Fingerprint recognition circuit and driving method thereof, fingerprint recognition unit, and sensor

Abstract

The present application provides a fingerprint recognition circuit and its driving method, a fingerprint recognition unit, and a sensor. The fingerprint recognition circuit includes a first end of a first switch module electrically connected to a first signal end, and a second end electrically connected to a first node; a first end of a driving module electrically connected to a first end of a third switch module, a second end electrically connected to a second signal end, and a control end electrically connected to a first node; a first end of a storage module electrically connected to a first node, a second end electrically connected to a second node, and the second node is used to be electrically connected to a sensing module; a first end of a second switch module electrically connected to a second node, and a second end electrically connected to a second signal end; and a second end of a third switch module electrically connected to a signal detection device. The present application collects the threshold voltage of the driving module during the initialization phase and loads it to the first node in advance, so that the driving module subsequently outputs a current whose magnitude is independent of the threshold voltage, which can effectively eliminate the influence of threshold voltage drift on fingerprint image acquisition.

Description

Technical Field

[0001] The present application relates to the field of fingerprint recognition technology. Specifically, the present application relates to a fingerprint recognition circuit and a driving method thereof, a fingerprint recognition unit, and a sensor. Background Art

[0002] Currently, three effective fingerprint recognition technologies exist: capacitive detection, photoelectric detection, and ultrasonic detection. Ultrasonic fingerprint recognition offers strong penetration, enabling liveness detection and low-cost, large-area fingerprint recognition. It is also unaffected by environmental factors such as water droplets and dust particles, resulting in greater stability. Ultrasonic fingerprint recognition uses an ultrasonic sensor to detect the electrical signal generated by the energy difference in the echoes, thereby obtaining fingerprint spine information and enabling fingerprint detection.

[0003] Existing fingerprint recognition solutions do not consider the impact of transistor threshold voltage drift in the sensor on the grayscale image acquisition of the fingerprint, resulting in poor accuracy of the grayscale image of the acquired fingerprint. Summary of the Invention

[0004] In response to the shortcomings of existing methods, this application proposes a fingerprint recognition circuit and its driving method, a fingerprint recognition unit, and a sensor to solve the technical problem that the existing technology does not consider the impact of transistor threshold voltage drift in the sensor on the grayscale image acquisition of the fingerprint, resulting in poor accuracy of the grayscale image of the acquired fingerprint.

[0005] In a first aspect, an embodiment of the present application provides a fingerprint recognition circuit, comprising: a first switch module, a second switch module, a third switch module, a drive module, and a storage module;

[0006] The first end of the first switch module is electrically connected to the first signal end, and the second end is electrically connected to the first node;

[0007] The first end of the driving module is electrically connected to the first end of the third switch module, the second end is electrically connected to the second signal end, and the control end is electrically connected to the first node;

[0008] The first end of the storage module is electrically connected to the first node, the second end is electrically connected to the second node, and the second node is used to be electrically connected to the sensing module;

[0009] The first end of the second switch module is electrically connected to the second node, and the second end is electrically connected to the second signal end;

[0010] The second end of the third switch module is used to be electrically connected to the signal detection device;

[0011] In a second aspect, an embodiment of the present application provides a fingerprint recognition unit, comprising a sensor module and the fingerprint recognition circuit of the first aspect;

[0012] The sensing module is electrically connected to the second node of the fingerprint recognition circuit.

[0013] In a third aspect, an embodiment of the present application provides a sensor comprising a fingerprint recognition unit as in the second aspect.

[0014] In a fourth aspect, an embodiment of the present application provides a driving method for a fingerprint recognition circuit, which is applied to the fingerprint recognition circuit of the first aspect, comprising:

[0015] In the initialization phase, the first switch module, the second switch module, and the third switch module are all turned on, increasing the voltage loaded from the first signal terminal to the first node until the voltage of the first node is the sum of the first voltage of the second signal terminal and the threshold voltage of the driving module;

[0016] During the signal acquisition phase, the driving module is turned on, and the storage module raises the voltage of the first node in a bootstrap manner, so that the voltage of the first node includes the second voltage collected by the sensing module and the threshold voltage, and the second voltage carries the biological information of the object; so that the driving module outputs a first current signal whose size is independent of the threshold voltage.

[0017] The beneficial technical effects brought about by the technical solutions provided in the embodiments of the present application include:

[0018] (1) The fingerprint recognition circuit provided by the embodiment of the present application, by setting a first switch module, a second switch module, a third switch module, a driver module and a storage module, collects the threshold voltage of the driver module and the first voltage of the second signal terminal in the initialization stage, and loads them to the first node (i.e., the control terminal of the driver module) in advance (in the initialization stage or the reset stage of the previous signal detection cycle in the periodic signal detection). In the signal acquisition stage, the driver module is turned on, and the pre-loaded threshold voltage can offset the threshold voltage of the driver module, so that the driver module outputs a first current signal whose size is independent of the threshold voltage. The present application can actively compensate for the threshold voltage, effectively eliminate the influence of the threshold voltage drift on the image acquisition of the fingerprint, thereby improving the accuracy and anti-interference of the grayscale image of the acquired fingerprint, and thus completing high-quality image acquisition. At the same time, it can also improve the efficiency of fingerprint acquisition and recognition efficiency, obtain a more efficient response, and has high practical value.

[0019] (2) The fingerprint recognition circuit provided in the embodiment of the present application can also directly obtain the threshold voltage information of the transistor and realize the monitoring of the threshold voltage of the transistor, which has high practical value and excellent applicability.

[0020] Additional aspects and advantages of the present application will be given in part in the following description, which will become apparent from the following description, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0022] Figure 1 A circuit diagram of a fingerprint recognition unit provided in an embodiment of the present application;

[0023] Figure 2 A circuit schematic diagram of a fingerprint recognition unit in the oscillation startup phase provided by an embodiment of the present application;

[0024] Figure 3 A circuit diagram of a fingerprint recognition unit in the receiving stage provided in an embodiment of the present application;

[0025] Figure 4 A circuit schematic diagram of a fingerprint recognition unit in the reset phase provided by an embodiment of the present application;

[0026] Figure 5 A timing diagram of a driving method of a fingerprint recognition circuit provided in an embodiment of the present application;

[0027] Figure 6 A timing diagram of another driving method of a fingerprint recognition circuit provided in an embodiment of the present application;

[0028] Figure 7 A timing diagram of a driving method for another fingerprint recognition circuit provided in an embodiment of the present application;

[0029] Figure 8 A schematic diagram of the structure of a sensor provided in an embodiment of the present application.

[0030] Reference numerals:

[0031] 10- fingerprint recognition unit, 11- first switch module, 12- second switch module, 13- third switch module, 14- driving module, 15- storage module, 16- sensor module;

[0032] 20-Signal detection device;

[0033] VDD-first signal terminal; VBIAS-second signal terminal;

[0034] N1-first node, N2-second node. DETAILED DESCRIPTION

[0035] The present application is described in detail below. Examples of embodiments of the present application are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar components or components having the same or similar functions. In addition, if the detailed description of the known technology is not necessary for the features of the present application shown, it will be omitted. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application and are not to be construed as limiting the present application.

[0036] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with their meanings in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless specifically defined as herein.

[0037] It will be understood by those skilled in the art that, unless expressly stated otherwise, the singular forms "a", "an", "said" and "the" used herein may also include the plural forms. It should be further understood that the term "comprising" used in the specification of the present application refers to the presence of the features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof. It should be understood that when we refer to an element as being "connected" or "coupled" to another element, it may be directly connected or coupled to the other element, or there may be intermediate elements. In addition, "connected" or "coupled" as used herein may include wireless connections or wireless couplings. The term "and / or" used herein includes all or any units and all combinations of one or more associated listed items.

[0038] The following describes in detail the technical solution of the present application and how the technical solution of the present application solves the above-mentioned technical problems with specific embodiments.

[0039] The present application embodiment provides a fingerprint recognition circuit, such as Figure 1 As shown, the fingerprint recognition circuit includes: a first switch module 11, a second switch module 12, a third switch module 13, a driving module 14 and a storage module 15;

[0040] The first switch module 11 has a first terminal electrically connected to the first signal terminal VDD, a second terminal electrically connected to the first node N1, and a control terminal for receiving a first switch signal;

[0041] The first end of the driving module 14 is electrically connected to the first end of the third switch module 13, the second end is electrically connected to the second signal end, and the control end is electrically connected to the first node N1;

[0042] The first end of the storage module 15 is electrically connected to the first node N1, and the second end is electrically connected to the second node N2. The second node N2 is used to be electrically connected to the sensor module 16.

[0043] The first end of the second switch module 12 is electrically connected to the second node N2, the second end is electrically connected to the second signal terminal VBIAS, and the control end is used to receive the second switch signal;

[0044] The second end of the third switch module 13 is used to be electrically connected to the signal detection device 20 , and the control end is used to receive the third switch module 13 .

[0045] Optionally, in the initialization stage, the first switch module 11, the second switch module 12 and the third switch module 13 are all turned on, that is, the first switch module 11 is turned on based on the first switch signal, the second switch module 12 is turned on based on the second switch signal, and the third switch module 13 is turned on based on the third switch signal, and the voltage loaded from the first signal end to the first node N1 is increased until the voltage of the first node N1 is the sum of the first voltage of the second signal end and the threshold voltage of the driving module 14.

[0046] During the signal acquisition phase, the driving module 14 is turned on, and the storage module 15 raises the voltage of the first node N1 in a bootstrap manner, so that the voltage of the first node N1 includes the second voltage acquired by the sensing module 16 and the threshold voltage, and the second voltage carries the biological information of the object; so that the driving module 14 outputs a first current signal whose size is independent of the threshold voltage.

[0047] The fingerprint recognition circuit provided in the embodiment of the present application is provided with a first switch module 11, a second switch module 12, a third switch module 13, a driver module 14, and a storage module 15. During the initialization phase, the threshold voltage of the driver module and the first voltage of the second signal terminal are acquired and loaded in advance (during the initialization phase or the reset phase of each signal detection cycle in periodic signal detection) to the first node (i.e., the control terminal of the driver module). During the signal acquisition phase, the driver module 14 is turned on, and the pre-loaded threshold voltage can offset the threshold voltage of the driver module, so that the driver module outputs a first current signal whose magnitude is independent of the threshold voltage. The present application can actively compensate for the threshold voltage, effectively eliminating the impact of threshold voltage drift on the grayscale image acquisition of the fingerprint, thereby improving the accuracy and anti-interference performance of the grayscale image of the acquired fingerprint, thereby completing high-quality image acquisition, and at the same time improving the efficiency of fingerprint acquisition and recognition, obtaining a more efficient response, and having high practical value.

[0048] In some embodiments, the voltage of the first signal terminal is an adjustable voltage.

[0049] Optionally, in the initialization stage, the first switch module 11, the second switch module 12 and the third switch module 13 are all turned on, the voltage of the first signal end gradually increases and is loaded to the first node N1, so that the voltage of the first node gradually increases. When the voltage of the first node N1 increases to the sum of the first voltage of the second signal end and the threshold voltage, the driving module 14 is turned on and outputs an initial current signal to the signal detection device 20.

[0050] The signal detection device 20 of the embodiment of the present application can directly obtain the threshold voltage information of the transistor based on the received initial current signal, thereby realizing the monitoring of the transistor threshold voltage, and has high practical value and excellent applicability.

[0051] Optionally, the signal acquisition phase includes periodic signal detection, where each signal detection cycle includes:

[0052] In the first phase, the first switch module 11 is off, and the second and third switch modules 12 and 13 are both on. The sensor module 16 transmits a signal based on the received pulse signal Tx. At this point, the voltage at the second signal terminal VBIAS is the first voltage. The voltage at the first node N1 is the sum of the first voltage obtained during the initialization phase or the previous signal detection cycle and the threshold voltage of the driver module.

[0053] In the second stage, the first switch module 11 and the second switch module 12 are both closed, and the third switch module 13 is turned on. The storage module 15 raises the voltage of the first node N1 in a bootstrap manner (raising the second voltage collected by the sensor module 16 in total) to a value such that the voltage of the first node N1 reaches the sum of the second voltage collected by the sensor module 16, the threshold voltage and the first voltage (that is, the voltage of the first node N1 at this time includes the second voltage collected by the sensor module 16, the threshold voltage of the driving module and the first voltage of the second signal end). The second voltage is generated by the sensor module 16 based on the echo signal reflected by the object; the driving module 14 outputs a first current signal to the signal detection device 20 based on the voltage of the first node, so that the magnitude of the first current signal is independent of the threshold voltage.

[0054] In the third stage, the first switch module 11 and the second switch module 12 are both turned on, and the third switch module 13 is turned off, so that the voltage of the first node is reset to the sum of the first voltage and the threshold voltage.

[0055] Optionally, the second signal terminal VBIAS is a bias voltage signal terminal, and the first voltage is a bias voltage.

[0056] In some embodiments, as Figure 1 As shown, including at least one of the following:

[0057] The first switch module 11 includes a first transistor T1 , a first electrode of the first transistor T1 is electrically connected to the first signal terminal VDD, a second electrode of the first transistor T1 is electrically connected to the first node N1 , and a control electrode is used to receive a first switching signal.

[0058] The driving module 14 includes a second transistor T2 , a first electrode of the second transistor T2 being electrically connected to the first end of the third switch module 13 , a second electrode being electrically connected to the second signal end VBIAS, and a control electrode being electrically connected to the first node N1 .

[0059] The storage module 15 includes a capacitor C. A first end of the capacitor C is electrically connected to the first node N1 , and a second end of the capacitor C is electrically connected to the second node N2 .

[0060] The second switch module 12 includes a third transistor T3 , a first electrode of the third transistor T3 is electrically connected to the second node N2 , a second electrode is electrically connected to the second signal terminal VBIAS, and a control electrode is used to receive a second switching signal.

[0061] The third switch module 13 includes a fourth transistor T4 , a first electrode of the fourth transistor T4 is electrically connected to the first end of the driving module 14 , a second electrode is electrically connected to the signal detection device 20 , and a control electrode is used to receive a third switching signal.

[0062] In this embodiment, the transistors can be independently selected from one of a polysilicon thin film transistor, an amorphous silicon thin film transistor, an oxide thin film transistor, and an organic thin film transistor. Among them, the "control electrode" specifically refers to the gate of the transistor, the "first electrode" specifically refers to the drain of the transistor, and the "second electrode" specifically refers to the source of the transistor. Of course, those skilled in the art should know that for the switch module, the "first electrode" and the "second electrode" can be interchanged, that is, the "first electrode" specifically refers to the source of the transistor, and the "second electrode" specifically refers to the drain of the transistor.

[0063] Optionally, each of the above transistors may be an N-type transistor or a P-type transistor, as those skilled in the art will appreciate. Figure 1 The circuit connection method shown is only an example of the fingerprint recognition circuit provided in the embodiment of the present application. When the type of each transistor changes, the electrical connection method of each component in the fingerprint recognition circuit provided in the embodiment of the present application can be adaptively adjusted. The adaptively adjusted electrical connection method still falls within the protection scope of the embodiment of the present application.

[0064] Optionally, the sensor module 16 may include an ultrasonic transceiver module, or a photoelectric module, etc., which is not particularly limited in this application.

[0065] Optionally, the ultrasonic transceiver module may be made of ultrasonic piezoelectric material. Different materials may be used for different application areas. The optoelectronic module may include a photodiode.

[0066] like Figure 1 As shown, the description is made by taking as an example that all transistors are N-type transistors and the sensor module 16 is an ultrasonic transceiver module Rx.

[0067] It should be noted that the ultrasonic transceiver module uses ultrasonic piezoelectric materials, which can realize the transmission and reception of ultrasonic waves. It has been used in existing ultrasonic solutions and has excellent transceiver effects.

[0068] The working characteristics of ultrasonic piezoelectric materials are that they can vibrate and emit ultrasonic waves under the action of pulse voltage signals. After the ultrasonic waves penetrate the glass cover and are emitted through the fingerprint spine, the ultrasonic piezoelectric materials can also realize the function of receiving ultrasonic waves. During the process of receiving ultrasonic waves, the voltage of the second node N2 changes, and the fingerprint spine information carried by the ultrasonic waves can be converted into a voltage signal (such as Figure 1 The magnitude of the Vp voltage can reflect the fingerprint spine information.

[0069] See also Figure 1 Specifically, the drain D of the first transistor T1 is electrically connected to the first signal terminal VDD, the source S is electrically connected to the first node N1, and the control terminal GATE is used to receive the first switching signal, which turns on when the signal is high and turns off when the signal is low. The voltage of the first signal terminal VDD is an adjustable voltage.

[0070] The drain D of the second transistor T2 is electrically connected to the drain D of the fourth transistor T4 , the source S is electrically connected to the second signal terminal VBIAS, and the control electrode GATE is electrically connected to the first node N1 .

[0071] The first end of the capacitor C is electrically connected to the first node N1, and the second end is electrically connected to the second node N2.

[0072] The drain D of the third transistor T3 is electrically connected to the second node N2 , the source S is electrically connected to the second signal terminal VBIAS, and the control electrode GATE is used to receive the second switching signal, which is turned on at a high level and turned off at a low level.

[0073] The drain D of the fourth transistor T4 is electrically connected to the drain D of the second transistor T2 , the source S is electrically connected to the signal detection device 20 , and the control electrode GATE is used to receive the third switching signal, which is turned on when high and turned off when low.

[0074] A first end of the sensor module 16 is electrically connected to the second node, and a second end thereof is used to receive the pulse signal Tx.

[0075] In some embodiments, at least one of the first transistor, the second transistor, the third transistor, and the fourth transistor is a low temperature polysilicon (LTPS) thin film transistor (TFT).

[0076] Optionally, each transistor is a low temperature polysilicon (LTPS) thin film transistor (TFT).

[0077] The transistors of the embodiments of the present application use low-temperature polysilicon (LTPS) thin-film transistors (TFTs), which can improve switching efficiency, have high mobility, and fast response speed, and can be efficiently and widely used in the field of fingerprint recognition.

[0078] Based on the same inventive concept, an embodiment of the present application provides a fingerprint recognition unit 10, which includes a sensor module 16 and a fingerprint recognition circuit provided by any of the above embodiments;

[0079] The sensor module 16 is electrically connected to the second node of the fingerprint recognition circuit.

[0080] In some embodiments, the sensor module 16 includes an ultrasonic transceiver module, or a photoelectric module.

[0081] Optionally, the ultrasonic transceiver module may be made of ultrasonic piezoelectric material. Different materials may be used for different application areas. The optoelectronic module may include a photodiode.

[0082] Based on the same inventive concept, an embodiment of the present application provides a sensor, which includes a fingerprint recognition unit 10 provided in any of the above embodiments.

[0083] In some embodiments, a signal detection device 20 is further included, and the signal detection device 20 is electrically connected to the fingerprint recognition unit 10.

[0084] In some embodiments, as Figure 8 As shown, the number of fingerprint recognition units 10 is at least two.

[0085] At least two fingerprint recognition units 10 are distributed in an array and are electrically connected to the signal detection device 20 .

[0086] Optionally, the sensor further includes a power supply unit and a control unit.

[0087] The power supply unit is electrically connected to the first signal terminal VDD, and is used to provide an adjustable voltage to the first signal terminal VDD.

[0088] Specifically, the power supply unit applies a voltage to the first node N1 through the first signal terminal VDD. In the initialization phase, the voltage of the first node N1 starts to rise from zero potential.

[0089] The control unit is electrically connected to the control end of the first switch module 11, the control end of the second switch module 12, and the control end of the third switch module 13, and is used to send a first switching signal to the first switch module 11, a second switching signal to the second switch module 12, and a third switching signal to the third switch module 13.

[0090] Optionally, the power supply unit and the control unit may be independent units respectively, or may be integrated into the signal detection device 20 , which is not particularly limited in this application.

[0091] Based on the same inventive concept, an embodiment of the present application provides a driving method for a fingerprint recognition circuit, which is applied to the fingerprint recognition circuit provided in any of the above embodiments. The driving method for the fingerprint recognition circuit includes:

[0092] In the initialization stage, the first switch module 11 , the second switch module 12 and the third switch module 13 are all turned on, increasing the voltage loaded from the first signal terminal to the first node until the voltage of the first node is the sum of the first voltage of the second signal terminal and the threshold voltage of the driving module 14 .

[0093] During the signal acquisition phase, the driving module 14 is turned on, and the storage module 15 raises the voltage of the first node in a bootstrap manner, so that the voltage of the first node includes the second voltage acquired by the sensing module 16 and the threshold voltage, and the second voltage carries the biological information of the object; so that the driving module 14 outputs a first current signal whose magnitude is independent of the threshold voltage.

[0094] The driving method of the fingerprint recognition circuit provided in the embodiment of the present application, during the initialization phase, acquires the threshold voltage of the driver module and the first voltage of the second signal terminal and pre-loads them to the first node (i.e., the control terminal of the driver module) (during the initialization phase or the reset phase of the previous signal detection cycle in periodic signal detection). During the signal acquisition phase, the driver module 14 is turned on, and the pre-loaded threshold voltage can offset the threshold voltage of the driver module, so that the driver module outputs a first current signal whose magnitude is independent of the threshold voltage. The present application can actively compensate for the threshold voltage, effectively eliminating the impact of threshold voltage drift on fingerprint image acquisition, thereby improving the accuracy and anti-interference performance of the grayscale image of the acquired fingerprint, thereby completing high-quality image acquisition. It can also improve the efficiency of fingerprint acquisition and recognition, obtain a more efficient response, and has high practical value.

[0095] Optionally, the signal acquisition phase may perform a single signal detection or a periodic signal detection. A corresponding signal detection method may be selected according to actual conditions.

[0096] In some embodiments, during the initialization phase, the first switch module 11, the second switch module 12, and the third switch module 13 are all turned on, and the voltage applied from the first signal terminal to the first node is increased until the voltage of the first node is the sum of the first voltage of the second signal terminal and the threshold voltage of the driving module 14, including:

[0097] During the initialization phase, the first switch module 11, the second switch module 12, and the third switch module 13 are all turned on, the voltage at the first signal terminal gradually increases and is loaded onto the first node, causing the voltage at the first node to gradually increase. When the voltage at the first node increases to the sum of the first voltage at the second signal terminal and the threshold voltage, the driving module 14 is turned on and outputs an initial current signal to the signal detection device 20. The signal detection device then determines the threshold voltage based on the initial current signal and the bias voltage.

[0098] The signal detection device 20 of the embodiment of the present application can directly obtain the threshold voltage information of the transistor based on the received initial current signal, thereby realizing the monitoring of the transistor threshold voltage, and has high practical value and excellent applicability.

[0099] In some embodiments, during the signal acquisition phase, the driving module 14 is turned on, and the storage module 15 raises the voltage of the first node in a bootstrap manner, so that the voltage of the first node includes the second voltage acquired by the sensing module 16 and the threshold voltage, and the second voltage carries the biological information of the subject; and the driving module 14 outputs a first current signal that is unrelated to the threshold voltage, including:

[0100] The signal acquisition phase includes periodic signal detection. Each signal detection cycle includes:

[0101] In the first phase, the first switch module 11 is off, and the second and third switch modules 12 and 13 are both on. The sensor module 16 transmits a signal based on the received pulse signal. At this time, the voltage at the second signal terminal VBIAS is the first voltage. The voltage at the first node N1 is the sum of the first voltage obtained during the initialization phase or the previous signal detection cycle and the threshold voltage of the driver module.

[0102] In the second stage, the first switch module 11 and the second switch module 12 are both closed, and the third switch module 13 is turned on. The storage module 15 raises the voltage of the first node in a bootstrap manner (raising the second voltage collected by the sensor module 16 in total) to the sum of the second voltage collected by the sensor module 16, the threshold voltage and the first voltage (that is, the voltage of the first node N1 at this time includes the second voltage collected by the sensor module 16, the threshold voltage of the driving module and the first voltage of the second signal end). The second voltage is generated by the sensor module 16 based on the echo signal reflected by the object; the driving module 14 outputs a first current signal to the signal detection device 20 based on the voltage of the first node, so that the magnitude of the first current signal is independent of the threshold voltage.

[0103] In the third stage, the first switch module 11 and the second switch module 12 are both turned on, and the third switch module 13 is turned off, so that the voltage of the first node is reset to the sum of the first voltage and the threshold voltage.

[0104] Below is Figure 1 The circuit diagram of the fingerprint recognition unit 10 shown in FIG. Figure 5 The timing diagram of the driving method of the fingerprint recognition circuit shown in FIG. 1 is a timing diagram of the driving method of the fingerprint recognition circuit provided in the embodiment of the present application. The principle of the driving method of the fingerprint recognition circuit provided in the embodiment of the present application is described in detail as follows:

[0105] Specifically, the operation of the fingerprint recognition circuit of the present application can be divided into two stages: an initialization stage and a signal acquisition stage (e.g., a periodic signal detection stage). The initialization stage realizes the power-on and threshold voltage acquisition of the ultrasonic fingerprint acquisition system, and then enters the periodic signal detection stage to realize the periodic acquisition of array information of the fingerprint recognition unit 10.

[0106] like Figure 1 and Figure 6As shown, in the initialization phase P1, the first transistor T1, the third transistor T3, and the fourth transistor T4 are all turned on (conducted) with their gates at high potential based on the received switching signal, and the voltage of the first signal terminal VDD begins to rise from zero potential until the signal detection device 20 detects the initial current signal. At this time, the voltage value V(N1) of the voltage at the first node N1 is the sum of the threshold voltage Vth of the second transistor T2 and the first voltage VBIAS_1 of the second signal terminal VBIAS, that is, V(N1)=Vth+VBIAS_1. In other words, the voltage of the first signal terminal VDD gradually increases and is loaded to the first node N1, so that the voltage of the first node N1 gradually increases. When the voltage V(N1) of the first node N1 increases to the sum of the first voltage VBIAS_1 of the second signal terminal VBIAS and the threshold voltage Vth of the second transistor T2, the second transistor T2 is turned on and outputs the initial current signal to the signal detection device 20, and the signal detection device 20 detects the signal. The voltage value of the second node N2 is the first voltage VBIAS_1 of the second signal terminal VBIAS, and the voltage value across the capacitor C1 is the threshold voltage Vth.

[0107] After the initialization phase P1 is completed, the voltage value of the first signal terminal VDD is the value of V( N1 ), and the signal detection device 20 can obtain the threshold voltage information of T2 through data processing.

[0108] This application can directly obtain the threshold voltage information of the transistor and realize the monitoring of the threshold voltage of the transistor, which has high practical value and excellent applicability.

[0109] like Figure 2-4 and Figure 7 As shown, the periodic signal detection phase can include three phases. If the sensor module 16 is an ultrasonic transceiver module, the periodic signal detection phase can include an oscillation phase, a receiving phase, and a reset phase. If the sensor module 16 is a photoelectric module, the periodic signal detection phase can include an illumination phase, a receiving phase, and a reset phase. The ultrasonic transceiver module and the photoelectric module have the same principles during the initialization phase and signal acquisition phase. Figure 2-4 The dotted line in the figure indicates that the corresponding transistor is turned off.

[0110] Taking the sensor module 16 as an example, the signal acquisition phase includes periodic signal detection, and each signal detection cycle includes:

[0111] like Figure 2 and Figure 7As shown, in the first stage P2 (for example, the oscillation starting stage), the first transistor T1 is turned off, the third transistor T3 and the fourth transistor T4 are both turned on (conducted) at a high potential, the pulse signal Tx sends a signal, and the ultrasonic transceiver module Rx sends out an ultrasonic signal under the stimulation of the pulse signal Tx. In the first stage P2, the first voltage VBIAS_1 of the second signal terminal VBIAS provides voltage to the ultrasonic transceiver module Rx.

[0112] like Figure 3 and Figure 7 As shown, in the second stage P3 (e.g., the receiving stage), the first transistor T1 and the third transistor T3 are both turned off, and the fourth transistor T4 is turned on (conducting) at a high potential. After the ultrasonic signal is reflected by the fingerprint spine (i.e., the object), the received signal carrying the fingerprint information returns to the ultrasonic transceiver module Rx. After the ultrasonic transceiver module Rx receives the echo signal reflected by the fingerprint spine (i.e., the object), a second voltage Vp is generated, and the voltage value of the second node N2 increases. Different fingerprint information generates different second voltages Vp.

[0113] At this point, the voltage V(N2) at the second node N2 is the sum of the first voltage VBIAS_1 and the second voltage Vp of the second signal terminal VBIAS, i.e., V(N2) = VBIAS_1 + Vp. Due to the bootstrap effect of capacitor C, the voltage at the first node N1 also begins to rise, and the voltage V(N1) at the first node N1 is V(N1) = Vth + VBIAS_1 + Vp, where Vth is the threshold voltage of the second transistor. According to the saturation current formula, the first current signal I of the second transistor T2 is:

[0114] I=Kn(Vgs–Vth) 2 =Kn(VBIAS_1+Vp+Vth–VBIAS_1–Vth) 2

[0115] =Kn(Vp) 2

[0116] Wherein, Kn is a fixed constant, Vgs represents the gate-source voltage of the second transistor T2, and Vth is the threshold voltage of the second transistor.

[0117] From the above, it can be seen that the first current signal I is independent of the threshold voltage Vth of the second transistor, and the voltage signal corresponding to the first current signal I is also independent of the threshold voltage Vth of the second transistor. The signal detection device 20 receives the voltage signal corresponding to the first current signal. At this time, the voltage signal eliminates the influence of the threshold voltage of the second transistor T2 on the signal, thereby obtaining more accurate image information.

[0118] like Figure 4 and Figure 7As shown, in the third stage P4 (for example, the reset stage), the fourth transistor T4 is turned off, and the first transistor T1 and the third transistor T3 are turned on (conducted) at a high potential. At this time, the signal detection device 20 no longer receives the signal, the first transistor T1 is turned on, and the voltage value of the first node N1 is reset to the voltage value of the first signal terminal VDD after initialization is completed, that is, VBIAS_1+Vth, and the voltage value of the second node N2 is reset to the first voltage VBIAS_1.

[0119] After the reset phase is completed, the signal acquisition process is completed once. For the array-type fingerprint recognition unit 10, periodic signal detection can be performed to finally complete the fingerprint information acquisition.

[0120] By applying the embodiments of the present application, at least the following beneficial effects can be achieved:

[0121] (1) The fingerprint recognition circuit provided by the embodiment of the present application, by setting a first switch module, a second switch module, a third switch module, a driver module and a storage module, collects the threshold voltage of the driver module and the first voltage of the second signal terminal in the initialization stage, and loads them to the first node (i.e., the control terminal of the driver module) in advance (in the initialization stage or the reset stage of the previous signal detection cycle in the periodic signal detection). In the signal acquisition stage, the driver module is turned on, and the pre-loaded threshold voltage can offset the threshold voltage of the driver module, so that the driver module outputs a first current signal whose size is independent of the threshold voltage. The present application can actively compensate for the threshold voltage, effectively eliminate the influence of the threshold voltage drift on the grayscale image acquisition of the fingerprint, thereby improving the accuracy and anti-interference of the grayscale image of the acquired fingerprint, and thus completing high-quality image acquisition. At the same time, it can also improve the efficiency of fingerprint acquisition and recognition, obtain a more efficient response, and has high practical value.

[0122] (2) The fingerprint recognition circuit provided in the embodiment of the present application can also directly obtain the threshold voltage information of the transistor and realize the monitoring of the threshold voltage of the transistor, which has high practical value and excellent applicability.

[0123] Those skilled in the art will appreciate that the steps, measures, and schemes in the various operations, methods, and processes discussed in this application may be interchanged, modified, combined, or deleted. Furthermore, other steps, measures, and schemes in the various operations, methods, and processes discussed in this application may also be interchanged, modified, rearranged, decomposed, combined, or deleted. Furthermore, steps, measures, and schemes in the prior art that are similar to those disclosed in this application may also be interchanged, modified, rearranged, decomposed, combined, or deleted.

[0124] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of such features. Throughout this application, unless otherwise specified, "plurality" means two or more.

[0125] In the description of this specification, specific features, structures, materials or characteristics may be combined in an appropriate manner in any one or more embodiments or examples.

[0126] It should be understood that although the steps in the flowcharts of the accompanying drawings are shown in sequence as indicated by the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some of the steps in the flowcharts of the accompanying drawings may include multiple sub-steps or multiple stages, and these sub-steps or stages are not necessarily executed at the same time, but can be executed at different times, and their execution order is not necessarily sequential, but can be executed in turn or alternately with other steps or at least a portion of the sub-steps or stages of other steps.

[0127] The above description is only part of the implementation methods of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A fingerprint recognition circuit, characterized in that: include: a first switch module, a second switch module, a third switch module, a drive module, and a storage module; The first end of the first switch module is electrically connected to the first signal end, and the second end is electrically connected to the first node; The first end of the driving module is electrically connected to the first end of the third switch module, the second end is electrically connected to the second signal end, and the control end is electrically connected to the first node; The first end of the storage module is electrically connected to the first node, the second end is electrically connected to the second node, and the second node is used to be electrically connected to the sensing module; A first end of the second switch module is electrically connected to the second node, and a second end thereof is electrically connected to the second signal end; The second end of the third switch module is used to be electrically connected to the signal detection device; The first switch module, the second switch module, and the third switch module are all turned on in an initialization phase to increase the voltage applied from the first signal terminal to the first node until the voltage of the first node is the sum of the first voltage of the second signal terminal and the threshold voltage of the driving module; The driving module is used to be turned on during the signal acquisition phase, and the storage module is used to raise the voltage of the first node in a bootstrap manner during the signal acquisition phase, so that the voltage of the first node includes the second voltage collected by the sensing module and the threshold voltage, and the second voltage carries the biological information of the object; so that the driving module outputs a first current signal with a magnitude that is independent of the threshold voltage.

2. The fingerprint recognition circuit according to claim 1, characterized in that: The voltage of the first signal terminal is an adjustable voltage.

3. The fingerprint recognition circuit according to claim 1, characterized in that: Include at least one of the following: The first switch module includes a first transistor, wherein a first electrode of the first transistor is electrically connected to the first signal terminal, and a second electrode of the first transistor is electrically connected to the first node; The driving module includes a second transistor, wherein a first electrode of the second transistor is electrically connected to the first end of the third switch module, a second electrode is electrically connected to the second signal end, and a control electrode is electrically connected to the first node; The storage module includes a capacitor, a first end of the capacitor is electrically connected to the first node, and a second end of the capacitor is electrically connected to the second node; The second switch module includes a third transistor, a first electrode of the third transistor is electrically connected to the second node, and a second electrode of the third transistor is electrically connected to the second signal terminal; The third switch module includes a fourth transistor, a first electrode of the fourth transistor is electrically connected to the first end of the driving module, and a second electrode of the fourth transistor is electrically connected to the signal detection device.

4. The fingerprint recognition circuit according to claim 3, characterized in that: At least one of the first transistor, the second transistor, the third transistor, and the fourth transistor is a low-temperature polysilicon thin-film transistor.

5. A fingerprint recognition unit, characterized in that: comprising a sensor module and a fingerprint recognition circuit according to any one of claims 1 to 4; The sensing module is electrically connected to the second node of the fingerprint recognition circuit.

6. The fingerprint recognition unit according to claim 5, characterized in that: The sensing module includes an ultrasonic transceiver module.

7. A sensor, characterized in that: The fingerprint recognition unit comprises the fingerprint recognition unit as described in any one of claims 5-6.

8. The sensor according to claim 7, characterized in that It also includes a signal detection device electrically connected to the fingerprint recognition unit.

9. The sensor according to claim 8, characterized in that The number of the fingerprint recognition units is at least two; At least two fingerprint recognition units are distributed in an array and are electrically connected to the signal detection device.

10. A driving method for a fingerprint recognition circuit, characterized in that: The fingerprint recognition circuit according to any one of claims 1 to 4 is applied to the fingerprint recognition circuit, wherein the first switch module, the second switch module, and the third switch module are all turned on in an initialization phase to increase the voltage applied from the first signal terminal to the first node until the voltage of the first node is the sum of the first voltage of the second signal terminal and the threshold voltage of the driving module, comprising: The first switch module, the second switch module and the third switch module are all turned on, the voltage of the first signal end gradually increases and is loaded to the first node, so that the voltage of the first node gradually increases. When the voltage of the first node increases to the sum of the first voltage of the second signal end and the threshold voltage, the driving module is turned on and outputs an initial current signal to the signal detection device.

11. The driving method of the fingerprint recognition circuit according to claim 10, characterized in that: The driving module is configured to be turned on during a signal acquisition phase, and the storage module is configured to raise the voltage of the first node in a bootstrap manner during the signal acquisition phase, so that the voltage of the first node includes a second voltage acquired by the sensing module and the threshold voltage, wherein the second voltage carries biological information of the subject; The step of causing the driving module to output a first current signal whose magnitude is independent of the threshold voltage includes: The signal acquisition phase includes periodic signal detection. Each signal detection cycle includes: In the first stage, the first switch module is closed, and the second switch module and the third switch module are both turned on, and the sensor module transmits a signal based on the received pulse signal; In the second stage, the first switch module and the second switch module are both turned off, and the third switch module is turned on. The storage module bootstraps the voltage of the first node to the sum of a second voltage collected by the sensing module, the threshold voltage, and the first voltage. The second voltage is generated by the sensing module based on the echo signal reflected by the object. The driving module outputs a first current signal to the signal detection device based on the voltage of the first node, so that the magnitude of the first current signal is independent of the threshold voltage; In the third stage, the first switch module and the second switch module are both turned on, and the third switch module is turned off, so that the voltage of the first node is reset to the sum of the first voltage and the threshold voltage.

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