Reduced Power Processing LED Driver With Constant Output Current

The performance of ac-dc LED drivers is determined by the power quality on both the ac and dc sides and the efficiency of conversion. To satisfy these specifications, a dedicated LED driver is needed. Reduced power processing is the current trend for enhancing the conversion efficiency without compromising the power quality. LED drivers powered by single-phase ac must have a high power factor (PF) and low total harmonic distortion to maintain grid power quality. Constant current must be achieved by LED drivers to prevent flickering, which can cause health problems. This article presents an architecture for driving LEDs that achieves a high PF with reduced harmonics on the ac side and maintains flicker-free operation on the dc side. A unique ripple cancellation approach using split capacitors is proposed to achieve constant output current with high conversion efficiency while reducing redundant power processing and design complexity. The new architecture offers a simple control method for effective driver operation. The proposed driver can considerably reduce the energy storage requirement at 100 Hz. Experiments show that the proposed LED driver achieved a high PF of 0.99 with lower input current harmonics and conversion efficiency of 94% at full power.