Control Strategies for Complete Soft-Switching of ICN Converters

This paper introduces the control strategies that enable zero-voltage switching (ZVS) of all the transistors in impedance control network (ICN) resonant converters. With the conventional $\phi$-based control strategy, ICN converters are well-suited for applications with wide variation in input voltage, owing to wide range soft switching capability of their inverter transistors. The control strategies presented in this paper simultaneously allow soft switching of all its inverter and rectifier transistors, thus extending the converter’s applicability to higher and wider output voltages. Two such control strategies, namely, $\psi$ and $\phi\psi$-based control, are presented and compared in terms of their soft switching capability and residual circulating currents in the resonant tank. It is shown that $\phi\psi$-based control strategy offers superior performance by substantially reducing circulating currents. A 15 V-to-2.5 V, 10- W, 400-kHz ICN converter prototype is built and tested with the proposed control strategies. $\phi\psi$-based control strategy achieves 5% higher efficiency compared to the $\psi$-based control strategy.