Hybrid Control Strategy for Single-Stage Interleaved Totem-Pole LLC AC-DC Converter With Input and Output Power Decoupling

This article proposes a hybrid control strategy for a single-stage interleaved totem-pole LLC ac-dc converter. Because the totem-pole power factor correction front cell provides bidirectional inductor current, this converter is restricted by operating in continuous conduction mode or critical conduction mode. The traditional control strategy shows a variable duty cycle of the resonant tank voltage to the instantaneous ac input voltage. Therefore, the line-frequency variation from the ac input-end will be easily interfaced with the load and bring a large fluctuation of output voltage. To tackle this issue, this article proposed a novel control strategy that utilizes pulsewidth modulation (PWM) to shape the input current, and pulse frequency modulation to regulate the output voltage. As a positive consequence, the large output voltage ripple brought by the variation of duty cycle for traditional PWM-based control is therefore effectively compensated by the variation of switching frequency, and the power decoupling between the ac pulse input power and constant dc output power is achieved. The numerical-based calculation method is utilized to develop the time-domain analysis of the converter, and a 500 W/150 V experimental prototype has been built to verify the proposed control strategy and theoretical analysis.