| 摘要 |
A lighting source ballast utilizes switching and control technology to convert an alternating current (AC) phase modulated dimmer input voltage into an approximately constant drive current to illuminate one or more light emitting diodes (LED(s)). In at least one embodiment, the state of the drive current conforms to a phase delay of the input voltage to facilitate, for example, dimming. The phase delay of the input voltage indicates a particular dimming level. The drive current varies for different dimming levels. However, the light source ballast controls drive current so that the drive current is approximately constant for each dimming level. In at least one embodiment, the ballast emulates a resistive load and, thus, the ballast has an approximately unity power factor. The switching frequency of one or more switches can be modified to spread the spectrum of electromagnetic radiation generated by the ballast.
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