Apparatus and method for compensating for reduced light output of a solid-state light source having a lumen depreciation characteristic over its operational life

• US 8,508,152 B1
• Filed: 04/22/2011
• Issued: 08/13/2013
• Est. Priority Date: 02/24/2004
• Status: Active Grant

• Current Assignee: Musco Corporation
• Original Assignee: Musco Corporation
• Inventors: Gordin, Myron, Young, Garrett J., Boyle, Timothy J.
• Primary Examiner(s): A, Minh D
• Application Number:
  US13/092,664
• Time in Patent Office: 844 Days
• Field of Search: 315/312, 315/291, 315/307, 315/200.R, 315/209.R
• US Class Current: 315/291
• CPC Class Codes: H05B 41/38 Controlling the intensity of light
• CPC Class Codes: H05B 41/40 discontinuously
• CPC Class Codes: H05B 45/14 using electrical feedback from LEDs or from LED modules
• CPC Class Codes: H05B 45/58 involving end of life detection of LEDs

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.

Claims

1. A method of adjusting a drive current to at least one solid-state light source which exhibits a lamp lumen depreciation characteristic wherein the at least one solid-state light source has a lumen output response to a range of applied drive currents comprising:

a. identifying a first and second lumen output level;

b. approximating an operating time at which the solid-state light source will depreciate in lumen output to the identified first lumen level;

c. approximating a necessary adjustment to the drive current which will result in the lumen output of the solid-state light source reaching to approximately the identified second lumen level;

d. modifying the drive current by the approximated adjustment at the approximated time.

2. An apparatus for providing approximately constant lumen output from at least one solid state light source which exhibits a lumen depreciation characteristic comprising:

a. at least one solid state light source which has a lumen output which varies with changes in drive current and which experiences lumen depression;

b. a timer which monitors the operating time of the at least one solid state light source and which produces a signal at pre-determined operating times;

c. means for determining said operating times, at least in part, from known lumen depreciation behavior of the at least one solid state light source;

d. an actuator adapted to increase the drive current to the at least one solid state light source so to compensate for said lumen depreciation, the actuator in operative communication to receive the signal from the timer.

3. The apparatus of claim 2 wherein the timer comprises an electronic device.

4. The apparatus of claim 3 wherein the electronic device comprises an electronic controller, computer, microprocessor, or electronic timer.

5. The apparatus of claim 2 wherein the actuator comprises an electronic device.

6. The apparatus of claim 5 wherein the electronic device comprises an electronic switching component.

7. The apparatus of claim 6 wherein the electronic switching component comprises an electronic relay, contactor, relay energizing contact, or latch relay.