Liquid crystal display
View Patent ↗A liquid crystal display (LCD) capable of enhancing display quality includes a voltage generation unit, a clock generation unit, a gate driving unit, and a display unit. The voltage generation unit outputs a gate-on voltage and first and second gate-off voltages that are different from each other. The clock generation unit outputs a first clock signal and a second clock signal whose phase is opposite to the phase of the first clock signal. The first clock signal swings between the gate-on voltage and the first gate-off voltage. The gate driving unit is provided with the first clock signal, the second clock signal, and the second gate-off voltage and outputs a gate signal. The display unit includes a plurality of pixels that are turned on or off in response to the gate signal and that display an image.
1. A liquid crystal display (LCD) comprising:
a voltage generation unit which outputs a gate-on voltage and first and second gate-off voltages, the first and second gate-off voltages being different from each other;
a clock generation unit which outputs a first clock signal and a second clock signal whose phase is opposite to the phase of the first clock signal, the first clock signal swinging between the gate-on voltage and the first gate-off voltage;
a gate driving unit which is provided with the first clock signal, the second clock signal, and the second gate-off voltage and outputs a gate signal; and
a display unit which comprises a plurality of pixels that are turned on or off in response to the gate signal and that display an image,
wherein the voltage generation unit comprises:
a temperature sensor which outputs a temperature-variable voltage which varies according to the ambient temperature;
a boost converter which generates a driving voltage and a pulse signal by boosting a first input voltage and outputs the driving voltage and the pulse signal, the driving voltage varying according to the temperature-variable voltage;
a gate-on voltage generator which generates the gate-on voltage by shifting the driving voltage by an amount corresponding to the voltage of the pulse signal and outputs the gate-on voltage;
a first gate-off voltage generator which generates the first gate-off voltage by shifting the second input voltage by the amount corresponding to the voltage of the pulse signal and outputs the first gate-off voltage; and
a second gate-off voltage generator which receives the first gate-off voltage, generates the second gate-off voltage by dividing the first gate-off voltage, and outputs the second gate-off voltage.
2. The LCD of claim 1 , wherein the gate signal swings between the gate-on voltage and the second gate-off voltage.
3. The LCD of claim 2 , wherein the amplitude of the gate signal decreases as the ambient temperature increases and increases as the ambient temperature decreases.
4. The LCD of claim 1 , wherein the first gate-off voltage is lower than the second gate-off voltage.
5. The LCD of claim 1 , wherein the gate-on voltage decreases as the ambient temperature increases and increases as the ambient temperature decreases.
6. The LCD of claim 1 , wherein the temperature-variable voltage decreases as the ambient temperature increases and increases as the ambient temperature decreases.
7. The LCD of claim 6 , wherein the temperature sensor comprises at least one diode which has a threshold voltage that varies substantially in inverse proportion to the ambient temperature.
8. The LCD of claim 1 , wherein the second gate-off voltage generator comprises:
a voltage divider which divides the first gate-off voltage; and
a Zener diode which uniformly outputs the second gate-off voltage.
9. The LCD of claim 1 , wherein the first gate-off voltage increases as the ambient temperature increases and decreases as the ambient temperature decreases.
10. The LCD of claim 1 , wherein the gate driving unit comprises a plurality of stages which sequentially output the gate signal, each of the stages comprising at least one amorphous silicon thin film transistor (a-Si TFT).
11. An LCD comprising:
a voltage generation unit which comprises a temperature sensor that outputs a temperature-variable voltage which varies according to the ambient temperature,
a boost converter that generates a driving voltage and a pulse signal by boosting a first input voltage which varies according to the temperature-variable voltage,
a gate-on voltage generator that generates the gate-on voltage by shifting the driving voltage by an amount corresponding to the voltage of the pulse signal,
a first gate-off voltage generator that generates the first gate-off voltage by shifting a second input voltage by an amount corresponding to the voltage of the pulse signal,
a second gate-off voltage generator that receives the first gate-off voltage, generates the second gate-off voltage by dividing the first gate-off voltage and outputs the second gate-off voltage;
a signal control unit which provides a scan start signal;
a clock generation unit which outputs a first clock signal and a second clock signal whose phase is opposite to the phase of the first clock signal, the first clock signal swinging between the gate-on voltage and the first gate-off voltage;
a gate driving unit which is enabled by the scan start signal, receives the first clock signal and the second clock signal and outputs a gate signal that swings between the gate-on voltage and the second gate-off voltage; and
a display unit which comprises a plurality of pixels that are turned on or off in response to the gate signal and that display an image.
12. The LCD of claim 11 , wherein the amplitude of the gate signal decreases as the ambient temperature increases and increases as the ambient temperature decreases.
13. The LCD of claim 11 , wherein the temperature-variable voltage increases as the ambient temperature increases and decreases as the ambient temperature decreases.
14. The LCD of claim 11 , wherein the second gate-off voltage is uniform regardless of the ambient temperature.
15. The LCD of claim 14 , wherein the second gate-off voltage generator comprises:
a voltage divider which divides the first gate-off voltage; and
a Zener diode which uniformly outputs the second gate-off voltage.
16. The LCD of claim 11 , wherein the first gate-off voltage is lower than the second gate-off voltage.
17. The LCD of 11 , wherein the gate driving unit comprises a plurality of stages which sequentially output the gate signal, each of the stages comprising:
a charge unit which is charged in response to the scanning start signal or a carry signal of a previous stage;
a pull-up unit which outputs the first clock signal or the second clock signal as the gate signal when the charge unit is charged;
a pull-down unit which pulls down the voltage of the gate signal to the second gate-off voltage in response to a gate signal of a subsequent stage; and
a discharge unit which discharges the charge unit in response to the gate signal of the subsequent stage.