A CLLC Converter Based on Switch-Controlled Capacitors for Flexible Voltage Regulation and Efficiency Optimization

The traditional CLLC converter has a unique output voltage in the fixed frequency mode. When it relies on variable frequency control to regulate the output voltage, however, the efficiency would decline significantly due to the resonant frequency deviation. To overcome these drawbacks, this paper proposes a CLLC converter based on switch-controlled capacitors (SCC-CLLC) and adaptive gain control. Adaptive gain control can regulate its equivalent capacitance by adjusting the phase shift angles of SCC. On the one hand, in fixed frequency mode, the SCC-CLLC converter can realize flexible voltage regulation without altering the frequency. On the other hand, under various load conditions, the operating frequency can be matched in a wide frequency range to achieve efficiency optimization. The experiment results demonstrate that the proposed SCC-CLLC converter can realize a voltage gain range of 0.88 to 1.2 at an 80kHz operating frequency. Besides, compared with the diode rectifier and synchronous rectifier of the traditional CLLC, the highest efficiency of the SCC-CLLC converter is optimized by 4.2% and 3.1%, respectively, across the frequency range of 70kHz to 100kHz under various load conditions.