Patent ID: 8294381

Claim:
A PWM dimming circuit for a LED lighting application, the circuit comprising: a main LED drive circuit; a LED load connected to the main LED drive circuit; a current loop configured to measure output current from the LED load; a current loop regulation circuit connected to the current loop; a main control circuit configured to receive a signal from the current loop; a PWM dimming controller configured to provide a signal to control the current loop regulation circuit and to make the current loop operate in a closed-loop mode during a period that the LED load has an output current, and to provide a shutdown signal to the main control circuit during a period that the LED load has no output current; wherein during the period that the LED load has the output current, the main control circuit controls the main LED drive circuit to set its output current at a predetermined load current; wherein during the period that the LED load has no output current, the main control circuit controls the main LED driver circuit to shut down; and wherein during the period that the LED load has no output current, the PWM dimming controller controls the current loop regulation circuit so that a current sampling signal of the current loop is forced to be equal to a current reference signal from an output of the current loop regulation circuit, so that the output of the current loop remains unchanged.