The ac–dc power supply units providing isolated, regulated outputs operating above 100 W typically require some form of input active power factor correction (PFC) [1] . To achieve this, a popular solution is to combine a boost PFC input stage with an “LLC” converter which isolates and controls the dc output voltage. However, a new, innovative single-stage technique for delivering regulated ac–dc power with a high input power factor offers the promise of high efficiency from no-load to full-load, while halving the number of active devices (MOSFETs) when compared to the traditional approach.
