A control technology to achieve a low cost flicker-free single stage LED driver with power factor correction

Conventional single-stage AC-DC LED drivers with a high power factor contain significant LED current ripple at twice the AC frequency. This paper proposes an average current modulation method that is capable of driving LEDs from a voltage with large AC ripple, while maintaining zero low frequency current ripple. This allows the energy storage capacitance to be reduced, avoiding the need for electrolytic capacitors and prolongs the life of the driver. The average current modulator requires a single low voltage MOSFET, a current sense resistor and a simple control circuit, which keeps the cost of the modulator low, and the impact on efficiency to a minimum. An 8.75 W experimental prototype has been built to verify the proposed design.