A Modified Modulation for Single-Phase Quasi-Z-Source Rectifier With Fully Soft Switching in Integrated Charger Application

A soft switching modulation for a single-phase quasi-Z-source rectifier (qZSR) without an auxiliary circuit is proposed in this article. Most switches realize zero voltage switching (ZVS) and zero current switching (ZCS) turn-ON. The reverse recovery current of all freewheeling diodes can be eliminated. However, one switch cannot achieve ZVS turn-OFF at the full range of the line cycle and other switches cannot realize ZVS or ZCS at the boundary of the line cycle, which causes low efficiency. To overcome this problem, this article proposes a modified modulation. The shoot through state in one switching cycle is optimized. The shoot through state occurs when any switch is turned OFF. Therefore, all switches can realize turn-OFF with ZVS. Besides, distribution of zero vector time is modified. Thus, soft switching conditions can be achieved within full range of line cycle. The ZCS and ZVS operation and improvement of efficiency are verified by experimental prototype. Experimental results show that ZVS and ZCS operation of all switches are realized at full range.