Dimmer with photo sensor and high/low clamping

Abstract

Provided is a circuit for controlling a level of brightness of a light electrically coupled to a dimming circuit including control leads configured to provide a dimming control voltage to the dimmable driver, the dimming control voltage having a permissible voltage range. The circuit includes a photo sensor for detecting an ambient light level in the vicinity of the light and a clamp controller for selectively reducing the dimming control voltage to a clamped voltage range less than the permissible voltage range. Also included is a feedback controller for adjusting the dimming control voltage in response to a detected ambient light level, the dimming control voltage being within the clamped voltage range.

What is claimed is: 
     
         1 . A circuit for controlling a level of brightness of a light electrically coupled to a dimming circuit including control leads configured to provide a dimming control voltage to the dimmable driver, the dimming control voltage having a permissible voltage range, the circuit comprising:
 a photo sensor for detecting an ambient light level in the vicinity of the light;   a clamp controller for selectively reducing the dimming control voltage to a clamped voltage range less than the permissible voltage range; and   a feedback controller for adjusting the dimming control voltage in response to a detected ambient light level, the dimming control voltage being within the clamped voltage range.   
     
     
         2 . The circuit of  claim 1 , wherein the ambient light level is detected by a photo sensor;
 wherein the permissible range include a minimum and a maximum output voltage; and   wherein the level of brightness of the light is responsive to the dimming control voltage.   
     
     
         3 . The circuit of  claim 1 , wherein the dimming control voltage decreases as more ambient light is detected by the photo sensor. 
     
     
         4 . The circuit of  claim 1 , wherein the dimming control voltage is the voltage measured across the pair of low voltage control leads. 
     
     
         5 . The circuit of  claim 1 , wherein the dimming control voltage is the voltage measured across the pair of low voltage control leads. 
     
     
         6 . The circuit of  claim 1 , wherein the clamped voltage range has a high voltage limit set lower than the maximum output voltage. 
     
     
         7 . The circuit of  claim 1 , wherein the clamped voltage range has a low voltage limit set higher than the minimum output voltage. 
     
     
         8 . The circuit of  claim 1 , wherein the actual ambient light level detected by the photo sensor is compared to a desired ambient light level and the feedback controller adjusts the dimming control voltage to adjust the level of brightness of the light to cause the actual ambient light level to converge toward the desired ambient light level. 
     
     
         9 . The circuit of  claim 8 , wherein the desired ambient light level is set using a reference voltage controller. 
     
     
         10 . The circuit of  claim 1 , wherein the dimmable driver is a ballast for a fluorescent light. 
     
     
         11 . The circuit of  claim 1 , wherein the dimmable driver is an LED driver for an LED or LED array. 
     
     
         12 . The circuit of  claim 1 , wherein the pair of low voltage control leads connect with conventional violet and gray 0-10V leads associated with the dimmable driver. 
     
     
         13 . The circuit of  claim 1 , wherein the pair of low voltage control leads are connected with and provide the dimming control voltage to a plurality of dimmable drivers. 
     
     
         14 . A method for controlling the dimming level of lights in an interior space, comprising:
 selectively reducing the voltage range of the dimming control voltage to a clamped voltage range that is less than a permissible voltage range;   receiving an input current from one or more dimmable drivers, each of the one or more dimmable drivers electrically coupled to a respective light;   detecting an actual ambient light level in the vicinity of the lights;   comparing the detected actual ambient light level with a desired ambient light level;   setting the dimming control voltage in response to the comparison of the detected actual ambient light level with the desired ambient light level, wherein the dimming control voltage must be within the selectively reduced clamped voltage range; and   providing the dimming control voltage to the one or more dimmable drivers, the dimming control voltage determining the dimming level of the lights.   
     
     
         15 . The method of  claim 14 , wherein even with the maximum dimming of the lights, some light is still emitted from the lights. 
     
     
         16 . The method of  claim 14 , wherein the maximum dimming of the lights causes no light to be emitted from the lights. 
     
     
         17 . The method of  claim 14 , further comprising increasing the dimming control voltage if the detected actual ambient light level is less than the desired ambient light level. 
     
     
         18 . The method of  claim 15 , wherein the clamped voltage range has a high voltage limit set lower than the maximum output voltage and wherein the dimming control voltage is capped at the high voltage limit. 
     
     
         19 . The method of  claim 14 , further comprising decreasing the dimming control voltage if the detected actual ambient light level is greater than the desired ambient light level. 
     
     
         20 . The method of  claim 19 , wherein the clamped voltage range has a low voltage limit set higher than the minimum output voltage and wherein the dimming control voltage is capped at the low voltage limit.