Dual Phase LLC Resonant Converter With Variable Frequency Zero Circulating Current Phase-Shift Modulation for Wide Input Voltage Range Applications

This article proposes a novel dual phase LLC resonant converter with an improved variable frequency-based zero circulating current phase-shift modulation scheme for wide input voltage applications. The presented topology employs a six-switch dual active bridge with two output ports reducing the voltage stress across upper and lower switches to half of the input voltage. The proposed modulation scheme is a three-variable control that enables the converter to operate with increased voltage gain range under all input voltage and loading conditions. Variable frequency control leads to the soft switching operation of the switches connected to the primary side for all load ranges. The phase-shift control is used as power transfer control along with maintaining a constant output voltage under changing input voltage. Moreover, the duty cycle calculation based on load conditions helps in eliminating the reverse power flow especially under light-load conditions. To verify the proposed converter and modulation scheme, a 1.5-kW prototype with 210-400-V input and 80-V output is built and tested with a peak load efficiency of 96.7%.