Fixed-Frequency Circulant Phase-Shift Controlled Current-Fed Resonant Converter with Wide Voltage Gain Range

This article proposes a novel current-fed LLC resonant (CFLLC) converter for wide voltage range applications. For the proposed CFLLC converter, it is obtained by integrating a boost inductor, two series-connected voltage source submodules (VSMs) and a resonant tank. The output voltage can be regulated by the fixed-frequency circulant phase-shift (FFCPS) modulation method. And the switching frequency is fixed at the resonant frequency, which is conducive to the design of magnetic components. Compared with other CFLLC converters, the proposed solution has a simpler single-stage structure and lower voltage stress borne by switching devices over a wide input range, which reduces the number and cost of components. Based on the FFCPS modulation strategy, the proposed CFLLC is characterized by wide voltage range, high efficiency and self-balancing performance of VSM capacitor voltages without introducing the control complexity. In addition, zero-voltage switching of all power devices can be achieved through the collaborative design of the boost inductor and transformer. The main working principle of CFLLC is expounded in more depth. A laboratory prototype is built for experimental verification. The experimental results verify the correctness and feasibility of the theoretical analysis.