Novel Single-Stage Isolated Buck-Boost Inverter Based on Improved SPWM Control Method

A novel single-stage isolated buck-boost inverter is proposed in this paper, which can generate an AC output voltage larger or lower than the input one in a single power stage. A high-frequency transformer operating as energy storage element is used to perform electrical isolation between the DC input and the AC output. The operation principle is analyzed in detail and the mathematics model is founded based on the state-space average method. An improved SPWM control method employing DC bias sine modulation wave is presented to optimize the inverter performance. The proposed control method eliminates the waveform distortion on output voltage zero-crossing area as caused by linear approximation in traditional SPWM method. The new inverter circuit topology provides the main switches for turn-on at zero current switching (ZCS) to achieve a low switching loss by a series-resonant tank. Laboratory experimental results from a 500 W prototype are given to verify the validity and effectiveness of the proposed inverter