A Novel CC/CV AC-DC Converter Without Auxiliary Winding

Abstract

This paper presented a high precision AC-DC converter that does not require an auxiliary winding. The converter uses primary-side regulation topology to sample output voltage and current at primary inductor, then adjusting working period and primary peak current to regulate the output. The driving voltage of the power transistor is generated by using the base charge storage effect, and the chip supply capacitor is charged by the primary side current instead of being charged by the auxiliary winding. Compared to the traditional three-winding converter, the proposed converter has simpler structure, which means fewer external components, simpler transformers and lower system cost can be achieved. The chip was fabricated in NEC 1-µm process. The experimental results based on a 5V/1A prototype show that the control chip is powered very well. Under different working conditions, the deviations of output current and voltage are within ±2.5% and ±1.3% respectively, and the conversion efficiency can be as high as 78.9%.