Lamp driving device for liquid crystal display device

• US 20050128377A1
• Filed: 12/14/2004
• Published: 06/16/2005
• Est. Priority Date: 12/16/2003
• Status: Active Grant

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Philips LCD Company Limited (LG Display Co., Ltd.)
• Inventors: Lee, Kang Ju, Park, Sin Kyun
• Granted Patent: US 7,427,977 B2
• Time in Patent Office: Days
• US Class Current: 349/61
• CPC Class Codes: G02F 1/133604 with lamps
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers

Abstract

A lamp driving device for driving a plurality of lamps in a liquid crystal display device and a liquid crystal display device using a lamp driving device are provided. The lamp driving device includes an inverter substrate, a plurality of transformers on the inverter substrate to supply a high voltage AC waveform to each of the lamps; and a plurality of pattern capacitors on the inverter substrate to limit the electric current supplied to each of the lamps. The patterns capacitors have a plurality of capacitor patterns on a front surface of the inverter substrate with a designated distance therebetween and a first ground line on a rear surface of the inverter substrate overlapping the capacitor patterns.

Claims

1. A lamp driving device for driving a plurality of lamps in a liquid crystal display device, comprising:

an inverter substrate;

a plurality of transformers on the inverter substrate to supply a high voltage AC waveform to each of the lamps; and

a plurality of pattern capacitors on the inverter substrate to limit the electric current supplied to each of the lamps, the pattern capacitors including a plurality of capacitor patterns on a front surface of the inverter substrate with a designated distance therebetween and a first ground line on a rear surface of the inverter substrate overlapping the capacitor patterns.

2. The lamp driving device according to claim 1, wherein the direct illumination type backlight unit includes:

a bottom cover to hold the lamps;

a diffusion plate to cover the front surface of the bottom cover; and

at least one optical sheet on the diffusion plate.

3. The lamp driving device according to claim 1, further comprising:

a feedback substrate connected to a low voltage electrode of each of the lamps;

a feedback circuit mounted on the feedback substrate to detect a tube current of the lamps to generate a feedback signal; and

a feedback cable connected between the feedback circuit and the inverter substrate to supply the feedback signal to the inverter substrate.

4. The lamp driving device according to claim 3, further comprising:

a plurality of inverter integrated circuits arranged in series on the inverter substrate with a designated distance therebetween to convert a lamp drive voltage supplied from the outside by use of a switching device into an AC waveform;

a main integrated circuit disposed on the inverter substrate to control the inverter integrated circuits

wherein the plurality of transformers is arranged in series on the inverter substrate to convert the AC waveform from the inverter integrated circuits to a high voltage AC waveform and to supply the high voltage AC waveform to the pattern capacitors; and

5. The lamp driving device according to claim 4, further comprising a plurality of output connectors arranged at an edge portion of the inverter substrate and connected with the pattern capacitors to output the high voltage AC waveform from each of the transformers to a high voltage electrode of each of the lamps.

6. The lamp driving device according to claim 5, further comprising:

a second ground line formed on the rear surface of the inverter substrate to supply a ground voltage to the inverter integrated circuit;

a connecting line to connect the first ground line with the second ground line; and

a plurality of feedback signal lines disposed between the first ground line and the second ground line to provide the feedback signal, supplied through the feedback cable, to the inverter integrated circuits.

7. The lamp driving device according to claim 6, wherein the first ground line is disposed on the rear surface of the inverter substrate between the transformers and the output connectors.

8. The lamp driving device according to claim 6, wherein the second ground line is disposed on the rear surface of the inverter substrate between the main integrated circuit and the inverter integrated circuits.

9. The lamp driving device according to claim 6, wherein the feedback signal line is disposed on the rear surface of the inverter substrate between the inverter integrated circuits and the transformers.

10. The lamp driving device according to claim 6, wherein a distance between the first ground line and the feedback signal line is at least 10 mm.

11. The lamp driving device according to claim 6, wherein a distance between the first ground line and the second ground line is at least 20 mm.

12. A liquid crystal display device, comprising:

a liquid crystal display panel;

a direct illumination type backlight unit having a plurality of lamps to provide light to the liquid crystal display panel;

an inverter substrate having a plurality of transformers to supply a high voltage AC waveform to each of the lamps; and

a plurality of pattern capacitors on the inverter substrate to limit the electric current supplied to each of the lamps, the pattern capacitors including a plurality of capacitor patterns on a front surface of the inverter substrate with a designated distance there between and a first ground line on a rear surface of the inverter substrate overlapping the capacitor patterns.

13. The liquid crystal display device according to claim 12, wherein the direct illumination type backlight unit includes:

a bottom cover to hold the lamps;

a diffusion plate to cover the front surface of the bottom cover; and

at least one optical sheet on the diffusion plate.

14. The liquid crystal display device according to claim 12, further comprising:

a feedback substrate connected to a low voltage electrode of each of the lamps;

a feedback circuit mounted on the feedback substrate to detect a tube current of the lamps to generate a feedback signal; and

a feedback cable connected between the feedback circuit and the inverter substrate to supply the feedback signal to the inverter substrate.

15. The liquid crystal display device according to claim 14, wherein the inverter substrate includes:

a plurality of inverter integrated circuits arranged in series with a designated distance therebetween to convert a lamp drive voltage supplied from the outside by use of a switching device into an AC waveform;

a main integrated circuit disposed on the inverter substrate to control the inverter integrated circuits; and

a plurality of output connectors arranged at an edge portion of the inverter substrate and connected with the pattern capacitors to output the high voltage AC waveform from each of the transformers to a high voltage electrode of each of the lamps

wherein the plurality of transformers is arranged in series on the inverter substrate to convert the AC waveform from the inverter integrated circuits to a high voltage AC waveform and to supply the high voltage AC waveform to the pattern capacitors.

16. The liquid crystal display device according to claim 15, wherein the inverter substrate includes:

a second ground line formed on the rear surface of the inverter substrate to supply a ground voltage to the inverter integrated circuit;

a connecting line to connect the first ground line with the second ground line; and

a plurality of feedback signal lines disposed between the first ground line and the second ground line to provide the feedback signal, supplied through the feedback cable, to the inverter integrated circuits.

17. The liquid crystal display device according to claim 16, wherein the first ground line is disposed on the rear surface of the inverter substrate between the transformers and the output connectors.

18. The liquid crystal display device according to claim 16, wherein the second ground line is disposed on the rear surface of the inverter substrate between the main integrated circuit and the inverter integrated circuits.

19. The liquid crystal display device according to claim 16, wherein the feedback signal line is disposed on the rear surface of the inverter substrate between the inverter integrated circuits and the transformers.

20. The liquid crystal display device according to claim 16, wherein a distance between the first ground line and the feedback signal line is at least 10 mm.

21. The liquid crystal display device according to claim 16, wherein a distance between the first ground line and the second ground line is at least 20 mm.