Backlight driving apparatus of liquid crystal display and method for driving backlight driving apparatus

• US 7,589,479 B2
• Filed: 12/28/2006
• Issued: 09/15/2009
• Est. Priority Date: 06/07/2006
• Status: Active Grant

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Display Co., Ltd.
• Inventors: Kim, Byoung Chul
• Primary Examiner(s): Owens; Douglas W
• Assistant Examiner(s): Vu; Jimmy T
• Application Number:
  US11/646,495
• Publication Number:
  US 20070285029A1
• Time in Patent Office: 992 Days
• Field of Search: 315/287, 315/209.PZ, 315/276, 315/291, 315/299, 315/244, 315/245, 315/291.307, 315/361, 3151691-1693, 345/77, 345/87, 345/102, 345/204
• US Class Current: 315/291
• CPC Class Codes: H05B 41/2853 against abnormal power supply conditions

Abstract

A backlight driving apparatus for a liquid crystal display device includes a light source, an AC driver for supplying a high voltage AC power to turn on the light source, and a protection circuit electrically connected to the AC driver responsive to an input voltage lower than a reference voltage for stopping the driving of the AC driver.

Claims

1. A backlight driving apparatus of a liquid crystal display, comprising:

a light source that emits light;

an AC driver for supplying AC power of a high voltage so that the light source emits light; and

a protection circuit electrically connected to the AC driver, for determining whether an input voltage applied to the AC driver is lower than a predetermined voltage and stopping the driving of the AC driver,

wherein the protection circuit comprises;

a reference voltage setting unit for setting a reference voltage of a predetermined level;

one or more resistors for dividing the input voltage applied to the AC driver in order to form a comparison voltage; and

a comparator having two input terminals connected to an output terminal of the reference voltage setting unit and the one or more resistors, respectively, wherein the comparator compares the reference voltage and the comparison voltage received via the one or more resistors and outputs a control voltage for the driving of the AC driver.

2. The backlight driving apparatus of claim 1, wherein the reference voltage setting unit comprises a zener diode.

3. The backlight driving apparatus of claim 1, wherein when the comparison voltage is higher than the reference voltage, the comparator outputs the control voltage as a high level and drives the AC driver in a normal state.

4. The backlight driving apparatus of claim 3, wherein the control voltage is higher than the comparison voltage.

5. The backlight driving apparatus of claim 1, wherein when the comparison voltage is lower than the reference voltage, the comparator outputs the control voltage as a low level and shuts down the AC driver.

6. The backlight driving apparatus of claim 5, wherein the control voltage is lower than the comparison voltage.

7. The backlight driving apparatus of claim 5, wherein the control voltage is a ground voltage.

8. The backlight driving apparatus of claim 1, wherein the comparator is an operational amplifier.

9. The backlight driving apparatus of claim 1, wherein the AC driver comprises:

a DC/AC converter for converting a DC input voltage into an AC voltage; and

a transformer for boosting the AC voltage converted through the DC/AC converter to a predetermined level.

10. The backlight driving apparatus of claim 1, wherein the light source is a Cold Cathode Fluorescent Lamp (EEFL).

11. The backlight driving apparatus of claim 1, wherein the light source is an External Electrode Fluorescent Lamp (EEFL).

12. A backlight driving apparatus of a liquid crystal display, comprising:

a light-emitting diode (LED) that emits light;

a DC driver for supplying DC power of a high voltage so that the LED emits light; and

a protection circuit electrically connected to the DC driver, for determining whether an input voltage applied to the DC driver is lower than a predetermined voltage and stopping the driving of the DC driver,

wherein the protection circuit comprises;

a reference voltage setting unit for setting a reference voltage of a predetermined level;

one or more resistors for dividing the input voltage applied to the DC driver in order to form a comparison voltage; and

a comparator having two input terminals connected to an output terminal of the reference voltage setting unit and the one or more resistors, respectively, wherein the comparator compares the reference voltage and the comparison voltage received via the one or more resistors and outputs a control voltage for the driving of the DC driver.

13. The backlight driving apparatus of claim 12, wherein the reference voltage setting unit comprises a zener diode.

14. The backlight driving apparatus of claim 12, wherein when the comparison voltage is higher than the reference voltage, the comparator outputs the control voltage as a high level and drives the DC driver in a normal state.

15. The backlight driving apparatus of claim 14, wherein the control voltage is higher than the comparison voltage.

16. The backlight driving apparatus of claim 12, wherein when the comparison voltage is lower than the reference voltage, the comparator outputs the control voltage as a low level and shuts down the DC driver.

17. The backlight driving apparatus of claim 16, wherein the control voltage is lower than the comparison voltage.

18. The backlight driving apparatus of claim 16, wherein the control voltage is a ground voltage.

19. The backlight driving apparatus of claim 12, wherein the comparator is an operational amplifier.

20. The backlight driving apparatus of claim 12, wherein the DC driver comprises:

a pulse width modulation signal providing unit for transforming a DC input voltage into a pulse width modulation signal and outputting the transformed pulse width modulation signal; and

a static voltage providing unit for transforming the transformed pulse width modulation signal into a constant level and sproviding the transformed signal.