Classifications

• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
  • H10K59/10—OLED displays
  • H10K59/12—Active-matrix OLED [AMOLED] displays
  • H10K59/121—Active-matrix OLED [AMOLED] displays characterised by the geometry or disposition of pixel elements
  • H10K59/1213—Active-matrix OLED [AMOLED] displays characterised by the geometry or disposition of pixel elements the pixel elements being TFTs
• • 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]
• • 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
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
  • H05B45/60—Circuit arrangements for operating LEDs comprising organic material, e.g. for operating organic light-emitting diodes [OLED] or polymer light-emitting diodes [PLED]
• • 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
  • 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
  • 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
  • G09G2300/088—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 using a non-linear two-terminal element

Definitions

• the present invention relates to the field of display technologies, and in particular, to a pixel circuit, a driving method thereof, and a display device.
• An Organic Light Emitting Diode is a current-driven active light-emitting device that has the unique advantages of self-illumination, fast response, wide viewing angle, and fabrication on a flexible substrate.
• the OLED-based organic light-emitting display is expected to become the mainstream in the display field in the next few years.
• Each display unit of the organic light emitting display is composed of an OLED.
• the OLED can be divided into a passive matrix driving organic light emitting diode (PMOLED) and an active matrix driving organic light emitting diode (Active Matrix Driving). OLED, AMOLED).
• PMOLED passive matrix driving organic light emitting diode
• Active Matrix Driving Active Matrix Driving
• the active matrix driving method is widely used in large information display because it can realize high quality display.
• each OLED has a Thin Film Transistor (TFT) circuit to control the current flowing through the OLED, and the OLED and the TFT circuit for driving the OLED constitute a pixel circuit, thereby ensuring active organic light emission.
• TFT Thin Film Transistor
• the uniformity of the brightness of the display panel requires consistency in the characteristics of the TFTs for driving the OLEDs located in different regions of the backplane.
• the threshold voltage of a TFT is related to many factors, including the doping of the first pole of the TFT, the thickness of the dielectric, the gate material, and the excess charge in the dielectric.
• the threshold voltage offset of each TFT is inconsistent; Problems such as decreased TFT stability may also cause the threshold voltage offset of the TFT to be inconsistent, and the inconsistent threshold voltage offset of the TFT may cause a difference in current flowing through each OLED, thereby causing the OLED to be driven by the current to emit light. Poor hooking.
• Embodiments of the present invention provide a pixel circuit, a driving method thereof, and a display device, which effectively improve the uniformity of the luminance of the light emitting device.
• the embodiments of the present invention provide the following technical solutions:
• a pixel circuit comprising:
• a light emitting device a driving tube, a storage capacitor, a first switching tube, a second switching tube, a compensation tube, and a fifth switching tube;
• the driving tube, the first switching tube, the second switching tube, the compensation tube, and the fifth switching tube each include a gate, a first pole and a second pole;
• One end of the light emitting device is connected to a power source
• a first pole of the driving tube is connected to the other end of the light emitting device, a second pole is connected to the first pole of the fifth switching tube, and a gate is connected to the first pole of the first switching tube;
• the second pole of the first switch tube is connected to the data line, the gate is connected to the scan line, and the first pole is connected to the gate of the drive tube;
• the gate of the second switch tube is connected to the control line, the first pole is connected to the power source, and the second pole is connected to the second pole of the compensation tube;
• the first pole of the compensating tube is connected to the first pole of the driving tube
• the second pole is connected to the second pole of the second switching tube
• the gate and the first pole or the second pole of the compensating tube Connected
• the gate of the fifth switch tube is connected to the control line, the first pole is connected to the second pole of the drive tube, and the second pole is connected to the ground;
• the first plate of the storage capacitor is connected to the gate of the drive tube, and the second plate is connected to the second pole of the compensation tube.
• a driving method for the pixel circuit comprising:
• a display device includes a pixel circuit provided by an embodiment of the present invention.
• the pixel circuit, the driving method thereof and the display device provided by the embodiment of the invention enable the switching of the circuit and the charging and discharging control of the circuit by the compensation tube, the capacitor and the plurality of switching tubes, so that the voltage across the compensation tube can also act on the driving tube, thereby enabling
• the drive current of the drive tube is independent of the threshold voltage of the drive tube.
• the difference in current flowing through the light emitting device due to the inconsistency or offset of the threshold voltage of the driving tube is compensated, so that the uniformity of the light emitting luminance of the light emitting device can be effectively improved.
• FIG. 1 is a circuit diagram of a pixel circuit according to an embodiment of the present invention.
• FIG. 2 is a timing chart of each signal line when the pixel circuit shown in FIG. 1 is driven;
• FIG. 3 is a schematic diagram of an equivalent circuit of the pixel circuit shown in FIG. 1 in a compensation phase
• FIG. 4 is a schematic diagram of an equivalent circuit of the pixel circuit of the first embodiment of the present invention
• FIG. 5 is a circuit diagram of another pixel circuit according to an embodiment of the present invention.
• FIG. 6 is a circuit diagram of another pixel circuit according to an embodiment of the present invention.
• FIG. 7 is a circuit diagram of another pixel circuit according to an embodiment of the present invention.
• FIG. 8 is a circuit diagram of another pixel circuit according to an embodiment of the present invention.
• FIG. 9 is an equivalent circuit diagram of the pixel circuit shown in FIG. 8 in a compensation phase
• FIG. 10 is a schematic diagram of an equivalent circuit of the pixel circuit of FIG. 8 in a transitional illumination phase
• FIG. 11 is a flow chart of a method for driving a pixel circuit according to an embodiment of the present invention.
• an embodiment of the present invention provides a pixel circuit, including:
• Light emitting device OLED driving transistor DTFT, storage capacitor Cst, first switching transistor T1, second The switch tube T2, the compensation tube ⁇ 3 and the fifth switch tube ⁇ 5.
• the driving transistor DTFT, the first switching transistor T1, the second switching transistor 2, the compensation transistor 3, and the fifth switching transistor 5 are all ⁇ -type thin film transistors, and each includes a source, a drain, and a gate.
• One end of the OLED is connected to the power supply VDD;
• a drain (first pole) of the driving transistor DTFT is connected to the other end of the light emitting device OLED, and a source (second pole) is connected to a drain (first pole) of the fifth switching transistor 5, a pole connected to a drain (first pole) of the first switching transistor T1;
• the source (second pole) of the first switch T1 is connected to the data line, the gate is connected to the scan line, and the drain (first pole) is connected to the gate of the drive transistor DTFT;
• the gate of the second switch T2 is connected to the control line, the drain (first pole) is connected to the power source VDD, and the source (second pole) is connected to the source (second pole) of the compensation tube T3;
• the gate of the compensation tube T3 is connected to the drain (first pole), the drain (first pole) is connected to the drain (first pole) of the driving transistor DTFT, and the source (second pole) and the The source (second pole) of the second switch tube T2 is connected;
• the gate of the fifth switching transistor T5 is connected to the control line, the drain (first pole) is connected to the source (second pole) of the driving transistor DTFT, and the source (second pole) is connected to the ground;
• the first plate of the storage capacitor Cst is connected to the gate of the drive transistor DTFT, and the second plate is connected to the source (second pole) of the compensation transistor T3.
• the compensation tube T3 is equivalent to a diode
• the drain (first pole) is connected to the gate and is equivalent to the anode of the diode, and is connected to the drain of the driving transistor DTFT (first pole) ), whose source is equivalent to the cathode of the diode, and is connected to the source (second pole) of the second switching transistor T2.
• the scan line, the control line, and the data line are respectively used to transmit different signals, wherein the scan line transmits the scan signal Vscan, the control line transmits the control signal EM, and the data line transmits the data signal. Vdata.
• Fig. 1 is a timing chart of each signal line when the pixel circuit shown in Fig. 1 is driven. As shown in Fig. 2, the compensation phase and the hopping illuminating phase are correspondingly represented by 1 and 2, respectively.
• the driving method of the pixel circuit shown in FIG. 1 is as follows:
• Phase 1 The compensation phase.
• the scan signal Vscan is at a high level
• the control signal EM is at a low level.
• the first switching transistor T1 is turned on according to the input scan signal Vscan, and the second switching transistor T2 and the fifth switching transistor T5 are turned off according to the control signal EM being at a low level.
• the compensation tube T3 is in a forward conduction state during the compensation phase.
• the pixel circuit shown in FIG. 1 can be equivalent to the circuit structure shown in FIG.
• the data signal Vdata can be input to the gate of the driving transistor DTFT through the first switching transistor T1, and the storage capacitor Cst is charged to input to the driving transistor.
• the data signal Vdata of the gate of the DTFT is maintained. After charging,
• the voltage at point A VA is equal to the data signal Vdata
• the voltage at point B is the power supply voltage.
• VDD minus the threshold voltage of the OLED.
• the Voth is subtracted from the threshold voltage Vth3 of the compensation tube T3.
• the second switching transistor T2 since the control signal EM input to the gate of the second switching transistor T2 is at a low level, the second switching transistor T2 is turned off, so that the storage capacitor Cst can be disconnected from the power supply VDD, and the OLED and the compensation of the light-emitting device are ensured.
• the data signal Vdata to the gate of the driving transistor DTFT is lost by the connection of the fifth switching transistor T5 to the ground GND.
• the second stage the transitional lighting stage.
• the scan signal Vscan is low and the control signal EM is high.
• the first switching transistor T1 is turned off according to the input scanning signal Vscan, and the second switching transistor T2 and the fifth switching transistor T5 are turned on according to the control signal EM being at a high level.
• the compensating tube T3 is in the reverse-off state during the hopping illumination phase.
• the pixel circuit shown in Fig. 1 can be equivalent to the circuit structure shown in Fig. 4.
• the scan signal Vscan input to the gate of the first switch transistor T1 is at a low level, and the first switch transistor T1 is turned off, so that the gate of the drive transistor DTFT is isolated from the data line, and the drive transistor DTFT is illuminated.
• the driving of the device OLED is not affected by the number of sources input to the first switching transistor T1. According to the influence of the change of signal Vdata.
• the control signal EM input to the gate of the fifth switching transistor T5 is at a high level, and the fifth switching transistor T5 is turned on, the source of the driving transistor DTFT is directly connected to the ground GND.
• the driving transistor DTFT operates in a saturated state, and the current I flowing through the source and the drain of the driving transistor DTFT, that is, the driving current I for driving the light emitting device OLED to emit light, the voltage Vgs between the gate and the source of the driving transistor DTFT Change and change, the specific relationship is shown in equation (5).
• the drive tube DTFT starts to drive the OLED to emit light.
• Vgs is the gate-source voltage of the driving transistor DTFT.
• K eff *Cox*(W/L)/2, where ⁇ ⁇ represents the carrier effective mobility of the DTFT, Cox represents the dielectric constant of the gate insulating layer of the driving transistor DTFT, and W/L represents the trench of the driving transistor DTFT
• the values of W, L, Cox, and ⁇ ⁇ are relatively stable in the same structure, so ⁇ can be considered as a constant.
• the current I flowing through the driving transistor DTFT is related to the data signal Vdata and the constant K, and also to the threshold voltage Vth3 of the compensation tube T3, the threshold voltage Vth of the driving transistor DTFT, and the width of the light emitting device OLED.
• the value voltage Voth is related.
• LTPS Low Temperature Poly-silicon
• the current I flowing through the driving transistor DTFT is only related to the data signal Vdata and the threshold voltage Voth of the light emitting device OLED.
• the driving current I is independent of the threshold voltage Vth of the driving transistor DTFT, thereby avoiding the threshold voltage bias of the driving transistor DTFT caused by the manufacturing process of the backplane and the long-time operation.
• the driving current I caused by the shift that is, the difference in current flowing through the light emitting device OLED, effectively improves the uniformity of the light emitting luminance of the light emitting device.
• the pixel circuit provided by the embodiment of the present invention can not only compensate for the difference of the driving current I due to the offset of the threshold voltage Vth of the driving transistor DTFT, but also, due to the driving current I and the light emission
• the Voth correlation of the OLED of the device OLED can also compensate for the difference in current flowing through the OLED of the OLED due to the high or low value of the threshold voltage Voth of the OLED of the OLED, thereby further improving the brightness of the illuminating device. Sex.
• the driving current I increases as the threshold voltage Voth of the light emitting device OLED increases, with the threshold voltage of the light emitting device OLED.
• the Voth is reduced by a decrease, so that when the OLED ages to cause the threshold voltage Voth to rise, the drive current I also rises accordingly to compensate for the decrease in the drive current I due to the rise of the threshold voltage Voth.
• the driving transistor DTFT does not drive the light emitting device OLED to emit light
• the light emitting device OLED is in the charging loop of the storage capacitor Cst, so the data signal Vdata is input to the driving transistor DTFT.
• the gate is charged to the storage capacitor Cst, the OLED still emits a certain amount of light.
• the driving transistor DTFT, the compensation transistor T3, and each of the switching transistors are ⁇ -type thin film transistors, but the present invention is not limited thereto.
• Each of the above-mentioned ⁇ -type thin film transistors may be replaced in whole or in part by a ⁇ -type thin film transistor as long as the following conditions are satisfied.
• the compensation tube 3 and the driving tube DTFT are the same type of thin film transistor, that is, the same type N or the same type P.
• the compensation tube T3 is used to provide a compensation voltage so that the drive current I of the drive transistor DTFT is independent of the turn-on voltage Vth of the drive transistor DTFT.
• Vth3 is equal to the turn-on voltage Vth of the driving transistor DTFT.
• the compensation tube T3 and the driving transistor DTFT need to have the same structure and close distance to meet the short-range order condition of the LTPS process.
• the second switching transistor T2 and the fifth switching transistor T5 are the same type of thin film transistor, that is, the same type N or the same P type. Since the second switch tube T2 and the fifth switch tube T5 need to be turned on or off at the same time, the on or off is controlled by the control signal EM on the control line.
• a signal input to the gate of the corresponding thin film transistor such as a scan signal Vscan input to the first switching transistor T1, a control signal EM input to the gates of the second switching transistor T2 and the fifth switching transistor T5, and an input
• the data signal Vdata to the gate of the drive transistor DTFT may need to be adjusted accordingly. The details are described below by way of specific examples.
• the pixel circuit includes:
• the driving transistor DTFT and the compensation transistor T3 are P-type thin film transistors
• the first switching transistor T1, the second switching transistor ⁇ 2, and the fifth switching transistor ⁇ 5 are all ⁇ -type thin film transistors, and each thin film transistor includes a source and a drain. And the gate.
• One end of the OLED is connected to the power supply VDD;
• a source (first pole) of the driving transistor DTFT is connected to the other end of the light emitting device OLED, and a drain (second pole) is connected to a drain (first pole) of the fifth switching transistor T5. a pole connected to a drain (first pole) of the first switching transistor T1;
• the source (second pole) of the first switch T1 is connected to the data line, the gate is connected to the scan line, and the drain (first pole) is connected to the gate of the drive transistor DTFT;
• the gate of the second switching transistor T2 is connected to the control line, the drain (first pole) is connected to the power source VDD, and the source (second pole) is connected to the drain (second pole) of the compensation tube T3;
• the gate of the compensation tube T3 is connected to the drain (second pole), the source (first pole) is connected to the source (first pole) of the driving transistor DTFT, and the drain (second pole) and the The source (second pole) of the second switch tube T2 is connected;
• a gate of the fifth switching transistor T5 is connected to the control line, a drain (first pole) is connected to a drain (second pole) of the driving transistor DTFT, and a source (second pole) is connected to the ground;
• the first plate of the storage capacitor Cst is connected to the gate of the driving tube DTFT, and the second plate is connected to the drain (second pole) of the compensation tube T3.
• the driving transistor DTFT is N-type, and the current I flowing through the source and the drain of the N-type driving transistor DTFT increases as the data signal Vdata increases, along with the data signal Vdata.
• the driving transistor DTFT is P-type, and the current I flowing through the source and the drain of the P-type driving transistor DTFT decreases as the data signal Vdata increases, along with the data.
• the signal Vdata is decreased by increasing. Therefore, the data signal Vdata in the embodiment shown in Fig. 1 may be different from the data signal Vdata in the present embodiment, corresponding to the same current I flowing through the driving transistor DTFT.
• the pixel circuit provided in this embodiment can achieve the same technical effect as the embodiment shown in FIG. 1 by replacing the N-type driving tube DTFT and the N-type compensation tube T3 with the corresponding P-type tube, and details are not described herein again. .
• FIG. 6 is still another circuit diagram of a pixel circuit according to an embodiment of the present invention.
• the present embodiment is different from the embodiment shown in Fig. 1 in that the second switching transistor T2 and the fifth switching transistor T5 are not N-type thin film transistors but P-type thin film transistors. Accordingly, the control signal EM input to the gate of the second switching transistor T2 and the gate of the fifth switching transistor T5 is also different from the embodiment shown in FIG.
• the pixel circuit provided in this embodiment includes: a light emitting device OLED, a driving transistor DTFT, a storage capacitor Cst, a first switching transistor T1, a second switching transistor T2, a compensation tube T3, and a fifth switching tube. T5.
• the driving transistor DTFT, the first switching transistor T1, and the compensation transistor ⁇ 3 are all ⁇ -type thin film transistors
• the second switching transistor ⁇ 2 and the fifth switching transistor ⁇ 5 are ⁇ -type thin film transistors
• each of the thin film transistors includes a source and a drain. Pole and gate.
• One end of the OLED is connected to the power supply VDD;
• a drain (first pole) of the driving transistor DTFT is connected to the other end of the light emitting device OLED, and a source (second pole) is connected to a source (first pole) of the fifth switching transistor T5.
• the source (second pole) of the first switch tube T1 is connected to the data line, the gate is connected to the scan line, and the drain (first pole) is connected to the gate of the drive tube DTFT;
• the gate of the second switching transistor T2 is connected to the control line, the source (first pole) is connected to the power source VDD, and the drain (second pole) is connected to the source (second pole) of the compensation tube T3;
• the gate of the compensation tube T3 is connected to the drain (first pole), the drain (first pole) is connected to the drain (first pole) of the driving transistor DTFT, and the source (second pole) and the The drain (second pole) of the two switching tubes T2 is connected;
• the gate of the fifth switching transistor T5 is connected to the control line, the source (first pole) is connected to the source (second pole) of the driving transistor DTFT, and the drain (second pole) is connected to the ground;
• the first plate of the storage capacitor Cst is connected to the gate of the drive transistor DTFT, and the second plate is connected to the source (second pole) of the compensation transistor T3.
• the working process of the pixel circuit is similar to the working process of the pixel circuit in the embodiment shown in FIG. 1, except that the control signal EM controls the opening or closing of the second switching transistor T2 and the fifth switching transistor T5, and The embodiment shown in 1 is different.
• the control signal EM is at a high level to turn off the second switching transistor T2 and the fifth switching transistor T5.
• the working process of the pixel circuit provided in this embodiment in the compensation phase is similar to the embodiment shown in Figures 1-4, and will not be described here.
• the control signal EM is at a low level to turn on the second switching transistor T2 and the fifth switching transistor T5. .
• the working process of the pixel circuit in the hopping illuminating stage is similar to the embodiment shown in FIG. 1-4, and details are not described herein again.
• the pixel circuit includes: a light emitting device OLED, a driving transistor DTFT, a storage capacitor Cst, a first switching transistor T1, a second switching transistor T2, a compensation tube T3, and a fifth Switch tube T5.
• the driving transistor DTFT, the compensation tube T3, the second switching transistor 2, and the fifth switching transistor ⁇ 5 are all ⁇ -type thin film transistors
• the first switching transistor T1 is a ⁇ -type thin film transistor
• each of the thin film transistors includes a source and a drain. Pole and gate.
• One end of the OLED is connected to the power supply VDD;
• the drain (first pole) of the driving transistor DTFT is connected to the other end of the light emitting device OLED, and the source (second pole) is connected to the drain (first pole) of the fifth switching transistor T5.
• the drain (second pole) of the first switch transistor T1 is connected to the data line, the gate is connected to the scan line, and the source (first pole) is connected to the gate of the drive transistor DTFT;
• the gate of the second switch T2 is connected to the control line, the drain (first pole) is connected to the power source VDD, and the source (second pole) is connected to the source (second pole) of the compensation tube T3;
• the gate of the compensation tube T3 is connected to the drain (first pole), the drain (first pole) is connected to the drain (first pole) of the driving transistor DTFT, and the source (second pole) and the The source (second pole) of the second switch tube T2 is connected;
• the gate of the fifth switching transistor T5 is connected to the control line, the drain (first pole) is connected to the source (second pole) of the driving transistor DTFT, and the source (second pole) is connected to the ground;
• the first plate of the storage capacitor Cst is connected to the gate of the drive transistor DTFT, and the second plate is connected to the source (second pole) of the compensation transistor T3.
• the operation of the pixel circuit is similar to the operation of the pixel circuit in the embodiment shown in FIG. 1, except that the scan signal Vscan controls the first switch tube T1 to be turned on or off, and in the embodiment shown in FIG.
• the pixel circuit is different.
• the scan signal Vscan is at a low level, thereby making the first switch tube
• T1 is turned on.
• the working process of the pixel circuit provided in this embodiment is similar to that of the embodiment shown in FIG. 1-4, and details are not described herein again.
• the scan signal Vscan is at a high level, thereby turning off the first switch.
• the working process of the pixel circuit in the hopping illuminating stage is similar to the embodiment shown in FIG. 1-4, and details are not described herein again.
• the thin film transistors of the pixel circuit provided by the present invention are all N-type, the driving transistor DTFT and the compensation transistor T3 are P-type, the other thin film transistors are N-type, and the second switching transistor T2 and the fifth switch are used.
• the tube T5 is of the P type
• the other thin film transistors are of the N type
• the case where the first switching transistor T1 is of the P type and the other thin film transistors are of the N type are described in detail.
• the present invention is not limited thereto.
• each of the above switching tubes, the driving tube DTFT, and the compensation tube T3 may also be P-type thin film transistors, or other forms of partial thin film transistors are P-type thin film transistors and A part of the thin film transistor is a combination of N-type thin film transistors, as long as the compensation transistor T3 and the driving transistor DTFT are the same type of thin film transistor, that is, the same type N or the same P type, and the second switching tube T2 and the fifth switching tube T5 It is just the same type of thin film transistor.
• connection method of each P-type thin film transistor in the circuit is similar to the connection method of the original N-type thin film transistor, only according to the gate, the drain and the source of the P-type tube and the N-type tube in the semiconductor physics knowledge.
• the connection relationship can be appropriately adjusted by the correspondence of the extreme potentials.
• each of the thin film transistors is an N-type thin film transistor, and the first poles of each thin film transistor are both drains and the second poles are all sources, in other embodiments of the present invention.
• connection relationship can still be described by the connection relationship between the first pole and the second pole of the thin film transistor in the embodiment shown in FIG. 1, but specifically, The one or the second pole represents the source or the drain of the thin film transistor, which may be different for different types of thin film transistors.
• the first pole thereof corresponds to the source of the P-type thin film transistor, and the second pole Corresponding to the drain of the P-type thin film transistor; for the compensation tube T3, since the gate is always connected to the drain, when T3 is an N-type thin film transistor, the gate and the drain of the T3 (first pole) Connected, when T3 is a P-type thin film transistor, the gate of T3 is connected to the drain (second pole).
• the compensation tube T3 is equivalent to a diode, and the drain is connected to the gate and is equivalent to one pole of the diode.
• the source is equivalent to the other pole of this diode.
• circuit structure provided by the embodiment of the present invention is similar to the embodiment shown in FIG. 1, except that each of the thin film transistors may be different in N type or P type, and correspondingly, in the circuit.
• the connection is also slightly adjusted, but no matter how it is changed, it can be ensured that the circuit functions of the compensation phase and the hopping illuminating phase in the above embodiment can be normally realized.
• the pixel circuit may further include a fourth switch tube T4. It should be noted that, in addition to the fourth switching transistor ,4, the pixel circuit in this embodiment is the same as the pixel circuit in the embodiment shown in FIG.
• the gate of the fourth switching transistor 4 is connected to the scan line, the drain (first pole) is connected to the drain (first pole) of the second switching transistor 2, and the source (second pole) and the driving transistor DTFT
• the drain (first pole) is connected, and the fourth switch transistor 4 is of the same type as the first switch transistor T1, that is, the same as a germanium thin film transistor or a germanium thin film transistor.
• the driving transistor DTFT, the storage capacitor Cst, the first switching transistor T1, the second switching transistor T2, the compensation tube T3 and the fifth switching transistor T5 please refer to the detailed description of the embodiment shown in FIG. I will not repeat them here.
• the working process of the pixel circuit in this embodiment will be described in detail below with reference to FIG. 2 and FIG. 8-10.
• Phase 1 The compensation phase.
• the scan signal Vscan is at a high level
• the control signal EM is at a low level.
• the pixel circuit shown in FIG. 8 can be equivalent to the circuit structure shown in FIG. 8 and FIG. 9, the first switching transistor T1 and the fourth switching transistor T4 are N-type thin film transistors, and the scanning signals Vscan input to the gates of the first switching transistor T1 and the fourth switching transistor T4 are at a high level, thereby The first switch tube T1 and the fourth switch tube T4 are turned on.
• the second switching transistor T2 and the fifth switching transistor T5 are also N-type thin film transistors, and the control signal EM input to their gates is at a low level, thereby turning off the second switching transistor T2 and the fifth switching transistor T5.
• the light emitting device OLED is short-circuited by the turned-on fourth switch tube T4. Therefore, unlike the embodiment shown in FIG. 1, in this embodiment, no current flows through the light at this stage.
• the device OLED the light emitting device OLED does not emit light.
• the data signal Vdata can be input to the gate of the drive transistor DTFT through the first switch T1 and held.
• the voltage VA at point A is the data signal Vdata.
• Point B voltage VB is the power supply voltage VDD minus the threshold voltage Vth3 of the compensation tube, ie
• the second switching transistor T2 disconnects the storage capacitor Cst from the power supply VDD according to the input low-level control signal EM, thereby ensuring the forward conduction of the compensation tube T3.
• the fifth switching transistor T5 disconnects the driving transistor DTFT from the ground GND according to the input low-level control signal EM, thereby preventing the data signal Vdata input to the gate of the driving transistor DTFT from passing through the fifth switching transistor T5 and the ground GND. The connection is lost.
• the second stage the transitional lighting stage.
• the scan signal Vscan is at a low level
• the control signal EM is at a high level.
• the pixel circuit shown in FIG. 8 can be equivalent to the circuit structure as shown in FIG.
• the first switching transistor T1 is turned off according to the input scan signal Vscan, so that the gate of the driving transistor DTFT and the source of the first switching transistor T1, that is, the input end of the data signal Vdata. isolation.
• the driving of the light-emitting device OLED by the driving transistor DTFT is not affected by the signal variation of the source of the first switching transistor T1.
• the fourth switching transistor T4 is turned off according to the input scanning signal Vscan, so that the driving transistor DTFT is no longer short-circuited, so that the light-emitting device OLED can be driven to emit light.
• the second switch T2 is turned on according to the control signal EM, the upper plate of the storage capacitor Cst is directly connected to the power supply VDD, and the voltage VB at the B point is instantaneously changed from Vdata to VDD. It is known from physics that the voltage between the two plates of the capacitor does not change instantaneously. Therefore, when the voltage at point B VB has just jumped to VDD, equation (11) still holds. Then, at this time, the voltage at point A is equal to the voltage at point B, VB, and the voltage VAB between point A and point B, that is,
• the fifth switching transistor T5 is turned on according to the control signal ⁇ , and the source of the driving transistor DTFT is directly connected to the ground GND. At this time, the driving tube DTFT starts to drive the OLED to emit light.
• the gate-source voltage of the driving transistor DTFT is
• the current flowing through the driving transistor DTFT is
• equation (14) can be expressed as:
• K has the same meaning as the foregoing embodiment, and can be considered as a constant here.
• the current flowing through the driving transistor DTFT is only related to the data signal Vdata, and is independent of the threshold voltage Vth of the driving transistor DTFT, thereby avoiding the threshold value of the driving transistor DTFT caused by the manufacturing process of the backplane and the long-time operation.
• the difference in current flowing through the light emitting device OLED caused by the voltage offset effectively improves the uniformity of the light emitting luminance of the light emitting device.
• the fourth switching transistor T4 short-circuits the light emitting device OLED in the compensation phase. That is, no current flows through the light-emitting device OLED during the compensation phase, and the light-emitting device OLED does not emit light, thereby avoiding the occurrence of flicker in the compensation phase of the light-emitting device OLED.
• the present invention is described by taking an OLED as an example.
• the illuminating device provided by the embodiment of the present invention may be another illuminating device capable of driving the pixel circuit in the embodiment of the present invention, and the present invention does not limit.
• each thin film transistor is an N-type thin film transistor
• the fourth switching transistor T4 is added thereto for explanation.
• each of the thin film transistors may be replaced in whole or in part as a P-type thin film transistor, and only the following conditions are satisfied: the compensation tube T3 and the driving transistor DTFT are the same type of thin film transistor, and the fourth switching tube T4 and
• the first switching transistor T1 is a thin film transistor of a type
• the second switching transistor T2 and the fifth switching transistor T5 may be the same type of thin film transistor.
• the same type of thin film transistor means an N-type thin film transistor or a P-type thin film transistor.
• an embodiment of the present invention further provides a driving method of a pixel circuit, including:
• the first switch tube T1 is turned on, and the second switch tube T2 and the fifth switch tube T5 are turned off, so that the data signal Vdata in the data line charges the first plate of the storage capacitor Cst through the first switch tube T1. And causing the power supply VDD to charge the second plate of the storage capacitor Cst through the light emitting device OLED and the compensation tube T3;
• the first switch tube T1 is turned off, and the second switch tube T2 and the fifth switch tube T5 are turned on, so that the light-emitting device OLED is sequentially supplied by the power source VDD through the light-emitting device OLED, the driving tube DTFT, and the fifth switch tube.
• the current of T5 drives the illumination.
• the driving method of the pixel circuit divides the driving of the pixel circuit into two stages by the compensation tube T3, the storage capacitor and the plurality of switching tubes for the switching and charging and discharging control of the circuit, thereby making the driving tube DTFT
• the driving current is independent of the threshold voltage Vth of the driving transistor DTFT, and compensates for the difference in current flowing through the light emitting device OLED due to the inconsistency or offset of the threshold voltage Vth of the driving transistor DTFT, thereby effectively improving the luminance of the light emitting device. Uniformity.
• the turn-on voltage Voth of the light-emitting device such as the OLED can also be added between the gate and the second pole of the driving transistor DTFT in the jump light-emitting phase, it is possible to compensate for the increase in the threshold voltage of the light-emitting device OLED.
• the difference in current flowing through the light emitting device OLED is an OLED, but the present invention is not limited thereto, and other illuminating devices that can be driven by the pixel circuit provided by the embodiment of the present invention may be used.
• the first switch tube T1, the second switch tube ⁇ 2, and the fifth switch tube ⁇ 5 are all ⁇ -type thin film transistors, and their first extreme drain and second extreme source .
• the driving method of the pixel circuit provided by the embodiment of the present invention can input the high level to the gate of the first switching transistor T1 through the scan line to turn on the first switching tube T1, and simultaneously input the low level through the control line.
• the gate of the second switch transistor 2 and the gate of the fifth switch transistor 5 turn off the second switch transistor 2 and the fifth switch transistor 5; correspondingly, for step S12, the low level can also be input to the first switch through the scan line.
• the gate of the tube T1 turns off the first switching transistor T1, and simultaneously inputs a high level through the control line to the gate of the second switching transistor ⁇ 2 and the gate of the fifth switching transistor ⁇ 5 to the second switching transistor ⁇ 2 and the fifth switching transistor ⁇ 5 is turned on.
• the first switch transistor T1 is a ⁇ -type thin film transistor having a first extreme drain and a second extreme source; the second switch transistor ⁇ 2 and the fifth switch transistor ⁇ 5 are both The first extreme source of the second switching transistor ⁇ 2 and the fifth switching transistor ,5, and the second extreme drain.
• the driving method of the pixel circuit provided by the embodiment of the present invention can input the high level to the gate of the first switching transistor T1 through the scan line to turn on the first switching transistor T1, and simultaneously input the high level through the control line.
• the gate of the second switch transistor 2 and the gate of the fifth switch transistor 5 turn off the second switch transistor 2 and the fifth switch transistor 5; correspondingly, for step S12, the low level can also be input to the first switch through the scan line.
• the gate of the tube T1 turns off the first switching transistor T1, and simultaneously inputs a low level through the control line to the gate of the second switching transistor ⁇ 2 and the gate of the fifth switching transistor ⁇ 5 to the second switching transistor ⁇ 2 and the fifth switching transistor ⁇ 5 is turned on.
• the first switching transistor T1 is a ⁇ -type thin film transistor, the first extreme source of the first switching transistor T1, the second extreme drain; the second switching transistor ⁇ 2 and the The five switching transistors ⁇ 5 are all ⁇ -type thin film transistors, and their first extreme drain and second extreme source.
• the driving method of the pixel circuit can input the low level to the gate of the first switching transistor T1 through the scan line to turn on the first switching transistor T1, and simultaneously input the low level through the control line.
• the gate of the second switch transistor 2 and the gate of the fifth switch transistor 5 turn off the second switch transistor 2 and the fifth switch transistor 5; correspondingly, for step S12, the high level can be input to the first switch transistor through the scan line.
• the gate of T1 turns off the first switching transistor T1, and simultaneously inputs a high level through the control line to the gate of the second switching transistor ⁇ 2 and the gate of the fifth switching transistor ⁇ 5 to the second switching transistor T2 and the fifth switching tube T5 are turned on.
• the first switch tube T1, the second switch tube ⁇ 2, and the fifth switch tube ⁇ 5 are all ⁇ -type thin film transistors.
• the driving method of the pixel circuit provided by the embodiment of the present invention can input the low level to the gate of the first switching transistor T1 through the scan line to turn on the first switching transistor T1, and simultaneously input the high level through the control line.
• the gate of the second switch transistor 2 and the gate of the fifth switch transistor 5 turn off the second switch transistor 2 and the fifth switch transistor 5; correspondingly, for step S12, the high level can be input to the first switch transistor through the scan line.
• the gate of T1 turns off the first switching transistor T1, and simultaneously inputs a low level through the control line to the gate of the second switching transistor 2 and the gate of the fifth switching transistor 5 to the second switching transistor 2 and the fifth switching transistor 5 Open.
• the opening of the first switch tube T1 may further open the first switch tube T1 and the fourth switch tube ⁇ 4;
• the first switch tube T1 and the fourth switch tube ⁇ 4 are simultaneously turned on, and the second switch tube ⁇ 2 and the fifth switch tube ⁇ 5 are simultaneously turned off, so that the data line, that is, the signal line where the data signal Vdata is located, passes through the first
• the switch tube T1 charges the first plate of the storage capacitor Cst, so that the power source VDD charges the second plate of the storage capacitor Cst through the fourth switch tube T4 and the compensation tube T3.
• step S12 the first switch tube T1 is turned off to close the first switch tube T1 and the fourth switch tube T4 at the same time.
• the first switch tube T1 and the fourth switch tube T4 are simultaneously turned off, and the second switch tube T2 and the fifth switch tube T5 are turned on at the same time, so that the light emitting device OLED is sequentially supplied by the power source VDD and flows through the light emitting device OLED.
• the gate of the fourth switching transistor T4 is connected to the scan line, the first pole is connected to the first pole of the second switching transistor T2, the second pole is connected to the first pole of the driving transistor DTFT, and the fourth switching transistor T4 and the first A switch tube T1 is of the same type.
• the fourth switch tube T4 and the first switch tube T1 are both controlled by the scan signal Vscan, the fourth switch tube T4 is turned on or off together with the first switch tube T1.
• the fourth switch tube T4 and the For the principle and detailed procedure of the opening or closing of a switch T1 refer to the description of the foregoing embodiment, and details are not described herein again.
• the fourth switching transistor T4 Since the fourth switching transistor T4 is turned on during the compensation phase, the light emitting device OLED can be short-circuited by the fourth switching transistor T4, that is, no current flows through the light emitting device OLED during the compensation phase, and the light emitting device OLED does not emit light, thereby avoiding the light emitting device OLED being The compensation phase flashes.
• the present invention also provides a display device, including any of the foregoing embodiments.
• the pixel circuit has the beneficial technical effects brought by the pixel circuit provided by the embodiment of the present invention. The foregoing has been described in detail, and details are not described herein again.

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• 2012
  • 2012-01-12 CN CN201210008738.3A patent/CN102654976B/zh active Active
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