This application claims priority to Chinese Patent Application No. 202011608249.2, filed on Dec. 30, 2020, the entire contents of which are incorporated herein by reference.
The present disclosure relates to display technology, and more particularly to a display panel, a driving method and a display device.
OLED (Organic Light Emitting Diode) display devices have the advantages of being self-luminous, having a low driving voltage and a short response time, and being flexible etc. The OLED display devices have a great potential of development.
OLED display devices normally have corresponding pixel circuits to drive the OLED elements to emit light. However, the pixel circuits in the prior art do not have threshold compensation function. Therefore, the uniformity in display of such display devices is not desirable.
In a first aspect of the present disclosure, a display panel is provided. The display panel comprises a substrate; a plurality of sub-pixels located on one side of the substrate; and at least one first signal module. Each sub-pixel includes a pixel circuit and a light-emitting element, and the pixel circuit includes a reset module, a data-writing module, a driving transistor, a light-emitting control module and a first memory module. The data-writing module, a first end of the first memory module and a gate electrode of the driving transistor are electrically connected to a first node; the reset module, a first electrode of the driving transistor, the light-emitting control module and a second end of the first memory module are electrically connected to a second node; and the light-emitting element is electrically connected to the light-emitting control module. A first output end of the first signal module is electrically connected to the data-writing module, and a second output end of the first signal module is electrically connected to the reset module The reset module is configured to provide a reset signal to an anode of the light-emitting element through the light-emitting control module in a reset stage The first signal module is configured to provide a data voltage signal to the data-writing module in a data-writing stage to write the data voltage signal to the gate electrode of the driving transistor and the first end of the first memory module through the data-writing module; and is further configured to provide a data current signal to the driving transistor in the data-writing stage to compensate the threshold voltage of the driving transistor to the second node; the light-emitting control module is configured to control a driving current generated by the driving transistor to flow into the light-emitting element to drive the light-emitting element to emit light.
In a second aspect of the present disclosure, a control method of a display panel is provided, the method comprises:
in a reset stage, providing a reset signal, by the reset module, to the anode of the light-emitting element through the light-emitting control module;
in a data-writing stage, providing, by the first signal module, a data voltage signal to the data-writing module to write the data voltage signal to the gate electrode of the driving transistor and the first end of the first memory module through the data-writing module, and providing, by the first signal module, a data current signal to the driving transistor to compensate the threshold voltage of the driving transistor to the second node; and
in a light-emitting stage, controlling, by the light-emitting control module, the driving current generated by the driving transistor to flow into the light-emitting element to drive the light-emitting element to emit light.
In a third aspect of the present disclosure, a display device is provided. The display device comprises a display panel according to the above first aspect of the present disclosure.
It should be readily understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not intended as a limitation to the scope of the present disclosure.
The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
In the following, embodiments of the present disclosure will be described in detail with reference to the figures. It should be understood that, the embodiments described hereinafter are only used for explaining the present disclosure, and should not be understood to limit the present disclosure. To describe the embodiments more clearly, the figures only show some aspects, instead of every aspect, of the present disclosure.
To solve the above issues, the present disclosure provides a display panel. As illustrated in an exemplary embodiment in
In the embodiment of the present disclosure, the first signal module is capable of providing a data voltage signal to the data-writing module in a data-writing stage to write the data voltage signal to the gate electrode of the driving transistor and the first end of the first memory module through the data-writing module. The first signal module is further capable of providing a data current signal to the driving transistor in the data-writing stage to compensate the threshold voltage of the driving transistor to the second node to realize the threshold compensation function. Furthermore, when the first memory module is a capacitor, even if the light emitted by the light-emitting element attenuates and the voltage of the second node floats, the voltage of the first node will change correspondingly due to the coupling effect of the capacitor to inhibit the attenuation impact of the light-emitting element. Therefore, the uniformity of the display panel will be improved. In addition, the pixel circuit according to the embodiment of the present disclosure has a simple structure and a small size, which increases the resolution of the display panel.
The above describes the core concept of the present disclosure, and those skilled in the art can get other embodiments, based on the embodiments of the present disclosure, without making any creative work, which are all within the protection scope of the present disclosure. In the following, the embodiments of the present disclosure will be further described clearly and fully combining with the figures according to the embodiments of the present disclosure.
Specifically, in the reset stage, the reset voltage is written to the anode of the light-emitting element 22 to initialize the electric potential of the anode of the light-emitting element 22, and decrease the effect from the voltage on the anode of the light-emitting element 22 in the last frame to the voltage on the anode of the light-emitting element 22 in the current frame, such that the uniformity in display is improved. Optionally, the first signal module 30 is capable of outputting a reset voltage and writing the reset voltage to the anode of the light-emitting element 22 through the reset module 211 and the light-emitting control module 213. The reset voltage can be output by the first signal module 30, thus there is no need to provide a separate module to provide the reset voltage and the structure of the pixel circuit is simplified
In the data-writing stage, the first signal module 30 outputs the data voltage signal Vdata, which is required for display, then the data voltage signal Vdata is written to the gate electrode of the driving transistor MD and the first end of the first memory module 214, that is, the first node N1. At this time, the data-writing module 212, the driving transistor MD, the reset module 211 and the first signal module 30 together form a loop. The first signal module 30 not only provides the data voltage signal Vdata required for display, but also provide a data current signal ID required for display after compensation. At this time, the current in the loop is the data current signal ID, that is, the current IMD of the driving transistor MD is equal to the data current signal ID. When the current IMD of the driving transistor MD is a stable value, the source electrode of the driving transistor MD will be self-adapted to a certain voltage, that is, the second node N2 is self-adapted to a certain voltage, so that ID=IMD=k*(Vgs−Vth)=k*(Vdata−VN2−Vth)2,
wherein, μ is the carrier mobility, Cox is the channel capacitance in a unit area of the driving transistor MD,
is a ratio of width to length of the driving transistor MD. Therefore, the voltage of the second node N2 includes the information of the threshold voltage Vth of the driving transistor MD. The voltage of the first node N1 and the voltage of the second node N2 are both stored in the first memory module 214, that is, the voltage range of the first memory module 214 is Vdata−VN2.
In the light-emitting stage, the light-emitting control module 213 is turned on, the light-emitting current IMD at this time is: IMD=k*(Vdata−VN2−Vth)2. As the voltage of the second node N2 includes the information of the threshold voltage Vth of the driving transistor MD, the threshold voltage compensation of the driving transistor MD is realized, the light-emitting element 22 is no longer impacted by the threshold voltage Vth, the unity in display is improved. Furthermore, if the first memory module 214 is a capacitor, even if the light emitted by the light-emitting element 22 attenuates and the voltage of the second node N2 varies, the voltage of the first node N1 will also vary under the coupling effect of the capacitor, to inhibit the attenuation influence of the light emitted by the light-emitting element 22, therefore, the uniformity of the display panel will be improved.
Furthermore, the display panel of the present embodiment can realize the compensation to the threshold voltage of the driving transistor MD through the first signal module 30 instead of a complex compensation circuit. Compared to the pixel circuit having the threshold compensation function in the prior art, the pixel circuit of the embodiment has a simple structure and a small size, and increases the resolution of the display panel.
It should be understood that, the structures of the reset module 211, the data-writing module 212, the light-emitting control module 213, the first memory module 214 and the first signal module 30 are not specifically limited to exemplary structures. Based on that the compensation function to the threshold voltage of the driving transistor MD can be realized, each module can be designed according to actual requirements.
In some embodiments, the substrate of the display panel includes a silicon substrate. Therefore, the pixel circuit is produced on single-crystal silicon, using SMIC 110 nm CMOS (Complementary Metal Oxide Semiconductor) technology.
Specifically, in the reset stage, the third gating unit 33 writes the received reset signal Vini to the anode of the light-emitting element 22 through the reset module 211 and the light-emitting control module 213 to reset the electrical potential of the anode of the light-emitting element 22.
In the data-writing stage, the fourth gating circuit 34 is turned on, the constant current source 31 outputs a data current signal ID corresponding to the gray scale of the sub-pixel to the inverse-phase input end of the operational amplifier 32, so the output end of the operational amplifier 32 outputs a data voltage signal Vdata required for display. The constant current source 31, the reset module 211, the driving transistor MD, the data-writing module 212 and the operational amplifier 32 together form a loop, and the current in the loop is the data current signal ID output from the constant current source 31. Therefore, the current IMD of the driving transistor MD is exactly equal to the data current signal ID. As the voltage on the gate electrode of the driving transistor MD is Vdata, the source electrode of the driving transistor MD will be self-adapted to a certain voltage, that is, the second node N2 is self-adapted to a certain voltage, so that ID=IMD=k*(Vdata−VN2−Vth)2. Therefore, the voltage of the second node N2 includes the information of the threshold voltage Vth of the driving transistor MD. The voltage of the first node N1 and the voltage of the second node N2 are both stored in the first memory module 214, that is, the voltage range of the first memory module 214 is Vdata-VN2.
In the light-emitting stage, the light-emitting control module 213 is turned on, the light-emitting current IMD at this time is: IMD=k*(Vdata−VN2−Vth)2. As the voltage of the second node N2 includes the information of the threshold voltage Vth of the driving transistor MD, the threshold voltage compensation of the driving transistor MD is realized, the light-emitting element 22 is no longer impacted by the threshold voltage Vth, and thus the unity in display is improved.
Based on the above technical solution, optionally, as shown in
The third control signal XSW3 is configured to control the turning on or turning off the third transistor M3, and thus to control whether the reset signal Vini is transmitted to the reset module 211. The fourth control signal SW3 is configured to control the turning on or turning off the fourth transistor M4, and thus to control whether the data current signal ID output from the constant current source 31 is transmitted to the loop. The third control signal XSW3 is a signal opposite to the fourth control signal SW3, that is, when the third transistor M3 is turned on, the fourth transistor M4 is turned off, or when the third transistor M3 is turned off, the fourth transistor M4 is turned on.
In the illustrated embodiment, with the arrangement of the second phase inverter 35, the display panel can control the third transistor M3 and the fourth transistor M4 by only providing the control signal XSW3, instead of providing control signal lines separately for the third transistor M3 and the fourth transistor M4. Therefore, the layout of the display panel is simplified, the structure is simplified, and the producing efficiency of the display panel is increased. In addition, the number of the control ends on the chip for driving the pixel circuit can be decreased, and the cost of the chip can be saved.
It should be understood that, as the data current signal ID provided by the first signal module 30 is not a fixed value and has different values according to different gray scales. As illustrated in
In one example embodiment wherein the driving transistor MD is a NMOS transistor, each of the first memory module 214 and the second memory module 215 is a capacitor, the operation principle is described below.
In a reset stage, the reset module 211 and the light-emitting control module 213 are turned on. The reset module 211 transmits a reset voltage to an anode of the light-emitting element 22 through the light-emitting control module 213 to reset the anode of the light-emitting element 22. The electrical potential of the first node N1 is equal to the electrical potential of the last frame (i.e., the last time of light-emitting). At the same time, the second signal module 40 provides a first fixed electrical potential V1 to the first end of the second memory module 215.
In the first stage, the data-writing module 212 and the reset module 211 are turned on. The first signal module 30 outputs the data voltage signal Vdata to the gate electrode of the driving transistor MD and the first end of the first memory module 214 through the data-writing module 212, that is, output to the first node N1. At this time, the data-writing module 212, the driving transistor MD, the reset module 211 and the first signal module 30 together form a loop. The first signal module 30 not only provides the data voltage signal Vdata required for display, but also provides a data current signal ID required for display after compensation. At this time, the current in the loop is the data current signal ID, that is, the current IMD of the driving transistor MD is equal to the data current signal ID. When the current IMD of the driving transistor MD is a fixed value, the source electrode of the driving transistor MD will be self-adapted to a certain voltage, that is, the second node N2 is self-adapted to a certain voltage, so that ID=IMD=k*(Vdata−VN2−Vth)2, wherein the voltage of the second node N2 includes the information of the threshold voltage Vth of the driving transistor MD.
In the second stage, the data-writing module 212 is turned on. The electrical potential of the first node N1 is still equal to the data voltage signal Vdata. The second signal module 40 provides a second fixed electrical potential V2 to the first end of the second memory module 215 to control the electrical potential of the first end of the second memory module 215 to jump from the first fixed electrical voltage V1 to the second fixed electrical potential V2, that is, a voltage jump of ΔV is generated, wherein, ΔV=V2−V1.
As the capacitor has a characteristic of charge conservation, if an electrical potential of one electrode of the capacitor varies, the electrical potential of another electrode of the capacitor will also varies under the coupling effect. Further, as the first memory module 214 is electrically connected to the second memory module 215 in series, when the electrical potential of a first end of the second memory module 215 varies for ΔV, the second node N2 varies for C1*ΔV/(C1+C2), wherein, C1 is the capacitance of the first memory module 214, C2 is the capacitance of the second memory module 215. The voltage range between the two ends of the first memory module 214 is Vdata−VN2−C1*ΔV/(C1+C2). When the data-writing module 212 is turned off, the voltage of the first node N1 and the voltage of the second node N2 are stored in the first memory module 214 and the second memory module 215.
In the light-emitting stage, the light-emitting control module 213 is turned on, the first node N1 is floating, and the light-emitting current at this time is: IMD=k*(Vdata−VN2−C1*ΔV/(C1+C2)−Vth)2.
In the illustrated embodiment, as the voltage of the second node N2 includes the information of the threshold voltage Vth of the driving transistor MD, the threshold voltage compensation of the driving transistor MD is realized. In addition, the second signal module 40 raises the electrical potential of the second node N2 by ΔV/(C1+C2), therefore, the gate-source voltage Vgs is decreased by ΔV/(C1+C2) from the original voltage, therefore, the data range of the pixel circuit is increased, the gamma of 0-255 gray scale can be easily adjusted.
As shown in
The first control signal SW1 controls turning on or turning off the first transistor M1 to control whether the first voltage signal V1 is transmitted to the first end of the second memory module 215. The second control signal SW2 controls turning on or turning off the second transistor M2 to control whether the second voltage signal V2 is transmitted to the first end of the second memory module 215. The first control signal SW1 is a signal opposite to the second control signal SW2, that is, when the first transistor M1 is turned on, the second transistor M2 is turned off; or when the first transistor M1 is turned off, the second transistor M2 is turned on.
In the illustrated embodiment, with the arrangement of the first phase inverter 43, the display panel can control the first transistor M1 and the second transistor M2 by only providing the control signal SW1 instead of providing control signal lines separately for the first transistor M1 and the second transistor M2. Therefore, the layout of the display panel is simplified, the structure is simplified, and the producing efficiency of the display is improved. In addition, the number of the control ends on the chip for driving the pixel circuit can be decreased, and the cost of the chip can be saved.
In the illustrated embodiment, as the first ends of the second memory modules 215 of the sub-pixels on a same line are all electrically connected to a same second signal module 40, the second signal module 40 is capable of providing the first voltage signal V1 to the first ends of the second memory modules 215 of the sub-pixels on a same line in the reset stage and the first stage, and providing the second voltage signal V2 to the first ends of the second memory modules 215 of the sub-pixels on a same line. Therefore, the number of the second signal modules in the display panel can be decreased, the producing steps of the display panel are simplified, and the producing efficiency of the display panel is improved. In addition, the synchronicity of the first ends of the second memory modules 215 of the sub-pixels on a same line receiving the first voltage signal V1 and the second voltage signal V2 is ensured.
It should be understood that
In the illustrated embodiment, each transistor may be a PMOS transistor, or a NMOS transistor, the embodiment of the present disclosure has no limit to this. Taking the pixel circuit 21 being a 4T2C circuit as an example, the transistors, the third gating unit 33 and the fourth gating unit 34 in the pixel circuit 21 are all NMOS transistors and the first gating unit 41 and the second gating unit 42 are both PMOS transistors. The working principle of the first signal module 30, the second signal module 40 and the pixel circuit 21 are described in detail.
In the time period from T2 to T3 (i.e., in the first stage), the first control signal SW1 received by the gate electrode of the first transistor M1, the third control signal XSW3 received by the gate electrode of the third transistor M3 and the light-emitting control signal Emit received by the gate electrode of the seventh transistor M7 are all low-level signals. The second control signal SW2 received by the gate electrode of the second transistor M2, the fourth control signal SW3 received by the gate electrode of the fourth transistor M4, the second scan signal SCAN2 received by the gate electrode of the fifth transistor M5 and the first scan signal SCAN1 received by the gate electrode of the sixth transistor M6 are all high-level signals. At this time, the first transistor M1, the fourth transistor M4, the sixth transistor M6 and the fifth transistor M5 are turned on. The constant current source 31 outputs a data current signal ID corresponding to the gray scale of the sub-pixel to the inverse-phase input end of the operational amplifier 32, so that the output end of the operational amplifier 32 outputs a data voltage signal Vdata required for display, the constant current source 31, the sixth transistor M6, the driving transistor MD, the fifth transistor M5 and the operational amplifier 32 together form a loop. The current in the loop is the data current signal ID output from the constant current source 31. Therefore, the current IMD of the driving transistor MD is exactly equal to the data current signal ID. As the voltage on the gate electrode of the driving transistor MD is Vdata, the source electrode of the driving transistor MD will be self-adapted to a certain voltage, that is, the second node N2 is self-adapted to a certain voltage, so that ID=IMD=k*(Vdata−VN2−Vth)2. The voltage of the second node N2 includes the information of the threshold voltage Vth of the driving transistor MD. The voltage of the first node N1 and the voltage of the second node N2 are both stored in the first memory module 214, that is, the voltage range of the first memory module 214 is Vdata−VN2.
In the time period from T3 to T4 (i.e., in the second stage), the second control signal SW2 received by the gate electrode of the second transistor M2, the third control signal XSW3 received by the gate electrode of the third transistor M3, the second scan signal SCAN2 received by the gate electrode of the fifth transistor M5 and the light-emitting control signal Emit received by the gate electrode of the seventh transistor M7 are all low-level signals. The first control signal SW1 received by the gate electrode of the first transistor M1, the fourth control signal SW3 received by the gate electrode of the fourth transistor M4, and the first scan signal SCAN1 received by the gate electrode of the sixth transistor M6 are all high-level signals. At this time, the second transistor M2, the fourth transistor M4 and the sixth transistor M6 are turned on. The electrical potential of the first node N1 is still equal to the data voltage signal Vdata. The second transistor M2 provides a second fixed electrical potential V2 to the first electrode of the second capacitor C2. Therefore, the electrical potential of the first electrode of the second capacitor C2 jumps from the first fixed electrical voltage V1 to the second fixed electrical potential V2, that is, a voltage jump of ΔV is generated, wherein ΔV=V2−V1. The second node N2 jumps C1*ΔV/(C1+C2) correspondingly, wherein C1 is the capacitance of the first capacitor C1, C2 is the capacitance of the second capacitor C2. The voltage range between the two ends of the first capacitor C1 is Vdata−VN2−C1*ΔV/(C1+C2). When the sixth transistor M6 is turned off, the voltage of the first node N1 and the voltage of the second node N2 are stored in the first capacitor C1 and the second capacitor C2.
In the time period from T4 (i.e., the light-emitting stage), the second control signal SW2 received by the gate electrode of the second transistor M2, the third control signal XSW3 received by the gate electrode of the third transistor M3, the second scan signal SCAN2 received by the gate electrode of the fifth transistor M5 and the first scan signal SCAN1 received by the gate electrode of the sixth transistor M6 are all low-level signals. The first control signal SW1 received by the gate electrode of the first transistor M1, the fourth control signal SW3 received by the gate electrode of the fourth transistor M4, and the light-emitting control signal Emit received by the gate electrode of the seventh transistor M7 are all high-level signals. At this time, the seventh transistor M7 is turned on, and the light-emitting current is: IMD=k*(Vdata-VN2− Vth)2. As the voltage of the second node N2 includes the information of the threshold voltage Vth of the driving transistor MD, the threshold voltage compensation of the driving transistor MD is realized, the light-emitting element 22 is not impacted by the threshold voltage Vth, the unity in display is improved. Even if the light emitted by the light-emitting element attenuates and the voltage of the second node floats, the voltage of the first node will change correspondingly under the coupling effect of the capacitor C1 to inhibit the attenuation influence of the light emitted by the light-emitting element, thus the uniformity of the display panel will be improved. In addition, because the first electrode of the second capacitor C2 connected to the voltage is capable of jumping, the electrical potential of the second node N2 is raised by ΔV/(C1+C2), therefore, the gate-source voltage Vgs is decreased by subtracting ΔV/(C1+C2) from the original voltage, therefore, the data range of the pixel circuit is increased and the gamma of 0-255 gray scale can be easily adjusted.
It should be understood that, under the premise of the functions of the pixel circuit, the second signal module and the first signal module can be realized, the sequence view of the pixel circuit, the second signal module and the first signal module is not limited to
Optionally, the first voltage signal V1 is a first power signal VP1 transmitted by the first power signal end VP+; or the second voltage signal V2 is a second power signal VP2 transmitted by the second power signal end VP−. The arrangement has the advantages that there is no need to provide separate signal lines for the first voltage signal V1 or the second voltage signal V2, the structure of the pixel circuit is simplified, and the producing efficiency of the display panel is improved.
Optionally, the first capacitor C1 can be a MIN capacitor or a MOS capacitor, and the second capacitor C2 can be a MIN capacitor. It should be understood, the types of the first capacitor C1 and the second capacitor C2 are not limited to this, those skilled in the art can choose the types of the capacitors according to actual situations, and not limited to the embodiment.
Based on a same concept with the above display panel, the present disclosure further provides a driving method of a display panel. The method can be applied to drive the display panel described above. The technical features not described in detail here can refer to the features in the embodiments of the display panel described above. As shown in
S110: in a reset stage, providing, by the reset module, a reset signal to the anode of the light-emitting element through the light-emitting control module;
S120: in a data-writing stage, providing, by the first signal module, a data voltage signal to the data-writing module to write the data voltage signal to the gate electrode of the driving transistor and the first end of the first memory module through the data-writing module, and providing, by the first signal module, a data current signal to the driving transistor to compensate the threshold voltage of the driving transistor to the second node;
S130: in a light-emitting stage, controlling, by the light-emitting control module, the driving current generated by the driving transistor to flow into the light-emitting element to drive the light-emitting element to emit light.
By using the driving method of a display panel, the first signal module provides a data voltage signal to the data-writing module to write the data voltage signal to the gate electrode of the driving transistor and the first end of the first memory module through the data-writing module, and the first signal module provides a data current signal to the driving transistor to compensate the threshold voltage of the driving transistor to the second voltage to realize the threshold voltage compensation. In addition, when the first memory module is a capacitor, even if the light emitted by the light-emitting element attenuates and the voltage of the second node floats, the voltage of the first node will change along under the coupling effect of the capacitor to inhibit the attenuation influence of the light emitted by light-emitting element, therefore the uniformity of the display panel will be improved.
In one embodiment, the display panel further includes at least one second signal module for providing a jump signal, the pixel circuit further includes a second memory module, and the data-writing stage includes a first stage and a second stage.
S210: in a reset stage, providing, by the reset module, the reset signal to an anode of the light-emitting element through the light-emitting control module, and providing, by the second signal module, a first voltage signal to the first end of the second storage module;
S220: in the first stage, providing, by the first signal module, the data voltage signal to the data-writing module to write the data voltage signal to the gate electrode of the driving transistor and the first end of the first memory module through the data-writing module, providing, by the first signal module, the data current signal to the driving transistor to compensate the threshold voltage of the driving transistor to the second node; continuously providing, by the second signal module, a first voltage signal to the first end of the second memory module;
S230: in the second stage, providing, by the second signal module, a second voltage signal to the first end of the second memory module to change the voltage signal of the second node; wherein the second voltage signal is greater than the first voltage signal;
S240: in a light-emitting stage, controlling, by the light-emitting control module, the driving current generated by the driving transistor to flow into the light-emitting element to drive the light-emitting element to emit light.
In the illustrated embodiment, with the arrangement of the second signal module, the electrical potential of the second node is raised, and the gate-drain voltage is decreased correspondingly from the basis of the original voltage, which results in the increase of the data range of the pixel circuit. Thus, the gamma of 0-255 gray scale can be easily adjusted.
Based on a same concept with the above display panel, the present disclosure further provides a display device.
The above is a detailed description of the present disclosure in connection with the specific preferred embodiments, and the specific embodiments of the present disclosure are not limited to the description. Modifications and substitutions can be made without departing from the spirit and scope of the present disclosure.
Number | Date | Country | Kind |
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202011608249.2 | Dec 2020 | CN | national |
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20060232522 | Roy | Oct 2006 | A1 |
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20170278457 | Zhu | Sep 2017 | A1 |
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20210125568 | Yuan | Apr 2021 | A1 |
Number | Date | Country | |
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20220208120 A1 | Jun 2022 | US |