Abstract

The paper explains the operating principle of an LLC resonant circuit for induction heating applications. Although induction heating has attracted a great deal of attention in recent years, very little consideration on designing the inductor in the resonant circuit for specific requirements has been done. Specifically, a design procedure with the required power and work-head dimension as inputs is still needed, from a practical point of view. In this paper, a quantitative analysis of power transferred to the work-head will be done to help design the resonant circuit. A design procedure for the LLC circuit will be proposed, utilizing results from the quantitative power analysis and taking into account mechanical constraints on the work-head. In addition, a simple technique to monitor the soft switching condition of the power switches in the resonant inverter, utilizing only voltage signals, is also proposed. The feasibility of the proposed design procedure will be demonstrated and verified by simulations and experiments.