JP4539963B2 - Active drive type light emitting display device and electronic device equipped with the display device - Google Patents

Active drive type light emitting display device and electronic device equipped with the display device Download PDF

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JP4539963B2
JP4539963B2 JP2004172581A JP2004172581A JP4539963B2 JP 4539963 B2 JP4539963 B2 JP 4539963B2 JP 2004172581 A JP2004172581 A JP 2004172581A JP 2004172581 A JP2004172581 A JP 2004172581A JP 4539963 B2 JP4539963 B2 JP 4539963B2
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JP2005352148A (en
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孝義 吉田
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東北パイオニア株式会社
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  The present invention relates to an active drive type light emitting display device including a measurement pixel in addition to a light emission display pixel, and in particular, obtains a forward voltage of a light emitting element by the measurement pixel, thereby efficiently driving the display pixel. The present invention relates to a light emitting display device and an electronic device equipped with the display device.

  The development of a display using a display panel configured by arranging light emitting elements in a matrix is being widely promoted. As a light-emitting element used for such a display panel, an organic EL (electroluminescence) element using an organic material for a light-emitting layer has attracted attention. This is also due to the fact that the use of an organic compound that can be expected to have good light-emitting characteristics for the light-emitting layer of the EL element has led to an increase in efficiency and longevity that can withstand practical use.

  The organic EL element described above can be electrically represented by an equivalent circuit as shown in FIG. In other words, the organic EL element can be replaced with a configuration having a parasitic capacitance component Cp and a diode component E coupled in parallel to the capacitance component, and the organic EL element is considered to be a capacitive light emitting element. When a light emission driving voltage is applied to the organic EL element, first, a charge corresponding to the electric capacity of the element flows into the electrode as a displacement current and is accumulated. Subsequently, when a certain voltage specific to the element (light emission threshold voltage = Vth) is exceeded, current begins to flow from the electrode (the anode side of the diode component E) to the organic layer constituting the light emitting layer, and the intensity is proportional to this current. It can be considered to emit light.

  FIG. 2 shows the static light emission characteristics of such an organic EL element. According to this, as shown in FIG. 2A, the organic EL element emits light with luminance (L) substantially proportional to the drive current (I), and as shown in FIG. 2B, the drive voltage ( When V) is equal to or higher than the light emission threshold voltage (Vth), current (I) suddenly flows to emit light.

  In other words, when the drive voltage is equal to or lower than the light emission threshold voltage (Vth), almost no current flows through the EL element and no light is emitted. Therefore, as shown by a solid line in FIG. 2 (c), the EL element has a luminance characteristic that is larger than the threshold voltage (Vth). The luminance (L) is increased.

  On the other hand, it is known that the organic EL element described above changes the physical properties of the element due to long-term use and the forward voltage (Vf) increases. For this reason, as shown in FIG. 2B, the organic EL element changes in the VI characteristic in the direction indicated by the arrow (characteristic indicated by the broken line) according to the actual usage time, and thus the luminance characteristic also decreases. Will do. In addition, the above-described organic EL element also has a problem that the initial luminance varies due to, for example, variations in vapor deposition at the time of film formation of the element, thereby expressing luminance gradation faithful to the input video signal. It becomes difficult.

  Furthermore, it is also known that the luminance characteristics of the organic EL element change as shown by a broken line in FIG. That is, the EL element has a characteristic that in a light emission possible region larger than the light emission threshold voltage, the light emission luminance (L) increases as the value of the voltage (V) applied thereto increases. The threshold voltage is reduced. Therefore, the EL element is in a state in which light can be emitted with a smaller applied voltage as the temperature becomes higher, and has a luminance temperature dependency such that it is brighter at high temperatures and darker at low temperatures even when the same applied voltage capable of emitting light is applied.

  On the other hand, the above-mentioned organic EL element has a current / luminance characteristic that is stable with respect to a temperature change, whereas a voltage / luminance characteristic is unstable with respect to a temperature change. In general, constant current driving is performed for reasons such as preventing deterioration. In this case, the drive voltage (V0) supplied from the DC-DC converter or the like supplied to the constant current circuit must be set in consideration of the following factors.

  That is, the elements include the forward voltage (Vf) of the EL element, the variation (VB) of the Vf of the EL element, the change over time (VL) of the Vf, the temperature change (VT) of the Vf, the constant. A drop voltage (VD) required for the current circuit to operate at a constant current can be cited. Even when these elements act synergistically, the driving voltage (V0) is shown as each element in order to ensure sufficient constant current characteristics of the constant current circuit. It must be set to a value obtained by adding the maximum values of each voltage.

  However, the drive voltage (V0) supplied to the constant current circuit rarely occurs in the case where a voltage value obtained by adding the maximum values of the voltages as described above is required. A large power loss is caused as a voltage drop in the circuit. Therefore, this causes heat generation and results in stress on the organic EL element and peripheral circuit components.

Therefore, by measuring the forward voltage Vf of the EL element and controlling the value of the drive voltage (V0) applied to the constant current circuit based on this Vf, an attempt to solve the above-mentioned problems is possible. It is disclosed in Patent Document 1.
JP-A-7-36409

  By the way, the configuration disclosed in Patent Document 1 described above is a so-called passive matrix display device in which EL elements are arranged at the intersections of the anode lines and the cathode lines. According to such a passive matrix type display device, the anode driver is provided with a constant current circuit corresponding to each anode line, and therefore, by detecting the voltage value in one anode line, It is possible to easily take out the average value of the forward voltage Vf in each connected EL element.

  However, in an active matrix display device, an active element composed of a TFT (Thin Film Transistor) is added to each of the EL elements arranged in a matrix, and each EL element is driven at a constant current by the TFT. In order to operate, in order to detect the forward voltage Vf of each EL element, it is necessary to draw a wiring for detecting Vf from, for example, the anode terminal of each EL element.

  At this time, for example, when the forward voltage Vf of only one EL element is used to control the drive voltage applied to each pixel, when a problem occurs in the EL element that measures the forward voltage Vf. However, the entire display panel and the module including the module cannot be used practically and must be discarded as defective. In view of this, it is conceivable that the above-described Vf detection wiring is drawn out from a plurality of EL elements and the average value of the forward voltage Vf of each element is measured. It is difficult to realize due to physical problems such as increase.

  The present invention has been made paying attention to the problems in the active matrix drive circuit described above, and makes it possible to take out the forward voltage from a plurality of EL elements reasonably and accurately. It is an object of the present invention to provide an active drive light emitting display device capable of controlling a drive voltage supplied to a light emitting display pixel based on the above.

One preferred embodiment of a light emitting display device according to the present invention made in order to solve the above, as described in claim 1, comprising at least a driving TFT that supplies a drive current to the light emitting element and the light-emitting element An active drive type light emitting display device in which a large number of light emitting display pixels are arranged, the light emitting display device including a power supply circuit for supplying a driving voltage to the light emitting display pixels and at least one for obtaining a forward voltage. one of the measuring element and the plurality of measurement pixels including a driving TFT that supplies a drive current to the elements are arranged, the measuring element is either at least aging characteristics of the light emitting elements constituting the light emitting display pixels to have one of the temperature dependence the same electrical characteristics, each of the anode or cathode side potential of the the element for measuring the light emitting element is different potentials and Is constant, the is the driving TFT derive the forward voltage generated in the measuring device in the state of applying the drive current is configured to supply to the power supply circuit, the power supply circuit on the basis of the forward voltage The present invention is characterized in that the drive voltage level of the light emitting display pixel is controlled .

  Hereinafter, an active drive type light emitting display device according to the present invention will be described based on the embodiments shown in the drawings. Prior to that, the light emitting display device which is the basis of the present invention previously proposed by the present applicant will be described. This will be described with reference to FIG. FIG. 3 shows a partial configuration of a light-emitting display panel and a circuit configuration for driving the light-emitting display panel. The light-emitting display panel denoted by reference numeral 10 emits light in which light-emitting display pixels 10a are arranged in a matrix. A display area 10A and a measurement pixel area 10B in which measurement pixels 10b are arranged in the column direction are formed.

  In FIG. 3, only the configuration of the two light emitting display pixels 10a arranged in a matrix is shown due to space limitations, and also in the measurement pixels 10b arranged in the column direction. Similarly, only the configuration of two pixels is shown.

  In the light emitting display panel 10, data lines m1, m2,... From a data driver described later are arranged in the vertical direction (column direction), and similarly, a control line n1 from a scanning driver described later. , N2,... Are arranged in the horizontal direction (row direction). Further, on the display panel 10, power supply lines p1, p2,... Are arranged in the vertical direction corresponding to the data lines.

  As an example of the light emitting display pixel 10a in the light emitting display region 10A, a pixel configuration by a conductance control system is shown. That is, as the elements constituting the pixel 10a in the upper left of the light emitting display area 10A are labeled, the gate of the control TFT (Tr1) constituted by the N channel is connected to the control line n1, and the source thereof is the data Connected to line m2. Further, the drain of the control TFT (Tr1) is connected to the gate of the drive TFT (Tr2) constituted by the P channel and to one terminal of the charge holding capacitor C1.

  The source of the driving TFT (Tr2) is connected to the other terminal of the capacitor C1 and to the power supply line p2. Further, the anode of the organic EL element E1 as a light emitting element is connected to the drain of the driving TFT, and the cathode of the EL element E1 is connected to the cathode side power supply line Vca. Thus, as described above, a large number of the light emitting display pixels 10a configured as described above are arranged in a matrix in the vertical and horizontal directions in the light emitting display region 10A.

  On the other hand, each measurement pixel 10b in the measurement pixel region 10B is configured in the same manner as the light emission display pixel, and each element in the uppermost measurement pixel has each of the light emission display pixels 10a. The same reference numerals as those of the elements are attached. The gate of the control TFT (Tr1) constituting the measurement pixel 10b is connected to the control line n1, and the source thereof is connected to the data line m1. The source of the driving TFT (Tr2) is connected to the power supply line p1. Further, the measurement pixels 10b described above are arranged in a line along one data line m1 and the power supply line p1 in the measurement pixel region 10B.

  The element indicated by the symbol E1 constituting the above-described measurement pixel 10b is referred to as a measurement element. In the example shown in FIG. 3, an element having the same electrical characteristics as that of the organic EL element E1 constituting the light emitting display pixel 10a is used as the measuring element. That is, the light emitting display EL element and the measurement EL element are formed on the display panel 10 simultaneously by the same manufacturing process. Therefore, since the light emitting operation is accompanied when the measurement EL element is driven, it is desirable to provide a shielding film or the like on the surface of the measurement pixel region 10B as necessary.

  As described above, it is not always necessary to use an organic EL element as a measurement element, and it is possible to consider a method of forming an element that does not emit light in the measurement pixel region 10B. In short, as the above-described measuring element, other elements whose electrical characteristics including time-varying characteristics, temperature dependency, and the like approximate the characteristics of the organic EL element can be used.

  As described above, in the configuration of the display panel 10 shown in FIG. 3, the light emitting display pixels 10a are arranged in a matrix at the intersections of the data lines and the control lines, and the measurement pixel 10b is one data line m1. The control lines used in the measurement pixel 10b are shared with the control lines n1, n2,... Used in the light emitting display pixel 10a. Therefore, the gate voltage of the control TFT of the measurement pixel 10b is common to the gate voltage of the control TFT of the light emitting display pixel 10a. As a result, the gate voltage of the drive TFT of the measurement pixel 10b is This is the same as the gate voltage of the driving TFT of the pixel 10a.

  A constant current is supplied to the power supply line p1 in the measurement pixel 10b through the constant current source 11. A voltage detection terminal 12 is formed in the power supply line p1 between the constant current source 11 and each measurement pixel 10b so that the forward voltage Vf of the measurement element in the measurement pixel 10b can be obtained at the terminal 12. It is configured. That is, the forward voltage Vf of the measuring element is obtained via the driving TFT (Tr2) in the example shown in FIG.

  On the other hand, each light emitting display pixel 10a is supplied with a driving voltage from a power supply circuit 17 constituting a constant voltage source via a power supply line p2,..., And each EL element as a light emitting element is driven by this driving voltage. E1 is selectively driven to light. Each of the data lines m1, m2,... Arranged in the vertical direction is derived from the data driver 13, and the control lines n1, n2,. Has been derived.

  A control bus is connected to the data driver 13 and the scan driver 14 from a controller IC 15, and the data driver 13 and the scan driver 14 are controlled based on an image signal supplied to the controller IC. As a result, each light emitting display pixel 10a in the light emitting display area 10A is selectively turned on, and as a result, an image is reproduced in the light emitting display area 10A.

  That is, when an on-voltage is supplied to the gate of the control TFT (Tr1) in the light emitting display pixel 10a from the scan driver 14, for example, via the control line n1, the control TFT (Tr1) is supplied to the source. A current corresponding to the data voltage from the line m2 is passed from the source to the drain. Therefore, the capacitor C1 is charged while the gate of the control TFT (Tr1) is on-voltage, and the voltage is supplied to the gate of the drive TFT (Tr2). Therefore, the driving TFT (Tr2) passes a current based on the gate voltage and the source voltage to the EL element E1 to drive the EL element to emit light. That is, the driving TFT (Tr2) drives the EL element E1 to emit light by driving the EL element E1 with a constant current.

  When the gate of the control TFT (Tr1) is turned off, the control TFT (Tr1) becomes a so-called cut-off, and the drain of the control TFT (Tr1) is opened, but the drive TFT (Tr2) is The gate voltage is held by the electric charge accumulated in the capacitor C1, the driving current is maintained until the next scanning, and the light emission of the EL element E1 is also maintained.

  In synchronization with the light emission driving operation described above, each measurement pixel 10b is also subjected to the same scanning, and the forward voltage generated at the anode of the measurement EL element E1 at this time is the driving TFT ( The voltage detection terminal 12 is provided via Tr2). The forward voltage Vf of the measuring element provided at the voltage detection terminal 12 is supplied to the sampling and holding circuit 16, and the hold output by the sampling and holding circuit 16 is supplied to the voltage control unit 18 in the power supply circuit 17. Has been.

  Here, the voltage controller 18 in the power supply circuit 17 receives the hold voltage from the sampling and hold circuit 16 and controls the value of the constant voltage applied to the power supply lines p2,. That is, this controls the level of the drive voltage applied to each light emitting display pixel 10a corresponding to the forward voltage value Vf provided to the voltage detection terminal 12.

  In this case, when the forward voltage value Vf provided to the terminal 12 is large, control is performed so as to increase the level of the drive voltage applied to each light emitting display pixel 10a, and conversely, the forward voltage value provided to the terminal 12 is controlled. When Vf is small, control is performed so as to reduce the level of the drive voltage applied to each light emitting display pixel 10a.

  As a result, the driving voltage value applied to the light emitting display pixel 10a is controlled, and the driving TFT (Tr2) in the light emitting display pixel 10a has secured a drop voltage (VD) sufficient to maintain constant current characteristics. Thus, the EL element E1 can be driven. In this case, the drive voltage value applied to the light emitting display pixel 10a is controlled including the variation factors such as the time-dependent change (VL) and the temperature change (VT) of the forward voltage Vf of the EL element. Therefore, it is possible to effectively suppress the power loss generated in the driving TFT (Tr2) in the light emitting display pixel 10a.

  Note that the constant current source 11 in the configuration shown in FIG. 3 is preferably configured to output a current that causes one measurement pixel 10b to emit light with a predetermined luminance. Thus, a constant current is sequentially applied to each measurement pixel 10b in synchronization with the operation of driving the light emitting display pixel 10a to light. That is, the constant current source 11 is controlled so that no current is supplied to the plurality of measurement pixels 10b at the same time.

  In the sampling and holding circuit 16, the measurement pixel 10b has a time constant longer than the period in which the constant current is sequentially supplied, so that each measurement pixel 10b averaged in an analog manner is used. A forward voltage Vf can be obtained at the voltage detection terminal 12. Thereby, the control of the drive voltage value applied to the light emitting display pixel 10a can be executed based on the averaged voltage Vf, and the influence due to the variation in Vf can be avoided.

  In the configuration shown in FIG. 3, a luminance control signal is supplied to the controller IC 15 described above, and the light emission luminance of each light emitting display pixel 10a is changed by receiving this luminance control signal. It has been made possible. That is, when the luminance control signal is supplied to the controller IC 15, the control signal is sent from the controller IC 15 to the data driver 13, and the data driver 13 controls the light emitting display pixels 10a based on the luminance control signal. The source voltage applied to the TFT for use (Tr1) is controlled.

  As a result, the gate voltage of the driving TFT (Tr2) in each light emitting display pixel 10a is controlled, and the current value supplied to the EL element E1 in the light emitting display pixel 10a is varied. Accordingly, as a result, the light emission luminance of the EL element E1 in the light emitting display pixel 10a is controlled. In this case, the drive current supplied to the measurement element constituting the measurement pixel 10b is also controlled based on the luminance control signal.

  Therefore, according to the configuration shown in FIG. 3, the current value of the constant current source 11 that supplies current to the measurement pixel 10b is also varied by the luminance control signal. As described above, since the current flowing through the measurement element of the measurement pixel 10b is also varied in accordance with the light emission luminance (= drive current) of the light emission element (EL element E1), the EL element E1 and the measurement in the light emission display pixel 10a are changed. The measuring elements in the pixel 10b are driven under the same conditions.

  Therefore, the forward voltage Vf of the EL element E1 in the light emitting display pixel 10a can be grasped more accurately by the measurement element in the measurement pixel 10b. Therefore, it is possible to realize the above-described action of suppressing the power loss generated in the driving TFT (Tr2) in the light emitting display pixel 10a with higher accuracy.

  Incidentally, in the configuration shown in FIG. 3, the driving TFT (Tr2) constituting the light emitting display pixel 10a is operated in a saturation region at a predetermined gate voltage. That is, the driving TFT constituting the light emitting display pixel 10a holds a certain drain-source voltage Vds, and is driven by constant current. On the other hand, the driving TFT (Tr2) in the measurement pixel 10b described above needs to be operated in a linear region, that is, as a switch element. This is because when the on-resistance of the driving TFT in the measurement pixel 10b is large, a voltage drop occurs between the source and drain of this TFT, and an accurate forward voltage Vf in the measurement element is obtained at the voltage detection terminal 12. It is because it becomes impossible.

  As described above, when the driving TFT in the light emitting display pixel 10a is operated in the saturation region and the driving TFT in the measurement pixel 10b is operated in the linear region, the potential setting of each part in the light emitting display pixel and the measurement pixel is performed. In other words, there is a problem that the range in which both can operate under a preferable condition is narrowed.

FIG. 4 shows a pixel configuration in the measurement pixel 10b including the constant current source 11 shown in FIG. In the configuration shown in FIG. 4, in order to operate the driving TFT (Tr2) in the measurement pixel 10b in a linear region, that is, as a switching element, the gate voltage when the P-channel driving TFT (Tr2) is turned on is set to When Vlow is set, it is necessary to satisfy the relationship shown in the following formula 1, and it is more desirable to satisfy the condition shown in formula 2.
Vca + Vf ≥ Vlow (Equation 1)
[0 ≧ Vgs + Vlow− (Vca + Vf)] (Formula 2)

In the circuit configuration shown in FIG. 4, for example, when Vgs = 1V, Vlow = 0V, Vca = −8V, and Vf = 5V, the drain / source of the driving TFT (Tr2) in the measurement pixel 10b. The inter-voltage Vds can be expressed as the following Expression 3.
Vds = Vgs + Vlow− (Vca + Vf) = 1 + 0 − (− 8 + 5) = 4 (Equation 3)

  According to the potential setting described above, Vds = 4 (V) as shown in Equation 3, and the forward voltage Vf generated at the anode of the measuring element is accurately detected at the voltage detection terminal 12 via the driving TFT (Tr2). It is impossible to detect. On the other hand, the potential setting described above is a preferable condition when the driving TFT in the light emitting display pixel 10a shown in FIG. 3 is operated in the saturation region.

  Therefore, even in the above-described potential setting condition in which the driving TFT in the light emitting display pixel 10a is operated in the saturation region, a circuit in which Vds = 0 or its value can be negative (−) in the above equation 3. It is desired that the configuration, that is, the configuration in which the driving TFT in the measurement pixel can reliably operate in the linear region.

  FIG. 5 shows one means for realizing this, which corresponds to the invention described in claim 1. In the configuration shown in FIG. 5, parts having the same functions as those shown in FIG. 3 already described are denoted by the same reference numerals, and therefore detailed description thereof is omitted. In FIG. 5, the difference from the configuration shown in FIG. 3 described above is that a plurality of series-connected measuring electrodes are connected between the driving TFT (Tr2) and the cathode side power supply line Vca in each measuring pixel 10b. The element E1 is interposed.

  Each measuring element E1 is preferably an organic EL element, and in the embodiment shown in FIG. 5, two EL elements are connected in series. Here, it is desirable that the organic EL element constituting each measuring element E1 and each light emitting display EL element use elements having the same electrical characteristics. That is, the light emitting display EL element and the measurement EL element are formed and formed on the display panel 10 by the same manufacturing process at the same time, so that substantially the same electrical characteristic characteristics as described above can be obtained. .

In the configuration shown in FIG. 5, when the potential setting already exemplified is obtained, the value of Vds shown in the above-described Expression 3 can be obtained as follows.
Vds = Vgs + Vlow− (Vca + Vf) = 1 + 0 − (− 8 + 5 × 2) = − 1

  As apparent from the calculation of Vds described above, according to the configuration shown in FIG. 5, the driving TFT in the measurement pixel can be obtained even under a potential setting condition in which the driving TFT in the light emitting display pixel 10 a is preferably operated in the saturation region. Can be reliably operated in the linear region. Therefore, according to the configuration shown in FIG. 5, it is possible to obtain the forward voltage from the two measurement EL elements from the voltage detection terminal 12. The forward voltage (2 · Vf) obtained by the two measurement EL elements obtained from the terminal 12 is supplied to the sampling and holding circuit 16, and the hold output from the sampling and holding circuit 16 is supplied to the voltage control unit 18 in the power supply circuit 17. Supplied.

  As a result, the voltage control unit 18 controls the value of the constant voltage applied to each light emitting display pixel 10a. At this time, the voltage control unit 18 connects the forward voltage (= hold output) in series. It is desirable to divide by the plurality of measurement elements (number of elements = 2 in the embodiment shown in FIG. 5) and control the constant voltage applied to the light emitting display pixel based on the divided value. Thereby, it is possible to prevent the output voltage from the voltage control unit 18 from being excessively corrected. As the means for dividing, in a very typical example, a voltage dividing means using a resistor or the like can be used.

  According to the embodiment shown in FIG. 5 described above, the operational effects of the configuration shown in FIG. 3 can be enjoyed as they are. Furthermore, since the driving TFT in the measurement pixel can be operated in the linear region while the driving TFT in the light emitting display pixel is operated in the saturation region, the voltage detection terminal 12 can be operated more accurately by the measuring element. A forward voltage can be obtained. Thereby, it is possible to further improve the accuracy of correction of the constant voltage output from the voltage control unit.

  In the embodiment shown in FIG. 5, in the measurement pixel 10b, two measurement elements are connected in series, but the number of measurement elements is three or more as required. In some cases.

FIG. 6 shows another means by which the driving TFT in the light emitting display pixel can be operated in the saturation region and the driving TFT in the measurement pixel can be reliably operated in the linear region. This corresponds to the invention described in claim 1 . In FIG. 6, parts having the same functions as those shown in FIG. 3 already described are denoted by the same reference numerals, and therefore detailed description thereof is omitted.

  The configuration shown in FIG. 6 differs from the configuration shown in FIG. 3 described above in that the potential on the cathode side of the light emitting element constituting the light emitting display pixel 10a and the cathode side of the measuring element constituting the measurement pixel. This is that the potential is set to a different potential.

  In the configuration shown in FIG. 6, an organic EL element is preferably used as the measuring element E1. The organic EL element constituting each measuring element E1 and each light emitting display EL element are desirably elements having the same electrical characteristics. That is, the light emitting display EL element and the measurement EL element are formed and formed on the display panel 10 by the same manufacturing process at the same time, so that substantially the same electrical characteristic characteristics as described above can be obtained. .

In the configuration shown in FIG. 6, in the case where the already-illustrated potential setting for operating the driving TFT in the light emitting display pixel 10a in the saturation region and the cathode side potential Vca1 in the measuring element E1 is set to, for example, -3V. When the value of Vds shown in Equation 3 is obtained, it can be expressed as follows.
Vds = Vgs + Vlow- (Vca + Vf) = 1 + 0-(-3 + 5) =-1

  As is apparent from the calculation of Vds described above, the driving TFT in the measurement pixel is also used in the configuration shown in FIG. 6 under the potential setting conditions in which the driving TFT in the light emitting display pixel 10a is preferably operated in the saturation region. Can be reliably operated in the linear region. The forward voltage Vf from the measurement EL element is supplied to the sampling and holding circuit 16, and the voltage controller 18 controls the value of the constant voltage applied to each light emitting display pixel 10a by the hold output from the sampling and holding circuit 16. Acts like

  In the embodiment shown in FIG. 6, one measuring element E1 is used in the measuring pixel 10b, but this is used by connecting two or more measuring elements in series as required. It is possible to do. In this case, as already described based on the configuration shown in FIG. 5, the forward voltage obtained from the voltage detection terminal 12 is divided by the number of measurement elements used, and light emission display is performed based on the divided value. It is desirable to control the constant voltage applied to the pixel.

  In the embodiment shown in FIG. 6 described above, the operational effects of the configuration shown in FIG. 3 can be enjoyed as they are. Furthermore, since the driving TFT in the measurement pixel can be operated in the linear region while the driving TFT in the light emitting display pixel is operated in the saturation region, the voltage detection terminal 12 can be operated more accurately by the measuring element. A forward voltage can be obtained. Thereby, the precision of correction of the constant voltage output from the voltage control unit can be further improved.

FIG. 7 shows another means by which the driving TFT in the light emitting display pixel can be operated in the saturation region and the driving TFT in the measurement pixel can be reliably operated in the linear region. This corresponds to the invention described in claim 1 . In FIG. 7, parts having the same functions as those shown in FIG. 6 already described are denoted by the same reference numerals, and therefore detailed description thereof is omitted.

  The configuration shown in FIG. 7 is different from the configuration shown in FIG. 6 described above in that the constant current circuit 11 is arranged on the cathode side of the measuring element. A connection point between each cathode of the measuring element and the constant current circuit 11 is made to the voltage detection terminal 12, and this terminal voltage is sampled by the sampling and holding circuit 16. Therefore, also in the embodiment shown in FIG. 7, the same operational effects as those of the embodiment shown in FIG. 6 already described can be obtained.

Further, FIG. 8 also shows another means that can operate the driving TFT in the light emitting display pixel in the saturation region and can reliably operate the driving TFT in the measurement pixel in the linear region. This corresponds to the invention described in claim 1 . In FIG. 8, parts having the same functions as those shown in FIG. 6 already described are denoted by the same reference numerals, and therefore detailed description thereof is omitted.

  The configuration shown in FIG. 8 is different from the configuration shown in FIG. 6 described above in that an N-channel type is used for each driving TFT in the light emitting display pixel and the measurement pixel. Therefore, the EL elements constituting the light emitting element and the measuring element are connected in reverse polarities, and the constant current source 11 functions as a current sink circuit. Therefore, also in the embodiment shown in FIG. 8, the same effects as those of the embodiment shown in FIG. 6 already described can be obtained.

  In the embodiment described above, the forward voltage Vf obtained by each measurement pixel 10b is sampled and held, and the drive voltage applied to the light emitting display pixel 10a is analog controlled based on this hold value. However, for example, the hold value can be A / D converted into digital data, and the driving voltage applied to the light emitting display pixel 10a can be controlled based on this. When such a configuration is adopted, the averaging process of the forward voltage Vf can be facilitated, and when a part of the measurement pixel 10b becomes defective, the pixel from the defective pixel is detected. Processing such as stopping the acquisition of Vf can be easily performed.

  In the embodiment described above, the description has been made based on the case where the conductance control system configuration is adopted as the light emitting display pixel 10a. However, the present invention can be applied to the light emitting display device having such a specific configuration. In addition, for example, a voltage writing method, a current writing method, a driving method of 3 TFT method for realizing digital gradation, that is, SES (Simultaneous-Erasing-Scan = simultaneous erasing method), and further, a threshold voltage correction method, a current mirror method The present invention can be similarly applied to a light emitting display device using an active drive pixel configuration such as the above.

  Furthermore, in the embodiment described above, the same electrical connection configuration is used for the light emitting display pixel 10a and the measurement pixel 10b, but the configurations are different from each other. Also good.

  The above-described light-emitting display device can enjoy the functions and effects described above as they are by adopting it in various electronic devices that require this type of display device.

It is a figure which shows the equivalent circuit of an organic EL element. It is a figure which shows the various characteristics of an organic EL element. It is the circuit block diagram which showed the basic composition of the light emission display device concerning this invention. FIG. 4 is a circuit configuration diagram illustrating a measurement pixel portion in the configuration illustrated in FIG. 3. 1 is a circuit configuration diagram showing a first embodiment of a light emitting display device according to the present invention; It is the circuit block diagram which similarly showed 2nd Embodiment. It is the circuit block diagram which similarly showed 3rd Embodiment. It is the circuit block diagram which similarly showed 4th Embodiment.

Explanation of symbols

10 Light-emitting display panel (light-emitting display device)
DESCRIPTION OF SYMBOLS 10A Light emission display area 10a Light emission display pixel 10B Measurement pixel area 10b Measurement pixel 11 Constant current source 12 Voltage detection terminal 13 Data driver 14 Scan driver 15 Controller IC
16 Sampling and holding circuit 17 Power supply circuit 18 Voltage controller C1 Charge holding capacitor E1 Light emitting element, measuring element (organic EL element)
Tr1 control TFT
Tr2 driving TFT
n1, n2, ... control lines m1, m2, ... data lines p1, p2, ... power supply lines

Claims (10)

  1. An active drive type light emitting display device in which a large number of light emitting display pixels each including at least a light emitting element and a driving TFT for applying a driving current to the light emitting element are arranged,
    The light-emitting display device includes a plurality of power supply circuits that supply a driving voltage to the light-emitting display pixels, at least one measuring element for obtaining a forward voltage, and a driving TFT that supplies a driving current to the element. and measuring pixels are arranged, the measuring device may be any one at least aging properties and temperature dependence of the light emitting elements constituting the light emitting display pixels have the same electrical characteristics, the measurement The potential on the anode side or the cathode side of the light emitting element and the light emitting element is set to a different potential,
    A forward voltage generated in the measuring element in a state where a drive current is applied by the drive TFT is derived and supplied to the power supply circuit, and the power supply circuit is configured to display the light emitting display based on the forward voltage. An active drive light emitting display device configured to control the level of a drive voltage of a pixel for use .
  2. 2. The active drive light emitting display device according to claim 1, wherein each of the measurement elements has an electrical characteristic that is at least one of a temporal change characteristic and a temperature dependency .
  3. The light emitting display pixels are arranged in a matrix at intersections of data lines and control lines, and the measurement pixels are arranged in a line along one data line, and are used in the measurement pixels. 3. The active drive light emitting display device according to claim 1 , wherein a line is shared with a control line used in the light emitting display pixel.
  4. The operating power of the measuring pixel active drive type light emitting display device according to any one of claims 1 to claim 3, characterized in that a constant current source.
  5. The active drive type light emitting display device according to claim 4 , wherein the current value of the constant current source is variable.
  6. 6. The active drive light emitting display device according to claim 4 , wherein a forward voltage of the measuring element is obtained between the constant current source and the measuring pixel.
  7. The active driving light emitting display device according to claim 1, wherein the driving TFT constituting the measuring pixel is operated in a linear region.
  8. The driving TFT constituting the light emitting display pixel includes an active driven light emitting display device according to any one of claims 1 to claim 7, characterized in that to operate in the saturation region at a predetermined gate voltage.
  9. A light emitting element in the light emitting display pixel, and the measuring element in the measuring pixel, any claims 1, characterized in that it is constituted by an organic EL element using an organic compound in the light emitting layer of claim 8 2. An active drive type light emitting display device according to item 1.
  10. An electronic device equipped with the active drive type light emitting display device according to any one of claims 1 to 9 .
JP2004172581A 2004-06-10 2004-06-10 Active drive type light emitting display device and electronic device equipped with the display device Active JP4539963B2 (en)

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JP2009025741A (en) * 2007-07-23 2009-02-05 Hitachi Displays Ltd Image display device and its pixel deterioration correction method
JP5502266B2 (en) * 2007-07-23 2014-05-28 株式会社ジャパンディスプレイ Display device

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