A Resonant Current Phase Angle Difference (θ)-Controlled Zero Voltage Soft-Switching High-Frequency Inverter

—Characteristics of Efficiency Improvement by Employing Sub-Mode Power Control Schemes—

Abstract

Practical evaluations of an efficiency-improved zero voltage soft-switching (ZVS) high-frequency resonant (HF-R) inverter for induction heating (IH) applications are presented in this paper. By adopting a dual-mode power regulation method that consists of the phase angle difference (θ) control and another effective control strategy such as pulse density modulation (PDM), pulse frequency modulation (PFM), and asymmetrical pulse width modulation (A-PWM), the IH load power can be widely regulated under the condition of ZVS while maintaining high efficiency even in a low-output power setting. The actual performances of the output power regulations and ZVS operations are obtained from an experiment based on the 1kW-60kHz laboratory prototype, after which the validity of each sub-mode power control scheme is evaluated from a practical point of view.