New multi-channel LEDs driving methods using current transformer in electrolytic capacitor-less AC-DC drivers

This paper proposes new multi-channel LEDs driving methods in electrolytic capacitor-less, single-stage AC-DC drivers which use current transformer(CT) to sense output current in constant current control and operate without any damage when the number of LED channels increase or decrease. To increase lifetime of the power supply, electrolytic capacitor is substituted to small polyester film capacitor. And to insure input power factor(PF) higher than 0.9, conventional Buck-Boost PFC converter is chosen due to its simplicity and low cost. The converter operates in boundary mode condition between CCM and DCM to achieve soft switching and high efficiency. In order to verify the performance of new multi-channel LEDs driving method in constant current control, a 35V, 1.3A(45W) Buck-Boost PFC converter was designed and tested to drive 2-channel LED arrays with each 2.2uF polyester film capacitor. Through test and experiment, it was verified that the proposed methods operated very well regardless of the number of LED channels.