High Power Factor Flyback Converter for LED Driver with Boundary Conduction Mode Control

A varying-frequency control Flyback rectifier for LED driving in Boundary-Conduction Mode (BCM) is presented. Comparing with Discontinuous-Conduction Mode, BCM has the advantages like smaller coupling inductor current, less current stress for circuit component, slight output current ripple, and higher power factor performance. For lower output application circumstance, the boundary conduction mode can be chosen with smaller inductance value. In this control scheme, input line voltage sensing, analog multiplier/divider and inner current loop are neglected. Design and analysis for BCM control circuit are derived and simulated. To verify the ideal vary-frequency controller, the circuit experiment has been applied to driving LED module, and stabilized the output current. The experimental results show that the system can provide constant current output with high power factor and it also compared with the system is operating in DCM.