FIELD SEQUENTIAL COLOR MODE LIQUID CRYSTAL DISPLAY

• US 20070182699A1
• Filed: 12/04/2006
• Published: 08/09/2007
• Est. Priority Date: 02/09/2006
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electro-Mechanics Co., Ltd. (Samsung Group)
• Inventors: Min, Byoung Own, Cheon, Jeong In, Jang, Yu Jin, HA, Chang Woo
• Granted Patent: US 8,643,587 B2
• Time in Patent Office: Days
• US Class Current: 345/102
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• CPC Class Codes: H05B 45/38 using boost topology
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

In an FSC mode LCD, a controller operates in response to an external adjustment, and a DC/DC converter converts a battery voltage into a driving voltage under control of the controller. A color LED backlight includes first, second and third color LED arrays connected in parallel, which are operated by the driving voltage. An FSC generator generates first, second and third color PWM signals according to an internal sawtooth voltage and a dimming voltage. A 3-channel current source generates first, second and third driving currents under control of the controller, and on/off switches paths of the first, second and third driving currents flowing through the first, second and third color LED arrays according to the first, second and third color PWM signals generated from the FSC generator, thereby adjusting luminance of the first, second and third color LED arrays of the color LED backlight.

Claims

1. A field sequential color (FSC) mode liquid crystal display (LCD), comprising:

a controller operating in response to an external adjustment;

a DC/DC converter for converting a battery voltage into a driving voltage under control of the controller;

a color light emitting diode (LED) backlight including first, second and third color LED arrays connected in parallel, which are operated by the driving voltage outputted from the DC/DC converter;

an FSC generator for generating first, second and third color PWM signals, which are field sequential signals, according to an internal sawtooth voltage and a dimming voltage; and

a 3-channel current source for generating first, second and third driving currents under control of the controller, and on/off switching paths of the first, second and third driving currents flowing through the first, second and third color LED arrays of the color LED backlight according to the first, second and third color PWM signals generated from the FSC generator, thereby adjusting luminance of the first, second and third color LED arrays of the color LED backlight.

2. The FSC mode LCD of claim 1, wherein the first, second and third color PWM signals are sequential signals with the same width.

3. The FSC mode LCD of claim 2, wherein the FSC generator comprises:

a sawtooth voltage generating unit for generating a sawtooth voltage;

a comparing unit for comparing the sawtooth voltage with an external dimming voltage to output a PWM signal; and

an FSC logic unit for dividing the PWM signal by two and four, and operating a logic operation on the divided signals to generate the first, second and third color PWM signals.

4. The FSC mode LCD of claim 3, wherein the FSC logic unit comprises:

a first binary counter for dividing an output signal of the comparing unit by two to generate a first divided signal;

a second binary counter for dividing an output signal of the first binary counter by two to generate a second divided signal;

an inverter unit for inverting the first divided signal and the second divided signal to output a first inverted signal and a second inverted signal;

a first AND gate unit for ANDing the first and second inverted signals to output a first logic signal, ANDing the first divided signal and the second inverted signal to output a second logic signal, ANDing the first inverted signal and the second divided signal to output a third logic signal, and ANDing the first and second divided signals to output a fourth logic signal; and

a second AND gate unit for ANDing the first logic signal and the PWM signal to output a first color PWM signal, ANDing the second logic signal and the PWM signal to output a second color PWM signal, ANDing the third logic signal and the PWM signal to output a third color PWM signal, and ANDing the fourth logic signal and the PWM signal to output the second color PWM signal SP2.

5. The FSC mode LCD of claim 4, wherein the FSC logic unit further comprises an OR gate unit for ANDing the second color PWM signal given by ANDing the second logic signal and the PWM signal and the second color PWM signal given by ANDing the fourth logic signal and the PWM signal.

6. The FSC mode LCD of claim 4, wherein the second color LED array is provided with a plurality of green LEDs.

7. The FSC mode LCD of claim 6, wherein the FSC logic unit sequentially supplies the first color PWM signal, the second color PWM signal, the third color PWM signal, and the second color PWM signal at each period.

8. The FSC mode LCD of claim 6, wherein the first color LED array is provided with a plurality of red LEDs, and the third color LED array is provided with a plurality of blue LEDs.

9. The FSC mode LCD of claim 6, wherein the first color LED array is provided with a plurality of blue LEDs, and the third color LED array is provided with a plurality of red LEDs.