Patent Application
20050140628
This application claims the benefit of Korean Application No. 2003-99347, filed on Dec. 29, 2003. The disclosure of the above application is incorporated herein by reference.
1. Technical Field
The invention relates to a liquid crystal display (LCD), and more particularly, to a driving system for an LCD in which an analog driving circuit unit is controlled in a programmable manner.
2. Related Art
LCDs are used for a large number of information processing devices such as computers because of slim and lightweight designs and good performances as display devices. As demands for LCDs increase, it is required to improve an image quality of LCDs such as brightness, contrast ratio, etc.
The LCD module 1 operates as follows. Digital image signals from the digital video card 10 are first transmitted to the controller 11. The controller 11 synchronizes the digital image signals and provides synchronized signals to the data driver 13. In addition, the controller 11 delivers to the gate driver 12 scanning signals for turning on/off the TFTs connected with the data lines. The data driver 13 converts digital image signals delivered from the controller 11 to analog image signals and sequentially transfers the analog signals to a plurality of data lines formed on the liquid crystal panel 20. When the digital image signals are converted into the analog image signals, the gamma circuit 15 provides a gamma voltage for controlling the transmittance of the liquid crystal. Specifically, the gamma voltage provided by the gamma circuit 15 is divided into a plurality of tone voltages by resistor circuits disposed inside of the gamma circuit 15. Each divided tone voltage corresponds to each digital image signal and is eventually outputted to the respective data line as analog image signals. Meanwhile, the gate driver 12 turns on/off the TFT by sequentially providing scanning signals to a plurality of gate lines formed on the liquid crystal panel 20. Accordingly, the analog image signals delivered from the data lines are transferred to a respective pixel area.
The gamma circuit 15 has a plurality of resistors R1, R2, . . . Rn, which are connected in series and divide a voltage. Each resistor R1, R2, . . . Rn is connected to a buffer 35 which includes an operational amplifier (“OP Amp”), respectively. Another resistors R11 . . . Rnn are connected to an output terminal of the buffer so that the previously divided voltage may be divided again. The respective gamma voltage is outputted therefrom.
The Vcom circuit 40 has the following construction. A plurality of resistors R101, R102 . . . and a variable resistor VR1 are connected in series and divide a voltage. Each divided voltage is transferred to a buffer 45 including an OP Amp. An output terminal of the buffer 45 outputs a Vcom voltage which is appropriate for a liquid crystal panel. The inverter controller 50 receives an analog voltage and converts the voltage by using resistors disposed therein (not shown). Consequently, the inverter controller 50 generates a control signal for driving an inverter of an LCD.
The analog driving circuits 31 results in a large size and high manufacturing costs because each driving circuit needs to be separately manufactured. Further, because an output voltage is generated after the analog voltage is divided by multiple resistors, such voltage is not generated in a programmable manner. Specifically, once resistances of multiple resistors are determined, it is not possible to change output voltages generated by multiple resistors. Consequently, the analog driving circuits 31 cannot be controlled by a digital processor that processes digital image signals. There is a need for a driving circuit for an LCD that overcomes the foregoing drawbacks of the related art.
A driving system for an LCD is provided that includes an analog driving circuit unit, a digital analog converter and a digital interface unit. The digital analog converter supplies an analog voltage that operates the analog driving circuit unit. The digital interface unit supplies a digital signal to the digital analog converter. The analog driving circuit unit, the digital analog converter and the digital interface unit may be formed on a single chip. In one embodiment, an analog driving circuit unit includes a gamma circuit, a common circuit, and an inverter controller.
A driving system for an LCD can improve a display quality by integrating the analog driving circuit unit with other circuit elements and controlling it with a control signal. A digital image signal processor and/or an EEPROM (Electronically Erasable Programmable Read Only Memory) generate and provide such control signal. Accordingly, the driving circuit can control the analog driving circuit unit in a programmable manner.
The invention can be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like referenced numerals designate corresponding parts throughout the different views.
Referring to
In operation, the DSP 200 receives a digital image signal from an input terminal 201. The input terminal 201 of the DSP 200 may be disposed between a digital video card such as the digital video card 10 and a controller such as the controller 11. Alternatively, the input terminal 201 may be disposed between a controller such as the controller 11 and a data driver such as the data driver 13. The DSP 200 analyzes the digital image signal per frame and determines whether at least one image quality, for example, a brightness or a contrast ratio, needs to be adjusted. The EEPROM 300 stores various control signals as default values. The DSP 200 fetches a control signal that adjusts the image quality from the EEPROM 300 and provides it to the digital interface unit 101. Alternatively, if the EEPROM 300 does not store a necessary control signal, the DSP 200 may generate such control signal. Then, the control signal is transmitted to the DAC unit 103 through the digital interface unit 101. The DAC unit 103 converts the control signal into an analog signal and directly transmits it to the gamma circuit 105, the Vcom circuit 107 and/or the inverter controller 109.
An example of the above operation is described. The DSP 200 analyzes an image data at frame 1. The DSP 200 determines that a brightness of the image data should be adjusted because the image data is too dark. The DSP 200 verifies whether the EEPROM 300 stores a control signal that increases a brightness of a backlight. If the EEPROM 300 stores the control signal, the control signal is selected and transmitted to a digital interface unit 101. If the EEPROM 300 does not store the control signal, the DSP 200 may generate a necessary control signal. The control signal from the EEPROM 300 is provided to the DAC 103 via the digital interface unit 101. Subsequently, the DAC unit 103 converts this signal into an analog voltage and provides the same to the inverter controller 109. Based on the received analog voltage, the inverter controller 109 controls an inverter that drives a backlight of a liquid crystal panel such as the liquid crystal panel 20. The brightness of the backlight of the liquid crystal panel is increased and an image data at frame 2, which is brighter than the image data at the frame 1, is displayed.
Alternatively, as a result of analyzing the image data, the DSP 200 may determine that a contrast ratio is required to be adjusted. Then, either the DSP 200 or the EEPROM 300 provides a control signal for changing a gamma voltage to the DAC unit 103 through the digital interface unit 101. The DAC unit 103 converts this control signal into an analog signal and provides the same to the gamma circuit 105. The gamma circuit 105 provides the analog signal to a liquid crystal panel through a data driver such as the data driver 13. The analog voltage provided to the gamma circuit 105 is not divided by multiple resistors (as shown in
The Vcom circuit 107 may be configured in a manner that the gamma circuit 105 is configured as described above. Specifically, the DSP 200 analyzes an image data and determines that a reference voltage needs to be adjusted. A Vcom control signal in a digital signal format is provided to the DAC unit 103. The DAC unit 103 converts the digital signal into an analog voltage and provides it to the Vcom circuit 107. The Vcom circuit 107 provides the analog voltage to a liquid crystal panel. Because the Vcom circuit 107 does not require circuit elements such as resistors and variable resistors, a simple construction is possible. The analog voltage provided to the Vcom circuit 107 is controlled by the control signal provided from the EEPROM 300 or generated from the DSP 200. Analog voltage is transmitted through a buffer 107a of the Vcom circuit 107, but the buffer 107a may be omitted.
The DSP 200 of the analog driving circuit unit 100 consistently analyzes a displayed image and preferably provides control signals to the gamma circuit 105, the Vcom circuit 107 and/or the inverter controller 109. As a result, a display quality is optimized. As a result, analog circuits are controlled by the DSP 200 in a programmable manner. Furthermore, the analog circuits can be arranged to be integrated on a single chip. This arrangement facilitates control of the analog circuits by the DSP 200 and reduces manufacturing costs and device sizes.
While various embodiments of the invention have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible within the scope of the invention. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| P2003-99347 | Dec 2003 | KR | national |
