LED driver and driving method

摘要

An LED driver includes a power converter to convert an input voltage to a regulated voltage, a current source to be connected with an LED string in series between the power converter and a bias node, and a switching circuit to apply a bias voltage to the bias node to set the total voltage drop of the LED string and the current source. By controlling the total voltage drop of the LED string and the current source, the LED driver will automatically select a boost mode or a buck mode for operation, thereby improving the efficiency thereof.

主权项

1. An LED driver comprising:
a first output terminal and a second output terminal for an LED string connected therebetween; a power converter for converting an input voltage to a regulated voltage; a switching circuit connected to a bias node for applying a bias voltage thereto; a current source connected to the first output terminal or the second output terminal such that the current source and the LED string will be connected in series, with the combination of the current source and the LED string connected between the power converter and the bias node; and a detector connected to the current source and the switching circuit for detecting a voltage drop of the current source to control the switching circuit to select one of a plurality of supplied voltages as the bias voltage to apply to the bias node; wherein the bias voltage sets a total voltage drop of the combination of the current source and the LED string.