Dual-Phase Shifting Strategy for CLLC Resonant Converters

The CLLC resonant converter has the advantages of bidirectional power transmission, natural soft switching, and wide range voltage output. However, the gain curve is relatively smooth during high-frequency light-load operation, and it is difficult to adjust through frequency conversion; the traditional fundamental harmonic approximation (FHA) method has a large error in calculating the gain at a position away from the resonance point, which brings difficulties to the design. In order to better design the converter, this paper proposes a dual phase-shift (DPS) control method based on time-domain analysis, which can achieve a wide voltage range output without losing soft switching, and has constant current source output characteristics. Firstly, the time-domain model of the CLLC converter is analyzed, and the output voltage gain and soft switching range under DPS control are solved; then a simulation is built for verification; finally, a 200/80 V, rated power 500 W full-bridge CLLC resonant converter experimental prototype is built. The experimental results prove that the converter has good soft switching range and constant current source output characteristics.