Study of digital LED driving technology based on auto-identifying open strings in LEDs array

A novel two-stage digital control driver for the high bright LEDs is proposed. The front stage is a PFC circuit controlled by the chip MC33262, the DC/DC stage is a half bridge circuit controlled by the micro-controller. The output current of the controller is adjusted according to the number of the strings in the open-circuit state, so the current of a single LED ring is always nearly constant even when several LED rings are in the open-circuit state. In the paper, the design process of the system is presented, an 112W prototype is presented in the laboratory, and the experimental results verify the control method proposed in the paper.