A novel constant voltage primary-side regulation topology to eliminate auxiliary winding

Primary-side regulation (PSR) scheme is widely used in low-cost and low power applications such as cell phone charger and LED lighting. Generally, an auxiliary winding in the conventional flyback converter is used for both power supplier and feedback sensing. With the increase of labor cost, the transformer needs to be produced automatically. So the transformer architecture should be designed as simple as possible to meet automatic production requirement. In this paper, a novel constant voltage primary-side regulator topology is proposed to eliminate the auxiliary winding. On one hand, the controller is built in self-powered function. On the other hand, a dedicated scheme is used to guarantee the accurate output voltage sensing. Meanwhile, new technology is presented in detail to obtain better EMI performance. To verify the efficiency of the proposed constant voltage primary-side regulator topology, a dedicated constant voltage regulator integrated in a power IC is fabricated. The experimental results demonstrated that the prototype based on the proposed integrated chip has excellent regulation and EMI performance without auxiliary winding of the transformer.