CN114170990A - Display panel, ambient light detection driving method thereof and display device - Google Patents

Display panel, ambient light detection driving method thereof and display device Download PDF

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CN114170990A
CN114170990A CN202111476604.XA CN202111476604A CN114170990A CN 114170990 A CN114170990 A CN 114170990A CN 202111476604 A CN202111476604 A CN 202111476604A CN 114170990 A CN114170990 A CN 114170990A
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electrically connected
transistor
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module
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CN114170990B (en
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张蒙蒙
李玥
黄静
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Wuhan Tianma Microelectronics Co Ltd
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Wuhan Tianma Microelectronics Co Ltd
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    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09GARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G5/00Control arrangements or circuits for visual indicators common to cathode-ray tube indicators and other visual indicators
    • G09G5/10Intensity circuits
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01JMEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J1/00Photometry, e.g. photographic exposure meter
    • G01J1/42Photometry, e.g. photographic exposure meter using electric radiation detectors
    • G01J1/4204Photometry, e.g. photographic exposure meter using electric radiation detectors with determination of ambient light
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01JMEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J1/00Photometry, e.g. photographic exposure meter
    • G01J1/42Photometry, e.g. photographic exposure meter using electric radiation detectors
    • G01J1/44Electric circuits
    • G01J1/46Electric circuits using a capacitor
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01JMEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J1/00Photometry, e.g. photographic exposure meter
    • G01J1/42Photometry, e.g. photographic exposure meter using electric radiation detectors
    • G01J1/44Electric circuits
    • G01J2001/4446Type of detector
    • G01J2001/4473Phototransistor
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09GARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00Control of display operating conditions
    • G09G2320/06Adjustment of display parameters
    • G09G2320/0626Adjustment of display parameters for control of overall brightness

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  • Engineering & Computer Science (AREA)
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  • Spectroscopy & Molecular Physics (AREA)
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  • Theoretical Computer Science (AREA)
  • Power Engineering (AREA)
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  • Sustainable Development (AREA)
  • Control Of Indicators Other Than Cathode Ray Tubes (AREA)

Abstract

The invention provides a display panel, an ambient light detection driving method thereof and a display device, which are used for enabling the display panel to have an ambient light detection function and reducing the manufacturing cost of the display panel. The display panel comprises a photosensitive transistor, a first electrode of the photosensitive transistor is electrically connected with the first fixed signal end, and a second electrode of the photosensitive transistor is electrically connected with the first node; the first end of the first reset module is electrically connected with the reset signal end, and the second end of the first reset module is electrically connected with the first node; a voltage following module, a first end of which is electrically connected with the first node, and a second end of which is electrically connected with the second node; and the calculation module is electrically connected with the second node and used for recording the signal value of the second node as a first signal value after the first node is reset, recording the signal value of the second node as a second signal value after the photosensitive transistor is exposed, obtaining the photocurrent of the photosensitive transistor according to the first signal value and the second signal value respectively, and obtaining the illumination intensity sensed by the display panel according to the photocurrent.

Description

Display panel, ambient light detection driving method thereof and display device
[ technical field ] A method for producing a semiconductor device
The invention relates to the technical field of display, in particular to a display panel, an ambient light detection driving method thereof and a display device.
[ background of the invention ]
With the continuous development of display technologies, mobile terminals such as smart phones have been widely used in daily life of people. In recent years, terminal devices with ambient light sensing function have gradually appeared to save power consumption and improve user experience.
At present, a terminal device having an ambient light sensing function is mainly implemented by additionally mounting an ambient light sensor on one side of a display panel. By adopting the arrangement mode, the cost of the terminal equipment can be greatly increased, and the ambient light sensor needs to collect ambient light during working, so that the requirement on the light transmittance of the display panel is higher.
[ summary of the invention ]
In view of this, embodiments of the present invention provide a display panel, an ambient light detection driving method thereof, and a display device, so that the display panel can realize an ambient light sensing function at a low cost.
In one aspect, an embodiment of the present invention provides a display panel, including:
the first electrode of the photosensitive transistor is electrically connected with the first fixed signal end, and the second electrode of the photosensitive transistor is electrically connected with the first node;
the first end of the first reset module is electrically connected with a reset signal end, and the second end of the first reset module is electrically connected with the first node;
a voltage following module, a first end of the voltage following module is electrically connected with the first node, and a second end of the voltage following module is electrically connected with the second node;
the computing module is electrically connected with the second node; the calculation module is used for recording the signal value of the second node as a first signal value after the first node is reset, recording the signal value of the second node as a second signal value after the photosensitive transistor is exposed, obtaining the photocurrent of the photosensitive transistor according to the first signal value and the second signal value respectively, and obtaining the illumination intensity sensed by the display panel according to the photocurrent.
In another aspect, an embodiment of the present invention provides an ambient light detection driving method for a display panel, where the display panel includes:
the first electrode of the photosensitive transistor is electrically connected with the first fixed signal end, and the second electrode of the photosensitive transistor is electrically connected with the first node;
the first end of the first reset module is electrically connected with a reset signal end, and the second end of the first reset module is electrically connected with the first node;
a voltage following module, a first end of the voltage following module is electrically connected with the first node, and a second end of the voltage following module is electrically connected with the second node;
the computing module is electrically connected with the second node;
the driving method includes:
in a first reset stage, resetting the first node by using the first reset module;
in a first reading stage, recording a signal value of the second node in the first resetting stage as a first signal value by using the calculation module;
in a leakage current stage, exposing the photosensitive transistor, wherein the photosensitive transistor generates photocurrent, so that the potential of the first node is changed;
in a second reading stage, recording a signal value of the second node in the leakage stage as a second signal value by using the calculation module;
in the calculation stage, the calculation module is used for obtaining the photocurrent of the photosensitive transistor according to the first signal value and the second signal value, and obtaining the illumination intensity sensed by the display panel according to the photocurrent.
In another aspect, an embodiment of the present invention provides a display device, including the display panel described above.
According to the display panel, the ambient light detection driving method and the display device provided by the embodiment of the invention, the photosensitive circuit is integrated in the display panel, and the ambient light sensor is not required to be additionally arranged, so that the manufacturing cost of the display panel is favorably reduced. In addition, the setting mode provided by the embodiment of the invention can enable the photosensitive circuit to avoid the setting of the pixel driving circuit, can avoid the influence of the setting of the photosensitive circuit on the pixel driving circuit, can enable the display panel to realize the ambient light detection function, can also realize high PPI display, and has better low-frequency display effect.
In addition, the voltage following module is arranged in the photosensitive circuit, so that the second node can stably output the signal capable of reflecting the potential of the first node, the calculation module can obtain the illumination intensity according to the signal of the second node output by the voltage following module, the calculation module is prevented from directly obtaining the illumination intensity according to the signal of the first node, and the accuracy of illumination intensity calculation can be improved.
In addition, in the embodiment of the invention, the calculation module is enabled to record the first signal value and the second signal value respectively in one driving period, wherein the first signal value is read after the first node is reset, the second signal value is read after the photosensitive transistor is exposed for a period of time, and then photocurrent is obtained according to the first signal value and the second signal value, which is equivalent to double sampling, so that the influence of noise can be effectively reduced, and the accuracy of illumination intensity calculation can be further improved.
[ description of the drawings ]
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a diagram of a light sensing circuit according to an embodiment of the present invention;
FIG. 2 is a diagram of another optical sensing circuit according to an embodiment of the present invention;
FIG. 3 is a diagram of another optical sensing circuit according to an embodiment of the present invention;
FIG. 4 is a diagram of another optical sensing circuit according to an embodiment of the present invention;
FIG. 5 is a diagram of another optical sensing circuit according to an embodiment of the present invention;
FIG. 6 is a diagram of another optical sensing circuit according to an embodiment of the present invention;
FIG. 7 is a diagram of another optical sensing circuit according to an embodiment of the present invention;
FIG. 8 is a diagram of another optical sensing circuit according to an embodiment of the present invention;
FIG. 9 is a schematic diagram of a working timing sequence of a light sensing circuit according to an embodiment of the present invention;
fig. 10 is a schematic diagram of a display device according to an embodiment of the present invention.
[ detailed description ] embodiments
For better understanding of the technical solutions of the present invention, the following detailed descriptions of the embodiments of the present invention are provided with reference to the accompanying drawings.
It should be understood that the described embodiments are only some embodiments of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the examples of the present invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
It should be understood that the term "and/or" as used herein is merely one type of association that describes an associated object, meaning that three relationships may exist, e.g., a and/or B may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein generally indicates that the former and latter related objects are in an "or" relationship.
It should be understood that although the terms first, second, third, etc. may be used to describe transistors in embodiments of the present invention, these transistors should not be limited to these terms. These terms are only used to distinguish transistors from one another. For example, a first transistor may also be referred to as a second transistor, and similarly, a second transistor may also be referred to as a first transistor, without departing from the scope of embodiments of the present invention.
The embodiment of the invention provides a display panel, which comprises a light sensing circuit. As shown in fig. 1, fig. 1 is a schematic diagram of a photo circuit according to an embodiment of the present invention, the photo circuit includes a photo transistor M0, a first pole of the photo transistor M0 is electrically connected to a first fixed signal terminal Vc, and a second pole of the photo transistor M0 is electrically connected to a first node N1. Under illumination, photo-generated carriers are generated in the photo transistor M0, and the drift of the photo-generated carriers can form a photocurrent, so that the potential of the first node N1 can be changed. That is, the photo transistor M0 can convert the optical signal into an electrical signal.
Illustratively, the photo transistor M0 may be a triode. When the phototransistor M0 is configured as a triode, as shown in fig. 1, its gate may receive a fixed signal that is set to ensure that the phototransistor M0 is off in the absence of light. For example, when the photo transistor M0 is configured as a P-type transistor, the embodiment of the invention may electrically connect the high-level signal terminal VGH with the control electrode of the photo transistor M0. When the photo transistor M0 is an N-type transistor, the embodiment of the invention may electrically connect the low-level signal terminal VGL with the control electrode of the photo transistor M0. Alternatively, in the embodiment of the present invention, the light sensing transistor M0 may be configured as a diode, an anode of the diode is connected to the low level signal, and a cathode of the diode is connected to the high level signal, so that the light sensing transistor M0 is in a reverse bias off state when there is no illumination. In fig. 1, the light sensing transistor M0 is a P-type transistor, and its control electrode and the high-level signal terminal VGH are taken as an example.
As shown in fig. 1, the light sensing circuit further includes a first reset module 11, a voltage following module 12, and a calculation module 13. A first terminal of the first reset module 11 is electrically connected to the reset signal terminal Va, and a second terminal of the first reset module 11 is electrically connected to the first node N1. The first terminal of the voltage follower module 12 is electrically connected to the first node N1, and the second terminal of the voltage follower module 12 is electrically connected to the second node N2. The input of the calculation module 13 is electrically connected to the second node N2.
The first reset module 11 is configured to reset the potential of the first node N1 to an initial potential after each driving cycle is completed, so as to prevent the first node N1 from remaining the potential of the previous driving cycle in the next driving cycle, and in the next driving cycle, the first node N1 starts to be charged from the initial potential, so as to improve the charging accuracy of the first node N1. When the signal of the reset signal terminal Va is selected, the embodiment of the present invention may make the signal of the reset signal terminal Va different from the signal of the first fixed signal terminal Vc, so as to ensure that the photo transistor M0 can form a photo current flowing between the first fixed signal terminal Vc and the first node N1 under the illumination.
The voltage follower module 12 is set to establish a correspondence between the potential of the second node N2 and the potential of the first node N1. The calculating module 13 is configured to record the signal value of the second node N2 as a first signal value after the first node N1 is reset, record the signal value of the second node N2 as a second signal value after the photo transistor M0 is exposed, obtain a photo current of the photo transistor M0 according to the first signal value and the second signal value, and obtain the intensity of light sensed by the display panel according to the photo current.
For example, the display panel may store a photocurrent versus illumination intensity curve in advance. After the photocurrent of the phototransistor M0 is obtained according to the calculating module 13, the intensity of the light sensed by the display panel can be obtained according to the relationship curve.
When the light sensing circuit operates to detect the intensity of ambient light, the first node N1 is first reset by the first reset module 11. Due to the arrangement of the voltage follower module 12, the signal of the second node N2 will follow the variation of the signal of the first node N1, and after the first node N1 is reset, the signal value of the second node N2 is recorded as the first signal value by the calculation module 13. Then, the first reset module 11 is controlled to stop operating. In this process, the photo transistor M0 is illuminated to generate a photo current, so that the potential at the first node N1 changes. The signal at the second node N2 follows the variation of the signal at the first node N1. After a certain period of exposure, the signal value of the second node N2 is recorded as a second signal value by the calculation module 13.
When the photo transistor M0 is exposed, the intensity of the light received by the photo transistor M0 determines the magnitude of the photocurrent generated by the photo transistor M0. The magnitude of the photocurrent of the photo transistor M0 determines the potentials of the first node N1 and the second node N2. Therefore, the calculation module 13 may obtain the photocurrent generated by the photo transistor M0 according to the first signal value and the second signal value respectively obtained before and after the exposure, and obtain the illumination intensity sensed by the photo transistor M0 according to the photocurrent, thereby implementing the determination of the brightness of the ambient light. The subsequent calculating module 13 may feed back the ambient light brightness information to the driving chip, and the driving chip may perform corresponding actions according to the ambient light brightness information, for example, may determine the brightness to be displayed by the display panel and the turning on or adjusting of some other functions in the display panel.
In the embodiment of the present invention, the first reset module 11, the voltage following module 12 and the calculating module 13 may include one or more thin film transistors, and the first reset module 11, the voltage following module 12, the calculating module 13 and the photo transistor M0 may be formed through a semiconductor process. For example, the thin film transistor for driving the sub-pixels to be turned on in the display panel and at least part of the structure of the photosensitive circuit may be formed in the same process, so as to integrate the photosensitive circuit inside the display panel, which not only simplifies the structure of the display panel and improves the integration level of the display panel, but also greatly reduces the manufacturing cost of the display panel with the ambient light intensity sensing function.
In the process of implementing the embodiment of the present invention, the inventor researches and discovers that in the related art, sensing of the ambient light intensity by the display panel is mainly achieved by placing the ambient light sensor below the display panel, which is not only costly, but also requires that the position of the display panel where the ambient light sensor is correspondingly disposed has a high light transmittance, thereby causing a limitation on the number of Pixels (PPI) possessed by the display panel Per Inch. Particularly, when the display panel needs to realize low-frequency display, a storage capacitor is usually added in the pixel driving circuit to maintain the stability of the low-frequency display, and since the light transmittance of the storage capacitor is low, the added storage capacitor inevitably reduces the light transmittance at a corresponding position, so that the display panel cannot well realize multiple functions of low-frequency display, ambient light sensing and the like.
According to the embodiment of the invention, the photosensitive circuit is integrated in the display panel, and an additional ambient light sensor is not required, so that the cost is reduced. In addition, the setting mode provided by the embodiment of the invention can enable the photosensitive circuit to avoid the setting of the pixel driving circuit, can avoid the influence on the pixel driving circuit caused by the setting of the photosensitive circuit, can enable the display panel to realize the ambient light detection function, can still realize high PPI display, and has better low-frequency display effect.
In addition, in the embodiment of the present invention, by providing the voltage follower module 12 in the photosensitive circuit, the second node N2 can stably output a signal capable of reflecting the potential of the first node N1, and the calculation module 13 can obtain the illumination intensity according to the signal of the second node N2 output by the voltage follower module 12, so as to avoid that the calculation module 13 directly obtains the illumination intensity according to the signal of the first node N1, and improve the accuracy of the illumination intensity calculation.
In addition, in the embodiment of the present invention, the calculation module 13 records the first signal value and the second signal value in one driving cycle, respectively, where the first signal value is read after resetting the first node N1, the second signal value is read after exposing the phototransistor M0 for a period of time, and then a photocurrent is obtained according to the first signal value and the second signal value, which is equivalent to performing double sampling, so that the influence of noise can be effectively reduced, and the accuracy of calculating the illumination intensity can be further improved.
For example, as shown in fig. 2, fig. 2 is a schematic diagram of another light sensing circuit provided in the embodiment of the present invention, and the display panel further includes a control module 14 and a second reset module 15; a first terminal of the control module 14 is electrically connected to the first node N1, and a second terminal of the control module 14 is electrically connected to the third node N3; a first end of the second reset module 15 is electrically connected with the reset signal end Va, and a second end of the second reset module 15 is electrically connected with the third node N3; the first terminal of the voltage follower module 12 is electrically connected to the first node N1 through the third node N3 and the control module 14.
In the embodiment of the present invention, the second reset module 15 is configured to reset the potential of the third node N3 to the signal provided by the reset signal terminal Va after each driving cycle is finished (hereinafter, the signal provided by the reset signal terminal Va is denoted by Va), so as to prevent the third node N3 from remaining the potential of the previous driving cycle in the next driving cycle, and the third node N3 starts to charge from Va in the next driving cycle, so as to improve the charging accuracy of the third node N3. Furthermore, in the embodiment of the present invention, by connecting both the first reset block 11 and the second reset block 15 to the reset signal terminal Va, the reset potential of the third node N3 can be used as the reset potential of the first node N1. That is, the calculation module 13 may be caused to record the signal value of the second node N2 as the first signal value after the third node N3 is reset.
The settings of the control module 14 may be used to control the timing of the reading of the second signal value. In the working process of the light sensing circuit, after the third node N3 is reset and the light sensing transistor M0 is exposed for a period of time, the control module 14 is turned on to connect the first node N1 and the third node N3, that is, the first node N1 containing the photocurrent information transmits the photocurrent information to the third node N3, then the voltage following module 12 reacts the signal of the third node N3 on the second node N2, and the calculation module 13 takes the signal of the second node N2 read at this time as a second signal value.
For example, the embodiment of the present invention may make the conduction period of the second reset module 15 and the conduction period of the control module 14 adjacent to each other, and make the conduction period of the first reset module 11 and the conduction period of the control module 14 separated by a period of time, that is, after making the first reset module 11 conduct to reset the first node N1, make the light sensing transistor M0 exposed for a period of time, then make the second reset module 15 conduct to reset the third node N3 and record the value of the second node N2 as the first signal value in the period of time, and then make the control module 14 conduct soon, so as to make the first node N1 signal containing the photocurrent information transmit to the third node N3, and record the value of the second node N2 as the second signal value in the period of time. By the arrangement, the reading time of the first signal value and the reading time of the second signal value can be ensured to be close to each other, so that the noise information contained in the first signal value and the second signal value tends to be consistent, the influence of noise can be reduced or even eliminated after the first signal value and the second signal value are processed, and the accuracy of a calculation result is improved.
Alternatively, as shown in fig. 3, fig. 3 is a schematic diagram of another light sensing circuit according to an embodiment of the invention, the first reset module 11 includes a first transistor M1, a first electrode of the first transistor M1 is electrically connected to the reset signal terminal Va, a second electrode of the first transistor M1 is electrically connected to the first node N1, and a control electrode of the first transistor M1 is electrically connected to the first control terminal S1. The first transistor M1 may be turned on or off by a signal provided from the first control terminal S1. When the first transistor M1 is controlled to be turned on, the reset signal terminal Va resets the first node N1.
As shown in fig. 3, the second reset module 15 includes a second transistor M2, a first pole of the second transistor M2 is electrically connected to the reset signal terminal Va, a second pole of the second transistor M2 is electrically connected to the third node N3, and a control pole of the second transistor M2 is electrically connected to the second control terminal S2. The second transistor M2 may be turned on or off by a signal provided from the second control terminal S2. When the second transistor M2 is controlled to be turned on, the reset signal terminal Va resets the third node N3.
For example, as shown in fig. 4, fig. 4 is a schematic diagram of another light sensing circuit according to an embodiment of the invention, the control module 14 includes a third transistor M3, a first pole of the third transistor M3 is electrically connected to a first node N1, a second pole of the third transistor M3 is electrically connected to a third node N3, and a control pole of the third transistor M3 is electrically connected to a third control terminal S3. The third transistor M3 may be turned on or off by a signal provided from the third control terminal S3. When the third transistor M3 is controlled to be turned on, the potential of the first node N1 is the same as the potential of the third node N3.
Alternatively, as shown in fig. 5, fig. 5 is a schematic diagram of another light sensing circuit according to an embodiment of the present invention, and the calculating module 13 includes a first storage capacitor C1 and a second storage capacitor C2. The first storage capacitor C1 is electrically connected to the second node N2, and the first storage capacitor C1 is configured to store the signal value at the second node N2 as the first signal value when the control module 14 is turned off. The second storage capacitor C2 is electrically connected to the second node N2, and the second storage capacitor C2 is used for storing the signal value of the second node N2 as the second signal value when the control module 14 is turned on.
As shown in fig. 5, the calculating module 13 includes a differential amplifier 130, a first input terminal of the differential amplifier 130 is electrically connected to the first storage capacitor C1, and a second input terminal of the differential amplifier 130 is electrically connected to the second storage capacitor C2.
Illustratively, with continued reference to fig. 5, the computing module 13 further includes a fourth transistor M4, a fifth transistor M5, a sixth transistor M6, and a seventh transistor M7. A first pole of the fourth transistor M4 is electrically connected to the second node N2, a second pole of the fourth transistor M4 is electrically connected to the first storage capacitor C1, and a control pole of the fourth transistor M4 is electrically connected to the fourth control terminal S4. A first pole of the fifth transistor M5 is electrically connected to the first storage capacitor C1, a second pole of the fifth transistor M5 is electrically connected to the first input terminal of the differential amplifier 130, and a control pole of the fifth transistor M5 is electrically connected to the fifth control terminal S5. A first pole of the sixth transistor M6 is electrically connected to the second node N2, a second pole of the sixth transistor M6 is electrically connected to the second storage capacitor C2, and a control pole of the sixth transistor M6 is electrically connected to the sixth control terminal S6. A first pole of the seventh transistor M7 is electrically connected to the second storage capacitor C2, a second pole of the seventh transistor M7 is electrically connected to the second input terminal of the differential amplifier 130, and a control pole of the seventh transistor M7 is electrically connected to the fifth control terminal S5.
When the photosensitive circuit is operated, the active level of the fourth control terminal S4 may be located after the second reset module 15 is turned on, i.e., after the third node N3 is reset, so that the first storage capacitor C1 connected to the fourth transistor M4 stores the signal of the second node N2 as the first signal value.
The active level of the sixth control terminal S6 may be set after the control module 14 is turned on, i.e. after the light sensing transistor M0 is exposed for a period of time, the control module 14 is turned on, and the second storage capacitor C2 connected to the sixth transistor M6 stores the signal of the second node N2 as the second signal value.
In the embodiment of the present invention, the fifth transistor M5 and the seventh transistor M7 are turned on simultaneously to provide the first signal and the second signal to the differential amplifier 130 simultaneously, and the differential amplifier 130 may perform a difference process on the first signal and the second signal to obtain a photocurrent signal generated by the photo transistor.
Illustratively, as shown in fig. 1 to 5, the light sensing circuit further includes a third storage capacitor C3. The third storage capacitor C3 includes a first plate electrically connected to the first node N1 and a second plate electrically connected to the fixed signal terminal. For example, the embodiment of the present invention may electrically connect the second plate of the third storage capacitor C3 with the reset signal terminal Va. When the photo transistor M0 is exposed, the photo current flows through the photo transistor M0 to the third storage capacitor C3, and is accumulated as electric charge on the third storage capacitor C3 to charge the third storage capacitor C3. When the control module 14 is turned on to read the second signal value, the third storage capacitor C3 may discharge the stored charge.
For example, as shown in fig. 6, fig. 6 is a schematic diagram of another light sensing circuit according to an embodiment of the present invention, and the voltage follower module 12 includes an eighth transistor M8 and a ninth transistor M9. A control electrode of the eighth transistor M8 is electrically connected to the third fixed signal terminal Vb, a first electrode of the eighth transistor M8 is electrically connected to the fourth fixed signal terminal Vd, and a second electrode of the eighth transistor M8 is electrically connected to the second node N2. A control electrode of the ninth transistor M9 is electrically connected to the third node N3, a first electrode of the ninth transistor M9 is electrically connected to the second node N2, and a second electrode of the ninth transistor M9 is electrically connected to the fifth fixed signal terminal Ve.
In the embodiment of the present invention, by properly selecting the signals of the third fixed signal terminal Vb, the fourth fixed signal terminal Vd, and the fifth fixed signal terminal Ve, the eighth transistor M8 and the ninth transistor M9 can be normally open when the photosensitive circuit operates, and the eighth transistor M8 and the ninth transistor M9 can operate in a saturation region. The conduction current I of the transistor in a saturation region meets the following conditions:
Figure BDA0003393651100000111
where W is the channel width of the transistor, L is the channel length of the transistor, μ is the equivalent carrier mobility of the transistor, Cox is the gate insulator capacitance of the transistor, and VgsThe difference in gate-source voltages of the transistors, Vth, is the threshold voltage of the transistor.
After the eighth transistor M8 and the ninth transistor M9 are determined, W, L, μ, Cox, and Vth of both are determined. In the embodiment of the present invention, as shown in fig. 6, the eighth transistor M8 and the ninth transistor M9 are connected in series between the fourth fixed signal terminal Vd and the fifth fixed signal terminal Ve, and the same current flows through the eighth transistor M8 and the ninth transistor M9 when they are turned on. Thus, V can be obtainedgs_M8V betweengs_M9The relational expression (c) of (c). Wherein, Vgs_M8Is the gate-source voltage difference, V, of the eighth transistor M8gs_M9Is the gate-source voltage difference of the ninth transistor M9. Based on the circuit shown in FIG. 6, the gate-source voltage difference V of the eighth transistor M8gs_M8Vb-Vd; the gate-source voltage difference V of the ninth transistor M9gs_M9=VN3-VN2. Wherein, VN3Is the voltage of the third node N3, VN2Is the voltage of the second node N2. Accordingly, a relationship between the voltage of the third node N3 and the voltage of the second node N2 can be obtained. That is, the third node N3 can be made to reflect the potential of the second node N2.
In addition, in the embodiment of the invention, the eighth transistor M8 and the ninth transistor M9 are connected in series between the fourth fixed signal terminal Vd and the fifth fixed signal terminal Ve, so that the potential of the second node N2 is stable and is not affected by other branches connected with the second node N2. And the calculation module 13 is connected with the second node N2, and the photocurrent generated by the light sensing transistor M0 is calculated according to the potential of the second node N2, so that the accuracy of the calculation result can be improved. If the calculating module 13 is directly connected to the first node N1 or the third node N3, the charge on the first node N1 or the third node N3 will be diluted by the circuit formed by the calculating module 13.
Optionally, in the embodiment of the present invention, the channel types of the eighth transistor M8 and the ninth transistor M9 may be the same, so that the equivalent carrier mobility and the threshold voltage of the eighth transistor M8 and the ninth transistor M9 are equal, the relationship between the voltage of the third node N3 and the voltage of the second node N2 is simplified, and the calculation efficiency is improved. Moreover, when the threshold voltages of the eighth transistor M8 and the ninth transistor M9 are equal, the influence of the threshold voltage can be eliminated when calculating the relationship between the voltage of the third node N3 and the voltage of the second node N2, and the accuracy of the calculation result can be ensured when the threshold voltage shift problem occurs.
Alternatively, the embodiment of the invention may make the types of the channels of the eighth transistor M8 and the ninth transistor M9 the same, and make the channel width-to-length ratios of the eighth transistor M8 and the ninth transistor M9 the same. The structures of the eighth transistor M8 and the ninth transistor M9 are completely the same, that is, W, L, μ, Cox and Vth are the same, and it can be obtained that: vgs_M8=Vgs_M9And Vb-Vd ═ V can be obtainedN3-VN2. The embodiment of the invention can establish V by selecting the values of Vb and VdN2And VN3The relational expression (c) of (c).
For example, as shown in fig. 6, in the embodiment of the present invention, the eighth transistor M8 and the ninth transistor M9 may be both P-type transistors. In the case that both are set as P-type tubes, the embodiment of the present invention may make the signal of the fifth fixed signal end Ve smaller than the signal of the fourth fixed signal end Vd. Illustratively, the fifth fixed signal terminal Ve may be grounded. And enabling the signal of the reset signal end Va to be smaller than the signal of the third fixed signal end Vb, and enabling the signal of the third fixed signal end Vb to be smaller than the signal of the fourth fixed signal end Vd. With this arrangement, the eighth transistor M8 and the ninth transistor M9 can be operated in the saturation region.
Alternatively, as shown in fig. 7, fig. 7 is a schematic diagram of another light sensing circuit according to an embodiment of the present invention, and in an embodiment of the present invention, both the eighth transistor M8 and the ninth transistor M9 may be N-type transistors. When the eighth transistor M8 and the ninth transistor M9 are both N-type transistors, the embodiment of the present invention may make the signal of the fifth fixed signal terminal Ve greater than the signal of the fourth fixed signal terminal Vd, and make the signal of the reset signal terminal Va greater than the signal of the third fixed signal terminal Vb, and make the signal of the third fixed signal terminal Vb greater than the signal of the fourth fixed signal terminal Vd. With this arrangement, the eighth transistor M8 and the ninth transistor M9 can be operated in the saturation region.
With reference to fig. 8 and 9, fig. 8 is a schematic diagram of another light sensing circuit according to an embodiment of the present invention, and fig. 9 is a schematic diagram of an operation timing sequence of the light sensing circuit according to the embodiment of the present invention, and an operation process of the light sensing circuit is described, where the operation process of the light sensing circuit includes a first reset stage T1, a drain stage T2, a first reading stage T3, a second reading stage T4, and a calculating stage T5.
In the first reset phase T1: the first control terminal S1 controls the first transistor M1 to be turned on, and the voltage at the reset signal terminal Va is transmitted to the first node N1 through the first transistor M1, so as to reset the first node N1. VN1=Va。
In the drain period T2, the phototransistor M0 is continuously exposed, and the phototransistor M0 generates a photocurrent, so that the potential of the first node N1 changes. The potential after change was: vN1=Va+△Vioff. Wherein, Δ VioffThe voltage change amount of the first node N1 before and after exposure.
In the first reading phase T3, the second control terminal S2 controls the second transistor M2 to be turned on, and the voltage at the reset signal terminal Va is transmitted to the third node N3 through the second transistor M2, so as to reset the third node N3. VN3Va. Under the control of the third node N3,the ninth transistor M9 is turned on, and the potential of the second node N2 can change following the change of the potential of the third node N3, that is, the potential of the third node N3 can reflect the potential of the second node N2. VN2=VN3And + Vb-Vd is Va + Vb-Vd. Also, the fourth control terminal S4 controls the fourth transistor M4 to be turned on, and the signal of the second node N2 is written into the first storage capacitor C1 through the fourth transistor M4 as the first signal value.
In the second read phase T4, the third control terminal S3 controls the third transistor M3 to be turned on. The potential of the third node N3 is the same as the potential of the first node N1, VN3=VN1=Va+△Vioff. Under the control of the third node N3, the ninth transistor M9 is turned on, and the potential of the second node N2 can follow the change of the potential of the third node N3, that is, the potential of the third node N3 can reflect the potential of the second node N2. VN2=VN3+Vb-Vd=Va+△Vioff+ Vb-Vd. And, the sixth control terminal S6 controls the sixth transistor M6 to be turned on, and the signal of the second node N2 is written into the second storage capacitor C2 through the sixth transistor M6 as the second signal value.
In the calculation stage T5, the fifth control terminal S5 controls the fifth transistor M5 and the seventh transistor M7 to be turned on, the first signal value stored on the first storage capacitor C1 is transmitted to the first input terminal of the differential amplifier 130 through the fifth transistor M5, and the second signal value stored on the second storage capacitor C2 is transmitted to the second input terminal of the differential amplifier 130 through the seventh transistor M7. The differential amplifier 130 obtains Δ Vi according to the first signal value and the second signal valueoff. Since Δ Vioff=IoffX T2/C3, wherein, IoffFor the photocurrent of the phototransistor, T2 is the time of the drain period, and C3 is the capacitance of the third storage capacitor. Therefore, the voltage change amount Δ Vi before and after exposure at the known first node N1offThe photocurrent of the phototransistor M0 can be obtained under the condition of the time T2 of the leakage current stage and the capacitance C3 of the third storage capacitor, and the illumination intensity sensed by the display panel can be obtained subsequently according to the relationship curve between the photocurrent and the illumination intensity.
Optionally, each of the transistors may be a low-temperature polysilicon thin film transistor, an oxide semiconductor thin film transistor, or an amorphous silicon thin film transistor, and may be manufactured together with a pixel circuit in a display panel, so as to simplify a manufacturing process of the display panel.
The embodiment of the invention also provides an ambient light detection driving method of the display panel, and the display panel comprises the photosensitive circuit. As shown in connection with fig. 1, the light sensing circuit includes a light sensing transistor M0. The first pole of the sensing transistor M0 is electrically connected to the first fixed signal terminal Vc, and the second pole of the sensing transistor M0 is electrically connected to the first node N1. The light sensing circuit further comprises a first reset module 11, a voltage following module 12 and a calculation module 13. A first end of the first reset module 11 is electrically connected to the reset signal end Va, and a second end of the first reset module 11 is electrically connected to the first node N1; a first terminal of the voltage follower module 12 is electrically connected to the first node N1, and a second terminal of the voltage follower module 12 is electrically connected to the second node N2; the calculation module 13 is electrically connected to the second node N2.
The driving method includes:
in the first reset phase, the first node N1 is reset using the first reset module 11.
In the first reading phase, the signal value of the second node N2 in the first reset phase is recorded as the first signal value by the calculation module 13.
In the drain phase, the photo transistor M0 is exposed to light, and the photo transistor M0 generates a photocurrent, so that the potential of the first node N1 changes.
In the second reading phase, the signal value of the second node N2 in the leakage phase is recorded as the second signal value by the calculating module 13.
In the calculation stage, the calculation module 13 is utilized to obtain the photocurrent of the phototransistor M0 according to the first signal value and the second signal value, and obtain the intensity of the light sensed by the display panel according to the photocurrent.
In the embodiment of the present invention, the voltage follower module 12 is disposed in the photosensitive circuit, so that the second node N2 can stably output a signal capable of reflecting the potential of the first node N1, and the calculation module 13 can obtain the illumination intensity according to the signal of the second node N2 output by the voltage follower module 12, thereby preventing the calculation module 13 from directly obtaining the illumination intensity according to the signal of the first node N1, and improving the accuracy of the illumination intensity calculation.
In addition, in the embodiment of the present invention, the calculation module 13 records the first signal value and the second signal value in one driving cycle, respectively, where the first signal value is read after resetting the first node N1, the second signal value is read after exposing the phototransistor M0 for a period of time, and then a photocurrent is obtained according to the first signal value and the second signal value, which is equivalent to performing double sampling, so that the influence of noise can be effectively reduced, and the accuracy of calculating the illumination intensity can be further improved.
Optionally, as shown in fig. 2, the display panel further includes a control module 14 and a second reset module 15. A first terminal of the control module 14 is electrically connected to the first node N1, a second terminal of the control module 14 is electrically connected to the third node N3, a first terminal of the second reset module 15 is electrically connected to the reset signal terminal Va, and a second terminal of the second reset module 15 is electrically connected to the third node N3; the first terminal of the voltage follower module 12 is electrically connected to the first node N1 through the third node N3 and the control module 14.
The driving method further comprises a second reset phase and a control phase; the second reset phase precedes the first read phase, in which the third node N3 is reset by the second reset module 15.
The control phase, between the second read phase and the drain phase, causes the signal from the first node N1 to be written to the third node N3 by the control module 14.
For example, in the embodiment of the present invention, the first reading stage and the second reading stage may be adjacent to each other, that is, the reading time of the first signal value and the reading time of the second signal value are close to each other, so that noise information included in the first signal value and the second signal value may tend to be consistent, and after the first signal value and the second signal value are processed, the influence of noise may be reduced or even eliminated, which is beneficial to improving the accuracy of the calculation result.
As shown in fig. 10, fig. 10 is a schematic view of a display device according to an embodiment of the present invention, where the display device includes the display panel 100. The display panel 100 includes the above-described light sensing circuit. The specific structure of the photosensitive circuit has been described in detail in the above embodiments, and is not described herein again. Of course, the display device shown in fig. 10 is only a schematic illustration, and the display device may be any electronic device with a display function, such as a mobile phone, a tablet computer, a notebook computer, an electronic book, or a television.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (16)

1. A display panel, comprising:
the first electrode of the photosensitive transistor is electrically connected with the first fixed signal end, and the second electrode of the photosensitive transistor is electrically connected with the first node;
the first end of the first reset module is electrically connected with a reset signal end, and the second end of the first reset module is electrically connected with the first node;
a voltage following module, a first end of the voltage following module is electrically connected with the first node, and a second end of the voltage following module is electrically connected with the second node;
the computing module is electrically connected with the second node; the calculation module is used for recording the signal value of the second node as a first signal value after the first node is reset, recording the signal value of the second node as a second signal value after the photosensitive transistor is exposed, obtaining the photocurrent of the photosensitive transistor according to the first signal value and the second signal value respectively, and obtaining the illumination intensity sensed by the display panel according to the photocurrent.
2. The display panel according to claim 1, further comprising:
the display panel further comprises a control module and a second reset module;
the first end of the control module is electrically connected with the first node, and the second end of the control module is electrically connected with the third node; the first end of the second reset module is electrically connected with the reset signal end, and the second end of the second reset module is electrically connected with the third node; the first end of the voltage following module is electrically connected with the first node through the third node and the control module.
3. The display panel according to claim 2,
the first reset module comprises a first transistor, a first electrode of the first transistor is electrically connected with the reset signal end, a second electrode of the first transistor is electrically connected with the first node, and a control electrode of the first transistor is electrically connected with a first control end;
the second reset module comprises a second transistor, a first electrode of the second transistor is electrically connected with the reset signal end, a second electrode of the second transistor is electrically connected with a third node, and a control electrode of the second transistor is electrically connected with a second control end.
4. The display panel according to claim 2, wherein the control module comprises:
a third transistor, a first pole of the third transistor is electrically connected to the first node, a second pole of the third transistor is electrically connected to the third node, and a control pole of the third transistor is electrically connected to a third control terminal.
5. The display panel of claim 2, wherein the computing module comprises:
the first storage capacitor is electrically connected with the second node and used for storing a signal value of the second node when the control module is switched off;
the second storage capacitor is electrically connected with the second node and used for storing a signal value of the second node when the control module is conducted;
and a first input end of the differential amplifier is electrically connected with the first storage capacitor, and a second input end of the differential amplifier is electrically connected with the second storage capacitor.
6. The display panel of claim 5, wherein the computing module further comprises:
a fourth transistor, a first electrode of which is electrically connected to the second node, a second electrode of which is electrically connected to the first storage capacitor, and a control electrode of which is electrically connected to a fourth control terminal;
a first electrode of the fifth transistor is electrically connected with the first storage capacitor, a second electrode of the fifth transistor is electrically connected with the first input end of the differential amplifier, and a control electrode of the fifth transistor is electrically connected with a fifth control end;
a sixth transistor, a first electrode of which is electrically connected to the second node, a second electrode of which is electrically connected to the second storage capacitor, and a control electrode of which is electrically connected to a sixth control terminal;
a first electrode of the seventh transistor is electrically connected to the second storage capacitor, a second electrode of the seventh transistor is electrically connected to the second input terminal of the differential amplifier, and a control electrode of the seventh transistor is electrically connected to the fifth control terminal.
7. The display panel according to claim 1, wherein the voltage following module comprises:
a control electrode of the eighth transistor is electrically connected with the third fixed signal end, a first electrode of the eighth transistor is electrically connected with the fourth fixed signal end, and a second electrode of the eighth transistor is electrically connected with the second node;
and a control electrode of the ninth transistor is electrically connected with the third node, a first electrode of the ninth transistor is electrically connected with the second node, and a second electrode of the ninth transistor is electrically connected with a fifth fixed signal end.
8. The display panel according to claim 7,
the eighth transistor and the ninth transistor are both P-type transistors;
the signal of the fifth fixed signal end is smaller than the signal of the fourth fixed signal end;
the signal of the reset signal end is smaller than the signal of the third fixed signal end, and the signal of the third fixed signal end is smaller than the signal of the fourth fixed signal end.
9. The display panel according to claim 7,
the eighth transistor and the ninth transistor are both N-type transistors;
the signal of the fifth fixed signal end is greater than the signal of the fourth fixed signal end;
the signal of the reset signal end is greater than the signal of the third fixed signal end, and the signal of the third fixed signal end is greater than the signal of the fourth fixed signal end.
10. The display panel according to claim 7, wherein width-to-length ratios of channels of the eighth transistor and the ninth transistor are the same.
11. The display panel according to claim 1, further comprising:
and the third storage capacitor comprises a first polar plate and a second polar plate, the first polar plate is electrically connected with the first node, and the second polar plate is electrically connected with the fixed signal end.
12. The display panel according to claim 1,
the signal of the first fixed signal terminal is different from the signal of the reset signal terminal.
13. An ambient light detection driving method of a display panel, the display panel comprising:
the first electrode of the photosensitive transistor is electrically connected with the first fixed signal end, and the second electrode of the photosensitive transistor is electrically connected with the first node;
the first end of the first reset module is electrically connected with a reset signal end, and the second end of the first reset module is electrically connected with the first node;
a voltage following module, a first end of the voltage following module is electrically connected with the first node, and a second end of the voltage following module is electrically connected with the second node;
the computing module is electrically connected with the second node;
the driving method includes:
in a first reset stage, resetting the first node by using the first reset module;
in a first reading stage, recording a signal value of the second node in the first resetting stage as a first signal value by using the calculation module;
in a leakage current stage, exposing the photosensitive transistor, wherein the photosensitive transistor generates photocurrent, so that the potential of the first node is changed;
in a second reading stage, recording a signal value of the second node in the leakage stage as a second signal value by using the calculation module;
in the calculation stage, the calculation module is used for obtaining the photocurrent of the photosensitive transistor according to the first signal value and the second signal value, and obtaining the illumination intensity sensed by the display panel according to the photocurrent.
14. The driving method according to claim 13, wherein the display panel further comprises a control module and a second reset module;
the first end of the control module is electrically connected with the first node, the second end of the control module is electrically connected with a third node, the first end of the second reset module is electrically connected with the reset signal end, and the second end of the second reset module is electrically connected with the third node; the first end of the voltage following module is electrically connected with the first node through the third node and the control module;
the driving method further comprises a second reset phase and a control phase;
the second reset phase is located before the first reading phase, and the second reset module is used for resetting the third node in the second reset phase;
and the control stage is positioned between the second reading stage and the leakage stage, and in the control stage, the control module is used for writing the signal of the first node into the third node.
15. The driving method according to claim 13,
the first read phase is adjacent to the second read phase.
16. A display device characterized by comprising the display panel according to any one of claims 1 to 12.
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