Display device and driving device for a light source

• US 20060017404A1
• Filed: 07/22/2005
• Published: 01/26/2006
• Est. Priority Date: 07/22/2004
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Jang, Hyeon-Yong
• Granted Patent: US 7,595,785 B2
• Time in Patent Office: Days
• US Class Current: 315/291
• CPC Class Codes: G09G 2320/041 Temperature compensation
• CPC Class Codes: G09G 2330/04 Display protection
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: H05B 41/2858 for protecting the lamp against abnormal operating conditions
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps

Abstract

A light source portion for a liquid crystal display (LCD) device may prevent reduction of the life span of the multiple lamps (LPs) when a surrounding temperature of the multiple LPs is less than a predetermined temperature of the LCD device. The LCD device comprises first and second brightness control portions receiving a brightness control signal, a temperature sensor, a signal output portion connected to the first and second brightness control portions and the temperature sensor, and an inverter portion turning on or turning off the multiple LPs based on the control signal from the signal output portion. When the temperature sensed by the temperature sensor is less than the predetermined temperature of the LCD device, the signal output portion switches the brightness control signal from a high level to a low level, and makes the multiple LPs maintain the high level until the surrounding temperature becomes more than the predetermined temperature.

Claims

1. A driving device for at least one light source, comprising:

a temperature sensor operable for sensing a surrounding temperature of the light source and outputting a first control signal in response to the sensed temperature;

a signal output portion operable for receiving a second control signal based on a first brightness control signal applied from an external source;

changing the second control signal based on the first control signal; and

outputting the changed second control signal; and

an inverter controller operable for receiving the changed second control signal and outputting a third control signal based on the changed second control signal.

2. The driving device for the at least one light source of claim 1, wherein the first control signal becomes a low level when the surrounding temperature of the light source is less than a predetermined temperature of the light source, and the second and third control signals are adjusted based on the first control signal.

3. The driving device for the at least one light source of claim 2, wherein the second control signal becomes a low level when the first control signal is a low level, and the third control signal is ramped up to a high level for driving the at least one light source.

4. The driving device for the at least one light source of claim 2, wherein the temperature sensor comprises:

a temperature sensing part connected to the power supply;

a first resistor disposed between the temperature sensing part and the ground;

a first capacitor disposed between the ground and the common terminal of the temperature sensing part and the first resistor;

second and third resistors in series disposed between the power supply and the ground;

a second capacitor disposed between the common terminal of the second and third resistors and the ground;

a fourth resistor connected to the common terminal of the temperature sensing part and the first resistor;

an operational amplifier that a negative terminal is connected to the common terminal of the second and third resistors and a positive terminal is connected to the fourth resistor; and

a fifth resistor disposed between the positive terminal and an output terminal of the operational amplifier.

5. The driving device for the at least one light source of claim 4, wherein the temperature sensing part is a thermistor and the operational amplifier is a comparator.

6. The driving device for the at least one light source of claim 5, wherein the operational amplifier has hysteresis characteristics.

7. The driving device for the at least one light source of claim 4, wherein the signal output portion comprises:

first and second diodes forwardly connected to the capacitor of the first brightness control portion;

a diode forwardly connected to a collector terminal of the transistor of the second brightness control portion; and

a first resistor connected to the output terminal of the operational amplifier of the temperature sensor and the diodes.

8. The driving device for the at least one light source of claim 7, further comprising:

a first brightness control portion operable for outputting the first control signal based on the first brightness control signal; and

a second brightness control portion operable for generating an output signal based on a second brightness control signal.

9. The driving device for the at least one light source of claim 8, wherein the first brightness control portion comprises:

a first resistor connected to a power supply;

a second resistor in common connected to the first resistor and an input terminal of the first brightness control signal;

a third resistor connected to the power supply;

a fourth resistor connected to a collector terminal of a transistor;

a transistor, the transistor having a base terminal connected to the second resistor, an emitter terminal connected to a ground, and a collector terminal connected to the fourth resistor; and

a capacitor disposed between the fourth resistor and the ground.

10. The driving device for the at least one light source of claim 9, wherein the first brightness control signal is a pulse width modulation (PWM) signal.

11. The driving device for the at least one light source of claim 10, wherein the second brightness control portion comprises:

a first resistor connected to a power supply;

a second resistor in common connected to the first resistor and an input terminal of the second brightness control signal;

a third resistor disposed between the second resistor and a ground;

a transistor having a base terminal connected to the second resistor and a collector terminal connected to the signal output portion; and

a fourth resistor disposed between an emitter terminal of the transistor and the ground.

12. The driving device for the at least one light source of claim 11, further comprising:

a switching portion operable for operating based on the third control signal;

converting a DC voltage applied from an external device into an AC voltage; and

outputting the AC voltage;

a transforming portion operable for ramping up the AC voltage to a higher voltage and outputting the higher voltage;

a light source portion operable for receiving the higher voltage and for turning on or turning off at least one lamp based on the higher voltage; and

an electric current sensor operable for sensing an electric current of the at least one lamp and for outputting a corresponding voltage in response to the sensed electric current.

13. The driving device for the at least one light source of claim 12, wherein the electric current sensor comprises a resistor connected to the signal output portion.

14. A driving device for at least one light source, comprising:

a temperature sensor, the temperature sensor operable for sensing a surrounding temperature of the light source and outputting a first control signal in response to the sensed temperature;

a first brightness control portion, the first brightness control portion operable for outputting the first control signal based on a first brightness control signal applied from an external source;

a signal output portion, the signal output portion operable for receiving a second control signal based on the first brightness control signal;

changing the second control signal based on the first control signal; and

outputting the changed second control signal;

an inverter controller, the inverter controller operable for receiving the changed second control signal and outputting a third control signal based on the changed second control signal;

a second brightness control portion, the second brightness control portion operable for generating an output signal based on a second brightness control signal; and

an electric current sensor operable for sensing an electric current of at least one lamp and outputting a corresponding voltage in response to the sensed electric current.

15. The driving device for the at least one light source of claim 14, wherein the first control signal becomes a low level when the surrounding temperature of the light source is less than a predetermined temperature of the light source, and the second and third control signals are adjusted based on the first control signal.

16. The driving device for the at least one light source of claim 15, wherein the second control signal becomes a low level when the first control signal is a low level, and the third control signal is ramped up to a high level for driving the light source.

17. A display device, comprising:

a display portion, the display portion comprising a display assembly, multiple data and gate tape carrier packages (TCPs) attached to the display assembly, and data and gate printed circuit boards attached to the corresponding data and gate TCPs; and

a backlight assembly, the backlight assembly comprising a light source portion having at least one light source, an optical portion disposed between the display assembly and the light source portion for adjusting amount of light from the light source portion, and an inverter portion operable for controlling operation of the light source portion;

wherein the inverter portion comprises;

a temperature sensor operable for sensing a surrounding temperature of the light source and outputting a first control signal in response to the sensed temperature;

a signal output portion operable for receiving a second control signal based on a first brightness control signal applied from an external source;

changing the second control signal based on the first control signal; and

outputting the changed second control signal; and

an inverter controller operable for receiving the changed second control signal and outputting a third control signal based on the changed second control signal.

18. The display device of claim 17, wherein the first control signal becomes a low level when the surrounding temperature of the light source is less than a predetermined temperature of the light source, and the second and third control signals are adjusted based on the first control signal.

19. The display device of claim 18, wherein the second control signal becomes a low level when the first control signal is a low level, and the third control signal is ramped up to a high level for driving the at least one light source.

20. The display device of claim 19, wherein the temperature sensor comprises:

a temperature sensing part connected the power supply;

a first resistor disposed between the temperature sensing part and the ground;

a first capacitor disposed between the ground and the common terminal of the temperature sensing part and the first resistor;

second and third resistors in series disposed between the power supply and the ground;

a second capacitor disposed between the common terminal of the second and third resistors and the ground;

a fourth resistor connected to the common terminal of the temperature sensing part and the first resistor;

an operational amplifier that a negative terminal is connected to the common terminal of the second and third resistors and a positive terminal is connected to the fourth resistor; and

a fifth resistor disposed between the positive terminal and an output terminal of the operational amplifier.

21. The display device of claim 20, wherein the temperature sensing part is a thermistor and the operational amplifier is a comparator.

22. The display device of claim 21, wherein the operational amplifier has hysteresis characteristics.

23. The display device of claim 22, further comprising:

a first brightness control portion operable for outputting the first control signal based on the first brightness control signal; and

a second brightness control portion operable for generating an output signal based on a second brightness control signal.