Universal dimmable driving system for various power LEDs using digital adaptation

For LED driver, the wide range of power should be accounted for designing circuits. Providing for such variety leads to increase implementation costs. In this study, a universal architecture for driving multi-power LED is presented. The architecture approaches this issue by auto-tracking output voltages so that the circuit can deliver the driving requirement for a number of in-series LEDs. The system senses the drain voltage of power MOS, and a buck converter then adaptively generates an optimal voltage for the connected LEDs. An FPGA (field-programmable gate array) controller is used to monitor the voltage cross the LED string and computes the best PWM (pulse-width modulation) duty for voltage converter based on a finite-state machine. LED dimming is realized using the analog mode rather than PWM method to prolong LED lifespan. The results showed that the auto-tracking system was able to find the optimal power level when the number of LEDs in a string changed, even if there were drop voltage differences or aging problems with the bulbs.