CONTROLLING CIRCUIT FOR AN LED DRIVER AND CONTROLLING METHOD THEREOF

摘要

The present invention relates to a controlling circuit and controlling method for an LED driver implemented as a flyback topology. The controlling circuit may be at a primary side of a transformer of the LED driver, and include a sampling circuit, an on time sensing circuit of an output diode, a regulating signal generator, and a PWM controller. The sampling circuit may generate a sampling signal indicating output current by sampling at the primary transformer side. The on time sensing circuit can detect an on time of the output diode. The regulating signal generator can generate a regulating signal by regulating the sampling signal, a voltage reference, and the on time of the output diode. The PWM controller may generate a controlling signal to control operation of a switching device of the LED driver to maintain a substantially constant output current in accordance with the regulating signal.

主权项

1. A controlling circuit for a light-emitting diode (LED) driver having a transformer, said controlling circuit comprising:
a) a sampling circuit configured to generate a sampling signal that indicates an output current signal of said LED driver at a primary side of said transformer; b) an on time sensing circuit configured to sense an on time of an output diode arranged at a secondary side of said transformer; c) a regulating signal generator configured to generate a regulating signal based on said sampling signal, a voltage reference that is directly proportional to an expected output current of said LED driver, and said on time of said output diode, wherein said regulating signal generator comprises an operational amplifier; and d) a pulse-width modulation (PWM) controller configured to generate a controlling signal to control operation of a switching device of said LED driver based on said regulating signal, and wherein an on time of said switching device is controlled by said regulating signal.