JPH0535212A - Liquid crystal driving method - Google Patents

Abstract

PURPOSE:To improve the contrast of a liquid crystal panel by applying an equal voltage to both terminals of respective liquid crystal picture elements of the liquid crystal panel during the blanking period of a vertical synchronizing signal when a large-sized simple matrix of one-screen constitution is driven. CONSTITUTION:Although a control circuit outputs the vertical synchronizing signal LVS, data LD, and a horizontal synchronizing signal LHS so as to drive the liquid crystal panel of one-screen constitution, 520 pulses of the horizontal synchronizing signal LHS are outputted in one vertical synchronizing period; and 480 pulses are outputted in an effective data period D and 40 pulses are outputted in the vertical blanking period C. In this case, a signal DOFF indicating the vertical blanking period of the vertical synchronizing signal LVS is inputted to hold the output voltages of the output voltages of a segment-side and a scanning-side driver circuit at the same potential in the vertical blanking period of the vertical synchronizing signal LVS. Therefore, no voltage is applied to both sides of each liquid crystal picture element in the vertical blanking period, so even when the 520 pulses of the horizontal synchronizing signal LHS are outputted in one vertical synchronizing period, a contrast which is equivalent to 1/480 duty driving can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a simple matrix type liquid crystal driving method without screen division, which is mainly used as a display for information terminal equipment and the like.

[0002]

2. Description of the Related Art An embodiment of a conventional liquid crystal driving method will be described below with reference to the drawings.

FIG. 1 is an example showing a liquid crystal drive circuit configuration. In the figure, reference numeral 1 is an information terminal device such as a personal computer, which takes out a clock signal, a data signal, a horizontal synchronizing signal and a vertical synchronizing signal for a CRT and controls the control circuit 2.
To enter. The control circuit 2 converts the CRT clock signal, data signal, horizontal synchronizing signal, and vertical synchronizing signal into a liquid crystal driving clock signal, data signal, horizontal synchronizing signal, and vertical synchronizing signal, respectively. A circuit other than the above signals necessary for driving the liquid crystal, that is, a control signal for AC driving the liquid crystal is also generated by this circuit. Reference numeral 3 is a power supply circuit for driving the liquid crystal, and this output voltage and the output signal of the control circuit 2 are connected to a segment side driver circuit 4 and a scanning side driver circuit 5, respectively.
The output of the circuit is connected to the liquid crystal panel 6. The liquid crystal panel 6 is a simple matrix type liquid crystal panel having a single screen configuration of 640 columns and 480 rows without screen division.

FIG. 2 is an operation waveform diagram of the liquid crystal drive circuit shown in FIG. In the figure, (a) VS,
(B) D and (c) HS are a CRT vertical synchronizing signal, data, and horizontal synchronizing signal output from the information terminal device 1 to the control circuit 2, respectively, and are horizontal synchronizing during one vertical synchronizing period. 520 signals are included. 480 out of 520
The 40 pieces are output during the valid data period (B period in FIG. 2), and the remaining 40 pieces are output during the vertical blanking period (A period in FIG. 2). (D) LVS, (e) LD, (f) LHS
Is a vertical synchronizing signal for driving the liquid crystal panel 6 having a single screen output from the control circuit 2,
Data and horizontal sync signals. Again, 520 horizontal sync signals are included in one vertical sync period, of which valid data is valid.
480 in the data period (D period in FIG. 2) and 40 in the vertical blanking period (C period in FIG. 2). (G) is an example of a voltage waveform applied across both ends of each liquid crystal pixel of the liquid crystal panel 6, and a voltage is applied to each liquid crystal pixel even during the vertical blanking period.

[0005]

When the liquid crystal panel 6 is driven by the voltage averaging method, which is a general liquid crystal driving method of the simple matrix type, the maximum value αmax of the ratio of the selected pixel voltage and the non-selected pixel voltage is the liquid crystal. It becomes one of the indexes for determining the contrast of the panel 6, and the larger the αmax is, the higher the contrast can be obtained.

In the voltage waveform as shown in FIG. 2G, the maximum value αmax of the ratio of the selected pixel voltage to the non-selected pixel voltage of the liquid crystal panel 6 is 1/520 duty drive value,
That is, αmax = 1.0448. However, in this conventional example, since the liquid crystal panel 6 has 640 columns and 480 rows, it is desirable that αmax is a 1/480 duty drive value, that is, αmax = 1.0467, but 1/520 duty is actually used. There is a problem that the display is low in contrast due to the tee driving.

It is an object of the present invention to provide a liquid crystal driving method that solves the above problems.

[0008]

In order to solve the above problems, the present invention provides a segment side driver circuit and a scan side driver circuit connected to a simple matrix type liquid crystal panel having a single screen structure, and the above two types. It is composed of a control circuit connected to a driver circuit and a power supply circuit for driving the liquid crystal, and the control circuit supplies a clock signal for CRT, a data signal, a horizontal synchronizing signal and a vertical synchronizing signal for the liquid crystal. A circuit for converting into a clock signal, a data signal, a horizontal synchronizing signal, and a vertical synchronizing signal, and also generating a control signal other than those mentioned above necessary for driving the liquid crystal, during the vertical blanking period from the control circuit. The same voltage is applied to both ends of each pixel of the liquid crystal panel.

[0009]

According to the above-described structure, the present invention does not apply a voltage across each liquid crystal pixel during the vertical blanking period, so that even if 520 horizontal synchronizing signals are included in one vertical synchronizing period,
It is possible to obtain a contrast equivalent to 1/480 duty drive.

[0010]

EXAMPLE A liquid crystal driving method according to an example of the present invention,
Hereinafter, description will be given with reference to the drawings.

The circuit configuration diagram of the present invention is the same as that of the conventional example (FIG. 1), and a detailed description thereof will be omitted. The difference from the conventional example is that the control circuit 2 supplies a clock signal, a data signal, a horizontal synchronizing signal, and a vertical synchronizing signal for a CRT to a liquid crystal driving clock signal, a data signal, and a horizontal synchronizing signal, respectively. , While converting to vertical sync signal,
It outputs a control signal for AC driving the liquid crystal and a signal indicating the vertical blanking period, and the segment side driver circuit 4,
This is a point to be inputted to each of the scanning side driver circuits 5.

FIG. 3 shows an operation waveform diagram of one embodiment of the present invention shown in FIG. In the figure, (a) VS,
(B) D and (c) HS are a CRT vertical synchronizing signal, data, and horizontal synchronizing signal output from the information terminal device 1 to the control circuit 2, respectively, and are horizontal synchronizing during one vertical synchronizing period. 520 signals are included. 480 out of 520
The 40 pieces are output during the valid data period (B period in FIG. 3), and the remaining 40 pieces are output during the vertical blanking period (A period in FIG. 3). (D) LVS, (e) LD, (f) LHS
Is a vertical synchronizing signal for driving the liquid crystal panel 6 having a single screen output from the control circuit 2,
Data and horizontal sync signals. Again, 520 horizontal sync signals are included in one vertical sync period, of which valid data is valid.
480 in the data period (D period in FIG. 3) and 40 in the vertical blanking period (C period in FIG. 3). (G) DOF
F is a signal indicating the vertical blanking period of LVS. By inputting this signal, the output voltage of the driver circuits 4, 5 on the segment side and the scanning side becomes the same voltage during the vertical blanking period of LVS. To do. As a result, no voltage is applied across the pixels of the liquid crystal panel 6 during the vertical blanking period. Segment side and scan side drivers-circuits 4, 5
A specific means for making the output voltage of the same voltage the same is, for example, as the segment side driver circuit 4 TM manufactured by TI
If S57207 is used and TMS57202 manufactured by TI is also used as the scanning side driver circuit 5, a circuit for making the output voltage of both drivers the same voltage is built in. (H) is an example of a voltage waveform applied between both ends of each liquid crystal pixel of the liquid crystal panel 6 when (g) DOFF is used, and a voltage is applied between both ends of each liquid crystal pixel during the vertical blanking period. Is not applied.

When driven by the circuit configuration as described above, the maximum value αmax of the ratio between the selected pixel voltage and the non-selected pixel voltage of the liquid crystal panel 6 is a value equal to 1/480 duty αmax =
Since it becomes 1.0467, driving with high contrast becomes possible.

In this embodiment, a driver circuit manufactured by TI is used as a means for keeping the output voltages of the segment side and scan side driver circuits 4 and 5 at the same voltage during the vertical retrace blanking period of LVS. However, any driver circuit having an equivalent function may be used.

Further, in this embodiment, a case has been described in which a 640 × 480 dot panel is used as the liquid crystal panel 6, and 520 horizontal synchronizing signals are included in one vertical synchronizing period, but the liquid crystal panel 6 has 640 × 400 dot. It is needless to say that the same effect can be obtained when using a panel and including 401 or more horizontal synchronizing signals in one vertical synchronizing period.

[0016]

As described above, according to the present invention, during the erasing period of the vertical synchronizing signal LVS for driving the liquid crystal, the voltage applied to both ends of each liquid crystal pixel is the same voltage, so that one vertical synchronizing period is provided. Even with 520 horizontal sync signals, a liquid crystal display with a contrast equivalent to 1/480 duty can be realized, which is very effective in improving the display quality of the liquid crystal panel.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a liquid crystal driving method according to an embodiment of the present invention.

FIG. 2 is a voltage waveform diagram of each part according to a conventional liquid crystal driving method.

FIG. 3 is a voltage waveform diagram of each part according to the liquid crystal driving method of the present invention.

[Explanation of symbols]

 1 information terminal equipment 2 controller circuit 3 power supply circuit 4 segment side driver-circuit 5 scanning side driver-circuit 6 liquid crystal panel

Claims (1)

Claim: What is claimed is: 1. A segment-side driver circuit and a scanning-side driver circuit connected to a simple matrix type liquid crystal panel having a single screen structure, and a controller connected to the two types of driver circuits. A control circuit and a liquid crystal driving power supply circuit, and the control circuit supplies a CRT clock signal, a data signal, a horizontal synchronizing signal and a vertical synchronizing signal to the liquid crystal clock signal, a data signal, A circuit for converting into a horizontal synchronizing signal and a vertical synchronizing signal and also generating a control signal other than the above which is necessary for driving a liquid crystal.
A method for driving a liquid crystal, characterized in that the same voltage is applied to both ends of each pixel of the liquid crystal panel during a vertical blanking period from the circuit.