Floating gate based pixel compensation circuit, compensation method and display

Abstract

The application discloses a floating gate based pixel compensation circuit, comprising input circuit, driving transistor and threshold reading circuit connected in sequence, wherein: the input circuit is used for outputting V in 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, the substrate of the driving transistor is connected to a VB voltage, the threshold reading circuit is connected to the source-drain of the driving transistor through a Sense transistor, and is used for outputting V out measured threshold voltage. The scheme utilizes the threshold stability and threshold adjustment characteristics of the floating gate transistor, so that the floating gate transistor is used in the pixel external compensation circuit, and stable current and better compensation effect are easily obtained.

Description

Technical Field

[0001] This application belongs to the field of display devices, and specifically relates to a pixel compensation circuit, compensation method and display based on a floating gate. Background Technology

[0002] The pixel internal compensation circuit is a key part of AMOLED (Active Matrix Organic Light Emitting Diode) displays. It is mainly used to compensate for parameter fluctuations in driving transistors and OLED devices caused by manufacturing processes, aging, or environmental changes, ensuring the uniformity and stability of display brightness.

[0003] Traditional pixel internal compensation circuitry includes a driving transistor (T1) for controlling pixel brightness; a switching transistor (T2) for gating the pixel; a storage capacitor (Cst) for maintaining the gate voltage of the driving transistor; and a compensation circuit, which typically contains additional transistors and capacitors, for compensating for changes in threshold voltage and mobility.

[0004] However, traditional pixel-internal compensation circuits require resetting, threshold acquisition, and data writing compensation for each frame. Moreover, the threshold voltage of traditional MOS transistors keeps drifting with the increase of time stress, causing the compensation circuit to deteriorate or even fail 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] To address the shortcomings of the prior art, this application provides a pixel compensation circuit, compensation method, and display based on a floating gate transistor. By utilizing the threshold stability and adjustable threshold characteristics of the floating gate transistor, it is easier to obtain stable current and achieve better compensation effect when used in external pixel compensation circuits.

[0007] The technical effect to be achieved in this application is accomplished through the following solution:

[0008] According to a first aspect of this application, a pixel compensation circuit based on a floating gate is provided, comprising an input circuit, a driving transistor, and a threshold readout circuit connected in sequence, wherein:

[0009] The input circuit is used for output. The signal, wherein 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 voltage, the threshold readout circuit is connected to the source and drain of the driving transistor via the Sense transistor, for output. Perform a threshold voltage measurement.

[0010] Preferably, both the Scan transistor and the Sense transistor are MOS transistors.

[0011] Preferably, the source and drain of the driving transistor are respectively connected to And the anode of the OLED light-emitting diode.

[0012] Preferably, the input circuit is an integrated operational amplifier circuit, and the input... as well as After subtraction, output The signal serves as the gate voltage of the driving transistor.

[0013] Preferably, the input circuit of The signal output terminal is connected to Signal, 0V signal Signals and Signals are used to adjust the driving timing of the pixel compensation circuit.

[0014] Preferably, the threshold reading circuit is an integrated operational amplifier circuit, and the Sense transistor is connected to a capacitor. Charge the threshold reading circuit to enable integral output. Satisfy the following formula:

[0015]

[0016] in, t represents the current across the Sense transistor and t represents time.

[0017] Preferably, the threshold voltage is calculated according to the following formula. :

[0018]

[0019] in, The current on the Sense transistor;

[0020]

[0021]

[0022] It is the carrier mobility. It is the gate oxide capacitance per unit area. and These are the width and length of the channel, respectively. It is the source-drain voltage of the Sense transistor. It is the gate-source voltage of the Sense transistor.

[0023] Preferably, the capacitor An erase switch is connected in parallel, which is used to reset the capacitor. .

[0024] According to a second aspect of this application, a pixel compensation method employing the above-described floating gate-based pixel compensation circuit is provided, comprising the following steps:

[0025] Step 1: Scan transistor is turned on, write arrive ,Write arrive When the floating gate substrate potential is Floating, the Sense transistor is turned on and draws current from the driving transistor. The threshold reading circuit starts working, and the reset capacitor... Then charging begins, and once charging is complete, information containing threshold data is obtained. ;

[0026] Step 2: The Scan transistor is turned on, and the Sense transistor is turned off. Write a 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;

[0027] Step 3: Put and Write a 0V signal to program the floating gate transistor, and adjust the threshold voltage by controlling the charge on the floating gate;

[0028] Step 4: As Input, write arrive The substrate potential of the driving transistor Set to Floating mode to write data.

[0029] Step 5: When the Vanode potential is greater than the OLED's turn-on voltage, the OLED starts to emit light, and the floating gate transistor provides driving current to the OLED.

[0030] According to a third aspect of this application, a display is provided that employs the aforementioned floating gate-based pixel compensation circuit.

[0031] According to one embodiment of this application, the beneficial effect of using this floating gate-based pixel compensation circuit is that the floating gate transistor has stable performance and the threshold voltage can be maintained for a relatively long time; at the same time, by changing the voltage of the control terminal of the floating gate transistor, the amount of charge written to the floating gate can be changed, thereby changing the threshold voltage of the floating gate transistor, so that it can be applied in the external compensation circuit of OLED pixels.

[0032] Using a floating-gate transistor as the driving transistor, along with its specific reset and readout... ,Write The timing of writing data to emit light enables threshold adjustment and high-stability threshold maintenance, resulting in a more stable driving current and better display effect. Attached Figure Description

[0033] To more clearly illustrate the embodiments of this application or the existing technical solutions, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a circuit structure block diagram of a pixel compensation circuit based on a floating gate according to an embodiment of this application;

[0035] Figure 2 for Figure 1 Circuit schematic of the input circuit;

[0036] Figure 3 for Figure 1 Circuit diagram of the middle threshold reading circuit;

[0037] Figure 4 This is a driving timing diagram of a pixel compensation method based on a floating gate in one embodiment of this application. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0039] like Figure 1 As shown, a pixel compensation circuit based on a floating gate in one embodiment of this application includes an input circuit, a driving transistor, and a threshold readout circuit connected in sequence, wherein:

[0040] Input circuit is used for output The signal is driven by 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. The substrate of the driving transistor is connected to... Voltage, driving the source and drain of the transistor are connected respectively And the anode of the OLED light-emitting diode;

[0041] The threshold readout circuit connects the source and drain of the driving transistor and the anode of the OLED light-emitting diode via the source and drain of the Sense transistor, for output. The threshold voltage is thus measured; the anode of the light-emitting diode is simultaneously connected to the gate of the driving transistor via a capacitor of 0.5~2pF.

[0042] Both the Scan transistor and the Sense transistor are MOS transistors.

[0043] In this embodiment, a floating gate transistor is used as the driving transistor. Taking advantage of the fact that the floating gate transistor can store charge for a long time and has a relatively stable threshold voltage, there is no need to perform erase, write, and read operations in every frame. The threshold voltage only needs to be adjusted within a certain period of time, which simplifies the operation steps and saves operation time.

[0044] like Figure 2 As shown, in one embodiment of this application, the input circuit is an integrated operational amplifier circuit. as well as After subtraction, output The signal serves as the gate voltage of the driving transistor.

[0045] Input circuit The signal output terminal is connected to Signal, 0V signal Signals and Signals are used to adjust the driving timing of the pixel compensation circuit.

[0046] This input circuit is located outside the pixel area, and its output serves as the input to the pixel compensation circuit. Input different values ​​at different stages. During the programming phase, the threshold reading circuit obtains... and Subtraction, used as the gate voltage of the floating gate transistor, can control the charge written to the floating gate; the resistor R2 in the figure has a specification of 10kΩ~100kΩ.

[0047] When the threshold When smaller, A smaller threshold voltage and a larger gate voltage allow more charge to pass through the dielectric layer into the floating gate, thereby increasing the threshold voltage. When the threshold When it is large, A larger threshold voltage and a smaller gate voltage allow less charge to pass through the dielectric layer into the floating gate, thus reducing the threshold voltage. In this way, the threshold voltage of the floating gate transistor can be stabilized within a certain range, meeting the requirements for driving OLED light emission.

[0048] like Figure 3 As shown, in one embodiment of this application, the threshold reading circuit is an integrated operational amplifier circuit, and the Sense transistor is connected to a capacitor. Charge the threshold reading circuit to enable integral output. Satisfy the following formula:

[0049]

[0050] in, Let t be the current across the Sense transistor, and t be time. In the capacitor... An erase switch is connected in parallel; the erase switch is used to reset the capacitor. .

[0051] Because when the floating-gate transistor operates in the linear region, the source-drain voltage... When unchanged, and threshold voltage There is a linear relationship, therefore the threshold voltage can be calculated using the following formula. :

[0052]

[0053] in, The current on the Sense transistor;

[0054]

[0055]

[0056] It is the carrier mobility. It is the gate oxide capacitance per unit area. and These are the width and length of the channel, respectively. It is the source-drain voltage of the Sense transistor. It is the gate-source voltage of the Sense transistor.

[0057] and With threshold voltage There is a linear relationship, therefore, by measuring... To measure threshold voltage .

[0058] This threshold reading circuit is located outside the pixel area, and can be adjusted... The size of the resistor is used to adjust the charging time; R1 has a specification of 10kΩ~100kΩ.

[0059] One embodiment of this application discloses a pixel compensation method employing the aforementioned floating-gate-based pixel compensation circuit, such as... Figure 4 The pixel compensation driving timing shown includes the following steps:

[0060] Step 1: Scan transistor is turned on, write arrive ,Write arrive When the floating gate substrate potential is Floating, the Sense transistor is turned on and draws current from the driving transistor. The threshold readout circuit starts working; the erase switch between the input and output of the integrated operational amplifier is turned off to reset the capacitor. Turn on the erase switch and hold it, then turn on the reset capacitor. Charge the device, and once charging is complete, obtain the information containing the threshold. ;

[0061] Step 2: In order to write a new threshold voltage to the floating gate transistor, an erase operation is first required. Specifically:

[0062] Scan transistor on, Sense transistor off. Write a 0V voltage to drive the substrate potential of the transistor. Set to 20V. When set to floating, the charge escapes from the floating gate, passes through the dielectric layer, and enters the substrate, completing the threshold erase of the floating gate transistor;

[0063] Step 3: Next, program a new threshold voltage for the floating gate transistor, specifically:

[0064] The threshold information obtained in step 1 and Take the difference as The input, i.e., the gate input of the floating-gate transistor, 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;

[0065] Step 4: As Input, write arrive The substrate potential of the driving transistor Set to Floating mode to write data.

[0066] Step 5: When the Vanode potential is greater than the OLED's turn-on voltage, the OLED starts to emit light, and the floating gate transistor provides driving current to the OLED.

[0067] When pixel compensation is not performed in the current frame, only two stages are required: writing data and emitting light. Only give That's all.

[0068] This method utilizes a floating-gate transistor as the driving transistor, along with its specific reset and readout functions. ,Write The timing of writing data to emit light enables threshold adjustment and high-stability threshold maintenance, resulting in a more stable driving current and better display effect.

[0069] In one embodiment of this application, a display is also provided that employs the above-described floating gate-based pixel compensation circuit.

[0070] According to one embodiment of this application, the beneficial effect of using this floating gate-based pixel compensation circuit is that the floating gate transistor has stable performance and the threshold voltage can be maintained for a relatively long time; at the same time, by changing the voltage of the control terminal of the floating gate transistor, the amount of charge written to the floating gate can be changed, thereby changing the threshold voltage of the floating gate transistor, so that it can be applied in the external compensation circuit of OLED pixels.

[0071] By performing 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, and data is written, thus completing the entire external compensation process for the pixel. At the same time, since the charge stored in the floating gate can be maintained for a relatively long time, the threshold voltage is relatively stable. Therefore, it is not necessary to perform erasing, writing, and reading operations for every frame. The threshold voltage can be adjusted only within a certain period of time.

[0072] It should be noted that the above detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0073] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0074] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented in sequences other than those illustrated or described herein.

[0075] Furthermore, the terms “comprising” and “having”, and any variations thereof, are intended to cover non-exclusive inclusion. 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 that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or apparatus.

[0076] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can 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 spatial relative descriptions used herein will be interpreted accordingly.

[0077] In the detailed description above, reference has been made to the accompanying drawings, which form part of this document. In the drawings, similar symbols typically identify similar parts unless the context otherwise indicates otherwise. The illustrated embodiments described in the detailed specification, drawings, and claims are not intended 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.

[0078] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A pixel compensation circuit based on a floating gate, characterized in that, It includes an input circuit, a driving transistor, and a threshold readout circuit connected in sequence, wherein: The input circuit is used for output. The signal, wherein 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 voltage, the threshold readout circuit is connected to the source and drain of the driving transistor via the Sense transistor, for output. The threshold voltage is measured; both the Scan transistor and the Sense transistor are MOS transistors; the source and drain of the driving transistor are respectively connected to... And the anode of the OLED light-emitting diode; The input circuit is an integrated operational amplifier circuit. as well as After subtraction, the result is generated Signal, the input circuit The signal output terminal is connected to Signal, 0V signal Signals and Signals are used to adjust the driving timing of the pixel compensation circuit and output. The signal serves as the gate voltage of the driving transistor; The threshold reading circuit is an integrated operational amplifier circuit, and the Sense transistor is connected to a capacitor. Charge the threshold reading circuit to enable integral output. Satisfy the following formula: in, To drive the current on the transistor, For time; Calculate the threshold voltage using the following formula. : in, To drive the current on the transistor; It is the carrier mobility. It is the gate oxide capacitance per unit area. and These are the width and length of the channel, respectively. It is the source-drain voltage driving the transistor. It is the gate-source voltage driving the transistor; by measuring... To measure threshold voltage ; The specific working method of the above pixel compensation circuit is as follows: Step 1: Turn on the Scan transistor and write V. ref To V in Write VDD to VD, the floating gate substrate potential is floating, the Sense transistor turns on, and the current I from the driving transistor is obtained. ds The threshold reading circuit starts working, and the reset capacitor C... int Then charging begins, and once charging is complete, V containing threshold information is obtained. out ; Step 2: Scan transistor turns on, Sense transistor turns off, V in Write a 0V voltage to set the substrate potential VB of the driving transistor to 20V and set VD to floating, thus completing the threshold erase of the floating gate transistor. Step 3: Write 0V signals to VD and VB to program the drive transistor, setting V... in Write V prgm The voltage is applied to the gate of the driving transistor, and the threshold voltage is adjusted by controlling the charge on the floating gate. Step 4: Put V data As V in The input is written from VDD to VD, and the substrate potential VB of the driving transistor is set to floating to write data information. Step 5: When the Vanode potential is greater than the OLED's turn-on voltage, the OLED starts to emit light, and the floating gate transistor provides driving current to the OLED.

2. The pixel compensation circuit based on a floating gate according to claim 1, characterized in that, The capacitor An erase switch is connected in parallel, which is used to reset the capacitor. .

3. A display, characterized in that, The pixel compensation circuit based on the floating gate as described in claim 1 or 2 is adopted.

Images