An Ultrawide Range Pulse Width Modulated LLC Converter With Voltage Multiplier Rectifiers

This article presents a voltage multiplier rectifier-based LLC resonant converter that achieves an ultrawide range of the output voltage with pulse width modulation (PWM) of the auxiliary switches on the secondary side. Compared with the pulse frequency modulated LLC topologies, the proposed topology operates at a fixed frequency and features a bounded voltage gain range. Thus, the resonant tank design can be optimized at one frequency, and high efficiency can be realized throughout the output voltage range. Furthermore, the proposed topology greatly extends the maximum PWM normalized voltage gain range to 4.0 with two-mode operations. Meanwhile, zero-voltage switching is realized for all the switches, and a seamless mode transition is achieved by the proposed converter. At last, a time-domain-based analysis and optimization methodology are proposed. A 300 kHz, 1 kW, 400 V input/250–1000 V output prototype demonstrates high efficiency through the output range and achieves 97.69% peak efficiency.