Three-legs Converter with Optimized Critical Current Mode

This paper proposes an improved critical current mode control scheme for a single-phase AC-DC-AC converter, which can improve the power density and reduce harmonic suppression requirements. The proposed method achieves dual optimization by real-time adjusting the envelope shape of the inductor current and the switching frequency. Compared to the fixed reset current mode, the new scheme achieves a high power factor and zero voltage switching conditions over the entire load range. The simulation experimental results show that the total harmonic distortion rate decreased from 3.57% to 2.99%, and the LC-free resonance phenomenon was suppressed. Furthermore, a high efficiency can be achieved by the significant reduction in switch losses.