Automatic control electroluminescent backlight panel

• US 5,747,938 A
• Filed: 05/22/1995
• Issued: 05/05/1998
• Est. Priority Date: 10/18/1994
• Status: Expired due to Term

• Current Assignee: Intermec IP Corporation (Honeywell International Inc.)
• Original Assignee: Norand Corporation (Baker Hughes Company)
• Inventors: Beard, Paul
• Primary Examiner(s): Pascal, Robert
• Assistant Examiner(s): Philogene, Haissa
• Application Number:
  US08/445,494
• Time in Patent Office: 1,079 Days
• Field of Search: 315/169.3, 315/209 R, 315/226, 315/239, 315/307, 315/169.4, 315/200 R, 315/205, 315/219, 315/224, 315/169.1, 315/155, 315/291, 340/468, 340/461, 340/462, 340/815.01, 345/63, 345/102, 345/207
• US Class Current: 315/169.3
• CPC Class Codes: H02M 3/33576 having at least one active switching element at the secondary side of an isolation transformer
• CPC Class Codes: H02M 7/537 using semiconductor devices only, e.g. single switched pulse inverters
• CPC Class Codes: H05B 44/00 Circuit arrangements for operating electroluminescent light sources for operating light emitting diodes H05B45/00
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

An electroluminescent backlight panel for a video display system is automatically controlled by the varying ambient light levels. A light detector receives the ambient light level and sends a corresponding electrical signal to a microcontroller. The microcontroller controls the driving of the eletroluminescent backlight power supply according to varying ambient light levels until an optimum backlight output is reached. The automatic electroluminescent backlight control system is combined with an efficient power supply unit in order to further reduce battery energy consumption.

Claims

1. An apparatus for automatically controlling the backlighting of a display, comprising:

a backlight for providing a light output for backlighting the display;

a first light detector disposed proximate to said backlight for detecting the light output of said backlight;

a second light detector for detecting the level of ambient light;

a controller operatively connected to said first and second light detectors, said controller for controlling the light output of said backlight based upon the detected light output of said backlight and the detected level of ambient light; and

wherein the light output of said backlight is increased as the level of ambient light decreases and is decreased as the level of ambient light increases.

2. An apparatus as claimed in claim 1, wherein said controller varies the light output of said backlight for conserving battery energy when said backlight is battery powered.

3. An apparatus as claimed in claim 1, wherein said controller includes an analog-to-digital converter for digitizing the level of ambient light.

4. An apparatus as claimed in claim 1, wherein said controller includes an analog-to-digital converter for digitizing the light output provided by said backlight.

5. An apparatus as claimed in claim 1, wherein said controller includes a pulse-width modulator for modulating the light output of said backlight.

6. An apparatus as claimed in claim 1, wherein said backlight is an electroluminescent device.

7. An apparatus as claimed in claim 1, wherein said backlight is an electroluminescent panel.

8. A method for reducing the amount of energy consumed by a backlight for a video display system comprising the steps of:

(a) converting battery energy to electroluminescent panel energy;

(b) charging an electroluminescent panel with the electroluminescent panel energy such that a first portion of the electroluminescent panel energy is converted to light energy and a second portion of the electroluminescent panel energy is stored therein;

(c) converting the stored electroluminescent panel energy into battery energy by discharging the electroluminescent panel; and

(d) recharging a battery with the thus converted battery energy.

9. The method of claim 8 wherein the charging of the electroluminescent panel is controlled according to varying ambient light levels.

10. The method of claim 8 wherein the discharging of the electroluminescent panel is controlled according to varying ambient light levels.

11. The method of claim 8 wherein the charging of the electroluminescent panel is controlled according to varying ambient light levels and the electroluminescent panel output level.

12. The method of claim 8 wherein the discharging of the electroluminescent panel is controlled according to varying ambient light levels.