Patent ID: 8952620
Filing Date: 2015-02-10
Classification: H05B,Y02B

Abstract:
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 corresponding one of current regulating circuits, each of the current regulating circuits including a sensor amplifier and a cascade structure having first and second transistors, a source of the first transistor being directly connected to a drain of the second transistor so that the source and the drain have a same voltage potential during operation, each said group being coupled to a different voltage source for providing a different reference voltage thereto; measuring a phase of a voltage waveform of the power source; turning on the groups in a downstream sequence based on the measured phase; applying a gate voltage to a gate of the first transistor; inputting the different reference voltage to the sensor amplifier; and causing the sensor amplifier to send an output signal to a gate of the second transistor to thereby regulate a current flowing through the second transistor.