Lighting control system having temperature compensation and trim circuits

• US 7,701,151 B2
• Filed: 10/19/2007
• Issued: 04/20/2010
• Est. Priority Date: 10/19/2007
• Status: Active Grant

• Current Assignee: American Sterilizer Company (Steris Corporation)
• Original Assignee: American Sterilizer Company (Steris Corporation)
• Inventors: Petrucci, James A., Hite, David A., Drabinski, Terry A., Rice, Sheari A.
• Primary Examiner(s): Vo; Tuyet
• Application Number:
  US11/875,083
• Publication Number:
  US 20090102396A1
• Time in Patent Office: 914 Days
• Field of Search: 315/224, 315/225, 315/209.R, 315291-326, 315/185.S, 315/247, 315/246, 345/82, 345/101, 345/102, 345211-214
• US Class Current: 315/309
• CPC Class Codes: H05B 45/00 Circuit arrangements for operating light-emitting diodes [LED]
• CPC Class Codes: H05B 45/28 using temperature feedback
• CPC Class Codes: H05B 45/48 having LEDs organised in strings and incorporating parallel shunting devices
• CPC Class Codes: H05B 45/56 involving measures to prevent abnormal temperature of the LEDs
• CPC Class Codes: H05B 45/58 involving end of life detection of LEDs
• CPC Class Codes: H05B 47/235 with communication between the lamps and a central unit

Abstract

A lighting control system suitable for a surgical lighting device. The lighting control system includes circuitry that compensates for the effects of temperature changes in a lighting device, and that compensates for forward voltage variations among LED lighting modules to provide substantially uniform light output.

Claims

1. A lighting control system for a lighting device, the system comprising:

a primary controller;

a plurality of drive controllers electrically connected with the primary controller;

a plurality of drive outputs electrically connected with a drive controller, each drive controller controlling at least one drive output;

a plurality of LED modules, each LED module electrically connected with a drive output and having a plurality of LEDs, wherein at least one of said plurality of LED modules includes;

a temperature compensation circuit to compensate for effects of temperature changes on a forward voltage associated with the LEDs of the LED module, said temperature compensation circuit reducing the forward voltage as the temperature of the LEDs increases.

2. A lighting control system according to claim 1, wherein said temperature compensation circuit includes:

a resistor network;

a transistor; and

a thermistor.

3. A lighting control system according to claim 1, wherein at least one of said plurality of LED modules includes:

a temperature sensing device for sensing temperature in the vicinity of the LED module.

4. A lighting control system according to claim 1, wherein said primary controller monitors a drive current associated with each drive output in order to determine whether one of said plurality of LED modules has an open circuit failure.

5. A lighting control system according to claim 1, wherein said drive output includes circuitry to determine whether an associated LED module has a short circuit failure.

6. A lighting control system according to claim 1, wherein said primary controller operates in a maintenance mode wherein said plurality of LED modules operate at a low duty cycle.

7. A lighting control system according to claim 1, wherein said primary controller operates in a calibration mode allowing tuning of said plurality of LED modules to a LED drive current within a range from a predetermined target drive current.

8. A lighting control system according to claim 1, wherein said system includes a substrate having a plurality of LED modules located thereon.