Research On PDM&PSPWM Modulated Induction Heating Power Based On DSP

First, this paper gives a brief introduction to the basic theory of induction heating and outlines the development and the status of the induction heating technique. Based on the analasys of all kinks of power modulation strategies of series resonant inverters, a new power modulation strategy called PDM&PSPWM is presented, which regulates output power of inverters by regulating both pulse-density and phase-shift angle. When compared with PDM only schemed inverters, the PDM&PSPWM schemed inverters achieve continuous power regulation and more steady output current, continuous power regulation, and operating in continuous current mode (CCM); When compared with PSPWM only schemed inverters, new schemed inverters have smaller phase-shift as well as hardly any distortion in output current. Even working under light load status, the inverter can realize quasi-sinusoid output current waveform with less fluctuation in peak value.On the basis of elaborate analysis to working process of PDM&PSPWM controlled inverter, soft-swiching of all four swiches is achieved. Formulas in calculating output voltage, current and power in one PDM cycle are aquired by analyzing one power outputing cycle. An experimental induction heating system is designed to illustrate the feasibility of the new power regulating strategy, of which every part in main circuit as well as the control system consists of DPLL and so on is designed. The experimental results illustrat the favorable performance of the new power regulating strategy.