A software phase-locked loop of control system of a series-resonant voltage-source inverter for induction heating equipment

Using a pulse density modulation (PDM) to regulate a load current of a resonant voltage-source inverter causes fluctuation of a current amplitude. The paper proposes a software phase-locked loop (SPLL) of control system in a resonant voltage inverter with PDM for induction heating equipment. The proposed SPLL changes a dead-time between control pulses of inverter transistors, taking into account current amplitude changes at the inverter output under PDM to provide a phase shift between its output voltage and current, which ensures lower dynamic power loss in these transistors. The paper presents results of experimental investigation of the proposed SPLL.