Backlight unit, method of operating the same and liquid crystal display device having the same

• US 8,736,196 B2
• Filed: 07/15/2009
• Issued: 05/27/2014
• Est. Priority Date: 10/09/2008
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.), Korea Taiyo Yuden Co., Ltd. (Taiyo Yuden Co)
• Original Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.), Korea Taiyo Yuden Co., Ltd. (Taiyo Yuden Co)
• Inventors: Lee, Yun-Gun, Kang, Moon-Shik, Jang, Ki-Bok, Park, Sung-Kyu, Seo, Hyun-Ho
• Primary Examiner(s): Taningco, Alexander H
• Assistant Examiner(s): LO, CHRISTOPHER KWOK YEUNG
• Application Number:
  US12/503,303
• Publication Number:
  US 20100091220A1
• Time in Patent Office: 1,777 Days
• Field of Search: 315/127, 315/175, 315/128, 315/119, 315/224, 315/225, 315/291, 315/314, 315/57, 315307-308, 315/293, 315/294, 315/295, 315/297, 315/194, 315/209.R, 315/247, 315/246, 315/DIG.2, 315/DIG.5, 315/DIG.7, 363 16- 20, 363 24- 26, 363/97, 363/98, 363/95, 363/131, 363/132
• US Class Current: 315/308
• CPC Class Codes: G02F 1/133604 with lamps
• CPC Class Codes: G09G 3/342 using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines
• CPC Class Codes: H05B 41/2855 against abnormal lamp operating conditions

Abstract

A backlight unit includes; a light source, an inverter which provides the light source with an input voltage, and a printed circuit board (“PCB”) connected to the light source, wherein the PCB includes a protection circuit which detects an open-lamp-protection voltage which varies according to a change of the input voltage and changes a reference voltage according to the change of the input voltage, wherein the protection circuit turns off the inverter when the detected open-lamp-protection voltage is higher than the changed reference voltage.

Claims

1. A backlight unit comprising:

a light source;

an inverter which provides the light source with an input voltage; and

a printed circuit board connected to the light source,

wherein the printed circuit board includes a protection circuit which detects an open-lamp-protection voltage which varies according to a change of the input voltage, and changes a reference voltage according to the change of the input voltage, and

wherein the protection circuit turns off the inverter when the detected open-lamp-protection voltage is higher than the changed reference voltage by comparing the detected open-lamp-protection voltage with the changed reference voltage, and

wherein the protection circuit includes;

a voltage detection part which distributes the input voltage applied to the light source by using a capacitor to detect the open-lamp-protection voltage;

a reference voltage changing part which distributes the input voltage by using the capacitor to change the reference voltage according to the change of the input voltage; and

a protection-control signal generation part which compares the open-lamp-protection voltage with the reference voltage and generates a protection-control signal Which controls the operation of the inverter.

2. The backlight unit of claim 1, wherein the input voltage is a local dimming voltage.

3. The backlight unit of claim 1, wherein the capacitor is a pattern capacitor comprising patterns disposed on at least one of an upper surface and a lower surface of the printed circuit board.

4. The backlight unit of claim 1, wherein the protection-control signal generation part includes a comparator which compares the open-lamp-protection voltage with the reference voltage.

5. The backlight unit of claim 1, wherein a difference between the open-lamp-protection voltage and the reference voltage is in a range of about 2 Volts to about 11 Volts.

6. The backlight unit of claim 1, wherein the printed circuit board further includes a plurality of balance capacitors which control the input voltage to substantially uniformly maintain a balance of electrical currents applied to the light source.

7. The backlight unit of claim 1, wherein the printed circuit board further includes a plurality of balance inductors which control the input voltage to substantially uniformly maintain a balance of electrical currents applied to the light source.

8. The backlight unit of claim 1, further comprising a feedback control part which generates a feedback signal which controls the voltage level of the input voltage according to whether the light source is turned on normally.

9. The backlight unit of claim 1, wherein the light source is one of a plurality of light-emitting diodes and at least one cold cathode fluorescent lamp.

10. A method of operating a backlight unit, the method comprising:

applying an input voltage to a light source;

detecting an open-lamp-protection voltage using a capacitor to distribute the input voltage;

changing a reference voltage according to the change of the input voltage using the capacitor to distribute the input voltage;

comparing the detected open-lamp-protection voltage with the changed reference voltage; and

turning off the input voltage applied to the light source when the detected open-lamp-protection voltage is higher than the changed reference voltage by comparing the detected open-lamp-protection voltage with the changed reference voltage.

11. The method of claim 10, wherein turning off the input voltage includes:

changing the reference voltage according to a change of the input voltage;

comparing the open-lamp-protection voltage with the changed reference voltage; and

turning off the input voltage applied to the light source when the detected open-lamp-protection voltage is higher than the changed reference voltage, or maintaining the input voltage applied to the light source when the detected open-lamp-protection voltage is substantially the same as or lower than the changed reference voltage.

12. The method of claim 11, wherein the input voltage is turned off when the detected open-lamp-protection voltage is higher than the changed reference voltage for about 2 seconds or longer.

13. The method of claim 11, wherein a difference between the open-lamp-protection voltage and the reference voltage is in a range of about 2 Volts to about 11 volts.

14. A liquid crystal display device comprising:

an liquid crystal display panel which displays an image; and

a backlight unit providing the liquid crystal display panel with light, the backlight unit including;

a light source;

an inverter which provides the light source with an input voltage; and

a printed circuit board connected to the light source, the printed circuit board including a protection circuit which detects an open-lamp-protection voltage which varies according to a change of the input voltage and changes a reference voltage according to the change of the input voltage, and the protection circuit turns off the inverter when the detected open-lamp-protection voltage is higher than the changed reference voltage by comparing the detected open-lamp-protection voltage with the changed reference voltage, and

wherein the protection circuit includes;

a voltage detection part which distributes the input voltage applied to the light source by using a capacitor to detect the open-lamp-protection voltage;

a reference voltage changing part which distributes the input voltage by using the capacitor to change the reference voltage according to the change of the input voltage; and

a protection-control signal generation part which compares the open-lamp-protection voltage with the reference voltage and generates a protection-control signal which controls the operation of the inverter.

15. The liquid crystal display device of claim 14, wherein the input voltage is a local dimming voltage.

16. The liquid crystal display device of claim 14, wherein the capacitor is a pattern capacitor comprising patterns disposed on at least one of an upper surface and a lower surface of the printed circuit board.

17. The liquid crystal display device of claim 14, wherein the printed circuit board further includes a plurality of balance capacitors which control the input voltage to uniformly maintain a balance of electrical currents applied to the light source.

18. The liquid crystal display device of claim 14, wherein the printed circuit board further includes a plurality of balance inductors which control the input voltage to substantially uniformly maintain a balance of electrical currents applied to the light source.

19. The liquid crystal display device of claim 14, further comprising a feedback control part which generates a feedback signal which controls the voltage level of the input voltage according to whether the light source is turned on normally.

20. The liquid crystal display device of claim 14, wherein the light source is one of a plurality of light-emitting diodes and at least one cold cathode fluorescent lamp.