Flat panel display having a backlight module

• US 20080191639A1
• Filed: 11/14/2006
• Published: 08/14/2008
• Est. Priority Date: 11/15/2005
• Status: Abandoned Application

• Current Assignee: InnoLux Corporation
• Original Assignee: Chi Mei Optoelectronics (InnoLux Corporation)
• Inventors: Chen, Shih-Ming, Lee, Yong-Long
• Application Number:
  US11/599,185
• Publication Number:
  US 20080191639A1
• Time in Patent Office: Days
• US Class Current: 315/287
• CPC Class Codes: H05B 41/2822 using specially adapted components in the load circuit, e.g. feed-back transformers, piezoelectric transformers; using specially adapted load circuit configurations

Abstract

A backlight module that includes a lamp and a single side driving inverter that is coupled to one end of the lamp. The single side driving inverter is configured to control an operating current of the lamp to be within 80% to 100% of a saturation luminance current. The lamp has a characteristic such that when the operating current is lower than the saturation luminance current, the lamp luminance increases as the operating current increases, and when the operating current is substantially equal to or higher than the saturation luminance current, the lamp luminance does not increase as the operating current increases.

Claims

1. A backlight module, comprising:

a lamp; and

a single side driving inverter that is coupled to one end of the lamp and configured to control an operating current of the lamp to be within 80% to 100% of a saturation luminance current,

wherein the lamp has a characteristic such that when the operating current is lower than the saturation luminance current, the lamp luminance increases as the operating current increases, and when the operating current is substantially equal to or higher than the saturation luminance current, the lamp luminance does not increase as the operating current increases.

2. The backlight module of claim 1, wherein the lamp comprises cold cathode fluorescent lamp.

3. The backlight module of claim 1, wherein the single side driving inverter is configured to adjust a duty cycle of the operating current to reduce the luminance of the lamp.

4. The backlight module of claim 1, further comprising additional lamps, the single side driving inverter configured to control operating currents of each of the additional lamps to be within 80% to 100% of the saturation luminance current, wherein the single side driving inverter is configured to alternate the operating currents between a higher level and a lower level such that the lamps alternate between a brighter state and a darker state for a user-selectable maximum luminance level of the backlight module.

5. The backlight module of claim 4 wherein the single side driving inverter is configured to alternate the operating currents between a higher level and a lower level such that the lamps alternate between a brighter state and a darker state for an entire range of user-selectable luminance levels of the backlight module.

6. The backlight module of claim 1 wherein the driver is configured to control the operating current to be at a level such that more than 80% of the current provided to the one end of the lamp flows in the lamp to another end of the lamp.

7. A liquid crystal display television comprising the backlight module of claim 1.

8. An apparatus comprising:

a backlight module for a flat panel display, the backlight module comprising;

a fluorescent lamp having a current-luminance characteristic such that when a current lower than a saturation level is provided to the lamp, the luminance of the lamp increases as the current increases, and the lamp luminance saturates when the current is equal to or higher than the saturation level; and

a driver configured to drive the lamp for at least a portion of the time using a current that is higher than 80% of the saturation level.

9. The apparatus of claim 8 wherein the driver is configured to drive the lamp using a current that alternates between a higher level and a lower level so that the lamp alternates between a brighter state and a darker state, the current being higher than 80% of the saturation level in the higher level and less than 80% of the saturation level in the lower level.

10. The apparatus of claim 9 wherein the driver adjusts the ratio of the durations of the higher and lower levels to adjust the luminance of the backlight module.

11. The apparatus of claim 9 wherein the driver adjusts the current level in the higher level and/or the lower level to adjust the luminance of the backlight module.

12. The apparatus of claim 8 wherein the driver comprises a single-side-driving inverter that is coupled to a first end of the lamp and provides the current to the lamp, a second end of the lamp being electrically coupled to a ground voltage.

13. The apparatus of claim 8 wherein the saturation level is between 5 to 20 mA.

14. The apparatus of claim 8 wherein the lamp has a voltage-current characteristic such that the current flowing in the lamp decreases as a voltage applied to the lamp increases when the current is lower than the saturation level.

15. An apparatus comprising:

a backlight module having a user-selectable maximum luminance, the backlight module comprising;

one or more fluorescent lamps having current-luminance characteristics such that the backlight module has a luminance higher than the user-selectable maximum luminance when a continuous current higher than 80% of a saturation level is provided to each lamp,

the saturation level being defined such that when a current lower than the saturation level is provided to the lamp, the luminance of the lamp increases as the current increases, and the lamp luminance saturates when the current is equal to or higher than the saturation level; and

a driver configured to drive each of the one or more lamps using a current that alternates between a higher level and a lower level such that the lamp alternates between a brighter state and a darker state to cause the backlight module to have the user-selectable maximum luminance, the current being higher than 80% of the saturation level during the higher level and less than 80% of the saturation level during the lower level.

16. The apparatus of claim 15 wherein the driver comprises a single-side-driving inverter that is coupled to a first end of each lamp and provides the current to the lamp, a second end of the lamp being electrically coupled to a ground voltage.

17. A flat panel display having a diagonal size larger than 37 inches, comprising:

a fluorescent lamp having a first end and a second end for providing light that is modulated by a plurality of pixel circuits of the display; and

a single side driving inverter configured to drive the lamp by providing an AC voltage and an AC current to the first end of the lamp, the single side driving inverter configured to control the AC voltage and the AC current to have levels such that more than 80% of the AC current provided to the first end flows in the lamp to the second end.

18. The flat panel display of claim 17 wherein the single side driving inverter is configured to control the AC voltage and the AC current such that less than 20% of the AC current provided to the first end of the lamp forms leakage currents that flow to ground through stray capacitances.

19. The flat panel display of claim 17 wherein the lamp comprises a cold cathode fluorescent lamp.

20. The flat panel display of claim 17 wherein the single side driving inverter is configured to control the AC current to have a root-mean-square (rms) value higher than 80% of a saturation level for at least a portion of the time,

the lamp having a luminance-current characteristic such that when an AC current having an rms value lower than the saturation level is provided to the lamp, the luminance of the lamp increases as the AC current increases, and the lamp luminance saturates when the AC current is equal to or higher than the saturation level.

21. A method comprising:

driving a fluorescent lamp of a backlight module of a flat panel display by providing to the lamp a current higher than 80% of a saturation level of the lamp for at least a portion of the time,

the lamp having a luminance-current characteristic such that when a current lower than the saturation level is provided to the lamp, the luminance of the lamp increases as the current increases, and the lamp luminance saturates when the current is equal to or higher than the saturation level.

22. The method of claim 21 wherein driving the lamp comprises using a single side driving inverter to drive the lamp.

23. The method of claim 21 wherein providing the current to the lamp comprises providing an AC current that alternates between a first level higher than 80% of the saturation level and a second level lower than 80% of the saturation level to cause the lamp to alternate between a brighter level and a darker level.

24. The method of claim 23, further comprising adjusting the ratio of the durations of the first and second levels to adjust the luminance of the backlight module.

25. The method of claim 21, further comprising adjusting the current level provided to the lamp to adjust the luminance of the backlight module.

26. The method of claim 21 wherein driving the lamp comprises driving the lamp in a negative resistance region in which increasing the voltage across the lamp results in a reduction of the current flowing in the lamp.

27. The method of claim 21, further comprising modulating the light from the backlight module using pixel circuits to form an image.

28. A method comprising:

driving a fluorescent lamp of a backlight module of a flat panel display having a diagonal size larger than 37 inches using single side driving by providing an AC voltage and an AC current to a first end of the lamp, the AC voltage and the AC current being selected such that more than 80% of the AC current provided to the first end flows in the lamp to a second end of the lamp.

29. The method of claim 28 wherein the AC current is higher than 80% of a saturation level for at least a portion of the time,

the lamp having a luminance-current characteristic such that when an AC current lower than the saturation level is provided to the lamp, the luminance of the lamp increases as the AC current increases, and the lamp luminance saturates when the AC current is equal to or higher than the saturation level.

30. The method of claim 28 wherein providing the AC current to the lamp comprises providing an AC current that alternates between a first level and a second level so that the lamp alternates between a brighter state and a darker state, the first level being higher than 80% of the saturation level, the second level being lower than 80% of the saturation level.

31. The method of claim 30, further comprising adjusting the ratio of the durations of the first and second levels to adjust the luminance of the backlight module.