| 摘要 |
A circuit 1500 for powering an LED light source 208 includes a filter 1420, a transformer 1422, such as a flyback converter, and a controller 1410. The filter receives an input voltage VIN and filters the input voltage to provide a filtered voltage. The transformer converts the filtered voltage to an output voltage VOUT to power the light source. The controller generates a driving signal 1462 to alternately operate a switch 1424 between a first state and a second state. The controller corrects a power factor of the circuit by controlling time durations of the first state and the second state, such that an input current IIN decreases to a predetermined level during the second state and increases to a peak level proportional to the input voltage during the first state. The controller controls the ratio of time in the first state to time in the second state to adjust an output current IOUT flowing through the light source to a target level. |
