Control scheme for TRIAC dimming high PF single-stage LED driver with adaptive bleeder circuit and non-linear current reference

Abstract

Control scheme for TRIAC dimming high PF single-stage LED driver with adaptive bleeder circuit and nonlinear current reference is studied in this paper. The target of the control scheme is to achieve high efficiency and high compatibility to different kinds of TRIAC dimmers. The control scheme includes adaptive bleeder circuit control, operation modes control, non-linear current reference and output current estimation. The adaptive bleeder circuit regulates the bleeder current according to the phase angle to reduce the loss. The driver operates in boundary conduction model under large phase angle for achieving high efficiency and operates in discontinuous conduction mode with adaptive off-time control for frequency limitation. In order to achieve wide dimming angle, a non-linear current reference circuit is proposed. The output current estimation circuit is applied to estimate the output current so that the switch can be driven directly. Three topologies of TRIAC dimmable driver including floating buck, floating buck-boost and flyback with proposed control schemes are presented in this paper. Detailed theoretical analysis and optimal design considerations are presented. Finally, a 63V/135mA LED driver prototype based on floating buck-boost topology with the proposed control scheme was built up. High dimmer compatibility has been achieved.