WO2007111202A1 - Dispositif d'attaque pour élément électroluminescent commandé en courant - Google Patents

Dispositif d'attaque pour élément électroluminescent commandé en courant Download PDF

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Publication number
WO2007111202A1
WO2007111202A1 PCT/JP2007/055745 JP2007055745W WO2007111202A1 WO 2007111202 A1 WO2007111202 A1 WO 2007111202A1 JP 2007055745 W JP2007055745 W JP 2007055745W WO 2007111202 A1 WO2007111202 A1 WO 2007111202A1
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WIPO (PCT)
Prior art keywords
current
emitting element
light emitting
drive
controlled light
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Ceased
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PCT/JP2007/055745
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English (en)
Japanese (ja)
Inventor
Hideo Ochi
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Pioneer Corp
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Pioneer Corp
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    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
    • G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
    • G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
    • G09G3/3208—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED]
    • G09G3/3225—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED] using an active matrix
    • G09G3/3233—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED] using an active matrix with pixel circuitry controlling the current through the light-emitting element
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2300/00—Aspects of the constitution of display devices
    • G09G2300/08—Active matrix structure, i.e. with use of active elements, inclusive of non-linear two terminal elements, in the pixels together with light emitting or modulating elements
    • G09G2300/0809—Several active elements per pixel in active matrix panels
    • G09G2300/0819—Several active elements per pixel in active matrix panels used for counteracting undesired variations, e.g. feedback or autozeroing
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/02—Improving the quality of display appearance
    • G09G2320/0233—Improving the luminance or brightness uniformity across the screen

Definitions

  • the present invention relates to a drive device for driving a current-controlled light emitting element such as an organic EL element or an organic light emitting diode used in a display device such as a display.
  • a current-controlled light emitting element such as an organic EL element or an organic light emitting diode used in a display device such as a display.
  • each pixel is formed of a current control type light emitting element and a thin film transistor (TFT) for supplying a drive current Id to the current control type light emitting element.
  • TFT thin film transistor
  • each drive circuit is scanned by the scanning line and the signal line to supply a pixel signal, and the gate potential Vg of the drive transistor formed in each drive circuit is controlled.
  • a predetermined drive current Id is supplied to the current-controlled light emitting element to display an image or the like.
  • the drive transistor formed of the above-described thin film transistor has a variation in the drive current Id with respect to the above-described gate voltage Vg due to, for example, difficulty in manufacturing or inevitably changing electrical characteristics. Therefore, improvement of contrast ratio and suppression of luminance fluctuation There was a problem that it was difficult to control.
  • FIG. 1 (b) showing the transfer characteristics of the gate-source voltage Vgs and drive current (i.e., drain current) Id, first, good contrast
  • a drive transistor with excellent on / off characteristics against changes in the gate-source voltage Vgs is required! RU
  • a drive transistor formed of a thin film transistor may have difficulty in manufacturing, etc. Force inevitably may not have excellent on / off characteristics, and the characteristic curve CAS
  • the structural power of the thin film transistor inevitably causes a leakage current, and the appropriate drain current Id with respect to the gate potential Vg is not supplied to the current-controlled light emitting element, resulting in luminance fluctuations, There is a problem that the contrast ratio deteriorates due to the above-mentioned “black floating” phenomenon.
  • the setting range of the gate potential Vg of the drive transistor formed of a thin film transistor is limited, and it may not be possible to completely turn off the drive transistor.
  • the drive transistor is formed of a depletion type thin film transistor, the drain current Id flows even if the gate-source voltage Vgs is set to 0 volt, as shown by the characteristic curve CASE 3, and the contrast ratio In some cases, it is difficult to improve the brightness and to set a desired luminance.
  • the present invention has been made in view of such a conventional problem, and an object of the present invention is to provide a drive device for a current-controlled light-emitting element that realizes, for example, improvement in contrast ratio and suppression of luminance fluctuation. To do.
  • the invention according to claim 1 is a drive device for a current control type light emitting element in an active matrix display device, and is formed of a P-channel thin film transistor connected to the current control type light emitting element and supplying a drive current.
  • Drive transistor and the current control Current control means connected to the connection point between the light emitting element and the drive transistor, and the current control means detects the voltage at the connection point as the voltage between the positive and negative electrodes of the current control light emitting element.
  • the supply of the drive current to the current control type light emitting element is suppressed by discharging a branch current from the connection point side,
  • a branch current having a small current value substantially equal to the branch current when the voltage is less than the threshold value of the current control type light emitting element is discharged from the connection point side. Then, the driving current is supplied to the current-controlled light emitting element.
  • the invention according to claim 2 is a drive device for a current control type light emitting element in an active matrix display device, and is formed of an n-channel thin film transistor connected to the current control type light emitting element and supplying a drive current. And a current control means connected to a connection point between the current control type light emitting element and the drive transistor, and the current control means outputs the voltage at the connection point to the current control type light emission.
  • a branch current flows into the connection point side, and the drive to the current control type light emitting element is detected.
  • the drive current is supplied to the current-controlled light-emitting element by flowing a branch current having a small current value substantially equal to the branch current to the connection point side.
  • FIG. 1 is an explanatory diagram for explaining a configuration and characteristics of a driving device in a display using a conventional current-controlled light-emitting element.
  • FIG. 2 is a plan view and an equivalent circuit diagram showing the configuration of the drive circuit (drive device) of the embodiment.
  • FIG. 3 is a characteristic diagram showing characteristics of the drive circuit shown in FIG.
  • FIG. 4 is an equivalent circuit diagram showing a configuration of a modified example of the drive circuit shown in FIG.
  • FIG. 5 is an equivalent circuit diagram and a characteristic diagram showing the configuration and characteristics of the drive circuit of Example 1.
  • FIG. 6 is an equivalent circuit diagram showing the configuration of the drive circuit of Example 2.
  • FIG. 7 is an equivalent circuit diagram and a characteristic diagram showing the configuration and characteristics of the drive circuit of Example 3.
  • FIG. 8 is an equivalent circuit diagram showing the configuration of the drive circuit of Example 4.
  • Fig. 2 (a) is a plan view showing the basic structure of an active matrix type display device formed using current-controlled light emitting elements in this embodiment
  • Fig. 2 (b) is a diagram for each pixel. It is the circuit diagram which represented the structure of the provided drive device with the equivalent circuit.
  • this display device has basically the same structure as a conventionally known organic EL display or organic diode display. That is, a predetermined number of scanning lines X, signal lines Y, and current supply lines Z are formed along a matrix on a V substrate, not shown, and an organic pixel as a light-emitting pixel is located near each intersection.
  • a current control type light emitting element such as an EL element or an organic light emitting diode (hereinafter referred to as “light emitting element”) and a driving device (hereinafter referred to as “driving circuit”) are formed and arranged in a matrix.
  • the configuration of the light emitting element Pij formed at the position of i row and j column and the drive circuit Mij will be described based on FIG. 2 (b). It is formed with a silicon thin film transistor (TFT) and has a switch circuit SWij and a drive transistor Bij for supplying a drive current Ip to the light emitting element Pij.
  • the circuit Dij is configured, and the forward bias is applied by setting the cathode of the light emitting element Pij and the ground side terminal of the current control circuit Dij to the ground potential Vss and applying the power supply voltage Vdd to the current supply line Zj. It is designed to operate in this state.
  • ground-side terminal of the current control circuit Dij may be set to another potential Vb instead of the ground potential Vss. In short, the current control circuit Dij should be operated in the forward bias state.
  • the switch circuit SWij is scanned and address-selected by the scanning signal and the pixel signal supplied via the scanning line Xi and the signal line Yj, and the gate potential of the drive transistor Bij is set based on the pixel signal. Generates drive signal Vij for setting.
  • the drive transistor Bij is formed of a p-channel thin film transistor that is turned on / off according to a voltage change of the drive signal Vij, and has a source connected to the current supply line Zj and a drain. IN is connected to the anode of the light emitting element Pij and the current control circuit Dij.
  • the current control circuit Dij detects the voltage Vq generated at the connection point Q between the drain of the drive transistor Bij and the light emitting element Pij as a voltage between the anode and the cathode of the light emitting element Pij, and a predetermined voltage Vq
  • the branch current Ic with the voltage-current conversion coefficient Gm is shunted from the connection point Q side and discharged to the Darling side.
  • the current control circuit Dij diverts the branch current Ic corresponding to the product of the voltage Vq and the voltage-current conversion coefficient Gm from the drain current Id of the drive transistor Bij, thereby As shown, the drive current Ip supplied to the light emitting element Pij is adjusted.
  • the voltage-current conversion coefficient Gm is set based on the result of analyzing and evaluating the electrical characteristics of the drive transistor Bij.
  • an evaluation drive transistor having the same structure as the drive transistor Bij is created, and the evaluation drive transistor is operated under conditions that take into account temperature dependence, aging, and other factors.
  • the characteristic curves in Figure 1 (b) CASE 1, CASE2, CASE3, etc. Measure the transfer characteristic represented by Also, the voltage Vq at the connection point Q described above is obtained from the relationship between the measured drain-source voltage Vds and the power supply voltage Vdd.
  • the characteristic curve CASE1 is an example of the characteristics of the drive transistor Bij having a good on-Z-off characteristic
  • the characteristic curve CASE2 is a drive transistor Bij formed in an unenhancement type
  • the gate-source voltage Vgs is
  • the characteristic curve CASE3 shows the characteristics when drain current Id flows even if it is set to 0 volt
  • the characteristic curve CASE3 is formed even if the drive transistor Bij is a delay type and the gate-source voltage Vgs is set to 0 volt. This is an example of characteristics when drain current Id flows.
  • the drain current Id Based on the drain current Id generated in the evaluation drive transistor when the gate-source voltage Vgs is 0 V and the drain voltage (voltage corresponding to the voltage Vq at the connection point Q), the drain current Id
  • the voltage-current conversion coefficient Gm that satisfies the condition that the branch current Ic is almost equal
  • the drain current Id and the drain voltage (voltage corresponding to the voltage Vq at the connection point Q) increase within the range of the power supply voltage Vdd where the gate-source voltage Vgs of the drive transistor for evaluation exceeds 0 volt. Determine the voltage-current conversion coefficient Gm that satisfies the condition that the branch current Ic is constant or slightly increased.
  • a current control circuit Dij that generates a branch current Ic with respect to the voltage Vq at the connection point Q is designed according to the voltage-current conversion coefficient Gm that has been analyzed and evaluated.
  • the gate source of the drive transistor Bij is exemplified by the symbols lea and Icb in the figure.
  • the branch current Ic is generated approximately equal to the drain current Id of the drive transistor Bij with respect to the voltage Vq at the connection point Q, and the gate-source voltage Vgs of the drive transistor Bij is 0 volt.
  • a current control circuit Dij that generates a constant or slightly increasing branch current Ic with respect to the voltage Vq at the connection point Q is formed in the drive circuit Mij.
  • the current control circuit Dij suppresses the drive current Ip by discharging the drain current Id as the branch current Ic when the voltage Vq is equal to or lower than the threshold value of the light emitting element Pij.
  • the driving current Ip is supplied to the light emitting element Pij by discharging the branch current Ic having the small current value described above.
  • the drive transistor Bij has a transfer characteristic represented by the characteristic curve CASE3 (in the case of the depletion type)
  • the drive transistor Bij When the gate-source voltage Vgs is 0 volt, the drain current Id of the drive transistor Bij is almost equal to the drain voltage Id of the drive transistor Bij and the branch current Ic is generated, and the gate-source voltage Vgs of the drive transistor Bij is When the voltage exceeds 0 V, a current control circuit Dij that generates a constant or slightly increasing branch current Ic with respect to the voltage Vq at the connection point Q is formed in the drive circuit Mij.
  • the current control circuit Dij since the current control circuit Dij is provided, even if the drain current Id is generated when the drive transistor Bij is turned off by the drive voltage Vin, the drain of the drain current Id is generated. Since the current Id becomes the branch current Ic and is discharged through the current control circuit Dij, the inflow of the drive current Ip to the light emitting element Pij can be suppressed. Therefore, black Occurrence of the “black floating” phenomenon during display can be suppressed and the contrast ratio can be improved.
  • the current control circuit Dij discharges the fluctuation of the drain current Id as the branch current Ic and suppresses the luminance fluctuation of the light emitting element Pij. it can.
  • the drive transistor Bij is formed of a thin film transistor
  • the threshold of the drive transistor Bij It is known that a phenomenon called “threshold shift”, in which the voltage gradually changes, is caused by the current control circuit Dij, but the change in the drain current Id that is output when the threshold shift occurs is the branch current. Since it is discharged as Ic, adverse effects on the drive current Ip supplied to the light emitting element Pij can be suppressed, and variations in light emission luminance can be improved.
  • the drive transistor Bij when the drive transistor Bij is formed of a p-channel thin film transistor, the light-emitting element Pij is also applied when the force drive transistor Bij described above is formed of an n-channel thin film transistor. And the drive circuit Mij should be configured to operate in the forward bias state.
  • a current control circuit Dij is formed between the current supply line Zj and the drain of the drive transistor Bij, which is an n-channel thin film transistor.
  • the current Ic that is substantially equal to the drain current Id of the drive transistor Bij is at least when the gate-source voltage Vgs of the drive transistor Bij is 0 volt.
  • Is supplied to the drive transistor Bij, and the voltage-current conversion coefficient Gm is determined so that the current Ic becomes constant or slightly increased when the gate-source voltage Vgs changes from 0 volt according to the drive voltage Vin.
  • the current control circuit Dij can be provided to suppress the occurrence of the “black floating” phenomenon during black display. And the contrast ratio can be improved.
  • the current control circuit Dij By supplying the fluctuation amount of the drain current Id of the current to the drive transistor Bij as the current Ic, the luminance fluctuation of the light emitting element Pij can be suppressed.
  • FIG. 5 (a) shows a light emitting element Pij and a drive circuit Mij formed for each pixel in an active matrix display device formed using a current control type light emitting element.
  • FIG. 3 is a circuit diagram showing the configuration with an equivalent circuit, and the same or corresponding parts as those in FIGS. 2 (a) and 2 (b) are denoted by the same reference numerals.
  • the drive circuit Mij of the present embodiment is formed with an organic semiconductor or a low-temperature polysilicon thin film transistor, and includes a switch transistor Sij formed of a P-channel thin film transistor and a capacitor.
  • a switch circuit SWij having an element Cij, a drive transistor Bij formed of a p-channel thin film transistor, and a current control transistor Da formed of a p-channel thin film transistor are formed.
  • the display device of the present embodiment has a predetermined number of scanning lines X, signal lines Y, and current supply lines Z on a substrate (not shown). Is formed along a matrix, and in the vicinity of each of these intersections, a current control type light emitting element (light emitting element) such as an organic EL element or an organic light emitting diode as a light emitting pixel and a drive circuit are formed to form a matrix. Is arranged. A light emitting element Pij and a drive circuit Mij are formed at the position of i row and j column.
  • the switch transistor Sij has a source connected to the current supply line Zj via the signal line Yj, a gate connected to the scanning line Xi, and a drain connected to the capacitance element Cij.
  • the switch transistor Sij is turned on when a scanning signal is applied through the scanning line Xi, and receives a pixel signal supplied through the signal line Yj and accumulates it in the capacitor element Cij as a charge transistor.
  • the drive voltage Vin for setting the gate potential of the capacitor Bij is generated.
  • the capacitive element Cij is described above for a long time (one frame period) corresponding to the case where the surface sequential scanning is performed. Therefore, the luminance of the light emitting element Pij that emits light by receiving the drive current Ip from the drive transistor Bij can be stabilized.
  • the drive voltage Vin is applied to the gate, and the source is the current supply line Z.
  • the drain is connected to the anode of the light emitting element Pij and the source of the current control transistor Da.
  • the light emitting element Pij has an anode connected to the drain of the drive transistor Bij and a cathode connected to a ground line (not shown) of the ground potential Vss.
  • the current control transistor Da corresponds to the current control circuit Dij shown in Fig. 2 (b).
  • the source is connected to the connection point Q between the drain of the drive transistor Bij and the anode of the light emitting element Pij, and the gate and The drain is connected to the above-described ground line. Then, based on the mutual conductance gm, a branch current Ic corresponding to the voltage Vq of the connection point Q applied between the gate and source is generated, and the drain current Id force of the drive transistor Bij also sinks the branch current Ic. Then discharge to the Dutch side.
  • the current control transistor Da uses the mutual conductance gm as the voltage-current conversion coefficient Gm described above, and sinks the branch current Ic corresponding to the voltage Vq from the drain current Id, whereby the drive current Ip supplied to the light emitting element Pij is obtained. Is adjusted to the current value represented by Id—Ic.
  • the channel width Wd of the current control transistor Da is compared with the ratio (LbZWb) of the channel width Wb and the channel length Lb of the drive transistor Bij capable of outputting a drain current Id having a large current value.
  • the channel length Ld ratio (LdZWd) is designed to be a predetermined large value. Furthermore, by designing the ratio of the channel width Wd to the channel length Ld (LdZWd) to a predetermined value, the drain current Id output when the gate-source voltage Vgs of the drive transistor Bij is 0 vol.
  • the current control transistors Da are mutually connected so that the branch current Ic is slightly increased even when the equal branch current Ic is generated and the drive transistor Bij is turned on and the voltage Vq at the connection point Q rises. Conductance gm is determined.
  • the current control transistor Da is designed by adjusting the ratio (L dZWd) of the channel width Wd and the channel length Ld, so that the connection as shown in the characteristic diagram of FIG. A small branch current Ic is generated with respect to the voltage Vq at point Q.
  • the switch transistor Sij When the scanning signal is supplied via the scanning line XI, the switch transistor Sij is turned on, and the pixel signal supplied via the signal line Yj is input. Capacitance element Cij receives the input signal. The signal is stored as an electric charge, and a drive voltage Vin for setting the gate potential of the drive transistor Bij is generated. The drive transistor Bij is turned on or off according to the level of the drive voltage Vin.
  • the drain current Id is discharged as the branch current Ic, and the inflow of the driving current Ip to the light emitting element Pij is suppressed.
  • the drain current Id is changed as shown in FIG. 5 (b).
  • the drive transistor Bij is turned on, the voltage Vq at the connection point Q increases, the anode-cathode voltage of the light emitting element Pij also exceeds the threshold value, and the branch current Ic of the current control transistor Da is also transconductance gm. Increases slightly. However, since the branch current Ic has a smaller current value than the drain current Id, a sufficient drive current Ip is supplied to the light emitting element Pij to emit light.
  • the drain current Id of the drive transistor Bij changes due to a change over time or the like, the fluctuation of the drain current Id becomes a branch current Ic and is discharged to the ground side through the current control transistor Da.
  • the fluctuation of the driving current Ip is suppressed, and the luminance fluctuation of the light emitting element Pij is suppressed.
  • the current control transistor Da detects the voltage Vq at the connection point Q between the drive transistor Bij and the light emitting element Pij as a gate-source voltage, and performs a predetermined mutual Since the branch current Ic having a small current value is sinked according to the conductance gm, the drain current Id is reduced when the drive transistor Bij is turned off by the drive voltage Vin. Even if it occurs, the drain current Id can be discharged as the branch current Ic, and the inflow of the drive current Ip to the light emitting element Pij can be suppressed. Therefore, it is possible to suppress the occurrence of the “black floating” phenomenon during black display and improve the contrast ratio.
  • the current control transistor Da discharges the variation of the drain current Id as the branch current Ic, so that the luminance variation of the light emitting element Pij is suppressed. can do.
  • the drive transistor Bij and the current control transistor Da are formed by the same semiconductor manufacturing process, the relative accuracy of the electrical characteristics of the two can be improved. For this reason, if the electrical characteristics of the drive transistor Bij change due to changes over time, the electrical characteristics of the current control transistor Da also change with the same tendency, and the fluctuation of the drain current Id of the drive transistor Bij is caused by the branch current Ic. It can be effectively removed, and the luminance fluctuation of the light emitting element Pij can be suppressed and the contrast ratio can be improved.
  • the potentials of the gate and drain of the current control transistor Da are both set to the cathode potential (ground potential) Vss of the light emitting element Pij.
  • the mutual conductance gm of the current control transistor Da may be adjusted by setting the drain potential to different potentials Va and Vb, or by setting the drain potential to a potential different from the ground potential Vss even if they are the same potential! / ,.
  • the current control transistor Da is also formed of a p-channel thin film transistor.
  • the source is connected to the connection point Q and operates under forward bias.
  • the drive transistor Bij is formed of an n-channel thin film transistor
  • the current control circuit Dij is a current control transistor Da having an n-channel thin film transistor force.
  • the drain and gate of the n-channel thin film transistor are connected to the anode of the light emitting element Pij
  • the source is connected to the connection point Q
  • the branch current Ic flows into the light emitting element Pij. ⁇ .
  • the inflowing branch current Ic is shown in accordance with the anode-cathode voltage of the light emitting element Pij.
  • the current control transistor Da which is an n-channel thin film transistor, is formed in a smaller size than the drive transistor Bij so that the current Ic shown in FIG. 3 changes slightly, and the ratio of the channel width to the channel length. Should be designed with a large value.
  • FIG. 6 the same or corresponding parts as those in FIGS. 2 (a), 2 (b) and 5 (a) are denoted by the same reference numerals.
  • the drive circuit Mij of the present embodiment is provided with a current control circuit Mij formed with a current control transistor Da, a switch transistor Db, and a capacitive element Cd.
  • the current control transistor Da is formed by a small thin film transistor that can flow a branch current Ic having a small current value, and its source is connected to a connection point Q between the drive transistor Bij and the light emitting element Pij.
  • the drain is set to the same ground potential Vss as the cathode of the light emitting element Pij, the gate is connected to the drain of the switch transistor Db, and the capacitor element Cd is connected between the gate and the drain.
  • the capacitive element Cd may be formed of a small capacitive element sufficient to store electric charge for operating the current control transistor Da.
  • the switch transistor Db is formed of a small-sized thin film transistor sufficient to supply the current for accumulating the charge in the capacitive element Cd.
  • the drain of the switch transistor Db is connected to the gate of the current control transistor Da and the capacitive element Cd, the gate is connected to the scanning line Xi, and the source is connected to the control line YBij.
  • a predetermined control signal is supplied to the current control circuit formed for each pixel.
  • a control line is formed, and the scanning signal CNTi of the scanning line Xi is supplied to the switch transistor Db in the current control circuit Dij formed at the position of i row and j column shown in FIG.
  • a signal CNTj having a phase opposite to that of the pixel signal on the line Yj is supplied.
  • the anti-phase signal CNTj described above is a force that can be generated simply by inverting the pixel signal of the signal line YBij with a NOT circuit (inverting circuit). In order to cause a decrease or the like, it is desirable to form outside the display screen area.
  • Capacitance element Cij accumulates the input signal as electric charge, generates drive voltage Vin for setting the gate potential of drive transistor Bij, and drive transistor Bij is turned on or off according to the level of drive voltage Vin. To do.
  • the switch transistor Db provided in the current control circuit Dij is also supplied with the scanning signal CNTi via the scanning line Xi and further supplied with the signal CNTj via the control line YBij, so that the switch The signal CNTj input through the transistor Db is accumulated as a charge in the capacitive element Cd, and the current control transistor Da is turned off or on according to the level of the voltage Vc generated in the capacitive element Cd.
  • the drive voltage generated by the capacitive element Cij in the switch circuit SWij The voltage Vc generated by Vij and the capacitive element Cd in the current control circuit Dij is also in an opposite phase relationship. Therefore, when the drive transistor Bij is on, the current control transistor Da is off, and when the drive transistor Bij is off, the current control transistor Da is on.
  • the current control transistor D a that is turned off or on in the opposite phase to the drive transistor Bij that is turned on or off according to the pixel signal is provided. Therefore, even if the drain current Id occurs when the drive transistor Bij is turned off by the drive voltage Vin, the drain current Id is discharged as the branch current Ic, and the inflow of the drive current Ip to the light emitting element Pij is suppressed. be able to. Therefore, it is possible to suppress the occurrence of the “black floating” phenomenon during black display and to improve the contrast ratio.
  • the current control transistor Da discharges the fluctuation amount of the drain current Id as the branch current Ic, thereby suppressing the luminance fluctuation of the light emitting element Pij. can do.
  • the drive transistor Bij and the current control transistor Da are formed by the same semiconductor manufacturing process, the relative accuracy of the electrical characteristics of both can be improved. For this reason, if the electrical characteristics of the drive transistor Bij change due to changes over time, the electrical characteristics of the current control transistor Da also change with the same tendency, and the fluctuation of the drain current Id of the drive transistor Bij is caused by the branch current Ic. It can be effectively removed, and the luminance fluctuation of the light emitting element Pij can be suppressed and the contrast ratio can be improved.
  • FIG. 7 (a) the same or corresponding parts as those in FIGS. 2 (a), 2 (b) and 5 (a) are indicated by the same reference numerals.
  • FIG. 7B is a characteristic diagram for explaining the function of the drive circuit of this embodiment.
  • the drive circuit Mij of the present embodiment is provided with a current control transistor Dd formed of a depletion type thin film transistor in which the gate and source are connected, and the transistor Dd
  • the gate and source power of the transistor is connected to a connection point Q between the drain of the drive transistor Bij and the anode of the light emitting element Pij, and the drain is set to the same ground potential Vs s as the cathode of the light emitting element Pij.
  • the current control transistor Dd is a depletion type thin film transistor in which the gate and the source are connected to each other. Therefore, the drive transistor Vid is driven by the drive voltage Vij.
  • a branch current Ic with a current value almost the same as the drain current Id that is output when the gate-source voltage Vgs of the star Bij becomes 0 volts is generated, and the voltage Vq at the connection point Q changes within the range of the power supply voltage Vdd. Even in this case, a branch current Ic having a substantially constant current value is generated.
  • the current control transistor Dd sinks the branch current Ic having a substantially constant current value from the connection point Q side and discharges it to the ground side.
  • the current control transistor Dd Sinks the branch current Ic and discharges it to the ground side, almost equal to the drain current. For this reason, when a pixel signal for black display is supplied via the signal line Yj, even if the drain current Id is output from the drive transistor Bij, the inflow of the drive current Ip to the light emitting element Pij is suppressed, Occurrence of black float is prevented and the contrast ratio is improved.
  • the branch current Ic of the current control transistor Dd has a substantially constant small current value. For this reason, the drain current Id of the drive transistor Bij becomes almost the driving current Ip and is supplied to the light emitting element Pij to emit light.
  • the branch current Ic having a constant current value is generated approximately equal to the drain current Id output when the drive transistor Bij is set to OFF, and the connection point Q Since the current control transistor Dd that sinks and discharges the branch current Ic is provided, the occurrence of the “black floating” phenomenon during black display can be suppressed and the contrast ratio can be improved. Can do.
  • the current control transistor Dd discharges the fluctuation of the drain current Id as the branch current Ic, and the luminance fluctuation of the light emitting element Pij can be suppressed. .
  • the drive circuit Mij of the present embodiment is provided with a current control circuit Dij having a high-resistance resistor R and a diode DI, and the resistance scale is generated between the drain and the drive transistor Bij.
  • the connection point Q between the anode of the optical element Pij and the anode of the diode DI is connected, and the force sword of the diode DI is set to the same ground potential Vss as the cathode of the light emitting element Pij.
  • the resistor R is formed of the same material as the ITO transparent electrode that is formed as an anode-side electrode to emit light emitted from the light emitting element Pij, and in the same manufacturing process as the ITO transparent electrode.
  • the resistance value is increased by being formed long and narrow.
  • the resistance value of the resistor R that generates a branch current Ic substantially equal to the drain current Id that is output when the drive transistor Bij is set to OFF by the drive voltage Vin is determined.
  • the diode DI is formed using a p-type thin film layer and an n-type thin film layer formed in the manufacturing process of the light emitting element Pij, and has a structure having a PN junction.
  • the light-emitting element Pij is an organic EL element
  • the p-type thin film layer and the n-type thin film layer are formed when the p-type hole transport layer and the n-type electron transport layer excluding the light-emitting layer are formed.
  • a diode DI having a PN junction is formed.
  • the diode DI has the same structure as that obtained by removing the light emitting layer from the organic EL element, thereby lowering the threshold of the diode DI compared to the threshold of the light emitting element Pij.
  • the drain current Id flows even when the gate-source voltage gs of the drive transistor Bij becomes 0 volt due to the drive voltage Vin, the drain current Id flows. Id becomes the branch current Ic generated by the resistor R and the diode DI, and the connection point Q-side force is also released to the ground side. Further, since the threshold value of the diode DI is lower than the threshold value of the light emitting element Pij, the drain current Id starts to be emitted before the light emitting element Pij emits light. For this reason, it is possible to suppress the occurrence of the “black floating” phenomenon during black display and to improve the contrast ratio.
  • the drain current Id of the drive transistor Bij fluctuates due to changes over time, the fluctuation of the drain current Id is discharged as the branch current Ic via the resistor R and the diode DI. Can be suppressed.
  • the resistor R, the diode DI force, the light emitting element Pij, and the ITO transparent electrode are manufactured. Since it is formed at the same time during the manufacturing process, it is not necessary to increase the manufacturing process, and it is possible to simplify the manufacturing process.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Control Of El Displays (AREA)
  • Electroluminescent Light Sources (AREA)

Abstract

L'invention concerne un dispositif d'attaque pour des éléments électroluminescents commandés en courant, par lequel le rapport de contraste est amélioré et la fluctuation de luminance est diminuée. Le dispositif d'attaque est muni d'un transistor d'attaque (Bij) qui est relié à un élément électroluminescent commandé en courant (Pij) et qui est formé d'un transistor à film mince permettant d'appliquer un courant d'attaque (Ip), ainsi qu'un élément de commande de courant (Dij) qui est relié à un point de connexion (Q) entre l'élément électroluminescent commandé en courant (Pij) et le transistor d'attaque (Bij). Lorsque le circuit commandé en courant (Dij) détecte une tension (Vq) du point de connexion (Q) en tant que tension entre l'anode et la cathode de l'élément électroluminescent commandé en courant (Pij) et que la tension détectée (Vq) est une valeur de seuil de l'élément électroluminescent commandé en courant (Pij) ou inférieure, la fourniture du courant d'attaque (Ip) à l'élément électroluminescent commandé en courant (Pij) est diminuée en déchargeant un courant dérivé (Ic) du côté du point de connexion (Q). Lorsque la tension détectée (Vq) dépasse la valeur de seuil de l'élément électroluminescent commandé en courant (Pij), le courant d'attaque (Ip) est appliqué à l'élément électroluminescent commandé en courant (Pij) en déchargeant un courant dérivé d'une petite valeur de courant sensiblement identique au courant dérivé (Ic) à partir du côté du point de connexion (Q).
PCT/JP2007/055745 2006-03-28 2007-03-20 Dispositif d'attaque pour élément électroluminescent commandé en courant Ceased WO2007111202A1 (fr)

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JP2007322795A (ja) * 2006-06-01 2007-12-13 Nippon Hoso Kyokai <Nhk> 発光ダイオード駆動回路およびそれを使用した表示装置
JP2010079056A (ja) * 2008-09-26 2010-04-08 Kyocera Corp 画像表示装置
JP2013161084A (ja) * 2012-02-07 2013-08-19 Samsung Display Co Ltd 画素およびこれを利用した有機発光表示装置
US9549450B2 (en) 2012-07-25 2017-01-17 Samsung Display Co., Ltd. Pixel and organic light emitting display device using the same
JP2018036667A (ja) * 2012-08-02 2018-03-08 三星ディスプレイ株式會社Ｓａｍｓｕｎｇ Ｄｉｓｐｌａｙ Ｃｏ．，Ｌｔｄ． 有機発光表示装置
JP2018151506A (ja) * 2017-03-13 2018-09-27 セイコーエプソン株式会社 画素回路、電気光学装置および電子機器
CN114569102A (zh) * 2020-11-30 2022-06-03 华为技术有限公司 生物特征参数的测量方法和装置
WO2024148565A1 (fr) * 2023-01-12 2024-07-18 京东方科技集团股份有限公司 Circuit de pixels, procédé de commande d'attaque, substrat d'affichage et appareil d'affichage
JP2025067809A (ja) * 2023-10-12 2025-04-24 合肥維信諾科技有限公司 画素回路及び表示モジュール
CN120380532A (zh) * 2023-11-24 2025-07-25 京东方科技集团股份有限公司 一种驱动控制电路、驱动系统及显示装置

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JP2006098437A (ja) * 2004-09-28 2006-04-13 Sony Corp 画素回路及び表示装置

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* Cited by examiner, † Cited by third party
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JP2007322795A (ja) * 2006-06-01 2007-12-13 Nippon Hoso Kyokai <Nhk> 発光ダイオード駆動回路およびそれを使用した表示装置
JP2010079056A (ja) * 2008-09-26 2010-04-08 Kyocera Corp 画像表示装置
US10600365B2 (en) 2012-02-07 2020-03-24 Samsung Display Co., Ltd. Pixel and organic light emitting diode display having a bypass transistor for passing a portion of a driving current
JP2013161084A (ja) * 2012-02-07 2013-08-19 Samsung Display Co Ltd 画素およびこれを利用した有機発光表示装置
EP2626851A3 (fr) * 2012-02-07 2013-10-30 Samsung Display Co., Ltd. Pixel et dispositif dýaffichage électroluminescent organique lýutilisant
US9324264B2 (en) 2012-02-07 2016-04-26 Samsung Display Co., Ltd. Pixel and organic light emitting diode display having a bypass transistor for passing a portion of a driving current
US9728134B2 (en) 2012-02-07 2017-08-08 Samsung Display Co., Ltd. Pixel and organic light emitting diode display having a bypass transistor for passing a portion of a driving current
US11657762B2 (en) 2012-02-07 2023-05-23 Samsung Display Co., Ltd. Pixel and organic light emitting diode display having a bypass transistor for passing a portion of a driving current
US11189231B2 (en) 2012-02-07 2021-11-30 Samsung Display Co., Ltd. Pixel and organic light emitting diode display having a current flow in an off transistor in a black luminance condition
US9549450B2 (en) 2012-07-25 2017-01-17 Samsung Display Co., Ltd. Pixel and organic light emitting display device using the same
US10734470B2 (en) 2012-08-02 2020-08-04 Samsung Display Co., Ltd. Organic light emitting diode display
US12213358B2 (en) 2012-08-02 2025-01-28 Samsung Display Co., Ltd. Organic light emitting diode display with bent semiconductor layer
US10204976B2 (en) 2012-08-02 2019-02-12 Samsung Display Co., Ltd. Organic light emitting diode display
US10985234B2 (en) 2012-08-02 2021-04-20 Samsung Display Co., Ltd. Organic light emitting diode display
US10483342B2 (en) 2012-08-02 2019-11-19 Samsung Display Co., Ltd. Organic light emitting diode display
US11690266B2 (en) 2012-08-02 2023-06-27 Samsung Display Co., Ltd. Organic light emitting diode display with plurality of thin film transistors in portions of curved semiconductor layer
US11574988B2 (en) 2012-08-02 2023-02-07 Samsung Display Co., Ltd. Organic light emitting diode display with scan line between storage capacitor and voltage line
US11574990B2 (en) 2012-08-02 2023-02-07 Samsung Display Co., Ltd. Organic light emitting diode display with curved channel region
US11574991B2 (en) 2012-08-02 2023-02-07 Samsung Display Co., Ltd. Organic light emitting diode display with semiconductor layer having bent portion
US11574989B2 (en) 2012-08-02 2023-02-07 Samsung Display Co., Ltd. Organic light emitting diode display with thin film transistors in portions of curved semiconductor layer
JP2018036667A (ja) * 2012-08-02 2018-03-08 三星ディスプレイ株式會社Ｓａｍｓｕｎｇ Ｄｉｓｐｌａｙ Ｃｏ．，Ｌｔｄ． 有機発光表示装置
JP2018151506A (ja) * 2017-03-13 2018-09-27 セイコーエプソン株式会社 画素回路、電気光学装置および電子機器
CN114569102A (zh) * 2020-11-30 2022-06-03 华为技术有限公司 生物特征参数的测量方法和装置
WO2024148565A1 (fr) * 2023-01-12 2024-07-18 京东方科技集团股份有限公司 Circuit de pixels, procédé de commande d'attaque, substrat d'affichage et appareil d'affichage
US12543461B2 (en) 2023-01-12 2026-02-03 Hefei Boe Joint Technology Co., Ltd. Pixel circuit, driving control method, display substrate and display device
JP2025067809A (ja) * 2023-10-12 2025-04-24 合肥維信諾科技有限公司 画素回路及び表示モジュール
CN120380532A (zh) * 2023-11-24 2025-07-25 京东方科技集团股份有限公司 一种驱动控制电路、驱动系统及显示装置

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