Electromagnetic heating noise reduction equipment and control method thereof

Abstract

The electromagnetic heating noise reduction equipment comprises a heating module, a driving module and an MCU, the heating module is used for heating cookware, the control end of the heating module is connected to the output end of the driving module, and the power input end of the heating module is connected to the output end of a current conversion module in parallel; the driving module is used for outputting voltage pulses to the heating module, the input end of the driving module is connected with a PPG port of the MCU, the output end of the driving module is connected with the control end of the heating module, and the control end of the driving module is connected with the output end of the voltage regulation control module; the MCU controls the output of the PPG port and the PWM port according to the input; the device further comprises a voltage regulation control module. And the voltage regulation control module is used for regulating the output voltage of the driving module, and the input end of the voltage regulation control module is connected with the PWM port of the MCU. During heating, the duty ratio of the PWM is controlled to be gradually increased from 0 to 100%, the grid voltage of the IGBT is controlled to be gradually increased from 9V to 18V, soft start control of continuous heating is completed through the increase of the duty ratio, and the process effectively reduces the impact of the peak current of the IGBT, reduces the starting noise and improves the experience feeling and reliability of the product.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to an electromagnetic heating noise reduction device and a control method. Background Art

[0002] The electromagnetic heating products on the market, such as induction cookers, induction rice cookers, etc., generally use a single IGBT (insulated gate bipolar transistor) to control the heating solution.

[0003] Before heating, the induction cooker will first use pulses to check whether there is a pot that meets the requirements on the stove surface. If there is, it will start heating. This detection process is called "pot detection". When checking the pot or starting or stopping heating, the noise made by the pot and induction cooker is called "pot hitting" noise.

[0004] At the beginning of each heating, the collector voltage of the IGBT is not zero (about 1.4 times the grid voltage), which leads to high conduction voltage and large instantaneous conduction current when the IGBT detects the pot or starts heating. The IGBT loss is large, especially when the grid voltage is high. The instantaneous conduction current can reach more than 150A, which has a high risk of damage. At the same time, when the pot is detected and heating starts, the pot-beating noise is also more obvious. Therefore, if the heating is frequently started and stopped, not only will the risk of damage or even explosion of the induction cooker increase, but the pot-beating noise will also greatly affect the user experience.

[0005] Traditional IGBT drivers generally have only one level of voltage (such as 18V) to drive. In order to improve the above phenomenon, the existing technology adds a voltage limiting circuit at the output end of the IGBT driver circuit and adds a low-voltage driver (such as 9V). The drive voltage has only two levels of voltage, which cannot achieve the optimal soft-start noise reduction effect. Summary of the invention

[0006] In view of this, the present invention provides an electromagnetic heating noise reduction device, which includes a heating module, a driving module and an MCU, and also includes a voltage regulation control module;

[0007] The heating module is used to heat the cookware, and its control end is connected to the output end of the driving module;

[0008] The driving module is used to output voltage pulses to the heating module, its input end is connected to the PPG port of the MCU, its output end is connected to the control end of the heating module, and its control end is connected to the output end of the voltage regulation control module;

[0009] The voltage regulation control module is used to regulate the output voltage of the driving module, and its input end is connected to the PWM port of the MCU;

[0010] The MCU controls the output of the PPG and PWM ports according to the input.

[0011] Preferably, the voltage regulation control module includes a selection circuit, a first voltage circuit and a second voltage circuit;

[0012] The selection circuit is used to select the first voltage circuit or the second voltage circuit according to the high or low level output by the PWM port, the control end of which is connected to the PWM port of the MCU, and the output of which is connected to the control end of the first voltage circuit;

[0013] The first voltage circuit and the second voltage circuit are used to generate voltage drops of different voltages. The first voltage circuit and the second voltage circuit are connected in parallel, one end of the parallel circuit is connected to a DC drive power supply, and the other end is connected to a control end of the drive module.

[0014] Preferably, the selection circuit includes a resistor R4 and an NPN transistor Q2, the first voltage circuit includes a PNP transistor Q1, resistors R2 and R12, and the second voltage circuit includes a Zener diode ZD1; one end of the resistor R4 is connected to the PWM port of the MCU, and the other end is connected to the base of Q2, the emitter of Q2 is grounded, the collector is connected in series with the resistor R2 and then connected to the base of Q1, the emitter of Q1 is connected to a DC drive power supply, the collector is connected in series with the resistor R12 and then connected to the positive electrode of ZD1, the negative electrode of ZD1 is connected to the DC drive power supply, and the positive electrode of ZD1 is connected to the control end of the drive module.

[0015] Preferably, the driving module includes resistors R7, R8, R11, NPN transistors Q4, Q3, PNP transistor Q5 and capacitor C3;

[0016] One end of R11 is connected to the PPG port of the MCU, and the other end is connected to the base of Q4. The emitter of Q4 is grounded, and its collector is connected to the base of Q3. Resistor R8 is connected in parallel between the collector and base of Q3, and its collector is connected to the output end of the voltage regulation control module. The collector of PNP transistor Q5 is grounded, and its base is connected in parallel with the base of Q3. The emitter of Q3 is connected to the emitter of Q5, and the emitter of Q5 is connected in series with R7 and then connected to the control end of the heating module. Capacitor C3 is connected in parallel between the collector of Q3 and ground.

[0017] Preferably, it also includes a power conversion module, a heating module and a pot detection module;

[0018] The power conversion module is used to convert AC power into DC power of different voltages. Its input end is connected to the power grid, and its output end is connected to the power input end of each module.

[0019] A heating module, whose power input end is connected in parallel to the output end of the current conversion module; the heating module comprises a coil disk L, a resonant capacitor C1 and an IGBT; L and C1 are connected in parallel, one end of which is connected to an output end of the current conversion module, and the other end is connected to the collector of the IGBT, the emitter of the IGBT is grounded, and the gate is connected to the output end of the driving module;

[0020] The pot detection module is used to detect whether there is a pot on the electromagnetic heating device. The two input ends are respectively connected to the two ends of the coil disk in the heating module, and the two output ends are respectively connected to the MCU.

[0021] Preferably, it also includes a zero-crossing detection module;

[0022] The zero-crossing detection module is used for detecting when the AC power of the power grid is converted from the positive half cycle to the negative half cycle and passes through the zero position. Its input end is connected in parallel between the live wire and the neutral wire of the power grid, and its output end is connected to the MCU.

[0023] The present invention also provides a control method for an electromagnetic heating noise reduction device, wherein the electromagnetic heating noise reduction device comprises a heating module, a voltage regulation control module, a driving module and an MCU;

[0024] The driving module is used to output voltage pulses to the heating module, its input end is connected to the PPG port of the MCU, its output end is connected to the control end of the heating module, and its control end is connected to the output end of the voltage regulation control module;

[0025] The voltage regulation control module is used to regulate the output voltage of the driving module, and its input end is connected to the PWM port of the MCU;

[0026] The control method comprises the following steps:

[0027] S5: The PWM port of the MCU outputs a PWM signal with a duty cycle gradually increasing from 0 to 100% to the driving module; at the same time, the PPG port of the MCU outputs a PPG pulse sequence signal to the driving module.

[0028] Preferably, the voltage regulation control module includes a selection circuit, a first voltage circuit and a second voltage circuit; the selection circuit is used to select the first voltage circuit or the second voltage circuit according to the output of the PWM port, and its control end is connected to the PWM port of the MCU, and its output is connected to the control end of the first voltage circuit; the first voltage circuit and the second voltage circuit are used to generate voltage drops of different voltages, and the first voltage circuit and the second voltage circuit are connected in parallel, one end of the parallel circuit is connected to a DC drive power supply, and the other end is connected to the control end of the drive module;

[0029] In step S5, when PWM is at a low level, the selection circuit selects the DC driving power supply to be output to the control end of the driving module via the second voltage circuit; when PWM is at a high level, the selection circuit selects the DC driving power supply to be output to the control end of the driving module via the first voltage circuit;

[0030] Preferably, the method further comprises step S6 performed after step S5:

[0031] S6: Keep the PWM signal duty cycle at 100%.

[0032] Preferably, the method further includes steps S2, S3 and S4 which are sequentially performed before step S5:

[0033] S2: The MCU outputs a PWM signal with a duty cycle of 0 to the voltage regulation control module, and the selection circuit selects a DC drive power supply to output to the control end of the drive module through the second voltage circuit; at the same time, the MCU outputs a PPG pulse sequence signal to the drive module;

[0034] S3: The MCU outputs a PWM signal with a duty cycle of 100% to the voltage regulation control module, and the selection circuit selects a DC drive power supply to output to the control end of the drive module via the first voltage branch; at the same time, the MCU outputs a PPG pulse sequence signal to the drive module;

[0035] S4: MCU outputs PPG high level signal to the driver module.

[0036] Beneficial technical effects of the present invention:

[0037] 1. During heating, the duty cycle of PWM is controlled to gradually increase from 0 to 100%, and the gate voltage of IGBT is controlled to gradually increase from 9V to 18V. The increase in duty cycle completes the soft start control of continuous heating. This process effectively reduces the IGBT peak current impact, reduces the starting noise, and improves the product experience and reliability.

[0038] 2. The IGBT gate voltage during pot inspection has two driving voltages of 9V and 18V. The IGBT first passes through the semi-conduction state and then to the saturation conduction state. Utilizing the characteristics of the IGBT device itself, its collector voltage first slowly decreases and then quickly decreases to 0, effectively reducing the IGBT peak current impact and improving reliability. At the same time, it greatly reduces the pot inspection noise and improves the product experience.

[0039] 3. The control circuit is simple and cost-effective. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 A schematic diagram of a circuit composition of an electromagnetic heating noise reduction device provided in an exemplary embodiment;

[0041] Figure 2 The following is a waveform diagram of the gate and collector of an IGBT in an electromagnetic heating noise reduction device provided in an exemplary embodiment. DETAILED DESCRIPTION

[0042] In order to make the objectives, technical solutions and advantages of the present application more clear, the embodiments of the present application will be further described in detail below with reference to the accompanying drawings.

[0043] like Figure 1The electromagnetic heating noise reduction device in this embodiment includes a power conversion module, a zero-crossing detection module, a heating module, a pot detection module, a driving module, a voltage regulation control module and an MCU.

[0044] The power conversion module is used to convert AC power into DC power of different voltages. Its input end is connected to the power grid, and its output end is connected to the power input end of each module. The power conversion module includes a rectifier circuit, a filter circuit, and a voltage stabilizing circuit. The rectifier circuit has a wide range of options, and can be a half-wave rectifier circuit, a full-wave rectifier circuit, a bridge rectifier circuit, a voltage doubler rectifier circuit, and other circuits. The filter circuit is used to filter out low-frequency and high-frequency noise in the DC power, and is connected between the output ends of the rectifier module. In the prior art, ceramic capacitors and electrolytic capacitors are used to filter out high-frequency and low-frequency noises respectively. The voltage stabilizing circuit converts high-voltage DC power into low-voltage DC power.

[0045] The zero-crossing detection module is used to detect when the AC power of the power grid passes through the zero position when it converts from the positive half cycle to the negative half cycle. Its input end is connected in parallel between the live wire and the neutral wire of the power grid, and its output end is connected to the MCU.

[0046] The heating module is used to heat the pot, the control end is connected to the output end of the driving module, and the power input end is connected in parallel to the output end of the current conversion module. Figure 1 , the coil disk L and the resonant capacitor C1 are connected in parallel to form a resonant circuit. One end of the resonant circuit is connected to an output end of the current conversion module, and the other end is connected to the collector of the IGBT (insulated gate bipolar transistor). The emitter of the IGBT is grounded, and the gate is connected to the output end of the driving module. The IGBT is turned on and off under the control of the driving module. When the IGBT is turned on, the coil disk L is charged to prepare for maintaining the oscillation between the coil disk L and the resonant capacitor C1. When the IGBT is turned off, the coil disk L and the resonant capacitor C1 oscillate. An alternating magnetic field is generated around the coil disk L. The magnetic lines of force of the alternating magnetic field pass through the pot and generate eddy currents at the bottom of the pot, generating the heat required for cooking. IGBT can also be a semiconductor device with switching properties such as a MOS tube (field effect transistor) and a triode.

[0047] The pot detection module is used to detect whether there is a pot on the electromagnetic heating device. The two input ends are connected to the two ends of the coil disk in the heating module, and the two output ends are connected to the MCU. Figure 1, the first voltage divider circuit formed by resistors R5 and R9 in series, one end of which is connected to one end of the resonant capacitor C1, and the other end is grounded; the second voltage divider circuit formed by resistors R6 and R10 in series, one end of which is connected to the other end of the resonant capacitor C1, and the other end is grounded. The common end of the first voltage divider circuit R5 and R9, and the common end of the second voltage divider circuit R6 and R10 are connected to the positive input and reverse input of the operational amplifier inside the MCU. When the IGBT is turned off, the voltage at the positive input of the operational amplifier will flip back and forth due to the back and forth oscillation between the coil disk L and the resonant capacitor C1. The comparator of the MCU can be set outside the MCU together with the voltage divider circuit; or, the voltage divider circuit can be set inside the MCU together with the comparator. The MCU determines whether there is a pot by the number of times the level flips.

[0048] The driving module is used to output voltage pulses to the heating module, and its input end is connected to the PPG (programmable pulse generator) port of the MCU, and its output end is connected to the control end of the heating module, and its control end is connected to the output end of the voltage regulation control module. The driving module in the present embodiment is shown in Figure X, and one end of the current limiting resistor R11 is connected to the PPG port, and the other end is connected to the base of the NPN transistor Q4, the Q4 emitter is grounded, and its collector is connected to the base of the NPN transistor Q3, and the bias resistor R8 is connected in parallel between the Q3 collector and the base, and its collector is connected to the output end of the voltage regulation control module, and the PNP transistor Q5 collector is grounded, and its base is connected in parallel with the Q3 base, and the Q3 emitter is connected to the emitter of Q5, and the control end of the heating module is connected after the small resistance current limiting resistor R7 is connected in series. Capacitor C3 is connected in parallel between the collector and ground of Q3. Capacitor C3 is a storage capacitor, which plays a role in smoothing the driving voltage. The PPG port of MCU can also be a common I / O port, and the output pulse train signal is realized by software programming.

[0049] The voltage regulation control module is used to adjust the output voltage of the driving module. Its input end is connected to the PWM (pulse width modulation) port of the MCU, and its output end is connected to the control end of the driving module. Figure 1 As shown, the base of NPN transistor Q2 is connected in series with current limiting resistor R4, the emitter is grounded, the collector is connected in series with current limiting resistor R2 and then connected to the base of NPN transistor Q1, the emitter of Q1 is connected to 18V DC drive power supply, the collector is connected in series with pull-down resistor R12 and then connected to the collector of Q3, the cathode of voltage zener diode ZD1 is connected to 18V power supply, the anode is connected to the collector of Q3, and the stable voltage V of ZD1 is ZD1 When Q2 is turned on, Q1 is turned on, and the 18V power supply is connected to the collector of Q3 through the Q1 and R2 branches. When Q1 is turned on, the collector and emitter voltages are very small, and the resistor R2 is a small resistance. The collector voltage of Q3 is about 18V; when Q2 is turned off, Q1 is turned off, and the 18V power supply is connected to the collector of Q3 through the ZD1 road. The collector voltage of Q3 is: 18V-V ZD1=9V. It can be seen that Q2 constitutes a selection circuit and plays a role in selecting a voltage branch; at the same time, Q1, R2, R12 and the 18V power supply constitute the first voltage circuit, and ZD1 and the 18V power supply constitute the second voltage circuit. There are many forms of implementation of the first voltage circuit and the second voltage circuit, such as ZD1 can be a resistor, and Q1 and Q2 can also be MOS tubes. The DC drive power supply is adjusted according to the drive voltage follower of the IGBT. The PWM port of the MCU can also be a common I / O port, and the output of pulse sequence signals with different duty cycles can be realized through software programming.

[0050] MCU controls the output of PPG and PWM ports according to the output of pot detection module, zero-crossing detection module and user's instructions. PPG module and PWM module can also be set outside MCU.

[0051] The working process of the electromagnetic heating device in this embodiment is as follows:

[0052] When in standby mode and not heating, the PWM port has no output, the PPG port outputs a high level, transistors Q1, Q2, and Q3 are all turned off, and Q4 and Q5 are turned on. The 18V voltage passes through the voltage regulator diode ZD1 and charges the capacitor C3 all the way. The IGBT gate voltage is pulled to 0V by the emitter of Q5, the IGBT is turned off, and the heating module does not heat.

[0053] The user inputs the heating command and starts the pot detection program first. When the MCU controls the PWM port to output a low level (duty cycle is 0), Q2 and Q1 are both turned off; the MCU controls the PPG module to output a PPG pulse sequence signal. When the PPG signal is high, Q4 is turned on, Q3 is turned off, Q5 is turned on, and the IGBT is turned off. The gate voltage of the IGBT is pulled to a low level (0V) by Q5, and the 18V power supply charges the capacitor C3 through the voltage regulator diode ZD1. The voltage across C3 is 9V; when the PPG signal is low, Q4 is turned off, Q3 is turned on, Q5 is turned off, and the IGBT is turned on. The 18V power supply passes through the voltage regulator diode ZD1, the transistor Q3, the resistor R7, and the gate of the IGBT. The collector voltage of Q3 is 9V, and the gate voltage of the IGBT is about 9V. The IGBT starts with a low voltage and enters a semi-conduction state. After a certain delay, the MCU controls the PWM and PPG ports to output a pulse sequence. When the PWM is low, the on-off state of each transistor and IGBT is consistent with the previous state, which will not be repeated here. When PWM is at a high level (duty cycle is 100%), Q2 and Q1 are both turned on, and ZD1 is turned off; when PPG is at a high level, Q4 is turned on, Q3 is turned off, Q5 is turned on, and IGBT is turned off. The 18V power supply charges C3 through Q1 and resistor R12, and the voltage across C3 is 18V; when PPG is at a low level, Q4 is turned off, Q3 is turned on, Q5 is turned off, and the 18V power supply is driven by Q1, R12, Q3, and R7. Since the resistance of resistors R12 and R7 is small, the voltage drop across them is very small, and the IGBT driving voltage is close to 18V, and the IGBT enters a saturated conduction state. After a certain pot detection pulse, the MCU controls the PWM port output to be low level (duty cycle is 0), controls the PPG output to be high level, and when Q2 and Q1 are both turned off, Q4 is turned on, Q3 is turned off, Q5 is turned on, and IGBT is turned off, completing the pot detection. The IGBT gate voltage during pot detection has two driving voltages of 9V and 18V. The IGBT first passes through the semi-conduction state and then the saturation conduction. By utilizing the characteristics of the IGBT device itself, its collector voltage is first slowly lowered and then quickly lowered to 0, which effectively reduces the IGBT peak current impact and improves reliability. At the same time, it greatly reduces the pot detection noise and improves the product experience. When Q3 is turned off and the IGBT is turned off, after C3 is charged to 9V or 18V, the current passing through R8 and Q4 is very small and negligible, and C3 basically enters a steady state. When Q3 is turned on and the IGBT is turned on, C3 is charged through the first voltage circuit or the second voltage circuit, and C3 is discharged through Q3. C3 will enter a dynamic charging and discharging state, dynamic balance, and achieve the function of smoothing the IGBT driving voltage.

[0054] After the pot inspection program is completed, the continuous heating program is started. The MCU first detects the zero point of the power grid. Some time before the zero point, the MCU outputs the PPG signal, the PWM port outputs a low-level signal (duty cycle is 0), Q2 and Q1 are both cut off; when the PPG signal is high, Q4 is turned on, Q3 is cut off, Q5 is turned on, the IGBT is cut off, and the 18V power supply charges the capacitor C3 through the voltage regulator diode ZD1, and the voltage across C3 is 9V; when the PPG signal is low, Q4 is cut off, Q3 is turned on, Q5 is cut off, the IGBT is turned on, and the 18V power supply passes through the voltage regulator diode ZD1, the transistor Q3, the resistor R7, and the gate of the IGBT. The collector voltage of Q3 is 9V, and the gate voltage of the IGBT is about 9V. The IGBT starts with a low voltage and enters a semi-conduction state. The collector voltage of the IGBT slowly decreases until the power grid crosses the zero point. At this time, the collector voltage follows and drops to 0V. Figure 2 , during the T1 time period, V1 is the IGBT gate voltage, and U is the IGBT collector voltage. After that, the MCU controls the PWM to output a pulse sequence with a duty cycle that gradually increases from 0% to 100%, and the duty cycle remains unchanged after it increases to 100%. When the PWM signal duty cycle is less than 100%, when the PWM signal is low and the PPG signal is high and low respectively, when the PWM signal is high and the PPG signal is high and low respectively, the on and off states of each transistor and IGBT are the same as in the aforementioned pot detection process, and will not be repeated here, but the IGBT gate drive voltage gradually increases from 9V to 18V as the PWM duty cycle increases, and when the PWM signal duty cycle is 100% and remains unchanged thereafter, the IGBT gate drive voltage remains at 18V, such as Figure 2 As shown in the T2 time period, the level of the PWM signal selects the first voltage circuit or the second voltage branch, controlling the IGBT gate voltage to gradually increase from 9V to 18V. The increase in duty cycle completes the soft start control of continuous heating. This process effectively reduces the IGBT peak current impact, reduces the starting noise, and improves the product experience and reliability.

[0055] The electromagnetic heating noise reduction control method in this embodiment comprises the following steps when in standby mode:

[0056] S1: MCU does not output PWM signal, outputs high-level PPG signal, IGBT is cut off, and the heating module does not heat.

[0057] When starting the pot detection procedure, the following steps are performed in sequence:

[0058] S2: The MCU outputs a PWM signal with a duty cycle of 0 to the voltage regulation control module, and the selection circuit selects a DC drive power supply to output to the control end of the drive module through the second voltage circuit; at the same time, the MCU outputs a PPG pulse sequence signal to the drive module;

[0059] S3: The MCU sends a PWM signal with a duty cycle of 100% to the voltage regulation control module, and the selection circuit selects the DC drive power supply to be output to the control end of the drive module through the first voltage branch; at the same time, the MCU outputs a PPG pulse sequence signal to the drive module;

[0060] S4: MCU outputs PPG high level signal to the driver module.

[0061] When starting the heating program, the following steps are performed in sequence:

[0062] S5: The MCU sends a PWM signal with a duty cycle gradually increasing from 0 to 100% to the driving module. When PWM is at a low level, the selection circuit selects the DC driving power supply to be output to the control end of the driving module via the second voltage circuit; when PWM is at a high level, the selection circuit selects the DC driving power supply to be output to the control end of the driving module via the first voltage branch; at the same time, the MCU outputs a PPG pulse sequence signal to the driving module;

[0063] S6: Keep the PWM signal duty cycle at 100%.

[0064] The above description is only the preferred embodiment of this patent and is not intended to limit this patent. For those skilled in the art, this patent may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this patent shall be included in the protection scope of this patent.

Claims

1. An electromagnetic heating noise reduction device, comprising a heating module, a driving module and an MCU, characterized in that: Also included is a voltage regulation control module; The heating module is used to heat the cookware, and its control end is connected to the output end of the driving module; The driving module is used to output voltage pulses to the heating module, its input end is connected to the PPG port of the MCU, its output end is connected to the control end of the heating module, and its control end is connected to the output end of the voltage regulation control module; The voltage regulation control module is used to regulate the output voltage of the driving module, and its input end is connected to the PWM port of the MCU; The MCU controls the output of the PPG and PWM ports according to the input.

2. The electromagnetic heating noise reduction device according to claim 1, characterized in that: The voltage regulation control module includes a selection circuit, a first voltage circuit and a second voltage circuit; The selection circuit is used to select the first voltage circuit or the second voltage circuit according to the high or low level output by the PWM port, the control end of which is connected to the PWM port of the MCU, and the output of which is connected to the control end of the first voltage circuit; The first voltage circuit and the second voltage circuit are used to generate voltage drops of different voltages. The first voltage circuit and the second voltage circuit are connected in parallel, one end of the parallel circuit is connected to a DC drive power supply, and the other end is connected to a control end of the drive module.

3. The electromagnetic heating noise reduction device according to claim 2, characterized in that: The selection circuit includes a resistor R4 and an NPN transistor Q2, the first voltage circuit includes a PNP transistor Q1, resistors R2 and R12, and the second voltage circuit includes a Zener diode ZD1; one end of the resistor R4 is connected to the PWM port of the MCU, and the other end is connected to the base of Q2, the emitter of Q2 is grounded, the collector is connected in series with the resistor R2 and then connected to the base of Q1, the emitter of Q1 is connected to a DC drive power supply, the collector is connected in series with the resistor R12 and then connected to the positive electrode of ZD1, the negative electrode of ZD1 is connected to the DC drive power supply, and the positive electrode of ZD1 is connected to the control end of the drive module.

4. The electromagnetic heating noise reduction device according to any one of claims 1 to 3, characterized in that: The driving module includes resistors R7, R8, R11, NPN transistors Q4, Q3, PNP transistor Q5 and capacitor C3; One end of R11 is connected to the PPG port of the MCU, and the other end is connected to the base of Q4. The emitter of Q4 is grounded, and its collector is connected to the base of Q3. Resistor R8 is connected in parallel between the collector and base of Q3, and its collector is connected to the output end of the voltage regulation control module. The collector of PNP transistor Q5 is grounded, and its base is connected in parallel with the base of Q3. The emitter of Q3 is connected to the emitter of Q5, and the emitter of Q5 is connected in series with R7 and then connected to the control end of the heating module. Capacitor C3 is connected in parallel between the collector of Q3 and ground.

5. The electromagnetic heating noise reduction device according to any one of claims 1 to 3, characterized in that: It also includes a power conversion module, a heating module and a pot detection module; The power conversion module is used to convert AC power into DC power of different voltages. Its input end is connected to the power grid, and its output end is connected to the power input end of each module. A heating module, whose power input end is connected in parallel to the output end of the current conversion module; the heating module comprises a coil disk L, a resonant capacitor C1 and an IGBT; L and C1 are connected in parallel, one end of which is connected to an output end of the current conversion module, and the other end is connected to the collector of the IGBT, the emitter of the IGBT is grounded, and the gate is connected to the output end of the driving module; The pot detection module is used to detect whether there is a pot on the electromagnetic heating device. The two input ends are respectively connected to the two ends of the coil disk in the heating module, and the two output ends are respectively connected to the MCU.

6. The electromagnetic heating noise reduction device according to any one of claims 1 to 3, characterized in that: It also includes a zero-crossing detection module; The zero-crossing detection module is used for detecting when the AC power of the power grid is converted from the positive half cycle to the negative half cycle and passes through the zero position. Its input end is connected in parallel between the live wire and the neutral wire of the power grid, and its output end is connected to the MCU.

7. A control method for an electromagnetic heating noise reduction device, characterized in that: The electromagnetic heating noise reduction device includes a heating module, a voltage regulation control module, a driving module and an MCU; The driving module is used to output voltage pulses to the heating module, its input end is connected to the PPG port of the MCU, its output end is connected to the control end of the heating module, and its control end is connected to the output end of the voltage regulation control module; The voltage regulation control module is used to regulate the output voltage of the driving module, and its input end is connected to the PWM port of the MCU; The control method comprises the following steps: S5: The PWM port of the MCU outputs a PWM signal with a duty cycle gradually increasing from 0 to 100% to the driving module; at the same time, the PPG port of the MCU outputs a PPG pulse sequence signal to the driving module.

8. The control method of the electromagnetic heating noise reduction device according to claim 7, characterized in that: The voltage regulation control module includes a selection circuit, a first voltage circuit and a second voltage circuit; the selection circuit is used to select the first voltage circuit or the second voltage circuit according to the output of the PWM port, and its control end is connected to the PWM port of the MCU, and its output is connected to the control end of the first voltage circuit; the first voltage circuit and the second voltage circuit are used to generate voltage drops of different voltages, and the first voltage circuit and the second voltage circuit are connected in parallel, one end of the parallel circuit is connected to a DC drive power supply, and the other end is connected to the control end of the drive module; In step S5, when PWM is at a low level, the selection circuit selects the DC drive power supply to be output to the control end of the drive module via the second voltage circuit; when PWM is at a high level, the selection circuit selects the DC drive power supply to be output to the control end of the drive module via the first voltage circuit.

9. The control method of the electromagnetic heating noise reduction device according to claim 8, characterized in that: The method further comprises a step S6 executed after the step S5: S6: Keep the PWM signal duty cycle at 100%.

10. The control method of the electromagnetic heating noise reduction device according to any one of claims 7 to 9, characterized in that: The method further includes steps S2, S3 and S4 which are sequentially executed before step S5: S2: The MCU outputs a PWM signal with a duty cycle of 0 to the voltage regulation control module, and the selection circuit selects a DC drive power supply to output to the control end of the drive module through the second voltage circuit; at the same time, the MCU outputs a PPG pulse sequence signal to the drive module; S3: The MCU outputs a PWM signal with a duty cycle of 100% to the voltage regulation control module, and the selection circuit selects a DC drive power supply to output to the control end of the drive module via the first voltage branch; at the same time, the MCU outputs a PPG pulse sequence signal to the drive module; S4: MCU outputs PPG high level signal to the driver module.

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