All-metals Induction Heating System with Switching Between Full-bridge and Half-bridge Inverter Configurations

抄録

An induction heating system is proposed as a new circuit topology for induction-heating cookers that can be used with all metals. This system has a fixed number of work coil turns that switch the inverter between full-bridge or modified half-bridge configuration according to the cookware material and power setting. When heating cookware made of a low-resistivity material such as copper or aluminum, the inverter is switched to the half-bridge configuration; when cookware made of a high-resistivity material such as iron or magnetic stainless steel is heated at high power, the inverter is switched to the full-bridge configuration. The buck converter, which is placed in the stage before the inverter, controls the DC link voltage to adjust the power. In addition, the boost converter placed in the stage before the buck converter is switched between passive filter and active filter modes to reduce the harmonics of the commercial input current and hence improve the power factor. Tests confirm the power conversion efficiency of the inverter and boost and buck converters as well as the power control characteristics of the inverter. High efficiency over a wide power range when heating an iron pan was also confirmed.