Floating gate-based pixel compensation circuit, compensation method and display

Abstract

The invention discloses a floating gate-based pixel compensation circuit, which comprises an input circuit, a driving transistor and a threshold reading circuit which are connected in sequence, and is characterized in that the input circuit is used for outputting a Vin signal, the driving transistor is a floating gate transistor, the grid electrode of the driving transistor is connected to the input circuit through a Scan transistor, and the threshold reading circuit is used for reading the threshold value of the driving transistor. A substrate of the driving transistor is connected with VB voltage, and the threshold reading circuit is connected with a source drain electrode of the driving transistor through a Sense transistor and used for outputting Vout to measure threshold voltage. According to the scheme, the characteristics that the threshold value of the floating gate transistor is stable and can be adjusted are utilized, so that stable current and a better compensation effect can be obtained more easily when the floating gate transistor is used in a pixel external compensation circuit.

Description

Technical Field

[0001] The present application belongs to the field of display devices, and in particular relates to a floating gate-based pixel compensation circuit, a compensation method and a display. Background Art

[0002] The pixel internal compensation circuit is a key part in the AMOLED (active matrix organic light-emitting diode) display screen. It is mainly used to compensate for parameter fluctuations of the driving transistor and OLED devices caused by manufacturing process, aging or environmental changes, ensuring the uniformity and stability of display brightness.

[0003] The traditional pixel internal compensation circuit includes a driving transistor (T1) for controlling the pixel brightness; a switching transistor (T2) for selecting the pixel; a storage capacitor (Cst) for maintaining the gate voltage of the driving transistor; and a compensation circuit, which usually contains additional transistors and capacitors to compensate for changes in threshold voltage and mobility.

[0004] However, the traditional pixel internal compensation circuit needs to be reset, threshold acquired and data written for compensation every frame, and the threshold voltage of the traditional MOS transistor has been drifting with the increase of time stress, so that the compensation circuit has poor compensation effect or even fails after exceeding a certain threshold voltage range.

[0005] Therefore, a pixel compensation circuit is needed to solve the above problems. Summary of the invention

[0006] In order to address the deficiencies of the prior art, the present application provides a floating gate-based pixel compensation circuit, compensation method and display, which utilizes the threshold stability and adjustable threshold characteristics of the floating gate transistor to make it easier to obtain stable current and better compensation effect when used in a pixel external compensation circuit.

[0007] The technical effects to be achieved by this application are achieved through the following solutions: According to a first aspect of the present application, a floating gate-based pixel compensation circuit is provided, comprising an input circuit, a driving transistor, and a threshold reading circuit connected in sequence, wherein: The input circuit is used to output signal, the driving transistor is a floating gate transistor, the gate of the driving transistor is connected to the input circuit through a Scan transistor, and the substrate of the driving transistor is connected to The threshold reading circuit is connected to the source and drain of the driving transistor through the Sense transistor to output The threshold voltage is measured.

[0008] Preferably, both the Scan transistor and the Sense transistor are MOS transistors.

[0009] Preferably, the source and drain of the driving transistor are respectively connected to And the anode of OLED light-emitting diode.

[0010] Preferably, the input circuit is an integrated operational amplifier circuit, the input as well as After subtraction, the output is The signal acts as the gate voltage of the driving transistor.

[0011] Preferably, the input circuit The signal output terminal is connected with signal, 0V signal, Signal and Signal to adjust the driving timing of the pixel compensation circuit.

[0012] Preferably, the threshold reading circuit is an integrated operational amplifier circuit, and the Sense transistor is connected via a capacitor. Charges the threshold reading circuit to make the integral output Satisfies the following formula:

[0013] in, is the current on the Sense transistor, and t is the time.

[0014] Preferably, the threshold voltage is calculated according to the following formula: :

[0015] in, is the current on the Sense transistor;

[0016]

[0017] is the carrier mobility, is the gate oxide capacitance per unit area, and are the width and length of the channel, is the source-drain voltage of the Sense transistor, is the gate-source voltage of the Sense transistor.

[0018] Preferably, the capacitor An erase switch is connected in parallel, and the erase switch is used to reset the capacitor .

[0019] According to a second aspect of the present application, a pixel compensation method using the above floating gate based pixel compensation circuit is provided, comprising the following steps: Step 1: Scan transistor is turned on, write arrive ,Write arrive , the floating gate substrate potential is Floating, the Sense transistor is turned on, and the current from the drive transistor is obtained The threshold reading circuit starts to work, resetting the capacitor After charging is completed, the threshold information is obtained. ;

[0020] Step 2: Scan transistor is turned on, Sense transistor is turned off, Write 0V voltage to drive the substrate potential of the transistor Set to 20V, Set to floating to complete the threshold erase of the floating gate transistor; Step 3: and Write a 0V signal to program the floating gate transistor and adjust the threshold voltage by controlling the charge on the floating gate. Step 4: As Input, write arrive , the substrate potential of the driving transistor Set to Floating to write data information; Step 5: When the potential at the Vanode point is greater than the turn-on voltage of the OLED, the OLED starts to emit light, and the floating gate transistor provides a driving current to the OLED.

[0021] According to a third aspect of the present application, a display is provided, which adopts the above-mentioned floating gate-based pixel compensation circuit.

[0022] According to an embodiment of the present application, the beneficial effect of using the floating gate-based pixel compensation circuit is that the performance of the floating gate transistor is stable and the threshold voltage can be maintained for a relatively long time; at the same time, by changing the voltage of the floating gate transistor control terminal, the amount of charge written into the floating gate can be changed, thereby changing the threshold voltage of the floating gate transistor, so that it can be applied to the external compensation circuit of the OLED pixel; Use floating gate transistor as driver, with its specific reset and read ,Write , write data to emit light, realize the function of threshold adjustment and high stable threshold maintenance, make the driving current more stable and the display effect better BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present application or the existing technical solutions, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0024] Figure 1 This is a circuit structure block diagram of a floating gate-based pixel compensation circuit in one embodiment of the present application; Figure 2 for Figure 1 Schematic diagram of the input circuit; Figure 3 for Figure 1 Circuit schematic diagram of the mid-threshold reading circuit; Figure 4 FIG. 4 is a driving timing diagram of a floating gate-based pixel compensation method in an embodiment of the present application. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the present application clearer, the technical solution of the present application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0026] like Figure 1 As shown, a floating gate-based pixel compensation circuit in an embodiment of the present application includes an input circuit, a driving transistor, and a threshold reading circuit connected in sequence, wherein: Input circuit for output signal, the driving transistor is a floating gate transistor, the gate of the driving transistor is connected to the input circuit through the source and drain of the Scan transistor, and the substrate of the driving transistor is connected voltage, the source and drain of the driving transistor are connected and an anode of an OLED light emitting diode; The threshold reading circuit connects the source and drain of the driving transistor and the anode of the OLED light-emitting diode through the source and drain of the Sense transistor to output , thereby measuring the threshold voltage; the anode of the light-emitting diode is simultaneously connected to the gate of the driving transistor through a capacitor, which is 0.5~2pF.

[0027] Among them, the Scan transistor and the Sense transistor are both MOS tubes.

[0028] In this embodiment, a floating gate transistor is used as a driving transistor. The floating gate transistor can store charge for a long time and the threshold voltage is relatively stable. There is no need to perform erase, write, and read operations in each frame. It is only necessary to adjust the threshold voltage within a certain period of time. Therefore, the operation steps are simplified and the operation time is saved.

[0029] like Figure 2 As shown, the input circuit in one embodiment of the present application is an integrated operational amplifier circuit, and the input as well as After subtraction, the output is The signal acts as the gate voltage of the driving transistor.

[0030] Input circuit The signal output terminal is connected with signal, 0V signal, Signal and Signal to adjust the driving timing of the pixel compensation circuit.

[0031] This input circuit is located outside the pixel area, and its output is used as the input of the pixel compensation circuit . Enter different values ​​at different stages to During the programming phase, the threshold read circuit obtains and Doing subtraction, as the gate voltage of the floating gate transistor, can control the charge written into the floating gate; the specification of the resistor R2 in the figure is 10kΩ~100kΩ.

[0032] When the threshold When smaller, Smaller, larger gate voltage, allowing more charges to pass through the dielectric layer into the floating gate, thereby increasing the threshold voltage , when the threshold When larger, Larger, smaller gate voltage, which allows less charge to pass through the dielectric layer into the floating gate, thereby reducing the threshold voltage In this way, the threshold voltage of the floating gate transistor can be stabilized within a certain range to meet the requirements of driving the OLED to emit light.

[0033] like Figure 3 As shown, the threshold reading circuit in one embodiment of the present application is an integrated operational amplifier circuit, and the Sense transistor is connected through a capacitor Charges the threshold reading circuit to make the integral output Satisfies the following formula:

[0034] in, is the current on the Sense transistor, and t is the time. There is an erase switch in parallel, which is used to reset the capacitor .

[0035] When the floating gate transistor operates in the linear region, the source-drain voltage When unchanged, and threshold voltage There is a linear relationship, so the threshold voltage is calculated according to the following formula :

[0036] in, is the current on the Sense transistor;

[0037]

[0038] is the carrier mobility, is the gate oxide capacitance per unit area, and are the width and length of the channel, is the source-drain voltage of the Sense transistor, is the gate-source voltage of the Sense transistor.

[0039] and With threshold voltage There is a linear relationship, so by measuring To measure the threshold voltage .

[0040] The threshold reading circuit is located outside the pixel area. The size of R1 can be used to adjust the charging time. The specification of R1 is 10kΩ~100kΩ.

[0041] In one embodiment of the present application, a pixel compensation method using the above floating gate based pixel compensation circuit is disclosed, such as Figure 4 The driving timing of the pixel compensation shown includes the following steps: Step 1: Scan transistor is turned on, write arrive ,Write arrive , the floating gate substrate potential is Floating, the Sense transistor is turned on, and the current from the drive transistor is obtained , the threshold reading circuit starts working; close the erase switch between the input and output of the integrated operational amplifier to reset the capacitor , open the erase switch and hold it, reset the capacitor After charging, the threshold information is obtained. ; Step 2: In order to write a new threshold voltage to the floating gate transistor, an erase operation is required first. Specifically: The Scan transistor is turned on and the Sense transistor is turned off. Write 0V voltage to drive the substrate potential of the transistor Set to 20V, Set to floating, the charge escapes from the floating gate, passes through the dielectric layer and enters the substrate, completing the threshold erasure of the floating gate transistor; Step 3: Then program the new threshold voltage to the floating gate transistor, specifically: The threshold information obtained in step 1 and Make the difference, as The input of the floating-gate transistor, i.e., the gate input, will and Write a 0V signal to program the floating gate transistor and adjust the threshold voltage by controlling the charge on the floating gate. Step 4: As Input, write arrive , the substrate potential of the driving transistor Set to Floating to write data information; Step 5: When the potential at the Vanode point is greater than the turn-on voltage of the OLED, the OLED starts to emit light, and the floating gate transistor provides a driving current to the OLED.

[0042] When pixel compensation is not performed in the current frame, only two stages, writing data and emitting light, are required. Only give That's it.

[0043] This method uses a floating gate transistor as a driver tube, and cooperates with its specific reset and read ,Write , write data to emit light, realize the function of threshold adjustment and high stable threshold maintenance, make the driving current more stable and the display effect better In one embodiment of the present application, a display is also provided, which adopts the above-mentioned floating gate-based pixel compensation circuit.

[0044] According to an embodiment of the present application, the beneficial effect of using the floating gate-based pixel compensation circuit is that the performance of the floating gate transistor is stable and the threshold voltage can be maintained for a relatively long time; at the same time, by changing the voltage of the floating gate transistor control terminal, the amount of charge written into the floating gate can be changed, thereby changing the threshold voltage of the floating gate transistor, so that it can be applied to the external compensation circuit of the OLED pixel; Through operations such as erasing, writing, and reading, the floating gate transistor is reset (charge flows out of the floating gate), the threshold voltage is adjusted, data is written, etc., and the entire pixel external compensation process is completed; at the same time, because the floating gate storage charge can be maintained for a long time and the threshold voltage is relatively stable, there is no need to perform erase, write, and read operations in every frame, and it is only necessary to adjust the threshold voltage within a certain period of time.

[0045] It should be noted that the above detailed descriptions are exemplary and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present application belongs.

[0046] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should also be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0047] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein.

[0048] In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed or inherent to these processes, methods, products, or apparatuses.

[0049] For ease of description, spatially relative terms, such as "above", "above", "on the upper surface of", "above", etc., may be used herein to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" may include both "above" and "below". The device may also be positioned in other different ways, such as rotated 90 degrees or in other orientations, and the spatially relative descriptions used herein are interpreted accordingly.

[0050] In the above detailed description, reference is made to the accompanying drawings, which form a part of this document. In the accompanying drawings, similar symbols typically identify similar components unless the context indicates otherwise. The illustrated embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be used, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein.

[0051] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A floating gate based pixel compensation circuit, characterized in that: The invention comprises an input circuit, a driving transistor and a threshold reading circuit connected in sequence, wherein: The input circuit is used to output signal, the driving transistor is a floating gate transistor, the gate of the driving transistor is connected to the input circuit through a Scan transistor, and the substrate of the driving transistor is connected to The threshold reading circuit is connected to the source and drain of the driving transistor through the Sense transistor to output The threshold voltage is measured.

2. The floating gate based pixel compensation circuit according to claim 1, characterized in that: The Scan transistor and the Sense transistor are both MOS transistors.

3. The floating gate based pixel compensation circuit according to claim 1, characterized in that: The source and drain of the driving transistor are respectively connected And the anode of OLED light-emitting diode.

4. The floating gate based pixel compensation circuit according to claim 3, characterized in that: The input circuit is an integrated operational amplifier circuit. as well as After subtraction, the output is The signal acts as the gate voltage of the driving transistor.

5. The floating gate based pixel compensation circuit according to claim 4, characterized in that: The input circuit The signal output terminal is connected with signal, 0V signal, Signal and Signal to adjust the driving timing of the pixel compensation circuit.

6. The floating gate based pixel compensation circuit according to claim 1, characterized in that: The threshold reading circuit is an integrated operational amplifier circuit, and the Sense transistor is connected through a capacitor. Charges the threshold reading circuit to make the integral output Satisfies the following formula: ； in, is the current on the Sense transistor, For time.

7. The floating gate based pixel compensation circuit according to claim 6, characterized in that: The threshold voltage is calculated according to the following formula : ； in, is the current on the Sense transistor; ； ； is the carrier mobility, is the gate oxide capacitance per unit area, and are the width and length of the channel, is the source-drain voltage of the Sense transistor, is the gate-source voltage of the Sense transistor.

8. The floating gate based pixel compensation circuit according to claim 6, characterized in that: The capacitor An erase switch is connected in parallel, and the erase switch is used to reset the capacitor .

9. A pixel compensation method using the floating gate based pixel compensation circuit according to any one of claims 1 to 8, characterized in that: The steps include: Step 1: Scan transistor is turned on, write arrive ,Write arrive , the floating gate substrate potential is Floating, the Sense transistor is turned on, and the current from the drive transistor is obtained , the threshold reading circuit starts working, resetting the capacitor After charging is completed, the threshold information is obtained. ; Step 2: Scan transistor is turned on, Sense transistor is turned off, Write 0V voltage to drive the substrate potential of the transistor Set to 20V, Set to floating to complete the threshold erase of the floating gate transistor; Step 3: and Write a 0V signal to program the floating gate transistor and adjust the threshold voltage by controlling the charge on the floating gate. Step 4: As Input, write arrive , the substrate potential of the driving transistor Set to Floating to write data information; Step 5: When the potential at the Vanode point is greater than the turn-on voltage of the OLED, the OLED starts to emit light, and the floating gate transistor provides a driving current to the OLED.

10. A display, characterized in that: A floating gate based pixel compensation circuit as described in any one of claims 1 to 8 is adopted.

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