High efficiency buck and boost type AC-AC converters

In this paper, buck and boost type AC-AC converters are proposed which are derived from the recently developed switching cell (SC) AC-AC converters. The volume of magnetic components of the SC AC-AC converters is large, and they are also associated with circulating current. The proposed AC-AC converters are free of circulating current and have smaller magnetic volume, therefore they can realize high efficiency. In addition, the proposed converters can effectively eliminate the loss due to revere recovery of body diode of MOSFETs, therefore they can make best use of power MOSFETs and fast freewheeling diodes which allow the proposed converters to get higher efficiency by reducing losses. The proposed converters are free of commutation problem, because the dead and overlap time cannot damage its switching devices. Furthermore, the proposed converters are not require to use sensing modules or resistive snubbers for commutation, and therefore they can be adopted with highly distorted input voltage and inductive load. A 250 W prototype of proposed boost type converter is tested to verify the analysis and operation of the proposed converters. It is found from the experimental results that the proposed boost type converter can get 97.7% efficiency for 50 kHz switching frequency.