The utility model relates to the technical field

The utility model relates to the technical field of home appliances, more specifically, to an electromagnetic heating power circuit. Background technology: since the birth of rice cooker, the heating plate is the only heating method of rice cooker. Its principle is to transfer heat to the bottom of the inner tank through the heating plate, and then the heat is transferred to the ingredients from the inner tank. This heating method has low production cost and small control difficulty, but the heating is uneven, so it can't be accurately controlled Obvious drawbacks. With the development of technology, IH electric rice cooker has emerged. IH electric rice cooker uses electromagnetic heating to heat the food materials. The working principle of IH electromagnetic technology is to connect the alternating current through the electromagnetic coil to directly heat the metal inner tank, which passes through the heat conduction process of the heating plate and heats up rapidly; moreover, many high-end IH rice cookers introduce multi-level coils to realize the surrounding heating of the whole inner tank and realize the absolute uniform heating; IH rice cookers can also realize the precise program control of the rice stewing process System, according to the needs of each heating stage of rice to set different heating programs, rice taste and nutritional ingredients have been improved to an unprecedented height. IH rice cooker is gradually replacing the traditional rice cooker with its significant advantages and becoming the mainstream of the market. Referring to figure 1, the existing main circuit of electromagnetic heating of IH rice cooker is a single tube resonant converter, which is composed of bridge rectifier and resonant converter. By using LC resonance phenomenon, ZVS with low switching loss can be realized; however, the main circuit of electromagnetic heating of IH rice cooker is a single tube resonant converterThe disadvantages of this circuit are as follows: 1. When the first start-up or resonance is not fully established, there is a large impact current, which will cause excessive IGBT loss or direct impact damage; 2. In the resonance period, when the resonance current is too small, residual voltage will appear on the resonance capacitance, which leads to the hard opening of IGBT, which greatly increases the switching loss, and at the same time produces a large impact current and EMI disturbance The above defects will seriously affect the normal use of IH rice cooker. Technical implementation elements: in view of the shortcomings of the prior art, the utility model aims to provide an electromagnetic heating power circuit, which can reduce the impact current of IGBT and improve the EMC performance. To achieve the above purpose, the utility model provides the following technical scheme: an electromagnetic heating power circuit, which includes a bridge rectifier circuit connected with the mains power, a filter circuit coupled to the output end of the rectifier circuit, a first IGBT connected to the first output end of the electromagnetic heating power circuit and a MCU controller for controlling the first IGBT connected with the first IGBT The first output terminal and the second output terminal of the magnetic heating power supply circuit are connected with a first resonant capacitor, and the absorption circuit also includes an absorption circuit and a resonance circuit. The absorption circuit includes a first diode and a charging capacitor. The cathode of the first diode is connected with the gate of the first IGBT, and its anode is connected with one end of the charging capacitor, and the other end of the charging capacitor is grounded. The resonance circuit includes the second IGBT The emitter of the second IGBT is connected with the collector of the first IGBT through the second resonance capacitorThe gate of the second IGBT is connected with the collector of the first IGBT through the first resistance, the gate of the second IGBT is connected with the collector of the first IGBT, the gate of the second IGBT is connected with a rectifier diode, the gate of the second IGBT is also connected with the second resistance, the other end of the second resistance is connected with the cathode of the second diode, and the second diode The anode of the IGBT is connected with the collector of the first IGBT. As a preferred solution, the absorption circuit also includes a discharge resistance which is connected in parallel with the charging capacitance. As a preferred scheme, the capacitance value of the second resonant capacitor is greater than that of the first resonant capacitor. As a preferred solution, the filter circuit is an LC filter circuit. Compared with the prior art, the utility model has the advantages that the RCD absorption circuit and the auxiliary resonance circuit are added on the basis of the technical reproduction of the electromagnetic heating power circuit, the starting impact current is reduced through the RCD absorption circuit, and the electric stress of the IGBT is reduced through the auxiliary resonance circuit. This can greatly improve the performance and reliability of IGBT and the performance of EMC. Fig. 1 is the electromagnetic heating power supply circuit in the prior art; FIG. 2 is the electromagnetic heating power supply circuit in the embodiment. Specific embodiment refers to Fig. 2, an electromagnetic heating power supply circuit. The electromagnetic heating power circuit includes a parallel zener diode ZNR, a capacitor C1 and a resistance R1. One end of Zener diode ZNR is connected to the live wire of the mains power through fuse fuse,The other end of Zener diode ZNR is connected to the zero line of mains power. One end of the resistance R1 is connected with one end of the first coil with inductance L2 of two coils, the other end of the first coil is connected with the first input end of the bridge rectifier circuit, the other end of the resistance R1 is connected with one end of the second coil with inductance L2, and the other end of the second coil is connected with the second input end of the bridge rectifier circuit. Capacitor C2 is connected with capacitor C3 in series, the other end of capacitor C2 is connected with the first input of bridge rectifier circuit, the other end of capacitor C3 is connected with the second input of bridge rectifier circuit, and the connection point of capacitor C2 and capacitor C3 is grounded; one end of capacitor C4 is connected with the first input of bridge rectifier circuit, the other end of capacitor C4 is connected with the second input of bridge rectifier circuit; the second end of bridge rectifier circuit One output terminal is connected with one end of the inductance L1, and the other end of the inductance L1 is connected with the first output terminal out1 of the power circuit. The second output end of the bridge rectifier circuit is connected with the emitter of IGBT1, the emitter of IGBT1 is connected with the sampling signal input end of MCU controller through thermistor NTC, the collector of IGBT1 is connected with the first output end of power circuit through the first resonant capacitor C6, the gate of IGBT1 is connected with the control signal output end of MCU controller through the resistor R6, and the end of feedback resistor R3 is connected with the power circuit The other end of the second output terminal is connected with the feedback signal input terminal of the MCU controller; the anode of the rectifier diode zd1 is connected with the gate of IGBT1 and its cathode is grounded; the other end of the resistance R4 is connected with the gate of IGBT1 and its other end is connected with the gate of IGBT1End to ground. Diode D1 and capacitor C8 form an absorption circuit. The cathode of diode D1 is connected with the gate of IGBT1, the anode of diode is connected with one end of capacitor C8, and the other end of capacitor C8 is grounded. The working principle of the absorption circuit is as follows: when IGBT1 is first turned on, that is, when the first pulse https://www.ranzhichina.com/product/detail/heater-control-board-electromagnetic-induction-heating-induction-heating-control.html width of IGBT1 comes, diode D1 is on, PWM pulse width signal charges C8 capacitor, while capacitor C8 is 0V to the ground in an instant, then recharges and the voltage rises, so that the amplitude of the first several pulse width of IGBT1 will be lower than other normal driving voltage, which makes IGBT1 turn on for the first time Several pulse width of the unit are opened with larger internal resistance value, so as to greatly reduce the impact current of the start-up; and when the capacitor C8 is charged, the driving waveform voltage value of IGBT1 will also return to the normal power supply voltage, so that it can be opened with smaller internal value after the start-up, reduce the opening loss, reduce the heat and temperature rise; because the impact current is reduced, the performance and temperature of IGBT are greatly improved Reliability while significantly improving EMC performance. On this basis, the absorption circuit can be optimized by adding resistor R5, which is connected in parallel with capacitor C8, and resistor R5 acts as discharge resistor. After adding R5, ensure that the voltage in capacitor C8 is effectively discharged when the IGBT control signal is in the off state in each resonance cycle, so that C8 can be charged when the IGBT control signal in the next cycle is in the on state, so as to ensure that the voltage of IGBT base rises slowly and reducesVoltage conversion rate, and then reduce some impulse voltage and impulse current; improve the EMC characteristics. The power supply circuit also includes a resonant circuit. The resonant circuit includes igbt2, the collector of igbt2 is connected with the first output of the power circuit, the emitter of igbt2 is connected with the collector of IGBT1 through the second resonant capacitor C7, the anode of rectifier diode ZD2 is connected with the gate of igbt2, the anode of rectifier diode zd3 is connected with the cathode of ZD2, the cathode of zd3 is connected with the emitter of igbt2, one end of resistor R7 is connected with the gate of igbt2, and the cathode of diode D2 Connect the other end of resistor R7, the collector of anode IGBT1 of diode D2; the gate of igbt2 at one end of resistor R8, and the collector of IGBT1 at the other end. Here, the capacitance value of the second resonant capacitance C7 is greater than the capacitance value of the first resonant capacitance C6. The working principle of resonant circuit is as follows: when IGBT1 is turned on, the current flows into IGBT1 through the coil disk; when IGBT1 is turned off, the coil leads to C6 for charging; when the C6 charging voltage rises to a certain voltage (higher than the bus voltage), the continuous current diode of igbt2 starts to turn on; meanwhile, the voltage of C7 is supplied to the gate of igbt2 through R18 ~ R21, when the voltage supplied exceeds the base of igbt2 When the voltage is turned on, igbt2 is turned on. At this time, C6 and C7 are connected in parallel. The disk current of coil L1 charges C6 and C7 together. At this time, the collector of IGBT1 is reversed due to the large charging capacitanceThe charging voltage will not be too high, so that when C7 resonates alone, the voltage of the hard switch is very low and the impulse current is very small; when C6 resonates at the same time, the c-pole reverse voltage of IGBT1 will be greatly reduced; the electric stress of IGBT1 will be reduced. The above-mentioned is only the preferred embodiment of the utility model, and the protection scope of the utility model is not limited to the above-mentioned embodiments. All technical schemes under the thinking of the utility model belong to the protection scope of the utility model. It should be pointed out that for ordinary technicians in the technical field, several improvements and refinements without departing from the principle of the utility model shall also be regarded as the protection scope of the utility model. Technical features: 1. An electromagnetic heating power supply circuit, including a bridge rectifier circuit connected to the mains, a filter circuit coupled to the output of the rectifier circuit, a first IGBT connected to the first output of the electromagnetic heating power supply circuit, a MCU controller for controlling the first IGBT connected to the first IGBT, a first output and a second output of the electromagnetic heating power supply circuit The first resonant capacitor is connected between the terminals, which is characterized in that the absorption circuit and the resonance circuit are also includedThe circuit includes a first diode and a charging capacitor. The cathode of the first diode is connected with a gate pole of the first IGBT and its anode is connected with one end of the charging capacitor. The other end of the charging capacitor is grounded. The resonance circuit includes a second IGBT. The emitter of the second IGBT is connected with the collector of the first IGBT through the second resonance capacitance. The collector of the second IGBT is connected with the electromagnetic heating power circuit The gate of the second IGBT is connected with the collector of the first IGBT through the first resistance, the gate of the second IGBT is connected with the emitter by the rectifier diode, the gate of the second IGBT is also connected with the second resistance, the other end of the second resistance is connected with the cathode of the second diode, and the anode of the second diode is connected with the collector of the first IGBT. 2. The electromagnetic heating power supply circuit according to claim 1, which is characterized in that the absorption circuit also comprises a discharge resistance which is connected in parallel with the charging capacitor. 3. The electromagnetic heating power circuit according to claim 1, which is characterized in that the capacitance value of the second resonance capacitance is greater than the first resonance capacitance. 4. The electromagnetic heating power circuit according to claim 1, which is characterized in that the filter circuit is an LC filter circuit. Technical summary electromagnetic heating power supply circuit, including the bridge rectifier circuit connected to the mains, the filter circuit coupled to the output of the rectifier circuit, the first IGBT connected to the first output of the electromagnetic heating power supply circuit and the MCU controller connected to the first IGBT for controlling the first IGBT. The first output and the second output of the electromagnetic heating power supply circuit are connected with each other The absorption circuit includes a first diode and a charging capacitor, the cathode of the first diode is connected with the gate of the first IGBT, the anode of the first diode is connected with one end of the charging capacitor, the other end of the charging capacitor is grounded, the resonance circuit includes a second IGBT, the emitter of the second IGBT is connected with the set of the first IGBT through the second resonance capacitor Electrode, the collector of the second IGBT is connected with the second output end of the electromagnetic heating power circuit, the gate of the second IGBT is connected with the collector of the first IGBT through the first resistance, the gate of the second IGBT is connected with the emitter by the rectifier diode, the gate of the second IGBT is also connected with the second resistance, the other end of the second resistance is connected with the cathode of the second diode, and the second pole The anode of the tube is connected with the collector of the first IGBT. Technical R & D personnel: Lu Gaofeng protected TechnologyUser: Guangdong Shangyan Electronic Technology Co., Ltd. Document No.: 201720068919 technology research and development date: January 20, 2017 technology publication date: October 13, 2017