A DC bus voltage reduction technique for single-stage AC-DC forward converters

There are several key criteria to consider when designing single-stage ac-dc converters, such as primary-side dc bus voltage level, input current harmonics, and output power. Satisfying these criteria for higher power converters, such as a two-switch single-stage forward converter is challenging because of the wide line and load range that these converters operate with. A technique that can reduce the dc bus voltage and be used in higher power single-stage converters is proposed in this paper. The reduction in voltage allows for greater flexibility in the design of the converter. In this paper, a design procedure based on the use of steady-state characteristic curves is developed. The procedure can be used to select the values of key converter parameters, and is demonstrated with the design of an example converter. Experimental results obtained on a laboratory prototype are presented to confirm the concepts discussed in the paper.