Self‐adaptive load technology for multiple‐string LED drivers

Abstract

A self‐adaptive load technology for multiple‐string LED drivers is presented. Directly operating from an AC voltage, the proposed technology realises soft switching with a self‐adaptive load resistor, so that the LED avoids the current glitch during current switching. Thus, the quality of lighting, the lifetime and the performance of the LED are improved. An AC LED driver using the proposed technology was fabricated in a 0.25 µm BCDMOS process and tested with a five‐string LED. The measured results show that the power factor is 0.998 (0.997) with 5.1% (7.2%) total harmonic distortion under 19 W 110 V/AC (220 V/AC) condition.