JPS58197967A - Display device - Google Patents

Abstract

PURPOSE:To reduce power consumption, and to eliminate bad influence exerted on contrast, by clippig a video signal and a square wave or a part of the video signal at one field or every other field, and applying them alternately to a sampling circuit. CONSTITUTION:When display is executed by sampling a video signal and applying the signal voltage to each picture element, the video signal is set to a square wave at one field or every other field, or is set to a signal which clips a part of the video signal. This square wave and the signal which clips a part are applied as a video signal alternately to a sampling circuit. The absolute value of the potential of this square wave is made almost equal to that the the potential of a pedestal level of the video signal or a threshold level of a display element. Also, the clip voltage of the signal which clips the video signal is set to the voltage by which the transmissivity becomes 70-90%, in the voltage- transmissivity characteristic of the element to be used, thus the power consumption is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION Display device manufactured by the present invention, particularly display device K for displaying video signals
I'll do it.

Conventionally, in a display device for displaying a video signal, in order to extend the life of the display panel, as shown in the %as1 diagram, a voltage V 66m is applied between the video signal source v DO and %V as cv. For example, the signals are input to the sampling circuit so that the odd and even fields are inverted. However, this method requires twice the dynamic range of the signal as compared to the case where only one side is used. Therefore, the power supply voltage VDD-Van takes a very steep value, and the overall power consumption also increases.

The present invention has been made in view of the above-mentioned drawbacks, and is aimed at keeping the required power supply voltage low and reducing power consumption without impeding the longevity of liquid crystals. Let me explain the details. Figure 2 shows an embodiment of the present invention, in which the odd field signal is a completely square wave 1) υ, and the even field waveform is a conventional video signal va that is input to the sample and hold circuit. It is designed to be sent as a signal. However, the odd field and the even field are of course the same even if they are reversed. The voltage level vDD-vCOMIIi of this square wave is set to a value lower than the maximum value VJIMX of the video signal V#. The video signal v8 has changed to 马, and this video signal Vs
If the value of the Senki square wave is set to a value that is approximately the effective value of , an alternating current signal is apparently applied to the display panel, and the life of the display element is maintained. and ζ, the voltage Vuo-vCOM of the square wave is lower than l V JIMAX 1, and the power supply voltage V DD -V aa is lower than the conventional case shown in FIG. It is achieved.By the way, what does it look like visually?
In terms of images, the voltage applied to a certain pixel is conventionally
The video signal is Voo, but in this case (Voo
-Vco+Vs)/2 and 1 to 9, the contrast deteriorates somewhat. However, V DD−V aoM
What about when zo?In a panel where the signal voltage retention time at the 0 display pixel is long, the voltage of the pixel is v
Although it is 1/2, it can be displayed sufficiently.

Now, if the level of the square wave is close to the pedestal level of the video signal Va or the threshold voltage of the display element used, then the contrast on the square wave side is V D
It can be seen that although the black level does not change in the same way as when D-V coM=o, the effect as an alternating current and the contrast in the pixels are clearly the same as above. At this time, when a guest/host liquid crystal channel is actually used as a display element, the required power supply voltage VoD-Vl decreases by nearly 3V, and power consumption can be significantly reduced. Moreover, the apparent contrast is almost the same as in the conventional case.

FIG. 3 shows another embodiment of the present invention, in which a video signal Va is used on the positive potential side and a square wave is used on the negative potential side with respect to the common voltage V 66M. It is exactly the same as the case shown in the figure.

FIG. 4 also shows yet another embodiment of the present invention, in which a signal with one waveform clipped is input.

Here, by setting the clipping voltage to a surface voltage value such that the voltage-transmission (t or brightness characteristic) value of the display element used in #1 is 70 to 90, the contrast can be further improved. It is almost the same as the conventional one.However, the required voltage drop is less than 3V, and the reduction in power consumption is the same as 2.3.
Although it is not the case in the figure, it is quite effective.

Here, we have shown the case of mixing every other field, but
It doesn't matter if it is every l frame.

As described above, according to the present invention, as the video signal input (to the sampling circuit) of the display device, the video signal and the square wave (or the signal obtained by clipping a part of the video signal) are input every other field or every other frame. )t- By using alternating waveforms, the life of the display element is long,
In addition, it is possible to provide an excellent display with low power consumption and no significant adverse effect on contrast.

The level of the square wave is close to the pedestal level of the video signal or the threshold voltage of the display element, and the clip level is the value that is close to the maximum value of the transmittance or brightness characteristics of the display element used. It is desirable that the potential is 70 to 90 degrees.

[Brief explanation of drawings]

FIG. 1 shows a conventional signal waveform, and FIG. 2.3.4 shows an embodiment of the signal waveform according to the present invention. V oD * va, a * *Power supply voltage vCo' -@
@ 1111 common voltage vI10. Video signal voltage or higher

Claims (1)

[Claims] (1) In a display 1ljt in which a video signal is tempered and a signal voltage is applied to each pixel, one field is squared with the video signal every nine frames as a video signal input to a sampling circuit. A display device characterized by alternately applying signals obtained by clipping a part of a wave or a video signal. (2) The potential of the square wave is approximately equal in absolute value to the pedestal level t of the video signal or the threshold level potential of the display element.
The display device described in section 1). (:l, The clipping voltage of the signal obtained by clipping the video signal is determined when the transmittance (t or luminance) is between 70 and 90 in the voltage-transmittance characteristic (i or brightness characteristic) of the element used. A patented device characterized in that the voltage is such that