High efficiency led drivers with high power factor

摘要

The present invention relates to a high efficiency, high power factor LED driver for driving an LED device. In one embodiment, an LED driver can include: an LED current detection circuit coupled to the LED device, and configured to generate a feedback signal that represents an error between a driving current and an expected driving current of the LED device; a power stage circuit, where a first power switch terminal is coupled to a first input voltage, and a second power switch terminal is coupled to ground; and a control circuit configured to generate a control signal according to the feedback signal and a drain-source voltage of the power switch, where the control signal, in each switch period, turns on the power switch when the drain-source voltage reaches a low level, and turns off the power switch after a fixed time interval based on the feedback signal.

主权项

1. A light-emitting diode (LED) driver configured to drive an LED device, the LED driver comprising:
a) a rectifier bridge configured to receive an AC input voltage source, and to provide a first input voltage and a second input voltage; b) an LED current detection circuit coupled to said LED device, wherein said LED current detection is configured to generate a feedback signal that represents an error between a driving current and an expected driving current of said LED device; c) a power stage circuit configured for a buck topology and having a power switch, wherein a first power switch terminal is coupled to said first input voltage, and a second power switch terminal is coupled to ground; d) a control circuit coupled to said LED current detection circuit and said power stage circuit, wherein said control circuit is configured to generate a control signal according to said feedback signal and a drain-source voltage of said power switch, wherein said control signal is configured, in each switch period, to turn on said power switch when said drain-source voltage reaches a low level, and to turn off said power switch after a fixed time interval based on said feedback signal; and e) a bias power supply generating circuit having a diode and a capacitor, wherein said diode is coupled between a common node of an inductor of said power stage circuit and said LED device, and wherein a voltage at a common node of said diode and said capacitor is configured as a bias power supply of said control circuit.