High-Efficiency Dual-Phase LLC Converter with Asymmetric Resonant Tanks and Switch-Controlled Capacitor for EV Auxiliary Power Modules

A novel asymmetrical resonant tank design is proposed for dual-phase LLC DC-DC converters used in the auxiliary power module (APM) of electric vehicles (EVs), featuring built-in redundancy. The proposed design ensures that the impedance of one phase remains consistently either higher or lower than the other phase’s impedance across a wide input and output voltage range. Consequently, a single Switch-Controlled Capacitor (SCC) circuit suffices for effective active current sharing, reducing system complexity and implementation costs without compromising efficiency or performance. Each phase of the proposed converter is designed separately to meet the requirements of a wide voltage gain range, while maintaining an expected voltage gain relationship between the phases. A sensitivity analysis was conducted, considering the maximum phase-to-phase mismatch resulting from ±5% component tolerances between the two phases. Experimental results from a full-scale APM implementing the proposed dual-phase LLC DC-DC converter, operating with an input voltage of 250 V to 475 V, an output voltage of 9 V to 16 V, and a maximum output current of 285 A (4 kW output power), demonstrate the design’s success in achieving effective current sharing across input/output voltage and load ranges. Furthermore, the implemented APM achieves a peak efficiency of 96.3% and a load average efficiency exceeding 95.6% across the HV battery voltage range.