Digital Control Technique Of Parallel Resonant Inverter

Control strategy for the parallel-resonance induction heating power supply is designed in this paper. It analyzed the load character and control object for a parallel inverter. the conclusion that series and parallel resonant circuit are two antithetic circuits is pointed out, this provides a theoretical guide to the control circuit design for these two inverters. Through the analysis of different operating states, it is pointed out that a capacitive quasi-resonant state is a safe and efficient working condition for a parallel inverter. After analyzing the control principle of phase-locked loop and the current usage of fixed-angle-control for phase locking, a new control method using phase-locked loop is presented. It is used in induction heating power supply and realizes fixed-angle-control. The hardware circuit and the software design of the Programmable Logic Device based on VHDL are designed, which successfully solve the digital of phase discriminator,frequency divider,overlap time and dynamic delay;A novel and practical over-voltage protective method for parallel inverters is presented which effectively avoid the possible over-voltage destroy to the inverter.