Research On PDM Power Regulation Method Of The Induction Heating Power Supply

Induction heating power supply has very important applications in manyindustrial fields. This paper describes the principles, the applications and the mainpower regulation method of induction heating power supply, in which the pulsedensity modulation (PDM) method can ensure that the inverter switching devicesalways works in the state of zero voltage switching or zero current switching. And,it can effectively improve the power conversion efficiency of induction heatingpower supply, reduce the power consumption. In view of the disadvantages that theinduction heating power supply’s output currents is easily interrupted with a lightload, the phase-locked loop circuit can not work reliably and the output power withgiven level for traditional pulse density control method, this paper presents animproved PDM power regulation method and it’s researched and designed in-depth.1. The existing PDM power regulation method are analyzed and compared, inorder to overcome its deficiencies, we propose an improved PDM power regulationmethod. In view of the induction heating power supply output power characteristics,we design a new PDM control pulse generate principles, and the control pulsegenerated based on finite state machine. A closed-loop power control circuit isdesigned which is based on anticipated algorithm module and hysteresis comparisoncontrol module. The improved PDM power regulation method effectively solve theproblem that the output load current is easy intermittent, and the output power canbe regulated quickly and continuously.2. In order to solve the problem that the system is unlocked easily, a novelphase-locked loop circuit which is suit for induction heating power PDM powerregulation method. A practical peak current detection circuit is designed. And thisphase-locked loop circuit is all digital designed with a with programmable logicdevices. The frequency spectrum of the induction heating power PDM waveform isanalyzed, this paper gives the harmonic position and the harmonic content, the lawof integer and non-integer harmonics in PDM waveform, and the relationshipbetwen harmonic content and various parameters.3. The simulation model of induntion heating power supply’s improved PDMpower regulation method is designed in MATLAB/simulink. We use VHDLhardware description language to write the programs of each module in theQuartusⅡ software, and the functional and timing simulation of each program isachieved in Modelsim software. The improved PDM digital control system iscompleted in a common field programmable gate arrays (FPGA). 4. Finally, an induntion heating power supply test prototype is devised whichcontrolled by the improved PDM power regulation method, to verify the correctnessand validity of the research and design, and we achieve good experimental results.