Patent ID: 9532420
Filing Date: 2016-12-27
CPC Classification: H05B,Y02B

Claim Text:
1. An LED drive circuit, comprising: a rectifier circuit configured to receive a phase-control dimming signal with a conduction angle and output a rectified signal; a converter comprising a switching element, an input end of the converter being coupled to the rectifier circuit and an output end of the converter being coupled to an LED; and a controller having a first input end, a second input end and an output end, the first input end of the controller being configured to receive the rectified signal, the second input end of the controller being configured to receive a first sampling signal from the LED, the first sampling signal indicating a current flowing through the LED, and the output end of the controller being configured to output a control signal according to the rectified signal and the first sampling signal; wherein the switching element receives the control signal from the controller, thus executing an on/off operation to control the current flowing through the LED; wherein the rectified signal carries the conduction angle, when the conduction angle is greater than or equal to a set angle, the controller outputs the control signal so that the first sampling signal is equal to a first current reference; when the conduction angle is smaller than the set angle, the controller outputs the control signal so that the first sampling signal varies in a same trend as the conduction angle; and wherein the controller comprises: a first operational amplifier configured to receive the first sampling signal and the first current reference; a signal transmission circuit configured to enable a feedback signal to be output when the first sampling signal is greater than or equal to the first current reference, or configured to disable the feedback signal to be output when the first sampling signal is smaller than the first current reference; a regulator configured to receive the feedback signal and a reference signal to output a first regulating signal corresponding to the feedback signal when the feedback signal is enabled to be output, or configured to receive the reference signal and output a second regulating signal with a constant amplitude when the feedback signal is disabled to be output; a multiplier configured to receive the rectified signal and the first regulating signal or the second regulating signal, and to output a second current reference according to a multiplication coefficient, the rectified signal and the first regulating signal or the second regulating signal; and a switching drive circuit configured to receive a second sampling signal indicating switch current flowing through the switching element and the second current reference, and to output the control signal.