Performance characterization of a high power factor power supply with a single power stage

A single high-frequency full-bridge power stage produces two outputs. One is connected in series with the rectified AC line to boost the bus voltage, and the other is the desired DC output. The boosting stage, implemented as a series-resonant power converter, is frequency controlled over the 120 Hz cycle to maintain the bus constant at an optimum fraction above the peak line voltage. This provides adequate wave shaping of the line current to maintain the high input power factor. Regulation of the main DC output is achieved by phase shifting the inverter pole voltages. Independent control of the two outputs provides the strong decoupling necessary, and hence good transient response. The soft switching nature of the converter improves performance and allows reduction in size/weight at frequencies in the hundreds of kilohertz. Experimental results show a power factor above 95% from 100% to 20% load, with peak efficiencies in the range of 85-86%