Fingerprint identification circuit, display panel and display device

Abstract

The application discloses a fingerprint identification circuit, a display panel and a display device. The circuit comprises a photodiode, a first capacitor is formed between the anode and the cathode of the photodiode; a first signal reset module is connected with the cathode of the photodiode and is used for providing a first signal voltage for the cathode of the photodiode; a signal output module is connected with the cathode of the photodiode and is used for generating a corresponding fingerprint identification voltage according to the cathode voltage of the photodiode; and an adaptive adjustment module is used for increasing the equivalent capacitance between the anode and the cathode of the photodiode when the light signal is enhanced. According to the embodiment of the application, adaptive switching under normal environment and strong light environment can be realized, the effectiveness of fingerprint information collection is improved under the strong light environment, and the fingerprint identification effect is guaranteed.

Description

Technical Field

[0001] This application belongs to the field of display technology, and in particular relates to a fingerprint recognition circuit, display panel and display device. Background Technology

[0002] Currently, as smart terminals continue to develop, fingerprint recognition technology is also constantly innovating. Compared to facial recognition, under-display fingerprint recognition has multiple advantages, including high maturity, adaptability to user habits, and lower cost.

[0003] Based on the development trend of under-display fingerprint technology, the technology path is shifting and expanding towards larger areas, thinner designs, and greater integration. For example, the fingerprint recognition module is integrated inside the display panel screen.

[0004] However, the actual light signal is relatively weak when light enters the screen or under the screen, due to the influence of optical transmittance. To improve the quality of the light signal, methods such as changing the light sensor design and adjusting the filter structure are usually used to increase transmittance, thereby enhancing the light signal received by the fingerprint recognition module. However, in strong light environments, device signal saturation can easily occur, affecting the fingerprint recognition effect. Summary of the Invention

[0005] This application provides a fingerprint recognition circuit, a display panel, and a display device, which can solve the technical problem in the prior art where light signal saturation affects the fingerprint recognition effect under strong light conditions.

[0006] In a first aspect, embodiments of this application provide a fingerprint recognition circuit, the circuit comprising:

[0007] A photodiode, in which a first capacitor is formed between the anode and cathode;

[0008] The first signal reset module is connected to the cathode of the photodiode and is used to provide a first signal voltage to the cathode of the photodiode.

[0009] The signal output module is connected to the cathode of the photodiode and is used to generate the corresponding fingerprint recognition voltage based on the cathode voltage of the photodiode.

[0010] An adaptive adjustment module is used to increase the equivalent capacitance between the anode and cathode of the photodiode when the light signal is enhanced.

[0011] In some embodiments, the signal output module includes a first transistor and a second transistor;

[0012] The first terminal of the first transistor is connected to the read signal line, the second terminal of the first transistor is connected to the first terminal of the second transistor, the second terminal of the second transistor is connected to the first signal line, the gate of the first transistor is connected to the read control signal line, the gate of the second transistor is connected to the cathode of the photodiode, and the anode of the photodiode is connected to the bias signal line.

[0013] In some embodiments, the first signal reset module includes:

[0014] The third transistor has its first terminal connected to the first signal line, its second terminal connected to the cathode of the photodiode, and its gate connected to the reset signal line.

[0015] In some embodiments, the adaptive adjustment module includes:

[0016] Second capacitor;

[0017] The second signal reset module is connected to the second capacitor and is used to provide the second signal voltage to the second capacitor.

[0018] A switching module, connected between the second capacitor and the photodiode, is used to connect the second capacitor and the photodiode in parallel;

[0019] In some embodiments, the capacitance of the second capacitor is greater than the capacitance of the first capacitor.

[0020] In some embodiments, the second signal reset module includes:

[0021] The fifth transistor has its first terminal connected to the second signal line, its second terminal connected to the first terminal of the second capacitor, and its gate connected to the reset signal line.

[0022] In some embodiments, the first signal line and the second signal line are the same signal line.

[0023] In some embodiments, the switch module includes:

[0024] The fourth transistor has its first terminal connected to the cathode of the photodiode, its second terminal connected to the first terminal of the second capacitor, its gate connected to the first terminal of the second capacitor, and its second terminal connected to the anode of the photodiode.

[0025] In some embodiments, the switch module includes:

[0026] The cathode of the first diode is connected to the cathode of the photodiode, and the anode of the first diode is connected to the first terminal of the second capacitor.

[0027] In some embodiments, the fingerprint recognition circuit includes at least two adaptive adjustment modules, each of which is connected in parallel with each other. Each adaptive adjustment module is used for different light signal intensities, and a second capacitor corresponding to the light signal intensity is connected in parallel with a photodiode.

[0028] In some embodiments, the fingerprint recognition circuit includes at least two adaptive adjustment modules, each of which is connected in series with a photodiode. Each adaptive adjustment module is used for different light signal intensities, and a second capacitor corresponding to the light signal intensity is connected in parallel with the photodiode. In any two adaptive adjustment modules, the light signal intensity corresponding to the adaptive adjustment module closer to the photodiode is less than or equal to the light signal intensity corresponding to the adaptive adjustment module farther from the photodiode.

[0029] Secondly, embodiments of this application provide a display panel, the display panel comprising:

[0030] Multiple fingerprint recognition circuits arranged in an array; the fingerprint recognition circuit is the fingerprint recognition circuit of the first aspect;

[0031] Multiple read signal lines are connected to the fingerprint recognition circuit in the same column to receive the fingerprint recognition voltage.

[0032] In some embodiments, the display panel further includes:

[0033] Multiple read control signal lines, each connected to the fingerprint recognition circuit in the same row, are used to drive the signal output module of the fingerprint recognition circuit to turn on;

[0034] Multiple reset signal lines, each connected to the fingerprint recognition circuit in the same row, are used to drive the first signal reset module of the fingerprint recognition circuit to turn on;

[0035] A single fingerprint recognition cycle includes three stages in sequence: the first stage, the second stage, and the third stage. In the first stage, multiple reset signal lines output reset signals line by line. In the third stage, multiple read control signal lines output read control signals line by line.

[0036] This application provides a display device, including a display panel in the second aspect.

[0037] Compared with existing technologies, the fingerprint recognition circuit, display panel, and display device provided in this application, by setting an adaptive adjustment module, can adjust the equivalent capacitance between the anode and cathode of the photodiode (PD) according to the intensity of the light signal. Under normal lighting conditions, the intensity variation range of the light signal received by the photodiode is within the linear region of the reverse current. The reflected light intensity of fingerprint valleys and ridges will cause a significant difference in the reverse current. At this time, the fingerprint recognition voltage can effectively identify fingerprint valley and ridge information. When the light signal is enhanced, the equivalent capacitance between the anode and cathode of the photodiode increases, and the linear region of the reverse current also increases. At this time, the operating range of the reverse current changes from the saturation region back to the linear region, allowing the fingerprint recognition voltage to clearly characterize the difference in fingerprint valley and ridge information. This improves the effectiveness of fingerprint information acquisition in strong light environments and ensures fingerprint recognition performance. Attached Figure Description

[0038] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of the module structure of a fingerprint recognition circuit provided in one embodiment of this application;

[0040] Figure 2 This is a schematic diagram of a fingerprint recognition circuit provided in one embodiment of this application when it is disposed under the screen;

[0041] Figure 3 This is a schematic diagram of a fingerprint recognition circuit provided in an embodiment of this application when it is disposed inside the screen;

[0042] Figure 4 This is a schematic diagram of the circuit structure of a fingerprint recognition circuit provided in an embodiment of this application;

[0043] Figure 5 This is a schematic diagram of the circuit structure of a fingerprint recognition circuit provided in another embodiment of this application;

[0044] Figure 6 This is a schematic diagram of the circuit structure of a fingerprint recognition circuit provided in another embodiment of this application;

[0045] Figure 7 This is a schematic diagram of the circuit structure of a fingerprint recognition circuit provided in another embodiment of this application;

[0046] Figure 8 This is a schematic diagram of the circuit structure of a fingerprint recognition circuit provided in another embodiment of this application;

[0047] Figure 9 This is a schematic diagram of the circuit structure of a fingerprint recognition circuit provided in another embodiment of this application;

[0048] Figure 10 This is a schematic diagram of the circuit structure of a fingerprint recognition circuit provided in another embodiment of this application;

[0049] Figure 11 This is a schematic diagram of the structure of a display panel provided in one embodiment of this application;

[0050] Figure 12 This is a signal timing diagram of a fingerprint recognition circuit provided in an embodiment of this application;

[0051] Figure 13 This is a schematic diagram of the structure of a display device provided in an embodiment of this application.

[0052] In the attached image:

[0053] 10. Fingerprint recognition circuit; PD, photodiode; 20. First signal reset module; 30. Signal output module; 40. Adaptive adjustment module; 41. Second signal reset module; 42. Switch module; T1, first transistor; T2, second transistor; T3, third transistor; T4, fourth transistor; T5, fifth transistor; C1, first capacitor; C2, second capacitor; D1, first diode; VDD, first signal line; Vbias, bias signal line; Vlg, second signal line; SEL, read control signal line; Data, read signal line; RST, reset signal line. Detailed Implementation

[0054] The features and exemplary embodiments of various aspects of this application will be described in detail below. To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain this application and not to limit it. For those skilled in the art, this application can be implemented without some of these specific details. The following description of the embodiments is merely to provide a better understanding of this application by illustrating examples of this application.

[0055] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes said element.

[0056] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The embodiments will now be described in detail with reference to the accompanying drawings.

[0057] Currently, as smart terminals continue to develop, fingerprint recognition technology is also constantly innovating. Compared to facial recognition, under-display fingerprint recognition has multiple advantages, including high maturity, adaptability to user habits, and lower cost.

[0058] Based on the development trend of under-display fingerprint technology, the technology path is shifting and expanding towards larger areas, thinner designs, and greater integration. For example, the fingerprint recognition module is integrated inside the display panel screen.

[0059] However, the actual light signal is relatively weak when light enters the screen or under the screen, due to the influence of optical transmittance. To improve the quality of the light signal, methods such as changing the light sensor design and adjusting the filter structure are usually used to increase transmittance, thereby enhancing the light signal received by the fingerprint recognition module. However, in strong light environments, device signal saturation can easily occur, affecting the fingerprint recognition effect.

[0060] To address the aforementioned technical problems, embodiments of this application provide a fingerprint recognition circuit, a display panel, and a display device. The fingerprint recognition circuit provided in this application embodiment will be described first.

[0061] Figure 1 A schematic diagram of the structure of a fingerprint recognition circuit 10 provided in one embodiment of this application is shown. The fingerprint recognition circuit 10 includes a photodiode PD, a first signal reset module 20, a signal output module 30, and an adaptive adjustment module 40.

[0062] A first capacitor C1 can be formed between the anode and cathode of a photodiode PD. This first capacitor C1 can be the equivalent capacitance of the photodiode PD itself, or it can be the equivalent capacitance formed by superimposing a capacitor connected in parallel with the photodiode PD.

[0063] The first signal reset module 20 is connected to the cathode of the photodiode PD. The first signal reset module 20 can provide a first signal voltage to the cathode of the photodiode PD so as to reset the cathode voltage to the first signal voltage before the photodiode PD receives the light signal.

[0064] The signal output module 30 is connected to the cathode of the photodiode PD. After the photodiode PD receives the light signal, the signal output module 30 can generate a corresponding fingerprint recognition voltage based on the cathode voltage of the photodiode PD.

[0065] It should be noted that before receiving a light signal, the cathode voltage of the photodiode PD is reset to the first signal voltage. At this time, the cathode voltage is higher than the anode voltage, and the photodiode PD is in a reverse cutoff state, allowing only a very weak reverse current to pass through. When the photodiode PD does not receive a light signal, this reverse current is a dark current.

[0066] The adaptive adjustment module 40 increases the equivalent capacitance between the anode and cathode of the photodiode PD when the light signal intensity increases. That is, when the light signal intensity is low, the adaptive adjustment module 40 does not operate, and the equivalent capacitance between the anode and cathode of the photodiode PD is small; when the light signal intensity increases, the adaptive adjustment module 40 can increase the equivalent capacitance between the anode and cathode of the photodiode PD. Under the same light signal intensity, when the equivalent capacitance between the anode and cathode of the photodiode PD increases, the linear range of the reverse current will increase. In other words, by increasing the equivalent capacitance between the anode and cathode of the photodiode PD, the response of the reverse current to the light signal intensity under strong light conditions can return to the linear range, increasing the difference in fingerprint ridges and valleys under strong light conditions, improving the clarity of fingerprint ridge and valley information, and realizing fingerprint acquisition and recognition under strong light conditions.

[0067] Correspondingly, when the light signal intensity decreases, the adaptive adjustment module 40 can reduce the equivalent capacitance between the anode and cathode of the photodiode PD, at which point the fingerprint recognition circuit 10 can return to the normal light environment to collect fingerprint information.

[0068] Figure 2 This diagram shows a fingerprint recognition circuit 10 installed under the screen. Figure 3 A schematic diagram is shown when the fingerprint recognition circuit 10 is installed inside the screen. Figure 2As shown, when the fingerprint recognition circuit 10 is located under the screen, the light signal reflected by the finger needs to pass through the layer containing the light-emitting element and the pixel circuit. This can be achieved by setting a collimating light path or an infrared cutoff filter (IRcut) path. The collimating light path can focus and collimate the light signal, while the infrared cutoff filter can prevent strong light from passing through. The infrared cutoff filter can be achieved through processes such as film application or coating. Figure 3 As shown, when the fingerprint recognition circuit 10 is located under the screen, the photodiode PD of the fingerprint recognition circuit 10 can be arranged on the same layer as the light-emitting element, while other components of the fingerprint recognition circuit 10 can be arranged on the same layer as the pixel circuit. At this time, the collimation light path and the infrared cut-off filter light path can be arranged between the photodiode PD and the cover plate.

[0069] When a user's finger covers the display area, the finger reflects the light from the image, allowing the photodiode PD in the fingerprint recognition circuit 10 (located inside or under the screen) to receive the reflected light signal. At this time, the reverse current flowing through the photodiode PD rapidly increases, changing from dark current to light current. Under the influence of the reverse current, the cathode voltage of the photodiode PD gradually decreases, and the decrease in cathode voltage is positively correlated with the received light signal. After the photodiode PD receives the light signal, the signal output module 30 generates a corresponding fingerprint recognition voltage based on the reduced cathode voltage of the photodiode PD and transmits it to the signal recognition module via the signal traces inside or under the screen. The signal recognition module then determines the fingerprint ridge information at the location of the fingerprint recognition circuit 10 based on the fingerprint recognition voltage. The signal recognition module then realizes the fingerprint recognition function based on the fingerprint recognition voltages corresponding to the multiple fingerprint recognition circuits 10 located on the screen.

[0070] Because the fingerprint recognition circuit 10 needs to be configured to have good light signal response capability under normal lighting conditions, the photodiode PD is usually designed so that the magnitude of the reverse current changes linearly with the intensity of the light signal under normal lighting conditions. That is, the change in the reverse current of the photodiode PD under normal lighting conditions is within the linear region. However, under strong light conditions, such as summer, midday, high sunlight intensity, or high ambient light intensity, the response of the reverse current of the photodiode PD to the light signal intensity is not within the linear region, but rather in the saturation region. When the photodiode PD is in a saturated state, even if the light signal intensity changes, the reverse current of the photodiode PD will not change significantly or the change will be small. At this time, the difference in the ridge and valley of the fingerprint, that is, the difference between the reverse current at the fingerprint valley position and the reverse current at the fingerprint ridge position, is small, resulting in unclear fingerprint valley and ridge information and insufficient contrast, thus failing to collect a valid fingerprint.

[0071] like Figure 1 As shown, the adaptive adjustment module 40 may include a second capacitor C2. The adaptive adjustment module 40 can connect the second capacitor C2 in parallel with the photodiode PD when the light signal intensity reaches a threshold. When the second capacitor C2 is disconnected from the photodiode PD, the equivalent capacitance between the anode and cathode of the photodiode PD is the first capacitor C1. When the second capacitor C2 is connected in parallel with the photodiode PD, the equivalent capacitance between the anode and cathode of the photodiode PD will increase. Under the same light signal intensity, when the equivalent capacitance between the anode and cathode of the photodiode PD increases, the linear region of the reverse current will increase. That is, by connecting the second capacitor C2 in parallel with the photodiode PD, the response of the reverse current to the light signal intensity under strong light conditions can return to the linear region, increasing the difference in fingerprint ridges and valleys under strong light conditions, improving the clarity of fingerprint ridge and valley information, and realizing fingerprint acquisition and recognition under strong light conditions.

[0072] Correspondingly, when the light signal intensity decreases, the adaptive adjustment module 40 can disconnect the second capacitor C2 from the photodiode PD, at which point the fingerprint recognition circuit 10 can return to the normal light environment to collect fingerprint information.

[0073] In this embodiment, by setting an adaptive adjustment module 40, the equivalent capacitance between the anode and cathode of the photodiode PD can be adjusted according to the intensity of the light signal. Under normal lighting conditions, the intensity variation range of the light signal received by the photodiode PD is within the linear region of the reverse current. The reflected light intensity of fingerprint valleys and ridges will cause a significant difference in the reverse current. At this time, the fingerprint recognition voltage can effectively identify the fingerprint valley and ridge information. When the light signal is enhanced, the equivalent capacitance between the anode and cathode of the photodiode PD increases, and the linear region of the reverse current also increases. At this time, the working range of the reverse current changes from the saturation region back to the linear region, so that the fingerprint recognition voltage can clearly characterize the difference in fingerprint valley and ridge information, thereby improving the effectiveness of fingerprint information acquisition in strong light environments and ensuring fingerprint recognition performance.

[0074] When the fingerprint recognition circuit 10 in the above embodiments and the fingerprint circuits of related technologies were subjected to light illumination tests, the fingerprint circuits of the related technologies entered a saturation state when the photocurrent of the photodiode PD reached 8pA, and the photocurrent did not change significantly when the light intensity further increased. However, the fingerprint recognition circuit in the above embodiments entered a saturation state when the photocurrent of the photodiode PD reached 60pA. Compared with the related technologies, the fingerprint recognition circuit 10 in the above embodiments can achieve fingerprint signal acquisition in a much stronger light environment.

[0075] Please refer to Figure 4In some embodiments, the signal output module 30 described above may include a first transistor T1 and a second transistor T2.

[0076] The first terminal of the first transistor T1 is connected to the read signal line Data. The second terminal of the first transistor T1 is connected to the first terminal of the second transistor T2. The second terminal of the second transistor T2 is connected to the first signal line VDD. The gate of the first transistor T1 is connected to the read control signal line SEL. The gate of the second transistor T2 is connected to the cathode of the photodiode PD. The anode of the photodiode PD is connected to the bias signal line Vbias.

[0077] The anode of the photodiode PD can receive the bias signal provided by the bias signal line Vbias, and the cathode voltage of the photodiode PD is reset to the first signal voltage by the first signal reset module 20. The first signal voltage is higher than the bias signal voltage, and the photodiode PD is in the reverse cutoff state.

[0078] After the photodiode PD receives the light signal reflected from the finger, it generates a corresponding reverse current, and the cathode voltage of the photodiode PD decreases from the first signal voltage. Since the gate voltage of the second transistor T2 is the same as the cathode voltage of the photodiode PD, as the gate voltage of the second transistor T2 gradually decreases from the first signal voltage, the conduction amplitude of the second transistor T2 also changes continuously. The first electrode of the second transistor T2 receives the first signal voltage, and as the conduction amplitude of the second transistor T2 changes, the fingerprint recognition voltage output from the second electrode of the second transistor T2 also changes accordingly. The read control signal line SEL provides a read control signal after the photodiode PD receives the light signal reflected from the finger. The first transistor T1 conducts under the read control signal. When the first transistor T1 is on, the first electrode of the second transistor T2 can output a fingerprint recognition voltage to the read signal line Data through the first transistor T1. This fingerprint recognition voltage is related to the first signal voltage and the conduction amplitude of the second transistor T2. The signal recognition module can determine the intensity of the light signal received by the fingerprint recognition circuit 10 based on the magnitude of the first signal voltage and the magnitude of the received fingerprint recognition voltage, and thus determine the fingerprint ridge information.

[0079] It should be noted that the first transistor T1 can be configured to be in saturation conduction when the read control signal line SEL is received, while the second transistor T2 can be configured such that the variation range of the cathode voltage of the photodiode PD is within the linear region of the gate voltage of the second transistor T2. That is, when the cathode voltage of the photodiode PD changes due to the first signal voltage, the conduction amplitude of the second transistor T2 also changes accordingly.

[0080] Please continue to refer to Figure 4In some embodiments, the first signal reset module 20 described above may include a third transistor T3.

[0081] The first terminal of the third transistor T3 is connected to the first signal line VDD, the second terminal of the third transistor T3 is connected to the cathode of the photodiode PD, and the gate of the third transistor T3 is connected to the reset signal line RST.

[0082] Before the photodiode PD receives the light signal reflected from the finger, the reset signal line RST can provide a reset signal. The third transistor T3 is turned on under the reset signal, resetting the cathode voltage of the photodiode PD to the first signal voltage.

[0083] Understandably, when the third transistor T3 is off, the reverse current generated by the photodiode PD receiving the light signal reflected from the finger will pull down the cathode voltage of the photodiode PD. Therefore, before acquiring the fingerprint signal voltage each time, the third transistor T3 needs to be turned on to boost the cathode voltage of the photodiode PD to the first signal voltage.

[0084] Please refer to Figure 5 In some embodiments, the adaptive adjustment module 40 may include a second capacitor C2, a second signal reset module 41, and a switch module 42.

[0085] The second signal reset module 41 can be connected to the second capacitor C2 and provide a second signal voltage to the second capacitor C2. The switch module 42 can be connected between the second capacitor C2 and the photodiode PD. When the switch module 42 is off, the second capacitor C2 is disconnected from the photodiode PD; when the switch module 42 is on, the second capacitor C2 and the photodiode PD are connected in parallel.

[0086] Understandably, in order to prevent the voltage at the end of the second capacitor C2 connected to the cathode of the photodiode PD from affecting the cathode voltage of the photodiode PD when the switch module 42 is turned on, the second signal reset module 41 can provide a second signal voltage to the second capacitor C2 to reset the second capacitor C2.

[0087] As an optional implementation, the second signal voltage can be set slightly lower than the first signal voltage to avoid the second signal voltage being too large when the second capacitor C2 is connected in parallel with the photodiode PD, which would cause the cathode voltage of the photodiode PD to increase instead of decrease.

[0088] In some embodiments, the capacitance value of the second capacitor C2 can be set to be greater than the capacitance value of the first capacitor C1.

[0089] Under normal lighting conditions, the second capacitor C2 is not connected in parallel with the photodiode PD. The equivalent capacitance between the anode and cathode of the photodiode PD is the first capacitor C1. Under the first capacitor C1, the reverse current varies within the linear region and increases with the increase of the light signal intensity.

[0090] In strong light conditions, the second capacitor C2 is connected in parallel with the photodiode PD. The equivalent capacitance between the anode and cathode of the photodiode PD is necessarily greater than that of the first capacitor C1, meaning the equivalent capacitance is inevitably increased. At this point, when the light signal intensity is slightly higher than in normal light conditions, the reverse current remains within the linear region. However, the light signal intensity in strong light conditions is typically much greater than in normal light conditions. Even with a small increase in the equivalent capacitance after connecting the second capacitor C2 in parallel with the photodiode PD, the reverse current may still enter the saturation region when the light signal intensity is high. This prevents the signal recognition module from distinguishing fingerprint ridges and valleys based on the fingerprint recognition voltage. Therefore, to significantly increase the range of light signal intensity variation corresponding to the linear region of the reverse current after connecting the second capacitor C2 in parallel with the photodiode PD, the second capacitor C2 should be at least greater than the first capacitor C1.

[0091] Please refer to Figure 6 In some embodiments, the second signal reset module 41 may include a fifth transistor T5, the first terminal of the fifth transistor T5 is connected to the second signal line Vlg, the second terminal of the fifth transistor T5 is connected to the first terminal of the second capacitor C2, and the gate of the fifth transistor T5 is connected to the reset signal line RST.

[0092] The fifth transistor T5 can be turned on when the reset signal line RST provides a reset signal, and reset the voltage at the first terminal of the second capacitor C2 to the second signal voltage.

[0093] It should be noted that the gates of both the third transistor T3 and the fifth transistor T5 are connected to the reset signal line RST. The two transistors can be connected to the same reset signal line RST, or they can be connected to different reset signal lines RST. Connecting both transistors to the same reset signal line RST, compared to connecting them to different reset signal lines RST, saves on the number of signal traces within the display panel, optimizes layout design space, and reduces the difficulty of technical solution verification.

[0094] Please refer to Figure 7 In some embodiments, the first signal line VDD and the second signal line Vlg may be the same signal line.

[0095] When the first signal line VDD and the second signal line Vlg are the same signal line, the first terminal of the fifth transistor T5 is connected to the first signal line VDD. That is, the voltage at the first terminal of the second capacitor C2 after reset can be consistent with the voltage at the cathode of the photodiode PD after reset.

[0096] In this embodiment, the second capacitor C2 is reset directly through the first signal line VDD, without adding extra signal traces, which can save the number of signal traces and reduce the difficulty of modifying and designing the display panel.

[0097] Please continue to refer to Figure 6 In some embodiments, the switching module 42 described above may include a fourth transistor T4.

[0098] The first terminal of the fourth transistor T4 is connected to the cathode of the photodiode PD, the second terminal of the fourth transistor T4 is connected to the first terminal of the second capacitor C2, the gate of the fourth transistor T4 is connected to the first terminal of the second capacitor C2, and the second terminal of the second capacitor C2 is connected to the anode of the photodiode PD.

[0099] The second terminal and gate of the fourth transistor T4 are connected, meaning that the gate voltage of the fourth transistor T4 is the same as the voltage of the second terminal. After the second signal reset module 41 resets the second capacitor C2, the voltage at the first terminal of the second capacitor C2 is the second signal voltage, and therefore the gate voltage of the fourth transistor T4 is also the second signal voltage.

[0100] In strong light conditions, the photodiode PD receives a high intensity light signal, resulting in a high reverse current. This causes the cathode voltage of the photodiode PD to drop rapidly. The first-terminal voltage of the fourth transistor T4 is the cathode voltage of the photodiode PD. When the voltage difference between the first-terminal voltage and the gate voltage of the fourth transistor T4 meets the conduction threshold, the fourth transistor T4 changes from the off state to the on state, connecting the second capacitor C2 in parallel with the photodiode PD. In other words, in strong light conditions, when the light signal intensity reaches the signal threshold, it pulls down the cathode voltage of the photodiode PD, causing the fourth transistor T4 to conduct and connecting the second capacitor C2 in parallel with the photodiode PD.

[0101] Please refer to Figure 8 In some embodiments, the switch module 42 may include a first diode D1. The cathode of the first diode D1 is connected to the cathode of the photodiode PD, the anode of the first diode D1 is connected to the first terminal of the second capacitor C2, and the second terminal of the second capacitor C2 is connected to the anode of the photodiode PD.

[0102] In addition to setting the switch module 42 as the fourth transistor T4 in the above embodiment, the switch module 42 can also be set as the first diode D1. After both the second capacitor C2 and the photodiode PD are reset, the anode voltage of the first diode D1 is lower than or equal to the cathode voltage, at which point the first diode D1 is in the off state. When the light signal intensity reaches the signal threshold, it can pull down the cathode voltage of the photodiode PD, so that the difference between the anode voltage and the cathode voltage of the first diode D1 reaches the conduction threshold. When the first diode D1 is turned on, it can connect the second capacitor C2 in parallel with the photodiode PD.

[0103] The switching module 42 can be selected from transistors or diodes, which increases the options for design and process solutions and improves feasibility.

[0104] In some embodiments, the fingerprint recognition circuit 10 described above may include at least two adaptive adjustment modules 40. Each adaptive adjustment module 40 may connect a second capacitor C2 in parallel with a photodiode PD when the light signal intensity reaches different signal thresholds.

[0105] In one optional implementation, taking the fingerprint recognition circuit 10 as an example, the two adaptive adjustment modules 40 are connected in parallel with each other and in parallel with the two ends of the photodiode PD. The conduction thresholds of the two fourth transistors T4 corresponding to the two adaptive adjustment modules 40 are different.

[0106] like Figure 9 As shown, in the two adaptive adjustment modules 40, one adaptive adjustment module 40 includes a second capacitor C2, a fourth transistor T4 and a fifth transistor T5, and the other adaptive adjustment module 40 includes a second capacitor C2', a fourth transistor T4' and a fifth transistor T5'.

[0107] The first terminal of the fourth transistor T4 is connected to the cathode of the photodiode PD, the second terminal of the fourth transistor T4 is connected to the first terminal of the second capacitor C2, the gate of the fourth transistor T4 is connected to the first terminal of the second capacitor C2, and the second terminal of the second capacitor C2 is connected to the anode of the photodiode PD. The first terminal of the fifth transistor T5 is connected to the signal line Vmg, the second terminal of the fifth transistor T5 is connected to the first terminal of the second capacitor C2, and the gate of the fifth transistor T5 is connected to the reset signal line RST.

[0108] The first terminal of the fourth transistor T4' is connected to the cathode of the photodiode PD, the second terminal of the fourth transistor T4' is connected to the first terminal of the second capacitor C2', the gate of the fourth transistor T4' is connected to the first terminal of the second capacitor C2', and the second terminal of the second capacitor C2' is connected to the anode of the photodiode PD. The first terminal of the fifth transistor T5' is connected to the second signal line Vlg, the second terminal of the fifth transistor T5' is connected to the first terminal of the second capacitor C2', and the gate of the fifth transistor T5' is connected to the reset signal line RST.

[0109] The fourth transistors T4 and T4' corresponding to the two adaptive adjustment modules 40 have different turn-on thresholds. When the light intensity reaches a certain signal threshold, the cathode voltage of the photodiode PD is pulled down, causing the gate-source voltage difference of one of the fourth transistors T4 to reach the turn-on threshold. At this time, the fourth transistor T4 turns on, connecting the second capacitor C2 of the corresponding adaptive adjustment module 40 in parallel with the photodiode PD.

[0110] As the light intensity continues to increase and reaches another signal threshold, the cathode voltage of the photodiode PD continues to decrease, causing the gate-source voltage difference of another fourth transistor T4' to reach the conduction threshold. At this time, the second capacitor C2' of another adaptive adjustment module 40 is connected in parallel with the photodiode PD.

[0111] In the above embodiments, the capacitance values ​​of the two second capacitors C2 corresponding to the two adaptive adjustment modules 40 can be the same or different. The fifth transistor T5 of the two adaptive adjustment modules 40 can be connected to the same second signal line Vlg, or they can be connected to two different signal lines Vlg and Vmg respectively.

[0112] In another optional implementation, the two adaptive adjustment modules 40 can also be connected in series and then connected to the two ends of the photodiode PD. That is, the fourth transistors T4 of the two adaptive adjustment modules 40 are connected in series and then connected to the cathode of the photodiode PD, and the conduction thresholds of the two fourth transistors T4 corresponding to the two adaptive adjustment modules 40 are different.

[0113] like Figure 10 As shown, in the two adaptive adjustment modules 40, one adaptive adjustment module 40 includes a second capacitor C2, a fourth transistor T4 and a fifth transistor T5, and the other adaptive adjustment module 40 includes a second capacitor C2', a fourth transistor T4' and a fifth transistor T5'.

[0114] The first terminal of the fourth transistor T4 is connected to the cathode of the photodiode PD, the second terminal of the fourth transistor T4 is connected to the first terminal of the second capacitor C2, the gate of the fourth transistor T4 is connected to the first terminal of the second capacitor C2, and the second terminal of the second capacitor C2 is connected to the anode of the photodiode PD. The first terminal of the fifth transistor T5 is connected to the signal line Vmg, the second terminal of the fifth transistor T5 is connected to the first terminal of the second capacitor C2, and the gate of the fifth transistor T5 is connected to the reset signal line RST.

[0115] The first terminal of the fourth transistor T4' is connected to the second terminal of the fourth transistor T4', the second terminal of the fourth transistor T4' is connected to the first terminal of the second capacitor C2', the gate of the fourth transistor T4' is connected to the first terminal of the second capacitor C2', and the second terminal of the second capacitor C2' is connected to the anode of the photodiode PD. The first terminal of the fifth transistor T5' is connected to the second signal line Vlg, the second terminal of the fifth transistor T5' is connected to the first terminal of the second capacitor C2', and the gate of the fifth transistor T5' is connected to the reset signal line RST.

[0116] When the fourth transistor T4, which is close to the photodiode PD, is turned on, the corresponding adaptive adjustment module 40 connects the second capacitor C2 in parallel with the photodiode PD. At this time, the other adaptive adjustment module 40 is not working.

[0117] As the light intensity further increases and the cathode voltage of the photodiode PD further decreases, the fourth transistor T4', located away from the photodiode PD, is turned on. At this time, both adaptive adjustment modules 40 are in operation. That is, among the two adaptive adjustment modules 40, the light signal intensity corresponding to the adaptive adjustment module 40 closer to the photodiode PD is lower than that corresponding to the adaptive adjustment module 40 farther from the photodiode PD. As the light signal intensity increases, the adaptive adjustment module 40 closer to the photodiode PD first connects the second capacitor C2 in parallel with the photodiode PD; as the light signal intensity continues to increase, the adaptive adjustment module 40 farther from the photodiode PD connects the second capacitor C2 in parallel with the photodiode PD.

[0118] In an optional implementation, the light signal intensities corresponding to the two adaptive adjustment modules 40 can also remain consistent.

[0119] Understandable, Figure 9 In the illustrated embodiment, both adaptive adjustment modules 40 can be individually connected in parallel with the photodiode PD. Figure 10 In the illustrated embodiment, one of the adaptive adjustment modules 40 can be connected in parallel with the photodiode PD independently, while the other adaptive adjustment module 40 can only be connected in parallel with the photodiode PD when the fourth transistor T4 of the first adaptive adjustment module 40 is turned on.

[0120] This application embodiment also provides a display panel. Figure 11 A schematic diagram of a display panel according to an embodiment of this application is shown. The display panel includes a plurality of fingerprint recognition circuits 10 arranged in an array, which may be the fingerprint recognition circuit 10 in the above embodiment.

[0121] The display panel may also include multiple read signal lines Data, each read signal line Data is connected to the fingerprint recognition circuit 10 in the same column. When the signal output module 30 of the fingerprint recognition circuit 10 outputs the fingerprint recognition voltage, the read signal line Data can transmit the fingerprint recognition voltage to the fingerprint recognition module. For example, the fingerprint recognition module may be a fingerprint chip or other module that can generate fingerprint valley and ridge information based on the fingerprint recognition voltage.

[0122] In some embodiments, the display panel may further include multiple read control signal lines SEL and multiple reset signal lines RST.

[0123] Each read signal line Data can be connected to the fingerprint recognition circuit 10 in the same row. The read signal line Data can drive the signal output module 30 of the fingerprint recognition circuit 10 to conduct by outputting a read signal.

[0124] Each reset signal line RST is connected to the fingerprint recognition circuit 10 in the same row. The reset signal line RST can drive the first signal reset module 20 of the fingerprint recognition circuit 10 to turn on by outputting a reset signal.

[0125] like Figure 12 As shown, a single fingerprint recognition cycle on the display panel can sequentially include a first stage t1, a second stage t2, and a third stage t3.

[0126] The first stage, t1, is the reset stage. During this stage, each reset signal line RST outputs a reset signal row by row. Each row of fingerprint recognition circuits 10 can activate the first signal reset module 20 upon receiving a valid reset signal, resetting the cathode voltage of the photodiode PD. After multiple reset signal lines RST output reset signals row by row from the first row to the last row, the entire array of fingerprint recognition circuits 10 completes the reset process.

[0127] The second stage t2 is the exposure stage. During the exposure stage, both the reset signal line RST and the read control signal line SEL output invalid signals. At this time, the photodiodes PD in each fingerprint recognition circuit 10 in the display panel can receive the light signal reflected by the user's finger when the user's finger covers the display area. The reverse current generated by the photodiode PD under the light signal can pull down the cathode voltage.

[0128] The third stage t3 is the reading stage. During the reading stage, each reading signal line Data can output reading signals line by line. The fingerprint recognition circuit 10 of each line can turn on the signal output module 30 when it receives a valid reading signal. The signal output module 30 can output the corresponding fingerprint recognition voltage to the reading signal line Data according to the pulled-down cathode voltage.

[0129] After the signal lines of each row output the reading signal in sequence, the fingerprint recognition module can receive the fingerprint recognition voltage provided by each fingerprint driving circuit, and recognize the user's fingerprint information according to the fingerprint recognition voltage to complete a single full-screen fingerprint recognition.

[0130] In one optional implementation, during the single full-screen fingerprint recognition process described above, the effective signal period of a single reset signal can be set to the microsecond level, the effective signal period of a single read control signal can be set to the 10 microsecond level, and the period of the exposure stage can be set to the millisecond level.

[0131] This application also provides a display device; please refer to [link to relevant documentation]. Figure 13 The display device can be a PC, television, monitor, mobile terminal, tablet computer, or wearable device, etc., and the display device can include the display panel provided in the embodiments of this application.

[0132] The functional blocks shown in the above-described structural diagram can be implemented as hardware, software, firmware, or a combination thereof. When implemented in hardware, they can be, for example, electronic circuits, application-specific integrated circuits (ASICs), appropriate firmware, plug-ins, function cards, etc. When implemented in software, the elements of this application are programs or code segments used to perform the required tasks. Programs or code segments can be stored on a machine-readable medium or transmitted over a transmission medium or communication link via data signals carried on a carrier wave. "Machine-readable medium" can include any medium capable of storing or transmitting information. Examples of machine-readable media include electronic circuits, semiconductor memory devices, ROM, flash memory, erasable ROM (EROM), floppy disks, CD-ROMs, optical disks, hard disks, fiber optic media, radio frequency (RF) links, etc. Code segments can be downloaded via computer networks such as the Internet, intranets, etc.

[0133] It should be noted that, in this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0134] This document uses specific examples to illustrate the principles and implementation methods of this application. The examples are merely for the purpose of helping to understand the method and core ideas of this application. The above are only preferred embodiments of this application. It should be noted that due to the limitations of written expression, and the existence of an infinite number of specific structures, those skilled in the art can make several improvements, modifications, or changes without departing from the principles of this application, and can also combine the above technical features in an appropriate manner. These improvements, modifications, changes, or combinations, or the direct application of the concept and technical solution of this application to other situations without modification, should all be considered within the scope of protection of this application.

Claims

1. A fingerprint recognition circuit, characterized in that, The circuit includes: A photodiode, wherein a first capacitor is formed between the anode and cathode of the photodiode; The first signal reset module is connected to the cathode of the photodiode and is used to provide a first signal voltage to the cathode of the photodiode. A signal output module is connected to the cathode of the photodiode and is used to generate a corresponding fingerprint recognition voltage based on the cathode voltage of the photodiode. An adaptive adjustment module is used to increase the equivalent capacitance between the anode and cathode of the photodiode when the light signal is enhanced; The adaptive adjustment module includes: Second capacitor; The second signal reset module is connected to the second capacitor and is used to provide a second signal voltage to the second capacitor; A switching module is connected between the second capacitor and the photodiode, and is used to connect the second capacitor and the photodiode in parallel.

2. The fingerprint recognition circuit according to claim 1, characterized in that, The signal output module includes a first transistor and a second transistor; The first terminal of the first transistor is connected to the read signal line, the second terminal of the first transistor is connected to the first terminal of the second transistor, the second terminal of the second transistor is connected to the first signal line, the gate of the first transistor is connected to the read control signal line, the gate of the second transistor is connected to the cathode of the photodiode, and the anode of the photodiode is connected to the bias signal line.

3. The fingerprint recognition circuit according to claim 2, characterized in that, The first signal reset module includes: The third transistor has its first terminal connected to the first signal line, its second terminal connected to the cathode of the photodiode, and its gate connected to the reset signal line.

4. The fingerprint recognition circuit according to any one of claims 1-3, characterized in that, The capacitance of the second capacitor is greater than that of the first capacitor.

5. The fingerprint recognition circuit according to claim 1, characterized in that, The second signal reset module includes: The fifth transistor has its first terminal connected to the second signal line, its second terminal connected to the first terminal of the second capacitor, and its gate connected to the reset signal line.

6. The fingerprint recognition circuit according to claim 5, characterized in that, The first signal line and the second signal line connected to the signal output module are the same signal line.

7. The fingerprint recognition circuit according to claim 1, characterized in that, The switching module includes: The fourth transistor has its first terminal connected to the cathode of the photodiode, its second terminal connected to the first terminal of the second capacitor, its gate connected to the first terminal of the second capacitor, and its second terminal connected to the anode of the photodiode.

8. The fingerprint recognition circuit according to claim 7, characterized in that, The switching module also includes: The first diode has its cathode connected to the cathode of the photodiode, and its anode connected to the first terminal of the second capacitor.

9. The fingerprint recognition circuit according to claim 1, characterized in that, The fingerprint recognition circuit includes at least two adaptive adjustment modules, each of which is connected in parallel. Each adaptive adjustment module is used for different light signal intensities, and the second capacitor corresponding to the light signal intensity is connected in parallel with the photodiode.

10. The fingerprint recognition circuit according to claim 1, characterized in that, The fingerprint recognition circuit includes at least two adaptive adjustment modules, each of which is connected in series with the photodiode. Each adaptive adjustment module is used for different light signal intensities, and the second capacitor corresponding to the light signal intensity is connected in parallel with the photodiode. Among any two adaptive adjustment modules, the light signal intensity corresponding to the adaptive adjustment module closer to the photodiode is less than or equal to the light signal intensity corresponding to the adaptive adjustment module farther from the photodiode.

11. A display panel, characterized in that, The display panel includes: Multiple fingerprint recognition circuits arranged in an array; the fingerprint recognition circuits are as described in any one of claims 1-10; Multiple read signal lines are connected to the fingerprint recognition circuit in the same column to receive the fingerprint recognition voltage.

12. The display panel according to claim 11, characterized in that, The display panel also includes: Multiple read control signal lines are provided, each of which is connected to the fingerprint recognition circuit in the same row to drive the signal output module of the fingerprint recognition circuit to turn on. Multiple reset signal lines, each reset signal line is connected to the fingerprint recognition circuit in the same row, and is used to drive the first signal reset module of the fingerprint recognition circuit to turn on; A single fingerprint recognition cycle includes a first stage, a second stage, and a third stage in sequence; in the first stage, multiple reset signal lines output reset signals line by line; in the third stage, multiple read control signal lines output read control signals line by line.

13. A display device, characterized in that, The display panel included in any one of claims 11-12.

Images