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Color matching method with cyclic voltage setting

IP.com Disclosure Number: IPCOM000014431D
Original Publication Date: 2001-Nov-01
Included in the Prior Art Database: 2003-Jun-19
Document File: 5 page(s) / 90K

Publishing Venue

IBM

Abstract

Disclosed here is a method of color matching of TFT-LCD panels. TFT-LCD panels are composed of Liquid Crystal Cell, Source line driver IC, Gate line driver IC, Timing controller, DCDC converter and analogue circuit to generate several reference voltages etc. Source line driver IC has many input terminals of digital data and analogue reference voltage (VREFs) like fig.1. PCB Data Bus (Digital)

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Color matching method with cyclic voltage setting

Disclosed here is a method of color matching of TFT-LCD panels.

      TFT-LCD panels are composed of Liquid Crystal Cell, Source line driver IC, Gate line driver IC, Timing controller, DCDC converter and analogue circuit to generate several reference voltages etc.

   Source line driver IC has many input terminals of digital data and analogue reference voltage (VREFs) like fig.1.

PCB Data Bus (Digital)

Timing Controller

VREF Bus (Analogue)

[Fig.1]

   In the source driver IC, the VREF settings are common for all R,G and B sub-pixels. If independent VREF voltages are required, there should be 3 times of VREF pins and 3 times of VREF circuit on the PCB. Those make it difficult to tune the gamma curve and color point of the TFT-LCD product or to make them programmable, which results in a difficulty to enhance the image quality, in other words, to reduce the variation of color points and gamma curves of the TFT-LCD panels.

   Described below is an idea to enable the gamma correction and color point adjustment independently for each R, G and B sub-pixels, and also to reduce the VREF pins of source driver IC and finally to remove the VREF circuit from the PCB in TFT-LCD panel.

Analogue Circuit

Source Driver

Source Driver

Source Driver

Source Driver

 Gate Driver

Liquid Crystal Cell

 Gate Driver

Subpixel Capacitance

 Gate Driver

1

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Proposed idea

   VREF circuit on the PCB is an analogue voltage generator. The source driver IC is also an analogue voltage generators composed of many DACs(Digital Analogue Converter). If a little bit additional DAC circuit is integrated inside the source driver IC, it can act as VREF generator.

   The new source driver IC has the additional pins, one is to output the VREF voltage and the other to input it, instead of the traditional 10 or more VREF input pins as showed in Fig 2. The new source driver internally has small capacitance latches to sample hold the voltage supplied from one of the source drivers which works as a master VREF generator. Also the PCB does not have the VREF generator circuit. (The VREF pins and the VREF circuit, both are required 3 times to enable RGB independent color matching under the traditional approach.)

2

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PCB Data Bus (Digital)

Data Bus (Utilized during H-blanking)

VREF transfer line

Timing Controller

New VREF Bus, Only "In"/"Out" for Master, Only "In" for slaves

Analogue Circuit

Source Driver

Source Driver

Sourc...