology, electromagnetic heating devices such as induction cookers and the like step into each household to facilitate cooking by the user. Taking an induction cooker as an example, most induction cookers in the market operate by using an electromagnetic resonance circuit of a single insulated gate Bipolar Transistor (IGBT, power switch tube), and generally adopt a parallel resonance mode.

In the working process of the induction cooker, transient current can be generated at the moment of switching on the IGBT, and under certain extreme conditions, the transient current can be large and exceeds the bearing capacity of the IGBT, so that the IGBT is damaged; when the IGBT is turned on, noise is generated, so that the IGBT generates heat seriously, and the heat dissipation of the IGBT (such as increasing a heat dissipation sheet, increasing the rotating speed of a fan and the like) needs to be enhanced so as to realize the temperature rise requirement of the IGBT; due to the existence of the filter capacitor, the IGBT is hard to turn on when being turned on, and the IGBT is easy to burn out.

In order to solve the above problems, a low-power continuous heating scheme can be adopted at present, and the scheme mainly realizes corresponding electromagnetic heating by changing the drive voltage of the IGBT. The typical scheme is that a zero-crossing detection module detects a zero-crossing signal and transmits the zero-crossing signal to a main control module, the main control module judges target power, and when the target power is smaller than preset power (namely, works in a low-power state), the main control module controls a driving voltage transformation circuit to work. In this case, each duty cycle includes three phases, namely a discharge phase, a heating phase and a stop phase. The main control module adjusts the voltage of the IGBT into a driving voltage by controlling the driving voltage transformation circuit in the discharging stage, and controls the IGBT to work under the driving of another driving voltage when the voltage of the collector electrode of the IGBT oscillates to the minimum, so that the IGBT is started in a voltage transformation manner, the risk of damage of the IGBT is reduced, and the turn-on noise is reduced.

Therefore, in the prior art, the voltage regulator tube is mainly used for reducing the driving voltage to another driving voltage so as to realize the voltage transformation driving of the IGBT, and thus the voltage regulator tube can work frequently. Considering that the voltage stabilizing tube has higher cost and can be more easily damaged when the voltage stabilizing tube works frequently, the service life of the induction cooker is reduced and the maintenance cost of the induction cooker is increased due to the adoption of the realization mode.

SUMMERY OF THE UTILITY MODEL

The application provides a heating control circuit and electromagnetic heating device to solve the technical problem that a voltage-stabilizing tube which is caused by adjusting driving voltage through the voltage-stabilizing tube is easy to damage after frequent working.

In order to solve the above problems, the technical solution provided by the present application is as follows:

in a first aspect, an embodiment of the present application provides a heating control circuit, which is used for heating control of an electromagnetic heating device. The heating control circuit includes: the device comprises a resonant heating module, a rectifying and filtering module, a power switch tube, a power supply module, a power switch tube driving circuit, a main control module and a driving transformation circuit. The rectification filtering module is used for carrying out rectification filtering processing on the alternating current power supply; the power switch tube is used for controlling the resonant heating module to perform resonant operation; a power switching tube driving circuit; the driving voltage transformation circuit enables the power switch tube to be switched on in a voltage reduction mode when the power switch tube is switched on; the voltage of the power switch tube which is reduced and switched on is a first driving voltage, the voltage of the power switch tube which is switched on when the driving transformation circuit is switched off is a second driving voltage, and the second driving voltage is greater than the first driving voltage; the power supply module is connected with the driving transformation circuit, is provided with a first voltage source and a second voltage source, and provides a first driving voltage and a second driving voltage for the switching-on of the power switching tube; the main control module is connected with the power switch tube driving circuit, the driving transformation circuit and the power supply module; the main control module is used for sending a driving signal to the power switching tube driving circuit so as to drive the power switching tube to be switched on and off; and sending a driving transformation signal to the driving transformation circuit, and selecting one of the first voltage source and the second voltage source to control the power switch tube to be switched on under the first driving voltage or the second driving voltage.

In one implementation, the power module further has a third voltage source for providing a third voltage to the main control module, where the third voltage is smaller than the first driving voltage.

In one implementation, the power module is connected to a three-terminal regulator at the first driving voltage, so that the first driving voltage obtains a third voltage through the three-terminal regulator, and the third voltage is used for supplying power to the main control module.

In one implementation, at a first drive voltage, the power switching tube operates in an amplification region; and under the second driving voltage, the power switch tube works in a saturation region.

In one implementation, the circuit further includes a zero-crossing detection module that detects a zero-crossing point of the ac power supply to obtain a zero-crossing signal; the zero-crossing signal is transmitted to the main control module, so that the main control module sends a driving transformation signal to the driving transformation circuit.

In one implementation, the power switch tube driving circuit is connected with a first voltage regulator tube in parallel between a gate electrode and an emitting electrode of the power switch tube.

In one implementation, the driving transformation circuit includes a first transistor and a second transistor; when the driving transformation signal is at a low level, the first triode is disconnected, the second triode is conducted, so that the second driving voltage is connected into the power switch tube driving circuit, and the first driving voltage is switched off.

In one implementation, the driving transformation circuit further includes a third transistor; when the driving transformation signal is at a high level, the first triode is conducted, the second triode is cut off, the third triode is conducted, so that the second driving voltage is cut off, and the first driving voltage is connected to the power switch tube driving circuit.

In one implementation, the driving transformation circuit includes a second triode, a third triode, a first capacitor, a second capacitor, a third capacitor, a first resistor, a second resistor, and a third resistor; the power supply module is also provided with a fourth voltage source. One end of the first capacitor is grounded after being connected with the second capacitor in parallel, the other end of the first capacitor is connected with the collector of the second triode respectively with the second voltage source, and the base of the second triode is connected with the first resistor in series and is connected with the fourth voltage source. One end of the third capacitor is grounded, the other end of the third capacitor is connected with the collector electrode of the third triode respectively with the first voltage source, the base electrode of the third triode is connected with the second resistor in series, and the emitting electrode of the third triode is connected with the third resistor in series and connected with the emitting electrode of the second triode.

In a second aspect, the present application provides an electromagnetic heating apparatus comprising the heating control circuit of the first aspect and any one of its various possible implementations.

Compared with the prior art, the voltage regulator tube is used for reducing the driving voltage to another driving voltage so as to realize the voltage transformation driving of the IGBT. In the actual working process of the heating control circuit, during high-power work, voltage transformation driving is not needed, and the IO port of the voltage transformation driving always outputs low level, while during low-power work, the IGBT needs to be driven by half voltage first and then driven by full voltage, and then the main control module adjusts the output of the IO port of the voltage transformation driving according to needs to convert the driving voltage. Therefore, under the condition that the voltage-regulator tube does not need to work frequently, the conversion between the first driving voltage and the second driving voltage is realized, and the technical problem that the voltage-regulator tube is easy to damage after working frequently due to the fact that the driving voltage is adjusted through the voltage-regulator tube in the prior art is solved.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the application and not to limit the application. In the drawings:

fig. 1 is a first schematic structural diagram of a heating control circuit according to an embodiment of the present disclosure;

fig. 2 is a schematic structural diagram of a heating control circuit according to an embodiment of the present disclosure;

fig. 3 is a first schematic voltage supply diagram after the power module provides each voltage source according to the embodiment of the present disclosure;

fig. 4 is a schematic structural diagram of a heating control circuit according to an embodiment of the present disclosure;

fig. 5 is a second schematic diagram of voltage supply after the power module provides each voltage source according to the embodiment of the present application.

Detailed Description

In order to more clearly explain the overall concept of the present application, the following detailed description is given by way of example in conjunction with the accompanying drawings.

The embodiment of the application provides a heating control circuit, which can be used for heating control of an electromagnetic heating device. The electromagnetic heating device may be an electromagnetic oven or an electromagnetic heating-based household appliance, such as an electromagnetic rice cooker, an electromagnetic pressure cooker, etc., and the type of the electromagnetic heating device is not limited herein, and may include, but is not limited to, the above-mentioned cases.

Fig. 1 is a schematic structural diagram of a heating control circuit according to an embodiment of the present disclosure. The heating control circuit may include a main control module 100, a zero-crossing detection module 200, a driving transformer circuit 300, a power switching tube driving circuit 400, a power switching tube 500, and a power supply module 301. In one implementation of the embodiments of the present application, the heating control circuit further includes other circuits 600, such as a resonant heating module, a rectifying and filtering module, and so on. The zero-crossing detection module 200 may transmit the detected zero-crossing signal to the main control module 100, so that the main control module 100 sends a driving transformation signal (which is also a kind of driving signal, and for simplicity and clarity, hereinafter, referred to as the driving transformation signal to distinguish the driving signal received by the power switching tube driving circuit) to the driving transformation circuit 300, so that the power switching tube is selectively turned on at the first driving voltage or the second driving voltage. The power module 301 has a first voltage source and a second voltage source, and provides a first driving voltage and a second driving voltage for the driving transformer circuit 300.

Fig. 2 is a schematic structural diagram of another heating control circuit provided in the embodiment of the present application. In the other circuit 600 shown in fig. 1, a resonant heating module 601 and a rectifying and filtering module 602 are shown. In the embodiment of the present application, the power switch 500 may be an Insulated Gate Bipolar Transistor (IGBT), and the structure of the rest of the power switch may refer to the related description in fig. 1, which is not described herein again.

Referring to fig. 2, the heating control circuit may further include: the circuit comprises a resonant heating module 601, a rectifying and filtering module 602, a zero-crossing detection module 200, a power switch tube 500, a power switch tube driving circuit 400, a main control module 100, a driving transformation circuit 300 and the power switch tube 500.

And the rectification and filtering module 602 is configured to perform rectification and filtering processing on the ac power supply.

A zero-crossing detection module 200, configured to detect a zero-crossing point of the ac power supply and output a zero-crossing signal; and is connected to the main control module 100, so that the main control module 100 sends a driving transformation signal to the driving transformation circuit 300.

And the power switch tube 500 is used for controlling the resonant heating module 601 to perform resonant operation.

The main control module 100 is connected to the zero-crossing detection module 200, the power switching tube driving circuit 400, and the driving transformer circuit 300. The zero crossing signal is transmitted to the main control module 100, so that the main control module 100 sends a driving transformation signal to the driving transformation circuit; specifically, the main control module 100 is configured to send a driving signal to the power switching tube driving circuit 400 to drive the power switching tube 500 to be turned on and off; and sending a driving transformation signal to the driving transformation circuit 300, and selecting one of the first voltage source and the second voltage source to control the power switch tube to be switched on under the first driving voltage or the second driving voltage. The driving signal may be a PPG signal, and has a high level and a low level which alternately occur periodically, so that the power switch tube 500 can be driven to be turned on and off.

Driving the voltage transformation circuit 300, and enabling the power switch tube to be switched on in a voltage reduction mode when the power switch tube is switched on; the voltage of the power switch tube which is reduced and switched on is a first driving voltage, the voltage of the power switch tube which is switched on when the driving transformation circuit is switched off is a second driving voltage, and the second driving voltage is greater than the first driving voltage; the power module is connected to the driving transformer circuit, and has a first voltage source and a second voltage source for providing a first driving voltage and a second driving voltage for the driving transformer circuit 300, respectively.

The voltage dropped by the power switch tube 500 is a first driving voltage, and the voltage dropped by the power switch tube 500 is a second driving voltage when the driving transformer circuit 300 is turned off. The second driving voltage is greater than the first driving voltage.

Compared with the prior art, the voltage regulator tube is used for reducing the driving voltage to another driving voltage so as to realize the voltage transformation driving of the IGBT. In the actual working process of the heating control circuit, during high-power work, transformation driving is not needed, and the IO port of the transformation circuit is driven to always input low level. Therefore, under the condition that the voltage-regulator tube does not need to work frequently, the conversion between the first driving voltage and the second driving voltage is realized, and the technical problem that the voltage-regulator tube is easy to damage after working frequently due to the fact that the driving voltage is adjusted through the voltage-regulator tube in the prior art is solved.

It is considered that during the actual operation of the heating control circuit, the power module 301 needs to provide a corresponding voltage to the main control module to support other operations of the main control module. Therefore, in an implementation manner of the embodiment of the present application, the power module 301 may further have a third voltage source for providing a third voltage to the main control module. Wherein the third voltage is less than the first driving voltage.

As shown in fig. 3, a schematic voltage supply diagram after providing each voltage source for a power module provided in the embodiment of the present application is shown. The power module 301 provides a first driving voltage output to the driving transformer circuit through a first voltage source, and the first driving voltage provides a third voltage output (generally 5V) to the main control module after passing through the three-terminal regulator, so as to supply power to the main control module. Of course, the third voltage output may also be used to power a display panel of the electromagnetic heating device, and is not limited herein. The power module 301 may further provide a second driving voltage output to the driving transformer circuit through a second voltage source, and the second driving voltage may also be used to supply power to other circuits, modules, and the like. Under the first driving voltage, the power switch tube works in an amplification area; and under the second driving voltage, the power switch tube works in a saturation region.

Therefore, the driving transformation circuit can control the switching of the driving voltage of the power switch tube through the driving circuit of the power switch tube, namely, the voltage of the power switch tube is switched between the first driving voltage and the second driving voltage.

In a preferred embodiment of the present application, the first voltage source may be +9V, the second voltage source may be +18V, the first driving voltage is +9V, the second driving voltage is +18V, the three-terminal regulator may be 78L05, and the third voltage is 5V. By adopting the implementation mode, the 5V voltage required by the electromagnetic heating device can be provided for the electromagnetic heating device through the power supply module, and the output 5V voltage is not influenced by the switching of the driving voltage. The voltage of 5V is used to supply power to the main control module 100 or other control ports such as a display panel.

In the embodiment of the present application, values of the first driving voltage and the second driving voltage are not limited. In one implementation of the embodiment of the present application, the first driving voltage and/or the second driving voltage may be adjusted by adjusting the number of winding turns of the transformer in the power supply module. Of course, the first driving voltage and/or the second driving voltage may be adjusted in other manners, and the adjustment manner is not limited herein.

Fig. 4 is a schematic structural diagram of a specific heating control circuit provided in an embodiment of the present application.

The driving transformer circuit 300 includes a second transistor Q102, a third transistor Q103, a first capacitor C300, a second capacitor C301, a third capacitor C304, a first resistor R102, a second resistor R104, and a third resistor R105. In the embodiment of the present application, the power module may further have a fourth voltage source, i.e., VCC shown in fig. 4.

The first capacitor C300 and the second capacitor C301 are connected in parallel, and then one end of the first capacitor C300 is grounded, the other end of the first capacitor C and a +18V second voltage source are respectively connected with the collector of the second triode Q102, the first capacitor C300 is a polar capacitor, and the base of the second triode Q102 is connected in series with the first resistor R102 and is connected with the fourth voltage source VCC.

One end of a third capacitor C304 is grounded, the other end of the third capacitor C and a +9V first voltage source are respectively connected with a collector electrode of a third triode Q103, a base electrode of the third triode Q103 is connected with a second resistor R104 in series, an emitting electrode of the third triode Q103 is connected with a third resistor R105 in series, and the R105 is connected with an emitting electrode of a second triode Q102.

In the embodiment of the present application, the driving transformer circuit 300 may further include a first transistor Q101 and a fifth resistor R103. The collector of the first triode Q101 is connected in series with a first resistor R102 and is connected to a fourth voltage source VCC, the base of the first triode Q101 is connected in series with a fifth resistor R103, and the transmitter of the first triode Q101 is grounded.

Thus, when the IO port of the transformer driver is input with a low level, i.e., when the driving transformer signal is at a low level, the first transistor Q101 is turned off, the second transistor Q102 is turned on, so that the +18V second driving voltage is connected to the power switch driving circuit 400, and the +9V first driving voltage is turned off.

When the IO port of the transformer driver inputs a high level, that is, the driving transformer signal is at a high level, the first transistor Q101 is turned on, the second transistor Q102 is turned off, and the third transistor Q103 is turned on, so that the +18V second driving voltage is turned off, and the +9V first driving voltage is connected to the power switch tube driving circuit 400.

It should be noted that in the implementation scheme provided in the embodiment of the present application, the use under low power still needs to be implemented by matching with the zero-crossing detection module, specifically, the main control module sends the driving transformation signal to control the high level and the low level of the IO port of the driving transformation circuit to change according to the received zero-crossing signal from the zero-crossing detection module.

In the embodiment of the application, for the zero-crossing detection module, the zero-crossing detection module rectifies the alternating-current power supply and then obtains a zero-crossing signal by detecting a zero-crossing point. The zero-crossing detection module 200 continuously detects the rectified dc signal processed by the rectifying and filtering module 602 and outputs a zero-crossing signal to the main control module 100; the main control module 100 controls the driving transformation circuit 300 and the power switching tube driving circuit 400, the period of the zero-crossing signal is about 2 to 10ms (usually 2 to 3ms), and the period of the driving transformation signal is similar to that of the zero-crossing signal; the period of the driving signal such as the PPG signal sent by the main control module is several to several tens of μ s, that is, the driving signal that drives the power switch tube through the plurality of main control modules is within the duration of the high level or the low level of a zero-crossing signal.

When the driving transformer circuit 300 inputs a high level and is turned on, if the PPG signal (driving signal) is a high level, the power switching tube driving circuit 400 is turned off, the +18V power module is turned off, the system is in a turn-off state, and at this time, the driving waveform of the IGBT is at a low level; if the PPG signal is at a low level, the power switching tube driving circuit 400 is turned on, at this time, the IGBT driving waveform is at a high level, and the IGBT operates at the first driving voltage of + 9V.

When the driving transformation circuit inputs low level and the driving transformation circuit 300 is disconnected, the power switch tube driving circuit 400 acts alone, the PPG signal is high level, then the +18V power module is disconnected, and the IGBT driving waveform is at low level; and when the PPG signal is at a low level, the +18V power module is switched on, the IGBT driving waveform is at a high level, and the IGBT works at a +18V second driving voltage.

Referring to fig. 4, the fourth voltage source VCC is connected to the second driving voltage of the second diodes Q102 to +18V, so that the voltage provided by the fourth voltage source VCC is greater than the second driving voltage of +18V by 0.5 to 1V, for example, about 0.7V, to ensure that the second diode Q102 can be in saturation conduction, and ensure that the voltage connected to the power switch driving circuit 400 is the second driving voltage of + 18V.

The functions of the resistors are as follows: the third resistor R105 functions as an isolation to isolate the transistor to which the +18V second driving voltage is input from the transistor to which the +9V first driving voltage is input, thereby preventing the transistors from being damaged during voltage switching. The first resistor R102, the fifth resistor R103, and the second resistor R104 are all driving resistors, and are used to prevent excessive current from flowing through the connected transistors when the transistors are turned on.

Referring to fig. 4, the power switch driving circuit 400 is connected in parallel with a first voltage regulator ZD1 and a resistor R101 between the gate and the emitter of the power switch 500. The voltage-stabilized voltage of the first voltage-stabilized tube ZD1 may be +18V, and the emitter of the power switch tube 500 is grounded.

With the above, in the implementation process of the embodiment of the present application, the heating control principle of the electromagnetic heating device is as follows:

and controlling the electromagnetic heating device to enter a discharging stage and a heating stage in sequence in each control period. In the discharging stage, the driving voltage of the IGBT is reduced to a first driving voltage through the driving voltage transformation circuit, so that the IGBT works in an amplification area; when the voltage of the collector of the IGBT oscillates to the minimum, the IGBT enters a heating stage, the driving voltage of the IGBT is increased to a second driving voltage by the power switch tube driving circuit, and the IGBT works in a saturation region and works normally. When the next working cycle, the discharge stage and the heating stage are started, and the process is repeated. The method comprises the following specific steps:

the zero-crossing detection module processes the zero-crossing signal (such as time delay amplification) before the zero-crossing point of the alternating current power supply and transmits the zero-crossing signal to the main control module, so that the main control module drives the driving transformation circuit to enable the IGBT to work under the driving of a first driving voltage, and drives the transformation circuit to stop working when the voltage oscillation of a collector of the IGBT is minimum, so that the IGBT works under the driving of a second driving voltage, wherein the second driving voltage is greater than the first driving voltage. Therefore, when the electromagnetic heating device is heated, the IGBT is started and switched on in a variable voltage driving mode, so that the switching current of the IGBT is reduced, the damage caused by hard switching of the IGBT can be reduced, the switching noise can be reduced, the serious heating of the IGBT is avoided, the operation reliability of the electromagnetic heating device is improved, and the heating power range of the electromagnetic heating device can be widened.

On the basis of the implementation shown in fig. 3, an implementation shown in fig. 5 is further provided in an embodiment of the present application. That is, under the condition that the driving transformer circuit 300 and the power switch tube driving circuit 400 are not changed, the power module 301 is adjusted to divide three voltages, namely, a first driving voltage, a second driving voltage and a third voltage (for example, +5V), into the power module 301. That means, the third voltage is not obtained by the first driving voltage, so that the third voltage and the output of the first driving voltage can not interfere with each other during the operation of the heating control circuit, thereby improving the reliability of the circuit.

The embodiment of the application provides an electromagnetic heating device which can comprise a circuit structure shown in fig. 2 or fig. 4. For the working mode corresponding to the circuit structure of the electromagnetic heating device, reference may be made to the foregoing description, which is not repeated herein.

The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for the system embodiment, since it is substantially similar to the method embodiment, the description is simple, and for the relevant points, reference may be made to the partial description of the method embodiment.

The above description is only an example of the present application and is not intended to limit the present application. Various modifications and changes may occur to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims (10)

1. A heating control circuit for heating control of an electromagnetic heating device, the heating control circuit comprising:

a resonant heating module;

the rectification filtering module is used for carrying out rectification filtering processing on the alternating current power supply;

the power switch tube is used for controlling the resonant heating module to perform resonant operation;

a power switching tube driving circuit;

the driving voltage transformation circuit enables the power switch tube to be switched on in a voltage reduction mode when the power switch tube is switched on; the voltage of the power switch tube which is reduced and switched on is a first driving voltage, the voltage of the power switch tube which is switched on when the driving transformation circuit is switched off is a second driving voltage, and the second driving voltage is greater than the first driving voltage;

the power supply module is connected with the driving transformation circuit, is provided with a first voltage source and a second voltage source, and provides a first driving voltage and a second driving voltage for the switching-on of the power switching tube;

the main control module is connected with the power switch tube driving circuit, the driving transformation circuit and the power supply module; the main control module is used for sending a driving signal to the power switching tube driving circuit so as to drive the power switching tube to be switched on and off; and sending a driving transformation signal to the driving transformation circuit, and selecting one of the first voltage source and the second voltage source to control the power switch tube to be switched on under the first driving voltage or the second driving voltage.

2. The heating control circuit of claim 1, wherein the power module further comprises a third voltage source for providing a third voltage to the main control module, wherein the third voltage is less than the first driving voltage.

3. The heating control circuit of claim 2, wherein the power module is connected to a three-terminal regulator at the first driving voltage, so that the first driving voltage obtains a third voltage through the three-terminal regulator, and the third voltage is used for supplying power to the main control module.

4. The heating control circuit of claim 1, wherein the power switch operates in an amplification region at the first drive voltage; and under the second driving voltage, the power switch tube works in a saturation region.

5. The heating control circuit of claim 1, further comprising a zero-crossing detection module that detects a zero-crossing of the ac power source to obtain a zero-crossing signal; the zero-crossing signal is transmitted to the main control module, so that the main control module sends a driving transformation signal to the driving transformation circuit.

6. The heating control circuit of claim 1, wherein the power switch tube driving circuit is connected in parallel with a first voltage regulator tube between the gate and the emitter of the power switch tube.

7. The heating control circuit of claim 1, wherein the driving transformation circuit comprises a first transistor and a second transistor;

when the driving transformation signal is at a low level, the first triode is disconnected, the second triode is connected, so that the second driving voltage is connected to the power switch tube driving circuit, and the first driving voltage is disconnected.

8. The heating control circuit of claim 7, wherein the driving transformer circuit further comprises a third transistor;

when the driving transformation signal is at a high level, the first triode is conducted, the second triode is cut off, the third triode is conducted, so that the second driving voltage is cut off, and the first driving voltage is connected to the power switch tube driving circuit.

9. The heating control circuit of claim 1, wherein the driving transformation circuit comprises a second transistor, a third transistor, a first capacitor, a second capacitor, a third capacitor, a first resistor, a second resistor, and a third resistor; the power supply module is also provided with a fourth voltage source;

one end of the first capacitor is grounded after being connected with the second capacitor in parallel, the other end of the first capacitor is connected with the collector of the second triode respectively with the second voltage source, and the base of the second triode is connected with the first resistor in series and is connected with the fourth voltage source;

one end of the third capacitor is grounded, the other end of the third capacitor is connected with the first voltage source and the collector electrode of the third triode respectively, the base electrode of the third triode is connected with the second resistor in series, and the emitter electrode of the third triode is connected with the third resistor in series and is connected with the emitter electrode of the second triode.

10. An electromagnetic heating device comprising the heating control circuit of any one of claims 1 to 9.

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