Two-Phase Hybrid Buck-Boost Converter With Coupled-Inductors Under ZVS Operation for USB PD Bidirectional Conversion

This paper proposes a two-phase hybrid buck-boost converter, which meets the criteria of USB PD 3.1, with an auxiliary inductor LAUX to achieve soft switching by the zero voltage switching (ZVS) technique at light loads. Besides, two interleaving phases can reduce the inductor current to half of that conventional design. Benefiting from a coupled inductor with a negative mutual inductance (ML(AC)becomes small to achieve low output voltage ripple due to large equivalent inductance Leq in a steady state. Based on the loading current, the phase shedding can change the number of driving phases for high efficiency. Moreover, a transient enhancement circuit is proposed to speed up transient response time. The proposed circuit achieves the maximum inductor current ripple reduction of 9.09% and the maximum PACₗossreduction of 17.36% at D=0.5. Experimental results show 96.1% peak efficiency. In the case of the load step 0.5A to 5A, the recovery time and undershoot are reduced to10.7μs and 133mV, respectively, and in the case of the load step 5A to 0.5A, the recovery time and overshoot are reduced to9.4μs and 147mV, respectively.