Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1998-09-09
2001-04-17
Hjerpe, Richard (Department: 2674)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S092000, C345S211000, C345S214000, C345S094000, C345S098000, C345S212000, C345S089000
Reexamination Certificate
active
06219016
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to display devices, and more particularly to liquid crystal display devices.
BACKGROUND OF THE INVENTION
Liquid crystal displays are widely used flat panel display devices. As is well known to those having skill in the art, a liquid crystal display includes a liquid crystal display panel that displays images using the variable transmissivity of liquid crystals in response to applied voltages. The liquid crystal display panel includes gate lines, data lines and an array of thin film transistors that are connected to the gate lines and the data lines. A data driver drives the data lines with a gray voltage, also referred to as a gray scale voltage, and is powered by a data driver supply voltage. A gate driver drives the gate lines with gate ON and OFF voltages, and is powered by a gate driver supply voltage. A timing converter is connected to the gate driver and the data driver to control timing of the gate driver and the data driver, and is powered by a timing converter supply voltage. The data driver, gate driver and timing converter may use different supply voltage levels. For example, the data driver supply voltage, gate driver supply voltage and timing converter supply voltage may be 3.3 volts or 5 volts. The gate ON voltage may be between 15 and 40 volts, and the gate OFF voltage may be between 0 and −15 volts. The gray voltage may be 5 volts or 10.5 volts.
The above-described voltages may be generated by a DC-to-DC converter that is part of the liquid crystal display. The DC-to-DC converter may receive supply voltages of 5 volts and 12 volts, and can convert these voltages to the various voltage levels described above.
In generating these voltages, it may be important that the various voltage levels are applied to the components of the liquid crystal display in a proper sequence, so that the liquid crystal display does not malfunction or become damaged. For example, if the gate ON or gate OFF voltage is generated before the timing converter supply voltage and the gate driver supply voltage, the gate ON and OFF voltage may be applied to the thin film transistors in the liquid crystal display panel before the timing converter and/or the gate drivers become operational. As a result, it is possible for the gate ON voltage or the gate OFF voltage to simultaneously turn on all of the thin film transistors. This may cause an excess amount of current to flow to the liquid crystal display panel and can result in a malfunction of the liquid crystal display panel and/or damage to the gate driver.
In order to reduce the likelihood that these problems may arise, the timing sequences in which the various voltages are applied to the various components of the LCD may be adjusted using an external device. The sequence of applying supply voltages to the various components may be set during manufacturing. Unfortunately, this may complicate the manufacturing process and may still result in improper operation of the liquid crystal display after manufacturing, which may damage the liquid crystal display.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide improved supply voltage control circuits and methods for liquid crystal displays.
It is another object of the present invention to provide supply voltage control circuits and methods that can reduce the likelihood of improper voltages being applied to the various components of a liquid crystal display.
It is another object of the invention to provide liquid crystal display supply voltage control circuits and methods that need not be individually set during manufacturing.
These and other objects are provided, according to the present invention, by liquid crystal displays that include power supply control circuits and methods that are responsive to a single DC input supply voltage, to generate operating voltages for the gate driver, the data driver and the timing converter of the liquid crystal display from the single DC input supply voltage. Preferably, the data driver supply voltage and the gate driver supply voltage are generated prior to generating the gray scale voltage and the gate ON and OFF voltages. Also preferably, the timing converter supply voltage is generated prior to generating the gray voltage and the gate ON and OFF voltages.
Accordingly, a single external power supply voltage may be used to generate the requisite supply and operational voltages for the components of the liquid crystal display. Moreover, the sequence of energizing the various components of the liquid crystal display may be automatically controlled, so that improper operation and/or failure of the liquid crystal display can be reduced and preferably prevented.
More specifically, liquid crystal displays according to the present invention include a liquid crystal display panel that displays images. The liquid crystal display panel includes a plurality of gate lines and data lines. A gate driver drives the gate lines and a data driver drives the data lines. A timing converter is connected to the gate driver and the data driver to control timing of the gate driver and the data driver. A power supply control circuit is responsive to a single DC input supply voltage, to generate operating voltages for the gate driver, the data driver and the timing converter from the single DC input supply voltage.
The data driver preferably drives the data lines with a gray voltage and is powered by a data driver supply voltage. The power supply control circuit generates the gray voltage and the data driver supply voltage from the single DC input supply voltage. Also preferably, the gate driver drives the gate lines with gate ON and OFF voltages and is powered by a gate driver supply voltage. The power supply control circuit generates the gate ON and OFF voltages and the gate driver supply voltage from the single DC input supply voltage.
According to another aspect of the invention, power supply control circuits and methods generate the data driver supply voltage and the gate driver supply voltage prior to generating the gray voltage and the gate ON and OFF voltages. The power supply control circuits and methods also preferably generate the timing converter supply voltage prior to generating the gray voltage and the gate ON and OFF voltages.
In a preferred embodiment, power supply control circuits preferably include a first DC-to-DC converter that is responsive to the single DC input supply voltage to generate at least one supply voltage that is supplied to the gate driver, the data driver and the timing generator. The power supply control circuits also include a gray voltage generator that is responsive to a gray voltage generator supply voltage, to generate gray voltages for the data driver. A second DC-to-DC converter is responsive to the first DC-to-DC converter, to generate the gray voltage generator supply voltage. A gate voltage generator is responsive to the gray voltage generator supply voltage, to generate gate ON and OFF voltages for the gate driver from the single DC input supply voltage.
The power supply control circuits also preferably include a switch that is connected between the single DC input supply voltage, the gate voltage generator and the gray voltage generator supply voltage, to supply the single DC input supply voltage to the gate voltage generator in response to the gray voltage generator supply voltage. The switch is preferably a transistor having a controlling electrode and a pair of controlled electrodes. The pair of controlled electrodes are connected between the single DC input supply voltage and the gate voltage generator, and the controlled electrode is preferably connected to the gray voltage generator supply voltage.
In another embodiment, the first DC-to-DC converter is responsive to the single DC input supply voltage, to generate first and second digital circuit supply voltages that are applied to digital circuits of the liquid crystal display. The second DC-to-DC converter is responsive to the second supply voltage. Accordingly, multiple internal operating vol
Hjerpe Richard
Myers Bigel & Sibley & Sajovec
Samsung Electronics Co,. Ltd.
Zamani Ali
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