WO2018049809A1 - 像素驱动电路及其驱动方法和显示装置 - Google Patents

像素驱动电路及其驱动方法和显示装置 Download PDF

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Publication number
WO2018049809A1
WO2018049809A1 PCT/CN2017/079241 CN2017079241W WO2018049809A1 WO 2018049809 A1 WO2018049809 A1 WO 2018049809A1 CN 2017079241 W CN2017079241 W CN 2017079241W WO 2018049809 A1 WO2018049809 A1 WO 2018049809A1
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Prior art keywords
signal
unit
thin film
driving
driving unit
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English (en)
French (fr)
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冯佑雄
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BOE Technology Group Co Ltd
Chengdu BOE Optoelectronics Technology Co Ltd
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BOE Technology Group Co Ltd
Chengdu BOE Optoelectronics Technology Co Ltd
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Priority to US15/558,537 priority Critical patent/US10157576B2/en
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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]
    • G09G3/3266—Details of drivers for scan electrodes
    • 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
    • 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
    • G09G3/3258—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 voltage across 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
    • 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
    • G09G2300/0842—Several active elements per pixel in active matrix panels forming a memory circuit, e.g. a dynamic memory with one capacitor
    • 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
    • G09G2300/0842—Several active elements per pixel in active matrix panels forming a memory circuit, e.g. a dynamic memory with one capacitor
    • G09G2300/0861—Several active elements per pixel in active matrix panels forming a memory circuit, e.g. a dynamic memory with one capacitor with additional control of the display period without amending the charge stored in a pixel memory, e.g. by means of additional select electrodes
    • 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
    • G09G2320/0238—Improving the black level

Definitions

  • the present disclosure relates to the field of display technologies, and in particular, to a pixel driving circuit, a driving method thereof, and a display device.
  • AMOLED Active Matrix Organic Light Emitting Diode
  • the threshold voltage (Vth) of the driving TFT of each pixel is uneven, and the threshold voltage of the driving TFT of each pixel (ie, T2 in the figure) is uneven, which results in The current flowing through the OLED at each pixel changes, thereby affecting the display effect of the entire image.
  • Embodiments of the present disclosure provide a pixel driving circuit, a driving method thereof, and a display device, which can avoid the influence of a threshold voltage drift of a driving unit on a driving current of an active light emitting device, thereby improving uniformity of a display image, and improving pixels.
  • the display effect in the dark state increases the contrast of the display.
  • an embodiment of the present disclosure provides a pixel driving circuit.
  • the pixel driving circuit includes: a light emitting device, a storage capacitor, a driving unit, and five switch units; each switch unit includes a control end, a first signal end, and a second signal end; and the control end of the switch unit is used to turn on or Turning off the conduction between the first signal end and the second signal end; the driving unit includes a control end, a signal input end and a driving end, and the control end and the signal input end of the driving unit are used to control the driving end The output driving signal; the control end of the driving unit and the first end of the storage capacitor, the first signal end of the first switching unit, the first signal end of the second switching unit, and the control end of the third switching unit Connected to the control terminal of the first switch unit for inputting a reset signal, the second signal end of the first switch unit is connected to an initialization voltage; and the control end of the second switch unit is configured to input a scan signal, The second signal end of
  • the control end of the driving unit and the first end of the storage capacitor, the first signal end of the first switching unit, the first signal end of the second switching unit, and the third switching unit The control terminal of the first switch unit is configured to input a reset signal, the second signal end of the first switch unit is connected to an initialization voltage; and the control end of the second switch unit is used for input Scanning signal, said second a second signal end of the switch unit is connected to the first signal end of the third switch unit; a second signal end of the third switch unit is used for inputting a data signal; and a control end of the fourth switch unit is used for inputting light a signal; a control end of the fifth switch unit is configured to input a reset signal, a first signal end of the fifth switch unit is connected to an initialization voltage, and a second signal end of the fifth switch unit is opposite to the light emitting device One end is connected.
  • the sum of the data signal voltage and the threshold voltage of the third switching unit can be written to the control end of the driving unit, thereby eliminating the driving.
  • the effect of changes in cell threshold voltage on luminescence; and a relatively small storage capacitor can also be used to implement the circuit structure.
  • the fifth switching unit can be utilized to initialize the first end of the light emitting device such that the voltage across the light emitting device can be adjusted to, for example, zero prior to illumination.
  • the leakage current generated by the driving unit may flow out through the first signal end of the fifth switching unit; therefore, leakage current does not flow to the light emitting device, so that the light is emitted
  • the device accurately displays the dark state, which increases the contrast of the display.
  • the embodiment of the present disclosure utilizes a storage capacitor, a driving unit, and five switching units to implement a driving circuit, which can obtain a smaller pixel layout, which helps to improve the resolution of the display; and improves the display of the pixel in the dark state. The effect is increased contrast.
  • the driving unit and the five switching units are thin film transistors; the control end of each switching unit and the control end of the driving unit are gates of the thin film transistor; the first signal end of each switching unit And the second signal end is a source and a drain of the thin film transistor, respectively, or the first signal end and the second signal end of each switching unit are respectively a drain and a source of the thin film transistor; a signal input of the driving unit
  • the terminal and the driving terminal are respectively a source and a drain of the thin film transistor, or the signal input terminal and the driving terminal of the driving unit are respectively a drain and a source of the thin film transistor.
  • the pixel driving circuit provided by the embodiment of the present disclosure, before the light emitting device emits light, the sum of the data signal voltage and the threshold voltage of the thin film transistor serving as the third switching unit can be written into the thin film used as the driving unit The gate of the transistor, thereby eliminating the influence of variations in the threshold voltage of the thin film transistor used as the driving unit on the light emission; and it is also possible to implement the circuit structure using a relatively small storage capacitor.
  • Embodiments of the present disclosure utilize a storage capacitor and six thin film transistors to implement a driver circuit that enables a smaller pixel layout that helps to increase the resolution of the display.
  • the driving unit and the five switching units are both P-type thin film transistors.
  • the driving unit and the five switching units are all N-type thin film transistors.
  • the switching unit and the driving unit employed in all embodiments of the present disclosure may be thin film transistors or field effect transistors or other devices having the same characteristics.
  • the source and drain of the thin film transistor are symmetrical, so the source and drain are interchangeable.
  • one of the poles is referred to as a source and the other pole is referred to as a drain.
  • the middle end of the thin film transistor is a gate, the signal input end is a source, and the signal output end is a drain.
  • the P-type thin film transistor is turned on when the gate is at a low voltage, and turned off when the gate is at a high voltage
  • the N-type thin film transistor is turned on when the gate is at a high voltage, and turned off when the gate is at a low voltage.
  • a P-type thin film transistor used as a driving unit when the gate voltage is a low voltage (the gate voltage is smaller than the source voltage), and the absolute value of the gate source voltage difference is greater than the threshold voltage, it is in an amplified state or a saturated state;
  • the N-type thin film transistor used as the driving unit is in an amplified state or a saturated state when the gate voltage is a high voltage (the gate voltage is greater than the source voltage) and the absolute value of the gate source voltage difference is larger than the threshold voltage.
  • the driving unit and the third switching unit are thin film transistors having the same specifications.
  • the threshold voltage values of thin film transistors having the same specifications have the same tendency to change. That is, the threshold voltage Vth3 of the thin film transistor used as the third switching unit is substantially equal to the threshold voltage Vthd of the thin film transistor used as the driving unit. Therefore, the thin film transistor used as the third switching unit can write the sum of the data line voltage and its threshold voltage (Vdata+Vth3) to the first end of the storage capacitor, thereby eliminating the influence of the threshold voltage Vthd of the driving unit on the driving current. .
  • the light emitting device is an organic light emitting diode.
  • an embodiment of the present disclosure further provides a display substrate.
  • the display substrate includes a pixel driving circuit as described in the above embodiments.
  • an embodiment of the present disclosure provides a display device.
  • the display device includes a pixel driving circuit as described in the above embodiments.
  • an embodiment of the present disclosure provides a driving method for the pixel driving circuit described above.
  • the driving method includes: a first stage, turning on a first signal end and a second signal end of the first switching unit, charging the storage capacitor by using the initialization voltage; and turning on the fifth switch unit a first signal end and a second signal end, the first end of the light emitting device is initialized by using the initialization voltage; the second stage, Turning on the first signal end and the second signal end of the second switching unit, using the data signal, charging the storage capacitor via a second signal end and a control end of the third switching unit; and third In a stage, the first signal end and the second signal end of the fourth switching unit are turned on, and the light emitting device is driven by the driving unit.
  • the driving method of the pixel driving circuit provided by the embodiment of the present disclosure, before the light emitting device emits light, the sum of the data signal voltage and the threshold voltage of the third switching unit can be written into the control end of the driving unit, This eliminates the influence of variations in the threshold voltage of the driving unit on the light emission; and it is also possible to implement the circuit structure using a relatively small storage capacitor.
  • the fifth switching unit can be utilized to initialize the first end of the light emitting device such that the voltage across the light emitting device can be adjusted to, for example, zero prior to illumination.
  • the leakage current generated by the driving unit may flow out through the first signal end of the fifth switching unit; therefore, leakage current does not flow to the light emitting device, so that the light is emitted
  • the device accurately displays the dark state, which increases the contrast of the display.
  • the embodiment of the present disclosure utilizes a storage capacitor, a driving unit, and five switching units to implement a driving circuit, which can obtain a smaller pixel layout, which helps to improve the resolution of the display; and improves the display of the pixel in the dark state. The effect is increased contrast.
  • the driving unit is a thin film transistor; in the third stage, the thin film transistor used as the driving unit is in a saturated state.
  • the drive current I OLED is only related to the value of the data signal voltage Vdata, and therefore the drive current is not affected by the threshold voltage Vthd of the thin film transistor used as the drive unit.
  • V GS is the voltage between the gate and the source of the thin film transistor
  • ⁇ ⁇ C ox W / L
  • ⁇ C ox is the process constant
  • W is the channel width of the thin film transistor
  • L is the channel of the thin film transistor
  • the lengths, W and L are all constants that can be selectively designed.
  • the pixel driving circuit provided by the embodiment of the present disclosure, before the light emitting device emits light, the sum of the data signal voltage and the threshold voltage of the third switching unit can be written to the control end of the driving unit, thereby eliminating the driving.
  • the effect of changes in cell threshold voltage on luminescence; and a relatively small storage capacitor can also be used to implement the circuit structure.
  • the embodiment utilizes a storage capacitor, a drive unit, and five switch units to implement the drive circuit, enabling a smaller pixel layout that helps increase the resolution of the display.
  • FIG. 1 is a schematic structural view of a pixel driving circuit of the prior art
  • FIG. 2 is a schematic structural diagram of a pixel driving circuit according to an embodiment of the present disclosure
  • FIG. 3 is a schematic structural diagram of a pixel driving circuit according to another embodiment of the present disclosure.
  • FIG. 4 is a schematic structural diagram of a pixel driving circuit according to another embodiment of the present disclosure.
  • FIG. 5 is a schematic structural diagram of a pixel driving circuit according to another embodiment of the present disclosure.
  • FIG. 6 is a schematic structural diagram of a display substrate according to an embodiment of the present disclosure.
  • FIG. 7 is a schematic structural diagram of a display device according to an embodiment of the present disclosure.
  • FIG. 8 is a flowchart of a driving method of a pixel driving circuit according to an embodiment of the present disclosure
  • FIG. 9 is a schematic diagram showing a timing state of an input signal of a pixel driving circuit according to an embodiment of the present disclosure.
  • an embodiment of the present disclosure provides a pixel driving circuit.
  • the pixel driving circuit includes: a light emitting device L, a storage capacitor Cst, a driving unit D, and five switching units S1, S2, S3, S4, and S5; each switching unit includes a control end, a first signal end, and a second signal end The control end of the switching unit is configured to turn on or off the conduction between the first signal end and the second signal end;
  • the driving unit D includes a control end D3, a signal input end D1 and a driving end D2,
  • the control terminal D3 and the signal input terminal D1 of the driving unit D are used to control a driving signal outputted at the driving end D2;
  • the control terminal 303 is connected to the control terminal 103 for inputting
  • the first signal terminal 401 of the fourth switch unit S4 is connected to the second terminal C2 of the storage capacitor Cst and the first voltage VDD, and the second switch unit S4 is second.
  • the signal terminal 402 is connected to the signal input terminal D1 of the driving unit D, and the driving terminal D2 of the driving unit D is connected to the first end L1 of the light emitting device L.
  • the control end of the driving unit and the first end of the storage capacitor, the first signal end of the first switching unit, the first signal end of the second switching unit, and the third switching unit The control terminal of the first switch unit is configured to input a reset signal, the second signal end of the first switch unit is connected to an initialization voltage; and the control end of the second switch unit is used for input Scanning a signal, a second signal end of the second switching unit is connected to a first signal end of the third switching unit; a second signal end of the third switching unit is used for inputting a data signal; and a fourth switching unit
  • the control end is used for inputting a lighting signal; the control end of the fifth switching unit is for inputting a reset signal, the first signal end of the fifth switching unit is connected to the initialization voltage, and the second signal end of the fifth switching unit is Connected to the first end of the light emitting device.
  • the data signal voltage and The sum of the threshold voltages of the third switching unit can be written to the control terminal of the driving unit, thereby eliminating the influence of the variation of the threshold voltage of the driving unit on the light emission; and the circuit structure can also be implemented using a relatively small storage capacitor .
  • the fifth switching unit can be utilized to initialize the first end of the light emitting device such that the voltage across the light emitting device can be adjusted to, for example, zero prior to illumination.
  • the leakage current generated by the driving unit may flow out through the first signal end of the fifth switching unit; therefore, leakage current does not flow to the light emitting device, so that the light is emitted
  • the device accurately displays the dark state, which increases the contrast of the display.
  • the embodiment of the present disclosure utilizes a storage capacitor, a driving unit, and five switching units to implement a driving circuit, which can obtain a smaller pixel layout, which helps to improve the resolution of the display; and improves the display of the pixel in the dark state. The effect is increased contrast.
  • the light emitting device may be an organic light emitting diode OLED;
  • the driving unit DTFT and the five switching units T1, T2, T3, T4 and T5 are thin film transistors; each switch The control end of the unit and the control end of the driving unit are both gates of the thin film transistor; the first signal end and the second signal end of each switching unit are the source and the drain of the thin film transistor, respectively, or each switch The first signal end and the second signal end of the unit are respectively a drain and a source of the thin film transistor; the signal input end and the driving end of the driving unit DTFT are respectively a source and a drain of the thin film transistor, or the driving The signal input terminal and the driving terminal of the unit DTFT are the drain and the source of the thin film transistor, respectively.
  • the sum of the data signal voltage Vdata and the thin film transistor threshold voltage Vth3 serving as the third switching unit T3 can be written to be used as the driving before the light emitting device emits light.
  • the gate of the thin film transistor of the unit DTFT thereby eliminating the influence of the variation of the threshold voltage of the thin film transistor serving as the driving unit DTFT on the light emission; and the circuit structure can also be realized using the relatively small storage capacitor Cst.
  • Embodiments of the present disclosure utilize a storage capacitor and six thin film transistors to implement a driver circuit that enables a smaller pixel layout that helps to increase the resolution of the display.
  • the driving unit and the five switching units are both P-type thin film transistors.
  • the driving unit and the five switching units are all N-type thin film transistors.
  • the switching unit and the driving unit employed in all embodiments of the present disclosure may be thin film transistors or field effect transistors or other devices having the same characteristics.
  • the source and drain of the thin film transistor are symmetrical, so the source and drain are interchangeable.
  • one of the poles is referred to as a source, and the other pole is referred to as a source. Drain.
  • the middle end of the thin film transistor is a gate, the signal input end is a source, and the signal output end is a drain.
  • the P-type thin film transistor is turned on when the gate is at a low voltage, and turned off when the gate is at a high voltage
  • the N-type thin film transistor is turned on when the gate is at a high voltage, and turned off when the gate is at a low voltage.
  • a P-type thin film transistor used as a driving unit when the gate voltage is a low voltage (the gate voltage is smaller than the source voltage), and the absolute value of the gate source voltage difference is greater than the threshold voltage, it is in an amplified state or a saturated state;
  • the N-type thin film transistor used as the driving unit is in an amplified state or a saturated state when the gate voltage is a high voltage (the gate voltage is greater than the source voltage) and the absolute value of the gate source voltage difference is larger than the threshold voltage.
  • the driving unit DTFT and the third switching unit T3 are thin film transistors having the same specifications.
  • the threshold voltage values of thin film transistors having the same specifications have the same tendency to change. That is, the threshold voltage Vth3 of the thin film transistor used as the third switching unit is substantially equal to the threshold voltage Vthd of the thin film transistor used as the driving unit. Therefore, the thin film transistor used as the third switching unit can write the sum of the data line voltage and its threshold voltage (Vdata+Vth3) to the first end of the storage capacitor, thereby eliminating the influence of the threshold voltage Vthd of the driving unit on the driving current. .
  • an embodiment of the present disclosure further provides a display substrate.
  • the display substrate 600 includes a pixel driving circuit 601 as described in the above embodiment.
  • the display substrate 600 may further include an element for supporting the substrate driving circuit, the gate line, the data line, and the like, which are not limited herein.
  • an embodiment of the present disclosure provides a display device. As shown in FIG. 7, the display device 700 includes the pixel driving circuit as described in the above embodiments.
  • an embodiment of the present disclosure provides a driving method for the pixel driving circuit described above.
  • the driving method includes: a first stage 801, turning on a first signal end and a second signal end of the first switching unit, and charging the storage capacitor by using the initialization voltage; a first signal end and a second signal end of the fifth switch unit, initializing a first end of the light emitting device by using the initialization voltage; and a second stage 802, turning on a first signal end of the second switch unit And the second signal end, using the data signal, charging the storage capacitor via the second signal end and the control end of the third switching unit; and the third stage 803, turning on the fourth switching unit A signal terminal and a second signal terminal drive the light emitting device by the driving unit.
  • the driving method of the pixel driving circuit provided by the embodiment of the present disclosure, before the light emitting device emits light, the sum of the data signal voltage and the threshold voltage of the third switching unit can be written into the control end of the driving unit, This eliminates the influence of variations in the threshold voltage of the driving unit on the light emission; and it is also possible to implement the circuit structure using a relatively small storage capacitor.
  • the fifth switching unit can be utilized to initialize the first end of the light emitting device such that the voltage across the light emitting device can be adjusted to, for example, zero prior to illumination.
  • the leakage current generated by the driving unit may flow out through the first signal end of the fifth switching unit; therefore, leakage current does not flow to the light emitting device, so that the light is emitted
  • the device accurately displays the dark state, which increases the contrast of the display.
  • the embodiment of the present disclosure utilizes a storage capacitor, a driving unit, and five switching units to implement a driving circuit, which can obtain a smaller pixel layout, which helps to improve the resolution of the display; and improves the display of the pixel in the dark state. The effect is increased contrast.
  • the driving unit is a thin film transistor; in the third stage, the thin film transistor used as the driving unit is in a saturated state.
  • the drive current I OLED is only related to the value of the data signal voltage Vdata, and therefore the drive current is not affected by the threshold voltage Vthd of the thin film transistor used as the drive unit.
  • V GS is the voltage between the gate and the source of the thin film transistor
  • ⁇ ⁇ C ox W / L
  • ⁇ C ox is the process constant
  • W is the channel width of the thin film transistor
  • L is the channel of the thin film transistor
  • the lengths, W and L are all constants that can be selectively designed.
  • the working principle of the pixel driving circuit provided by the embodiment of the present disclosure is described with reference to the circuit layout shown in FIG. 3 and the input signal timing of the pixel driving circuit shown in FIG. 9.
  • the P-type transistor is used in the pixel driving circuit shown in FIGS. 3 and 5, it is only necessary to adjust the corresponding gate voltage correspondingly when the type of the transistor is simply replaced.
  • the embodiment of the present disclosure does not limit the types of the respective thin film transistors. When the type of the thin film transistor is changed, it is only necessary to adjust the voltage signal applied to the gate of the thin film transistor.
  • the driving method of the pixel circuit provided by the embodiment of the present disclosure is taken as the standard. Technical person Any combination that can be easily conceived and realized based on the pixel driving circuit and the driving method provided by the embodiments of the present disclosure is within the protection scope of the present disclosure.
  • the reset signal Reset is a low voltage, turning on the source and the drain of the first switching unit T1, charging the storage capacitor Cst by using the initialization voltage Vint; turning on the source and the drain of the fifth switching unit T5.
  • the first end L1 of the light emitting device OLED is initialized by the initialization voltage Vint.
  • the potential of the gate of the driving unit DTFT is the initialization voltage Vint.
  • the scan signal Gate is at a low voltage, turning on the source and the drain of the second switching unit T2, and the third switching unit T3 exhibits a diode state at this time, using the data signal, via the third switching unit T3.
  • the source and the gate charge the storage capacitor Cst.
  • the potential of the gate of the driving unit DTFT is the sum of the data signal voltage Vdata and the threshold voltage Vth3 of the third switching unit T3.
  • the illuminating signal EM is at a low voltage, turning on the source and the drain of the fourth switching unit T4, and driving the OLED by the driving unit DTFT. Since the threshold voltage of the driving unit DTFT has been compensated on the gate of the driving unit DTFT in the second stage, according to the above formula, the driving current I OLED of the OLED is related to the data signal voltage Vdata, and the driving unit DTFT The threshold voltage is independent.
  • the input signal timing of the pixel driving circuit shown in FIG. 9 can also be applied to the circuit layout shown in FIG. 5, and details are not described herein again.
  • the sum of the data signal voltage and the threshold voltage of the third switching unit can be written to the control end of the driving unit, thereby eliminating the driving.
  • the effect of changes in cell threshold voltage on luminescence; and a relatively small storage capacitor can also be used to implement the circuit structure.
  • the fifth switching unit can be utilized to initialize the first end of the light emitting device such that the voltage across the light emitting device can be adjusted to, for example, zero prior to illumination.
  • the leakage current generated by the driving unit may flow out through the first signal end of the fifth switching unit; therefore, leakage current does not flow to the light emitting device, so that the light is emitted
  • the device accurately displays the dark state, which increases the contrast of the display.
  • the embodiment of the present disclosure utilizes a storage capacitor, a driving unit, and five switching units to implement a driving circuit, which can obtain a smaller pixel layout, which helps to improve the resolution of the display; and improves the display of the pixel in the dark state. The effect is increased contrast.

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Abstract

一种像素驱动电路及其驱动方法和显示装置（700）。在实施例中，利用一个存储电容（Cst）、一个驱动单元（D）和五个开关单元（S1、S2、S3、S4、S5）来实现驱动电路，能够获得更小的像素布局，其有助于提高显示的分辨率；并且提高了像素在暗态时的显示效果，增加了对比度。

Description

像素驱动电路及其驱动方法和显示装置
相关申请
本申请要求保护在2016年9月19日提交的申请号为201610830007.5的中国专利申请的优先权，该申请的全部内容以引用的方式结合到本文中。
技术领域
本公开涉及显示技术领域，尤其涉及一种像素驱动电路及其驱动方法和显示装置。
背景技术
有源矩阵有机发光二极管(Active Matrix Organic Light Emitting Diode，AMOLED)显示器是当今平板显示器研究领域的热点之一。与液晶显示器相比，有机发光二极管OLED具有低能耗、生产成本低、自发光、宽视角及响应速度快等优点，目前，在手机、PDA(掌上电脑)、数码相机等显示领域，OLED已经开始取代传统的LCD显示屏。像素驱动电路设计是AMOLED显示器核心技术内容，具有重要的研究意义。
与TFT-LCD(Thin Film Transistor Liquid Crystal Display，薄膜晶体管液晶显示器)利用稳定的电压控制亮度不同，OLED属于电流驱动，需要稳定的电流来控制发光。由于工艺制程和器件老化等原因，在现有的两个晶体管T1、T2和一个存储电容C的驱动电路中(参照图1所示)，其中驱动电流IOLED是由于数据线提供的电压Vdata作用在驱动晶体管(DTFT)饱和区域而产生的电流。该电流驱动OLED以发光，其中驱动电流计算公式为IOLED＝K(VGS-Vth)2，其中VGS为驱动晶体管栅极和源极之间的电压，Vth为驱动晶体管的阈值电压。由于工艺制程和器件老化等原因，各像素点的驱动TFT的阈值电压(Vth)存在不均匀性，各像素点的驱动TFT(即图中T2)的阈值电压存在不均匀性，这样就导致了流过每个像素点OLED的电流发生变化，从而影响整个图像的显示效果。
发明内容
本公开的实施例提供一种像素驱动电路及其驱动方法和显示装置，能够避免驱动单元的阈值电压漂移对有源发光器件驱动电流的影响，进而提高了显示图像的均匀性；并且提高了像素在暗态时的显示效果，增加了显示的对比度。
根据本公开的一个方面，本公开实施例提供了一种像素驱动电路。所述像素驱动电路包括：发光器件、存储电容、驱动单元和五个开关单元；每个开关单元包括控制端、第一信号端和第二信号端；所述开关单元的控制端用于开启或关闭所述第一信号端和第二信号端之间的导通；所述驱动单元包括控制端、信号输入端和驱动端，所述驱动单元的控制端和信号输入端用于控制在驱动端输出的驱动信号；所述驱动单元的控制端与所述存储电容的第一端、第一开关单元的第一信号端、第二开关单元的第一信号端、以及第三开关单元的控制端相连接；所述第一开关单元的控制端用于输入复位信号，所述第一开关单元的第二信号端与初始化电压相连接；所述第二开关单元的控制端用于输入扫描信号，所述第二开关单元的第二信号端与所述第三开关单元的第一信号端相连接；所述第三开关单元的第二信号端用于输入数据信号；第四开关单元的控制端用于输入发光信号；第五开关单元的控制端用于输入复位信号，所述第五开关单元的第一信号端与初始化电压相连接，所述第五开关单元的第二信号端与所述发光器件的第一端相连接；其中，所述驱动单元的信号输入端与所述存储电容的第二端以及第一电压相连接，所述驱动单元的驱动端与所述第四开关单元的第一信号端相连接，所述第四开关单元的第二信号端与所述发光器件的第一端相连接；或者，所述第四开关单元的第一信号端与所述存储电容的第二端以及第一电压相连接，所述第四开关单元的第二信号端与所述驱动单元的信号输入端相连接，所述驱动单元的驱动端与所述发光器件的第一端相连接；所述发光器件的第二端与第二电压相连接。
在本公开实施例提供的像素驱动电路中，驱动单元的控制端与存储电容的第一端、第一开关单元的第一信号端、第二开关单元的第一信号端、以及第三开关单元的控制端相连接；所述第一开关单元的控制端用于输入复位信号，所述第一开关单元的第二信号端与初始化电压相连接；所述第二开关单元的控制端用于输入扫描信号，所述第二 开关单元的第二信号端与所述第三开关单元的第一信号端相连接；所述第三开关单元的第二信号端用于输入数据信号；第四开关单元的控制端用于输入发光信号；第五开关单元的控制端用于输入复位信号，所述第五开关单元的第一信号端与初始化电压相连接，所述第五开关单元的第二信号端与所述发光器件的第一端相连接。利用本公开实施例提供的像素驱动电路，在所述发光器件发光之前，数据信号电压和所述第三开关单元的阈值电压之和能够被写入所述驱动单元的控制端，由此消除驱动单元阈值电压的变化对于发光的影响；并且还可以使用相对小的存储电容来实现电路结构。同时，可以利用第五开关单元来初始化发光器件的第一端，使得发光器件两端的跨压在发光之前能够被调整为例如零。在实现较低灰阶的暗态显示时，驱动单元产生的漏电流可以通过所述第五开关单元的第一信号端流出；因此，漏电流不会流至所述发光器件，使得所述发光器件能够准确地展现暗态，从而增加显示的对比度。本公开实施例利用一个存储电容、一个驱动单元和五个开关单元来实现驱动电路，能够获得更小的像素布局，其有助于提高显示的分辨率；并且提高了像素在暗态时的显示效果，增加了对比度。
可选地，所述驱动单元和五个开关单元均为薄膜晶体管；每个开关单元的控制端和所述驱动单元的控制端均是薄膜晶体管的栅极；每个开关单元的第一信号端和第二信号端分别是薄膜晶体管的源极和漏极，或者，每个开关单元的第一信号端和第二信号端分别是薄膜晶体管的漏极和源极；所述驱动单元的信号输入端和驱动端分别是薄膜晶体管的源极和漏极，或者，所述驱动单元的信号输入端和驱动端分别是薄膜晶体管的漏极和源极。
利用本公开实施例提供的像素驱动电路，在所述发光器件发光之前，数据信号电压和用作所述第三开关单元的薄膜晶体管阈值电压之和能够被写入用作所述驱动单元的薄膜晶体管的栅极，由此消除用作所述驱动单元的薄膜晶体管的阈值电压的变化对于发光的影响；并且还可以使用相对小的存储电容来实现电路结构。本公开实施例利用一个存储电容和六个薄膜晶体管来实现驱动电路，能够获得更小的像素布局，其有助于提高显示的分辨率。
可选地，所述驱动单元和五个开关单元均为P型薄膜晶体管。或者，所述驱动单元和五个开关单元均为N型薄膜晶体管。
本公开所有实施例中采用的开关单元和驱动单元均可以为薄膜晶体管或场效应管或其他特性相同的器件。薄膜晶体管的源极、漏极是对称的，所以其源极、漏极是可以互换的。在本公开实施例中，为区分薄膜晶体管除栅极之外的两极，将其中一极称为源极，另一极称为漏极。按附图中的形态规定薄膜晶体管的中间端为栅极、信号输入端为源极、信号输出端为漏极。P型薄膜晶体管在栅极为低电压时导通，在栅极为高电压时截止，N型薄膜晶体管为在栅极为高电压时导通，在栅极为低电压时截止。对于用作驱动单元的P型薄膜晶体管，在栅极电压为低电压(栅极电压小于源极电压)，且栅极源极的压差的绝对值大于阈值电压时处于放大状态或饱和状态；对于用作驱动单元的N型薄膜晶体管，在栅极电压为高电压(栅极电压大于源极电压)，且栅极源极的压差的绝对值大于阈值电压时处于放大状态或饱和状态。
可选地，所述驱动单元和所述第三开关单元是具有相同规格的薄膜晶体管。
具有相同规格的薄膜晶体管的阈值电压值具有相同的变化趋势。也就是说，用作第三开关单元的薄膜晶体管的阈值电压Vth3与用作驱动单元的薄膜晶体管的阈值电压Vthd是基本相等的。因此，用作第三开关单元的薄膜晶体管可以将数据线电压与其阈值电压之和(Vdata+Vth3)写入存储电容的第一端，从而消除所述驱动单元的阈值电压Vthd对于驱动电流的影响。
可选地，所述发光器件是有机发光二极管。
根据本公开的另一个方面，本公开实施例还提供了一种显示基板。所述显示基板包括如以上实施例所述的像素驱动电路。
根据本公开的又一个方面，本公开实施例提供了一种显示装置。所述显示装置包括如以上实施例所述的像素驱动电路。
根据本公开的另一个方面，本公开实施例提供了一种用于以上所述的像素驱动电路的驱动方法。所述驱动方法包括：第一阶段，导通所述第一开关单元的第一信号端和第二信号端，利用所述初始化电压为所述存储电容充电；导通所述第五开关单元的第一信号端和第二信号端，利用所述初始化电压初始化所述发光器件的第一端；第二阶段， 导通所述第二开关单元的第一信号端和第二信号端，利用所述数据信号、经由所述第三开关单元的第二信号端和控制端为所述存储电容充电；以及第三阶段，导通所述第四开关单元的第一信号端和第二信号端，利用所述驱动单元驱动所述发光器件。
利用本公开实施例提供的像素驱动电路的驱动方法，在所述发光器件发光之前，数据信号电压和所述第三开关单元的阈值电压之和能够被写入所述驱动单元的控制端，由此消除驱动单元阈值电压的变化对于发光的影响；并且还可以使用相对小的存储电容来实现电路结构。同时，可以利用第五开关单元来初始化发光器件的第一端，使得发光器件两端的跨压在发光之前能够被调整为例如零。在实现较低灰阶的暗态显示时，驱动单元产生的漏电流可以通过所述第五开关单元的第一信号端流出；因此，漏电流不会流至所述发光器件，使得所述发光器件能够准确地展现暗态，从而增加显示的对比度。本公开实施例利用一个存储电容、一个驱动单元和五个开关单元来实现驱动电路，能够获得更小的像素布局，其有助于提高显示的分辨率；并且提高了像素在暗态时的显示效果，增加了对比度。
可选地，所述驱动单元是薄膜晶体管；在所述第三阶段，用作所述驱动单元的薄膜晶体管处于饱和状态。
当用作驱动单元的薄膜晶体管处在饱和状态时，其输出的电流为：
Figure PCTCN2017079241-appb-000001
由以上公式可知驱动电流IOLED只和数据信号电压Vdata值有关系，因此驱动电流不受用作驱动单元的薄膜晶体管的阈值电压Vthd的影响。其中，VGS为薄膜晶体管的栅极和源极之间的电压，β＝μCoxW/L，μ、Cox为工艺常数，W为薄膜晶体管的沟道宽度，L为薄膜晶体管的沟道长度，W、L都为可选择性设计的常数。此时，由于Vth3≈Vthd，因此发光器件OLED上的电流与用作驱动单元的薄膜晶体管的阈值电压Vthd无关。
利用本公开实施例提供的像素驱动电路，在所述发光器件发光之前，数据信号电压和所述第三开关单元的阈值电压之和能够被写入所述驱动单元的控制端，由此消除驱动单元阈值电压的变化对于发光的影响；并且还可以使用相对小的存储电容来实现电路结构。本公开实 施例利用一个存储电容、一个驱动单元和五个开关单元来实现驱动电路，能够获得更小的像素布局，其有助于提高显示的分辨率。
附图说明
图1示出了现有技术的一种像素驱动电路结构示意图；
图2示出了本公开实施例提供的一种像素驱动电路的结构示意图；
图3示出了本公开另一实施例提供的一种像素驱动电路的结构示意图；
图4示出了本公开又一实施例提供的一种像素驱动电路的结构示意图；
图5示出了本公开另一实施例提供的一种像素驱动电路的结构示意图；
图6示出了本公开实施例提供的一种显示基板的结构示意图；
图7示出了本公开实施例提供的一种显示装置的结构示意图；
图8示出了本公开实施例提供的像素驱动电路的驱动方法的流程图；以及
图9示出了本公开实施例提供的像素驱动电路的输入信号时序状态示意图。
具体实施方式
下面将结合本公开实施例中的附图，对本公开实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅仅是本公开一部分实施例，而不是全部的实施例。基于本公开中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本公开专利保护的范围。
如图2所示，根据本公开的一个方面，本公开实施例提供了一种像素驱动电路。所述像素驱动电路包括：发光器件L、存储电容Cst、驱动单元D和五个开关单元S1、S2、S3、S4和S5；每个开关单元包括控制端、第一信号端和第二信号端；所述开关单元的控制端用于开启或关闭所述第一信号端和第二信号端之间的导通；所述驱动单元D包括控制端D3、信号输入端D1和驱动端D2，所述驱动单元D的控制端D3和信号输入端D1用于控制在驱动端D2输出的驱动信号；所述 驱动单元D的控制端D3与所述存储电容Cst的第一端C1、第一开关单元S1的第一信号端101、第二开关单元S2的第一信号端201、以及第三开关单元S3的控制端303相连接；所述第一开关单元S1的控制端103用于输入复位信号Reset，所述第一开关单元S1的第二信号端102与初始化电压Vint相连接；所述第二开关单元S2的控制端203用于输入扫描信号Gate，所述第二开关单元S2的第二信号端202与所述第三开关单元S3的第一信号端301相连接；所述第三开关单元S3的第二信号端302用于输入数据信号Data；第四开关单元S4的控制端403用于输入发光信号EM；第五开关单元S5的控制端503用于输入复位信号Reset，所述第五开关单元S5的第一信号端501与初始化电压Vint相连接，所述第五开关单元S5的第二信号端502与所述发光器件L的第一端L1相连接；其中，所述驱动单元D的信号输入端D1与所述存储电容Cst的第二端C2以及第一电压VDD相连接，所述驱动单元D的驱动端D2与所述第四开关单元S4的第一信号端401相连接，所述第四开关单元S4的第二信号端402与所述发光器件L的第一端L1相连接；所述发光器件L的第二端L2与第二电压VSS相连接。
或者，如图4所示，所述第四开关单元S4的第一信号端401与所述存储电容Cst的第二端C2以及第一电压VDD相连接，所述第四开关单元S4的第二信号端402与所述驱动单元D的信号输入端D1相连接，所述驱动单元D的驱动端D2与所述发光器件L的第一端L1相连接。
在本公开实施例提供的像素驱动电路中，驱动单元的控制端与存储电容的第一端、第一开关单元的第一信号端、第二开关单元的第一信号端、以及第三开关单元的控制端相连接；所述第一开关单元的控制端用于输入复位信号，所述第一开关单元的第二信号端与初始化电压相连接；所述第二开关单元的控制端用于输入扫描信号，所述第二开关单元的第二信号端与所述第三开关单元的第一信号端相连接；所述第三开关单元的第二信号端用于输入数据信号；第四开关单元的控制端用于输入发光信号；第五开关单元的控制端用于输入复位信号，所述第五开关单元的第一信号端与初始化电压相连接，所述第五开关单元的第二信号端与所述发光器件的第一端相连接。利用本公开实施例提供的像素驱动电路，在所述发光器件发光之前，数据信号电压和 所述第三开关单元的阈值电压之和能够被写入所述驱动单元的控制端，由此消除驱动单元阈值电压的变化对于发光的影响；并且还可以使用相对小的存储电容来实现电路结构。同时，可以利用第五开关单元来初始化发光器件的第一端，使得发光器件两端的跨压在发光之前能够被调整为例如零。在实现较低灰阶的暗态显示时，驱动单元产生的漏电流可以通过所述第五开关单元的第一信号端流出；因此，漏电流不会流至所述发光器件，使得所述发光器件能够准确地展现暗态，从而增加显示的对比度。本公开实施例利用一个存储电容、一个驱动单元和五个开关单元来实现驱动电路，能够获得更小的像素布局，其有助于提高显示的分辨率；并且提高了像素在暗态时的显示效果，增加了对比度。
可选地，如图3和5所示，所述发光器件可以是有机发光二极管OLED；所述驱动单元DTFT和五个开关单元T1、T2、T3、T4和T5均为薄膜晶体管；每个开关单元的控制端和所述驱动单元的控制端均是薄膜晶体管的栅极；每个开关单元的第一信号端和第二信号端分别是薄膜晶体管的源极和漏极，或者，每个开关单元的第一信号端和第二信号端分别是薄膜晶体管的漏极和源极；所述驱动单元DTFT的信号输入端和驱动端分别是薄膜晶体管的源极和漏极，或者，所述驱动单元DTFT的信号输入端和驱动端分别是薄膜晶体管的漏极和源极。
利用本公开实施例提供的像素驱动电路，在所述发光器件发光之前，数据信号电压Vdata和用作所述第三开关单元T3的薄膜晶体管阈值电压Vth3之和能够被写入用作所述驱动单元DTFT的薄膜晶体管的栅极，由此消除用作所述驱动单元DTFT的薄膜晶体管的阈值电压的变化对于发光的影响；并且还可以使用相对小的存储电容Cst来实现电路结构。本公开实施例利用一个存储电容和六个薄膜晶体管来实现驱动电路，能够获得更小的像素布局，其有助于提高显示的分辨率。
可选地，所述驱动单元和五个开关单元均为P型薄膜晶体管。或者，所述驱动单元和五个开关单元均为N型薄膜晶体管。
本公开所有实施例中采用的开关单元和驱动单元均可以为薄膜晶体管或场效应管或其他特性相同的器件。薄膜晶体管的源极、漏极是对称的，所以其源极、漏极是可以互换的。在本公开实施例中，为区分薄膜晶体管除栅极之外的两极，将其中一极称为源极，另一极称为 漏极。按附图中的形态规定薄膜晶体管的中间端为栅极、信号输入端为源极、信号输出端为漏极。P型薄膜晶体管在栅极为低电压时导通，在栅极为高电压时截止，N型薄膜晶体管为在栅极为高电压时导通，在栅极为低电压时截止。对于用作驱动单元的P型薄膜晶体管，在栅极电压为低电压(栅极电压小于源极电压)，且栅极源极的压差的绝对值大于阈值电压时处于放大状态或饱和状态；对于用作驱动单元的N型薄膜晶体管，在栅极电压为高电压(栅极电压大于源极电压)，且栅极源极的压差的绝对值大于阈值电压时处于放大状态或饱和状态。
可选地，所述驱动单元DTFT和所述第三开关单元T3是具有相同规格的薄膜晶体管。
具有相同规格的薄膜晶体管的阈值电压值具有相同的变化趋势。也就是说，用作第三开关单元的薄膜晶体管的阈值电压Vth3与用作驱动单元的薄膜晶体管的阈值电压Vthd是基本相等的。因此，用作第三开关单元的薄膜晶体管可以将数据线电压与其阈值电压之和(Vdata+Vth3)写入存储电容的第一端，从而消除所述驱动单元的阈值电压Vthd对于驱动电流的影响。
根据本公开的另一个方面，本公开实施例还提供了一种显示基板。如图6所示，所述显示基板600包括如以上实施例所述的像素驱动电路601。当然，所述显示基板600还可以包括用于支撑所述像素驱动电路的衬底基板、栅线、数据线等元件，在此不做限定。
根据本公开的又一个方面，本公开实施例提供了一种显示装置。如图7所示，所述显示装置700包括如以上实施例所述的像素驱动电路。
根据本公开的另一个方面，本公开实施例提供了一种用于以上所述的像素驱动电路的驱动方法。如图8所示，所述驱动方法包括：第一阶段801，导通所述第一开关单元的第一信号端和第二信号端，利用所述初始化电压为所述存储电容充电；导通所述第五开关单元的第一信号端和第二信号端，利用所述初始化电压初始化所述发光器件的第一端；第二阶段802，导通所述第二开关单元的第一信号端和第二信号端，利用所述数据信号、经由所述第三开关单元的第二信号端和控制端为所述存储电容充电；以及第三阶段803，导通所述第四开关单元的第一信号端和第二信号端，利用所述驱动单元驱动所述发光器件。
利用本公开实施例提供的像素驱动电路的驱动方法，在所述发光器件发光之前，数据信号电压和所述第三开关单元的阈值电压之和能够被写入所述驱动单元的控制端，由此消除驱动单元阈值电压的变化对于发光的影响；并且还可以使用相对小的存储电容来实现电路结构。同时，可以利用第五开关单元来初始化发光器件的第一端，使得发光器件两端的跨压在发光之前能够被调整为例如零。在实现较低灰阶的暗态显示时，驱动单元产生的漏电流可以通过所述第五开关单元的第一信号端流出；因此，漏电流不会流至所述发光器件，使得所述发光器件能够准确地展现暗态，从而增加显示的对比度。本公开实施例利用一个存储电容、一个驱动单元和五个开关单元来实现驱动电路，能够获得更小的像素布局，其有助于提高显示的分辨率；并且提高了像素在暗态时的显示效果，增加了对比度。
可选地，所述驱动单元是薄膜晶体管；在所述第三阶段，用作所述驱动单元的薄膜晶体管处于饱和状态。
当用作驱动单元的薄膜晶体管处在饱和状态时，其输出的电流为：
Figure PCTCN2017079241-appb-000002
由以上公式可知驱动电流IOLED只和数据信号电压Vdata值有关系，因此驱动电流不受用作驱动单元的薄膜晶体管的阈值电压Vthd的影响。其中，VGS为薄膜晶体管的栅极和源极之间的电压，β＝μCoxW/L，μ、Cox为工艺常数，W为薄膜晶体管的沟道宽度，L为薄膜晶体管的沟道长度，W、L都为可选择性设计的常数。此时，由于Vth3≈Vthd，因此发光器件OLED上的电流与用作驱动单元的薄膜晶体管的阈值电压Vthd无关。
具体地，参照图3所示的电路布局和图9所示的像素驱动电路的输入信号时序，说明本公开实施例提供的像素驱动电路的工作原理。尽管在图3和图5所示的像素驱动电路中，使用的是P型晶体管，简单更换晶体管的类型时只需要相应的调整相应的栅极电压即可。本公开实施例对各个薄膜晶体管的类型不做限制。当各个薄膜晶体管的类型改变时，只需调整薄膜晶体管栅极施加的电压信号即可，这里以能够实现本公开实施例提供的像素电路的驱动方法为准。本领域技术人 员在本公开实施例提供的像素驱动电路和驱动方法的基础上可轻易想到并实现的任意组合均在本公开的保护范围内。
在第一阶段t1，复位信号Reset为低电压，导通第一开关单元T1的源极和漏极，利用初始化电压Vint为存储电容Cst充电；导通第五开关单元T5的源极和漏极，利用所述初始化电压Vint初始化发光器件OLED的第一端L1。此时所述驱动单元DTFT的栅极的电位为初始化电压Vint。
在第二阶段t2，扫描信号Gate为低电压，导通第二开关单元T2的源极和漏极，第三开关单元T3此时呈现二极管状态，利用所述数据信号、经由第三开关单元T3的源极和栅极为所述存储电容Cst充电。此时所述驱动单元DTFT的栅极的电位为数据信号电压Vdata和第三开关单元T3的阈值电压Vth3之和。
在第三阶段t3，发光信号EM为低电压，导通第四开关单元T4的源极和漏极，利用所述驱动单元DTFT驱动发光器件OLED。由于已经在第二阶段在所述驱动单元DTFT的栅极上补偿了驱动单元DTFT的阈值电压，根据上述公式，OLED的驱动电流IOLED与数据信号电压Vdata有关，而与所述驱动单元DTFT的阈值电压无关。
类似地，也可以将图9所示的像素驱动电路的输入信号时序应用于图5所示的电路布局，此处不再赘述。
利用本公开实施例提供的像素驱动电路，在所述发光器件发光之前，数据信号电压和所述第三开关单元的阈值电压之和能够被写入所述驱动单元的控制端，由此消除驱动单元阈值电压的变化对于发光的影响；并且还可以使用相对小的存储电容来实现电路结构。同时，可以利用第五开关单元来初始化发光器件的第一端，使得发光器件两端的跨压在发光之前能够被调整为例如零。在实现较低灰阶的暗态显示时，驱动单元产生的漏电流可以通过所述第五开关单元的第一信号端流出；因此，漏电流不会流至所述发光器件，使得所述发光器件能够准确地展现暗态，从而增加显示的对比度。本公开实施例利用一个存储电容、一个驱动单元和五个开关单元来实现驱动电路，能够获得更小的像素布局，其有助于提高显示的分辨率；并且提高了像素在暗态时的显示效果，增加了对比度。
显然，本领域的技术人员可以对本公开进行各种改动和变型而不脱离本公开的精神和范围。这样，倘若本公开的这些修改和变型属于本公开权利要求及其等同技术的范围之内，则本公开也意图包含这些改动和变型。

Claims (20)

  1. 一种像素驱动电路，包括：发光器件、存储电容、驱动单元和五个开关单元；每个开关单元包括控制端、第一信号端和第二信号端；所述开关单元的控制端用于开启或关闭所述第一信号端和第二信号端之间的导通；所述驱动单元包括控制端、信号输入端和驱动端，所述驱动单元的控制端和信号输入端用于控制在驱动端输出的驱动信号；
    所述驱动单元的控制端与所述存储电容的第一端、第一开关单元的第一信号端、第二开关单元的第一信号端、以及第三开关单元的控制端相连接；
    所述第一开关单元的控制端用于输入复位信号，所述第一开关单元的第二信号端与初始化电压相连接；
    所述第二开关单元的控制端用于输入扫描信号，所述第二开关单元的第二信号端与所述第三开关单元的第一信号端相连接；
    所述第三开关单元的第二信号端用于输入数据信号；
    第四开关单元的控制端用于输入发光信号；
    第五开关单元的控制端用于输入复位信号，所述第五开关单元的第一信号端与初始化电压相连接，所述第五开关单元的第二信号端与所述发光器件的第一端相连接；
    其中，所述驱动单元的信号输入端与所述存储电容的第二端以及第一电压相连接，所述驱动单元的驱动端与所述第四开关单元的第一信号端相连接，所述第四开关单元的第二信号端与所述发光器件的第一端相连接；或者，所述第四开关单元的第一信号端与所述存储电容的第二端以及第一电压相连接，所述第四开关单元的第二信号端与所述驱动单元的信号输入端相连接，所述驱动单元的驱动端与所述发光器件的第一端相连接；
    所述发光器件的第二端与第二电压相连接。
  2. 如权利要求1所述的像素驱动电路，其中所述驱动单元和五个开关单元均为薄膜晶体管；
    每个开关单元的控制端和所述驱动单元的控制端均是薄膜晶体管的栅极；
    每个开关单元的第一信号端和第二信号端分别是薄膜晶体管的源极和漏极；或者，每个开关单元的第一信号端和第二信号端分别是薄膜晶体管的漏极和源极；
    所述驱动单元的信号输入端和驱动端分别是薄膜晶体管的源极和漏极；或者，所述驱动单元的信号输入端和驱动端分别是薄膜晶体管的漏极和源极。
  3. 如权利要求2所述的像素驱动电路，其中所述驱动单元和五个开关单元均为P型薄膜晶体管。
  4. 如权利要求2所述的像素驱动电路，其中所述驱动单元和五个开关单元均为N型薄膜晶体管。
  5. 如权利要求1-4任一项所述的像素驱动电路，其中所述驱动单元和所述第三开关单元是具有相同规格的薄膜晶体管。
  6. 如权利要求1-4任一项所述的像素驱动电路，其中所述发光器件是有机发光二极管。
  7. 一种显示基板，包括如权利要求1所述的像素驱动电路。
  8. 如权利要求7所述的显示基板，其中所述驱动单元和五个开关单元均为薄膜晶体管；
    每个开关单元的控制端和所述驱动单元的控制端均是薄膜晶体管的栅极；
    每个开关单元的第一信号端和第二信号端分别是薄膜晶体管的源极和漏极；或者，每个开关单元的第一信号端和第二信号端分别是薄膜晶体管的漏极和源极；
    所述驱动单元的信号输入端和驱动端分别是薄膜晶体管的源极和漏极；或者，所述驱动单元的信号输入端和驱动端分别是薄膜晶体管的漏极和源极。
  9. 如权利要求8所述的显示基板，其中所述驱动单元和五个开关单元均为P型薄膜晶体管。
  10. 如权利要求8所述的显示基板，其中所述驱动单元和五个开关单元均为N型薄膜晶体管。
  11. 如权利要求7-10任一项所述的显示基板，其中所述驱动单元和所述第三开关单元是具有相同规格的薄膜晶体管。
  12. 如权利要求7-10任一项所述的显示基板，其中所述发光器件是有机发光二极管。
  13. 一种显示装置，包括如权利要求1所述的像素驱动电路。
  14. 如权利要求13所述的显示装置，其中所述驱动单元和五个开关单元均为薄膜晶体管；
    每个开关单元的控制端和所述驱动单元的控制端均是薄膜晶体管的栅极；
    每个开关单元的第一信号端和第二信号端分别是薄膜晶体管的源极和漏极；或者，每个开关单元的第一信号端和第二信号端分别是薄膜晶体管的漏极和源极；
    所述驱动单元的信号输入端和驱动端分别是薄膜晶体管的源极和漏极；或者，所述驱动单元的信号输入端和驱动端分别是薄膜晶体管的漏极和源极。
  15. 如权利要求14所述的显示装置，其中所述驱动单元和五个开关单元均为P型薄膜晶体管。
  16. 如权利要求14所述的显示装置，其中所述驱动单元和五个开关单元均为N型薄膜晶体管。
  17. 如权利要求13-16任一项所述的显示装置，其中所述驱动单元和所述第三开关单元是具有相同规格的薄膜晶体管。
  18. 如权利要求13-16任一项所述的显示装置，其中所述发光器件是有机发光二极管。
  19. 一种用于如权利要求1-6任一项所述的像素驱动电路的驱动方法，包括：
    第一阶段，导通所述第一开关单元的第一信号端和第二信号端，利用所述初始化电压为所述存储电容充电；导通所述第五开关单元的第一信号端和第二信号端，利用所述初始化电压初始化所述发光器件的第一端；
    第二阶段，导通所述第二开关单元的第一信号端和第二信号端，利用所述数据信号、经由所述第三开关单元的第二信号端和控制端为所述存储电容充电；以及
    第三阶段，导通所述第四开关单元的第一信号端和第二信号端，利用所述驱动单元驱动所述发光器件。
  20. 如权利要求19所述的驱动方法，其中所述驱动单元是薄膜晶体管；在所述第三阶段，用作所述驱动单元的薄膜晶体管处于饱和状态。
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