Soft-Switching Converter Based on Primary Series Connection and Single Transformer

This paper presents three soft switching converters in future dc microgrid system applications. The studied circuits are consisted of series-connection of half-or full-bridge circuits with a single transformer to convert high-voltage input to low-voltage output. On high-voltage side, $\mathbf{n}$ converters are series connection to reduce the voltage rating of power switches into $\mathbf{V}_{\mathbf{in}}/\mathbf{n}$. Thus, the low voltage stress MOSFETs with low turn-on resistance can be used in each converter modules to reduce conduction loss, increase switching frequency and reduce circuit size. The control scheme of the studied circuits are using the general asymmetric PWM scheme, phase-shift PWM scheme and frequency control scheme to control load voltage stable. Power devices in these three control approaches are all turned on at zero-voltage switching such that the switching losses are reduced and high circuit efficiency is predicted. Finally, the performance of the proposed circuit was demonstrated by the prototype circuits.