Inverter and liquid crystal display including inverter

• US 20040246226A1
• Filed: 05/21/2004
• Published: 12/09/2004
• Est. Priority Date: 05/23/2003
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Moon, Seung-Hwan
• Granted Patent: US 7,446,750 B2
• Time in Patent Office: Days
• US Class Current: 345/102
• CPC Class Codes: G02F 1/133604 with lamps
• 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
• CPC Class Codes: H05B 41/2824 using control circuits for the switching element H05B41/2822 takes precedence
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps

Abstract

An inverter is provided, which includes: a voltage converter that converts a DC voltage from an external device into an AC voltage to drive at least a lamp and includes a primary coil and first and second secondary coils connected in series; a current sensor that senses at least a current flowing in the first or second secondary coil and generate at least a sensing signal based on the sensed at least a current; a feedback signal generator that generates a feedback signal based on the at least a sensing signal from the current sensor; and a controller that controls the voltage converter based on the feedback signal such that a tube current flowing in the at least a lamp keeps substantially constant.

Claims

1. An inverter comprising:

a voltage converter that converts a DC voltage from an external device into an AC voltage to drive at least a lamp and includes a primary coil and first and second secondary coils connected in series;

a current sensor that senses at least a current flowing in the first or second secondary coil and generate at least a sensing signal based on the sensed at least a current;

a feedback signal generator that generates a feedback signal based on the at least a sensing signal from the current sensor; and

a controller that controls the voltage converter based on the feedback signal such that a tube current flowing in the at least a lamp keeps substantially constant.

2. The inverter of claim 1, wherein the at least a lamp comprises a plurality of lamps connected in parallel.

3. The inverter of claim 1, wherein the voltage converter applies voltages having the same magnitude and different polarities to respective ends of the at least a lamp.

4. The inverter of claim 1, wherein the at least a lamp comprises an external electrode lamp.

5. The inverter of claim 1, wherein the current sensor comprises first and second resistors connected in series between the first secondary coil and the second secondary coil, and a third resistor connected between a predetermined voltage and a first node between the first resistor and the second resistor.

6. The inverter of claim 5, wherein the first to third resistors have the same resistance.

7. The inverter of claim 5, wherein the at least a sensing signal includes a first voltage at a second node between the first secondary coil and the first resistor.

8. The inverter of claim 7, wherein the feedback signal generator rectifies the first voltage to generate the feedback signal.

9. The inverter of claim 7, wherein the at least a sensing signal further includes a second voltage at the first node between the first resistor and the second resistor.

10. The inverter of claim 9, wherein the feedback signal generator comprises:

a rectifier that rectifies the first and the second voltages; and

an operation unit that generates the feedback signal expressed as a first-order function of the rectified first and second voltages from the rectifier.

11. The inverter of claim 10, wherein the operation unit comprises:

a first amplifier that inverts the rectified first voltage; and

a second amplifier that doubles the rectified second voltage, adds the inverted first voltage from the first amplifier and the doubled rectified second voltage to generate a third voltage, and inverts the third voltage.

12. The inverter of claim 9, wherein the at least a sensing signal further includes a third voltage at a third node between the second secondary coil and the second resistor.

13. The inverter of claim 12, wherein the feedback signal generator comprises:

a rectifier that rectifies the first to third voltages;

a first operation unit that generates a first feedback signal expressed as a first-order function of the rectified first and second voltages; and

a second operation unit that generates a second feedback signal expressed as a first-order function of the rectified second and third voltages,

wherein the feedback signal includes a smaller one of the first and second feedback signals.

14. The inverter of claim 13, wherein the first operation unit comprises:

a first amplifier that inverts the rectified first voltage; and

a second amplifier that doubles the rectified second voltage, adds the inverted first voltage from the first amplifier and the doubled rectified second voltage to generate a fourth voltage, and inverts the fourth voltage, and

the second operation unit comprises;

a third amplifier that inverts the rectified third voltage; and

a fourth amplifier that doubles the rectified second voltage, adds the inverted third voltage from the third amplifier and the doubled rectified second voltage to generate a fifth voltage, and inverts the fifth voltage.

15. The inverter of claim 7, wherein the at least a sensing signal further includes a second voltage at a third node between the second secondary coil and the second resistor.

16. The inverter of claim 15, wherein the feedback signal generator comprises:

a rectifier that rectifies the first and second voltages;

a first operation unit that generates a first feedback signal expressed as a first-order function of the rectified first and second voltages; and

a second operation unit that generates a second feedback signal expressed as another first-order function of the rectified first and second voltages,

wherein the feedback signal includes a smaller one of the first and second feedback signals.

17. The inverter of claim 16, wherein the first operation unit comprises:

a fourth resistor;

a fifth resistor;

a first feedback resistor; and

a first amplifier that receives the first and second voltages through the fourth and fifth resistors, respectively, and has a negative feedback connection through the first feedback resistor, and

the second operation unit comprises;

a sixth resistor;

a seventh resistor;

a second feedback resistor; and

a second amplifier that receives the first and second voltages through the sixth and seventh resistors, respectively, and has a negative feedback connection through the second feedback resistor.

18. The inverter of claim 17, wherein a resistance ratio of the first feedback resistor, the fourth resistor, and the fifth resistor is about 1:

3;

1.5, and a resistance ratio of the second feedback resistor, the sixth resistor, and the seventh resistor is about 1;

1.5;

3.

19. The inverter of claim 5, wherein the primary coil comprises a first portion coupled with the first secondary coil to form a first transformer and a second portion coupled with the second secondary coil to form a second transformer, and the first transformer and a second transformer is spaced apart from each other on a printed circuit board.

20. The inverter of claim 19, wherein the first and second transformers are located near respective ends of the printed circuit board in a length direction.

21. A liquid crystal display comprising:

a lamp unit that includes a plurality of lamps;

an inverter that converts a DC voltage from a external device into a AC voltage to drive the lamp unit; and

a liquid crystal panel assembly that receives a light from the lamps to display images,

wherein the inverter includes;

a voltage converter that includes a primary coil and first and second secondary coils connected in series;

a current sensor that senses at least a current flowing in the first or second secondary coil and generate at least a sensing signal based on the sensed at least a current;

a feedback signal generator that generates a feedback signal based on the at least a sensing signal from the current sensor; and

a controller that controls the voltage converter based on the feedback signal such that a tube current flowing in the lamps keeps substantially constant.

22. The liquid crystal display of claim 21, wherein the lamps are connected in parallel.

23. The liquid crystal display of claim 21, wherein the voltage converter applies voltages having the same magnitude and different polarities to respective ends of the lamps.

24. The liquid crystal display of claim 21, wherein the lamps comprises an external electrode lamp.

25. The liquid crystal display of claim 21, wherein the current sensor comprises first and second resistors connected in series between the first secondary coil and second secondary coil, and a third resistor connected between a predetermined voltage and a first node between the first resistor and the second resistor.

26. The liquid crystal display of claim 25, wherein the first to third resistors have the same resistance.

27. The liquid crystal display of claim 25, wherein the at least a sensing signal includes a first voltage at a second node between the first secondary coil and the first resistor.

28. The liquid crystal display of claim 27, wherein the at least a sensing signal further includes a second voltage at the first node between the first resistor and the second resistor.

29. The liquid crystal display of claim 28, wherein the at least a sensing signal further includes a third voltage at a third node between the second secondary coil and the second resistor.

30. The liquid crystal display of claim 27, wherein the at least a sensing signal further includes a second voltage at a third node between the second secondary coil and the second resistor.

31. The liquid crystal display of claim of 25, further comprising an inverter printed circuit board that is equipped with the inverter,

wherein the primary coil comprises a first portion coupled with the first secondary coil to form a first transformer and a second portion coupled with the second secondary coil to form a second transformer, and the first transformer and a second transformer are spaced apart from each other on a printed circuit board.