JPH05265406A - Matrix electrode driving device for liquid crystal display panel - Google Patents

Abstract

PURPOSE:To provide the matrix electrode driving device for the liquid crystal display panel which drives a common electrode by inversion with small electric power. CONSTITUTION:This device consists of a 1st switch part 3-1 which is arranged between a driving line group 1-1 of the common electrode and a 1st common electrode driving part 5-1 and turns off only for a specific period from the switching timing of the polarities of driving signals outputted by the 1st and 2nd common electrode driving parts 5-1 and 5-2 at the time of the polarity switching, a 2nd switch part 3-2 which is arranged between a driving line group 1-2 of the common electrode and a 2nd common electrode driving part 5-2 and turns off for the same period simultaneously with the 1st switch part 3-1, and plural 3rd switch parts 2 which are provided, pair by pair, between the driving line group 1-1 and driving line group 1-2 and turn on while the switch parts 3-1 and 3-2 are OFF.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode driving device for a liquid crystal display panel, and more particularly to a matrix electrode driving device for a liquid crystal display panel which performs electrode driving of an active matrix driving system with low power.

A liquid crystal display panel is a flat panel type display device having both low power consumption and low voltage operation as compared with other display devices, and due to this characteristic, it is initially used for a clock, a calculator,
Subsequently, its applications are expanding to home appliances, in-vehicle devices, personal computers and word processors. The electrode structure for driving the liquid crystal element of the liquid crystal display panel,
There are segment electrodes, fixed pattern electrodes and matrix electrodes.

The matrix electrode is used when displaying an arbitrary pattern, and is composed of a plurality of scanning row electrodes formed on one substrate and a plurality of signal column electrodes formed on the other substrate. Character display, graphic display, and video display are performed by selectively applying a voltage to an arbitrary intersection (pixel) formed by these scanning row electrodes and signal column electrodes.

This is the structure of the matrix electrodes in the general multiplex drive system, whereas in the active matrix drive system in which a switching element is added to each pixel, the scanning row electrodes and the signal column electrodes are switched. The electrodes are formed on the same substrate surface via the element, and the electrodes are formed over the entire surface of the other substrate surface.

For the switching element, for example, a conductive layer, an insulating layer and an amorphous Si thin film are deposited on a glass substrate by vapor deposition.
A-Si formed by sputtering and etching
Thin film transistor (TFT: Thin Film Tr)
Anistor, hereinafter referred to as TFT) is used.
In the active matrix driving method using TFTs, a plurality of scanning row electrodes are sequentially scanned in a line-sequential method, all the TFTs on one scanning row electrode are simultaneously brought into a conductive state at a time, and in synchronization with this scanning. A signal charge corresponding to the signal supplied to the signal column electrode is supplied to the capacitor connected to the TFT.

In this way, the T provided for each pixel is
The FT separates each pixel electrode independently to prevent crosstalk, and the capacitor accumulates the signal charge for one frame time to improve the performance such as contrast and response of the liquid crystal display panel.

[0007]

2. Description of the Related Art With the recent miniaturization of computer systems, further miniaturization and lower power consumption of liquid crystal display panels are required. Therefore, it is necessary to reduce the power consumption of the common electrode for driving the switching element even in the active matrix driving method.

Therefore, from the conventional driving method in which the voltage applied to the common electrode in the matrix electrode is constant, a method has been proposed in which the common electrode is divided into two systems and the voltages applied to the pair of common electrodes are inverted to each other. ing.

According to this method, the power consumption is reduced by reducing the drive voltage of the signal column electrode which consumes the most current, and the power consumption of the entire liquid crystal display panel is reduced, while the drive power of the common electrode is reduced. Will increase.

Further, in order to set the common electrode, which is equivalently a capacitive load, to a predetermined voltage in a short time, the reversal drive of the common electrode is performed by a high speed / high output OP amplifier (operational amplifier).
Is done using. Therefore, the charging / discharging current of the common electrode increases as the number of times of inversion driving increases. In particular, this charge / discharge current becomes maximum in the case of one line inversion.

The charging / discharging current is usually charged from the positive power source and discharged to the negative power source or the ground. This is the same when the common electrode is divided into a plurality of parts, for example, when two drive lines of the common electrode are commonly connected and driven.

[0012]

As described above, in the conventional matrix electrode driving device for the liquid crystal display panel, the driving current for inverting the voltage applied to the common electrode is large, and the power consumption of the common electrode is increased. There was a problem to do.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a matrix electrode driving device for a liquid crystal display panel that drives a common electrode in reverse with low power.

[0014]

FIG. 1 illustrates the principle of the present invention. In order to solve the above-mentioned problems, the present invention provides a pair of common electrode driving units 5-1 and 5-2 which periodically output drive signals of opposite polarities, and a pair of common electrode driving unit 5
-1, 5-2, a first drive line group 1-1 connected to one common electrode drive section 5-1 and a second drive line group connected to the other common electrode drive section 5-2. A matrix electrode driving device for a liquid crystal display panel comprising line group 1-2,
The pair of common electrode driving units 5 are arranged between the first driving line group 1-1 and the one common electrode driving unit 5-1.
-1, When switching the polarity of the drive signal output by 5-2,
A first switch section 3-1 that is turned off for a predetermined period from the switching timing, and the second drive line group 1-
2 and the other common electrode drive section 5-2, and a second switch section 3-2 which is turned off at the same time as the first switch section 3-1 at the same time as the first switch section 3-1; Between the first drive line group 1-1 and the second drive line group 1-2, and the first and second switch units 3-1 and 3 are provided.
And a plurality of third switch units 2 which are in the ON state while −2 is in the OFF state.

[0015]

According to the present invention, as shown in FIG. 1, when the polarities of the driving signals in the pair of common electrode driving sections 5-1 and 5-2 are switched, the first and second electrodes are switched for a predetermined period from this switching timing.
Switch sections 3-1 and 3-2 are turned off, and at the same time, a plurality of third switch sections 2 are turned on and connected to the first and second drive line groups 1-1 and 1-2, respectively. The charges are moved from the high potential electrode group of the common electrode group divided into a plurality of pairs toward the low potential electrode group.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. 2 to 4 show an embodiment of the present invention. 2 is an overall configuration diagram of a matrix electrode driving device for a liquid crystal display panel according to an embodiment of the present invention, FIG. 3 is a timing chart showing the operation of the matrix electrode driving device for a liquid crystal display panel shown in FIG. 2, and FIG. 4 is an explanatory diagram showing a state of a current flowing through a drive line of a common electrode of the matrix electrode drive device of the liquid crystal display panel shown in FIG. 3. FIG.

In FIG. 2, the matrix electrode driving device of the liquid crystal display panel includes a first and a second common electrode driving section 5-1.
, 5-2, a liquid crystal display panel 10, first, second, and third switch sections 3-1, 3-2, 2 and an inverter logic 16a.

The liquid crystal display panel 10 has an even scanning row electrode (gate bus) X _2n (n: natural number) or an odd scanning row electrode X _{2n + 1} and an nth signal column electrode Yn (data bus). TFT as a switching element at each intersection
_10a-2n or TFTs _{10a-2n + 1} are arranged. The gate of the TFT _10a-2n or the TFT _{10a-2n + 1} is connected to the scan row electrode X _2n or X _{2n + 1} , the drain is connected to the signal column electrode Yn, and each source is common. The equivalent capacitance C _{10 b-2n} or C _{10b-2n + 1 of the} electrode (pixel electrode group) is connected.

The scanning row electrode X _2n or X _{2n + 1} and the signal column electrode Yn are driven by signals supplied from a gate bus driving unit and a data bus unit, which are controlled by a control unit (not shown). Is.

The first common electrode drive section 5-1 is composed of a voltage follower OP amplifier 5a connected to the power supply input terminal 19, and its input side is a signal input terminal 15-1.
And the output side is connected to the input side of the second switch section 3-2 via the output line 21-1.

The second common electrode driving section 5-2 is composed of a voltage follower OP amplifier 5b connected to the power source input terminal 19, and its input side is the signal input terminal 1
5-2, the output side of which is connected to the input side of the first switch section 3-1 via the output line 21-2. Here, the signal input terminals 15-1 and 15-2 are respectively connected to the control section, and the OP amplifiers 5a and 5-2 are connected.
b is grounded.

The first switch section 3-1 is composed of an analog switch 3a, the output side of which is connected to the one end of the equivalent capacitance C _{10b-2n + 1} through the drive line of the common electrode via 1-2. Together with the analog switch 2a via the connection line 4-2.
Is connected to the input side of the third switch unit 2.

On the other hand, the second switch section 3-2 comprises an analog switch 3b, the output side of which is connected to the drive line of the common electrode via 1-1 and to the equivalent capacitance C _10b-2n , and is also connected. It is connected to the output side of the third switch section 2 via the line 4-1.

Further, the signal input terminal 16-2 is connected to the respective control terminals of the first and second switch sections 3-1 and 3-2, and the inverter logic 16a and the connecting line 16 are connected.
−1 is connected to the control terminal of the third switch unit 2.

Incidentally, in synchronization with the timing when the polarities of the output voltages of the OP amplifiers 5a and 5b are periodically inverted,
From the control unit through the signal input terminal 16-2, the first, second, third
A switch control signal is supplied to the switch units 3-1, 3-2, and 2 of. The switch control signal causes the on / off operation of the analog switches 3a and 3b and the on / off operation of the analog switch 2a to be alternately performed in reverse.

Further, the analog switches 2a, 3a,
3b is a circuit in which a pMOS and an nMOS are connected in parallel, and the MOS-FET is turned on or off at the same time to mechanically replace the relay switch.
It has a flat on-resistance characteristic.

Next, the operation of the matrix electrode driving device for the liquid crystal display panel according to this embodiment will be described with reference to FIGS. First, the first and second common electrode driving units 5-1 and
The case where 5-2 is directly connected to the drive lines 1-1 and 1-2 of the common electrode will be described.

A control unit (not shown) controls the frame synchronization signal (V
SYNC), a line synchronization signal (HSYNC) or a line synchronization signal is frequency-divided to generate a timing signal for AC conversion shown in FIG. Then, based on this timing signal, alternating current control signals of opposite polarities are generated as shown in (b), and the first common electrode drive section 5-1 is respectively supplied via the signal input terminals 15-1 and 15-2. , To the second common electrode driver 5-2.

Then, the first common electrode driving section 5-1 outputs the output signal indicated by the solid line in (c) to the common electrode driving line 1-1.
To the equivalent capacitance C _10b-2n of the common electrode. On the other hand, the second common electrode drive section 5-2 supplies the output signal indicated by the broken line to the equivalent capacitance C _{10b-2n + 1} of the common electrode via the drive line 1-2 of the common electrode.

Here, when the first common electrode driving section 5-1 outputs the low level signal indicated by a ₁ in (c),
The charge already accumulated in the equivalent capacitance C _10b-2n of the common electrode is discharged, and the discharge current (a _{3 of} (e)) corresponding to the change of the discharge voltage indicated by a ₂ of (d) is the first common electrode. It flows to the drive unit 5-1. This discharge current flows to the ground via the OP amplifier 5a.

On the other hand, at this time, the common electrode driving section 5-2 outputs a high-level signal (a _{4 of} (c)) of the opposite polarity to the common electrode driving section 5-1. _The charging current (a _{6 of} (e)) due to the charging voltage shown by ₅ flows into the equivalent capacitance C _{10b-2n + 1} of the common electrode, and the common electrode is applied with a predetermined voltage.

Next, the operation of the present embodiment in which the switch control signal is supplied from the control section to the first, second and third switch sections 3-1, 3-2, 2 will be described. From the control unit (f)
When a high level switch control signal as indicated by a ₇ in Figure 7 is supplied to the signal input terminal 16-2, this switch control signal is supplied to the first and second switch sections 3-1 and 3-2 as they are, The switch units 3-1 and 3-2 are turned on.
On the other hand, this switch control signal is the inverter logic 16
At a, the signal is inverted as shown by a ₈ in (f) to become a low level signal, and the third switch section 2 is turned off.

Then, the first common electrode driving section 5-1 outputs the low level output signal indicated by a ₁ to the output line 21- in (c).
1, the second switch unit 3-2 in the ON state, and the drive line 1-1 of the common electrode, the equivalent capacitance C _{10b-2n of the} common electrode.
Supply to.

On the other hand, the second common electrode driving section 5-2 outputs the high level output signal indicated by a ₄ to the output line 21- in (c).
2, and the equivalent capacitance C _{10b-2n + 1 of the} common electrode via the first switch section 3-1 in the ON state and the drive line 1-2 of the common electrode.
Supply to.

Then, when the switch control signal supplied to the signal input terminal 16-2 falls as indicated by a ₉ in (f), the first and second switch sections 3-1 and 3-2 are turned off. while the state, the switch control signal is a third switch section 2 becomes a high level signal is inverted as shown by a ₁₀ in the inverter logic 16a (f) is turned on.

Therefore, the discharge current from the equivalent capacitance C _10b-2n of the even-numbered common electrodes is equal to the drive line 1 of the common electrodes.
−1 through the connection line 4-1 and flows into the third switch unit 2. Then, this current flows from the connection line 4-2 to the drive line 1
It flows through −2 into the equivalent capacitance C _{10b-2n + 1} of the odd-numbered common electrode.

Next, a high level switch control signal signal
(A in (f)₁₁) Is supplied to the input terminal 16-2,
The first and second switch sections 3-1 and 3-2 are turned on again.
Then, the third switch unit 2 is turned off. Because
And the equivalent capacitance C of the common electrode described above._10b-2nDischarge from
Current is a switch control signal supplied to the input terminal 16-2.
Only during the period of low level signal of the inverter logic
The high level signal inverted by 16a is supplied to the switch unit 2.
Period to be paid (a in (f)₁₆), A of (g) ₁₂Indicated by
It flows like a stream.

Therefore, the equivalent capacitance C _{10b-2n + 1} is charged by the discharge current of the equivalent capacitance C _10b-2n and its potential rises, so that the first common electrode driving section 5-1 is shown in FIG.
The charging current as shown by the chain line a ₁₃ in FIG.
Only the charging current shown in ₁₄ is required.

Incidentally, a _{15 in} (g) is the equivalent capacitance C _10b-2n of the even _- numbered common electrodes and the equivalent capacitance C of the odd _- numbered common electrodes described above.
The charge / discharge relationship with _{10b-2n + 1} is reversed, that is, the equivalent capacity C
The discharge current when charges flow from _{10b-2n + 1} to the equivalent capacitance C _10b-2n is shown.

After that, the first common electrode driving section 5-1 and the second common electrode driving section 5-1
Every time the output voltage of the common electrode driving section 5-2 is inverted, the above operation is repeated in synchronization with the timing.
At this time, a charging / discharging current as shown in FIG. 4 flows through the drive lines 1-1 and 1-2 of the common electrode.

In this way, the first common electrode section 5-1
And when the output voltage of the second common electrode section 5-2 is inverted,
In synchronization with this timing, the first and second switch units 3-
Since 1 and 3-2 are temporarily turned off and the third switch section 2 is turned on, the equivalent capacitance C of the common electrode is
_The charge is moved from the high potential side to the low potential side between _10b-2n and the equivalent capacitance C _{10b-2n + 1,} and the potential of the common electrode is improved.

Therefore, the first common electrode driver 5-1
And the load on the second common electrode driver 5-2 is reduced,
It is possible to reduce the power consumption for driving the liquid crystal display panel. In addition, in the present embodiment, the first to third switch units 3-1, 3-2,
Although an analog switch was used for 2, other elements such as F
ET is fine. Further, although the liquid crystal display panel is of the TFT type, it may be of a type having a common electrode or a functionally equivalent type in terms of structure.

[0043]

As described above, according to the present invention,
When switching the polarity of the drive signal in the pair of common electrode drive units, the first and
At the same time as turning off the second switch unit,
Of the common electrode group connected to the first and second drive line groups and divided into a plurality of pairs to move the charges from the high potential electrode group to the low potential electrode group. Since the potentials of these electrode groups are increased, the load on the common electrode driving unit can be reduced, and the power consumption for driving the matrix electrodes of the liquid crystal display panel can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is an overall configuration diagram of a matrix electrode driving device of a liquid crystal display panel according to an embodiment of the present invention.

3 is a timing chart showing signal states of respective parts of the matrix electrode driving device of the liquid crystal display panel shown in FIG.

4 is an explanatory diagram showing a state of a current flowing through a drive line of a matrix electrode driving device of the liquid crystal display panel shown in FIG.

[Explanation of symbols]

 1-1, 1-1 ... Drive line 2 ... Third switch 3-1 ... First switch section 3-2 ... Second switch section 5-1 ... First common electrode drive section 5-2 ... 2 common electrode drive unit 10 ... Liquid crystal display panel

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuhiko Kishida 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited

Claims (3)

[Claims] 1. A pair of common electrode driving sections (5-1, 5-2) which periodically output driving signals of opposite polarities, and a pair of common electrode driving sections (5-1, 5-2). Of the first drive line group (1-1) connected to one common electrode drive section (5-1) and the second drive line group connected to the other common electrode drive section (5-2) A matrix electrode driving device for a liquid crystal display panel, comprising: a line group (1-2), comprising: the first drive line group (1-1) and the one common electrode driving section (5-1). A first switch unit (which is disposed between the switch units and is turned off for a predetermined period from the switching timing when the polarity of the drive signal output by the pair of common electrode driving units (5-1, 5-2) is switched. 3-1), the second drive line group (1-2) and the other common electrode drive section (5-2), and the first switch. (3-1) at the same time the second switching section in the off state by the same time period and (3-2), the first driving line group (1-1) and the second drive line group (1
-2) and a pair of third switch sections (2) that are provided in pair with each other and are in the ON state while the first and second switch sections (3-1, 3-2) are in the OFF state. ) A matrix electrode driving device for a liquid crystal display panel, comprising: 2. The first, second and third switch parts (3-
The matrix electrode driving device for a liquid crystal display panel according to claim 1, wherein 1, 3-2 and 2) are semiconductor elements. 3. The pair of common electrode driving units (5-1, 5)
2. The matrix electrode driving device for a liquid crystal display panel according to claim 1, wherein the areas of the common electrodes of (2) are formed to be substantially equal.