A novel single-switch ac/dc converter for led driver with triac dimming capability

In this paper, a novel single switch ac/dc converter is first proposed to achieve high power factor, low THDi, and lower output current ripple. Also, an input voltage feed forward control method is proposed for the proposed ac/dc converter for universal input. Moreover, considering a lot of installed TRIAC dimming controllers in existing buildings, the proposed LED driver can also be adapted to TRIAC dimmers for dimming control. A special feature is that the inrush current and current spike can be eliminated completely by the proposed driver without extra circuits. Finally, a prototype is also constructed using a low cost MCU and SMT components to achieve a fully digital dimmable LED driver to demonstrate the effectiveness of the proposed driver. It is seen that, in addition to the dimming control for universal input, the proposed LED driver can also be coordinated with a traditional TRIAC dimmer. Experimental results show that a maximum efficiency 94% can be achieved.