Main Circuit Structure and Working Principle of Induction Heating Power Supply

The main circuit and its working principle are shown in Figure 1, which consists of a rectifier, a filter, and an inverter.

The rectifier adopts an uncontrolled three-phase full-bridge rectifier circuit. The filter uses two electrolytic capacitors C1 and C2 connected in series to reduce the voltage borne by a single capacitor, and R2 and R3 play a role in voltage equalization. R1 is a current-limiting resistor. When the system is initially powered on, since the voltage across the capacitors is zero, the current will be very large when starting to charge the capacitors. With the current-limiting resistor R added, the current will not be too large. When the voltage across the capacitors reaches a certain value, the AC contactor K1 closes to short-circuit the current-limiting resistor, and the system can work normally.

The inverter adopts a single-phase inverter bridge, which is connected to the series resonant circuit via a transformer. By alternately driving two groups of IGBTs at the diagonal of the single phase to work, it converts the constant DC voltage into a square wave voltage with a frequency range of 10Hz - 10kHz and outputs it to the load. Its working waveform is shown in Figure 2. C3 and C4 are non-inductive snubber capacitors, which are used to suppress the surge voltage borne by the IGBTs.