Liquid crystal display device

1. A display device for displaying display data, comprising:

a display panel having a plurality of pixels disposed in a matrix format;

a Y-circuit for generating a Y-selecting signal for selecting one or more pixel rows of said plurality of pixels and outputting said Y-selecting signals to said pixels; and

an X-circuit for generating a tone signal according to said display data for each of said plurality of pixels and outputting said tone signal to said plurality of pixels,

wherein each of said plurality of pixels includes a memory for holding the tone signal, a conversion circuit for converting, based on a sweep signal of a stepwise waveform, the tone signal from said memory into a pulse voltage having a time width according to said display data, and an electrode driven by the pulse voltage.

2. A display device according to claim 1 , wherein said X-circuit generates an X-selecting signal for selecting one or more pixel columns of said plurality of pixels and outputting said X-selecting signals to said pixels.

3. A display device according to claim 1 , wherein said sweep signal has a waveform having an amplitude which becomes smaller in a stepwise manner.

4. A display device according to claim 1 , wherein said sweep signal is synchronized with an alternating period.

5. A display device according to claim 1 , wherein said conversion circuit includes a first conversion circuit for adding the sweep signal to the tone signal from the memory and outputting a high-level voltage or a low-level voltage, and a second conversion circuit for outputting, in accordance with the signal from said first conversion circuit, an ac signal having an amplitude which changes periodically or a center voltage having a level between the high-level voltage and the low-level voltage thereby to output said pulse voltage.

6. A display device for displaying display data, comprising:

a display panel having a plurality of pixels disposed in a matrix format;

a Y-circuit for generating a Y-selecting signal for selecting one or more pixel rows of said plurality of pixels and outputting said Y-selecting signals to said pixels; and

an X-circuit for generating a tone signal according to said display data for each of said plurality of pixels and outputting said tone signal to said plurality of pixels,

wherein each of said plurality of pixels includes a memory for holding the tone signal, a first conversion circuit for generating a binary pulse signal having a time width according to the tone signal from said memory, a second conversion circuit for outputting, in accordance with a level of the pulse signal, an ac signal having an amplitude which changes periodically or a center voltage having a level between a high level and a low level of the ac signal, and an electrode driven by the selected signal from said selection circuit.

7. A display device according to claim 6 , wherein said X-circuit generates an X-selecting signal for selecting one or more pixel columns of said plurality of pixels and outputting said X-selecting signals to said pixels.

8. A display device according to claim 6 , wherein said second conversion circuit outputs said ac signal to said electrode during a time period derived by multiplying a time ta, which is derived by dividing an alternating period T of said ac signal by a square of a tone number of said display data, by a square of said tone number, and wherein an amplitude of said ac signal is constant.

9. A display device according to claim 6 , wherein:

said second conversion circuit outputs said ac signal to said electrode during a time period derived by multiplying a time tb, which is derived by dividing an alternating period T of said ac signal by a square of a tone number of said display data, by said tone number, and

an amplitude of said ac signal is increased by a value, which is derived by multiplying a square of a value derived by dividing 2 by said tone number by a reference amplitude at each divided time tb.