Research On High Frequency Induction Heating Power By CPDM Control Based On DSP

Induction heating power supply has been widely applied into industry because of itsenergy saving, high efficiency and no pollution. In this paper, the principium and evolutionsof induction heating are simply introduced, all kinds of power control methods are analyzedand compared in detail by simulation, then, a novel power control method——CompositePulse Density Modulation(CPDM) is developed. CPDM power control method not only hassimple main circuit, sine current output and reduced sinusoidal distortion and harmonics, butalso has high output power factor, ZVS, ZCS, and decreased EMI noise. According to characteristic of resonant circuit, an equal circuit model of DC/ACinverter based on CPDM control is built up. Furthermore, state space average equation ofCPDM Inverter is developed by state space average method, and small signal analysis isperformed on it. Based on small signal analysis of CPDM Inverter, small signal model ofCPDM control system is built up. All of these are valuable to designing CPDM control system,and support SCAM(Sinusoidal Current Amplitude Modulation ) theory effectively.At last, an induction heating power supply by CPDM control is designed and turned out,it uses a DSP as main controller and a novel digital PLL control, so the power system not onlycan adjust output power, but also works in Soft-Switching state, and has high out put powerfactor. It's proved that CPDM power control method is feasible and valid by experiments, soit will have excellent application futures in high frequency inverter power.