JP2018097236A - Display device, and driving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display device and driving method that suppress increase in power consumption attributed to correction actions.SOLUTION: A display device according to one embodiment of the present invention comprises: a plurality of pixels that includes a light emitting element and a pixel circuit, respectively; and a driving circuit that drives the plurality of pixels. In this display device, the pixel circuit has a diode element provided between an anode of the light emitting element and a control line. The driving circuit is configured to output a control signal including three types of voltage values to the control line, and thereby drive the plurality of pixels.SELECTED DRAWING: Figure 3

Description

  The present technology relates to a display device and a driving method.

  2. Description of the Related Art In recent years, in the field of display devices that perform video display, display devices using current-driven optical elements, such as organic EL (electroluminescence) elements, whose light emission luminance changes according to the value of a flowing current are used as light emitting elements of pixels. Developed and commercialized. Unlike a liquid crystal element or the like, the organic EL element is a self-luminous element. Therefore, since a display device (organic EL display device) using an organic EL element does not require a light source (backlight), it is lighter, thinner, and brighter than a liquid crystal display device that requires a light source. be able to. Furthermore, since the response speed of the organic EL element is very high, about several μs, no afterimage occurs when displaying a moving image. Therefore, organic EL display devices are expected to become the mainstream of next-generation flat panel displays.

  In an active matrix organic EL display device, each scanning line is sequentially scanned every horizontal period (1H), and a signal voltage corresponding to a video signal is sampled and written in a storage capacitor. That is, the signal voltage writing operation is performed by line sequential scanning of 1H cycle. Further, in the organic EL display device, when the threshold voltage and mobility of the driving transistor are different for each pixel, the light emission luminance of the organic EL element varies, and the uniformity of the screen is impaired. Therefore, in an active matrix organic EL display device, a correction operation for reducing variation in light emission luminance caused by variation in threshold voltage and mobility of a driving transistor is performed together with line sequential scanning of 1H cycle (Patent Document). 1).

JP 2009-145531 A

  Incidentally, the organic EL display device has a problem that power consumption increases due to the above-described correction operation.

  The present technology has been made in view of such a problem, and an object of the present technology is to provide a display device and a driving method capable of suppressing an increase in power consumption due to the above-described correction operation.

  A display device according to an embodiment of the present technology includes a plurality of pixels each including a light emitting element and a pixel circuit, and a drive circuit that drives the plurality of pixels. In this display device, the pixel circuit includes a driving transistor that controls a current flowing through the light emitting element, a writing transistor that controls application of a signal voltage corresponding to a video signal to the gate of the driving transistor, a gate of the driving transistor, and light emission. And a storage capacitor provided between the anode of the element. In this display device, the pixel circuit further includes a diode element provided between the anode of the light emitting element and the control line. The driving circuit drives a plurality of pixels by driving a plurality of pixels by outputting a control signal including three kinds of voltage values to the control line.

  A driving method according to an embodiment of the present technology is a method of driving a plurality of pixels each including a light emitting element and a pixel circuit. The pixel circuit of each pixel driven by this driving method includes a driving transistor that controls a current flowing through the light emitting element, a writing transistor that controls application of a signal voltage corresponding to a video signal to the gate of the driving transistor, and a driving transistor. And a storage capacitor provided between the gate of the light emitting element and the anode of the light emitting element. The above pixel circuit further includes a diode element provided between the anode of the light emitting element and the control line. This driving method includes a step of driving a plurality of pixels by outputting a control signal including three kinds of voltage values to a control line.

  In the display device and the driving method according to the embodiment of the present technology, a plurality of pixels are formed by applying a control signal including three kinds of voltage values to the diode elements connected in parallel to the light emitting elements in the pixel circuit. Driven. Thereby, for example, when a signal voltage is written to the gate of the driving transistor, an intermediate voltage value among the three voltage values can be output to the control line. As a result, for example, the diode element can be turned on at the time of writing the signal voltage at the high gradation while the diode element can be turned on at the time of writing the signal voltage at the high gradation, while the signal voltage can be lowered. It becomes.

  According to the display device and the driving method according to the embodiment of the present technology, a control signal including three kinds of voltage values is applied to the diode elements connected in parallel to the light emitting elements in the pixel circuit, so that a plurality of Since the pixels are driven, the signal voltage can be lowered. As a result, an increase in power consumption due to the correction operation can be suppressed. In addition, the effect of this technique is not necessarily limited to the effect described here, Any effect described in this specification may be sufficient.

1 is a schematic configuration diagram of a display device according to an embodiment of the present technology. It is a figure showing an example of the circuit composition of each pixel. It is a figure showing an example of the time-dependent change of the voltage applied to a scanning line, a power supply line, a signal line, and a control line when paying attention to one pixel, and a gate voltage and a source voltage of a driving transistor. It is a figure showing an example of operation of a pixel. It is a figure showing an example of operation of a pixel. It is a figure showing an example of operation of a pixel. It is a figure showing an example of operation of a pixel. It is a figure showing an example of operation of a pixel. It is a figure showing an example of the time-dependent change of the source voltage of a drive transistor. It is a figure showing an example of operation of a pixel. It is a figure showing an example of operation of a pixel. It is a figure showing an example of operation of a pixel. It is a figure showing an example of operation of a pixel. It is a figure showing the modification of the waveform of the voltage shown in FIG. It is a perspective view showing the external appearance of the application example of the display apparatus which concerns on the said embodiment and its modification.

Hereinafter, modes for carrying out the present technology will be described in detail with reference to the drawings. The description will be given in the following order.

1. Embodiment (display device)
2. Modified example (display device)
3. Application example (electronic equipment)

<1. Embodiment>
[Constitution]
FIG. 1 illustrates a schematic configuration of a display device 1 according to an embodiment of the present technology. The display device 1 includes, for example, a pixel array unit 10, a controller 20, and a driver 30. The controller 20 and the driver 30 correspond to a specific example of a “drive circuit” of the present technology. The pixel array unit 10 includes a plurality of pixels 11 arranged in a matrix. The controller 20 and the driver 30 drive the plurality of pixels 11 based on the video signal Din and the synchronization signal Tin input from the outside.

(Pixel array unit 10)
FIG. 2 illustrates an example of a circuit configuration of each pixel 11 included in the pixel array unit 10. The pixel array unit 10 displays an image based on the video signal Din and the synchronization signal Tin input from the outside, as each pixel 11 is driven in an active matrix by the controller 20 and the driver 30. The pixel array unit 10 includes a plurality of scanning lines WSL and a plurality of control lines CTL extending in the row direction, and a plurality of signal lines DTL extending in the column direction. The pixel array unit 10 further includes a plurality of pixels 11 that are provided one for each portion where the scanning line WSL and the signal line DTL intersect each other.

  The scanning line WSL is used for selecting each pixel 11, and supplies a selection pulse for selecting each pixel 11 for each predetermined unit (for example, a pixel row) to each pixel 11. The signal line DTL is used to supply a signal voltage Vsig corresponding to the video signal Din to each pixel 11 and supplies a data pulse including the signal voltage Vsig to each pixel 11. The control line CTL supplies a control pulse for controlling on / off of a diode element Tr3 described later to each pixel 11.

  Each pixel 11 includes, for example, a pixel circuit 12 and an organic EL element 13. The organic EL element 13 corresponds to a specific example of “light emitting element” of the present technology. The organic EL element 13 has, for example, a configuration in which an anode electrode, an organic layer, and a cathode electrode are sequentially stacked. The organic EL element 13 has an element capacitance (element capacitance Cel described later). The pixel circuit 12 controls light emission / extinction of the organic EL element 13. The pixel circuit 12 has a function of holding a voltage written to each pixel 11 by writing scanning described later. The pixel circuit 12 includes, for example, a drive transistor Tr1, a write transistor Tr2, a diode element Tr3, and a storage capacitor Cs.

  The write transistor Tr2 controls application of the signal voltage Vsig corresponding to the video signal Din to the gate of the drive transistor Tr1. Specifically, the write transistor Tr2 samples the voltage of the signal line DTL and writes the voltage obtained by the sampling to the gate of the drive transistor Tr1. The drive transistor Tr1 is connected to the organic EL element 13 in series. The drive transistor Tr1 drives the organic EL element 13. The drive transistor Tr1 controls the current flowing through the organic EL element 13 according to the magnitude of the voltage sampled by the write transistor Tr2.

  The holding capacitor Cs holds a predetermined voltage between the gate and source of the driving transistor Tr1. The storage capacitor Cs is provided between the gate of the drive transistor Tr1 and the anode of the organic EL element 13. The diode element Tr3 controls the anode voltage of the organic EL element 13 (or the source voltage Vs of the drive transistor Tr1). The diode element Tr3 is provided between the anode of the organic EL element 13 (or the source of the drive transistor Tr1) and the control line CTL. Therefore, the diode element Tr3 causes a current (through current) that passes through the drive transistor Tr1 and the diode element Tr3 to flow when the diode element Tr3 is turned on, and stops the through current when the diode element Tr3 is turned off. Note that the pixel circuit 12 may have a circuit configuration in which various capacitors and transistors are added to the above-described 3Tr1C circuit, or may have a circuit configuration different from the above-described 3Tr1C circuit configuration.

  The drive transistor Tr1 and the write transistor Tr2 are formed of, for example, an n-channel MOS thin film transistor (TFT (Thin Film Transistor)). The diode element Tr3 is formed, for example, of an n-channel MOS thin film transistor in which the gate and the source or drain are short-circuited. Note that these transistors may be formed of p-channel MOS TFTs. Although the following description is given on the assumption that these transistors are enhancement type, these transistors may be depletion type.

  Each signal line DTL is connected to an output terminal of a horizontal selector 31 (to be described later) and a source or drain of the write transistor Tr2. Each scanning line WSL is connected to an output terminal of a later-described write scanner 32 and a gate of the write transistor Tr2. Each control line CTL is connected to an output terminal of a control scanner 33 described later and a diode element Tr3.

  The gate of the writing transistor Tr2 is connected to the scanning line WSL. The source or drain of the write transistor Tr2 is connected to the signal line DTL. Of the source and drain of the write transistor Tr2, a terminal not connected to the signal line DTL is connected to the gate of the drive transistor Tr1. The source or drain of the drive transistor Tr1 is connected to the power supply line of the voltage Vcc. Of the source and drain of the drive transistor Tr1, a terminal not connected to the power supply line of the voltage Vcc is connected to the anode of the organic EL element 13. One end of the storage capacitor Cs is connected to the gate of the drive transistor Tr1. The other end of the storage capacitor Cs is connected to the anode of the organic EL element 13. The other end of the storage capacitor Cs is further connected to a terminal of the source and drain of the diode element Tr3 that is short-circuited with the gate of the diode element Tr3. Of the source and drain of the diode element Tr3, the terminal that is short-circuited to the gate of the diode element Tr3 is connected to the storage capacitor Cs and the anode of the organic EL element 13. Of the source and drain of the diode element Tr3, a terminal not connected to the storage capacitor Cs is connected to the control line CTL.

  The driver 30 includes, for example, a horizontal selector 31, a write scanner 32, and a control scanner 33.

  The horizontal selector 31 applies the analog signal voltage Vsig input from the video signal processing circuit 21 to each signal line DTL in response to (in synchronization with) the input of the control signal. For example, the horizontal selector 31 can output two types of voltages (Vofs, Vsig). For example, the horizontal selector 31 supplies two types of voltages (Vofs, Vsig) to the pixel 11 selected by the write scanner 32 via the signal line DTL.

  The signal voltage Vsig has a voltage value corresponding to the video signal Din. The minimum voltage of the signal voltage Vsig is a voltage value lower than the fixed voltage Vofs, and the maximum voltage of the signal voltage Vsig is a voltage value higher than the fixed voltage Vofs. The fixed voltage Vofs is a constant voltage unrelated to the video signal Din. The fixed voltage Vofs has a value smaller than the sum (Vcat + Vthel + Vth) of the cathode voltage Vcat of the organic EL element 13, the threshold voltage Vthel of the organic EL element 13, and the threshold voltage Vth of the drive transistor Tr1. The horizontal selector 31 outputs a data pulse including the signal voltage Vsig to each signal line DTL every horizontal period. The horizontal selector 31 outputs a pulse composed of two values of the signal voltage Vsig and the fixed voltage Vofs to each signal line DTL as a data pulse.

  The light scanner 32 scans the plurality of pixels 11 for each predetermined unit. For example, the write scanner 32 sequentially outputs a selection pulse to each scanning line WSL in one frame period. The write scanner 32 selects, for example, a plurality of scanning lines WSL in a predetermined sequence according to the input of the control signal (synchronously), thereby preparing threshold correction, threshold correction, writing and moving the signal voltage Vsig. The degree correction and the light emission are executed in a desired order.

  The threshold correction preparation refers to initializing the gate voltage of the drive transistor Tr1 (specifically, Vofs) and initializing the source voltage of the drive transistor Tr1. The threshold correction refers to a correction operation for bringing the gate-source voltage Vgs of the driving transistor Tr1 closer to the threshold voltage of the driving transistor Tr1. The writing of the signal voltage Vsig (signal writing) refers to an operation of writing the signal voltage Vsig to the gate of the driving transistor Tr1 via the writing transistor Tr2. Mobility correction refers to an operation of correcting the voltage (gate-source voltage Vgs) held between the gate and source of the drive transistor Tr1 in accordance with the mobility of the drive transistor Tr1. The signal writing and the mobility correction may be performed at separate timings. In the present embodiment, the write scanner 32 outputs one selection pulse to the scanning line WSL, so that signal writing and mobility correction are performed simultaneously (or continuously without gaps). ing.

  For example, the write scanner 32 can output two kinds of voltages (Von, Voff). For example, the write scanner 32 supplies two types of voltages (Von, Voff) to the pixel 11 to be driven via the scanning line WSL, and performs on / off control of the writing transistor Tr2. The on-voltage Von is a value equal to or higher than the on-voltage of the write transistor Tr2. The on-voltage Von is a peak value of a selection pulse output from the write scanner 32 during a “threshold correction preparation period”, a “threshold correction period”, a “signal writing / mobility correction period”, which will be described later. The off voltage Voff has a value lower than the on voltage of the write transistor Tr2 and a value lower than the on voltage Von.

  The control scanner 33 sequentially outputs control pulses to the plurality of control lines CTL for each predetermined unit in response to (in synchronization with) the input of the control signal. For example, the control scanner 33 sequentially outputs control pulses to the control lines CTL in one frame period. The control scanner 33 outputs control pulses in a predetermined sequence to a plurality of control lines CTL, for example, and cooperates with the write scanner 32 to prepare threshold correction, write threshold voltage, and write signal voltage Vsig. , Mobility correction and light emission are executed in a desired order.

  The control scanner 33 can output control pulses including three kinds of voltage values (Vdd, Vmid, Vss). For example, the control scanner 33 can output control pulses composed of three types of voltages (Vdd, Vmid, Vss). For example, the control scanner 33 supplies three types of voltages (Vdd, Vmid, Vss) to each pixel 11 via the control line CTL. When the control scanner 33 writes the signal voltage Vsig to the gate of the drive transistor Tr1, the control scanner 33 outputs an intermediate voltage value (Vmid) among the three types of voltage values (Vdd, Vmid, Vss) to the control line CTL. When the organic EL element 13 emits light, the control scanner 33 outputs the highest voltage value (Vdd) among the three types of voltage values (Vdd, Vmid, Vss) to the control line CTL. The control scanner 33 has the lowest voltage value among the three voltage values (Vdd, Vmid, Vss) immediately before performing the correction operation for bringing the gate-source voltage Vgs of the drive transistor Tr1 closer to the threshold voltage Vth of the drive transistor Tr1. (Vss) is output to the control line CTL.

The fixed voltage Vdd is larger than the difference (Vel−VthD) between the anode voltage Vel of the organic EL element 13 and the threshold voltage VthD of the diode element Tr3. The fixed voltage Vss is smaller than the difference (Vel−VthD) between the anode voltage Vel of the organic EL element 13 and the threshold voltage VthD of the diode element Tr3. The fixed voltage Vmid is a value larger than the fixed voltage Vss and smaller than the fixed voltage Vdd. The fixed voltage Vmid is larger than the difference (Vofs−Vth−VthD) between the fixed voltage Vofs and the threshold voltage Vth + VthD. Furthermore, the fixed voltage Vmid has a value that turns off the diode element Tr3 when the signal voltage Vsig is written when the video signal Din has a low gradation, and the signal voltage when the video signal Din has a high gradation. The diode element Tr3 is turned on when Vsig is written. Specifically, the fixed voltage Vmid is a value that satisfies the following expression (1).
Vmid + VthD <Vcat + Vel (1)

(Controller 20)
Next, the controller 20 will be described. The controller 20 includes, for example, a video signal processing circuit 21, a timing generation circuit 22, and a power supply circuit 23. For example, the video signal processing circuit 21 performs a predetermined correction on a digital video signal Din input from the outside, and generates a signal voltage Vsig based on the video signal obtained thereby. For example, the video signal processing circuit 21 outputs the generated signal voltage Vsig to the horizontal selector 31. Examples of the predetermined correction include gamma correction and overdrive correction. The timing generation circuit 22 controls the circuits in the driver 30 so as to operate in conjunction with each other. For example, the timing generation circuit 22 outputs a control signal to each circuit in the driver 30 in response to (in synchronization with) the synchronization signal Tin input from the outside. The power supply circuit 23 generates and supplies various fixed voltages necessary for various circuits such as the horizontal selector 31, the write scanner 32, the control scanner 33, the video signal processing circuit 21, and the timing generation circuit 22.

[Operation]
Next, the operation (operation from quenching to light emission) of the display device 1 of the present embodiment will be described. In the present embodiment, even if the IV characteristics of the organic EL element 13 change over time, the organic EL element 13 is not affected by the change so that the emission luminance of the organic EL element 13 is kept constant. The compensation operation for the fluctuation of the IV characteristic is incorporated. Furthermore, in the present embodiment, even if the threshold voltage and mobility of the drive transistor Tr1 change with time, the above-described in order to keep the light emission luminance of the organic EL element 13 constant without being affected by them, It incorporates a correction operation for the threshold voltage and the mobility fluctuation.

  FIG. 3 shows an example of changes over time in the voltage applied to the scanning line WSL, the signal line DTL, and the control line CTL, and the gate voltage Vg and the source voltage Vs of the driving transistor Tr1 when focusing on one pixel 11. It is. 4 to 8 and FIGS. 9 to 13 illustrate an example of the operation of the pixel 11. FIG. 9 shows an example of a change with time of the source voltage Vs of the drive transistor Tr1.

  First, the controller 20 and the driver 30 prepare for threshold correction to bring the gate-source voltage Vgs of the drive transistor Tr1 close to the threshold voltage Vth of the drive transistor Tr1. Prior to preparation for threshold correction, the organic EL element 13 emits light. At this time, the voltage of the scanning line WSL is Voff, and the voltage of the control line CTL is Vdd (FIG. 4). Since Vdd is larger than Vel−VthD, the diode element Tr3 is off. Since the drive transistor Tr1 operates in the saturation region, the current Ids flowing through the organic EL element 13 has a value corresponding to the magnitude of the gate-source voltage Vgs of the drive transistor Tr1.

  The controller 20 and the driver 30 extinguish the organic EL element 13 before starting preparation for threshold correction. Specifically, the write scanner 32 increases the voltage of the scanning line WSL from Voff to Von according to the control signal (T1, FIG. 5). Then, the gate voltage Vg decreases to Vofs. Since Vofs has a value smaller than Vcat + Vthel + Vth, the drive transistor Tr1 is turned off. Furthermore, the anode voltage Vel (or the source voltage Vs of the drive transistor Tr1) gradually decreases due to self-discharge and finally becomes Vcat + Vthel.

  After a certain period of time, the voltage of the control line CTL is lowered from Vdd to Vss (T2, FIG. 6). Since Vss is smaller than Vel-VthD, the diode element Tr3 is turned on. As a result, a current flows through the diode element Tr3, and the anode voltage Vel (or the source voltage Vs of the drive transistor Tr1) becomes Vss + VthD.

(Threshold correction preparation period)
Next, when the voltage of the signal line DTL is Vofs and the voltage of the control line CTL is Vss, the write scanner 32 increases the voltage of the scanning line WSL from Voff to Von according to the control signal. (T3, FIG. 7). Then, the gate voltage Vg changes to Vofs. At this time, the values of Vofs and Vss are set so that the gate-source voltage Vgs of the drive transistor Tr1 is larger than Vth of the drive transistor Tr1. Therefore, the drive transistor Tr1 is turned on, a current (through current) that passes through the drive transistor Tr1 and the diode element Tr3 flows, and the anode voltage Vel becomes Vss + VthD + ΔV. Here, ΔV corresponds to a voltage drop amount in the diode element Tr3.

(Threshold correction period)
Subsequently, the controller 20 and the driver 30 perform a threshold value correction operation of the drive transistor Tr1. Specifically, when the voltage of the signal line DTL is Vofs and the voltage of the scanning line WSL is Von, the control scanner 33 changes the voltage of the control line CTL from Vss to Vmid according to the control signal. (T4, FIG. 8). Vmid is a value larger than Vofs−Vth−VthD, and further satisfies the above formula (1). Then, the diode element Tr3 is turned off, and a current as shown in FIG. 8 flows. At this time, since Vel ≦ Vcat + Vthel, the current flowing through the driving transistor Tr1 is used to charge the storage capacitor Cs and the element capacitor Cel. At this time, the anode voltage Vel (or the source voltage Vs of the drive transistor Tr1) increases as time passes, for example, as shown in FIG. As a result, the gate voltage Vg becomes Vofs, the storage capacitor Cs and the element capacitor Cel are charged, and the gate-source voltage Vgs approaches Vth. On the other hand, since the organic EL element 13 is reverse-biased, the organic EL element 13 does not emit light.

  Thereafter, the write scanner 32 reduces the voltage of the scanning line WSL from Von to Voff in accordance with the control signal (T5, FIG. 10). Then, the gate of the drive transistor Tr1 becomes floating. At this time, since the gate-source voltage Vgs is still larger than the threshold voltage Vth of the drive transistor Tr1, a current continues to flow between the drain and source of the drive transistor Tr1, and the storage capacitor Cs continues to be charged. Therefore, the gate voltage Vg and the source voltage Vs of the drive transistor Tr1 continue to rise. On the other hand, since the organic EL element 13 is reverse-biased, the organic EL element 13 does not emit light.

  Thereafter, when the voltage of the signal line DTL becomes Vofs again, the write scanner 32 raises the voltage of the scanning line WSL from Voff to Von according to the control signal, and corrects the threshold value of the driving transistor Tr1. The controller 20 and the driver 30 thus repeatedly perform threshold correction. As a result, the gate voltage Vg becomes Vofs, the storage capacitor Cs is charged to Vth, and the gate-source voltage Vgs becomes Vth. At this time, the anode voltage Vel (or the source voltage Vs of the drive transistor Tr1) is Vofs−Vth, which is equal to or less than Vthel + Vcat. Therefore, at this time, the organic EL element 13 does not emit light.

  Thereafter, before the horizontal selector 31 switches the voltage of the signal line DTL from Vofs to Vsig according to the control signal, the write scanner 32 decreases the voltage of the scanning line WSL from Von to Voff according to the control signal (T6). Then, since the gate of the driving transistor Tr1 is in a floating state, the gate-source voltage Vgs can be maintained at Vth regardless of the magnitude of the voltage of the signal line DTL. In this way, by setting the gate-source voltage Vgs to Vth, even if the threshold voltage Vth of the drive transistor Tr1 varies for each pixel circuit 12, the emission luminance of the organic EL element 13 varies. Can be eliminated.

(Waiting period)
Thereafter, during the standby period, the horizontal selector 31 switches the voltage of the signal line DTL from Vofs to Vsig.

(Signal writing / mobility correction period)
After the standby period ends (that is, after the threshold correction is completed), the controller 20 and the driver 30 perform writing of the signal voltage Vsig corresponding to the video signal Din and mobility correction. Specifically, while the voltage of the signal line DTL is Vsig, the write scanner 32 raises the voltage of the scanning line WSL from Voff to Von according to the control signal (T7), and the gate of the drive transistor Tr1 is raised. Connect to signal line DTL. Then, the gate voltage Vg of the drive transistor Tr1 becomes the voltage Vsig of the signal line DTL.

  At this time, when the signal voltage Vsig is large, that is, when the video signal Din has a high gradation, the increase amount of the anode voltage Vel (or the source voltage Vs of the drive transistor Tr1) increases. At this time, Vmid is a value that turns on the diode element Tr3 when the signal voltage Vsig is written. That is, Vmid is set so that the anode voltage Vel (or the source voltage Vs of the drive transistor Tr1) exceeds Vmid + VthD. Therefore, the diode element Tr3 is turned on. Since Vmid satisfies the above formula (1), the organic EL element 13 does not turn on.

  Thus, when the diode element Tr3 is turned on during the mobility correction, a through current as shown in FIG. 11 flows, and the node voltage Vel (or the source voltage Vs of the drive transistor Tr1) gradually increases. As a result, the gate-source voltage Vgs of the drive transistor Tr1 does not decrease during mobility correction.

  On the other hand, when the signal voltage Vsig is small, that is, when the video signal Din has a low gradation, the increase amount of the anode voltage Vel (or the source voltage Vs of the drive transistor Tr1) is small. At this time, when the anode voltage Vel (or the source voltage Vs of the driving transistor Tr1) has a gradation that does not exceed Vmid + VthD, the diode element Tr3 remains off. Therefore, the through current as shown in FIG. 11 does not flow, and the current as shown in FIG. 12 flows. As a result, the drain-source current flows through the storage capacitor Cs and the element capacitor Cel of the organic EL element 13, and the storage capacitor Cs and the element capacitor Cel are charged, so that the source voltage Vs increases. Therefore, when the video signal Din has a low gradation, normal mobility correction is performed.

  Thus, in the present embodiment, normal mobility correction is performed at the time of low gradation, and mobility correction different from the normal is performed at the time of high gradation. In general, streaks and unevenness in the screen display are easily visible when the gradation is low, and are hardly visible when the gradation is high. Therefore, even when mobility correction different from normal is performed at the time of high gradation, there is no significant deterioration in image quality.

(Light emission)
Next, the write scanner 32 lowers the voltage of the scanning line WSL from Von to Voff according to the control signal (T8). Then, the gate of the drive transistor Tr1 becomes floating, the current Ids flows between the drain and source of the drive transistor Tr1, the source voltage Vs rises, and accordingly the gate voltage Vg also rises. Immediately thereafter, the control scanner 33 increases the voltage of the control line CTL from Vmid to Vdd in response to the control signal (T9, FIG. 13). Then, the driving transistor Tr1 passes a constant current Ids ′ through the organic EL element 13, and the source voltage Vs rises to a voltage Vx through which the current Ids ′ flows through the organic EL element 13, so that the organic EL element 13 has a desired luminance. Emits light.

[effect]
Next, the effect in the display apparatus 1 of this Embodiment is demonstrated.

  In an organic EL display device, a correction operation for reducing variation in light emission luminance caused by variation in threshold voltage or mobility of a drive transistor is usually performed. Mobility correction, which is one of the correction operations, is performed by changing the source voltage of the driving transistor with its own current. For this reason, a loss is caused by the mobility correction amount (source increase amount) with respect to the applied signal voltage Vsig. The mobility correction is performed simultaneously with the signal writing operation, and the signal writing operation and the mobility correction operation cannot be performed separately. Therefore, in order to cause the organic EL element to emit light with high luminance, it is necessary to set the signal voltage to a larger value, and there is a problem that the power consumption increases accordingly.

  On the other hand, in the present embodiment, a plurality of control signals including three kinds of voltage values (Vdd, Vmid, Vss) are applied to the diode element Tr3 connected in parallel to the organic EL element 13 in the pixel circuit 12, thereby providing a plurality of control signals. Of the pixels 12 are driven. Thereby, for example, when the signal voltage Vsig is written to the gate of the drive transistor Tr1, it is possible to output an intermediate voltage value (Vmid) among the three types of voltage values (Vdd, Vmid, Vss) to the control line CTL. It becomes. As a result, for example, the diode element Tr3 is not turned on when the signal voltage Vsig at the time of low gradation is written, while the diode element Tr3 can be turned on at the time of writing the signal voltage Vsig at the time of high gradation. Therefore, since the signal voltage Vsig can be lowered, an increase in power consumption due to the correction operation can be suppressed.

  In the present embodiment, the intermediate voltage value (Vmid) is a value at which the diode element Tr3 is turned off when the signal voltage Vsig is written when the video signal Din has a low gradation. Further, the intermediate voltage value (Vmid) is a value that turns on the diode element Tr3 when the signal voltage Vsig is written when the video signal Din has a high gradation. As a result, the signal voltage Vsig can be lowered, and an increase in power consumption caused by the correction operation can be suppressed.

  Further, in the present embodiment, the intermediate voltage value (Vmid) is a value that satisfies the above equation (1). As a result, the signal voltage Vsig can be lowered, and an increase in power consumption caused by the correction operation can be suppressed.

  In the present embodiment, when the organic EL element 13 is caused to emit light, the highest voltage value (Vdd) among the three voltage values (Vdd, Vmid, Vss) is output to the control line CTL. Further, immediately before the correction operation for bringing the gate-source voltage Vgs of the drive transistor Tr1 close to the threshold voltage Vth of the drive transistor Tr1, the lowest voltage value (Vss) of the three voltage values (Vdd, Vmid, Vss). Is output to the control line CTL. As a result, the signal voltage Vsig can be lowered only by applying a control pulse including three kinds of voltage values (Vdd, Vmid, Vss) to the diode element Tr3 while the pixel circuit 12 has a conventional circuit configuration. It becomes possible. As a result, an increase in power consumption due to the correction operation can be suppressed.

<2. Modification>
Below, the various modifications of the display apparatus 1 of the said embodiment are demonstrated. In the following description, the same reference numerals are given to components common to the display device 1 of the above embodiment. Furthermore, description of components common to the display device 1 of the above embodiment is omitted as appropriate.

  In the above embodiment, the control scanner 33 may output the highest voltage value (Vdd) among the three types of voltage values (Vdd, Vmid, Vss) to the control line CTL during the threshold correction period. At this time, for example, as shown in FIG. 14, the control scanner 33 outputs the fixed voltage Vmid to the control line CTL during a period including at least the completion of writing (T8) in the writing period (T7 to T8). Also good. Even in this case, for example, the diode element Tr3 is turned off when the signal voltage Vsig at the time of low gradation is written, while the diode element Tr3 is turned on when the signal voltage Vsig at the time of high gradation is written. it can. Therefore, since the signal voltage Vsig can be lowered, an increase in power consumption due to the correction operation can be suppressed.

<3. Application example>
Hereinafter, application examples of the display device 1 described in the above embodiment and its modified examples (hereinafter referred to as “the above embodiment and the like”) will be described. The display device 1 according to the above embodiment is a television device, a digital camera, a notebook personal computer, a mobile terminal device such as a mobile phone, or a video camera, such as an externally input video signal or an internally generated video signal. The present invention can be applied to display devices for electronic devices in various fields that display images or videos.

  FIG. 15 illustrates a schematic configuration example of the electronic device 2 according to this application example. The electronic device 2 is, for example, a notebook personal computer that includes a display surface 2A on the main surface of one of two foldable plate-like housings. The electronic device 2 includes the display device 1 according to the above-described embodiment. For example, the electronic device 2 includes the pixel array unit 10 at the position of the display surface 2A. In this application example, since the display device 1 is provided, variation in light emission luminance can be reduced. Further, in the display device 1, even when the pixel array unit 10 has a high definition, variations in light emission luminance can be reduced.

  While the present technology has been described with the embodiment, the modification, and the application example, the present technology is not limited to the embodiment and the like, and various modifications can be made. In addition, the effect described in this specification is an illustration to the last. The effect of this technique is not limited to the effect described in this specification. The present technology may have effects other than those described in the present specification.

For example, this technique can take the following composition.
(1)
A plurality of pixels each including a light emitting element and a pixel circuit;
A drive circuit for driving a plurality of the pixels,
The pixel circuit includes:
A driving transistor for controlling a current flowing in the light emitting element;
A writing transistor for controlling application of a signal voltage corresponding to a video signal to the gate of the driving transistor;
A storage capacitor provided between the gate of the driving transistor and the anode of the light emitting element;
A diode element provided between an anode of the light emitting element and a control line;
The driving circuit drives a plurality of the pixels by outputting a control signal including three kinds of voltage values to the control line.
(2)
The display device according to (1), wherein the drive circuit outputs an intermediate voltage value of the three types of voltage values to the control line when writing the signal voltage to the gate of the drive transistor.
(3)
The intermediate voltage value is a value that turns off the diode element when the signal voltage is written when the video signal has a low gradation, and the signal when the video signal has a high gradation. The display device according to (2), wherein the diode element is turned on when voltage is written.
(4)
The display device according to (3), wherein the intermediate voltage value satisfies the following expression.
Vmid + VthD <Vcat + Vel
Vmid: intermediate voltage value VthD: threshold voltage Vcat of the diode element: cathode voltage Vel of the light emitting element: anode voltage of the light emitting element (5)
When the light emitting element emits light, the driving circuit outputs the highest voltage value among the three kinds of voltage values to the control line, and sets the gate-source voltage of the driving transistor as a threshold voltage of the driving transistor. The display device according to any one of (2) to (4), wherein the lowest voltage value among the three types of voltage values is output to the control line immediately before performing the correction operation to approach.
(6)
A driving method for driving a plurality of pixels each including a light emitting element and a pixel circuit,
The pixel circuit includes:
A driving transistor for controlling a current flowing in the light emitting element;
A writing transistor for controlling application of a signal voltage corresponding to a video signal to the gate of the driving transistor;
A storage capacitor provided between the gate of the driving transistor and the anode of the light emitting element;
A diode element provided between an anode of the light emitting element and a control line;
A driving method including a step of driving a plurality of the pixels by outputting a control signal including three kinds of voltage values to the control line.
(7)
In the step, when writing the signal voltage to the gate of the driving transistor, an intermediate voltage value among the three types of voltage values is output to the control line.
(8)
The intermediate voltage value is a value that turns off the diode element when the signal voltage is written when the video signal has a low gradation, and the signal when the video signal has a high gradation. The driving method according to (7), wherein the diode element is turned on when a voltage is written.
(9)
The intermediate voltage value is a value satisfying the following expression (8).
Vmid + VthD <Vcat + Vel
Vmid: intermediate voltage value VthD: threshold voltage Vcat of the diode element: cathode voltage Vel of the light emitting element: anode voltage of the light emitting element (10)
When the light emitting element emits light, the highest voltage value among the three kinds of voltage values is output to the control line, and a correction operation is performed to bring the gate-source voltage of the driving transistor closer to the threshold voltage of the driving transistor. The drive method according to any one of (7) to (9), wherein the lowest voltage value of the three types of voltage values is output to the control line immediately before.

  DESCRIPTION OF SYMBOLS 1 ... Display apparatus, 2 ... Electronic device, 2A ... Display surface, 10 ... Pixel array part, 11 ... Pixel, 12 ... Pixel circuit, 13 ... Organic EL element, 20 ... Controller, 21 ... Video signal processing circuit, 22 ... Timing Generation circuit, 23 ... Power supply circuit, 30 ... Driver, 31 ... Horizontal selector, 32 ... Write scanner, 33 ... Control scanner, Cel ... Element capacitance, Cs ... Retention capacitance, Cgs ... Gate-source capacitance, CTL ... Control line, Din ... video signal, DTL ... signal line, Ids, Ids' ... current, T1, T2, T3, T4, T5, T6, T7, T8, T9 ... time, Tin ... sync signal, Tr1 ... drive transistor, Tr2 ... write Transistor, Tr3 ... Control transistor, Vcat ... Cathode voltage, Vcc, Vdd, Vofs, Vmid, Vss ... Fixed voltage, Vel ... Anode Voltage, Vg ... gate voltage, Vgs ... gate-source voltage, Von ... on voltage, Voff ... off voltage, Vs ... source voltage, Vsig ... signal voltage, Vth, VthD, Vthel ... threshold voltage, WSL ... scanning line, [Delta] V ... Voltage drop.

Claims (10)

A plurality of pixels each including a light emitting element and a pixel circuit;
A drive circuit for driving a plurality of the pixels,
The pixel circuit includes:
A driving transistor for controlling a current flowing in the light emitting element;
A writing transistor for controlling application of a signal voltage corresponding to a video signal to the gate of the driving transistor;
A storage capacitor provided between the gate of the driving transistor and the anode of the light emitting element;
A diode element provided between an anode of the light emitting element and a control line;
The driving circuit drives a plurality of the pixels by outputting a control signal including three kinds of voltage values to the control line. The display device according to claim 1, wherein the drive circuit outputs an intermediate voltage value of the three types of voltage values to the control line when writing the signal voltage to the gate of the drive transistor. The intermediate voltage value is a value that turns off the diode element when the signal voltage is written when the video signal has a low gradation, and the signal when the video signal has a high gradation. The display device according to claim 2, wherein the diode element has a value that turns on when a voltage is written. The display device according to claim 3, wherein the intermediate voltage value is a value satisfying the following expression.
Vmid + VthD <Vcat + Vel
Vmid: intermediate voltage value VthD: threshold voltage Vcat of the diode element: cathode voltage Vel of the light emitting element Vel: anode voltage of the light emitting element When the light emitting element emits light, the driving circuit outputs the highest voltage value among the three kinds of voltage values to the control line, and sets the gate-source voltage of the driving transistor as a threshold voltage of the driving transistor. The display device according to claim 2, wherein the lowest voltage value of the three types of voltage values is output to the control line immediately before performing the correction operation to approach the display device. A driving method for driving a plurality of pixels each including a light emitting element and a pixel circuit,
The pixel circuit includes:
A driving transistor for controlling a current flowing in the light emitting element;
A writing transistor for controlling application of a signal voltage corresponding to a video signal to the gate of the driving transistor;
A storage capacitor provided between the gate of the driving transistor and the anode of the light emitting element;
A diode element provided between an anode of the light emitting element and a control line;
A driving method for driving a plurality of the pixels by outputting a control signal including three kinds of voltage values to the control line. The driving method according to claim 6, wherein in the step, when writing the signal voltage to the gate of the driving transistor, an intermediate voltage value among the three kinds of voltage values is output to the control line. The intermediate voltage value is a value that turns off the diode element when the signal voltage is written when the video signal has a low gradation, and the signal when the video signal has a high gradation. The driving method according to claim 7, wherein the diode element is turned on when a voltage is written. The driving method according to claim 8, wherein the intermediate voltage value is a value satisfying the following expression.
Vmid + VthD <Vcat + Vel
Vmid: intermediate voltage value VthD: threshold voltage Vcat of the diode element: cathode voltage Vel of the light emitting element Vel: anode voltage of the light emitting element When the light emitting element emits light, the highest voltage value among the three kinds of voltage values is output to the control line, and a correction operation is performed to bring the gate-source voltage of the driving transistor closer to the threshold voltage of the driving transistor. The driving method according to claim 7, wherein the lowest voltage value among the three types of voltage values is output to the control line immediately before.

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