Design of a High Accuracy PSR CC/CV AC–DC Converter Without Auxiliary Winding

A high accuracy ac-dc converter without auxiliary winding has been proposed in this article. The converter adopts primary-side regulation (PSR) topology, sampling output voltage and current from primary inductance, then adjusting switching frequency and primary peak current of the power converter to regulate output. By switching the main power transistor and the auxiliary switching transistor alternately on and off, and using base charge storage effect to generate driving voltage, the converter charges chip-powering capacitor by primary-side current, instead of auxiliary winding. Compared to the traditional three-winding topology, the proposed converter not only achieves higher performance, but also eliminates one winding, which means fewer external components are used, transformer becomes simpler, and system cost is lower. The control chip was implemented in NEC 1-μm HVCMOS process, and a 5 V/1 A prototype has been built to verify its feasibility. Experimental results show that the control chip can be powered perfectly, and the deviations of output voltage and current are within ±1.3% and ±2.5% under different input and load conditions, whereas maximum conversion efficiency can reach a level of 78.9%.