Small-signal modeling and controller design of an isolated Quasi-Switched-Capacitor DC/DC converter

This paper presents the small-signal modeling and controller design of an isolated Quasi-Switched-Capacitor (QSC) dc/dc converter. The converter serves as an auxiliary power supply in automotive applications, connecting the highvoltage battery and the 14 V power net. It employs a front-stage QSC dc/ac circuit with a 3:1 voltage step-down ratio, and a poststage synchronous-rectifier, current-doubler circuit. The output power of the converter is regulated by the switching frequency control. A small-signal model of the converter is derived by the method of state-space averaging. Comparison of the open-loop simulation results from the derived small-signal model and a detailed circuit model showcases the effectiveness of the small-signal model. A closed-loop voltage controller with feed-forward compensation is designed to regulate the output voltage. Closed-loop simulation results from both the small-signal model and the detail circuit model, and experiment results from a 1-kW prototype are provided to verify the closed-loop control.