Light emitting diode driver

摘要

A driver circuit for driving light emitting diodes (LEDs). The driver circuit includes: a string of LEDs divided into n groups, the n groups of LEDs being electrically connected to each other in series, a downstream end of group m-1 being electrically connected to the upstream end of group m, where m is a positive number equal to or less than n. The driver circuit also includes a plurality of current regulating circuits, each of the current regulating circuits being coupled to the downstream end of a corresponding group at one end and coupled to the ground at the other end and including a sensor amplifier and a cascode having first and second transistors, each sensor amplifier being coupled to a different voltage source for providing a different reference voltage thereto.

主权项

1. A method for driving light emitting diodes (LEDs), comprising:
providing a string of LEDs divided into groups, the groups being electrically connected to each other in series; providing a power source electrically connected to the string of LEDs; coupling each of the groups to a ground through a separate current regulating circuit, the separate current regulating circuit including a cascode structure having first and second transistors, wherein a source of the first transistor is directly connected to a drain of the second transistor so that the source of the first transistor and the drain of the second transistor have the same voltage potential during operation; applying a different reference voltage to the separate current regulating circuit of each said group; and increasing an input voltage from the power source to turn on the groups in a downstream sequence.