JP2010044257A - Display device and drive control method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reconcile increase in precision of correction of characteristic deviation of a drive transistor with acquisition of display operation and a characteristic value, and to simplify a pixel circuit and drive control. <P>SOLUTION: A display device makes first and second reference currents flow from the source terminal of the drive transistor 11b toward a data line 14 via a source connection switch 11e, acquires first and second voltages for calculating characteristic values based on voltage VB and the voltage of the source terminal of the drive transistor 11b in an equilibrium state where the first reference current becomes equal to the current flowing in the drive transistor 11b, acquires a characteristic value according to the threshold voltage of the drive transistor and a characteristic value according to mobility based on the first and second reference current values and the first and second voltages for calculating characteristic values, and outputs, to the source terminal of the drive transistor 11b, a data signal based on the acquired characteristic values and the driving voltage of the drive transistor 11b according to the quantity of light emission of a light emitting element 11a. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a display device including a light emitting element driven by an active matrix method and a drive control method for the display device.

  Conventionally, display devices using light-emitting elements such as organic EL light-emitting elements have been proposed, and their use in various fields such as displays for televisions and mobile phones has been proposed.

  In general, an organic EL light emitting element is a current driven light emitting element. Therefore, unlike a liquid crystal display, a selection transistor that selects a pixel circuit as a driving circuit thereof, a storage capacitor that holds charges according to a display image, and organic EL light emission A driving transistor for driving the element is at least necessary (see, for example, Patent Document 1).

  Conventionally, a thin film transistor made of low-temperature polysilicon or amorphous silicon has been used in a pixel circuit of an active matrix organic EL display device.

  However, a low-temperature polysilicon thin film transistor can obtain high mobility and threshold voltage stability, but has a problem in uniformity of mobility. Amorphous silicon thin film transistors can achieve mobility uniformity, but have problems of low mobility and threshold voltage variation over time.

The non-uniformity of mobility and the instability of the threshold voltage as described above appear as unevenness in the display image. Thus, for example, Patent Document 2 proposes a display device in which a diode connection type compensation circuit is provided in a pixel circuit.
JP-A-8-234683 JP 2003-255856 A JP 2006-171109 A JP 2002-278513 A JP 2005-284172 A

  However, if the compensation circuit described in Patent Document 2 is provided, the pixel circuit becomes complicated, leading to an increase in cost due to a decrease in yield and a decrease in aperture ratio.

  The display device described in Patent Document 2 is a so-called voltage program method, but a current program method display device has also been proposed. In this current programming display device, both the threshold voltage and mobility of the driving transistor can be corrected, but the actual driving current of the driving transistor is driven outside the active matrix substrate on which the pixel circuit is arranged. Since the circuit flows from the circuit to the selected pixel, there is a problem in that the programming time becomes extremely long due to the distributed capacitance on the wiring when programming in a low gradation region where the driving current becomes a minute current. Further, a current program type display device improved to solve this problem has been proposed in Patent Document 3, but in the case of a large panel, the problem is that the program writing speed is still slow. .

  For example, in Patent Document 4 and Patent Document 5, a current measuring device is provided for each pixel circuit array outside the active matrix substrate on which the pixel circuit is arranged, and the driving current of the driving transistor is measured by this current measuring device. Based on the measured driving current value, a characteristic value such as a threshold voltage and mobility of the driving transistor is calculated and stored, and the correction circuit is used as the gate voltage of the driving transistor based on the characteristic value. A method has been proposed in which both the simplification of the pixel circuit and the characteristic correction of the driving transistor are made compatible by programming to the above.

  However, in the methods described in Patent Document 4 and Patent Document 5, the turn-off current of the organic EL light-emitting element of the non-selected pixel circuit is mixed into the measured drive current, and an accurate drive current cannot be measured. In addition, since a minute driving current of one pixel circuit is measured, there is a problem in practical use in current measurement accuracy. Further, since it takes time to measure the drive current, it is impossible to obtain both correction data and display operation, and correction data cannot be updated in real time.

  In view of the above circumstances, the present invention provides a display device capable of realizing high accuracy of correction of a characteristic deviation of a driving transistor, coexistence of display operation and acquisition of a characteristic value, and simplification of a pixel circuit and driving control. An object of the present invention is to provide a drive control method for the display device.

  According to a first display device driving control method of the present invention, a light emitting element, a driving transistor in which a source terminal is connected to an anode terminal of the light emitting element, and a driving current is supplied to the light emitting element, a gate terminal and a source terminal of the driving transistor, A capacitor connected between the gate terminal, a gate connection switch connected between the gate terminal of the driving transistor and a voltage source supplying a predetermined voltage, and data supplying a predetermined signal to the source terminal of the driving transistor A drive control method for a display device including an active matrix substrate in which a large number of pixel circuits having source connection switches connected to a line are arranged, wherein a first reference current set in advance is applied to a drive transistor The first reference current and the current flowing in the driving transistor are caused to flow from the source terminal to the data line via the source connection switch. The first characteristic value calculation voltage is acquired based on the voltage at the source terminal of the driving transistor in the balanced state and the predetermined voltage, and the second reference current set in advance is used as the driving transistor. The voltage of the source terminal of the driving transistor in the equilibrium state in which the second reference current and the current flowing through the driving transistor are equal to each other and flow from the source terminal to the data line through the source connection switch, and the predetermined voltage The second characteristic value calculation voltage is obtained based on the first reference current value, the second reference current value, the first characteristic value calculation voltage, and the second characteristic value calculation voltage. The characteristic value according to the threshold voltage of the driving transistor and the characteristic value according to the mobility are acquired, and the acquired characteristic value and the driving voltage of the driving transistor according to the light emission amount of the light emitting element And outputs the data signal to the data line and the source terminal of the driving transistor through source connection switch-based.

  According to a second display device driving control method of the present invention, a light emitting element, a driving transistor in which a source terminal is connected to an anode terminal of the light emitting element, and a driving current is supplied to the light emitting element, a gate terminal and a source terminal of the driving transistor, A capacitor connected between the gate terminal, a gate connection switch connected between the gate terminal of the driving transistor and a voltage source supplying a predetermined voltage, and data supplying a predetermined signal to the source terminal of the driving transistor A plurality of pixel circuits having source connection switches connected to the lines are arranged, and an active matrix substrate having a data line provided for each column of the pixel circuits and a row of the pixel circuits are sequentially selected and selected. The scanning drive unit that turns on the source connection switch of the pixel circuit in the row and the scanning drive unit repeatedly selects the pixel circuit rows from the first row to the last row. A display device drive control method comprising: a control unit that displays an image based on a data signal for each frame, and a part of the pixel circuits in a row of pixel circuits selected by the scan drive unit For each selected pixel circuit, a first reference current set in advance is supplied from the source terminal of the driving transistor to the data line via the source connection switch, The first characteristic value calculation voltage is acquired based on the voltage of the source terminal of the driving transistor and the predetermined voltage in an equilibrium state where the reference current of 1 and the current flowing through the driving transistor are equal, The set second reference current is supplied from the source terminal of the driving transistor to the data line via the source connection switch, and the second reference current is supplied. The second characteristic value calculation voltage is acquired based on the voltage of the source terminal of the driving transistor and the predetermined voltage in an equilibrium state in which the current flowing through the driving transistor is equal, and the first reference current value And the second reference current value, the first characteristic value calculation voltage, and the second characteristic value calculation voltage, the characteristic value corresponding to the threshold voltage of the driving transistor and the characteristic value corresponding to the mobility are acquired. The data signal based on the acquired characteristic value and the driving voltage of the driving transistor corresponding to the light emission amount of the light emitting element is output to the source terminal of the driving transistor via the data line and the source connection switch, and the acquisition is performed. The characteristic value stored in the characteristic value storage unit is stored in the characteristic value storage unit for the non-selected pixel circuits that are not selected among the pixel circuits in the row selected by the scan driving unit. A data signal based on the characteristic value stored at the time of selection and the driving voltage of the driving transistor corresponding to the light emission amount of the light emitting element is output to the source terminal of the driving transistor of the non-selected pixel circuit.

  According to a third display device driving control method of the present invention, a light emitting element, a driving transistor in which a source terminal is connected to an anode terminal of the light emitting element, and a driving current is supplied to the light emitting element, a gate terminal and a source terminal of the driving transistor, A capacitor connected between the gate terminal, a gate connection switch connected between the gate terminal of the driving transistor and a voltage source supplying a predetermined voltage, and data supplying a predetermined signal to the source terminal of the driving transistor A plurality of pixel circuits having source connection switches connected to the lines are arranged, and an active matrix substrate having a data line provided for each column of the pixel circuits and a row of the pixel circuits are sequentially selected and selected. The scanning drive unit that turns on the source connection switch of the pixel circuit in the row and the scanning drive unit repeatedly selects the pixel circuit rows from the first row to the last row. And a control unit for displaying an image based on a data signal for each frame to perform a drive control method for a display device, and a part of pixels in a row of pixel circuits from the first row to the last row A circuit row is sequentially switched for each frame and selected, and for the selected selected pixel circuit row, a preset first reference current is directed from the source terminal of the driving transistor to the data line via the source connection switch. And obtaining the first characteristic value calculation voltage based on the voltage of the source terminal of the driving transistor and a predetermined voltage in an equilibrium state where the first reference current and the current flowing in the driving transistor are equal. A second reference current set in advance is caused to flow from the source terminal of the driving transistor toward the data line via the source connection switch, and the second reference current and The second characteristic value calculation voltage is obtained based on the voltage of the source terminal of the driving transistor and a predetermined voltage in an equilibrium state in which the current flowing through the dynamic transistor is equal, and the first reference current value and the second A characteristic value corresponding to the threshold voltage of the driving transistor and a characteristic value corresponding to the mobility are obtained based on the reference current value, the first characteristic value calculating voltage, and the second characteristic value calculating voltage. A data signal based on the acquired characteristic value and the driving voltage of the driving transistor corresponding to the light emission amount of the light emitting element is output to the source terminal of the driving transistor via the data line and the source connection switch, and the acquired characteristic value Is stored in the characteristic value storage unit, and for the non-selected pixel circuit rows that are not selected other than the part of the pixel circuit rows, the characteristic value stored in the characteristic value storage unit at the time of the previous selection is stored. A data signal based on the driving voltage of the driving transistor corresponding to the light emission amount of the light emitting element is output to the source terminal of the driving transistor in the non-selected pixel circuit row.

  A first display device of the present invention includes a light emitting element, a source terminal connected to an anode terminal of the light emitting element, a driving transistor for passing a driving current through the light emitting element, and a connection between the gate terminal and the source terminal of the driving transistor. Between the gate terminal of the driving transistor and the voltage source supplying a predetermined voltage, and between the source terminal of the driving transistor and a data line supplying a predetermined signal A plurality of pixel circuits having source connection switches connected to each other, an active matrix substrate having a data line provided for each column of the pixel circuits, and a first reference current set in advance as a source terminal of the driving transistor To the data line through the source connection switch, the first reference current and the current flowing through the driving transistor are not equal. The first characteristic value calculation voltage is acquired based on the voltage of the source terminal of the driving transistor in the balanced state and the predetermined voltage, and the second reference current set in advance is used as the source terminal of the driving transistor. Based on the voltage of the source terminal of the driving transistor and the predetermined voltage in an equilibrium state in which the second reference current and the current flowing in the driving transistor are equal to each other. A characteristic value calculation voltage acquisition unit for acquiring a second characteristic value calculation voltage, a first reference current value, a second reference current value, a first characteristic value calculation voltage, and a second characteristic value calculation The characteristic value according to the threshold voltage of the driving transistor and the characteristic value according to the mobility based on the voltage, and the characteristic value acquired by the characteristic value acquisition unit And a source driving circuit having a data signal output unit for outputting a data signal based on the driving voltage of the driving transistor according to the light emission amount of the element to the source terminal of the driving transistor via the data line and the source connection switch. It is characterized by that.

  According to a second display device of the present invention, a light emitting element, a source terminal connected to the anode terminal of the light emitting element, a driving transistor for passing a driving current to the light emitting element, and a connection between the gate terminal and the source terminal of the driving transistor Between the gate terminal of the driving transistor and the voltage source supplying a predetermined voltage, and between the source terminal of the driving transistor and a data line supplying a predetermined signal A plurality of pixel circuits having source connection switches connected to each other, an active matrix substrate having a data line provided for each column of the pixel circuits, and a row of the pixel circuits are sequentially selected, and the pixel circuit in the selected row A scanning drive unit that turns on the source connection switch of the first transistor and a first reference current that is set in advance from the source terminal of the driving transistor. The first reference current and the current flowing in the driving transistor are equalized, and the first terminal current of the driving transistor in an equilibrium state and the predetermined voltage are set based on the predetermined voltage. A characteristic value calculation voltage of 1 is acquired, and a preset second reference current is supplied from the source terminal of the driving transistor toward the data line via the source connection switch, and the second reference current and the driving voltage are supplied. A characteristic value calculation voltage acquisition unit configured to acquire a second characteristic value calculation voltage based on the voltage of the source terminal of the driving transistor in an equilibrium state in which the current flowing through the transistor is equal and the predetermined voltage; Characteristic value corresponding to the threshold voltage of the driving transistor based on the reference current value, the second reference current value, the first characteristic value calculation voltage, and the second characteristic value calculation voltage And a characteristic value acquisition unit that acquires a characteristic value according to the mobility, and a data signal based on the characteristic value acquired by the characteristic value acquisition unit and the driving voltage of the driving transistor according to the light emission amount of the light emitting element And a source drive unit having a data signal output unit that outputs to the source terminal of the drive transistor via the source connection switch, a characteristic value storage unit that stores characteristic values of the drive transistors of all the pixel circuits, and a scan drive unit And a control unit that displays an image based on the data signal for each frame by repeatedly selecting the row of the pixel circuit from the first row to the last row, and the characteristic value calculation voltage acquisition unit is operated by the scan driving unit. A part of the pixel circuits in the selected row is sequentially switched and selected for each frame, and the first characteristic value calculation power is selected for the selected pixel circuit. The characteristic value acquisition unit acquires the characteristic value for the pixel circuit selected by the characteristic value calculation voltage acquisition unit, and acquires the acquired characteristic value. The characteristic value for the selected pixel circuit that has been output to the characteristic value storage unit and previously stored in the characteristic value storage unit is updated, and the data signal output unit is selected by the characteristic value calculation voltage acquisition unit. For the selected pixel circuit, a data signal based on the characteristic value acquired by the characteristic value acquisition unit at the time of selection and the driving voltage of the driving transistor according to the light emission amount of the light emitting element is transmitted to the source terminal of the driving transistor of the selected pixel circuit For the non-selected pixel circuit that has not been selected by the characteristic value calculation voltage acquisition unit, the driving transistor according to the characteristic value stored in the characteristic value storage unit and the light emission amount of the light emitting element is stored. And characterized in that for outputting a data signal based on the drive voltage of the register to the source terminal of the driving transistor of the non-selected pixel circuit. In the third display device of the present invention, a light emitting element, a source terminal connected to the anode terminal of the light emitting element, a driving transistor for passing a driving current to the light emitting element, and a connection between the gate terminal and the source terminal of the driving transistor are connected. Between the gate terminal of the driving transistor and the voltage source supplying a predetermined voltage, and between the source terminal of the driving transistor and a data line supplying a predetermined signal A plurality of pixel circuits having source connection switches connected to each other, an active matrix substrate having a data line provided for each column of the pixel circuits, and a row of the pixel circuits are sequentially selected, and the pixel circuit in the selected row A scanning drive unit that turns on the source connection switch of the first transistor and a first reference current that is set in advance from the source terminal of the driving transistor. The first reference current and the current flowing through the driving transistor are made equal to each other, and the first reference current and the current flowing through the driving transistor are equal to each other. And a second reference current set in advance is passed from the source terminal of the driving transistor toward the data line via the source connection switch, and the second reference current and the driving transistor are obtained. A characteristic value calculation voltage acquisition unit for acquiring a second characteristic value calculation voltage based on the voltage of the source terminal of the driving transistor and a predetermined voltage in an equilibrium state in which the current flowing through Based on the current value, the second reference current value, the first characteristic value calculation voltage, and the second characteristic value calculation voltage, the characteristic value and shift corresponding to the threshold voltage of the driving transistor are determined. A characteristic value acquisition unit that acquires a characteristic value according to the degree, and a data signal based on the characteristic value acquired by the characteristic value acquisition unit and the driving voltage of the driving transistor according to the light emission amount of the light emitting element A source driving unit having a data signal output unit that outputs to the source terminal of the driving transistor via the connection switch, a characteristic value storage unit that stores the characteristic values of the driving transistors of all the pixel circuits, and a scanning driving unit A control unit that displays an image based on a data signal for each frame by repeatedly selecting pixel circuit rows from the first row to the last row, and the characteristic value calculation voltage acquisition unit includes the first row to the last row. Some pixel circuit rows among the pixel circuit rows up to and including are sequentially switched and selected for each frame, and the first characteristic value calculation voltage and the second voltage are selected for the selected pixel circuit row. The characteristic value calculation unit acquires a characteristic value for the pixel circuit row selected by the characteristic value calculation voltage acquisition unit, and stores the acquired characteristic value as a characteristic value. The characteristic value for the selected pixel circuit row previously output to the characteristic value storage unit and stored in the characteristic value storage unit is updated, and the data signal output unit is selected by the characteristic value calculation voltage acquisition unit For the selected pixel circuit row, a data signal based on the characteristic value acquired by the characteristic value acquisition unit at the time of selection and the driving voltage of the driving transistor according to the light emission amount of the light emitting element is transmitted to the driving transistor of the selected pixel circuit row. For non-selected pixel circuit rows that are output to the source terminal and not selected by the characteristic value calculation voltage acquisition unit, the characteristic value stored in the characteristic value storage unit at the previous selection and the light emission amount of the light emitting element And characterized in that for outputting a data signal based on the drive voltage of the dynamic transistor to the source terminal of the driving transistor of the non-selected pixel circuit row.

  In the first to third display devices according to the present invention, the voltage at the source terminal approaches the voltage in the equilibrium state with respect to the source terminal of the driving transistor immediately before flowing the first reference current. Is expected to supply the second expected voltage such that the voltage at the source terminal approaches the voltage in the equilibrium state immediately before the second reference current is supplied. A voltage supply unit can be provided.

  In the first to third display devices of the present invention, a reverse bias voltage output unit that supplies a reverse bias voltage having a magnitude corresponding to a data signal output to the driving transistor to the gate terminal of the driving transistor. Can be further provided.

  Further, the driving transistor can be formed of a thin film transistor having a current characteristic with a negative threshold voltage.

  Further, the driving transistor can be formed of a thin film transistor made of IGZO (InGaZnO).

  In the second display device of the present invention, a part of the pixel circuits selected by the current value acquisition unit includes a pixel circuit having a red light emitting element belonging to one display pixel and a green light emitting element. A pixel circuit having a pixel circuit and a blue light-emitting element can be obtained.

  In the first to third display devices of the present invention, a common electrode line that supplies different voltages during a reverse bias voltage application period and a period other than the reverse bias voltage application period is connected to the cathode terminal of the light emitting element. can do.

  According to the first to third display devices and the drive control method thereof according to the present invention, a predetermined voltage is supplied to the gate terminal of the drive transistor and the preset first and second reference currents are used for the drive. The first characteristic value calculation voltage and the second voltage are supplied from the source terminal of the transistor through the source connection switch to the data line, based on the voltage of the source terminal of the driving transistor in the equilibrium state and the predetermined voltage. Since the characteristic value calculation voltage is acquired, and the characteristic value of the driving transistor is acquired based on the characteristic value calculation voltage, compared with the conventional method of setting the gate voltage and measuring the driving current, A simple and inexpensive circuit configuration can be obtained, and high-precision measurement can be performed in a short time.

  Accordingly, it is possible to insert the characteristic value acquisition operation of the driving transistor in the normal display data update cycle period, and the characteristic value acquisition operation and the correction operation can be performed in parallel with the display operation.

  Furthermore, according to the first display device and the drive control method thereof of the present invention, the correction data is updated as needed, so that the display stability during continuous operation for a long time is drastically improved and the correction data of all the pixel circuits is corrected. Can be eliminated, and the cost of the apparatus can be reduced.

  In addition, according to the second display device and the drive control method thereof of the present invention, a part of the pixel circuits in the row selected by the scan driver is sequentially switched for each frame and selected. Since the characteristic value is acquired for the selected pixel circuit, there is no need to provide a characteristic value acquisition unit for each pixel circuit column, and space saving and cost reduction can be achieved.

  In addition, according to the third display device and the drive control method thereof of the present invention, a part of the pixel circuit rows from the first row to the last row are sequentially switched for each frame and selected. Since the characteristic value is acquired for the selected pixel circuit row, for example, even when the scanning time of all the pixel circuit rows such as a high-definition panel is short, the time for acquiring the characteristic value is obtained for some pixel circuit rows. It is possible to obtain the characteristic values for all the pixel circuit rows by switching the pixel circuit rows for obtaining the characteristic values for each frame.

  In the first to third display devices of the present invention, the first display device is such that the voltage of the source terminal approaches the voltage in the equilibrium state with respect to the source terminal of the driving transistor immediately before flowing the first reference current. In addition to supplying the expected voltage, the second predicted voltage is supplied to the source terminal of the driving transistor immediately before the second reference current is supplied so that the voltage of the source terminal approaches the voltage in the equilibrium state. In this case, the time from when the reference current starts to flow until it reaches the equilibrium state can be shortened.

  In addition, when a reverse bias voltage output unit for supplying a reverse bias voltage having a magnitude corresponding to the data signal output to the driving transistor to the gate terminal of the driving transistor is further provided, the voltage of the driving transistor The threshold voltage shift due to stress can be appropriately suppressed.

  In addition, when the reverse bias voltage is supplied to the driving transistor as described above, the maximum voltage that can be set as the reverse bias voltage is the power supply voltage. It may occur.

  Therefore, when the driving transistor is constituted by a thin film transistor having a current characteristic with a negative threshold voltage, a positive and negative voltage is applied as Vgs in the display operation. The voltage also has both positive and negative polarities, and the reverse bias shortage due to the limit value of the reverse bias voltage can be reduced.

  In addition, when a common electrode line that supplies different voltages in the reverse bias voltage application period and the period other than the reverse bias voltage application period is connected to the cathode terminal of the light emitting element, light emission by applying the reverse bias voltage is performed. It is possible to prevent erroneous light emission of the element.

  Further, when the driving transistor is formed of a thin film transistor made of IGZO (InGaZnO), the reversible threshold voltage shift characteristic of the thin film transistor made of IGZO can be used. That is, the threshold voltage of a thin film transistor made of IGZO shifts due to voltage stress caused by application of a gate voltage, but unlike an amorphous silicon thin film transistor, it returns to its initial value by applying a zero bias. By utilizing this characteristic, for example, the threshold voltage can be returned to the initial value during a non-display period such as when a black screen is displayed or when the power is turned off. it can.

  Hereinafter, an organic EL display device to which a first embodiment of a display device of the present invention is applied will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of an organic EL display device to which the first embodiment of the present invention is applied.

  As shown in FIG. 1, the organic EL display device according to the first embodiment of the present invention holds charges according to the data signal output from the source drive circuit 12, and drives according to the held charge amount. An active matrix substrate 10 in which a large number of pixel circuits 11 for passing a current to the organic EL light emitting elements are arranged two-dimensionally, a source drive circuit 12 for outputting a data signal to each pixel circuit 11 of the active matrix substrate 10, and an active matrix substrate A scanning drive circuit 13 that outputs a scanning signal to each of the ten pixel circuits 11, and a timing signal based on display data and a synchronizing signal corresponding to the image data are output to the source driving circuit 12, and a synchronizing signal is output to the scanning driving circuit 13. And a control unit 16 that outputs a timing signal based thereon.

  The active matrix substrate 10 supplies a number of data lines 14 that supply the data signal output from the source driving circuit 12 to each pixel circuit column, and a scanning signal output from the scanning driving circuit 13 to each pixel circuit row. And a large number of scanning lines 15. The data lines 14 and the scanning lines 15 are provided in a lattice shape so as to be orthogonal to each other. A pixel circuit 11 is provided in the vicinity of the intersection of the data line 14 and the scanning line 15.

  As shown in FIG. 2, each pixel circuit 11 has an organic EL light emitting element 11a and a source terminal S connected to the anode terminal of the organic EL light emitting element 11a. A driving transistor 11b to be flown, a capacitive element 11c connected between a gate terminal G and a source terminal S of the driving transistor 11b, one end of the capacitive element 11c, a gate terminal G of the driving transistor 11b, and the data line 14 And a measuring transistor 11e connected between the source terminal S of the driving transistor 11b and the data line 14.

  The organic EL light emitting element 11 a includes a light emitting unit 50 that emits light by a driving current passed by the driving transistor 11 b and a parasitic capacitance 51 of the light emitting unit 50. The cathode terminal of the organic EL light emitting element 11a is connected to the ground potential.

  The driving transistor 11b, the selection transistor 11d, and the measurement transistor 11e are N-type thin film transistors. As a kind of the thin film transistor of the driving transistor 11b, an amorphous silicon thin film transistor or an inorganic oxide thin film transistor can be used. As the inorganic oxide film thin film transistor, for example, a thin film transistor made of an inorganic oxide film made of IGZO (InGaZnO) can be used. However, not only IGZO but also IZO (InZnO) can be used.

  As shown in FIG. 2, a predetermined fixed voltage Vdd is supplied to the drain terminal D of the driving transistor 11b. The fixed voltage VB is supplied to the terminal of the selection transistor 11d that is not connected to the gate terminal G of the driving transistor 11b. The magnitude of the fixed voltage VB will be described in detail later.

  Based on the timing signal output from the control unit 16, the scanning drive circuit 13 is turned off to turn on the on-scan signal Vscan (on) for turning on the selection transistor 11 d and the measurement transistor 11 e of the pixel circuit 11. The scanning signal Vscan (off) is sequentially output to each scanning line 15.

  FIG. 3 shows a detailed configuration diagram of the source drive circuit 12. The source driving circuit 12 includes a large number of circuits shown in FIG. 3, and the circuit shown in FIG. 3 is connected to each data line 14 of the active matrix substrate 10.

  As shown in FIG. 3, the source drive circuit 12 includes a fixed voltage source 12a, a D / A converter 12b, a first differential amplifier 12c, a second differential amplifier 12d, and an A / D converter 12e. A first reference current source 12f, a second reference current source 12g, a calculation unit 12h, a first switch element 12i, a second switch element 12j, and a third switch element 12k. Yes.

  The fixed voltage source 12a supplies a fixed voltage VB to the non-inverting input terminals of the first differential amplifier 12c and the second differential amplifier 12d. The fixed voltage VB and the fixed voltage VB supplied to the gate terminal G of the driving transistor 11b described above have the same voltage value. These may be supplied from the same voltage source, or may be supplied from different voltage sources.

  The D / A converter 12b converts a display gate-source voltage, which will be described later, into an analog signal, and supplies the display gate-source voltage of the analog signal to the inverting input terminal of the first differential amplifier 12c. It is.

  The first differential amplifier 12c calculates and outputs a display source voltage based on the difference between the display gate-source voltage output from the D / A converter 12b and the fixed voltage VB.

  The second differential amplifier 12d is in a balanced state by connecting the fixed voltage VB supplied from the fixed voltage source 12a and the first or second reference current source 12f, 12g to the source terminal S of the driving transistor 11b. The differential voltage with respect to the source voltage is calculated.

  The A / D converter 12e converts the differential voltage output from the second differential amplifier 12d into a digital signal.

  The first reference current source 12f is connected to the source terminal S of the driving transistor 11b via the second switch element 12j and the data line 14, and allows the first reference current to flow.

  The second reference current source 12g is connected to the source terminal S of the driving transistor 11b via the third switch element 12k and the data line 14, and allows the second reference current to flow.

  The first switch element 12i switches the connection between the first differential amplifier 12c and the data line 14, and can be constituted by, for example, a thin film transistor.

  The second switch element 12j switches the connection between the first reference current source 12f and the data line 14, and can be composed of, for example, a thin film transistor.

  The third switch element 12k switches the connection between the second reference current source 12g and the data line 14, and can be constituted by, for example, a thin film transistor.

  The calculation unit 12h calculates a characteristic value of the driving transistor 11b based on the differential voltage, the first reference current, and the second reference current output from the second differential amplifier 12d, and the characteristic value and the control unit The display gate-source voltage supplied to the driving transistor 11b is calculated on the basis of the display data output from 16 and the display gate-source voltage is output to the D / A converter 12b. .

  FIG. 4 shows a detailed configuration diagram of the calculation unit 12h. The calculation unit 12h includes first to fourth register units 20a to 20d, a ΔVGS calculation unit 20e, a Δ√ID calculation unit 20f, a MU calculation unit 20g, a VTH calculation unit 20h, and a VGS calculation unit 20i. I have.

  The first register unit 20a and the second register unit 20b hold the first characteristic value calculation voltage and the second characteristic value calculation voltage calculated by the second differential amplifier 12d, respectively.

  In the third register unit 20c and the fourth register unit 20d, the first reference current value and the second reference current value are respectively set in advance.

  The ΔVGS calculation unit 20e is a difference between the first measurement gate-source voltage held in the first register unit 20a and the second measurement gate-source voltage held in the second register unit 20b. The differential gate-source voltage is calculated.

  The Δ√ID calculation unit 20f calculates a current change amount based on the first reference current value held in the third register unit 20c and the second reference current value held in the fourth register unit 20d. It is.

  The MU calculation unit 20g corresponds to the mobility of the driving transistor 11b based on the current change amount calculated by the Δ√ID calculation unit 20f and the differential gate-source voltage calculated by the ΔVGS calculation unit 20e. A characteristic value is calculated.

  The VTH calculation unit 20h corresponds to the threshold voltage of the driving transistor 11b based on the current change amount calculated by the Δ√ID calculation unit 20f and the differential gate-source voltage calculated by the ΔVGS calculation unit 20e. A characteristic value is calculated.

  The VGS calculation unit 20i is based on the display data output from the control unit 16, the characteristic value corresponding to the mobility calculated by the MU calculation unit 20g, and the characteristic value corresponding to the threshold voltage calculated by the VTH calculation unit 20h. The gate-source voltage for display is calculated.

  Next, the operation of the organic EL display device of the first embodiment will be described with reference to the timing chart shown in FIG. 5 and FIGS. 6 to 8. In FIG. 5, the scanning signal Vscan output from the scanning driving circuit 13, the data signal Vdata output from the source driving circuit 12, the gate voltage Vg of the driving transistor 11b, the source voltage Vs, and the gate-source voltage Vgs are shown. The voltage waveform is shown.

  In the organic EL display device of the present embodiment, pixel circuit rows connected to each scanning line 15 of the active matrix substrate 10 are sequentially selected, and a predetermined operation is performed in the selection period in units of one row. Here, an operation performed in the selected period in the selected predetermined pixel circuit row will be described.

  First, a predetermined pixel circuit row is selected by the scanning drive circuit 13, and an on-scan signal as shown in FIG. 5 is output to the scanning line 15 to which the pixel circuit row is connected (time t1 in FIG. 5).

  As shown in FIG. 6, the selection transistor 11d and the measurement transistor 11e are turned on in response to the on-scan signal output from the scan drive circuit 13, and the gate terminal G of the drive transistor 11b and the fixed voltage VB are supplied. Are connected to the source terminal S of the driving transistor 11b, one end of the capacitive element 11c, and the anode terminal of the organic EL light emitting element 11a, and the data line 14.

  Here, as the fixed voltage VB at this time, in order to prevent the organic EL light emitting element 11a from emitting light, it is necessary to satisfy the following expression when the light emission threshold voltage Vf0 of the organic EL light emitting element 11a is used. Vgsmin is the minimum value of the gate-source voltage of the driving transistor 11b.

Vg−Vgsmin <Vf0
VB-Vgsmin <Vf0
VB <Vf0 + Vgsmin
Further, immediately before the above state, since the light emission state of the previous frame is present, the source voltage Vs> Vf0 of the driving transistor 11b is satisfied.

  That is, when the threshold voltage of the driving transistor 11b is Vth, Vgs ≦ Vth, and the current Id does not flow through the driving transistor 11b.

  First, a first characteristic value calculating voltage setting operation is performed (see t1 to t2 in FIG. 5, FIGS. 6 and 7). Specifically, the second switch element 12j of the source drive circuit 12 is turned on, the first reference current source 12f and the data line 14 are connected, and as shown in FIG. 6, the first reference current source 12f The first reference current Is1 is drawn from the pixel circuit 11 toward the source drive circuit 12.

  At this time, since the current Id does not flow through the driving transistor 11b as described above, the first reference current Is becomes the discharge current of the parasitic capacitance 51 of the organic EL light emitting element 11a and the capacitive element 11c. The source voltage Vs of the transistor for transistor 11b decreases.

  When the source voltage Vs of the driving transistor 11b decreases, the gate-source voltage Vgs of the driving transistor 11b increases, and as shown in FIG. 7, a current Id begins to flow through the driving transistor 11b, and finally Id = Is1 Becomes an equilibrium state.

  Then, in the second differential amplifier 12d of the source driving circuit 12, the source voltage Vs1 of the driving transistor 11b in the equilibrium state is subtracted from the fixed voltage VB to calculate the first characteristic value calculation voltage Vgs1. . The first characteristic value calculation voltage Vgs1 is converted into a digital signal by the A / D converter 12e, and then input to the calculation unit 12h and held in the first register unit 20a of the calculation unit 12h.

  Then, a second characteristic value calculation voltage setting operation is performed (see t2 to t3 in FIG. 5, FIGS. 6 and 7). Specifically, the second switch element 12j of the source drive circuit 12 is turned off and the third switch element 12k is turned on, and the second reference current source 12g and the data line 14 are connected, as shown in FIG. As described above, the second reference current Is2 of the second reference current source 12g is drawn from the pixel circuit 11 toward the source drive circuit 12.

  Here, the relationship between the second reference current Is2 and the first reference current Is1 is set to Is2 <Is1. Therefore, the source voltage Vs of the driving transistor 11b is increased by the above operation.

  When the source voltage Vs of the driving transistor 11b increases, the gate-source voltage Vgs of the driving transistor 11b decreases and finally becomes Id = Is2 and becomes an equilibrium state.

  Then, in the second differential amplifier 12d of the source drive circuit 12, the source voltage Vs2 of the drive transistor 11b in the equilibrium state is subtracted from the fixed voltage VB to calculate the second characteristic value calculation voltage Vgs2. . The second characteristic value calculation voltage Vgs2 is converted into a digital signal by the A / D converter 12e, and then input to the calculation unit 12h and held in the second register unit 20b of the calculation unit 12h.

  As shown in FIG. 5, the second reference current Is2 has such a magnitude that the source voltage Vs2 of the driving transistor 11b in the equilibrium state is smaller than the light emission threshold voltage Vf0 of the organic EL light emitting element 11a. Is set.

  Further, it is important to avoid the low current region of the first reference current Is1 and the second reference current Is2 in order to ensure the accuracy of the characteristic value described later, and the vicinity of the maximum driving current of the driving transistor 11b. It is preferable to set the current value in the vicinity of the average drive current.

  Then, a characteristic value calculating operation is performed (t3 to t4 in FIG. 5). Specifically, first, the characteristic value calculation voltage Vgs1 held in the first register unit 20a and the second characteristic value calculation voltage Vgs2 held in the second register unit 20b are output to the ΔVGS calculation unit 20e. The Then, the ΔVGS calculation unit 20e calculates a differential gate-source voltage ΔVGS by subtracting Vgs2 from Vgs1.

  On the other hand, Id1 (= Is1) preset in the third register unit 20c and Id2 (= Is2) preset in the fourth register unit 20d are output to the Δ√ID calculation unit 20f. Then, the Δ√ID calculation unit 20f calculates the current change amount Δ√ID by calculating the following equation.

Δ√ID = √Id1-√Id2
The ΔVGS calculated by the ΔVGS calculating unit 20e and the Δ√ID calculated by the Δ√ID calculating unit 20f are input to the MU calculating unit 20g, and the MU calculating unit 20g calculates the mobility by calculating the following equation. A characteristic value MU corresponding to the above is acquired.

MU = (Δ√ID) ² / (ΔVGS) ²
Also, ΔVGS, Δ√ID, Vgs1 set in the first register unit 20a, and Id1 set in the third register unit 20c are input to the VTH calculation unit 20h, and the VTH calculation unit 20h calculates the following equation: Thus, the characteristic value VTH corresponding to the threshold voltage is calculated.

VTH = -b / a
a = Δ√ID / ΔVGS
b = √Id1-a * Vgs1
Here, how to obtain the above equation for calculating the characteristic value MU according to the mobility and the characteristic value VTH according to the threshold voltage will be described below.

First, from the current formula of the thin film transistor in the saturation region,
Id = (1/2) × μ × Cox × (W / L) × (Vgs−Vth) ²
Where μ is the electron mobility, Cox is the gate oxide film capacity per unit area, W is the gate width, L is the gate length.
(Vgs−Vth) ² = Id / [(1/2) × μ × Cox × (W / L)]
(Vgs−Vth) = √Id / √ [(1/2) × μ × Cox × (W / L)]
Vgs = √Id / √ [(1/2) × μ × Cox × (W / L)] + Vth
From the two Vgs and Id values,
Vgs1 = √Id1 / √ [(1/2) × μ × Cox × (W / L)] + Vth
Vgs2 = √Id2 / √ [(1/2) × μ × Cox × (W / L)] + Vth
(Vgs1-Vgs2) = [√Id1-√Id2] / √ [(1/2) × μ × Cox × (W / L)]
√ [(1/2) × μ × Cox × (W / L)] = [√Id1-√Id2] / (Vgs1-Vgs2)
(1/2) × μ × Cox × (W / L) = [√Id1-√Id2] ² / (Vgs1-Vgs2) ²
(1/2) × μ × Cox × (W / L) = [ΔId] ² / (ΔVGS) ²
Here, the gain characteristic of the driving transistor necessary for the correction is not the mobility μ but the characteristic value MU = (1/2) × μ × Cox × (W / L) corresponding to the mobility. Therefore,
MU = (1/2) × μ × Cox × (W / L) = [ΔId] ² / (ΔVGS) ²
It becomes.

In addition, the characteristic value VTH corresponding to the threshold voltage is the X-axis tangent side of the √Id−Vgs curve.
a = Δ√Id / ΔVgs
b = √Id1-a * Vgs1
VTH = -b / a
It is obtained as

  Then, a display gate-source voltage setting operation is performed (t4 to t5 in FIG. 5). Specifically, the display data output from the control unit 16, the characteristic value MU calculated by the MU calculation unit 20g, and the characteristic value VTH calculated by the VTH calculation unit 20h are input to the VGS calculation unit 20i. Then, the VGS calculation unit 20i calculates the display gate-source voltage Vgsn based on the following equation. Idn is display data.

Idn = MU × (Vgsn−VTH) ²
(Vgsn−VTH) ² = Idn / MU
Vgsn−VTH = √ (Idn / MU)
Vgsn = √ (Idn / MU) + VTH
The Vgsn calculated by the VGS calculation unit 20i is input to the D / A converter 12b, converted into an analog signal, and then input to the inverting input terminal of the first differential amplifier 12c. Then, in the first differential amplifier 12c, the fixed voltage VB is added and converted to Vsn. Then, the third switch element 12k is turned OFF, the first switch element 12i is turned ON, and Vsn is output to the data line 14.

  With the above operation, the gate voltage Vg = VB, the source voltage Vs = Vsn, and Vgs = Vgsn are set in the driving transistor 11b.

  Then, a light emission operation is performed (see FIG. 8 after t5 in FIG. 5). Specifically, an off scanning signal is output from the scanning drive circuit 13 to each scanning line 15 (time t5 in FIG. 5). As shown in FIG. 8, the selection transistor 11d and the measurement transistor 11e are turned off in response to the off-scan signal output from the scan drive circuit 13, and the gate terminal G and the fixed voltage VB of the drive transistor 11b are supplied. As a result, the source terminal S of the driving transistor 11b, one end of the capacitive element 11c, the anode terminal of the organic EL light emitting element 11a, and the data line 14 are disconnected.

  Then, the gate-source voltage Vgs of the driving transistor 11b becomes Vgsn, and the driving current Idn according to the following TFT current equation flows between the drain and source of the driving transistor 11b.

Idn = μ × Cox × (W / L) × (Vgsn−Vth) ²
Where μ is the electron mobility, Cox is the gate oxide film capacity per unit area, W is the gate width, and L is the gate length.

  The drive current Idn charges the parasitic capacitance 51 of the organic EL light emitting element 11a, and the source voltage Vs of the drive transistor 11b rises, but the gate-source voltage Vgsn is held by the holding voltage Vgsn of the capacitance element 11c. Accordingly, the source voltage Vs eventually exceeds the light emission threshold voltage Vf0 of the organic EL light emitting element 11a, and the light emitting operation of the organic EL light emitting element 11a is performed with a constant current.

  Then, a predetermined pixel circuit row is sequentially selected by the scanning drive circuit 13, and the operation from the first measurement source voltage setting operation to the light emission operation is performed for each pixel circuit row, and a desired display image is displayed. .

  Here, a modification of the organic EL display device of the first embodiment will be described. Specifically, in the organic EL display device of the first embodiment, before the first characteristic value calculation voltage setting operation (t1 to t2 in FIG. 5) and the second characteristic value calculation voltage setting operation ( Prior to t2 to t3) in FIG. 5, a predetermined voltage may be output from the source driving circuit 12 to increase the source voltage Vs of the driving transistor 11b to an expected voltage. FIG. 9 shows a timing chart when this voltage application operation is performed. In FIG. 9, the voltage Vs10 is applied to the source terminal S of the driving transistor 11b between t0 and t1 before the first characteristic value calculation voltage setting operation (t1 to t1 ′ in FIG. 9). The voltage Vs20 is applied to the source terminal S of the driving transistor 11b during t1 ′ to t2 before the characteristic value calculation voltage setting operation (t2 to t3 in FIG. 9).

By applying the voltage as described above, it is possible to shorten the time from when the first reference current or the second reference current starts to flow until the equilibrium state is reached.

  Here, the expected voltage Vs10 is converted into an analog signal by the D / A converter 12b after the characteristic value calculation voltage Vgs1 held in the first register unit 20a when it was selected by the scan drive circuit 13 last time. It can be obtained by adding a fixed voltage VB in one differential amplifier 12c. The predicted voltage Vs20 is converted into an analog signal by the D / A converter 12b after the characteristic value calculation voltage Vgs2 held in the second register unit 20b when it was selected by the scan drive circuit 13 last time. This can be obtained by adding the fixed voltage VB in the differential amplifier 12c.

  The predicted voltage calculated as described above uses Vgs1 and Vgs2 when selected by the previous scanning drive circuit 13, and thus is not necessarily accurate, but the time can be shortened.

  Next, an organic EL display device to which the second embodiment of the display device of the present invention is applied will be described.

  In the organic EL display device according to the first embodiment, the first characteristic value calculation voltage Vgs1 and the second characteristic value calculation for all the pixel circuits 11 in the pixel circuit row in the program operation period of each pixel circuit row. The memory for storing the characteristic values of all the pixel circuits 11 is not installed by measuring the voltage Vgs2 and calculating the characteristic values. However, the characteristics of the driving transistor 11b do not fluctuate instantaneously and are not necessarily limited. It is considered that there is no particular problem even if the characteristic values are not calculated and updated for every program operation for all the pixel circuits 11 in the pixel circuit row.

  Therefore, in the organic EL display device according to the second embodiment, the characteristic value is calculated and updated only for a part of the pixel circuits 11 in the pixel circuit row in one program operation period of the pixel circuit row, and one of them. For the pixel circuits other than the pixel circuit 11 in this section, the characteristic values updated in the previous program operation period are used.

  FIG. 10 shows a schematic configuration diagram of an organic EL display device according to the second embodiment.

  In the organic EL display device according to the second embodiment, as shown in FIG. 10, a characteristic value memory 17 for storing characteristic values of all the pixel circuits is further added to the control unit 16. In the organic EL display device according to the first embodiment, the operation units 12h are provided in the source drive circuit 12 by the number of pixel circuit columns (the number of data lines 14). In the organic EL display device, an R calculation unit 22 that calculates the characteristic value of the R (red) pixel circuit 11, a G calculation unit 23 that calculates the characteristic value of the G (green) pixel circuit 11, and B ( Only three calculation units including the B calculation unit 22 for calculating the characteristic value of the pixel circuit 11 of (green) are provided. Other configurations such as the pixel circuit are the same as those of the organic EL display device of the first embodiment, and therefore, different configurations will be mainly described. In the active matrix substrate 10, as shown in FIG. 10, the R pixel circuit 11 and the G pixel circuit are arranged in a direction (a direction in which the scanning line 15 extends) orthogonal to the scanning direction (a direction in which the data line 14 extends). 11 and B pixel circuits 11 are repeatedly arranged in this order.

  FIG. 12 is a detailed configuration diagram of the source drive circuit 21 of the organic EL display device according to the second embodiment. The source drive circuit 21 includes a large number of circuits shown in FIG. 3, and the circuit shown in FIG. 11 is connected to each data line 14 of the active matrix substrate 10.

  As shown in FIG. 12, the source drive circuit 21 includes a fixed voltage source 21a, a D / A converter 21b, a first differential amplifier 21c, a second differential amplifier 21d, and an A / D converter 21e. The first reference current source 21f, the second reference current source 21g, the VTH register unit 21h, the MU register unit 21i, the VGS calculation unit 21j, the input / output unit 21k, and the first switch element 12l, a second switch element 12m, and a third switch element 12n.

  Fixed voltage source 21a, D / A converter 21b, first differential amplifier 21c, second differential amplifier 21d, A / D converter 21e, first reference current source 21f, second reference current source 21g, first The first switch element 121, the second switch element 12m, and the third switch element 12n are the same as those in the organic EL display device of the first embodiment.

  The MU register unit 21 i holds the characteristic value MU calculated by the R calculation unit 22, the G calculation unit 23, and the B calculation unit 24 or the characteristic value MU read from the characteristic value memory 17.

  The VTH register unit 21h holds the characteristic value VTH calculated by the R calculating unit 22, the G calculating unit 23, and the B calculating unit 24 or the characteristic value VTH read from the characteristic value memory 17.

  The R calculation unit 22 calculates the characteristic value of the driving transistor 11b based on the differential voltage output from the second differential amplifier 21d of the source driving circuit 21, and the characteristic value is calculated by the control unit 16 and the source driving circuit 21. Is output.

  FIG. 13 shows a detailed configuration diagram of the R calculation unit 22. The R operation unit 22 includes first to fourth register units 22a to 22d, a ΔVGS calculation unit 22e, a Δ√ID calculation unit 22f, a MU calculation unit 22g, and a VTH calculation unit 22h. These are the same as those of the organic EL display device of the first embodiment.

  The configurations of the G calculation unit 23 and the B calculation unit 24 are the same as those of the R calculation unit 22.

  Next, the operation of the organic EL display device of the second embodiment will be described. The timing chart and the operation in the pixel circuit are the same as those of the organic EL display device of the first embodiment, and will be described with reference to FIGS. 5 and 6 to 8.

  First, a predetermined pixel circuit row is selected by the scanning drive circuit 13, and an on-scan signal as shown in FIG. 5 is output to the scanning line 15 to which the pixel circuit row is connected (time t1 in FIG. 5).

  As shown in FIG. 6, the selection transistor 11d and the measurement transistor 11e are turned on in response to the on-scan signal output from the scan drive circuit 13, and the gate terminal G of the drive transistor 11b and the fixed voltage VB are supplied. Are connected to the source terminal S of the driving transistor 11b, one end of the capacitive element 11c, and the anode terminal of the organic EL light emitting element 11a, and the data line 14.

  Then, similarly to the organic EL display device of the first embodiment, the setting of the first characteristic value calculation voltage, the setting of the second characteristic value calculation voltage, and the calculation of the characteristic value are performed. In the organic EL display device according to the first embodiment, the above-described operation is performed for all the pixel circuits 11 in the selected pixel circuit row. In the present embodiment, among the selected pixel circuit rows, The above operation is performed for three pixel circuits, that is, the R pixel circuit 11, the G pixel circuit 11, and the B pixel circuit 11. First, the above operation is performed on the R pixel circuit 11, the G pixel circuit 11, and the B pixel circuit 11 arranged on the leftmost of the selected pixel circuit rows.

  First, the first characteristic value calculation voltage setting operation is performed (see t1 to t2 in FIG. 5, FIGS. 6 and 7). Specifically, the second switch element 21m of the source drive circuit 21 is turned on, and the first reference current source 21f and the data line 14 are connected. As shown in FIG. 6, the first reference current source 21f The first reference current Is1 is drawn from the pixel circuit 11 toward the source drive circuit 21.

  At this time, since the current Id does not flow through the driving transistor 11b as described above, the first reference current Is becomes the discharge current of the parasitic capacitance 51 of the organic EL light emitting element 11a and the capacitive element 11c. The source voltage Vs of the transistor for transistor 11b decreases.

  When the source voltage Vs of the driving transistor 11b decreases, the gate-source voltage Vgs of the driving transistor 11b increases, and as shown in FIG. 7, a current Id begins to flow through the driving transistor 11b, and finally Id = Is1 Becomes an equilibrium state.

  Then, in the second differential amplifier 21d of the source driving circuit 21, the source voltage Vs1 of the driving transistor 11b in the equilibrium state is subtracted from the fixed voltage VB to calculate the first characteristic value calculation voltage Vgs1. . The first characteristic value calculation voltage Vgs1 is converted into a digital signal by the A / D converter 12e, and then input to the R operation unit 22 and held in the first register unit 22a of the R operation unit 22.

  Then, a second characteristic value calculation voltage setting operation is performed (see t2 to t3 in FIG. 5, FIGS. 6 and 7). Specifically, the second switch element 21m of the source drive circuit 21 is turned off and the third switch element 21n is turned on, and the second reference current source 21g and the data line 14 are connected, as shown in FIG. As described above, the second reference current Is2 of the second reference current source 21g is drawn from the pixel circuit 11 toward the source drive circuit 21.

  Here, the relationship between the second reference current Is2 and the first reference current Is1 is set to Is2 <Is1. Therefore, the source voltage Vs of the driving transistor 11b is increased by the above operation.

  When the source voltage Vs of the driving transistor 11b increases, the gate-source voltage Vgs of the driving transistor 11b decreases and finally becomes Id = Is2 and becomes an equilibrium state.

  Then, in the second differential amplifier 21d of the source drive circuit 21, the source voltage Vs2 of the drive transistor 11b in the equilibrium state is subtracted from the fixed voltage VB to calculate the second characteristic value calculation voltage Vgs2. . The second characteristic value calculation voltage Vgs2 is converted into a digital signal by the A / D converter 12e, and then input to the R calculation unit 22 and held in the second register unit 22b of the R calculation unit 22.

  Then, a characteristic value calculating operation is performed (t3 to t4 in FIG. 5). Specifically, first, the characteristic value calculation voltage Vgs1 held in the first register unit 22a and the second characteristic value calculation voltage Vgs2 held in the second register unit 22b are output to the ΔVGS calculation unit 22e. The Then, the ΔVGS calculating unit 22e calculates a differential gate-source voltage ΔVGS by subtracting Vgs2 from Vgs1.

  On the other hand, Id1 (= Is1) preset in the third register unit 22c and Id2 (= Is2) preset in the fourth register unit 22d are output to the Δ√ID calculation unit 22f. The Δ√ID calculation unit 22f calculates the current change amount Δ√ID by calculating the following equation.

Δ√ID = √Id1-√Id2
The ΔVGS calculated by the ΔVGS calculating unit 22e and the Δ√ID calculated by the Δ√ID calculating unit 22f are input to the MU calculating unit 22g, and the MU calculating unit 22g calculates the mobility by calculating the following equation. A characteristic value MU corresponding to the above is acquired.

MU = (Δ√ID) ² / (ΔVGS) ²
Further, ΔVGS, Δ√ID, Vgs1 set in the first register unit 22a, and Id1 set in the third register unit 22c are input to the VTH calculation unit 22h, and the VTH calculation unit 22h calculates the following equation: Thus, the characteristic value VTH corresponding to the threshold voltage is calculated.

VTH = -b / a
a = Δ√ID / ΔVGS
b = √Id1-a * Vgs1
The characteristic value MU and characteristic value VTH for the R pixel circuit 11 calculated as described above are output to the control unit 16 and the source drive circuit 21 of the R pixel circuit 11. Then, the control unit 16 outputs the input characteristic value MU and characteristic value VTH to the characteristic value memory 17, and rewrites and updates the characteristic value of the R pixel circuit. On the other hand, the characteristic value MU input to the source drive circuit 21 of the R pixel circuit 11 is held in the MU register unit 21i, and the characteristic value VTH is held in the VTH register unit 21h.

  In the same manner as described above, the characteristic value MU and the characteristic value VTH are also calculated in the G calculation unit 23 for the G pixel circuit 11. The characteristic value MU and the characteristic value VTH for the G pixel circuit 11 are output to the control unit 16 and the source drive circuit 21 of the G pixel circuit 11. Then, the control unit 16 outputs the input characteristic value MU and characteristic value VTH to the characteristic value memory 17, and rewrites and updates the characteristic value of the G pixel circuit. On the other hand, the characteristic value MU inputted to the source drive circuit 21 of the G pixel circuit 11 is held in the MU register unit 21i, and the characteristic value VTH is held in the VTH register unit 21h.

  Also for the B pixel circuit 11, the characteristic value MU and the characteristic value VTH are calculated by the B calculation unit 24. The characteristic value MU and characteristic value VTH for the B pixel circuit 11 are output to the control unit 16 and the source drive circuit 21 of the B pixel circuit 11. Then, the control unit 16 outputs the input characteristic value MU and characteristic value VTH to the characteristic value memory 17, and rewrites and updates the characteristic value of the B pixel circuit. On the other hand, the characteristic value MU inputted to the source drive circuit 21 of the B pixel circuit 11 is held in the MU register unit 21i, and the characteristic value VTH is held in the VTH register unit 21h.

  For the pixel circuits 11 other than the three R, G, and B pixel circuits whose characteristic values are calculated as described above, the control unit 16 sets the characteristic value MU corresponding to each pixel circuit 11 from the characteristic value memory 17. The characteristic value VTH is read and input to the source drive circuit 21 of each pixel circuit 11. The characteristic value MU input to the source drive circuit 21 of each pixel circuit 11 is held in the MU register unit 21i, and the characteristic value VTH is held in the VTH register unit 21h.

  Then, a display gate-source voltage setting operation is performed (t5 to t6 in FIG. 5). The display gate-source voltage setting operation is performed for all the pixel circuits 11 in the selected pixel circuit row.

  Specifically, the display data output from the control unit 16, the characteristic value MU held in the MU register unit 21i, and the characteristic value VTH held in the VTH register unit 21h are input to the VGS calculation unit 21j. The Then, the VGS calculation unit 21j calculates the display gate-source voltage Vgsn based on the display data, the characteristic value MU, and the characteristic value VTH.

  Then, Vgsn calculated by the VGS calculating unit 21j is input to the D / A converter 21b, converted into an analog signal, and then input to the inverting input terminal of the first differential amplifier 21c. Then, in the first differential amplifier 21c, the fixed voltage VB is added and converted to Vsn. Then, the third switch element 21n is turned OFF, the first switch element 121 is turned ON, and Vsn is output to the data line 14.

  With the operation as described above, the gate voltage Vg = VB, the source voltage Vs = Vsn, and Vgs = Vgsn are set in the driving transistor 11b.

  Next, a light emission operation is performed (see FIG. 8 after t7 in FIG. 5). Specifically, an off-scan signal is output from the scan drive circuit 13 to each scan line 15 (time t7 in FIG. 5). As shown in FIG. 8, the selection transistor 11d and the measurement transistor 11e are turned off in response to the off-scan signal output from the scan drive circuit 13, and the gate terminal G and the fixed voltage VB of the drive transistor 11b are supplied. As a result, the source terminal S of the driving transistor 11b, one end of the capacitive element 11c, the anode terminal of the organic EL light emitting element 11a, and the data line 14 are disconnected.

  The gate-source voltage Vgs of the driving transistor 11b becomes Vgsn, and the driving current Idn flows between the drain and source of the driving transistor 11b.

  The drive current Idn charges the parasitic capacitance 51 of the organic EL light emitting element 11a, and the source voltage Vs of the drive transistor 11b rises, but the gate-source voltage Vgsn is held by the holding voltage Vgsn of the capacitance element 11c. Accordingly, the source voltage Vs eventually exceeds the light emission threshold voltage Vf0 of the organic EL light emitting element 11a, and the light emitting operation of the organic EL light emitting element 11a is performed with a constant current.

  Then, a predetermined pixel circuit row is sequentially selected up to the last row by the scanning drive circuit 13, and the operation from the first characteristic value calculation voltage setting operation to the light emission operation is performed for each pixel circuit row. A display image is displayed.

  When the display image of the second frame is displayed next, a predetermined pixel circuit row is sequentially selected by the scanning drive circuit 13, and light emission from the first characteristic value calculation voltage setting operation is performed for each pixel circuit row. The operation up to the operation is performed. At this time, the pixel circuit for which the characteristic value is calculated changes.

  Specifically, when displaying the display image of the first frame, characteristic values are calculated for the R, G, and B pixel circuits arranged on the leftmost of the selected pixel circuit rows, and the characteristic values are calculated. Although the characteristic value of the memory 17 is updated, when displaying the display image of the second frame, the R, G, and B pixel circuits that are characteristic value calculation targets when the display image of the first frame is displayed R, G, and B pixel circuits adjacent to the right side are selected as characteristic value calculation target pixel circuits.

  Further, when the display image of the third frame is displayed, R, G, B adjacent to the right side of the R, G, B pixel circuit of the characteristic value calculation target when the display image of the second frame is displayed. Is selected as a pixel circuit for which a characteristic value is to be calculated.

  As described above, every time the frame changes, the R, G, and B pixel circuits for which characteristic values are to be calculated are sequentially shifted to the right. As a result, the characteristic values of the characteristic value memory 17 are updated for all the pixel circuits when the number of frames corresponding to the total number of pixel circuits / 3 of the pixel circuit row is displayed. For example, in the case of a VGA having a frame rate of 60 Hz and a display pixel number (here, three pixel circuits of R, G, and B are one display pixel) of 640 × 480, the characteristic value update rate is 640 frames = This is 10.7 seconds, which is sufficient when compared with the fluctuation speed of the characteristics of the driving transistor.

  In the display device according to the second embodiment, the pixel circuit columns for which the characteristic values are calculated are sequentially switched for each frame. However, the pixel circuit rows for which the characteristic values are calculated are changed for each frame. You may make it switch sequentially.

  A schematic configuration in this case is shown in FIG. As shown in FIG. 14, the configuration of the calculation unit is different from that of the second embodiment. Specifically, in the second embodiment, only three calculation units, that is, an R calculation unit, a G calculation unit, and a B calculation unit are provided. However, a pixel circuit row for which a characteristic value is to be calculated is provided. In the case of switching sequentially for each frame, the calculation unit 26 having the configuration shown in FIG. 13 is provided for each pixel circuit column (data line 14). Other configurations are the same as those in the second embodiment.

  The operation of the organic EL display device shown in FIG. 14 will be described. The timing chart and the operation in the pixel circuit are the same as those of the organic EL display device of the first embodiment, and will be described with reference to FIGS. 5 and 6 to 8.

  First, the first pixel circuit row (the uppermost pixel circuit row shown in FIG. 14) is selected by the scanning drive circuit 13, and the scanning line 15 to which the pixel circuit row is connected is connected to the scanning line 15 as shown in FIG. An on-scan signal is output (time t1 in FIG. 5).

  As shown in FIG. 6, the selection transistor 11d and the measurement transistor 11e are turned on in response to the on-scan signal output from the scan drive circuit 13, and the gate terminal G of the drive transistor 11b and the fixed voltage VB are supplied. Are connected to the source terminal S of the driving transistor 11b, one end of the capacitive element 11c, and the anode terminal of the organic EL light emitting element 11a, and the data line 14.

  Then, similarly to the organic EL display device of the second embodiment, the first characteristic value calculation voltage, the second characteristic value calculation voltage, and the characteristic value are calculated. In the organic EL display device shown in FIG. 14, the above operation is performed for one pixel circuit row among the pixel circuit rows from the first row to the last row. First, the above operation is performed for each pixel circuit in the first pixel circuit row (the uppermost pixel circuit row shown in FIG. 14). The details of the operation are the same as in the second embodiment.

  Then, the characteristic value MU and the characteristic value VTH are calculated for each pixel circuit in the first pixel circuit row, and the characteristic value MU and the characteristic value VTH of each pixel circuit are transmitted to the control unit 16 and the source drive circuit 21. Is output. Then, the control unit 16 outputs the input characteristic value MU and characteristic value VTH to the characteristic value memory 17, and rewrites and updates the characteristic value of each pixel circuit in the first pixel circuit row. On the other hand, the characteristic value MU input to the source drive circuit 21 is held in the MU register unit 21i, and the characteristic value VTH is held in the VTH register unit 21h.

  Then, the display gate-source voltage setting operation and the light emission operation are performed for the first pixel circuit row. These operations are the same as those in the second embodiment.

  Then, the second pixel circuit row (second pixel circuit row from the top in FIG. 14) is selected by the scanning drive circuit 13, and the scanning circuit 15 to which the pixel circuit row is connected is connected to the scanning line 15 shown in FIG. An on-scan signal as shown is output.

  As shown in FIG. 6, the selection transistor 11d and the measurement transistor 11e are turned on in response to the on-scan signal output from the scan drive circuit 13, and the gate terminal G of the drive transistor 11b and the fixed voltage VB are supplied. Are connected to the source terminal S of the driving transistor 11b, one end of the capacitive element 11c, and the anode terminal of the organic EL light emitting element 11a, and the data line 14.

  For the second pixel circuit row, the setting of the first characteristic value calculation voltage, the setting of the second characteristic value calculation voltage, and the calculation of the characteristic value are not performed. That is, the characteristic value in the characteristic value memory 17 is not updated for each pixel circuit in the second pixel circuit row. Then, the characteristic value MU and the characteristic value VTH stored in the characteristic value memory 17 when the characteristic value calculation object is selected last time are read out, and the MU register unit 21i and the VTH register unit of the source drive circuit 21 are read. 21h.

  Then, the display gate-source voltage setting operation and the light emission operation are performed for the second pixel circuit row. These operations are the same as those of the first pixel circuit row.

  Then, the pixel circuit rows from the third row to the last row are sequentially selected by the scan driving circuit 13, and the same operation as the second pixel circuit row described above is performed, and the display image of the first frame is displayed.

  Then, when the display image of the second frame is displayed next, the pixel circuit row whose characteristic value is to be calculated is switched from the first pixel circuit row to the second pixel circuit row. That is, for the first pixel circuit row, the same operation as the second and subsequent pixel circuit rows during the display operation of the display image of the first frame described above is performed, and for the second pixel circuit row, The same operation as that of the first pixel circuit row in the display operation of the display image of the first frame described above is performed.

  When the display image of the third frame is further displayed, the pixel circuit row whose characteristic value is to be calculated is switched from the second pixel circuit row to the third pixel circuit row. That is, for the first and second pixel circuit rows, the same operation as the second and subsequent pixel circuit rows during the display operation of the display image of the first frame described above is performed, and the third pixel circuit row is performed. For the row, the same operation as the first pixel circuit row during the display operation of the display image of the first frame described above is performed.

As described above, every time the frame changes, the pixel circuit rows for which characteristic values are to be calculated are sequentially shifted. Thus, the characteristic values of the characteristic value memory 17 are updated for all the pixel circuits when the number of frames corresponding to the number of pixel circuit rows is displayed. For example, in the case of a VGA having a frame rate of 60 Hz and a display pixel number (here, three pixel circuits of R, G, and B are set as one display pixel) of 640 × 480, the characteristic value update rate is 480 frames = This is 8 seconds, which is sufficient when compared with the fluctuation speed of the characteristics of the driving transistor.

  As described above, a part of the pixel circuit rows of the pixel circuit rows from the first row to the last row are sequentially switched and selected for each frame, and the characteristic value is acquired for the selected selected pixel circuit row. For example, even when the scanning time of all pixel circuit rows such as a high-definition panel is short, it is possible to secure time for acquiring characteristic values for some pixel circuit rows, and to set pixel circuit rows for acquiring characteristic values. By switching every frame, characteristic values for all pixel circuit rows can be acquired.

  Here, in the organic EL display devices of the first and second embodiments, it is necessary to use an N-type thin film transistor as a driving transistor as described above, and an amorphous silicon thin film transistor is used as the N-type thin film transistor. I can.

  However, an amorphous silicon thin film transistor has a feature that its threshold voltage shifts due to voltage stress caused by application of a gate voltage.

  In the organic EL display devices of the first and second embodiments, the current value flowing through the driving transistor 11b is detected by changing the source voltage with the gate voltage Vg of the driving transistor 11b as the fixed voltage VB. When the threshold voltage shift of the driving transistor 11b is large, the source voltage set when detecting the current value becomes a lower voltage. For this reason, a large negative power supply voltage in anticipation of a long-term threshold voltage shift is required. Therefore, it is desirable to suppress the shift of the threshold voltage of the driving transistor 11b from the viewpoint of power saving.

  For example, Japanese Patent Laying-Open No. 2006-227237 (hereinafter referred to as Patent Document 7) proposes a method of suppressing a shift in threshold voltage by applying a reverse bias voltage to the gate terminal of a driving transistor.

  However, the magnitude of the gate voltage applied to the gate terminal of the driving transistor during the display operation depends on the display image, and the shift amount of the threshold voltage of the driving transistor changes depending on the magnitude of the gate voltage. On the other hand, the period of reverse bias and the magnitude of the reverse bias voltage performed in Patent Document 7 are common to all pixels, so that the threshold voltage deviation of each driving transistor and the change in threshold voltage shift amount due to the display image are changed. Can not cope with. When the threshold voltage of the driving transistor starts to shift due to insufficient reverse bias, the threshold voltage is accelerated. That is, with the method described in Patent Document 7, it is difficult to suppress the shift of the threshold voltage of the driving transistor when the display image is updated over a long period of time.

  Next, an organic EL display device to which the third embodiment of the display device of the present invention that can appropriately suppress the shift of the threshold voltage of the driving transistor as described above will be described. In the organic EL display device according to the third embodiment, a reverse bias voltage corresponding to a display image is further applied to the driving transistor 11b in the organic EL display device according to the first embodiment.

  FIG. 15 shows a configuration of a pixel circuit of the organic EL display device according to the third embodiment. As shown in FIG. 15, a common electrode line 18 is connected to the cathode terminal of the organic EL light emitting element 11a of the pixel circuit of the organic EL display device of the third embodiment. Other pixel circuits have the same configuration as that of the first organic EL display device.

  As shown in FIG. 16, the source drive circuit 25 of the organic EL display device of the third embodiment includes a fixed voltage source 25a, a D / A converter 25b, a first differential amplifier 25c, and a second difference. The dynamic amplifier 25d, the A / D converter 25e, the first reference current source 25f, the second reference current source 25g, the arithmetic unit 25h, the first switch element 25i, and the second switch element 25j , A third switch element 25k, a fourth switch element 25l, an amplifier 25m, and a third differential amplifier 25n.

  Fixed voltage source 25a, D / A converter 25b, first differential amplifier 25c, second differential amplifier 25d, A / D converter 25e, first reference current source 25f, second reference current source 25g, calculation The unit 25h, the first switch element 25i, the second switch element 25j, and the third switch element 25k are the same as those in the organic EL display device of the first embodiment.

  The amplifier 25m outputs the display gate-source voltage Vgsn calculated by the VGS calculation unit 20i of the calculation unit 25h by multiplying it by Kr.

  The third differential amplifier 25n calculates the reverse bias voltage Vrv by adding VB to Kr × Vgsn output from the amplifier 25m, and outputs the reverse bias voltage to the data line 14.

  The fourth switch element 251 switches the connection between the third differential amplifier 25n and the data line 14 in accordance with a timing signal based on the synchronization signal output from the control unit 16.

  Other configurations are the same as those of the organic EL display device of the first embodiment.

  Next, the operation of the organic EL display device of the third embodiment will be described with reference to the timing chart shown in FIG. In FIG. 17, the scanning signal Vscan output from the scanning driving circuit 13, the data signal Vdata output from the source driving circuit 12, the gate voltage Vg of the driving transistor 11b, the source voltage Vs, and the gate-source voltage Vgs are shown. The voltage waveform is shown.

  As shown in the timing chart of FIG. 17, in the organic EL display device of the third embodiment, the characteristic value calculation operation (t3 to t4 in FIG. 17) and the display gate-source voltage setting operation (t5 in FIG. 17). To t6), a reverse bias voltage application operation (t4 to t5 in FIG. 17) is performed. Since other operations are the same as those of the organic EL display device of the first embodiment, only the reverse bias voltage application operation will be described.

  Specifically, the reverse bias voltage application operation is calculated by the display data output from the control unit 16, the characteristic value MU calculated by the MU calculation unit 20g, and the VTH calculation unit 20h after the characteristic value calculation operation. The characteristic value VTH is input to the VGS calculation unit 20i, and the VGS calculation unit 20i calculates the display gate-source voltage Vgsn based on the display data, the characteristic value MU, and the characteristic value VTH.

  Then, Vgsn calculated by the VGS calculating unit 20i is input to the D / A converter 25b, converted into an analog signal by the D / A converter 25b, and then input to the amplifier 25m. In the amplifier 25m, Vgsn is multiplied by Kr, and Kr × Vgsn is input to the inverting input terminal of the third differential amplifier 25n. Then, in the third differential amplifier 25n, the fixed voltage VB is added to Kr × Vgsn to calculate the reverse bias voltage Vrv represented by the following equation.

Vrv = K × Vgsn + VB
Then, the fourth switch element 25l is turned on, and the reverse bias voltage Vrv is output from the third differential amplifier 25n to the data line 14 and applied to the source terminal S of the driving transistor 11b of the pixel circuit 11. This means that a voltage -Kr times the positive bias Vgsn set in the light emission operation is applied between the gate and the source of the driving transistor 11b, and the effect of suppressing the threshold voltage shift can be greatly improved.

  In the reverse bias voltage application period, the potential of the common electrode line 18 connected to the cathode terminal of the organic EL light emitting element 11a of the pixel circuit is changed from 0 V to a high potential (for example, Vdd). Thereby, it is possible to prevent the organic EL light emitting element 11a from emitting light erroneously by applying the reverse bias voltage Vrv to the source terminal S of the driving transistor 11b (the anode terminal of the organic EL light emitting element 11a).

  Here, the reverse bias voltage in the organic EL display device of the third embodiment will be considered.

In the organic EL display device of the third embodiment, the voltage stress of the driving transistor 11b due to the display operation is Vgs × Tdsp. Tdsp is a display period. When the reverse bias voltage application period is Trv, the necessary reverse bias voltage Vrv is
Vrv = Vgs × Tdsp / Trv
It becomes. By applying this reverse bias voltage, the voltage stress on the average of one frame is equalized between positive and negative and becomes zero.

That is, the reverse bias coefficient Kr set in the amplifier 25m in the organic EL display device of the third embodiment is
Kr = Tdsp / Trv
However, the reverse bias period Trv is a part of the program period Tprg and is naturally much shorter than the display period Tdsp. Therefore, the reverse bias coefficient Kr increases and the reverse bias voltage Vrv also becomes a high voltage.

  However, the maximum voltage that can be set as the reverse bias voltage Vrv is the power supply voltage Vdd. When high brightness display is performed, the voltage stress cannot be offset by the reverse bias voltage, and the reverse bias voltage may be insufficient. .

  Therefore, in order to solve this problem, the driving transistor 11b may be formed of a thin film transistor having a current characteristic of the threshold voltage Vth <0. FIG. 18 shows an example of the current characteristics of the driving transistor with the threshold voltage Vth <0.

  When the threshold voltage Vth of the driving transistor 11b is set to a negative voltage, a positive and negative voltage is applied as Vgs in the display operation, so that the reverse bias voltage also has both a positive and negative polarity. Thus, the shortage of reverse bias due to the limit value of the reverse bias voltage can be reduced.

  In the organic EL display devices of the first to third embodiments, the threshold voltage of the driving transistor 11b can perform the characteristic value calculation and the Vgsn setting operation regardless of whether the threshold voltage is positive or negative. By making the voltage negative, the reverse bias voltage setting range can be expanded and long-term stability can be improved.

  In the organic EL display devices of the first to third embodiments, an N-type thin film transistor made of amorphous silicon or an inorganic oxide film can be used as a driving transistor as described above. It is desirable to use an N-type thin film transistor as a driving transistor.

  By utilizing the reversible threshold voltage shift characteristic of a thin film transistor made of IGZO, for example, the threshold voltage can be returned to the initial value during a non-display period such as a period when a black screen is displayed or when the power is turned off. The shift of the threshold voltage can be further suppressed. Also, the negative voltage of the threshold voltage of the driving transistor 11b can be easily realized.

  In the organic EL display devices of the first to third embodiments, the second differential amplifier of the analog circuit is used as means for calculating the first and second characteristic value calculation voltages Vgs1, Vgs2. However, the present invention is not limited to this, and it may be calculated by digital calculation. In addition, as the means for calculating the display source voltage Vsn, the first differential amplifier of the analog circuit is used. However, it may be calculated by digital calculation. Further, if the fixed voltage VB = 0 V, it is possible to prevent the above calculation from being performed.

  In the organic EL display devices according to the first to third embodiments, the MU calculator, the VTH calculator, and the VGS calculator are provided to calculate MU, VTH, and Vgsn by digital calculation. These embodiments are not limited to this, and may be replaced by a DSP, a CPU, or the like.

  In addition, the calculation unit that calculates the characteristic values in the organic EL display devices of the first to third embodiments may be installed in the source drive circuit, may be an independent configuration, or may be in the control unit 16. You may make it install in.

  In the organic EL display devices according to the first to third embodiments, the first reference current source 12f for supplying the first reference current Is1 and the second reference current source 12g for supplying the second reference current Is2 are used. However, it is also possible to provide one variable current source and switch the first reference current Is1 and the second reference current Is2 using this variable current source. .

  In the embodiment of the present invention, the display device of the present invention is applied to an organic EL display device. However, the light emitting element is not limited to the organic EL light emitting element, and for example, an inorganic EL element is used. It may be.

  The display device of the present invention has various uses. For example, a portable information terminal (electronic notebook, mobile computer, mobile phone, etc.), a video camera, a digital camera, a personal computer, a television, etc. are mentioned.

1 is a schematic configuration diagram of an organic EL display device to which a first embodiment of a display device of the present invention is applied. The figure which shows the structure of the pixel circuit of the organic electroluminescence display to which 1st Embodiment of the display apparatus of this invention is applied. The figure which shows the structure of the source drive circuit of the organic electroluminescent display apparatus to which 1st Embodiment of the display apparatus of this invention is applied. The figure which shows the detailed structure of the calculating part shown in FIG. The timing chart for demonstrating the effect | action of the organic electroluminescence display to which 1st Embodiment of the display apparatus of this invention is applied. The figure for demonstrating the effect | action of the voltage setting operation | movement for the characteristic value calculation of the organic electroluminescence display of the 1st Embodiment of this invention. The figure for demonstrating the effect | action of the voltage setting operation | movement for the characteristic value calculation of the organic electroluminescence display of the 1st Embodiment of this invention. The figure for demonstrating the light emission operation | movement of the organic electroluminescence display of the 1st Embodiment of this invention. The timing chart for demonstrating an effect | action in the case of supplying an expected voltage in the organic electroluminescent display apparatus to which 1st Embodiment of the display apparatus of this invention is applied. Schematic configuration diagram of an organic EL display device to which a second embodiment of the display device of the present invention is applied The figure which shows arrangement | positioning of the pixel circuit of R, G, B of the organic electroluminescent display apparatus to which 2nd Embodiment of the display apparatus of this invention is applied. The figure which shows the structure of the source drive circuit of the organic electroluminescent display apparatus to which 2nd Embodiment of the display apparatus of this invention is applied. The figure which shows the structure of R calculating part of the organic electroluminescent display apparatus to which 2nd Embodiment of the display apparatus of this invention is applied. Schematic configuration diagram of an organic EL display device in a case where a pixel circuit row for characteristic value calculation is switched for each frame The figure which shows the structure of the pixel circuit of the organic electroluminescent display apparatus to which 3rd Embodiment of the display apparatus of this invention is applied. The figure which shows the structure of the source drive circuit of the organic electroluminescent display apparatus to which 3rd Embodiment of the display apparatus of this invention is applied. Timing chart for explaining the operation of the organic EL display device to which the third embodiment of the display device of the present invention is applied The figure which shows an example of the current characteristic of the drive transistor whose threshold voltage Vth is a negative voltage

Explanation of symbols

10 active matrix substrate 11 pixel circuit 11a light emitting element 11b driving transistor 11c capacitive element 11d selecting transistor 11e measuring transistor 12 source driving circuit 12a fixed voltage source 12b D / D converter 12c first differential amplifier 12d second difference Dynamic amplifier 12e A / d converter 12f First reference current source 12g Second reference current source 12h arithmetic unit 13 scan drive circuit 14 data line 15 scan line 16 control unit 17 characteristic value memory 18 common electrode line 20e ΔVGS calculation unit 20f Δ√ID calculator 20g MU calculator 20h VTH calculator 20i VGS calculator 21 Source drive circuit 21a Fixed voltage source 21b D / A converter 21c First differential amplifier 21d Second differential amplifier 21e A / D converter 21f First reference current source 21g second base Quasi-current source 21h VTH register unit 21i MU register unit 21j VGS calculation unit 22 R calculation unit 22e ΔVGS calculation unit 22f Δ√ID calculation unit 22g MU calculation unit 22h VTH calculation unit 23 G calculation unit 24 B calculation unit 25 Source drive Circuit 25a fixed voltage source 25b D / A converter 25c first differential amplifier 25d second differential amplifier 25e A / D converter 25f first reference current source 25g second reference current source 25h arithmetic unit 25m amplifier 25n first 3 differential amplifier 26 arithmetic unit 50 light emitting unit 51 parasitic capacitance

Claims (12)

A light emitting element, a driving transistor in which a source terminal is connected to an anode terminal of the light emitting element, and a driving current flows to the light emitting element, a capacitive element connected between a gate terminal and a source terminal of the driving transistor, and the driving A gate connection switch connected between the gate terminal of the transistor for driving and a voltage source for supplying a predetermined voltage, and a source connected between the source terminal of the driving transistor and a data line for supplying a predetermined signal A drive control method for a display device including an active matrix substrate in which a large number of pixel circuits having connection switches are arranged,
First preset first reference current flows from the source terminal of the driving transistor toward the data line through the source connection switch,
The first characteristic value calculation voltage is obtained based on the voltage of the source terminal of the driving transistor and the predetermined voltage in an equilibrium state in which the first reference current and the current flowing through the driving transistor are equal. And
A preset second reference current is allowed to flow from the source terminal of the driving transistor toward the data line via the source connection switch;
The second characteristic value calculation voltage is obtained based on the voltage of the source terminal of the driving transistor and the predetermined voltage in an equilibrium state where the second reference current and the current flowing through the driving transistor are equal. And
A characteristic according to a threshold voltage of the driving transistor based on the first reference current value, the second reference current value, the first characteristic value calculation voltage, and the second characteristic value calculation voltage Get characteristic value according to value and mobility,
A data signal based on the acquired characteristic value and the driving voltage of the driving transistor corresponding to the light emission amount of the light emitting element is output to the source terminal of the driving transistor via the data line and the source connection switch. A drive control method for a display device. A light emitting element, a driving transistor in which a source terminal is connected to an anode terminal of the light emitting element, and a driving current flows to the light emitting element, a capacitive element connected between a gate terminal and a source terminal of the driving transistor, and the driving A gate connection switch connected between the gate terminal of the transistor for driving and a voltage source for supplying a predetermined voltage, and a source connected between the source terminal of the driving transistor and a data line for supplying a predetermined signal An active matrix substrate having a plurality of pixel circuits each having a connection switch and having a data line provided for each column of the pixel circuits, and a row of the pixel circuits are sequentially selected, and source connection of the pixel circuits in the selected row By repeatedly selecting a pixel circuit row from the first row to the last row by the scan drive unit that turns on the switch and the scan drive unit. A drive control method of a display device and a control unit for displaying an image based on the data signals of each frame Te,
A part of the pixel circuits in the row selected by the scan driver is sequentially switched and selected for each frame,
For the selected pixel circuit, a first reference current set in advance is passed from the source terminal of the driving transistor toward the data line via the source connection switch, and the first reference current and the The first characteristic value calculation voltage is acquired based on the voltage of the source terminal of the driving transistor and the predetermined voltage in an equilibrium state in which the current flowing through the driving transistor becomes equal, and the first characteristic value calculation voltage is set in advance. In a balanced state in which two reference currents are caused to flow from the source terminal of the driving transistor toward the data line via the source connection switch, and the second reference current and the current flowing through the driving transistor are equal. Obtaining a second characteristic value calculation voltage based on the voltage of the source terminal of the driving transistor and the predetermined voltage;
A characteristic according to a threshold voltage of the driving transistor based on the first reference current value, the second reference current value, the first characteristic value calculation voltage, and the second characteristic value calculation voltage A characteristic value corresponding to the value and mobility is acquired, and a data signal based on the acquired characteristic value and a driving voltage of the driving transistor corresponding to the light emission amount of the light emitting element is transmitted to the data line and the source connection switch. Output to the source terminal of the driving transistor through, and store the acquired characteristic value in the characteristic value storage unit,
For the non-selected pixel circuits of the pixel circuits in the row selected by the scan driving unit, the characteristic value stored in the characteristic value storage unit at the previous selection and the light emission amount of the light emitting element And outputting a data signal based on the driving voltage of the driving transistor to the source terminal of the driving transistor of the non-selected pixel circuit. A light emitting element, a driving transistor in which a source terminal is connected to an anode terminal of the light emitting element, and a driving current flows to the light emitting element, a capacitive element connected between a gate terminal and a source terminal of the driving transistor, and the driving A gate connection switch connected between the gate terminal of the transistor for driving and a voltage source for supplying a predetermined voltage, and a source connected between the source terminal of the driving transistor and a data line for supplying a predetermined signal An active matrix substrate having a plurality of pixel circuits each having a connection switch and having a data line provided for each column of the pixel circuits, and a row of the pixel circuits are sequentially selected, and source connection of the pixel circuits in the selected row By repeatedly selecting a pixel circuit row from the first row to the last row by the scan drive unit that turns on the switch and the scan drive unit. A drive control method of a display device and a control unit for displaying an image based on the data signals of each frame Te,
A part of the pixel circuit rows from the first row to the last row are sequentially switched and selected for each frame,
For the selected selected pixel circuit row, a preset first reference current is caused to flow from the source terminal of the driving transistor toward the data line via the source connection switch, and the first reference current and The first characteristic value calculation voltage is acquired based on the voltage of the source terminal of the driving transistor and the predetermined voltage in an equilibrium state in which the current flowing through the driving transistor becomes equal, and is set in advance. A balanced state in which the second reference current is caused to flow from the source terminal of the driving transistor toward the data line via the source connection switch, and the second reference current and the current flowing through the driving transistor are equal. Obtaining a second characteristic value calculation voltage based on the voltage of the source terminal of the driving transistor and the predetermined voltage in
A characteristic according to a threshold voltage of the driving transistor based on the first reference current value, the second reference current value, the first characteristic value calculation voltage, and the second characteristic value calculation voltage A characteristic value corresponding to the value and mobility is acquired, and a data signal based on the acquired characteristic value and a driving voltage of the driving transistor corresponding to the light emission amount of the light emitting element is transmitted to the data line and the source connection switch. Output to the source terminal of the driving transistor through, and store the acquired characteristic value in the characteristic value storage unit,
For the non-selected pixel circuit rows that are not selected other than the part of the pixel circuit rows, the driving transistor according to the characteristic value stored in the characteristic value storage unit at the previous selection and the light emission amount of the light emitting element And outputting a data signal based on the driving voltage to the source terminal of the driving transistor in the non-selected pixel circuit row. A light emitting element, a driving transistor in which a source terminal is connected to an anode terminal of the light emitting element, and a driving current flows to the light emitting element, a capacitive element connected between a gate terminal and a source terminal of the driving transistor, and the driving A gate connection switch connected between the gate terminal of the transistor for driving and a voltage source for supplying a predetermined voltage, and a source connected between the source terminal of the driving transistor and a data line for supplying a predetermined signal An active matrix substrate having a plurality of pixel circuits having connection switches and data lines provided for each column of the pixel circuits;
A preset first reference current flows from the source terminal of the driving transistor toward the data line via the source connection switch, and the first reference current and the current flowing through the driving transistor are equal. The first characteristic value calculation voltage is acquired based on the voltage of the source terminal of the driving transistor in the balanced state and the predetermined voltage, and the second reference current set in advance is used as the driving transistor. The voltage at the source terminal of the driving transistor in an equilibrium state in which the second reference current and the current flowing through the driving transistor are equal to each other and flow from the source terminal to the data line via the source connection switch. And a characteristic value calculation voltage acquisition unit for acquiring a second characteristic value calculation voltage based on the predetermined voltage and the first voltage Based on the current value, the second reference current value, the first characteristic value calculation voltage, and the second characteristic value calculation voltage, the characteristic value and mobility according to the threshold voltage of the driving transistor are obtained. A characteristic value acquisition unit for acquiring a corresponding characteristic value, and a data signal based on the characteristic value acquired by the characteristic value acquisition unit and a driving voltage of the driving transistor according to a light emission amount of the light emitting element. And a source driving circuit having a data signal output section for outputting to the source terminal of the driving transistor via the source connection switch. A light emitting element, a driving transistor in which a source terminal is connected to an anode terminal of the light emitting element, and a driving current flows to the light emitting element, a capacitive element connected between a gate terminal and a source terminal of the driving transistor, and the driving A gate connection switch connected between the gate terminal of the transistor for driving and a voltage source for supplying a predetermined voltage, and a source connected between the source terminal of the driving transistor and a data line for supplying a predetermined signal An active matrix substrate having a plurality of pixel circuits having connection switches and data lines provided for each column of the pixel circuits;
A scan driver that sequentially selects rows of the pixel circuits and turns on a source connection switch of the pixel circuits of the selected rows;
A preset first reference current flows from the source terminal of the driving transistor toward the data line via the source connection switch, and the first reference current and the current flowing through the driving transistor are equal. The first characteristic value calculation voltage is acquired based on the voltage of the source terminal of the driving transistor in the balanced state and the predetermined voltage, and the second reference current set in advance is used as the driving transistor. The voltage at the source terminal of the driving transistor in an equilibrium state in which the second reference current and the current flowing through the driving transistor are equal to each other and flow from the source terminal to the data line via the source connection switch. And a characteristic value calculation voltage acquisition unit for acquiring a second characteristic value calculation voltage based on the predetermined voltage and the first voltage Based on the current value, the second reference current value, the first characteristic value calculation voltage, and the second characteristic value calculation voltage, the characteristic value and mobility according to the threshold voltage of the driving transistor are obtained. A characteristic value acquisition unit for acquiring a corresponding characteristic value, and a data signal based on the characteristic value acquired by the characteristic value acquisition unit and a driving voltage of the driving transistor according to a light emission amount of the light emitting element. And a source driver having a data signal output unit for outputting to the source terminal of the driving transistor via the source connection switch,
A characteristic value storage unit for storing the characteristic values of the driving transistors of all the pixel circuits;
A controller that displays an image based on the data signal for each frame by repeatedly selecting a row of pixel circuits from the first row to the last row by the scan driver;
The characteristic value calculation voltage acquisition unit sequentially switches and selects some of the pixel circuits in the row selected by the scan driver for each frame, and the first pixel circuit is selected for the selected pixel circuit. And obtaining the second characteristic value calculation voltage and the second characteristic value calculation voltage,
The characteristic value acquisition unit acquires the characteristic value for the pixel circuit selected by the characteristic value calculation voltage acquisition unit, outputs the acquired characteristic value to the characteristic value storage unit, and stores the characteristic value in the characteristic value storage unit. Updating previously stored characteristic values for the selected pixel circuit;
For the selected pixel circuit selected by the characteristic value calculation voltage acquisition unit by the data signal output unit, the characteristic value acquired by the characteristic value acquisition unit at the time of selection and the light emission amount of the light emitting element A data signal based on the driving voltage of the driving transistor is output to the source terminal of the driving transistor of the selected pixel circuit, and the non-selected pixel circuit that is not selected by the characteristic value calculation voltage acquisition unit A data signal based on the characteristic value stored at the time of previous selection in the value storage unit and the driving voltage of the driving transistor according to the light emission amount of the light emitting element is supplied to the source terminal of the driving transistor of the non-selected pixel circuit. A display device characterized by output. A light emitting element, a driving transistor in which a source terminal is connected to an anode terminal of the light emitting element, and a driving current flows to the light emitting element, a capacitive element connected between a gate terminal and a source terminal of the driving transistor, and the driving A gate connection switch connected between the gate terminal of the transistor for driving and a voltage source for supplying a predetermined voltage, and a source connected between the source terminal of the driving transistor and a data line for supplying a predetermined signal An active matrix substrate having a plurality of pixel circuits having connection switches and data lines provided for each column of the pixel circuits;
A scan driver that sequentially selects rows of the pixel circuits and turns on a source connection switch of the pixel circuits of the selected rows;
A preset first reference current flows from the source terminal of the driving transistor toward the data line via the source connection switch, and the first reference current and the current flowing through the driving transistor are equal. The first characteristic value calculation voltage is acquired based on the voltage of the source terminal of the driving transistor in the balanced state and the predetermined voltage, and the second reference current set in advance is used as the driving transistor. The voltage at the source terminal of the driving transistor in an equilibrium state in which the second reference current and the current flowing through the driving transistor are equal to each other and flow from the source terminal to the data line via the source connection switch. And a characteristic value calculation voltage acquisition unit for acquiring a second characteristic value calculation voltage based on the predetermined voltage and the first voltage Based on the current value, the second reference current value, the first characteristic value calculation voltage, and the second characteristic value calculation voltage, the characteristic value and mobility according to the threshold voltage of the driving transistor are obtained. A characteristic value acquisition unit for acquiring a corresponding characteristic value, and a data signal based on the characteristic value acquired by the characteristic value acquisition unit and a driving voltage of the driving transistor according to a light emission amount of the light emitting element. And a source driver having a data signal output unit for outputting to the source terminal of the driving transistor via the source connection switch,
A characteristic value storage unit for storing the characteristic values of the driving transistors of all the pixel circuits;
A controller that displays an image based on the data signal for each frame by repeatedly selecting a row of pixel circuits from the first row to the last row by the scan driver;
The characteristic value calculating voltage acquisition unit sequentially switches and selects a part of the pixel circuit rows from the first row to the last row for each frame, and the selected pixel circuit row Obtaining the first characteristic value calculation voltage and the second characteristic value calculation voltage;
The characteristic value acquisition unit acquires the characteristic value for the pixel circuit row selected by the characteristic value calculation voltage acquisition unit, and outputs the acquired characteristic value to the characteristic value storage unit to output the characteristic value storage unit. Updating the characteristic value for the selected pixel circuit row previously stored in
For the selected pixel circuit row selected by the characteristic value calculation voltage acquisition unit, the data signal output unit corresponds to the characteristic value acquired by the characteristic value acquisition unit at the time of selection and the light emission amount of the light emitting element. A data signal based on the driving voltage of the driving transistor is output to the source terminal of the driving transistor of the selected pixel circuit row, and the non-selected pixel circuit row that is not selected by the characteristic value calculation voltage acquisition unit The driving transistor of the non-selected pixel circuit row receives a data signal based on the characteristic value stored in the characteristic value storage unit at the previous selection and the driving voltage of the driving transistor according to the light emission amount of the light emitting element. A display device that outputs to a source terminal of the display.   Immediately before passing the first reference current, a first expected voltage is supplied to the source terminal of the driving transistor so that the voltage of the source terminal approaches the voltage in the equilibrium state, and the second reference current is supplied. An expected voltage supply unit that supplies a second expected voltage so that the voltage of the source terminal approaches the voltage in the equilibrium state is provided to the source terminal of the driving transistor immediately before the current flows. The display device according to claim 4.   8. A reverse bias voltage output unit for supplying a reverse bias voltage having a magnitude corresponding to a data signal output to the driving transistor to a gate terminal of the driving transistor. A display device according to claim 1.   9. The display device according to claim 8, wherein the driving transistor is configured by a thin film transistor having a current characteristic with a negative threshold voltage.   The display device according to claim 4, wherein the driving transistor is a thin film transistor made of IGZO (InGaZnO).   Some pixel circuits selected by the current value acquisition unit include a pixel circuit having the red light emitting element, a pixel circuit having the green light emitting element, and a blue light emitting element belonging to one display pixel. 6. The display device according to claim 5, wherein the display device is a circuit.   10. The common electrode line for supplying a different voltage between the reverse bias voltage application period and a period other than the reverse bias voltage application period is connected to the cathode terminal of the light emitting element. Display device.