Dimmable AC LED Driver Based on Series Drive

In this paper, a dimmable ac LED driving circuit with high power factor and low total harmonic distortion is presented, which takes series driving via the basic unit mainly constructed by the base of the BJT connected with the drain of the MOSFET. By doing so, the problem in floating driving can be removed, i.e., no additional isolated gate drivers are needed, and furthermore, if any one of LED strings opens, then turning on the corresponding switch can still make this LED system work. Finally, a prototype circuit is established and controlled by the field programmable gate array. Via experimental results, the effectiveness of the proposed topology can be demonstrated.