JP2008292546A - Cathode potential control device, self-luminous display device, electronic equipment and cathode potential control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To optimize the power consumption of a display panel with consideration for deterioration characteristic of a light emitting element while maintaining peak luminance level constant. <P>SOLUTION: The control device for a common cathode potential to be applied to a self-luminous display panel which drive-controls light emitting state of each pixel by an active matrix drive method includes: (a) a cathode potential determination part for determining a cathode potential value for canceling a change with time of a voltage generated between an anode electrode and a cathode electrode of a self-luminous element at the time of light emitting operation and also operating a driving transistor of the self-luminous element in a saturated region according to a measurement value of the change with time; and (b) a cathode potential application part for generating a cathode potential corresponding to the determined cathode potential value, and supplying it to a common cathode electrode of the self-luminous display panel. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The invention described in this specification relates to a technique for optimizing the power consumption of a self-luminous display panel in which the light emission state of each pixel is driven and controlled by an active matrix driving method in accordance with the deterioration state of each pixel.
The invention has aspects as a cathode potential control device, a self-luminous display device, an electronic device, and a cathode potential control method.

  Today, various types of flat panel displays are in practical use. One of these is an organic EL panel in which organic EL (Electro Luminescence) elements are arranged in a matrix in a display area. The organic EL panel is not only light and easy to thin, but also has a high response speed and excellent moving image display characteristics. Thus, the organic EL panel has various characteristics required for the next generation display device.

  By the way, it is known that the current-voltage (IV) characteristic of an organic EL element changes with progress of deterioration. FIG. 1 shows the time change of the current-voltage characteristics of the organic EL element. As shown in FIG. 1, even when the driving current is the same, the voltage Vel generated between the anode electrode and the cathode electrode of the organic EL element gradually increases.

  This voltage change is mainly caused by the deterioration of the organic EL element. As characteristics common to self-luminous elements, organic EL elements also deteriorate in proportion to the length of use. One of the deterioration phenomena is an increase in voltage generated between both electrodes of the organic EL element. The deterioration phenomenon also appears as a decrease in peak luminance level.

  However, the traveling speed is not uniform, and as a general characteristic of a self-luminous element, the traveling speed tends to increase as the screen brightness increases. In addition, as a characteristic of the organic EL element, the deterioration tends to be accelerated as the environmental temperature increases.

  Therefore, in the case of the prior art, assuming the maximum usage time of the display panel, a method is adopted in which the cathode potential of the display panel is set so that the most deteriorated organic EL element can operate normally within that time. Has been. That is, a method is adopted in which the power supply potential VDD and the cathode potential applied to the display panel are set assuming the maximum value of the voltage Vel.

Hereinafter, although the idea is different from the invention proposed by the inventors, some examples of power consumption reduction techniques will be exemplified.
In this patent document, a technique for suppressing the peak luminance level in order to suppress power consumption is disclosed. However, in this technique, it is essential to change the peak luminance level, and power consumption cannot be reduced if the peak luminance level is kept constant.

Japanese Patent Laid-Open No. 2003-330419 discloses a mechanism for correcting display data so as to obtain appropriate luminance by referring to voltage-current characteristics of a light-emitting element stored in the apparatus based on a detected value of ambient temperature. Has been. However, in the case of this technique, the gradation of display data decreases, and it becomes difficult to maintain high image quality.

Japanese Patent Laid-Open No. 2006-030318 discloses a mechanism for changing the peak luminance level according to the brightness of external light. Specifically, a mechanism is disclosed in which the cathode potential is variably controlled so as to reduce the voltage between the power supply potential Vcc and the cathode potential Vcathode according to the brightness of external light. However, also in this case, the change of the peak luminance level is indispensable, and the power consumption cannot be reduced unless the peak luminance level is lowered.

  Therefore, the inventors propose a mechanism for controlling the power consumed in the display panel to the minimum necessary according to the deterioration state of the self-light-emitting element while keeping the light emission state (peak luminance level) as it is. Specifically, a mechanism for controlling the cathode potential of the display panel to an optimum value is proposed.

  That is, the inventors provide a common cathode potential control device to be applied to a self-luminous display panel that drives and controls the light emission state of each pixel by an active matrix driving method. The cathode potential value that cancels the temporal change in the voltage generated between the cathode electrode and the cathode electrode, and at the same time, determines the cathode potential value that causes the drive transistor of the self-luminous element to operate in the saturation region in accordance with the measured value over time. A cathode potential determination unit and (b) a cathode potential application unit that generates a cathode potential corresponding to the determined cathode potential value and supplies the cathode potential to the common cathode electrode of the self-luminous display panel are mounted.

  In the case of the invention proposed by the inventors, the cathode potential can be variably controlled so as to cancel the change with time of the voltage generated between the anode electrode and the cathode electrode of the self-luminous element during the light emitting operation. For example, the common cathode potential can be controlled to increase while the voltage generated between the anode electrode and the cathode electrode is small, while the common cathode potential is decreased during the period when the voltage is large.

  As a result, the voltage applied to the display panel (the voltage applied between the power supply potential Vcc and the common cathode potential) can be variably controlled according to the change in the voltage generated between the two electrodes of the self-light emitting element. . That is, only the minimum necessary voltage can be applied to the display panel at each time point. Thereby, the power consumed in the display panel other than the light emitting operation can always be controlled to the minimum state.

The case where the invention is applied to the cathode potential control of an active matrix driving type organic EL panel module will be described below.
In addition, the well-known or well-known technique of the said technical field is applied to the part which is not illustrated or described in particular in this specification.
Moreover, the form example demonstrated below is one form example of invention, Comprising: It is not limited to these.

(A) Form example 1
In this embodiment, the voltage between both electrodes of the organic EL element (voltage between the anode electrode and the cathode electrode) Vel is directly measured using a dummy pixel having the same structure as the pixel in the effective display area, and the cathode potential of the organic EL panel is determined. The case of controlling will be described.

(A-1) Arrangement Example of Dummy Pixel FIG. 2 shows an arrangement example of the dummy pixel. The dummy pixels 7 shown in FIG. 2 are arranged on the organic EL panel 3 constituting the organic EL panel module 1. However, the arrangement position of the dummy pixel 7 is outside the effective display area 5. That is, the dummy pixel 7 is arranged in an area that is not related to screen display (usually an area that is not visible to the user).

  FIG. 2A shows an example in which the dummy pixel 7 is arranged on the right outer side of the effective display area 5 constituting the organic EL panel 3, and FIG. 2B shows the dummy pixel 7 on the lower outer side of the effective display area 5. The example which arrange | positions is represented.

  Note that the pixel structure of the dummy pixel 7 is the same as that of the pixels constituting the effective display area 5. Accordingly, the dummy pixel 7 is formed by the same process as the pixel of the effective display area 5.

(A-2) Overall Configuration FIG. 3 shows the main components of the organic EL panel module 11. The organic EL panel module 11 includes an organic EL panel 13, a data line driver 15, a scanning line driver 17, an interpolar voltage measurement unit 19, and a cathode potential control unit 21 as main components.

  In the effective display area of the organic EL panel 13, pixels 23 are arranged in a matrix according to the panel resolution. In the case of this embodiment, the organic EL panel 13 is for color display, and the pixels 23 are arranged according to the arrangement of emission colors. However, when an organic EL element having a structure in which organic light emitting layers of a plurality of colors are stacked constitutes the pixel 23, one pixel corresponds to a plurality of light emission colors.

  FIG. 4 shows a connection relationship between the internal structure of the dummy pixel 25 and other driving circuits. Note that the pixel structure shown in FIG. 4 is the same as the pixel structure of the pixel 23 in the effective display area 5 corresponding to the active matrix driving method. However, in the actual pixel 23, a transistor for controlling a light emission period, a transistor corresponding to a threshold correction function and a mobility correction function of a driving transistor, and the like are arranged.

The dummy pixel 25 shown in FIG. 4 includes a write control transistor T1, a charge holding capacitor C, a current driving transistor T2, and an organic EL element D.
The write control transistor T1 is a thin film transistor that controls writing of the signal voltage Vdata corresponding to the pixel data to the charge retention capacitor C.

  The opening / closing operation of the write control transistor T1 is controlled by a write signal WS supplied from the scan line driver 17 through the scan line WL. Pixel data (signal voltage Vdata) applied through the data line DL is written into the charge storage capacitor C during the period in which the write control transistor T1 is closed.

  The current driving transistor T2 is a thin film transistor that supplies a driving current having a magnitude corresponding to the signal voltage Vdata written in the charge holding capacitor C to the organic EL element D. In the case of FIG. 4, an N-channel field effect transistor is used as the current driving transistor T2.

  The data line driver 15 is a circuit device that applies pixel data (signal voltage Vdata) to a corresponding data line DL. The pixel data here includes pixel data for measurement corresponding to the dummy pixel 25 in addition to pixel data corresponding to the pixel 23 constituting the effective display area. For this reason, the data line driver 15 includes a switch 31 that selectively applies either the pixel data Din corresponding to the pixel 23 or the pixel data Ddmy corresponding to the dummy pixel 25 to the data line DL.

FIG. 5 shows the input / output relationship of the switch 31. Note that the switch 31 is disposed only on the data line DL where the dummy pixel 25 is disposed, and is not disposed on the other data line DL.
Note that the switching timing of the switch 31 is given as a measurement timing signal Stmg from the voltage measurement section 19 between the electrodes. As shown in FIG. 6, the measurement timing signal Stmg is output at a rate of once every 10 frames, for example.

  The scanning line driver 17 is a circuit device that provides a write timing of the signal voltage Vdata. Of course, the scanning line driver 17 also drives and controls the scanning lines WL dedicated to the dummy pixels 25. Note that the scanning line WL that is the supply destination of the write timing is sequentially switched and controlled in units of horizontal scanning periods.

The inter-electrode voltage measurement unit 19 is a processing device that measures the anode potential of the organic EL element D constituting the dummy pixel 25.
FIG. 7 shows an internal configuration example of the interpolar voltage measuring unit 19. The interpolar voltage measuring unit 19 includes a dummy pixel data generating unit 41 and an interpolar voltage calculating unit 43.

  The dummy pixel data generating unit 41 outputs the frame average value of the pixel data Din as dummy pixel data Ddmy except when measuring the voltage between both electrodes, and when measuring the voltage between both electrodes, the dummy pixel data generating unit 41 uses a fixed value for measurement as dummy pixel data Ddmy. Processing device to output. Here, the frame average value of all the pixels constituting the effective display area 5 is calculated as the dummy pixel data Ddmy in order to match the deterioration state of the dummy pixels 25 with the average value of the effective display area 5.

  However, the voltage between both electrodes is measured as a voltage Vel generated between both electrodes of the organic EL element D when the same voltage (fixed value) is applied. Therefore, the dummy pixel data generation unit 41 outputs a fixed value set in advance for measurement when measuring the voltage between both electrodes. The dummy pixel data generation unit 41 outputs the measurement timing as a measurement timing signal Stmg to the data line driver 15 and the interpolar voltage calculation unit 43.

  The voltage calculation part 43 between both electrodes is a signal processing part that measures the voltage Vel appearing between both electrodes of the organic EL element D during the light emission period at the measurement timing. For this reason, the anode potential (analog value) Vs and the cathode potential value Dcathode of the organic EL element D are given to the voltage calculation part 43 between both electrodes.

  FIG. 8 shows an internal configuration example of the interpolar voltage calculation unit 43. In the case of this embodiment, the interpolar voltage calculation unit 43 includes a voltage follower circuit 51 for measuring the anode potential Vs, an analog-digital conversion circuit (A / D conversion circuit) 53, and an interpolar voltage calculation unit 55.

  Here, the reason why the anode potential Vs is measured by using the voltage follower circuit 51 is that the magnitude of the drive current supplied to the organic EL element D is very small on the order of nanometers. That is, it is very difficult to directly measure the change in the voltage between both electrodes Vel from the drive current.

The anode potential Vs detected through the voltage follower circuit 51 is an analog value. Therefore, the analog / digital conversion circuit 53 converts the digital value.
The bipolar voltage calculator 55 calculates the potential difference between the anode potential Vs generated at the anode electrode of the organic EL element D and the common cathode potential Vcathode (p) applied to the cathode electrode. These arithmetic processes are executed by digital processing.

By this calculation process, a measured value Dvel generated between both electrodes of the organic EL element D is calculated. The reason why such calculation processing is performed is that the dummy pixel 25 adopts the same circuit configuration as that of the pixel 23 in the effective display area 5 in this embodiment. That is, the common cathode potential Vcathode (p) of the organic EL element D is variably controlled.
The bipolar voltage calculator 43 supplies the calculated measurement value Dvel to the cathode potential controller 21.

  The cathode potential control unit 21 is configured to cancel the amount of change in the voltage Vel generated between the anode electrode and the cathode electrode of the organic EL element D based on the measurement value Dvel measured by the voltage measurement unit 19 between the electrodes. This is a circuit device that determines a value and applies a cathode potential corresponding to the potential value to the common cathode electrode of the organic EL panel 13.

FIG. 9 shows an internal configuration example of the cathode potential control unit 19. The cathode potential control unit 19 includes a cathode potential determination unit 61 and a cathode potential application unit 63.
The cathode potential determination unit 61 calculates a difference value ΔV between the initial value DVel (ini) of the interelectrode voltage Vel of the organic EL element D and the measured value Dvel, and uses the difference value ΔV as an initial value of the cathode potential value Dcathode. This is a processing device that executes a process of subtracting from Dcathode (ini) to calculate a control cathode potential value Dcathode.

The cathode potential control unit 21 has two initial values Dvel (ini) necessary for these arithmetic processes.
And Dcathode (ini) are stored in a nonvolatile storage medium. These initial values are individually set for each organic EL panel module 11. For this reason, a rewritable storage medium is used. Further, for these initial values, for example, values measured at the time of manufacturing inspection for each organic EL panel module 11 are used.

  FIG. 10 shows the relationship between the voltage Vel generated between the two electrodes of the organic EL element D during the light emitting operation and the usage time. As shown in FIG. 10, the interpolar voltage Vel gradually increases as the organic EL element D deteriorates. In FIG. 11, the relationship between the usage time measured about the certain organic EL element D and the voltage Vel between both electrodes is shown. In the case of FIG. 11, the initial value Dvel (ini) is 8 [V].

  As described above, the progress rate of deterioration of the organic EL element D varies depending on the element material, the content of the displayed image (bright or dark), the temperature of the display panel, and the like. Therefore, it is impossible to estimate the current deterioration state and the amount of change in the interpolar voltage Vel due to deterioration using only the usage time.

  Therefore, the cathode potential determination unit 61 calculates a difference value ΔV between the current measured value Dvel and the initial value Dvel (ini), and obtains a change amount with respect to the initial value Dvel (ini). FIG. 12 shows a specific example. In the case of FIG. 12, the measured value Dvel is 8.02 [V]. Accordingly, the difference value ΔV at the time of measurement is 0.02 [V].

The cathode potential determination unit 61 uses the difference value ΔV as the cathode potential value Dcathode.
The control cathode potential value Dcathode is calculated by subtracting from the initial value Dcathode (ini). FIG. 13 shows an approximate correspondence between the cathode potential value Dcathode calculated for control and the usage time. FIG. 14 shows a specific example. In the case of FIG. 14, the initial value of the cathode potential value Dcathode is set to 3 [V].

  As shown in FIG. 14, it can be seen that the cathode potential value decreases by the amount of change (difference value ΔV) generated in the voltage Vel between both electrodes of the organic EL element D. Thereby, the potential appearing on the anode electrode side of the organic EL element D can be controlled to a substantially constant value.

The cathode potential application unit 63 is a circuit device that generates a common cathode potential Vcathode (p) corresponding to the cathode potential value Dcathode determined according to the measured value Dvel and applies it to the common cathode electrode of the organic EL panel 13.
FIG. 15 shows an internal configuration example of the cathode potential application unit 63.

  The cathode potential application unit 63 shown in FIG. 15 includes a digital potentiometer 71 and a voltage follower circuit (an operational amplifier OP1, resistors R1 and R3, and an N-channel field effect transistor T11) 73.

The digital potentiometer 71 is composed of a semi-fixed resistor that generates a voltage in 256 steps (8 bits), for example. A reference cathode potential Vcathode (i) as a reference potential is applied to the source electrode side of the field effect transistor T11.
With this circuit configuration, the potential of the wiring connected to the common cathode electrode of the organic EL panel 13 can be controlled to the same potential as the common cathode potential Vcathode (p) applied from the digital potentiometer 71.

(A-3) Consideration of light emission state and power consumption of organic EL panel FIG. 16 shows the relationship between the power consumption of the organic EL panel 13 and the power consumption of the cathode potential application unit 63 controlled by the cathode potential control unit 21 described above. Will be explained.

  As shown in FIG. 16, the voltage applied between the power supply potential VDD and the reference cathode potential Vcathode (i) is fixed. On the other hand, the cathode potential control unit 21 variably controls the common cathode potential Vcathode (p) according to the measured value Dvel accompanying the deterioration of the organic EL element D.

As a result, the ratio of the voltage applied to the organic EL panel 13 (= VDD−Vcathode (p)) and the voltage applied to the cathode potential application unit 63 (= Vcathode (p) −Vcathode (i)) is organic EL. It changes reflecting the deterioration state of the element D.
However, the voltage applied between the anode electrode of the organic EL element D and the power supply potential VDD is maintained substantially constant by variable control of the common cathode potential.

Therefore, the drive current Ids supplied from the current drive transistor T2 is not affected by the deterioration state of the organic EL element D, and the drive current Ids having the same current value is always supplied as long as the pixel data is the same.
The ratio of the power consumed in the organic EL panel 13 and the power consumed by the cathode potential application unit 63 varies depending on the ratio of the voltage applied to each section.

FIG. 17 shows a change in the power consumption distribution ratio as the organic EL element D deteriorates.
In a period in which the deterioration of the organic EL element D is small (period in which the usage time is short), the common cathode potential Vcathode (p) is controlled to an initial value (a value close to the reference cathode potential Vcathode (i). 11 is distributed to the cathode potential application unit 63. Thus, power consumed in the organic EL panel can be minimized.

  As a result, the heat generation amount of the organic EL panel 13 is also suppressed to the minimum necessary. In general, the high driving temperature of the organic EL panel 13 acts in the direction of shortening the lifetime of the organic EL element D. For this reason, reducing the heat generation amount (power consumption) of the organic EL panel 13 is expected to have an effect of extending the light emission lifetime.

  However, since the voltage between the power supply potential VDD and the reference cathode potential Vcathode (i) is fixed, if the power consumed by the organic EL panel 13 decreases, the power consumed by the cathode potential application unit 63 increases accordingly. It will be. In particular, the power consumed by the field effect transistor T11 increases.

  However, the cathode potential application unit 63 is located outside the organic EL panel 13. For this reason, unlike the case where the organic EL panel 13 itself generates heat, the influence of increasing the driving temperature of the organic EL panel 13 is small.

  Further, unlike the heat generation area of the organic EL panel 13, the heat generation area of the cathode potential application unit 63 can be very small. For this reason, heat dissipation design becomes easy. That is, it is possible to efficiently release the heat generated in the cathode potential application unit 63. For this reason, the influence which raises the drive temperature of the organic electroluminescent panel 13 can be small. That is, the temperature dependence characteristic of the organic EL panel 13 can be reduced as compared with the conventional method. This effect becomes more prominent as the area of the effective display area is larger.

  Further, in the control method described here, the control of the common cathode potential Vcathode (p) has no influence on the driving operation itself of the current driving transistor T11 (because the current driving transistor T11 operates in the saturation region). The peak luminance level is not lowered. That is, display quality is not impaired.

Note that the power consumption of the organic EL panel 13 is controlled to increase as the deterioration of the organic EL element D progresses. However, the amount of increase is the minimum increase required with the increase of the voltage between both electrodes Vel. For this reason, it is possible to minimize the power consumption exceeding the power necessary for the light emitting operation. As a result, it is possible to prevent an unnecessary temperature rise and achieve a long life.
As described above, the control method according to the embodiment can realize a remarkable effect that cannot be solved by the conventional technique.

(B) Embodiment 2
In this embodiment, the voltage between both electrodes of the organic EL element (the voltage between the anode electrode and the cathode electrode) Vel is measured using the pixels in the effective display area (pixels for both measurement), and the cathode potential of the organic EL panel is controlled. The case will be described.

(B-1) Arrangement Example of Measurement / Combination Pixel FIG. 18 shows an arrangement example of pixels (measurement / use pixels) used for both normal screen display and measurement. 18 is disposed on the organic EL panel 83 that constitutes the organic EL panel module 81. In this case, the measurement / use pixel 87 is arranged in the effective display area 85.

  FIG. 18A shows an example in which the measurement-use pixel 87 is arranged in the lower right corner of the effective display area 85 constituting the organic EL panel 83, and FIG. The example which arrange | positions the pixel 87 is represented.

  The number and arrangement position of the measurement / use pixels 87 are arbitrary. However, from the viewpoint of the influence on the display quality and the panel design, it is desirable to arrange it in any of the outer peripheral parts of the effective display area 85.

  The pixel structure of the measurement / use pixel 87 is the same as the other pixel structures of the effective display area 85 except that a lead-out wiring for measuring the anode potential of the organic EL element D is additionally formed. Therefore, the effective display area 85 is integrally formed by the same process.

(B-2) Overall Configuration FIG. 19 shows the main components of the organic EL panel module 81. However, in the case of FIG. 19, only one measurement / use pixel 87 is arranged at the lower right corner of the effective display area.
In the case of the organic EL panel module 81 shown in FIG. 19, the basic circuit configuration is the same as that of the first embodiment.

That is, the organic EL panel module 81 includes the organic EL panel 83, the data line driver 91, the scanning line driver 93, the interpolar voltage measurement unit 95, and the cathode potential control unit 97 as main components.
However, a normal image needs to be displayed on the measurement / use pixel 87 except during temperature measurement.

Therefore, in the case of this embodiment, a process for calculating the frame average value of the pixel data and a circuit configuration for supplying the calculation result to the data line driver 91 become unnecessary.
Incidentally, the data line driver 91, the scanning line driver 93, and the cathode potential control unit 97 use basically the same circuit configuration as in the first embodiment.

  FIG. 20 shows an internal configuration example of the interpolar voltage calculation unit 95 having a configuration unique to this embodiment. 20, parts corresponding to those in FIG. 7 are given the same reference numerals. The interpolar voltage calculation unit 95 includes a measurement pixel data supply unit 101 and an interpolar voltage calculation unit 43.

  The measurement pixel data supply unit 101 is a processing device that outputs a fixed value for measurement as measurement pixel data Ddtc when measuring the voltage Vel between both electrodes. Incidentally, during the period other than the time of measurement, the measurement / use pixel 87 is driven and controlled by the display content at the corresponding position.

  Except for the position where still images such as time display are mainly displayed, in the region where moving images are displayed, the heat generation state and the characteristic deterioration of the organic EL element D do not deviate greatly from the average level of all pixels. Accordingly, by measuring the interpolar voltage Vel at the measurement / use pixel 87 regularly or irregularly, the interpolar voltage Vel reflecting the deterioration state of the entire panel can be measured.

(B-3) Effect The same effect as that of Embodiment 1 can be realized even in the case of the configuration using the measurement and use pixels as in this embodiment.

(C) Embodiment 3
In the two embodiments described above, the case where the voltage Vel between the electrodes EL of the organic EL element D is directly measured and the cathode potential Vcathode (p) is controlled according to the measurement result has been described.
Here, a description will be given of a case where the cathode potential Vcathode (p) is controlled by measuring the luminance change accompanying the deterioration of the organic EL element D and indirectly obtaining the voltage Vel between the electrodes of the organic EL element D through the measurement result. To do.

(C-1) Arrangement Example of Dummy Pixel and Light Receiving Sensor FIG. 21 shows an arrangement example of the dummy pixel and the light receiving sensor. The dummy pixels 117 are arranged outside the effective display area 115 in the organic EL panel 113 constituting the organic EL panel module 111.

In FIG. 21, although arrange | positioned in the upper right corner of the organic electroluminescent panel 113, the arrangement position is arbitrary.
In the case of this embodiment, the light receiving sensor 119 for measuring the display luminance of the dummy pixel 117 is arranged so as to cover the entire surface of the dummy pixel 117.

(C-2) Overall Configuration FIG. 22 shows the main components of the organic EL panel module 111. The basic circuit configuration of FIG. 22 is the same as that of FIG.

  The organic EL panel module 111 shown in FIG. 22 includes an organic EL panel 113, a data line driver 121, a scanning line driver 123, a light receiving sensor 119, a dummy pixel data generation unit 125, and a cathode potential control unit 127 as main components.

  Here, the data line driver 121 and the scanning line driver 123 adopt the same configuration as the data line driver 15 and the scanning line driver 17 of the first embodiment. That is, in the data line driver 121, the switch 31 is arranged only for the data line DL where the dummy pixel 117 is arranged. Further, the scanning line driver 123 employs a configuration for driving and controlling the scanning lines WL of the dummy pixels 117.

  The dummy pixel data generator 125 outputs the frame average value of the pixel data Din as dummy pixel data Ddmy except when measuring the emission luminance, and outputs a measurement fixed value as dummy pixel data Ddmy when measuring the emission luminance. It is a processing device.

  Here, the frame average value of all the pixels constituting the effective display area 115 is calculated as the dummy pixel data Ddmy in order to make the deterioration state of the dummy pixel 117 coincide with the average value of the effective display area 115.

On the other hand, when measuring the emission luminance, a fixed value set in advance for measurement is used as the dummy pixel data Ddmy.
Is output. The dummy pixel data generation unit 125 outputs the measurement timing to the cathode potential control unit 127 as the measurement timing signal Stmg.

  The cathode potential control unit 127 obtains the voltage Ver between the electrodes corresponding to the deterioration state of the organic EL element D from the light emission luminance value of the dummy pixel 117 received by the light receiving sensor 119, and determines the cathode potential based on the voltage Vel between the electrodes. In this circuit device, the cathode potential corresponding to the potential value is applied to the common cathode electrode of the organic EL panel 113.

FIG. 23 shows a connection relationship among the light receiving sensor 119, the cathode potential control unit 127, and the common cathode electrode.
FIG. 24 illustrates an internal configuration example of the cathode potential control unit 127. The cathode potential control unit 127 includes a cathode potential determination unit 131 and a cathode potential application unit 133.

The cathode potential determination unit 131 is a processing device that obtains the current value of the voltage value Dvel between both electrodes of the organic EL element D from the measured light emission luminance value and calculates an appropriate cathode potential value Dcathode.
FIG. 25 shows an internal configuration example of the cathode potential determination unit 131. The cathode potential determining unit 131 includes a luminance value measuring unit 141 and a voltage output unit 143 between both electrodes.

  The luminance value measuring unit 141 is a processing device that obtains the current voltage VD between both electrodes based on the ratio [%] of the luminance value input at the measurement timing to the initial value. FIG. 26 shows a decrease characteristic of light emission luminance when pixel data for measurement (for example, maximum gradation value) is input. The luminance value measuring unit 141 stores a relationship between each light emission luminance and the voltage between both electrodes Vel when the light emission luminance at the start of use is 100% in order to obtain the voltage value Dvel between both electrodes corresponding to the current deterioration state. Is stored.

  FIG. 27 shows an example of the table memory. In this example, the bipolar voltage value Dvel corresponding to the light emission luminance measured at the time of product shipment is 8 [V]. In this case, the table memory stores the relationship between each light emission luminance and the interpolar voltage value Dvel when the initial value is 8 [V].

As shown in FIG. 28, the luminance value measuring unit 141 obtains a difference value ΔV between the current value and the initial value of the interpolar voltage value Dvel specified by using the table memory, and calculates the difference value ΔV. Cathode potential value Dcathode
The control cathode potential value Dcathode is calculated by subtracting from the initial value Dcathode (ini). The initial value Dcathode (ini) of the cathode potential value Dcathode is also stored in the luminance value measuring unit 141.

  The cathode potential application unit 143 is a circuit device that generates a common cathode potential Vcathode (p) corresponding to the current value of the cathode potential value Dcathode and applies it to the common cathode electrode of the organic EL panel 13, and the internal configuration thereof is described above. This is the same as other embodiments.

(C-3) Effect The same effect as that of Embodiment 1 can also be realized when measuring the voltage Vel between the electrodes indirectly using the light emission luminance as in this embodiment.

(D) Other Embodiments (D-1) Other Measurement Methods In the case of the above-described embodiment, the case where one dummy pixel or one measurement / use pixel is used has been described.
However, a plurality of pixels may be used, and the cathode potential may be controlled using the average value of the measured values.

(D-2) Product example (a) Drive IC
In the above description, the organic EL panel module in which the pixel array unit (organic EL panel) and the drive circuit (data line driver, scanning line driver, cathode potential control unit, etc.) are formed on one substrate has been described.

  However, the pixel array section and the drive circuit section can be manufactured separately and distributed as independent products. For example, the drive circuits may be manufactured as independent drive ICs (integrated circuits) and distributed independently from the pixel array unit.

(B) Display Module The organic EL panel module according to each of the above-described embodiments can be distributed in the form of a panel module 151 having an external configuration shown in FIG.
The panel module 151 has a structure in which a facing portion 153 is bonded to the surface of the support substrate 155.

The facing portion 153 is made of glass or other transparent member as a base material, and a color filter, a protective film, a light shielding film, and the like are arranged on the surface thereof.
Note that the panel module 151 may be provided with an FPC (flexible printed circuit) 157 and the like for inputting and outputting signals and the like to the support substrate 155 from the outside.

(C) Electronic device The organic EL panel module in the embodiment described above is also distributed in a product form mounted on an electronic device.
FIG. 30 illustrates a conceptual configuration example of the electronic device 161. The electronic device 161 includes the organic EL panel module 163 and the system control unit 165 described above. The processing content executed by the system control unit 165 differs depending on the product form of the electronic device 161.

Note that the electronic device 161 is not limited to a device in a specific field as long as it has a function of displaying an image or video generated in the device or input from the outside.
As this type of electronic device 161, for example, a television receiver is assumed. FIG. 31 shows an example of the appearance of the television receiver 171.

  A display screen 177 including a front panel 173, a filter glass 175, and the like is disposed on the front surface of the television receiver 171. The display screen 177 corresponds to the organic EL panel module described in the embodiment.

  Further, for example, a digital camera is assumed as this type of electronic device 161. FIG. 32 shows an appearance example of the digital camera 181. FIG. 32A shows an example of the appearance on the front side (subject side), and FIG. 32B shows an example of the appearance on the back side (photographer side).

  The digital camera 181 includes a protective cover 183, an imaging lens unit 185, a display screen 187, a control switch 189, and a shutter button 191. Among these, the display screen 187 corresponds to the organic EL panel module described in the embodiment.

For example, a video camera is assumed as this type of electronic device 161. FIG. 33 shows an example of the appearance of the video camera 201.
The video camera 201 includes an imaging lens 205 that images a subject in front of the main body 203, a shooting start / stop switch 207, and a display screen 209. Among these, the portion of the display screen 209 corresponds to the organic EL panel module described in the embodiment.

  In addition, as this type of electronic device 161, for example, a portable terminal device is assumed. FIG. 34 shows an example of the appearance of a mobile phone 211 as a mobile terminal device. A cellular phone 211 illustrated in FIG. 34 is a foldable type, and FIG. 34A illustrates an appearance example in a state where the housing is opened, and FIG. 34B illustrates an appearance example in a state where the housing is folded.

  The cellular phone 211 includes an upper housing 213, a lower housing 215, a connecting portion (in this example, a hinge portion) 217, a display screen 219, an auxiliary display screen 221, a picture light 223, and an imaging lens 225. Among these, the display screen 219 and the auxiliary display screen 221 correspond to the organic EL panel module described in the embodiment.

In addition, for example, a computer is assumed as this type of electronic device 161. FIG. 35 shows an example of the appearance of a notebook computer 231.
The notebook computer 231 includes a lower casing 233, an upper casing 235, a keyboard 237, and a display screen 239. Among these, the display screen 239 corresponds to the organic EL panel module described in the embodiment.

  In addition to these, the electronic apparatus 161 may be an audio playback device, a game machine, an electronic book, an electronic dictionary, or the like.

(D-3) Other Pixel Circuit Examples In the above-described embodiment, the case where the current driving transistor T2 is an N-channel field effect transistor has been described.
However, the present invention can also be applied to the case where the current driving transistor T2 is configured by a P-channel field effect transistor.

FIG. 36 shows an example of a pixel circuit when the current driving transistor T2 is a P-channel field effect transistor. In FIG. 36, the same reference numerals are given to the portions corresponding to FIG.
In the case of this pixel circuit, the charge holding capacitor C is connected between the power supply potential VDD and the gate electrode of the current driving transistor T2 so as to hold a voltage Vdata corresponding to pixel data.

(D-4) Other Display Device Examples In the description of the embodiments, the case where the common cathode potential of the organic EL panel module is controlled has been described.
However, the cathode potential control function can also be applied to other self-luminous display devices. For example, the present invention can be applied to an inorganic EL display device, a display device in which LEDs are arranged, and other display devices in which light emitting elements having a diode structure are arranged on a screen.

(D-5) Control Device Configuration In the above description, the case where the cathode potential control function is realized in hardware has been described.
However, a part of the cathode potential control function may be realized by software processing.

(D-6) Others Various modifications can be considered for the above-described embodiments within the scope of the gist of the invention. Various modifications and applications created or combined based on the description of the present specification are also conceivable.

It is a figure explaining the change of the voltage between both electrodes accompanying deterioration of an organic EL element. It is a figure which shows the example of arrangement | positioning of a dummy pixel. It is a figure which shows the circuit structure of an organic electroluminescent panel module. It is a figure which shows the connection relation of a pixel circuit and a peripheral circuit. It is a figure explaining a part of circuit structure mounted in a data line driver. It is a figure explaining the supply timing of a measurement timing signal. It is a figure which shows the internal structural example of the voltage measurement part between both electrodes. It is a figure which shows the internal structural example of the voltage calculation part between both electrodes. It is a figure which shows the internal structural example of a cathode potential control part. It is a figure which shows the relationship between the voltage between both electrodes, and use time. It is a figure which shows the relationship between the voltage between both electrodes, and use time. It is a figure explaining the calculation method of the variation | change_quantity of the voltage between both electrodes. It is a figure which shows the relationship between the optimal value of a cathode potential, and use time. It is a figure which shows the correspondence of the difference value of the voltage between both electrodes, and cathode potential. It is a figure which shows the internal structural example of a cathode potential application part. It is a figure which shows the correspondence of the electric power consumed by a cathode potential application part, and the electric power consumed by an organic electroluminescent panel. It is a figure which shows the relationship between the optimal value of a cathode potential, and use time. It is a figure which shows the example of arrangement | positioning of the pixel for measurement combined use. It is a figure which shows the circuit structure of an organic electroluminescent panel module. It is a figure which shows the internal structural example of the voltage calculation part between both electrodes. It is a figure which shows the example of arrangement | positioning of a dummy pixel and a light receiving sensor. It is a figure which shows the circuit structure of an organic electroluminescent panel module. It is a figure which shows the connection relation of a dummy pixel and a peripheral circuit. It is a figure which shows the internal structural example of a cathode potential control part. It is a figure which shows the internal structural example of a cathode potential determination part. It is a figure which shows the change of the light emission luminance accompanying deterioration of an organic EL element. It is a figure which shows the correspondence of light emission luminance and the voltage between both electrodes. It is a figure explaining the calculation method of the variation | change_quantity of the voltage between both electrodes. It is a figure which shows the structural example of a display module. It is a figure which shows the function structural example of an electronic device. It is a figure which shows the example of goods of an electronic device. It is a figure which shows the example of goods of an electronic device. It is a figure which shows the example of goods of an electronic device. It is a figure which shows the example of goods of an electronic device. It is a figure which shows the example of goods of an electronic device. It is a figure which shows the other pixel circuit example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Organic EL panel module 3 Organic EL panel 5 Effective display area 7 Dummy pixel 11 Organic EL panel module 19 Bipolar voltage measurement part 21 Cathode potential control part 81 Organic EL panel module 83 Organic EL panel 85 Effective display area 87 Measurement-use pixel 95 Bipolar voltage measurement unit 97 Cathode potential control unit 111 Organic EL panel module 113 Organic EL panel 115 Effective display area 117 Dummy pixel 119 Light receiving sensor 125 Dummy pixel data generation unit 127 Cathode potential control unit

Claims (8)

A cathode potential control device for controlling a common cathode potential applied to a self-luminous display panel that drives and controls the light emission state of each pixel by an active matrix driving method,
The cathode potential value that cancels the change over time in the voltage generated between the anode electrode and the cathode electrode of the self-light emitting element during the light emitting operation, and at the same time, the cathode potential value that causes the drive transistor of the self light emitting element to operate in the saturation region. Cathode potential determination unit that determines according to the measured value of change,
And a cathode potential application unit that generates a cathode potential corresponding to the determined cathode potential value and supplies the cathode potential to the common cathode electrode of the self-luminous display panel. The cathode potential control device according to claim 1,
The cathode potential determining unit
Calculate the difference between the measured value of the voltage generated between the anode electrode and the cathode electrode of the self-luminous element and the corresponding initial value when the specific pixel is driven and controlled with the pixel data for measurement,
A cathode potential control device characterized by subtracting the calculated difference value from a corresponding initial value of a cathode potential value to determine a cathode potential value for control. The cathode potential control device according to claim 2,
The cathode potential control device, wherein the specific pixel is a dummy pixel. The cathode potential control device according to claim 2,
The said specific pixel is a measurement combined pixel which comprises an effective display area. The cathode potential control apparatus characterized by the above-mentioned. The cathode potential control device according to claim 1,
The cathode potential determining unit
Based on the measured luminance value generated when the specific pixel is driven and controlled with the pixel data for measurement, the difference value between the voltage generated between the anode electrode and the cathode electrode of the self-luminous element and the corresponding initial value is calculated. ,
A cathode potential control device characterized by subtracting the calculated difference value from a corresponding initial value of a cathode potential value to determine a cathode potential value for control. A self-luminous display panel that drives and controls the light emission state of each pixel by an active matrix driving method;
The cathode potential value that cancels the change over time in the voltage generated between the anode electrode and the cathode electrode of the self-light emitting element during the light emitting operation, and at the same time, the cathode potential value that causes the drive transistor of the self light emitting element to operate in the saturation region. Cathode potential determination unit that determines according to the measured value of change,
A self-luminous display device comprising: a cathode potential application unit that generates a cathode potential corresponding to the determined cathode potential value and supplies the cathode potential to a common cathode electrode of the self-luminous display panel. A self-luminous display panel that drives and controls the light emission state of each pixel by an active matrix driving method;
The cathode potential value that cancels the change over time in the voltage generated between the anode electrode and the cathode electrode of the self-light emitting element during the light emitting operation, and at the same time, the cathode potential value that causes the drive transistor of the self light emitting element to operate in the saturation region. Cathode potential determination unit that determines according to the measured value of change,
A cathode potential application unit that generates a cathode potential corresponding to the determined cathode potential value and supplies the cathode potential to the common cathode electrode of the self-luminous display panel;
A system controller;
An electronic device comprising: an operation input unit for the system control unit. A cathode potential control method for controlling a common cathode potential applied to a self-luminous display panel that drives and controls the light emission state of each pixel by an active matrix driving method,
The cathode potential value that cancels the change over time in the voltage generated between the anode electrode and the cathode electrode of the self-light emitting element during the light emitting operation, and at the same time, the cathode potential value that causes the drive transistor of the self light emitting element to operate in the saturation region. Processing to determine according to the measured value of change;
A cathode potential control method comprising: generating a cathode potential corresponding to the determined cathode potential value and supplying the cathode potential to the common cathode electrode of the self-luminous display panel.

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