Patent ID: 7391172
Filing Date: 2008-06-24
Classification: G09G,H05B

Abstract:
1. An illumination control circuit comprising: a first optical sensor configured to detect visible light produced by a light source and to generate a first optical sensor output; an error amplifier configured to generate a control signal based on a comparison of the first optical sensor output to a reference level; a second optical sensor configured to detect ambient light and to generate a second optical sensor output; and an inverter controller configured to generate driving signals to control power to the light source, wherein the inverter controller operates in a boost mode to power the light source using a boosted AC current of a substantially constant level when the control signal from the error amplifier indicates that the first optical sensor output is less than the reference level, operates in a normal mode to power the light source using a nominal AC current that has a lower level than the boosted AC current when the control signal indicates that the first optical sensor output is greater than the reference level, and further adjusts power to the light source in response to a change in the second optical sensor output indicating a change in ambient light conditions.