ADC-free digital-control switch-mode LED driver with high switching frequency

A new ADC-free digital-control switch-mode LED driver with 1MHz switching frequency is presented, which is featured by digital counters, a PWM generator, and current comparators. The digital counter consists of up/down counters with a delay routine. The counter increases or decreases its binary value, depending on comparison result between the output current and the desired current. Then a PWM signal can be generated, which its pulse width is determined by multiplication of the binary value and the clock period. To prevent oscillation of the counter value owing to high frequency clock, a delay routine is added. This designed LED driver is successfully implemented through a 0.35μm 2poly-4metal high voltage process.