A frequency‐doubling modulation method for LLC with optimizing thermal balance of power switches

Abstract

AbstractIn order to further improve the energy efficiency of power electronic systems, DC‐DC converters can increase the power density by increasing the operating frequency to reduce the size and cost. To this end, some scholars have proposed a single‐switch frequency‐doubling (SS‐FD) modulation method, which can make the working frequency of the resonant tank of the converter twice the switching frequency. However, when the full‐bridge LLC converter operates under the SS‐FD modulation, the conduction time of each switch of the same bridge arm is different, which leads to uneven heating of the switches and reduces the overall life of the device. In order to optimize this problem, this paper proposes a dual‐switches time‐sharing frequency‐doubling (DSTS‐FD) modulation. This modulation method ensures that the resonant tank works under the premise of frequency doubling, so that the heating of each switch is more balanced, thereby increasing the overall service life of the equipment. Theoretical analysis is carried out through simulation. Finally, an experimental device of 288 V and 1000 W is built. The proposed modulation method is compared with the traditional modulation method in a stable state, and the experiment verifies the superiority of the proposed modulation method.