| 摘要 |
A power factor correction circuit includes an inductor L1, a diode D1, a switch Q3 and a controller 24. An input voltage Vin is applied to the inductor L1 which is cyclically discharged through the diode D1 by the operation of the switch Q3. The method of operation includes: operating a controller 24 to obtain an indication of the voltage across the switch Q3, monitoring the indication of the voltage across the switch Q3 to determine when the inductor L1 reaches a discharged state in response to the switch being in an off state, and the switch Q3 being controlled by the controller 24 to vary the on period of the switch Q3, during which the inductor is charged, for adjusting an output voltage Vbus towards a target value Vbus—target. The controller 24 monitors at least one of the indication of the voltage across the switch Q3 and the ratio of the switch on period Ton to the switch off period Toff for detecting that the input voltage Vin has a low value. |
