Current-Fed LC Series Resonant Converter With Load-Independent Voltage-Gain Characteristics for Wide Voltage Range Applications

This article proposes a current-fed LC series resonant converter, which integrates a two-phase interleaved boost circuit with a full-bridge LC series resonant converter. All switches can achieve zero voltage switching (ZVS) under full load range without utilizing a magnetizing inductor or an auxiliary inductor, and synchronous rectification (SR) can be realized without SR driving detection. With the proposed modulation, the resonant current is discontinuous without circulating current. Moreover, the voltage gain of the LC series resonant conversion is fixed, which is independent of load; therefore, the design of voltage regulation range and related parameters can be simplified. The integrated boost circuit works in the critical current mode to achieve ZVS for all the switches. Meanwhile, digital adaptive frequency modulation is presented to ensure ZVS realization and to minimize the boost inductor current ripple. The working characteristics and design considerations for the key parameters of the proposed modulation are also presented in detail in this article. Finally, a 600-W prototype with 27–54 V input and 360 V output is built, and experimental results validate the effectiveness and the advantages of the proposed solution.