US Patent No. 10,091,844

POWER SUPPLY FOR LED LAMP WITH TRIAC DIMMER


Patent No. 10,091,844
Issue Date October 02, 2018
Title Power Supply For Led Lamp With Triac Dimmer
Inventorship Zhimin Hu, Shanghai (CN)
Xuegang Ren, Shanghai (CN)
Assignee BCD Semiconductor Manufacturing Limited, George Town, Grand Cayman (KY)

Claim of US Patent No. 10,091,844

1. A control circuit for an LED (light-emitting diode) lighting system that includes a rectifier circuit for coupling to an AC input voltage through a TRIAC (Triode for Alternating Current) dimmer, the TRIAC dimmer being characterized by a holding current, the rectifier circuit being configured to provide a rectified DC input voltage to an inductor for supplying a constant current to an LED load, the control circuit comprises:a controller for coupling to a power switch for controlling a current flow in the inductor, the controller being configured to control current pulses in the inductor such that an envelope waveform formed by peak points of the current pulses is in phase with the AC input voltage; and
a bleeder circuit coupled to the rectifier circuit, wherein the bleeder circuit is configured to determine if that a current flow through the rectifier circuit is below the holding current of the TRIAC; and
wherein the bleeder circuit is configured to provide a compensation current, upon determining that the current flow through the rectifier circuit is below the holding current of the TRIAC, to maintain a current flow through the rectifier circuit at a magnitude of at least the holding current of the TRIAC;
wherein the bleeder circuit comprises:
a first resistor and a bipolar transistor coupled in series between the first output terminal of the rectifier circuit and a ground, a base of the bipolar transistor being coupled to a bias voltage;
a second resistor coupled between the second output terminal of the rectifier circuit and the ground; and
first and second diodes coupled in series between the second output terminal of the rectifier circuit and the base of the bipolar transistor.