A novel passive type LED driver for static LED power regulation by multi-stage switching circuits

A novel passive-type LED driver that can regulate LED power PL statically for the source voltage Vs variation is proposed. Contrary to switch-mode-power-supply (SMPS) type LED drivers, the proposed LED driver is based on passive type LED driver, which does not use pulse-width-modulation (PWM) technique. Thus, the LED power regulation with high power efficiency and a long lifetime of LED operation can be simultaneously performed by multi-stage switching circuits. The LED power can be calculated and controlled by micro controller unit (MCU), which selects the number of operating LEDs in series ns appropriately for the static LED power regulation. A prototype LED driver of 100 W was implemented and verified by experiments, where 90 W <; PL <; 110 W of a small LED power variation with 95.4 % ~ 97.1 % of very high efficiency for 200 V <; Vs <; 245 V was achieved with five stage switching circuits, meeting power factor (PF) and total harmonic distortion (THD) regulation.