Apparatus and method for compensating for reduced light output of a solid-state light source having a lumen depreciation characteristic over its operational life
First Claim
1. A method for compensating for loss in light output of an LED adapted to illuminate a target area comprising:
- a. characterizing a lumen depreciation characteristic of said LED from (i) empirical testing, (ii) a priori knowledge, (iii) manufacturing data, or some combination of (i)-(iii);
b. monitoring illumination at the target area when power is provided to the LED;
c. generating a signal when monitored illumination drops below a predetermined threshold; and
d. increasing power provided to the LED by a predetermined increment based, at least in part, on the lumen depreciation characteristic of the LED.
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Abstract
A method, apparatus, and system for compensating for lamp lumen depreciation. The method includes operating the lamp under rated wattage for a period towards the first part of operating life of the lamp. Operating wattage is increased at one or more later times. Energy savings are realized. The increases also restore at least some light lost by lamp lumen depreciation. The apparatus uses a timer to track operating time of the lamp. A few wattage changes made at spaced apart times can be made in a number of ways, including changing capacitance to the lamp, or using different taps on the lamp ballast. In one aspect the invention pertains to solid state sources. The invention can pertain to a variety of applications including wide area lighting, indoor lighting, pathway lighting, parking lot lighting, street lighting, under-counter or -cabinet lighting, and others.
109 Citations
20 Claims
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1. A method for compensating for loss in light output of an LED adapted to illuminate a target area comprising:
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a. characterizing a lumen depreciation characteristic of said LED from (i) empirical testing, (ii) a priori knowledge, (iii) manufacturing data, or some combination of (i)-(iii); b. monitoring illumination at the target area when power is provided to the LED; c. generating a signal when monitored illumination drops below a predetermined threshold; and d. increasing power provided to the LED by a predetermined increment based, at least in part, on the lumen depreciation characteristic of the LED. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of driving an array of solid state light sources elevated on an elevating structure relative a wide area target to be illuminated, each solid state light source having a lamp lumen depreciation characteristic which reduces lumen output of the light source over operating time and a lumen output that is at least partially dependent on drive current comprising:
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a. identifying a minimum desired lumen output, a light distribution output, and aiming direction for each solid state light source and the array of solid state light sources relative to the wide area target; b. predicting one or more discrete operating times to adjust the drive current at least partially from the lumen depreciation characteristic; c. determining a compensation adjustment to the drive current such that the lumen output of the solid state light sources will return at or near the minimum desired lumen output; and d. adjusting the drive current at each predicted operating time with the compensation adjustment. - View Dependent Claims (12, 13, 14, 15)
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16. A system for illuminating a wide area target comprising:
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a. a plurality of elevating structure positioned at or around the target area; b. an array of luminaires on each elevating structure aimed at the target area, each luminaire comprising a housing and a plurality of light sources, each light source having a lumen output and a lumen depreciation characteristic; c. a first circuit operatively connecting each elevating structure to an electrical power source; d. a second circuit operatively connected between the first circuit and each array, the second circuit providing adjustable electrical power to each light source in the array correlated to a desired lumen output at least partially based on compensation for the lumen depreciation characteristic. - View Dependent Claims (17, 18, 19, 20)
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Specification