A Driving Circuit With Partial Power Regulation for RGB LED Lamps

An efficient dimmable light-emitting diode (LED) driving circuit with partial power regulation is proposed for the lamp with three primary-color (red-green-blue, RGB) LED strings. The currents on RGB LED strings are individually regulated by a flyback converter with three output ports. A multi-phase pulse-width modulation (PWM) control scheme is introduced to operate the LED lamp at the desired irradiance and color. A driving circuit is designed for a 45-W RGB LED lamp supplied from a 24-V dc voltage source. The detailed circuit analyses for parameter design are provided. Experimental results have shown that a better circuit efficiency of the LED driver with partial power regulation over the dimmable range.