| 摘要 |
The light-emitting-diode lamp comprises a set of light-emitting diodes, a rectifier and power converter circuit, and a power factor controller. The rectifier and power converter circuit converts ac or dc voltage and current from a power source to dc voltage and current supplied to the set of light emitting diodes. The rectifier and power converter circuit includes an electronic switch through which it is supplied with ac or dc voltage and current from the power source, and an inductor device including windings adapted to charge a capacitor with a voltage signal representative of the amplitude of the ac or dc voltage from the power source. The power factor controller is responsive to the voltage signal across the capacitor for controlling the electronic switch of the rectifier and power converter circuit in view of supplying dc voltage and current to the set of light emitting diodes while maintaining the power factor of the light-emitting-diode lamp equal to or close to unity. The power factor controller comprises a voltage comparator supplied with the voltage signal across the capacitor for enabling operation of the power factor controller as long as the ac or dc voltage from the power source has an amplitude higher than a first predetermined voltage threshold. A voltage boosting circuit raises the amplitude of the voltage signal across the capacitor when the ac or dc voltage from the power source is lower than the first voltage threshold to keep operation of the power factor controller enabled as long as the ac or dc voltage is higher than a second predetermined voltage threshold lower than the first predetermined voltage threshold.
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