A 110-V AC, 17.1-W multi-segmented LED driver with 96.2% power factor

This paper presents an AC-powered, boostconverter LED driver that can be implemented with lowinductance inductor and low-voltage capacitors to reduce component costs. The proposed LED driver achieves this by segmenting the LED string into multiple sections and varying the number of LED sections connected in series and then to the charging inductor depending on the input AC voltage level, in a novel fashion to regulate the total current level as well as balancing the individual LED current levels. The switching schedule of the LED sections and pulse-widths are preprogrammed into a look-up table, which is played when it is triggered by an input´s zero-crossing event. A digital feedback loop compensates the pulse-width schedule with an offset to address the parameter uncertainties and maintain high power factor levels. A prototype LED driver demonstrates 96.2% power factor and 86.1% power efficiency while delivering 17.1-W to three sections of high-brightness white LEDs and reducing the capacitor voltage stress by 66.7%.