Research On Digital Phase－Shift Control Of Induction Heating Power

Induction heating power has been used widely in industrial areas for the advantage of protecting environment and saving energy. In traditional method which uses analogy control circuit, some disadvantages such as difficult debugging and aging component are unavoidable. With the development of the technology of chip, people gradually dedicate to develop the digital design of induction heating power based on the chips, which has a lot of advantages such as agility to design, convenient to amend and easy to realize. In induction heating field, digital control is becoming the development tendency. In this paper, a digital control method of phase-shifted PWM and frequency tracing with Phase-Looked Loop is designed for the induction heating power.Firstly, the principium and characters of the induction heating are introduced in brief. The status and the evolutions of the induction heating power technology are discussed. With the series resonant induction heating power as the research object, the ways of power regulated for induction heating power are analyzed, and the phase-shifted PWM is chosen to regulate the system power and analyzed in detail.Afterwards, the Phase-Looked Loop (PLL) technology is investigated that is used widely in induction heating power control by Phase–Shift PWM (PS-PWM). Based on the available documents at home and abroad on this subject, the principle, model and tracing ability of PLL are analyzed firstly, then the liner phase model of digital Phase-Looked Loop (DPLL) is analyzed, the stability of DPLL is analyzed in theory and simulated, and then a method of implement DPLL based on Digital Signal Processor is put forward and implemented .Finally, the digital implement of combination of PS-PWM and DPLL is investigated in detail. Base on the chip of TMS320LF2407 produced by TI Corporation, the hardware and software control system of he induction heating power are designed, according to the control method. The system's simulation with MATLAB/Simulink software show the proposed control method is reasonable.