| 摘要 |
A light sensitive dimmer switch circuit for controlling the illumination level of a light as a function of the ambient illumination level surrounding the dimmer switch circuit by selectively controlling an AC power signal provided to the light includes a photocell and a phase control circuit. The photocell is responsive to the ambient illumination level and has a conduction state associated therewith. The conduction state changes, in response to the ambient illumination level, such that the photocell effectively exhibits either a substantially open circuit or a substantially short circuit. The phase control circuit selectively varies a conduction phase angle associated with the AC power signal which correspondingly causes a variation in the illumination level of the light. The phase control circuit, in response to the photocell, selectively varies such conduction phase angle and thus the illumination level associated with the light when the photocell exhibits an open circuit and, conversely, prohibits the AC power signal from being provided to the light when the photocell exhibits a short circuit. Preferably, the phase control circuit permits the light to illuminate approximately at a full illumination level while the photocell exhibits a short circuit. Thus, the light sensitive dimmer switch circuit controls the light such that a user may operate the same in either an off region, a dimming region or a full illumination region.
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