Optical and temperature feedbacks to control display brightness
First Claim
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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.
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Abstract
An illumination control circuit allows a user to set a desired brightness level and maintains the desired brightness level over temperature and life of a light source. The illumination control circuit uses a dual feedback loop with both optical and thermal feedbacks. The optical feedback loop controls power to the light source during normal operations. The thermal feedback loop overrides the optical feedback loop when the temperature of the light source becomes excessive.
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Citations
20 Claims
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1. An illumination control circuit comprising:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method to improve response speed of a light source, the method comprising the steps of:
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sensing light produced by the light source with a first visible light sensor; comparing an output of the first visible light sensor to a predetermined threshold level; providing a substantially constant boost current to the light source when the output of the first visible light sensor is less than the predetermined threshold level; providing a preset nominal current to the light source when the output of the first visible light sensor is approximately equal to or greater than the predetermined threshold level, wherein the preset nominal current has a lower average level than the boost current; sensing ambient light with a second visible light sensor; and further adiusting power to the light source in response to changes in an output of the second visible light sensor. - View Dependent Claims (13, 14, 15)
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16. A liquid crystal display monitor comprising:
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at least one visible light detector located proximate to one or more backlight lamps to monitor the intensity of the backlight lamps; an inverter that monitors an output of the visible light detector and provides power to illuminate the backlight lamps, wherein the inverter operates in a boost mode to provide a boosted current to the backlight lamps when the output of the visible light detector is less than a threshold level and operates in a normal mode to provide a nominal current that has a lower level than the boosted current to the backlight lamps when the output of the visible light detector is greater than a threshold level; and an additional visible light detector located in a corner of the liquid crystal display monitor for monitoring ambient light, wherein said nominal current is adjusted responsive to said additional visible light detector. - View Dependent Claims (17, 18, 19, 20)
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Specification