A Novel Flyback LED Driver Based on Primary Side Feedback without Auxiliary Winding

Abstract

A novel flyback LED drive based on primary side feedback without auxiliary winding is proposed in this paper. Photoelectric couple or auxiliary winding must be used to detect the current conducted through secondary side in prior LED driver system. But it causes insecurity isolation and both raises the manufacturing cost accordingly. The proposed voltage coupled network can estimate zeros crossing point of secondary current and sets the right time to turn on the switch MOS transistor after a delay time. And the current sense circuit is utilized to sense the current flows through the primary side, turning off switching transistor when the primary current rising up to a setting value. The proposed LED driver is suitable for discontinuous conduction mode (DCM). The experimental results verified theoretical analyses.