JP2011145328A - Display device and display driving method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress changes in a driving current to a light-emitting element, caused by a leakage current in the off period of a sampling transistor. <P>SOLUTION: A sampling transistor and an auxiliary switching element are connected in series between the gate of a driving transistor and a signal line, and a leak suppressing capacitor is connected to the connection point. Upon writing a video signal voltage, the sampling transistor and the auxiliary switch element are conducted to input the video signal voltage applied to a signal line into the gate of the driving transistor. After writing, the auxiliary switch element is conducted in a state that the sampling transistor is not conducted, and the voltage of the signal line (voltage higher than a threshold correction reference voltage) is written in the leak suppressing capacitor, so that the drain-source voltage of the sampling transistor is made low to reduce a leakage current. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a display device having a pixel array in which pixel circuits are arranged in a matrix, and a display driving method thereof, for example, a display device using an organic electroluminescence element (organic EL (Electroluminescence) element) as a light emitting element. About.

JP 2003-255856 A JP 2003-271095 A JP 2008-33193 A JP 2008-281671 A JP 2001-222256 A

For example, as can be seen in Patent Documents 1 and 2, image display devices using organic EL elements as pixels have been developed. Since the organic EL element is a self-luminous element, it has advantages such as higher image visibility than a liquid crystal display, no need for a backlight, and high response speed. Further, the luminance level (gradation) of each light emitting element can be controlled by the value of the current flowing therethrough (so-called current control type).
In the organic EL display, similarly to the liquid crystal display, there are a simple matrix method and an active matrix method as driving methods. Although the former has a simple structure, there is a problem that it is difficult to realize a large-sized and high-definition display. Therefore, the active matrix method is actively developed at present. In this method, a current flowing through a light emitting element in each pixel circuit is controlled by an active element (generally a thin film transistor: TFT) provided in the pixel circuit.

In the case of the active matrix method, a thin film transistor provided inside a pixel is used as a switching transistor for sampling a video signal (hereinafter referred to as a sampling transistor) in order to apply a video signal voltage as a gradation value to a pixel circuit having an organic EL element. I use it.
When the organic EL element emits light, the video signal voltage supplied to the signal line is taken into a storage capacitor provided at the gate end (control input terminal) of the drive transistor by making the sampling transistor conductive. Then, the drive transistor supplies a drive signal corresponding to the captured video signal voltage to the organic EL element. For example, in an organic EL display device, an input video signal voltage is converted into a current signal by a driving transistor, and the driving current is supplied to an organic EL element.
At this time, in order that the light emission luminance of the organic EL element is unchanged, it is important that the video signal voltage taken in and held in the holding capacitor is constant. For example, in order for the light emission luminance of the organic EL element to be unchanged, it is important that the drive current corresponding to the input video signal voltage is constant.
For this reason, various mechanisms for making the drive current constant have been studied as pixel circuits for organic EL elements (see, for example, Patent Document 3 above).

Here, in a pixel circuit using an organic EL element, after a video signal voltage is written in a storage capacitor, a bootstrap operation is performed to emit light. For this reason, the gate voltage of the drive transistor is higher than the input video signal voltage.
As described above, the video signal voltage is taken into the gate terminal of the driving transistor through the sampling transistor and held in the holding capacitor.
However, when the leakage current of the sampling transistor (and the various transistors performing the switching operation) provided on the gate terminal side of the driving transistor is large, the leakage current flows from the gate terminal of the driving transistor toward the signal line. As a result, the voltage held in the storage capacitor varies depending on the leakage current.
As a result, the drive current for the organic EL element varies, and the light emission luminance cannot be maintained constant.

  Further, as a characteristic of the thin film transistor that performs the switching operation, the higher the drain-source voltage, the larger the leakage current in the off region. For this reason, the leakage current of the sampling transistor easily flows during the period when the voltage of the signal line is low. If the level of this phenomenon is different for each pixel, even if all the pixels emit light at the same gradation, the display image becomes a rough image as shown in FIG.

  This countermeasure is disclosed in the above-mentioned Patent Documents 4 and 5, but the process steps become complicated by changing the LDD (Lightly Doped Drain) structure, and the pixel circuit itself becomes complicated, resulting in cost and yield points. The problem remains that it is disadvantageous.

  Therefore, the present invention suppresses a leakage current at the time of light emission of a transistor used for a switching operation in the pixel circuit, so that the light emission luminance can be kept constant.

The display device of the present invention includes a light-emitting element, a drive transistor that applies a current according to a gate-source voltage to the light-emitting element when a drive voltage is applied between the drain and the source, and the drive transistor A sampling transistor and an auxiliary switch element that are connected in series between the gate and the signal line and are turned on to input the signal line voltage to the gate of the driving transistor, and are connected between the gate and source of the driving transistor. A pixel circuit having a storage capacitor for holding a threshold voltage of the driving transistor and the input video signal voltage, and a leakage suppression capacitor connected to a connection point of the sampling transistor and the auxiliary switch element; A signal selector for supplying a video signal voltage and a reference voltage as the signal line voltage to each signal line arranged in a column on a pixel array in which the pixel circuits are arranged in a matrix; and the pixel A drive control scanner that applies a power pulse to each power control line arranged in a row on the array and applies a drive voltage to the drive transistor of the pixel circuit, and a row arranged on the pixel array A first scan pulse is applied to the first write control line corresponding to the sampling transistor, and a second scan pulse is applied to the second write control line corresponding to the auxiliary switch. And a writing scanner that controls the sampling transistor and the auxiliary switch of the circuit to input a video signal voltage and a reference voltage to each pixel circuit.
When the signal selector applies the video signal voltage to the signal line, the writing scanner makes the sampling transistor and the auxiliary switch element conductive by the first and second scanning pulses, and the video signal A voltage is input to the gate of the drive transistor, and after the video signal voltage is written, the auxiliary switch element is turned on in the non-conductive state of the sampling transistor by the first and second scan pulses, and The voltage of the signal line is written into the leakage suppression capacitor.

In this case, the signal selector outputs a threshold correction reference voltage and a leak suppression reference voltage (that is, three values of a video signal voltage, a threshold correction reference voltage, and a leak suppression reference voltage) as the reference voltage. After the video signal voltage is written, the writing scanner makes the sampling transistor non-conductive by the first and second scanning pulses when the signal selector gives the leak suppression reference voltage. In this state, the auxiliary switch element is turned on to write the leak suppression reference voltage to the leak suppression capacitor.
The leak suppression reference voltage is higher than the threshold correction reference voltage.

  Alternatively, when the signal selector outputs at least two values of the video signal voltage and the threshold correction reference voltage, the writing scanner is after the video signal voltage is written and the signal selector is the video signal. Within the period in which the signal voltage is applied, the auxiliary switch element is turned on by the first and second scanning pulses while the sampling transistor is turned off, and the video signal voltage is written into the leakage suppression capacitor. Make it.

  The display driving method of the present invention is the display driving method of the display device having the above-described configuration, in which the writing scanner is configured to display the first and second signals when the signal selector applies a video signal voltage to the signal line. The sampling transistor and the auxiliary switch element are turned on by the scan pulse, and the video signal voltage is input to the gate of the drive transistor. After the video signal voltage is written, the video signal voltage is written by the first and second scan pulses. In this display driving method, the auxiliary switch element is turned on while the sampling transistor is in a non-conductive state, and the voltage of the signal line is written to the leakage suppression capacitor.

In the present invention, after writing the video signal voltage to the gate of the drive transistor, a voltage higher than the threshold correction reference voltage is written to the leakage suppression capacitor. The voltage higher than the threshold correction reference voltage corresponds to, for example, a leak suppression reference voltage or a video signal voltage written immediately before.
This lowers the drain-source voltage of the sampling transistor during the light emission period.
This alleviates the operating point of the leakage current of the sampling transistor and can suppress the leakage current. By suppressing the leak current, fluctuations in the drive current due to the leak current are suppressed.

According to the present invention, during the light emission period in which the sampling transistor is off, the drain-source voltage of the sampling transistor is lowered, and the operating point of the leakage current of the sampling transistor is alleviated.
As a result, the leakage current of the sampling transistor can be suppressed, and fluctuations in the drive current due to the leakage current can be suppressed. As a result, it is possible to provide a display device with uniform image quality that does not deteriorate due to leakage current such as roughness of the display screen.

It is explanatory drawing of a structure of the display apparatus of embodiment of this invention. It is a circuit diagram of a pixel circuit of an embodiment. It is a circuit diagram of a pixel circuit considered in the process leading to the present invention. It is explanatory drawing of normal pixel circuit operation | movement. It is explanatory drawing of the leakage current in the light emission period. It is explanatory drawing of the influence of the leakage current in the light emission period. It is explanatory drawing of operation | movement of the pixel circuit of 1st Embodiment. It is an equivalent circuit diagram of the pixel circuit of the embodiment. It is explanatory drawing of the operating point of the sampling transistor of embodiment. It is explanatory drawing of operation | movement of the pixel circuit of 2nd Embodiment. It is explanatory drawing of the display state with roughness.

Hereinafter, embodiments of the present invention will be described in the following order.
[1. Configuration of Display Device and Pixel Circuit]
[2. Pixel circuit operation considered in the process leading to the present invention]
[3. Pixel Circuit Operation of First Embodiment]
[4. Pixel Circuit Operation of Second Embodiment]

[1. Configuration of Display Device and Pixel Circuit]

FIG. 1 shows a configuration of an organic EL display device according to an embodiment.
This organic EL display device includes a pixel circuit 10 that uses an organic EL element as a light emitting element and performs light emission driving by an active matrix method.
As illustrated, the organic EL display device includes a pixel array 20 in which a large number of pixel circuits 10 are arranged in a matrix in the column direction and the row direction (m rows × n columns). Each of the pixel circuits 10 is a light emitting pixel of any one of R (red), G (green), and B (blue), and a color display device is configured by arranging the pixel circuits 10 of each color according to a predetermined rule. .

As a configuration for driving each pixel circuit 10 to emit light, a horizontal selector 11, a drive scanner 12, and a write scanner 13 are provided.
Also, signal lines DTL1, DTL2,... DTL (n), which are selected by the horizontal selector 11 and supply a voltage corresponding to the signal value (gradation value) of the luminance signal as display data to the pixel circuit 10, are on the pixel array. It is arranged in the column direction. The signal lines DTL1, DTL2,... DTL (n) are arranged by the number of columns (n columns) of the pixel circuits 10 arranged in a matrix in the pixel array 20.

  On the pixel array 20, the first write control lines WSLa1, WSLa2,. , DSL2... DSL (m). These first and second write control lines WSLa and WSSLb and the power supply control line DSL are arranged by the number of rows (m rows) of the pixel circuits 10 arranged in a matrix in the pixel array 20, respectively.

The first write control line WSLa (WSLa1 to WSLa (m)) is driven by the write scanner 13.
The write scanner 13 sequentially applies the first scanning pulses WSa (WSa1, WSa2... WSa (m) to the write control lines WSLa1 to WSLa (m) arranged in rows at predetermined timings set. ) To scan the pixel circuit 10 line-sequentially in units of rows.
The second write control line WSLb (WSLb1 to WSLb (m)) is also driven by the write scanner 13.
As will be described later, the write scanner 13 basically applies the second scanning pulse WSb (WSb1, WSb2,... WSb (m)) that is at the same timing as the first scanning pulse WSa but only partially differs. Are sequentially supplied to the write control lines WSLb1 to WSLb (m) arranged in rows.

The power supply control lines DSL (DSL1 to DSL (m)) are driven by the drive scanner 12. The drive scanner 12 supplies power pulses DS (DS1, DS2,... DS (m)) to the power supply control lines DSL1 to DSL (m) arranged in a row in accordance with the line sequential scanning by the write scanner 13. To do.
The power supply pulse DS (DS1, DS2,... DS (m)) is a pulse voltage that switches between two values of the drive voltage Vcc and the initial voltage Vini.
The drive scanner 12 and the write scanner 13 set the timing of the scanning pulses WSa and WSb and the power supply pulse DS based on the clock ck and the start pulse sp.

The horizontal selector 11 supplies a signal line voltage as an input signal to the pixel circuit 10 to the signal lines DTL1, DTL2,... Arranged in the column direction in accordance with the line sequential scanning by the write scanner 13.
The horizontal selector 11 supplies a video signal voltage and a reference voltage as signal line voltages to each signal line.
In the case of the first embodiment described in FIG. 7, the horizontal selector 11 outputs a threshold correction reference voltage Vofs and a leak suppression reference voltage Vofs2 as reference voltages. That is, the horizontal selector 11 performs ternary driving of the video signal voltage Vsig, the threshold correction reference voltage Vofs, and the leak suppression reference voltage Vofs2 as signal line voltages for each signal line.
On the other hand, in the case of the second embodiment described in FIG. 10, only the threshold correction reference voltage Vofs is used as the reference voltage. Therefore, the horizontal selector 11 performs binary driving of the video signal voltage Vsig and the threshold correction reference voltage Vofs as the signal line voltage for each signal line.

  In the display device of this embodiment, an example of a signal selector referred to in the present invention is the horizontal selector 11, an example of a drive control scanner is a drive scanner, and an example of a writing scanner is a write scanner 13. Become.

FIG. 2 shows a configuration example of the pixel circuit 10. The pixel circuits 10 are arranged in a matrix like the pixel circuits 10 in the configuration of FIG.
In FIG. 2, only one pixel circuit 10 arranged at a portion where the signal line DTL intersects with the write control lines WSLa and WSLB and the power supply control line DSL is shown for the sake of simplicity.

  The pixel circuit 10 includes an organic EL element 1 that is a light emitting element, a storage capacitor Cs, a sampling transistor Ts, and an n-channel thin film transistor (TFT) as a driving transistor Td. In addition, it has an auxiliary switch Ts2 composed of an n-channel TFT and a leakage suppression capacitor C2. Note that the capacitance Coled is a parasitic capacitance of the organic EL element 1.

The storage capacitor Cs has one terminal connected to the source (node ND2) of the drive transistor Td and the other terminal connected to the gate (node ND1) of the drive transistor Td.
The drain of the drive transistor Td is connected to the power supply control line DSL.
The light emitting element of the pixel circuit 10 is, for example, the organic EL element 1 having a diode structure, and includes an anode and a cathode. The anode of the organic EL element 1 is connected to the source of the drive transistor Td, and the cathode is connected to a predetermined wiring (cathode potential Vcat).

The sampling transistor Ts and the auxiliary switch Ts2 are connected in series between the gate of the drive transistor Td and the signal line DTL.
One end of the source and drain of the sampling transistor Ts is connected to the gate of the drive transistor Td, and the other end is connected to the auxiliary switch Ts2. The gate of the sampling transistor Ts is connected to the first write control line WSLa, and therefore the sampling transistor Ts is on / off controlled by the first scanning pulse WSa.
One end of the source and drain of the auxiliary switch Ts2 is connected to the signal line DTL, and the other end is connected to the sampling transistor Ts. The gate of the auxiliary switch Ts2 is connected to the second write control line WSLb. Therefore, the auxiliary switch Ts2 is ON / OFF controlled by the second scanning pulse WSb.

  A connection point between the sampling transistor Ts and the auxiliary switch Ts2 is a node ND3. The leakage suppression capacitor C2 is connected between the node ND3 and a predetermined potential (for example, ground potential or cathode potential Vcat).

The light emission driving of the organic EL element 1 is basically as follows.
At the timing when the video signal voltage Vsig is applied to the signal line DTL, the sampling transistor Ts and the auxiliary switch Ts2 are turned on by the scan pulses WSa and WSb supplied from the write scanner 13 by the write control lines WSLa and WSLb. As a result, the video signal voltage Vsig from the signal line DTL is input to the gate of the drive transistor Td and written to the storage capacitor Cs.

The drive transistor Td causes the drive current Ids to flow through the organic EL element 1 by supplying current from the power supply control line DSL to which the drive voltage Vcc is applied by the drive scanner 12, and causes the organic EL element 1 to emit light.
At this time, the drive current Ids becomes a value corresponding to the gate-source voltage Vgs of the drive transistor Td (value corresponding to the voltage held in the holding capacitor Cs), and the organic EL element 1 has a luminance corresponding to the current value. Emits light.
That is, in the case of this pixel circuit 10, by writing the video signal voltage Vsig from the signal line DTL to the storage capacitor Cs, the gate applied voltage of the drive transistor Td is changed, thereby controlling the value of the current flowing through the organic EL element 1. To obtain the gradation of light emission.

Since the drive transistor Td is designed to always operate in the saturation region, the drive transistor Td becomes a constant current source having a value represented by the following expression 1.
Ids = (1/2) · μ · (W / L) · Cox · (Vgs−Vth) ² (Equation 1)
Where Ids is the current flowing between the drain and source of a transistor operating in the saturation region, μ is the mobility, W is the channel width, L is the channel length, Cox is the gate capacitance, and Vth is the threshold voltage of the driving transistor Td. Yes.
As is clear from Equation 1, the current Ids is controlled by the gate-source voltage Vgs in the saturation region. Since the gate-source voltage Vgs is kept constant, the drive transistor Td operates as a constant current source, and can emit the organic EL element 1 with constant luminance.

In this way, basically, in each frame period, an operation is performed in which the video signal value (gradation value) Vsig is written in the storage capacitor Cs in the pixel circuit 10, and thereby the driving transistor is selected according to the gradation to be displayed. The gate-source voltage Vgs of Td is determined.
The drive transistor Td functions as a constant current source for the organic EL element 1 by operating in the saturation region, and a current corresponding to the gate-source voltage Vgs is supplied to the organic EL element 1 so that each frame period is The organic EL element 1 emits light with a luminance corresponding to the gradation value of the video signal.

[2. Pixel circuit operation considered in the process leading to the present invention]

Here, in order to understand the operation of the present embodiment to be described later, the pixel circuit operation considered in the process leading to the present invention will be described first. This is a circuit operation including a threshold correction operation and a mobility correction operation for compensating for uniformity deterioration due to variations in the threshold and mobility of the driving transistor Td of each pixel circuit 10. The threshold correction operation is an example in which divided threshold correction is performed a plurality of times by dividing within one light emission cycle.

In the pixel circuit operation, the threshold value correction operation and the mobility correction operation itself have been performed conventionally. This necessity will be briefly described.
For example, in a pixel circuit using a polysilicon TFT or the like, the threshold voltage Vth of the drive transistor Td and the mobility μ of the semiconductor thin film constituting the channel of the drive transistor Td may change over time. Further, the transistor characteristics of the threshold voltage Vth and the mobility μ are different for each pixel due to variations in the manufacturing process.
If the threshold voltage and mobility of the drive transistor Td differ from pixel to pixel, the current value flowing through the drive transistor Td varies from pixel to pixel. For this reason, even if the same video signal value (video signal voltage Vsig) is given to all the pixel circuits 10, the light emission luminance of the organic EL element 1 varies from pixel to pixel. As a result, the screen uniformity (uniformity) ) Is damaged.
For this reason, the pixel circuit operation is provided with a correction function for fluctuations in the threshold voltage Vth and the mobility μ.

Here, the operation of the general pixel circuit 10 shown in FIG. 3 will be described.
Compared with the pixel circuit 10 of the present embodiment shown in FIG. 2, the auxiliary switch Ts2 and the leakage suppression capacitor C2 are not provided.
Since the auxiliary switch Ts2 is not provided, the second write control line WSLb for the control is not provided.
The horizontal selector 11 supplies the video signal voltage Vsig and the threshold correction reference voltage Vofs for threshold correction operation to the signal line DTL in a time division manner.

The basic light emission operation by applying a current from the drive transistor Td to the organic EL element 1 is the same.
That is, at the timing when the video signal voltage Vsig is applied to the signal line DTL, the sampling transistor Ts is turned on by the scanning pulse WS applied from the write scanner 13 by the write control line WSL. As a result, the video signal voltage Vsig from the signal line DTL is written to the storage capacitor Cs.
The drive transistor Td functions as a constant current source for the organic EL element 1 by operating in the saturation region, and a current Ids corresponding to the video signal voltage Vsig (gate-source voltage Vgs) written in the storage capacitor Cs. Is passed through the organic EL element 1. As a result, light emission with luminance corresponding to the gradation value of the video signal is performed.

FIG. 4 shows a timing chart of the operation of one light emission cycle (one frame period) of the pixel circuit 10.
FIG. 4 shows the signal line voltage that the horizontal selector 11 applies to the signal line DTL. In the case of this operation example, the horizontal selector 11 supplies the signal line DTL with the pulse voltage as the threshold correction reference voltage Vofs and the video signal voltage Vsig in one horizontal period (1H) as the signal line voltage.
FIG. 4 shows a power pulse DS supplied from the drive scanner 12 via the power control line DSL. The drive voltage Vcc or the initial voltage Vini is given as the power supply pulse DS.
FIG. 4 shows a scan pulse WS applied to the gate of the sampling transistor Ts by the write scanner 13 via the write control line WSL. The n-channel sampling transistor Ts is turned on when the scanning pulse WS is set to the H level, and is turned off when the scanning pulse WS is set to the L level.
FIG. 4 shows changes in the gate voltage Vg and the source voltage Vs of the drive transistor Td as the voltages of the nodes ND1 and ND2 shown in FIG.

Time ts in the timing chart of FIG. 4 is a start timing of one cycle in which the organic EL element 1 as a light emitting element is driven to emit light, for example, one frame period of image display.
Before reaching this time point ts (period LT1), light emission of the previous frame is performed.
That is, the light emission state of the organic EL element 1 is a state where the power supply pulse DS is the drive voltage Vcc and the sampling transistor Ts is turned off. At this time, since the drive transistor Td is set to operate in the saturation region, the drive current Ids flowing through the organic EL element 1 is expressed by the above-described equation 1 according to the gate-source voltage Vgs of the drive transistor Td. Value.

The operation for light emission of the current frame is started at time ts.
First, the power supply pulse DS is set to the initial potential Vini.
At this time, when the initial potential Vini is smaller than the sum of the threshold voltage Vthel and the cathode voltage Vcat of the organic EL element 1, that is, Vini ≦ Vthel + Vcat, the organic EL element 1 is extinguished and a non-light emitting period is started. At this time, the power supply control line DSL becomes the source of the drive transistor Td. The anode (node ND2) of the organic EL element 1 is charged to the initial potential Vini.

Then, preparation for threshold correction is performed (period LT2).
That is, in the period LT2, when the potential of the signal line DTL becomes the threshold correction reference voltage Vofs, the scanning pulse WS is set to the H level, and the sampling transistor Ts is turned on. Therefore, the gate (node ND1) of the drive transistor Td becomes the threshold correction reference voltage Vofs. As a result, the gate-source voltage Vgs of the drive transistor Td becomes Vgs = Vofs−Vini.
Since the threshold value correction operation cannot be performed unless this Vofs−Vini is larger than the threshold voltage Vth of the drive transistor Td, the initial potential Vini and the reference voltage Vofs are set so that Vofs−Vini> Vth. .
That is, as a preparation for threshold correction, the gate-source voltage of the drive transistor is sufficiently widened than the threshold voltage Vth.

Subsequently, threshold correction (Vth correction) is performed (period LT3). Here, an example is shown in which threshold correction is performed four times during the periods LT3a to LT3d.
First, during the period LT3a, the first threshold correction (Vth correction) is performed.
In this case, at the timing when the signal line voltage becomes the threshold correction reference voltage Vofs, the write scanner 13 sets the scanning pulse WS to the H level, and the drive scanner 12 sets the power supply pulse DS to the driving voltage Vcc.
In this case, the anode (node ND2) of the organic EL element 1 serves as the source of the drive transistor Td, and a current flows. Therefore, the source node rises while the gate (node ND1) of the drive transistor Td is fixed to the threshold correction reference voltage Vofs.
As long as the anode potential of the organic EL element 1 (potential of the node ND2) is equal to or lower than Vcat + Vthel (threshold voltage of the organic EL element 1), the current of the drive transistor Td is used to charge the storage capacitor Cs and the capacitor Coled. “As long as the anode potential of the organic EL element 1 is equal to or lower than Vcat + Vthel” means that the leakage current of the organic EL element 1 is considerably smaller than the current flowing through the drive transistor Td.
For this reason, the potential of the node ND2 (the source potential of the driving transistor Td) increases with time.

This threshold correction is basically an operation of setting the gate-source voltage of the drive transistor Td to the threshold voltage Vth. Therefore, the source potential of the drive transistor Td only needs to be raised until the gate-source voltage of the drive transistor Td reaches the threshold voltage Vth.
However, the gate node can be fixed to the threshold correction reference voltage Vofs only during the period of the signal line voltage = Vofs. Then, depending on the frame rate or the like, sufficient time for the source potential to rise cannot be taken by the threshold correction operation once until the gate-source voltage reaches the threshold voltage Vth. Therefore, the threshold value correction is performed in a plurality of times.

For this reason, the threshold correction as the period LT3a is ended before the signal line voltage = the video signal voltage Vsig. That is, the write scanner 13 once sets the scanning pulse WS to L level and turns off the sampling transistor Ts.
At this time, since both the gate and the source are floating, a current flows between the drain and the source in accordance with the gate-source voltage Vgs and bootstraps. That is, the gate potential and the source potential rise as shown.

Next, in the period LT3b, the second threshold correction is performed. That is, when signal line voltage = threshold correction reference voltage Vofs, the write scanner 13 sets the scanning pulse WS to H level again and turns on the sampling transistor Ts. As a result, the gate voltage of the drive transistor Td = the threshold correction reference voltage Vofs, and the source potential is increased.
Further, the threshold correction operation is paused. Since the gate-source voltage of the drive transistor Td is closer to the threshold voltage Vth in the second threshold correction, the bootstrap amount in the second pause period is smaller than that in the first pause period.
Further, the third threshold correction is performed in the period LT3c, and after a pause, the fourth threshold correction is performed in the period LT3d.
Finally, the gate-source voltage of the drive transistor Td becomes the threshold voltage Vth.
At this time, the source potential (node ND2: anode potential of the organic EL element 1) = Vofs−Vth ≦ Vcat + Vthel. (Vcat is the cathode potential, Vthel is the threshold voltage of the organic EL element 1)
In the case of FIG. 4, after the fourth threshold correction period LT3d, the scanning pulse WS is set to L level, the sampling transistor Ts is turned off, and the threshold correction operation is completed.

  Thereafter, during a period LT4 in which the signal line voltage is the video signal voltage Vsig, the write scanner 13 sets the scanning pulse WS to the H level, and writing of the video signal voltage Vsig and mobility correction are performed. That is, the video signal voltage Vsig is input to the gate of the drive transistor Td.

The gate potential of the drive transistor Td becomes the potential of the video signal voltage Vsig, but current flows because the power supply control line DSL is at the drive voltage Vcc, and the source potential rises with time.
At this time, if the source voltage of the driving transistor Td does not exceed the sum of the threshold voltage Vthel and the cathode voltage Vcat of the organic EL element 1, the current of the driving transistor Td is used to charge the holding capacitor Cs and the capacitor Coled. That is, the condition is that the leakage current of the organic EL element 1 should be much smaller than the current flowing through the drive transistor Td.
At this time, since the threshold value correcting operation of the drive transistor Td is completed, the current flowing through the drive transistor Td reflects the mobility μ.
Specifically, those with high mobility have a large current amount at this time, and the source rises quickly. On the other hand, when the mobility is low, the amount of current is small and the source rises slowly.
As a result, during the period LT4 when the scanning pulse WS is at the H level, the source voltage Vs of the drive transistor Td rises after the sampling transistor Ts is turned on, and when the sampling transistor Ts is turned off, the source voltage Vs becomes the mobility μ The voltage Vs0 reflects the above. The gate-source voltage Vgs of the drive transistor Td is reduced to reflect the mobility (Vgs = Vsig−Vs0), and becomes a voltage that completely corrects the mobility after a predetermined time has elapsed.

After writing the video signal voltage Vsig and correcting the mobility in this way, the gate-source voltage Vgs is determined, and the process proceeds to the bootstrap and light emission state (period LT5).
That is, the scanning pulse WS is set to L level, the sampling transistor Ts is turned off, writing is completed, and the organic EL element 1 is caused to emit light. In this case, the drive current Ids according to the gate-source voltage Vgs of the drive transistor Td flows, the potential of the node ND2 rises to the voltage VEL through which the current flows in the organic EL element 1, and the organic EL element 1 emits light. . At this time, the sampling transistor Ts is off, and the gate of the drive transistor Td (node ND1) rises at the same time as the potential of the node ND2 rises, so the gate-source voltage Vgs remains constant. (Bootstrap operation)

As described above, the pixel circuit 10 performs the operation for light emission of the organic EL element 1 including the threshold value correction operation and the mobility correction operation as the light emission drive operation of one cycle in one frame period.
By the threshold correction operation, a current corresponding to the signal potential Vsig can be supplied to the organic EL element 1 regardless of variations in the threshold voltage Vth of the driving transistor Td in each pixel circuit 10 and variations in the threshold voltage Vth due to temporal variation. it can. That is, variations in the threshold voltage Vth due to manufacturing or changes over time can be canceled, and high image quality can be maintained without causing uneven brightness on the screen.
In addition, since the drain current varies depending on the mobility of the driving transistor Td, the image quality deteriorates due to variations in the mobility of the driving transistor Td for each pixel circuit 10, but the mobility correction increases or decreases the mobility of the driving transistor Td. In response to this, the source potential Vs is obtained.
As a result, the gate-source voltage Vgs is adjusted so as to absorb the variation in mobility of the drive transistor Td of each pixel circuit 10, so that the deterioration in image quality due to the variation in mobility is also eliminated.

Further, the threshold correction operation is divided and performed a plurality of times as one cycle of pixel circuit operation because of the demand for higher speed (higher frequency) of the display device.
As the frame rate is increased, the operation time of the pixel circuit is relatively shortened, so that it is difficult to secure a continuous threshold correction period (signal line voltage = threshold correction reference voltage Vofs period). . Thus, by performing the threshold correction operation in a time-sharing manner as described above, a necessary period is secured as the threshold correction period, and the gate-source voltage of the drive transistor Td is converged to the threshold voltage Vth.

For example, as shown in FIG. 3, one cycle of light emission driving operation is performed, but the following points are problematic.
As described above, as the pixel circuit operation, after the video signal voltage Vsig is written in the storage capacitor Cs, the bootstrap operation is performed to emit light.
Therefore, at the start of the light emission period LT5, the gate voltage of the drive transistor Td becomes equal to or higher than the video signal voltage Vsig, as can be seen from FIG.
Here, in the light emission period LT5, the sampling transistor Ts is turned off. However, as shown in FIG. 5A, there is a leakage current Ileak when the sampling transistor Ts is off.
The leakage current Ileak flows from the gate terminal of the driving transistor Td toward the signal line DTL, so that the voltage held in the holding capacitor Cs varies.
For this reason, the gate-source voltage of the drive transistor Td fluctuates, the drive current Ids fluctuates, and the light emission luminance cannot be kept constant.
Although FIG. 4 shows an ideal state, actually, as shown in FIG. 6, the gate voltage Vg of the driving transistor Td varies due to the influence of the leakage current Ileak in the light emission period LT5.

FIG. 5B shows the characteristics of the gate voltage / drain current of the sampling transistor Ts.
FIG. 5B shows a case where the drain-source voltage (Vds) is different between the straight line and the broken line, but the higher the drain-source voltage (Vds), the higher the drain current Id in the off region (that is, (Leakage current) increases.
As described above, in the light emission period LT5, the gate voltage Vg of the drive transistor Td becomes higher than the video signal voltage Vsig due to bootstrap after writing the video signal voltage Vsig. Therefore, as shown in FIG. 5A, the sampling transistor Ts has a drain (D) on the node ND1 side and a source (S) on the signal line DTL side.
Also in the light emission period LT5, the threshold value correction reference voltage Vofs and the video signal voltage Vsig are supplied to the signal line DTL every 1H period for the pixel circuits of other lines.

Then, the drain-source voltage (Vds) of the sampling transistor Ts becomes higher when the signal line DTL is at the threshold correction reference voltage Vofs than when the signal line DTL is at the video signal voltage Vsig. Of course, the video signal voltage Vsig cannot be generally described because it varies depending on the gradation value to be displayed. However, as a representative example, the broken line in FIG. 5B represents the solid line when the signal line DTL = the video signal voltage Vsig. It can be considered that signal line DTL = threshold correction reference voltage Vofs.
When the signal line DTL = the threshold correction reference voltage Vofs, the drain-source voltage Vds of the sampling transistor Ts becomes the largest, and at this time, the leakage current Ileak becomes the largest.
In FIG. 6, in the light emission period LT5, the amount of leakage is larger when the voltage of the signal line DTL is the threshold value correction reference voltage Vofs than when the voltage of the signal line DTL is the video signal voltage Vsig, and the change in the gate voltage of the drive transistor Td is larger. ing.

  As described above, the gate current of the driving transistor Td changes due to the leakage current Ileak of the sampling transistor Ts, and the gate-source voltage Vgs of the driving transistor Td varies. Therefore, the drive current Ids to the organic EL element 1 fluctuates, and it becomes difficult to maintain a constant luminance according to the video signal voltage Vsig during the light emission period LT5.

The amount of leakage current depends on the characteristics of each sampling transistor Ts. If the characteristics of the sampling transistor Ts are different for each pixel circuit 10, even if all the pixels emit light by the video signal voltage Vsig of the same gradation, the amount of leak current differs in each pixel circuit 10, The light emission luminance in the pixel circuit 10 does not become constant.
As a result, the display image becomes a rough image as shown in FIG.

[3. Pixel Circuit Operation of First Embodiment]

In the present embodiment, in order to prevent light emission luminance fluctuation due to such a leakage current, the configuration described with reference to FIGS. 1 and 2 is adopted, and the pixel circuit 10 as shown in FIG. 7 is driven.
This is a driving method in which after writing the video signal voltage Vsig, a voltage higher than the threshold correction reference voltage Vofs (leakage suppression reference voltage Vofs2) is written from the signal line DTL to the leakage suppression capacitor C2 via the auxiliary switch Ts2. .

FIG. 7 shows a timing chart of the operation of one light emission cycle (one frame period) of the pixel circuit 10 as in FIG.
First, the signal line voltage applied to the signal line DTL by the horizontal selector 11 is shown. In the case of FIG. 7, the horizontal selector 11 is ternary driven, unlike the example of FIG. That is, the horizontal selector 11 supplies the signal line DTL with the pulse voltage as the threshold correction reference voltage Vofs, the video signal voltage Vsig, and the leak suppression reference voltage Vofs2 as the signal line voltage in one horizontal period (1H).

FIG. 7 also shows a scanning pulse WSa applied to the gate of the sampling transistor Ts by the write scanner 13 via the first write control line WSLa. The n-channel sampling transistor Ts is turned on when the scanning pulse WSa is set to the H level, and is turned off when the scanning pulse WSa is set to the L level.
Further, a scanning pulse WSb given to the gate of the auxiliary switch Ts2 by the write scanner 13 via the second write control line WSLb is shown. The auxiliary switch Ts2 constituted by the n-channel TFT is turned on when the scanning pulse WSb is set at the H level, and is turned off when the scanning pulse WSb is set at the L level.

FIG. 7 shows a power pulse DS supplied from the drive scanner 12 via the power control line DSL. The drive voltage Vcc or the initial voltage Vini is given as the power supply pulse DS.
FIG. 7 shows changes in the gate voltage Vg and the source voltage Vs of the drive transistor Td as the voltages of the nodes ND1 and ND2 shown in FIG.

  The operation of FIG. 7 will be described. However, the periods LT1 to LT4 in FIG. 7 are the same as the basic operations in the periods LT1 to LT4 in FIG. For this reason, a detailed description is avoided, but the differences are described.

First, in the case of the present embodiment, the auxiliary switch Ts2 and the sampling transistor Ts are connected in series between the signal line DTL and the gate (node ND1) of the driving transistor Td. Therefore, in order to input the signal line potential to the gate of the drive transistor Td, both the auxiliary switch Ts2 and the sampling transistor Ts must be turned on.
In the period LT2 and the periods LT3a to LT3d, the threshold correction reference voltage Vofs is input to the node ND1 from the signal line DTL. Therefore, in these periods, the scanning pulses WSa and WSb are synchronously set to the H level.
In the period LT4, the video signal voltage Vsig is input to the node ND1 from the signal line DTL. Therefore, also in this period, the scanning pulses WSa and WSb are synchronously set to the H level.
In other words, during the periods LT2 to LT4, the auxiliary switch Ts2 and the sampling transistor Ts are turned on / off completely in synchronization, and the operations of the auxiliary switch Ts2 and the sampling transistor Ts are described in FIG. The operation is exactly the same as that of one sampling transistor Ts.

The horizontal selector 11 outputs the threshold correction reference voltage Vofs, the video signal voltage Vsig, and the leak suppression reference voltage Vofs2 to the signal line DTL in this order during the 1H period.
For such a ternary pulse, in the period LT2 and the periods LT3a to LT3d, the scanning pulses WSa and WSb are set to the H level when the voltage of the signal line DTL is set to the threshold correction reference voltage Vofs. .
In the period LT4, the scanning pulses WSa and WSb are set to the H level when the voltage of the signal line DTL is set to the video signal voltage Vsig.

Changes in the gate voltage Vg and the source voltage Vs of the drive transistor Td during the periods LT2 to LT4 are the same as those described with reference to FIG.
Then, as described with reference to FIG. 4, threshold correction preparation is performed in the period LT2, and the threshold correction operation is performed, for example, divided into four periods LT3 (LT3a to LT3d). Thereafter, in the period LT4, the writing of the video signal voltage Vsig and the mobility correction are performed.

In this embodiment, after performing the video signal voltage Vsig writing and the mobility correction in the period LT4 in this way, the scan pulses WSa and WSb are set to the L level, the gate-source voltage Vgs is determined, and the bootstrap and light emission are performed. Transition to a state (period LT5).
In this case, the drive current Ids according to the gate-source voltage Vgs of the drive transistor Td flows, the potential of the node ND2 rises to the voltage VEL through which the current flows in the organic EL element 1, and the organic EL element 1 emits light. . At this time, the sampling transistor Ts is off, and the gate of the drive transistor Td (node ND1) rises at the same time as the potential of the node ND2 rises, so the gate-source voltage Vgs remains constant. (Bootstrap operation)

As shown in the figure, the write scanner 13 is a period in which the bootstrap occurs after the video signal voltage Vsig is written, and the period in which the horizontal selector 11 applies the leakage suppression reference voltage Vofs2 to the signal line DTL. , The second scanning pulse WSb is set to the H level.
An equivalent circuit at this time is shown in FIG. When the first scanning pulse WSa is set to the L level and the second scanning pulse WSb is set to the H level, the sampling transistor Ts is turned off and the auxiliary switch Ts2 is turned on.
Since the leak suppression reference voltage Vofs2 is applied to the signal line DTL, the leak suppression reference voltage Vofs2 is input to the node ND3 and written to the leak suppression capacitor C2.

Thereafter, before the voltage of the signal line DTL becomes the threshold correction reference voltage Vofs, the write scanner 13 returns the second scanning pulse WSb to the L level. That is, the state shown in FIG. 8B is set, and thereafter the light emission state in the period LT5 is continued in this state.
In the state of FIG. 8B, the node ND1 becomes a potential after the video signal voltage Vsig is written and bootstrap. Further, the node ND3 becomes a potential based on the leak suppression reference voltage Vofs2 held in the leak suppression capacitor C2.

As described above, the leakage current of the sampling transistor Ts increases when the drain-source voltage is high.
The drain-source voltage Vds of the sampling transistor Ts becomes high during the light emission operation in the period LT5 when the threshold correction reference voltage Vofs is applied to the signal line DTL.
In practice, the leakage when the threshold correction reference voltage Vofs is applied to the signal line DTL causes large fluctuations in the gate voltage Vg and the source voltage Vs of the drive transistor Td as shown in FIG. 6, and this makes the emission luminance constant. It was a dominant factor that could not be maintained.

Therefore, in the present embodiment, in the light emission period LT5, the node ND3 is set to the leak suppression reference voltage Vofs2 that is higher than the threshold correction reference voltage Vofs.
The node ND3 is fixed to the leakage suppression reference voltage Vofs2 until the period LT5 ends and the light emission cycle of the next frame is started by the leakage suppression capacitor C2.
Then, the potential difference between the drain and source of the sampling transistor Ts in the period LT5 is the difference between the potential of the node ND1 due to the video signal voltage Vsig + bootstrap and the potential of the leak suppression reference voltage Vofs2 at the node ND3.
This potential difference is smaller than the potential difference between the potential of the node ND1 and the threshold correction reference voltage Vofs.

  Thereby, the voltage difference applied between the drain and source of the sampling transistor Ts can be reduced, and the operating point where the leak current flows can be relaxed as shown in FIG. That is, in FIG. 9, the voltage VWSL is assumed to be the L level potential of the first scanning pulse WSa, and the operating point of the sampling transistor Ts when it is off is moved from P1 to P2.

Therefore, the leakage current of the sampling transistor Ts is suppressed, and the potentials of the nodes ND1 and ND2 are stabilized as shown in FIG. Thereby, the gate-source voltage Vgs of the drive transistor Td does not fluctuate, and the fluctuation of the drive current Ids with respect to the organic EL element 1 due to the leak current can be suppressed.
As a result, it is possible to provide an organic EL display device with uniform image quality that is free from deterioration due to leakage current such as roughness on the screen display.

As can be understood from the above, the leak suppression reference voltage Vofs2 is higher than the threshold correction reference voltage Vofs, so that the drain-source voltage Vds of the sampling transistor Ts is changed to the operation of FIG. Has a lower role than in the example.
Therefore, the potential of the leak suppression reference voltage Vofs2 should be set so that the operating point in the off region of the sampling transistor Ts becomes the operating point at which the leakage current is at a level that does not cause a problem.

[4. Pixel Circuit Operation of Second Embodiment]

FIG. 10 shows an operation example of the pixel circuit 10 as the second embodiment.
Also in the case of the second embodiment, the configuration of the display device and the configuration of the pixel circuit 10 are the same as those described with reference to FIGS.
However, the horizontal selector 11 performs binary driving of the threshold correction reference voltage Vofs and the video signal voltage Vsig on the signal line DTL.
In other words, the second embodiment is an example in which the leak suppression reference voltage Vofs2 is not used, and the video signal voltage Vsig is used instead of the leak suppression reference voltage Vofs2.

In the pixel circuit driving method of FIG. 10, the scan pulses WSa and WSb and the power supply pulse DS are the same as those in FIG.
The operation up to the period LT4 is the same. That is, the threshold correction preparation is performed in the period LT2, and the threshold correction operation is performed, for example, divided into four times in the period LT3 (LT3a to LT3d). Thereafter, in the period LT4, the writing of the video signal voltage Vsig and the mobility correction are performed.

Also in the second embodiment, after the video signal voltage Vsig writing and mobility correction are performed in the period LT4, the scan pulses WSa and WSb are set to the L level, the gate-source voltage Vgs is determined, and bootstrap and light emission are performed. Transition to a state (period LT5).
The write scanner 13 sets the second scanning pulse WSb to the H level during the bootstrap period after the writing of the video signal voltage Vsig. That is, when the first scanning pulse WSa is at L level and the second scanning pulse WSb is at H level, the sampling transistor Ts is turned off and the auxiliary switch Ts2 is turned on.
At this time, the video signal voltage Vsig is continuously applied to the signal line DTL. Therefore, the video signal voltage Vsig is input to the node ND3 and written to the leakage suppression capacitor C2.
Thereafter, before the voltage of the signal line DTL becomes the threshold correction reference voltage Vofs, the write scanner 13 returns the second scanning pulse WSb to the L level.

That is, in the second embodiment, at the light emission start stage, the node ND3 is set to the video signal voltage Vsig as a voltage higher than the threshold correction reference voltage Vofs. The video signal voltage Vsig is held in the leakage suppression capacitor C2 until the light emission in the period LT5 is completed, and the node ND3 is fixed to the video signal voltage Vsig.
Then, the potential difference between the drain and source of the sampling transistor Ts is the difference between the potential of the node ND1 due to the video signal voltage Vsig + bootstrap and the potential of the video signal voltage Vsig at the node ND3.
This potential difference is smaller than the potential difference between the potential of the node ND1 and the threshold correction reference voltage Vofs.

Thereby, the voltage difference applied between the drain and source of the sampling transistor Ts can be reduced, and the operating point through which the leak current flows can be relaxed.
Therefore, the leakage current of the sampling transistor Ts is suppressed, and the potentials of the nodes ND1 and ND2 in the period LT5 are stabilized as shown in FIG. Thereby, the gate-source voltage Vgs of the drive transistor Td does not fluctuate, and the fluctuation of the drive current Ids with respect to the organic EL element 1 due to the leak current can be suppressed.
As a result, it is possible to provide an organic EL display device with uniform image quality that is free from deterioration due to leakage current such as roughness on the screen display.
Further, in the case of the second embodiment, the horizontal selector 11 may be binary driven, and therefore the signal line driver configuration inside the horizontal selector 11 can be simplified.

Although the embodiments have been described above, the present invention is not limited to the above examples.
In the light emission drive examples of FIGS. 7 and 10, the threshold correction is performed four times in one light emission cycle. For example, there are examples of two times, three times, five times or more.
The leak suppression reference voltage Vofs2 or the video signal voltage Vsig is preferably written to the leak suppression capacitor C2 immediately after the video signal voltage Vsig is written as shown in FIGS. Even in the supply period of the leakage suppression reference voltage Vofs2 in the period (or the supply period of the video signal voltage Vsig), the leakage suppression effect is obtained to some extent.

  DESCRIPTION OF SYMBOLS 1 Organic EL element, 10 pixel circuit, 11 horizontal selector, 12 drive scanner, 13 light scanner, 20 pixel array part, Cs holding capacity, Ts sampling transistor, Td drive transistor, Ts2 auxiliary switch, C2 leakage suppression capacity

Claims (5)

A light emitting element, a driving transistor that applies a current according to a gate-source voltage to the light emitting element by applying a driving voltage between the drain and the source; and between the gate and the signal line of the driving transistor. The sampling transistor and auxiliary switch element that input the signal line voltage to the gate of the driving transistor by being electrically connected together, and the threshold voltage and input of the driving transistor connected between the gate and source of the driving transistor A pixel circuit having a storage capacitor for holding the video signal voltage and a leakage suppression capacitor connected to a connection point of the sampling transistor and the auxiliary switch element;
A signal selector for supplying a video signal voltage and a reference voltage as the signal line voltage to each signal line arranged in a column on a pixel array in which the pixel circuits are arranged in a matrix;
A drive control scanner that applies a power pulse to each power control line arranged in a row on the pixel array and applies a drive voltage to the drive transistor of the pixel circuit;
A first scan pulse is applied to a first write control line corresponding to the sampling transistor, which is arranged in a row on the pixel array, and a second scan control line corresponding to the auxiliary switch is provided with a first scan pulse. A writing scanner that applies two scanning pulses to control the sampling transistor and the auxiliary switch of the pixel circuit to execute input of a video signal voltage and a reference voltage to each pixel circuit;
With
The writing scanner causes the sampling transistor and the auxiliary switch element to conduct by the first and second scanning pulses when the signal selector applies the video signal voltage to the signal line, and the video signal voltage Is input to the gate of the driving transistor, and after the video signal voltage is written, the auxiliary switching element is turned on by the first and second scanning pulses while the sampling transistor is turned off, and the signal is supplied. A display device for writing a line voltage to the leakage suppression capacitor. The signal selector outputs a threshold correction reference voltage and a leak suppression reference voltage as the reference voltage,
After the writing of the video signal voltage, the writing scanner makes the sampling transistor non-conductive by the first and second scanning pulses when the signal selector gives the leak suppression reference voltage. The display device according to claim 1, wherein the auxiliary switch element is turned on in a state to write the leak suppression reference voltage in the leak suppression capacitor.   The display device according to claim 2, wherein the leak suppression reference voltage is higher than the threshold correction reference voltage.   The writing scanner makes the sampling transistor non-conductive by the first and second scanning pulses within a period after the video signal voltage is written and the signal selector applies the video signal voltage. The display device according to claim 1, wherein the auxiliary switch element is turned on in a state so that the video signal voltage is written to the leakage suppression capacitor. A light emitting element, a driving transistor that applies a current according to a gate-source voltage to the light emitting element by applying a driving voltage between the drain and the source; and between the gate of the driving transistor and a signal line The sampling transistor and auxiliary switch element that input the signal line voltage to the gate of the driving transistor by being electrically connected together, and the threshold voltage and input of the driving transistor connected between the gate and source of the driving transistor A pixel circuit having a storage capacitor for holding the video signal voltage and a leakage suppression capacitor connected to a connection point of the sampling transistor and the auxiliary switch element;
A signal selector for supplying a video signal voltage and a reference voltage as the signal line voltage to each signal line arranged in a column on a pixel array in which the pixel circuits are arranged in a matrix;
A drive control scanner that applies a power pulse to each power control line arranged in a row on the pixel array and applies a drive voltage to the drive transistor of the pixel circuit;
A first scan pulse is applied to a first write control line corresponding to the sampling transistor, which is arranged in a row on the pixel array, and a second scan control line corresponding to the auxiliary switch is applied to the second write control line. A writing scanner that applies two scanning pulses to control the sampling transistor and the auxiliary switch of the pixel circuit to execute input of a video signal voltage and a reference voltage to each pixel circuit;
As a display driving method for a display device comprising:
The writing scanner makes the sampling transistor and the auxiliary switch element conductive by the first and second scanning pulses when the signal selector applies the video signal voltage to the signal line, and the video signal voltage Is input to the gate of the drive transistor,
After the video signal voltage is written, the auxiliary switch element is turned on while the sampling transistor is turned off by the first and second scanning pulses, and the voltage of the signal line is written into the leakage suppression capacitor. Display driving method.

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