Method and apparatus for a pulsed L.E.D. illumination source

• US 20030095406A1
• Filed: 11/18/2002
• Published: 05/22/2003
• Est. Priority Date: 03/19/1998
• Status: Active Grant

• Current Assignee: Lemaire Illumination Technologies LLC
• Original Assignee: PPT Vision, Inc. (Datalogic S.p.A.)
• Inventors: Lemaire, Charles A., Bourn, Charles T., Lebens, Gary A.
• Granted Patent: US 6,808,287 B2
• Time in Patent Office: Days
• US Class Current: 362/231
• CPC Class Codes: F21L 4/027 the light sources being a LED
• CPC Class Codes: F21Y 2115/10 Light-emitting diodes [LED]
• CPC Class Codes: H04B 10/502 LED transmitters
• CPC Class Codes: H04B 10/564 Power control
• CPC Class Codes: H04N 23/74 by influencing the scene brightness using illuminating means
• CPC Class Codes: H05B 45/12 using optical feedback
• CPC Class Codes: H05B 45/20 Controlling the colour of the light
• CPC Class Codes: H05B 45/22 using optical feedback
• CPC Class Codes: H05B 45/32 Pulse-control circuits
• CPC Class Codes: H05B 45/395 Linear regulators
• CPC Class Codes: H05B 45/50 responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]
• CPC Class Codes: Y10S 362/80 Light emitting diode
• CPC Class Codes: Y10S 362/802 Position or condition responsive switch

Abstract

Improved method and apparatus for hand-held portable illumination. A flashlight and corresponding method are described. The flashlight includes a housing, a plurality of LEDs, and an electrical circuit that selectively applies power from the DC voltage source to the LED units, wherein the flashlight is suitable for handheld portable operation by a user. In one embodiment, the first electrical circuit further includes a control circuit for maintaining a predetermined light output level of the LED units as a charge on a battery varies. In another embodiment, the control circuit maintains an average predetermined light output level of the LED units as the charge on the battery cell varies by changing a pulse width or frequency as the charge on the battery cell varies to maintain a given average light output. Another aspect provides an illumination source that includes a light-emitting diode (LED) housing including one or more LEDs, and a control circuit that selectively applies power from a source of electric power to the LEDs, the control circuit substantially maintaining a light output characteristic of the LEDs as a voltage of the voltage source varies over a range that would otherwise vary the light output characteristic. Still another aspect provides an illumination source including a light-emitting diode (LED) housing including one or more LEDs; and a control circuit that selectively applies power from a source of electric power to the LEDs, thus maintaining or controlling a light output color spectrum of the LEDs.

Claims

1. A method of providing general-purpose illumination of such compact size and low weight as to be suitable for single-handed portable operation by a user, comprising the steps of:

(a) providing one or more first LED units that each emit light;

(b) selectively applying pulsed power from a DC voltage source to the LED units; and

(c) maintaining a predetermined light output level of the LED units as a charge on the DC voltage source varies by controlling the step (b).

2. The method of claim 1, wherein the step of maintaining maintains an average predetermined light output level of the LED units as the charge on the battery cell varies by increasing a pulse width as the charge on the battery cell decreases.

3. The method of claim 1, wherein the step of maintaining maintains an average predetermined light output level of the LED units as the charge on the battery cell varies by increasing a pulse energy as the charge on the battery cell decreases.

4. The method of claim 1, wherein the step of maintaining maintains an average predetermined light output level of the LED units as the charge on the battery cell varies by increasing a pulse frequency as the charge on the battery cell decreases.

5. The method of claim 1, wherein the step of maintaining maintains an average predetermined light output level of the LED units by sensing a battery voltage and adjusting a pulse width to the LED units based on the measured voltage to maintain the average light output at the predetermined level.

6. The method of claim 1, wherein the step of maintaining maintains an average predetermined light output level of the LED units by sensing a battery voltage and adjusting a pulse energy to the LED units based on the measured voltage to maintain the average light output at the predetermined level.

7. The method of claim 1, wherein the step of maintaining maintains an average predetermined light output level of the LED units by sensing a battery voltage and adjusting a pulse frequency to the LED units based on the measured voltage to maintain the average light output at the predetermined level.

8. The method of claim 1, wherein the step of maintaining maintains an average predetermined light output level of the LED units by sensing a light output and adjusting a pulse width to the LED units based on the measured voltage to maintain the average light output at the predetermined level.

9. The method of claim 1, wherein the step of maintaining maintains an average predetermined light output level of the LED units by sensing a light output and adjusting a pulse energy to the LED units based on the measured voltage to maintain the average light output at the predetermined level.

10. The method of claim 1, wherein the step of maintaining maintains an average predetermined light output level of the LED units by sensing a light output and adjusting a pulse frequency to the LED units based on the measured voltage to maintain the average light output at the predetermined level.

11. A pulsed LED illumination source, comprising:

one or more LEDs; and

a control circuit that is operatively coupled to the one or more LEDs and that selectively applies power pulses from a DC voltage source to the LEDs, the control circuit substantially maintaining an average light output characteristic of the LEDs as a voltage of the voltage source varies over a range that would otherwise vary the light output characteristic by adjusting the pulses.

12. The illumination source of claim 11, wherein the light output characteristic that is maintained is light output intensity.

13. The illumination source of claim 12, wherein the control circuit maintains the light output intensity of the LED units as the voltage of the DC voltage source varies by increasing a pulse width as the voltage of the DC voltage source decreases.

14. The illumination source of claim 12, wherein the control circuit maintains the light output intensity of the LED units as the voltage of the DC voltage source varies by increasing a pulse energy as the voltage of the DC voltage source decreases.

15. The illumination source of claim 12, wherein the control circuit maintains the light output intensity of the LED units as the voltage of the DC voltage source varies by increasing a pulse frequency as the voltage of the DC voltage source decreases.

16. The illumination source of claim 12, wherein the control circuit maintains an average predetermined light output level of the LED units by sensing a voltage and adjusting a pulse width to maintain the average light output at the predetermined level.

17. The illumination source of claim 12, wherein the control circuit maintains an average predetermined light output level of the LED units by sensing a voltage and adjusting a pulse energy to maintain the average light output at the predetermined level.

18. The illumination source of claim 12, wherein the control circuit maintains an average predetermined light output level of the LED units by sensing a voltage and adjusting a pulse frequency to maintain the average light output at the predetermined level.

19. A battery-powered portable pulsed LED illumination source comprising:

one or more light-emitting devices (LEDs);

a switch; and

control means for maintaining a substantially constant perceived light output, the control means operatively coupled to a battery, the LEDs, and the switch, wherein the control means drives the LEDs with electrical pulses at a frequency high enough that light produced by the LEDs has an appearance to a human user of being continuous rather than pulsed, and wherein the LEDs have proportion of on-time that increases as remaining battery power decreases.

20. The illumination source of claim 19, wherein the control means further comprise:

feedback means for controlling the pulses so that light intensity produced by the LEDs, as perceived by the human user, is substantially constant across a greater range of battery power than a corresponding range for which light intensity is equally constant without the feedback circuit.