<p>To address the problems of an insufficient voltage gain range in the low voltage range and difficulty in achieving wide range zero-voltage soft switching with phase-shifting modulation for CLLLC resonant converters, optimizing triple phase-shift modulation is proposed in this paper. The proposed optimizing triple phase-shift modulation can effectively expand the voltage gain range of the CLLLC resonant converter and improve efficiency by appropriately selecting three phase angles. First, the effects of the three phase angles on the voltage gain and the rms value of the resonant current are analyzed, and the optimal phase angle is selected. Then the voltage gain of the optimizing triple phase-shift modulation for CLLLC resonant converter is solved using the multiple-harmonic impedance model. Finally, the correctness and superiority of the optimizing triple phase-shift modulation are verified with a 1 kW experimental prototype.</p>