A new control method for series resonant inverter with inherently phase-locked coil current with induction cookware applications

In this paper, a new control method for induction cookware applications with series resonant inverter has been proposed. Generally, the output power of series resonant inverter is controlled by pulse frequency modulation (PFM). However, PFM has a large turn off current and a high switching frequency as the output power decreases, resulting in a large switching turn off loss and poor efficiency. To beat these limitations, pulse width modulation (PWM), PWM-PFM mixed control, and pulse density modulation (PDM) methods have been investigated. However, they have still limitations such as control complexity or loosing zero voltage switching (ZVS) characteristics. The most powerful advantage of the proposed method is the simplicity, since the only on-time is used as the control variable. Also, it has inherent soft switching characteristics with ZVS turn-on and zero current switching (ZCS) turnoff of low side switches and zero voltage and ZVZCS turn-on of two high side switches. The effectiveness of the proposed method has been verified by 200V input voltage and 2.8kW output prototype.