JPS6231894A - 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 Field of the Invention The present invention relates to a liquid crystal drive circuit that can be used in display devices such as hand belt computers and word processors.

Conventional technology] In display devices such as computers and word processors,
Immediately after the power is turned on, the display frame memory (RA
Since the content of M) is undefined, if it is displayed as is, a random pattern will be displayed on the screen, which is not desirable.

Therefore, display blanking is usually performed to erase the screen. Blanking is also performed when the main body is temporarily stopped and the display is turned off when the display is not needed, such as when the printer is operating, to reduce power consumption.

In a drive circuit used in a liquid crystal display device driven in a time-division manner, display blanking is performed using the following method. FIG. 3 is a typical block diagram of a conventional liquid crystal drive circuit, in which the display data in the display memory 1 is read out by the controller 2 in synchronization with the scanning electrode driver 6, converted from parallel to serial, and sent to the signal electrode driver 3. The display data aH+m is sent and displayed here.
, a L l" (usually "H" is the liquid crystal lighting.

(Lo corresponds to turning off) is applied to the liquid crystal panel 4, and the liquid crystal turns on and off according to the display data.

FIG. 4 shows the signal electrode driver 3 in more detail. The display data stored in the latch 7 via the shift register 6 is sent to the waveform selector 10 via the blanking circuit 8 and the level shifter 9. ′ of the data displayed in
Either the selected waveform 11 (lighting waveform) or the non-selecting waveform 12 (lighting out waveform) is selected depending on the signals H" and "L" and sent to the liquid crystal panel. Here, the blanking circuit 8 It is composed of one AND gate, and if the blanking signal 13 is "L" (display state), the latch 7
The data of “H” is sent to the level shifter 9 as is.
” (blanking state), all outputs of the blanking circuit 8 will be “L” regardless of the data of the latch 7, so all outputs of the waveform selector 1o will be the non-selected waveform 12.
The LCD will turn off.

Here, the waveform generating circuit 16 inputs “H” and “L” of the AC signal 14 input via the level shifter 9.

Drive voltage 16 (VDD>Vz>V3>Vs
The selected waveform 11. A non-selected waveform 12 is being created. An example of the circuit configuration is shown in FIG.

In the figure, 17 to 20 are analog switches, and when the control terminal is "H", the input and output are conductive, and the output is "L".

It is a circuit element that shuts off when . 16 is a driving voltage, which is a four-value DC voltage of VDD -V5 .V, 2.Vs I). Now, if the AC signal 14 input via the level shifter 9 is "H", the analog switch (3
1) 17 and the analog switch (S5) 19 are electrically connected, and the others are cut off. Therefore, as the selection waveform 11, VDD
However, v2 is output as the non-selected waveform 12. Next, when the AC signal 14 becomes “L”, the analog switch (S
2) 1B+! :The analog switch (84) 20 is conductive, and the others are cut off.

Therefore, v5 is output as the selected waveform 11, and v3 is output as the non-selected waveform 12. In this way, the alternating current signal 14
A selection waveform 11 and a selection waveform 12 are created in accordance with the above.

Problems to be Solved by the Invention However, in the above configuration, even though the liquid crystal is turned off, it is in a non-selected state and displays at a low brightness, so although the power consumption of the liquid crystal panel is reduced, It cannot be zero. Furthermore, since the blanking circuit 8 requires a large number of gates, the circuit scale of the driver also increases.

In order to prevent this, a gate may be provided at the input section of the shift register 6 to form a blanking circuit, but in this case, there is a problem that the response time is slightly delayed.

The present invention aims to solve these problems,
It is an object of the present invention to provide a liquid crystal drive circuit that can reduce the power consumption of a liquid crystal panel to zero when erasing a display with a simple circuit configuration.

Means for Solving the Problem In order to solve this problem, the present invention provides the same potential for all outputs of both the signal electrode driver and the scanning electrode driver, so that the voltage is applied to the display dots of the liquid crystal panel. The liquid crystal display is erased by setting the potential difference between the two to zero.

As a result, according to the present invention, no potential difference is applied to the liquid crystal dots, so the power consumption of the liquid crystal panel becomes zero.

Embodiment FIG. 1e) is a block diagram of a signal electrode driver of a liquid crystal drive circuit according to an embodiment of the present invention, in which a shift register 6
, latch 7, level shifter 9. The waveform selector 10 is the same as the conventional example. The waveform generating circuit 21 is different from the conventional example in that the blanking signal 13 is replaced by the AC converting signal 14.
The signal is also applied to the waveform generation circuit 21 via the level shifter 9. When the blanking signal 13 is “Lo” (
In the display state), one of the outputs of the waveform creation circuit 21, the V person waveform 22, is the selected waveform, and the other one, the V output, is the selected waveform.

The waveform 23 becomes a non-selected waveform, and the output of the waveform selector 1° becomes a selected or non-selected waveform depending on the display data, so that the liquid crystal panel performs lighting-on/off display according to the display data. Next, when the blanking signal 13 becomes "H" (blanking state), both the V person waveform 22 and the V waveform 23 are at the same potential, for example, VDD potential (one of the power supply voltages of the driver). A waveform generating circuit 21 is configured, so that the output of the waveform selector 1o is always at the VDD potential regardless of the display data.

Similarly, FIG. 1(b) is a block diagram of the scanning electrode driver, and similarly, the blanking signal 13 is the same signal as shown in the signal electrode driver, but is passed through a level shifter 24 to form a waveform. When the blanking signal 13 is "L", a normal scanning signal is sent to the waveform selector 28, but 'H' is applied to the generation circuit 26.
’, the Vmu waveform 25. The waveform generating circuit 26 is configured so that all of the Va waveforms 27 have the same potential as in the signal electrode driver, for example, in this case, the vDD potential, so the output of the waveform selector 28 is always at Vl regardless of the scanning timing. I) Potential.

Therefore, the output voltage of the signal electrode driver 3 and the scanning electrode driver 6 are applied to the liquid crystal dots of the liquid crystal panel 4 shown in FIG.
However, according to the circuit of the present invention, in the blanking state, both are at the same potential, so the voltage applied to the liquid crystal dot is zero, and the liquid crystal does not light up at all. Its power consumption becomes zero.

FIG. 2 shows a circuit diagram specifically illustrating the waveform generating circuit 21 of the signal electrode driver according to an embodiment of the present invention. In the figure, 29 to 33 are analog switches. Same as used. Now, when the blanking signal 13 is "L", the analog switch 5533 is always cut off, and if the AC conversion signal 14 is "Ho", then v, =v
DD, vB=Y2, if “L- then Vi=Vs + V
! +=Vs (However, L, VDD > V2 > Vs >
Vs), V, waveform 22°VB waveform 23 is the selected and non-selected waveform. Next, blanking signal 1
3 is 'H', only the analog switches (81) 29 and (85) 33 are in the conductive state and the others are in the cut-off state.
It can be seen that l"v!l"VDD. Note that it is easily understood that the waveform generation circuit 25 of the scanning electrode driver can also be configured in a similar manner.

Effects of the Invention As can be seen from the above explanation, the present invention makes it possible to completely erase the liquid crystal display by setting the outputs of the signal electrode driver and the scanning electrode driver to the same potential during blanking. An excellent effect is obtained in that the power consumption of the liquid crystal panel can be completely reduced to zero, and the circuit configuration for this purpose can also be made very simple.

[Brief explanation of the drawing]

FIG. 1(2L) is a block diagram of a signal electrode driver according to an embodiment of the present invention; FIG. 1(b) is a block diagram of a scanning electrode driver;
FIG. 2 is a circuit diagram of a waveform generation circuit of a signal electrode driver according to an embodiment of the present invention, FIG. 3 is a block diagram of a liquid crystal display device, FIG. 4 is a block diagram of a conventional signal electrode driver, and FIG. f) C in the circuit diagram of a conventional waveform creation circuit. 1...Display memory, 2...Controller, 3...Signal electrode driver, 4...
Liquid crystal panel, 6...Scanning electrode driver, 6...
...Shift register, 7...Latch, 8.
...Blanking circuit, 9.24 ...Level shifter, 10.28 ... Waveform selector, 1
1...Selected waveform, 12...Non-selected waveform, 13...Blanking signal, 14...
・AC signal, 16°21.25... Waveform creation circuit, 16... Drive voltage, 17~20.29~
33...Analog switch, 22, 26...
...Vm waveform, 23.27...vB waveform. Name of agent: Patent attorney Toshio Nakao and 1 other person11
Figure (Oshin Figure 2, /3., /4 72 sink issue Intersecting vaporization bond issue Figure 3 Figure 4

Claims (1)

[Claims] It is equipped with a liquid crystal display panel, a scanning electrode driver, a signal electrode driver, and a blanking signal input terminal driven in a time division manner, and when the blanking signal is operated, all liquid crystal drive outputs of the scanning electrode driver and the signal electrode driver are provided. A liquid crystal drive circuit configured to completely turn off the liquid crystal display panel by setting potentials at the same potential and zeroing a potential difference applied to display dots of the liquid crystal display panel.