JPS595283A - Liquid crystal driving circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid crystal drive circuit whose purpose is to prevent an increase in brightness of non-selected segments due to a delay in a drive element in driving a liquid crystal display.

In recent years, with the development of production technology and the expansion of demand for liquid crystal displays, contrast has begun to be affected to a large extent by demands for an enlargement of the display area of liquid crystal displays and an increase in driving frequency. There are various possible reasons for poor contrast, but as the display area increases and the drive frequency increases, unnecessary effective voltage is applied to non-selected segments due to delay in the drive circuit, causing an increase in brightness. This phenomenon becomes more noticeable as the driving frequency increases.

The present invention is a liquid crystal drive circuit that eliminates the above-mentioned drawbacks and prevents an increase in brightness of non-selected segments due to delay in drive elements.

The present invention will be explained below based on examples.

FIG. 1 shows a conventional static liquid crystal driving circuit. 1 corresponds to a segment driver. The segment driver is configured with exclusive OR, and the output signal 7 of the common driver 3 which drives the common driver signal 5 by the signal of the segment signal line 4 and the output signal of the segment driver 1 are used to control the segment of the liquid crystal display. Electrode 6. A signal from the common driver is applied to the common electrode 7 to create a selected or non-selected state. It should be noted here that the driving waveforms applied to the segment electrodes 6 and the common electrode 7 are out of phase by the delay time of the segment electrodes. This delay time is indicated by di in the time chart of FIG. This phase shift leads to an increase in the brightness of non-selected segments, resulting in poor contrast. This phase shift is a function of the liquid crystal display area and the driving frequency, and as both of them increase, the phase shift increases.

FIG. 2 shows a liquid crystal driving circuit according to the present invention.

The drive signal 10 drives the segment driver 4 and is applied to the segment electrodes of the liquid crystal display 6 through the analog switch 7 which is turned on when selected. On the other hand, the drive signal 10 is transmitted to the segment driver 4. The common driver 5 is driven and a voltage is applied to the common electrode 12.

The output waveforms of the segment driver 4 and the common driver 5 are mutually inverted waveforms. To set the liquid crystal display 6 to the 11 selection state, the segment signal line 13 is set to low level, the signal line 14 is set to high level through the analog switch driver 9, and the azolog switch 7, which is conductive when selected, is made conductive to connect the electrodes of the liquid crystal display 6. The inverted waveforms of the drive signals are applied to each of them to bring them into a selected state. Conversely, when not selected, the segment signal line 13 is set to a high level, the analog switch 8, which is conductive when not selected, is made conductive, and the common electrode 12 of the liquid crystal display 6 and the segment electrode 55 are short-circuited, resulting in a non-selected state. By doing this, the liquid crystal display is separated from the segment and common driver when it is not selected, so if the driving method according to the present invention is adopted, the brightness of the non-selected segment will not increase due to driver delay. Contrast defects related to driver delay due to increases in driving frequency and liquid crystal display area can be completely eliminated, and the present invention does not require any special circuit configuration and can be configured with a completely simple circuit. .

[Brief explanation of drawings]

FIG. 1 shows a liquid crystal drive circuit according to the prior art, FIG. 2 shows a liquid crystal drive circuit according to the present invention, and FIG. 3 shows a time chart. Fig. 1 1... Segment driver 2... Liquid crystal display 3... Common driver Fig. 2 4... Segment driver 5... Common Driver 6...LCD display

Claims (1)

[Claims] (1) A common driver that drives a common electrode of a liquid crystal display element, a segment driver that drives a signal electrode, an analog switch that conducts when a segment is selected, an analog switch that conducts when a segment is not selected, and drives the analog switch. When a segment is selected, a drive waveform that is an inversion of the common electrode waveform is applied to the signal electrode through the analog switch;
A liquid crystal drive circuit characterized in that when non-selected, the common electrode and the signal electrode are short-circuited through the analog switch so that an effective voltage applied to the non-selected segment is not applied due to the delay time of the driver.