Double step-down AC-AC converters with high frequency isolation

Abstract

In this paper, double step-down isolated ac-ac converters are proposed. The proposed converters have double step-down function and provides electrical isolation using high frequency transformer. The proposed converters avoid the saturation of transformer by adding a capacitor. In addition, the voltage stress of three bidirectional switches at the primary side of transformer is half of input voltage. The voltage across the primary winding of transformer is also half of input voltage, therefore the transformer of the proposed converters can be designed with smaller size, low leakage inductance and less isolation requirements. The proposed converters have double step-down function with high frequency galvanic isolation, and have low voltage stress across the switches and transformer, therefore they can be good candidates for solid state transformer.