JP2002023708A - Driving circuit, display device and driving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such problem that it is needed to add a potential modulating circuit or the like to peripheral circuits in order to reduce the driving power and the scale of circuits is made large in a display device in which a display material such as liquid crystal is alternatively driven by using an active matrix having switching elements and pixel electrodes in a matrix shape. SOLUTION: This driving circuit is provided with a semiconductor switching element having C-MOS (complementary metal-oxide semiconductor) structure which receives the feeding of power from a picture signal wiring and which samples the potential of a picture signal and capacitances provided among respective gate electrodes of the P-channel transistor and the N-channel transistor of the semiconductor switching element having the C-MOS structure and the picture signal wiring.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a sample-and-hold circuit using a switching element such as a thin film transistor (hereinafter referred to as a TFT) having a C-MOS structure, and an active circuit having the switching element and pixel electrodes in a matrix. Regarding a method for driving a display device that performs image display by alternating current driving a display material such as a liquid crystal using a matrix, a drive circuit, a display device, and a drive of the display device for the purpose of reducing drive power and simplifying the drive circuit Method etc.

[0002]

2. Description of the Related Art Conventionally, in a liquid crystal display device, driving methods such as opposing inversion driving, synchro gate driving, and capacitive coupling driving have been devised for the purpose of reducing the driving voltage and the power consumption of a driving circuit.

[0003] Hereinafter, as an example, an opposing inversion driving method using a driving circuit used in a conventional liquid crystal display device or the like will be described.

FIG. 3 shows timings of driving waveforms in the conventional opposing inversion driving method. FIG. 4 is an equivalent circuit of an image display portion in which TFTs and pixel electrodes are arranged in a matrix. In FIG. 3, reference numeral 1 denotes a voltage waveform applied to the gate electrode of the pixel electrode TFT, and 2 denotes a pixel electrode TFT.
Is a voltage waveform applied to the image signal line, and 3 is a voltage waveform applied to the counter electrode for holding the liquid crystal material between the pixel electrode and the pixel electrode. However, FIG. 3A shows the n-th field, and FIG. 3B shows the (n + 1) -th field (n: positive integer)
The waveforms in the case of FIG.
Description will be made with reference to FIG. In FIG. 4, reference numeral 4 denotes a gate electrode of a pixel electrode TFT, 5 denotes an image signal wiring, 6 denotes a counter electrode, and 7 denotes a pixel electrode. Although not shown,
Each image signal wiring 5 is provided with an input signal wiring for inputting an image signal and a semiconductor switching element for sampling the signal.

The operation of the liquid crystal display device configured as described above will be described below.

First, the voltage waveform 2 applied to the image signal wiring 5 is transmitted to the pixel electrode 7 when the voltage 1 applied to the gate electrode 4 of the pixel electrode TFT 4 is at a high level, that is, when the TFT is turned on. Is done. Then, the gate electrode 4
Changes the potential of the counter electrode 6 at the moment when the voltage 1 applied to the TFT is at a low level, that is, when the TFT is turned off. By this operation, the signal voltage 3 held by the pixel electrode 7 changes. The amount of change 3 in the pixel electrode potential at this time is ΔV *, the liquid crystal capacitance between the pixel electrode and the counter electrode is Clc, and the pixel T
Assuming that the stray capacitance between the gate electrode and the pixel electrode of the FT is Cgd and the amount of change in the counter electrode voltage is ΔVcom, ΔV * can be expressed by the following equation.

[0007]

ΔV * = {Clc / (Clc + Cgd)} × ΔVcom (1) As described above, by changing the potential of the counter electrode 6, the image signal voltage is effectively applied to the liquid crystal material by ΔV *. Can be done. This means that the image signal voltage can be input at a lower amplitude of ΔV * when the driving circuit is configured, and the driving power can be reduced by that much.

In the case where the synchro gate drive and the capacitive coupling drive method are used, a storage capacitor is provided in the pixel electrode and the storage capacitor electrode is changed, or the gate electrode potential is changed during the off period of the pixel TFT. The driving voltage is reduced, and the driving power is reduced.

[0009]

However, in the above-mentioned conventional configuration, the liquid crystal display device is driven in order to change the counter electrode or change the gate electrode during the off period of the TFT gate. In addition, it is necessary to add a potential modulation circuit to a peripheral circuit provided outside the image display portion, and there is a problem that the circuit scale becomes large.

An object of the present invention is to solve the above-mentioned conventional problems and to provide a drive circuit, a display device, and a method of driving the same which can reduce the drive voltage with the same configuration as a normal drive circuit. .

[0011]

In order to achieve the above object, a first aspect of the present invention (corresponding to claim 1) is to receive power supply of a predetermined input signal and sample the potential of the input signal. C—output to the image signal wiring as the potential of the image signal
A MOS switching semiconductor switching element, and the C-MO
A drive circuit comprising: a capacitor provided between a gate electrode of each of a P-channel transistor and an N-channel transistor of a semiconductor switching element having an S configuration and the image signal wiring.

Further, the second invention (corresponding to claim 2)
A driving circuit according to the first aspect of the present invention, a scanning signal wiring intersecting with the image signal wiring to form a plurality of grid areas, and the scanning circuit arranged in a matrix on the plurality of grid areas. A semiconductor switching element receiving power supply from a signal wiring and the image signal wiring; and a signal supplied from the image signal wiring via the semiconductor switching elements arranged in a matrix on the plurality of lattice regions. A pixel electrode for applying to the display material, and a counter electrode for holding the display material facing the pixel electrode, wherein a difference between a potential of a signal applied to the pixel electrode and a potential of the counter electrode is: And a potential difference between the potential of the predetermined input signal and a potential of the counter electrode.

Further, the third invention (corresponding to claim 3)
Is a driving method of a display device according to the second aspect of the present invention, wherein the potentials of the gate electrodes of the P-channel transistor and the N-channel transistor of the semiconductor switching element having the C-MOS configuration are changed at independent timings. And a step of applying a signal to the pixel electrode by changing a potential of the image signal.

A fourth aspect of the present invention (corresponding to claim 4)
Is P of the semiconductor switching element having the C-MOS configuration.
The channel transistor and the N-channel transistor
The present invention is characterized in that they are not turned on at the same time.

Further, a fifth aspect of the present invention (corresponding to claim 5)
The present invention is characterized in that the polarity of the voltage of the image signal input to the semiconductor switching element having the C-MOS configuration is inverted every field or every scanning line of the display screen.

A sixth aspect of the present invention (corresponding to claim 6)
According to the present invention, the absolute value of the voltage of the image signal is different for each polarity.

Further, a seventh aspect of the present invention (corresponding to claim 7)
Is P of the semiconductor switching element having the C-MOS configuration.
The potential of the image signal when the channel transistor is on
To Vs ⁺Semiconductor switching element having the C-MOS configuration
The image signal when the child N-channel transistor is on
Potential of Vs^-Then, the potential Vs of the image signal⁺Mark
When the pixel electrode is added,
The potential is high, and the potential Vs of the image signal is high.^-Where is applied
The potential between the pixel electrode and the counter electrode is
The present invention is characterized in that it is low.

The eighth invention (corresponding to claim 8)
In the above invention, the potential of the counter electrode is constant.

The ninth aspect of the present invention (corresponding to claim 9)
Is a medium which carries a program and / or data for causing a computer to execute all or a part of the functions of all or part of any of the second to eighth aspects of the present invention. A medium characterized by what is possible.

A tenth aspect of the present invention (corresponding to claim 10) is to cause a computer to execute all or a part of the functions of all or part of the second to eighth aspects of the present invention. , And / or data.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment) FIG. 1 shows an electric equivalent circuit of a display element of a TFT active matrix drive LCD which is a drive circuit and a display device according to an embodiment of the present invention. Each display element has a TFT 10 at the intersection of the scanning signal wiring 8 and the image signal wiring 9.
The N-channel TFT 11 and the P-channel TFT 12 having the MOS structure are connected, and the voltages applied to the N-channel TFT gate wiring 14 and the P-channel TFT gate wiring 15 are independently changed, so that the external input image signal wiring 13 The input image signal is sampled in a switch operation. The TFT 10 has a capacitance C between the gate and the source of the pixel TFT, which is the sum of the parasitic capacitance and the gate electrode of all the pixel TFTs on one image signal line as a parasitic capacitance.
gs16 and a parasitic capacitance Cgd20 between the gate electrode and the pixel electrode of the pixel TFT.

Further, as a capacitor formed intentionally, P
Channel TFT gate-source capacitance Cgsp17 and N
There is a channel TFT gate-source capacitance Cgsn18 and a liquid crystal capacitance Clc19. The P-channel TFT gate-source capacitance Cgsp17, the N-channel TFT gate-source capacitance Cgsn18, the liquid crystal capacitance Clc19.
In order to specifically configure the method, a method of forming a capacitance using a dielectric thin film between two conductive electrodes, a capacitor determined by the dielectric constant of a liquid crystal material, and the like are used.

Each of the above-mentioned element electrodes is provided with a scanning signal Vg on the scanning signal wiring 8, an image signal voltage Vsig on the external input image signal wiring 13, and C-
The selection signal Vgn is applied to the N-channel TFT gate wiring 15 of the MOS structure, the selection signal Vgp is applied to the P-channel TFT gate wiring 15, and the counter electrode 30 of the liquid crystal capacitor Clc19.
, A constant voltage determined as a design item is applied. The influence of the drive voltage via the parasitic or intentionally formed various capacitors appears on the image signal wiring 9 and the pixel electrode 31.

The operation of the TFT active matrix drive LCD, which is the drive circuit and the display device according to the embodiment of the present invention configured as described above, will be described below with reference to the drawings. The driving method of the present invention will be described.

First, FIG. 2 shows the scanning signal lines 8 and N of a certain field and the next field of the certain field.
The timing of the voltage waveform applied to the channel TFT gate wiring 14, the P-channel TFT gate wiring 15, and the pixel electrode 31 is shown. The Vs ⁺ and Vs ^- voltages are applied to the external input image signal wiring 13 while reversing the polarity for each field.

Assuming that the high level voltage of the waveform 21 applied to the scanning signal wiring 8 is VgH and the low level voltage is VgL, the state where VgH is applied to the gate electrode of the pixel TFT 10, that is, when the pixel TFT 10 is on, A signal obtained by sampling the voltage of the external input signal line 13 is applied to the image signal line 9 by the N-channel TFT gate voltage waveform 22 or the P-channel gate voltage waveform 23, and the voltage Vs ⁺ is applied to the pixel electrode 31 via the pixel TFT 10. or Vs ^- applied at.

Next, the operation will be described for each field of the image signal.

First, a certain field (the n-th field)
In the period, the voltage Vs ⁺
Is input. At the timing when this signal is sampled and transmitted to the image signal wiring 9, the C-MOS
The gate voltage of the P-channel TFT 12 of the switching circuit having the configuration is at the low level VpL, that is, the on state, and the gate voltage of the N-channel TFT 11 is at the low level VnL, that is, the off state.
Voltage 24 becomes Vs ⁺ . Next, a P-channel TFT 1
At the moment when the gate voltage of No. 2 is at a high level, that is, in the off state, the voltage rises to (Vs ⁺ + ΔVp) due to various capacitances.

The voltage ΔVp at this time can be expressed by the following equation.

[0031]

ΔVp = {Cgsp / (Cgsp + Cgs)} × (VpH−VpL) (2) Next, the voltage applied to the scan signal wiring 8 of the n-th field is the low level VgL, that is, the off state. Instantaneously, the voltage drops by ΔVlc due to the influence of the parasitic capacitance of the pixel TFT 10 and the like.

The voltage ΔVlc at this time can be expressed by the following equation.

[0033]

ΔVlc = {Cgd / (Clc + Cgd)} × (VpH−VpL) (3) Therefore, according to the above equations (1) to (3), in the scan of the odd-numbered field, an external input is made at Vs ^+. The signal voltage applied to the pixel electrode 31 is a voltage (Vs ⁺ + ΔVp−Δ).
Vlc) and the pixel TF until the next field
It is held in the liquid crystal capacitance of T10.

Next, in the next field th scanning of said certain th field, the voltage Vs to the external input signal lines 13 in the same manner as described above ^- signal is input. At the timing when this signal is sampled and transmitted to the image signal wiring 9, the gate voltage of the N-channel TFT 11 of the switching circuit having the C-MOS configuration is at the high level VnH, that is, the ON state, and the gate voltage of the P-channel TFT 12 is at the high level. Level VpH, that is, by being turned off,
Image voltage of the signal line 9 of this period, Vs ^- to become.

Next, at the moment when the gate voltage of the N-channel TFT goes to a low level, that is, the off state, the voltage drops to (Vs ^-- ΔVn) due to the influence of various capacitances.

The ΔVn voltage at this time can be expressed by the following equation.

[0037]

ΔVn = {Cgsn / (Cgsn + Cgs)} × (VnH−VnL) (4) Next, the voltage applied to the scanning signal wiring 8 in the (n + 1) th field is at the low level VgL, that is, in the off state. Even at the moment, the voltage drops by ΔVlc due to the influence of the parasitic capacitance of the pixel TFT 10 and the like.

As described above, in the scanning of the (n + 1) th field, the signal voltage input from the outside at Vs− is applied to the pixel electrode 31 by the voltage (Vs ⁻ −ΔVn−ΔVlc).
And is held in the liquid crystal capacitance of the pixel TFT 10 until the next field.

That is, when the amplitude inputted from the outside is | Vs ⁺
−Vs ⁻ | is applied to the pixel electrode 31 by | Vs ⁺ −Vs
⁻ + Vp + ΔVn | can be amplified and applied.

As described above, according to the embodiment of the present invention, each of the P-channel and N-channel of the switching element of the C-MOS configuration for sampling the external input signal, which is the driving circuit formed in the display device, is used. provided a capacitor between the gate electrode and the image signal lines to operate the P-channel TFT when the polarity inverted Vs + signal is input from the outside, Vs ^- when the signal is input N-channel TFT
By operating the independently without the need to add a potential modulation circuit to an external peripheral circuit for driving the display device, the amplitude inputted from an external display device is ^| Vs ⁺ -Vs - | AC signal, | Vs ⁺ −Vs ⁻ + ΔVp
+ ΔVn | can be amplified and applied.

In the embodiment, the P-channel TFT gate-source capacitance Cgsp17 and the N-channel TFT gate-source capacitance Cgsn18 have been described as intentionally formed capacitances.
May be used as a parasitic capacitance. Further, a storage capacitor may be provided on the drain side of the pixel TFT 10 to hold the voltage applied to the liquid crystal capacitor. Further, the voltage of the storage capacitor on the side opposite to the TFT drain may be arbitrary as long as it is at a certain level. Also, the switching element is not limited to the TFT,
Any semiconductor switching element having a MOS configuration may be used.

Although the drive circuit, the display device, and the drive method of the present invention have been described as being used for a liquid crystal display device in the embodiment, the present invention is not limited to this. , EL (electroluminescence) display and the like.

In the above description, the driving circuit, the display device, and the driving method of the display device according to the embodiment of the present invention have been described. However, the present invention relates to all or a part of the present invention. A medium that carries a program and / or data for causing a computer to execute all or a part of the function of the means. The medium is readable by a computer, and the program and / or data read therefrom cooperate with the computer. It may be realized as a medium for executing the above functions.

The present invention also relates to a program and / or data for causing a computer to execute all or a part of the functions of all or part of the above-described means of the present invention. It may be realized as an information aggregate that performs a function.

In the above description, data includes a data structure, a data format, a type of data, and the like.
The medium includes a recording medium such as a ROM, a transmission medium such as the Internet, and a transmission medium such as light, radio waves, and sound waves. Further, the carried medium is, for example, a recording medium on which a program and / or data is recorded, or a program and / or
Or, include a transmission medium for transmitting data.

Further, the fact that the program can be processed by a computer means that the program can be read by a computer in the case of a recording medium such as a ROM, and the program and / or program to be transmitted in the case of a transmission medium. Or that the data can be handled by a computer as a result of transmission,
For example, it includes software such as a program and / or data.

Therefore, as described above, the configuration of the present invention may be realized by software or hardware.

[0048]

As described above, according to the present invention, a capacitor is provided between the gate electrode of each of the P-channel and N-channel of the switching element of the C-MOS structure for sampling the external input signal in the display device and the image signal wiring. By independently operating the P-channel transistor and the N-channel transistor in response to a polarity-inverted signal input from the outside, there is no need to add a potential modulation circuit to a peripheral circuit for driving the liquid crystal display device. Power consumption of the image signal output circuit can be reduced.

[Brief description of the drawings]

FIG. 1 is an electrical equivalent circuit diagram of a display element of a TFT active matrix drive LCD according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining timing of a driving waveform according to the embodiment of the present invention.

FIG. 3 is a diagram for explaining timings of driving waveforms in a conventional opposing inversion driving method.

FIG. 4 is an equivalent circuit diagram of a conventional image display portion in which TFTs and pixel electrodes are arranged in a matrix.

[Explanation of symbols]

1 voltage waveform applied to the gate electrode of the pixel electrode TFT 2 voltage waveform applied to the image signal wiring of the pixel electrode TFT 3 voltage waveform applied to the counter electrode for holding the liquid crystal material between the pixel electrode and the TFT 4 Gate electrode of pixel electrode TFT 5 Image signal wiring 6 Counter electrode 7 Pixel electrode 8 Scanning signal wiring 9 Image signal wiring 10 TFT 11 N-channel TFT 12 P-channel TFT 13 External input signal wiring 14 N-channel TFT gate wiring 15 P-channel TFT gate Wiring 16 Pixel TFT gate-source capacitance Cgs 17 P-channel TFT gate-source capacitance Cgsp 18 N-channel TFT gate-source capacitance Cgsn 19 Liquid crystal capacitance Clc 20 Parasitic capacitance between the gate electrode and the pixel electrode of the pixel TFT is Cgd 21 Waveform applied to scanning signal wiring 8 22 N Channel TFT gate voltage waveform 23 P-channel gate voltage waveform 24 Voltage of pixel electrode 30 Counter electrode 31 Pixel electrode

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H093 NA16 NA32 NA33 NC09 NC11 NC18 NC34 ND38 ND42 5C006 AC09 BB16 BC13 BF11 BF37 FA46 FA47 5C080 AA05 AA06 AA10 BB05 DD26 EE19 EE29 FF11 JJ02 JJ03 JJ04 JJ04

Claims (10)

[Claims] 1. A semiconductor switching element having a C-MOS configuration for receiving a power supply of a predetermined input signal, sampling a potential of the input signal, and outputting the sampled potential as an image signal potential to an image signal wiring; A drive circuit comprising: a capacitor provided between each gate electrode of a P-channel transistor and an N-channel transistor of a semiconductor switching element and the image signal wiring. 2. The drive circuit according to claim 1, further comprising: a scanning signal line that crosses the image signal lines to form a plurality of grid regions; and a plurality of scanning signal lines arranged in a matrix on the plurality of grid regions. ,
A semiconductor switching element receiving power from the scanning signal wiring and the image signal wiring, and arranged in a matrix on the plurality of lattice areas;
A pixel electrode for applying a signal supplied from the image signal wiring to a display material through the semiconductor switching element; and a counter electrode that holds the display material in opposition to the pixel electrode. A display device, wherein a difference between a potential of a signal applied to an electrode and a potential of the counter electrode is larger than a difference between a potential of the predetermined input signal and a potential of the counter electrode. 3. The method of driving a display device according to claim 2, wherein the potentials of the gate electrodes of the P-channel transistor and the N-channel transistor of the semiconductor switching element having the C-MOS configuration are set at independent timings. And changing the potential of the image signal to apply a signal to the pixel electrode. 4. The driving method according to claim 3, wherein the P-channel transistor and the N-channel transistor of the semiconductor switching element having the C-MOS configuration are not simultaneously turned on. 5. The display device according to claim 4, wherein the polarity of the voltage of the image signal input to the semiconductor switching element having the C-MOS configuration is inverted for each field or each scanning line of the display screen. 3. The driving method of the driving circuit according to 1., 6. The driving method according to claim 5, wherein the absolute value of the voltage of the image signal is different for each of the polarities. 7. The potential of the image signal when the P-channel transistor of the semiconductor switching element having the C-MOS configuration is on is Vs ⁺ , and the image when the N-channel transistor of the semiconductor switching element having the C-MOS configuration is on. Signal potential is V
s ^- When, if the image signal potential Vs ⁺ is applied, the potential of the pixel electrode with respect to the counter electrode is high, the potential of the image signal Vs ^- If is applied, the relative to the counter electrode 7. The method according to claim 6, wherein a potential between the pixel electrodes is low. 8. The method according to claim 3, wherein the potential of the counter electrode is constant. 9. A program and / or a program for causing a computer to execute all or a part of the functions of all or part of the present invention according to any one of claims 2 to 8.
Alternatively, a medium that carries data and can be processed by a computer. 10. A program and / or data for causing a computer to execute all or a part of the functions of all or a part of the present invention according to any one of claims 2 to 8. Information aggregate to do.