| 摘要 |
<p>This invention relates to gradation display by pulse width control method (PWM method) in each pixel in a capacitive display apparatus such as electroluminescent liquid crystal display apparatus. The driving voltage applied to the data electrodes is caused to vary in a ramp waveform, and the number of gradations of gradation display by the PWM method is increased. Since the capacitive display apparatus is used, the driving pulse is increasingly influenced by capacity as the location of the pixel to be controlled is further away from the drive circuit of the data electrode and in particular its duration becomes extended. As a result, even for identical gradation data, uneven illumination may occur. In this invention, the pulse width applied to the data electrodes is gradually decreased as scanning of the electrodes progresses. Therefore, the brightness of the capacitive display apparatus may be made uniform over the entire screen surface. Also, in the invention an impedance converting means connected in series between a DC power supply and the data electrodes is controlled by a control signal, with a switching means being controlled to effect application of a current to the data electrode for a period according to gradation display data. <IMAGE></p> |
