| The control method of ultra-audio-frequency series resonant induction heating power supply is mainly researched in this paper. Firstly the working principles and character of induction heating are briefly introduced. After the series resonant type and the parallel type induction heating power supply are analyzed and compared, the series resonant type main circuit is adopted. This main circuit is composed of the three-phase fully-controlled bridge using GTO and the single-phase bridge inverter using IGBT. Secondly the theory of Phased-Locked Loop (PLL) is analyzed in detail, and then a method of implementing Digital Phased-Locked Loop (DPLL) is put forward. The algorithm is well implemented using Digital Signal Processor (DSP). Then the theory of generator of triggering pulse for three-phase fully-controlled bridge is analyzed, and the method of implementing generator of pulse using VHDL language is put forward. The simulation result is given also. The hardware control system based on TMS320F240 is designed, which includes sampling circuit, protective circuit, phase-compensated circuit, keyboard & display circuit and so on. The program of system is compiled and a prototype is made and tested. The experimental results indicate the circuit is credible and the program runs well. The DPLL based on DSP is competent for ultra-audio frequency-tracking. In the end of this paper, the real waves of power supply are provided.
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