Flyback CC/CV AC–DC converter with high precision and reliability based on two-winding topology

Abstract

Due to the rapid development of consumer electronics, the demand for power adapters is increasing. Therefore, a high-precision, high-reliability, low-cost flyback AC–DC converter without auxiliary winding was proposed in this paper. The converter adopted a primary-side regulation (PSR) topology to sample the output voltage and current from the primary inductor, and adjusted the switching frequency to achieve a constant output voltage. By alternately switching the main power BJT and the auxiliary MOSFET, with the advantage of the base charge storage effect, the chip was powered by the primary-side current. A primary-side sampling resistor was placed at the negative terminal of the ground potential of the chip, which approached real-time monitoring of the primary-side current. This improved the reliability and output accuracy of the system. To verify the feasibility and performance of the proposed circuit, an IC controller was designed and fabricated under the NEC 1 μm BCD process. Experimental result showed that deviations of the output voltage and current do not exceed ± 1.4% and ± 2.3%, respectively. These results also showed that the maximum conversion efficiency can reach a level of 78.7%, which satisfies the consumer market very well.