Dual-mode-operation half-bridge resonant converter for improved-efficiency induction heating system

Induction heating (IH) technology is nowadays widely present in domestic appliances because of its cleanness, high efficiency, and faster heating times. All of these advantages are due to its heating process, where the pot is directly heated by a varying magnetic field. As a result, the glass where the pot is supported is not directly heated and, consequently, efficiency and heating times are improved. Induction heating systems are based on dc-link inverters to generate the required alternating voltage to feed the inductor. Usually, resonant converters are used to achieve higher efficiencies and power densities. In such systems, the maximum output power and efficiency are achieved in resonance, and the switching frequency is increased to reduce the output power. As a consequence, in these converters the efficiency is also reduced in the low-medium output power range. This paper proposes the use of the half-bridge inverter in two operating modes to achieve higher efficiency in a wide output power range. The power converter topology can be reconfigured by changing the resonant capacitors through electromechanical relays. As a consequence, the entire efficiency of the cooking process is improved with a cost-effective procedure.