Improving power quality in series resonant inverter for induction heating applications

This paper proposes a method to improve power quality in resonant converters for industrial induction heating applications, which is characterized by a full-bridge inverter the switches consist of insulated-gate bipolar transistor (IGBT) and a power control based in pulse-frequency modulation (PFM). This power control strategy allows the inverter to work close to the resonance frequency and improve power quality of the inverter. In this situation, zero-current switching (ZCS) conditions are performed, and the switching losses are minimized. An additional improvement of inverter efficiency is achieved by choosing appropriate values of the modulation index. After an analysis of the switching and losses process in the converter, a control strategy is also explained, as well as the criteria for the design of a lossless switched for the devices in the inverter. The results were tested and simulated in the laboratory to validate the proposed method.