Design of a digital LED driver with auto-identifying open strings

In this paper, a novel digital control topology for high bright LEDs is proposed. And this driver can identify the open strings in LEDs array automatically to increase the reliability of the LEDs. There are two stages in this topology. The front stage is a PFC circuit controlled by the chip MC33262, and 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 can keep a constant value even when the number of working LED strings is changed. 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.