Lighting control method having a light output ramping function

• US 7,812,551 B2
• Filed: 03/25/2009
• Issued: 10/12/2010
• Est. Priority Date: 10/19/2007
• Status: Active Grant

• Current Assignee: American Sterilizer Company (Steris Corporation)
• Original Assignee: American Sterilizer Company (Steris Corporation)
• Inventors: Hite, David A., Rice, Sheari A.
• Primary Examiner(s): Vo; Tuyet Thi
• Application Number:
  US12/410,494
• Publication Number:
  US 20090179595A1
• Time in Patent Office: 566 Days
• Field of Search: 315/247, 315/246, 315/224, 315/225, 315/209.R, 315/185.S, 315/291, 315/297, 315307-326, 345/82, 345/102, 345/101, 345211-214
• US Class Current: 315/291
• CPC Class Codes: H05B 45/00 Circuit arrangements for operating light-emitting diodes [LED]
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/18 using temperature feedback
• CPC Class Codes: H05B 45/395 Linear regulators
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

A lighting control method for maintaining substantially uniform light output from an LED light source during a warm-up period. A ramp duty cycle function gradually increases the duty cycle of an LED drive output signal during the warm-up period of the LED light source.

Claims

1. A lighting control method for controlling an LED light source during an LED warm-up mode, the method comprising:

(a) retrieving a pre-stored setpoint duty cycle corresponding to a light intensity level;

(b) operating the LED light source during a first time interval at an operating duty cycle equal to the setpoint duty cycle minus a pre-stored duty cycle trim value;

(c) setting a duty cycle ramp value equal to a pre-stored duty cycle step value;

(d) operating the LED light source for a time interval at an operating duty cycle equal to the setpoint duty cycle minus the duty cycle trim value plus the duty cycle ramp value; and

determining whether (1) a ramp-up time has elapsed, (2) the operating duty cycle equals the setpoint duty cycle, or (3) a new light intensity level has been selected, and ending the LED warm-up mode if any one of (1), (2) or (3) has occurred, and if (1), (2) and (3) have not occurred, then increasing the duty cycle ramp value by the duty cycle step value, and returning to step (d).

2. A lighting control method according to claim 1, wherein after the first time interval has elapsed, determining whether a ramp duty cycle function has been enabled, wherein if the ramp duty cycle function has not been enabled, then ending the LED warm-up mode.

3. A lighting control method according to claim 1, wherein said warm-up mode is initiated only if ambient temperature of electronics for the LED light source is below a predetermined setpoint temperature.

4. A lighting control method for controlling an LED light source during an LED warm-up mode, the method comprising:

(a) establishing a light intensity level;

(b) retrieving a pre-stored setpoint duty cycle corresponding to the light intensity level;

(c) retrieving a pre-stored duty cycle trim value;

(d) operating the LED light source during a first time interval at an operating duty cycle equal to the setpoint duty cycle minus the duty cycle trim value;

(e) retrieving a pre-stored ramp-up time;

(f) retrieving a pre-stored duty cycle step value;

(g) setting a duty cycle ramp value equal to the pre-stored duty cycle step value;

(h) operating the LED light source for a time interval at an operating duty cycle equal to the setpoint duty cycle minus the duty cycle trim value plus the duty cycle ramp value;

(i) determining whether a predetermined condition has been satisfied;

(j) if the predetermined condition has been satisfied, then increasing the duty cycle ramp value by the duty cycle step value and returning to step (h); and

(k) if the predetermined condition has not been satisfied, then ending the warm-up-mode.

5. A lighting control method according to claim 4, wherein said predetermined condition is whether:

(1) the ramp-up time has not elapsed, (2) the operating duty cycle does not equal the setpoint duty cycle, and (3) a new light intensity level has not been selected.

6. A lighting control method according to claim 4, wherein after the first time interval has elapsed, determining whether a ramp duty cycle function has been enabled, wherein if the ramp duty cycle function has not been enabled, then ending the LED warm-up mode.

7. A lighting control method according to claim 4, wherein said warm-up mode is initiated only if ambient temperature of electronics for the LED light source is below a predetermined setpoint temperature.