Liquid crystal display device

1. A liquid crystal display device comprising:

a liquid crystal display panel having a number of pixels;

wherein each of said pixels has a pixel electrode to which an image voltage is supplied and a counter electrode to which a common voltage is supplied; and

wherein when two pixels adjacent to each other along one display line are a first pixel and a second pixel, an image voltage at a potential higher than that of the common voltage supplied to the counter electrode is applied to the pixel electrode of the first pixel and an image voltage at a potential lower than that of the common voltage supplied to the counter electrode is applied to the pixel electrode of the second pixel when the image voltage is written into the pixel electrode;

a common voltage generating circuit for generating a common voltage supplied to each of the counter electrodes of said pixels;

a feedback means for detecting a fluctuation in the potential of the common voltage in a number of places within each of said counter electrodes so that the fluctuation is fed back to said common voltage generating circuit; and

a supply end for supplying said common voltage to each of said counter electrodes from said common voltage generating circuit, characterized in that

on the basis of a fluctuation in the potential that has been fed back by said feedback means, said common voltage generating circuit supplies a common voltage that is gained by superposing a reverse correction voltage for offsetting said fluctuation in the potential on a reference common voltage, which is a common voltage before said fluctuation in the potential is fed back, to the counter electrode; and

when point A is located at a distance away from said supply end and point B is located closer to said supply end than point A, the voltage that fluctuates at said point A is voltage A and the voltage that fluctuates as said point B is voltage B, said feedback means detects fluctuations in the potential in two places for said voltage A and said voltage B so that the fluctuations are fed back to said common voltage generating circuit.

2. The liquid crystal display device according to claim 1 , characterized in that

said common voltage generating circuit has a mixing means for mixing said voltage A and said voltage B and an amplifier circuit for inverting and amplifying the voltage mixed in said mixing means so that the resulting voltage is superposed on said reference common voltage and is supplied to said counter electrodes.

3. The liquid crystal display device according to claim 2 , characterized in that

the direction in which said liquid crystal display panel is scanned vertically is the direction from said point A toward said point B, and

said mixing means continuously changes the mixture ratio of said voltage A and said voltage B in such a manner that said voltage A and said voltage B are mixed when having such a relationship as voltage A >voltage B at the beginning of one vertical scan period, and said voltage A and said voltage B are mixed when having such a relationship as voltage A<voltage B as the vertical scan period progresses.

4. The liquid crystal display device according to claim 3 , characterized in that

said mixing means has a resistor A where said voltage A is inputted at one end, a resistor B where said voltage B is inputted at one end, and a transistor connected between the other end of said resistor A and the other end of said resistor B,

the resistance value of said resistor A is higher than the resistance value of said resistor B,

said voltage A is inputted into said amplifier circuit through resistor A,

said voltage B is inputted into said amplifier circuit through said resistor B and said transistor, and

the mixture ratio of said voltage A and said voltage B is changed by changing the gate voltage of said transistor.

5. The liquid crystal display device according to claim 4 , characterized in that

said mixture means has a D/A converting circuit for converting the inputted digital control signal into an analog control signal and for inputting the converted analog control signal into the gate of said transistor, and

the mixture ratio of said voltage A and said voltage B is changed by changing the gate voltage of said transistor in accordance with the change in said inputted digital control signal.

6. The liquid crystal display device according to claim 5 , further comprising a display control circuit and a power supplying circuit, characterized in that

said common voltage generating circuit is provided within said power supplying circuit, and

said display control circuit generates a digital control signal, which is inputted into said common voltage generating circuit within said power supplying circuit.

7. The liquid crystal display device according to claim 3 , characterized in that

said mixing means has a resistor A where said voltage A is inputted at one end, a resistor B where said voltage B is inputted at one end, and a digital control variable resistor which is connected between the other end of said resistor A and the other end of said resistor B and into which said digital control signal is inputted,

the resistance value of said resistor A is greater than the resistance value of said resistor B,

said voltage A is inputted into said amplifier circuit through said resistor A,

said voltage B is inputted into said amplifier circuit through said resistor B and said digital control variable resistor, and

the mixture ratio of said voltage A and said voltage B is changed by changing the resistance value of said digital control variable resistor in accordance with the change in said inputted digital control signal.

8. The liquid crystal display device according to claim 2 , characterized in that

the direction in which said liquid crystal display panel is scanned vertically is the direction from said point A toward said point B, and

said mixing means continuously changes the mixture ratio of said voltage A and said voltage B in such a manner that said voltage A and said voltage B are mixed when having such a relationship as voltage A >voltage B at the beginning of one vertical scan period, and said voltage A and said voltage B are mixed when having such a relationship as voltage A <voltage B as the vertical scan period approaches the end.