A Three-Leg Reconfigurable <i>LLC</i> Resonant Converter for Wide-Voltage-Gain Application

Traditional methods for extending the voltage gain of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> resonant converter typically involve either widening the switching frequency range or reducing the magnetizing inductance. However, both approaches may compromise the converter’s performance. To overcome this issue, this paper proposes a novel three-leg reconfigurable <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> resonant converter with two split resonant tanks for wide voltage gain applications. By reconfiguring the switching modes on the primary side, the converter operates in four modes with different gain ranges. Furthermore, the split resonant tanks can be connected in parallel or series through primary-side drive signal control, without the need for additional components. This topology accommodates input voltage variations from 40 V to 460 V while maintaining a fixed 50 V output. The parameters are designed to ensure zero-voltage switching and smooth mode transitions. Compared with conventional methods, the proposed strategy achieves wide voltage gain with a reduced operating frequency range of 80 kHz to 166 kHz. Finally, a 250 W prototype of the proposed converter is developed to validate its effectiveness.