Universal Controller for Quasiresonant and LLC Converters

The paper proposes a versatile analog controller for quasiresonant (QRC) and resonant converters, in fact for any frequency controlled DC-DC converter. The on time and off time of the transistors can be independently controlled. Design equations are provided and a small-signal model of the controller is derived. Feasibility and validation of the proposed controller is demonstrated in a closed loop system as a voltage regulator, first comprising a zero current switching (ZCS) full-wave (FW) QRC Buck converter and then built around a LLC converter. The controller can be easily integrated in an ASIC and a digital version can be also developed.