Dimmable flicker-free Linear LED Driver

The paper presents the design of a linear dimmable flicker-free LED driver. The driver consists of a preamplifier in series with a linear regulator and forms a drive loop with the LED string. The output current of the pre-amplifier adjusts adaptively with the amplitude of the AC input bus and therefore, the voltage across the linear regulator remains at the minimum required to maintain the desired string current while reducing the power variation on the LEDs. In addition, the linear regulator detects and provides a constant current to the LEDs based on fluctuations in the input voltage, which effectively eliminates flicker and maintains high system efficiency. The designed driver is compatible with a variety of triac circuits and achieves flicker-free in all dimming situations. Operating across an AC input voltage of 110~150 V, with an input power of 4.5 W, the LED driver achieves larger than 85% efficiency, percent flicker of 0.03%, and power factor of 72%.