Design Methodology of Series Resonant Half Bridge Inverter for Induction Cooker

Abstract

Induction heating is a commonly used method of heating in household appliances due to its efficiency and high reliability. In induction cookers, resonant inverter circuits are frequently chosen due to their high efficiency and the ability to facilitate soft switching. Among the resonant inverters used in induction cookers, the half-bridge series resonant (HBSR) inverter topology is often preferred for applications where a balance between cost and power is required. Despite the numerous circuit designs proposed to enhance the performance of HBSR converters, a standardized design methodology suitable for circuit design dedicated to induction cookers has not yet been established. In this study, a new HBSR inverter design methodology supported by various theoretical equations is proposed for use in household induction cooktops. In the proposed design, the first step involves calculating the equivalent resistance value of the coil. Subsequently, a coil capable of achieving this resistance value is mechanically designed. Finally, the capacitance value for the resonance circuit is calculated. In particular, calculating the equivalent resistance value before designing the coil enables the practical implementation of a viable coil design. To validate the proposed design methodology, controlling the power transferred to the resonant circuit is necessary. For this purpose, the frequency modulation technique achieves closed-loop power control using the peak value of coil current. Additionally, it also needs to be proven that the implementation circuit works with soft switching between the maximum and minimum switch cut-off currents. To assess the compliance of the proposed design method with standards, thermal measurements were taken from semiconductors, EMC measurements were conducted to verify compliance with the IEC 55014-1 standard, and finally, the power transferred to the resonant circuit was calculated using oscilloscope measurements. Using the proposed design method, calculations were performed for a 20 cm diameter iron pot with a 2300 VA power transfer at 230 VAC mains voltage. Subsequently, these calculations were verified using various simulation tools, and finally, a prototype implementation circuit was realized to demonstrate the reliability of the proposed design method.