As an emerging discipline, induction heating has been really applied in the past 30 years. In today's energy shortage, its importance is particularly prominent, technology is changing with each passing day, and its use is becoming more and more extensive. China began to develop induction heating technology after the reform and opening up, and its application prospects are very broad.

We first 220V AC uncontrolled rectification, through the rectifier bridge to get pulsating DC, and then electrolytic capacitor filtering to get DC DC voltage, the use of high-speed V-MOS power field effect tube to form a bridge inverter circuit, inverter high-frequency square wave AC voltage, the transformer isolation, the high-frequency high-voltage into low-voltage high-current, to achieve impedance matching. The core of the control circuit is the use of phase-locked technology to achieve automatic frequency tracking. Induction heating equipment system mainly consists of seven parts:

1. Uncontrollable rectifier circuit: In this study, uncontrollable rectification is used to convert AC power into non-adjustable DC power. In order to simplify the circuit, this topic uses PWM to adjust the duty cycle of the output voltage to adjust the power.

2. Filter circuit voltage source: Capacitor filter is generally used for inverter resonance. Here, in order to reduce the volume, an inductor is used. In order to prevent the current impact, the delay link is set in the circuit.

3. Full-bridge inverter circuit: Due to the high frequency of the device in this study, fast V-MOS field effect transistor must be used; due to the limited current capacity of the single tube, under the premise of voltage resistance, the multi-tube parallel connection is used to meet the output power requirements, and the field effect tube itself also has the characteristics of easy parallel connection.

4. High-frequency transformer isolation: The Q value of series resonance is generally large, and the resonance voltage is above 1000 volts. The transformer must be isolated, and the transformer plays the role of impedance matching. Under UHF operating conditions, the core of the transformer is a high-frequency ferrite core.

5. Regulator: In the closed feedback system, the mature and universal regulation method PI regulator can be used to achieve no static error and fast tracking.

6. Phase-locked loop: Due to the different sizes of the workpiece and the change of the frequency at any time during the temperature change of the workpiece, the inverter frequency is required to follow the resonant frequency and the phase is consistent. Through the comparison of various schemes, it is determined that the phase-locked technology can accurately follow the change of resonant frequency and control the phase.

7. Drive circuit: In the frequency of UHF induction heating equipment, only pulse transformer speed regulation in various drive circuits can meet such high speed requirements.

In recent years, induction heating technology has been widely used in metal surface heat treatment, smelting, casting, powder metallurgy, welding, bending and other traditional industrial fields. Processing areas such as welding and composite treatment of material surface coatings are also playing an increasingly important role. Electric water heaters, induction cookers, microwave ovens, etc. in daily life are also the embodiment of the application of induction heating equipment.