WO2021248561A1 - 光学指纹识别电路及显示面板 - Google Patents

光学指纹识别电路及显示面板 Download PDF

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Publication number
WO2021248561A1
WO2021248561A1 PCT/CN2020/097760 CN2020097760W WO2021248561A1 WO 2021248561 A1 WO2021248561 A1 WO 2021248561A1 CN 2020097760 W CN2020097760 W CN 2020097760W WO 2021248561 A1 WO2021248561 A1 WO 2021248561A1
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Prior art keywords
driving transistor
reset
gate
signal
voltage
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PCT/CN2020/097760
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English (en)
French (fr)
Inventor
田超
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武汉华星光电技术有限公司
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Application filed by 武汉华星光电技术有限公司 filed Critical 武汉华星光电技术有限公司
Priority to US16/965,367 priority Critical patent/US11838019B2/en
Priority to EP20870450.2A priority patent/EP4163818A4/en
Publication of WO2021248561A1 publication Critical patent/WO2021248561A1/zh

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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
    • G06V40/00—Recognition of biometric, human-related or animal-related patterns in image or video data
    • G06V40/10—Human or animal bodies, e.g. vehicle occupants or pedestrians; Body parts, e.g. hands
    • G06V40/12—Fingerprints or palmprints
    • G06V40/13—Sensors therefor
    • G06V40/1318—Sensors therefor using electro-optical elements or layers, e.g. electroluminescent sensing
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
    • H10K59/10—OLED displays
    • H10K59/12—Active-matrix OLED [AMOLED] displays

Definitions

  • This application relates to the field of fingerprint identification technology, and in particular to an optical fingerprint identification circuit and a display panel.
  • Fingerprints are invariable characteristics that are inherently unique and distinguishable from others.
  • the fingerprint pattern is unique. It is composed of a series of ridges and valleys on the surface of the fingertip skin.
  • the fingerprint recognition technology developed from it is an earlier technology used for personal identity verification.
  • Optical fingerprint recognition technology as a mature fingerprint recognition technology, has long been integrated into people's daily life, and fingerprint locks and fingerprint time attendance are not lacking.
  • Optical fingerprint recognition technology uses the principle of light refraction and reflection. When light is irradiated on a finger, it is received by a photosensitive sensor (sensor) after being reflected by the finger. The photosensitive sensor can convert the light signal into an electrical signal for reading.
  • the fingerprint valley and ridge reflect different light
  • the reflected light intensity of the valley and ridge received by the photosensitive sensor is different, and the magnitude of the converted current or voltage is also different, so special points in the fingerprint can be captured to provide uniqueness Confirmation information.
  • the optical system is relatively large, which limits the application of optical fingerprint recognition technology.
  • optical fingerprint systems can omit complex and bulky optical systems.
  • Low-temperature polysilicon Low Temperature Poly-Silicon, referred to as LTPS
  • LTPS Low Temperature Poly-Silicon
  • using the light of the OLED display screen to trigger the photosensitive sensor has low brightness, resulting in weak photo-generated current of the photosensitive sensor, which poses a challenge to signal collection and processing.
  • an active driving scheme is used for pixel signal output to achieve improved fingerprint recognition efficiency.
  • the existing active driving scheme generally requires a large number of thin film transistors (TFT), which is not conducive to in-plane integration; and the architecture with fewer TFTs requires higher characteristics of the photosensitive sensor, which increases the preparation requirements of the photosensitive sensor , Is not conducive to promotion.
  • TFT thin film transistors
  • the embodiments of the present application provide an optical fingerprint recognition circuit and a display panel, which can reduce the requirement on the reverse breakdown voltage of the photodiode while realizing the signal output to complete the fingerprint recognition, that is, the characteristic requirement on the photosensitive sensor.
  • An embodiment of the application provides an optical fingerprint recognition circuit, the circuit includes a driving transistor and a photodiode; the circuit further includes: a reset unit for responding to a reset signal to transmit a reset voltage, reset the The gate voltage of the driving transistor; the anode of the photodiode is connected to a gate scan line for receiving a scan signal, and the cathode is connected to the gate of the driving transistor, and the photodiode is used to respond to a first The scanning signal of the level enters the reverse bias state, and the exposure is performed under the light signal of the light intensity corresponding to the fingerprint valley or fingerprint ridge, and a corresponding photocurrent is generated to discharge the gate of the driving transistor, and pull down the driving transistor.
  • a reset unit for responding to a reset signal to transmit a reset voltage, reset the The gate voltage of the driving transistor
  • the anode of the photodiode is connected to a gate scan line for receiving a scan signal
  • the cathode is connected to the gate of the driving transistor
  • the gate voltage, the photodiode is further used to respond to a scan signal of a second level to enter a forward conduction state, wherein the second level is higher than the first level; a coupling capacitor is used to respond The scan signal of the second level is used to turn on the driving transistor; the driving transistor is used to output the light signal for fingerprint identification.
  • the embodiment of the present application also provides an optical fingerprint recognition circuit, the circuit includes a driving transistor and a photodiode; the circuit further includes: a reset unit for responding to a reset signal to transmit a reset voltage, reset all The gate voltage of the driving transistor; the photodiode is used to respond to a scan signal of a first level to enter a reverse bias state, generate a photocurrent according to a light signal and output to the gate of the driving transistor, and respond to a first The two-level scan signal enters the forward conduction state, wherein the second level is higher than the first level; a coupling capacitor is used to respond to a second-level scan signal to turn on the drive Transistor; The driving transistor is used to output the optical signal for fingerprint recognition.
  • the embodiment of the present application also provides a display panel, including an array substrate; the array substrate includes at least one optical fingerprint recognition circuit, the optical fingerprint recognition circuit includes a driving transistor and a photodiode; the optical fingerprint recognition circuit also It includes: a reset unit for transmitting a reset voltage in response to a reset signal and resetting the gate voltage of the driving transistor; the photodiode for entering a reverse bias state in response to a scanning signal of a first level, according to A light signal generates a photocurrent output to the gate of the driving transistor, and enters a forward conduction state in response to a scan signal of a second level, and wherein the second level is higher than the first level; A coupling capacitor is used to respond to the scan signal of the second level to turn on the driving transistor; the driving transistor is used to output the optical signal for fingerprint identification.
  • This application can effectively avoid the risk of photodiode reverse breakdown while realizing the output of optical signals to complete fingerprint recognition, and reduces the requirement for the reverse breakdown voltage of the photodiode, that is, the characteristic requirements for the photosensitive sensor are reduced, and the circuit
  • the structure is simple, and fewer TFTs are required, which facilitates in-plane integration.
  • FIG. 1 is a circuit diagram of an embodiment of an optical fingerprint identification circuit of this application
  • Figure 2 shows the volt-ampere characteristic curve of the photodiode
  • FIG. 3 is a driving timing diagram of the optical fingerprint identification circuit shown in FIG. 1;
  • Fig. 4 is a circuit diagram of a conventional optical fingerprint recognition circuit
  • FIG. 5 is a driving timing diagram of the optical fingerprint identification circuit shown in FIG. 4;
  • FIG. 6 is a schematic diagram of the structure of the display panel of this application.
  • connection and “connected” should be interpreted in a broad sense. For example, it may be electrical connection or mutual communication, it may be directly connected, or indirectly connected through an intermediate medium, it may be the internal communication between two components or the interaction relationship between two components. It should be understood that when an element is referred to as being “coupled to” another element, there are intervening elements. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.
  • This application proposes an optical fingerprint recognition circuit, which adds a reset unit to the gate of the driving transistor and at the same time connects the anode of the photodiode to the gate scan line; in the reset phase, the gate of the driving transistor is reset by the reset unit, In the exposure phase, the photodiode is in a reverse bias state, and exposure is carried out under different light intensities corresponding to the fingerprint valley/fingerprint ridge, discharges the gate of the driving transistor, and pulls down the gate voltage of the driving transistor; in the reading phase, pass The coupling capacitor voltage-couples the gate of the driving transistor, so that the driving transistor is turned on and the light signal is output.
  • the voltage at both ends of the photodiode rises at the same time without increasing the reverse bias voltage.
  • This application can effectively avoid the risk of photodiode reverse breakdown while realizing the output of optical signals to complete fingerprint recognition, and reduces the requirement for the reverse breakdown voltage of the photodiode, that is, the characteristic requirements for the photosensitive sensor are reduced, and the circuit
  • the structure is simple, and fewer TFTs are required, which facilitates in-plane integration.
  • Figure 1 is a circuit diagram of an embodiment of the optical fingerprint recognition circuit of this application.
  • Figure 2 is the volt-ampere characteristic curve of the photodiode.
  • the abscissa is the voltage value (unit V)
  • the ordinate is Is the current value (unit A)
  • FIG. 3 is a driving timing diagram of the optical fingerprint recognition circuit shown in FIG. 1.
  • the optical fingerprint recognition circuit includes a driving transistor T11, a photodiode D11, a reset unit 101, and a coupling capacitor C11.
  • the reset unit 101 is used for transmitting a reset voltage Vinit in response to a reset signal RST1 to reset the gate voltage of the driving transistor T11.
  • the photodiode D11 is used to respond to a scan signal Gn of a first level to enter a reverse bias state, generate a photocurrent according to a light signal and output it to the gate of the driving transistor T11.
  • the coupling capacitor C11 is used to respond to a scan signal Gn of a second level to turn on the driving transistor T11; the driving transistor T11 is used to output the optical signal for fingerprint recognition; the photodiode D11 further In response to the scan signal Gn of the second level, it enters a forward conduction state.
  • the photodiode D11 After the photodiode D11 enters the reverse-biased state, it is exposed under the light signal of the light intensity corresponding to the fingerprint valley or fingerprint ridge to generate a corresponding photocurrent to discharge the gate of the driving transistor T11, and pull down the The gate voltage of the driving transistor T11 is described.
  • the light signals of different light intensities have different capabilities to discharge the gate of the driving transistor T11, which in turn causes the gate voltage of the driving transistor T11 to fall differently, so that fingerprint recognition can be performed subsequently.
  • a photodiode is a semiconductor device composed of a PN junction, which has unidirectional conductivity and is a photoelectric sensor device that can convert optical signals into electrical signals.
  • the photodiode works under the action of reverse voltage. When there is no light, the reverse current is extremely weak, called dark current; when there is light, the reverse current rapidly increases to tens of microamps, called photocurrent. The greater the intensity of light, the greater the reverse current. The change of light causes the current of the photodiode to change, which can convert the light signal into an electrical signal.
  • the working area of the photodiode is divided into a forward working area 201, a reverse working area 202 and a reverse breakdown area 203.
  • the absolute value of the reverse bias voltage of the photodiode is greater than the highest absolute value of its allowable reverse working voltage, the photodiode will be reversed breakdown.
  • the photodiode changes from a reverse bias state to a forward conduction state; in order to ensure that the driving transistor T11 is effectively turned on, the gate voltage needs to be high enough, but Since the voltage across the photodiode D11 rises at the same time, the reverse bias voltage will not increase, the risk of reverse breakdown can be effectively avoided, and the requirement for the reverse breakdown voltage of the photodiode D11 is reduced, that is, the requirement for the photosensitive sensor is reduced.
  • the reset unit 101 includes: a reset transistor T12, the control terminal of which is connected to a reset scan line for receiving the reset signal RST1, and the first terminal of which is used for receiving the reset signal RST1.
  • the second end of the reset voltage Vinit is connected to the gate of the driving transistor T11.
  • the reset crystal T12 is turned on under the control of the reset signal RST1, and transmits the reset voltage Vinit to the gate of the driving transistor T11 for resetting. That is, in the reset phase, the gate voltage of the driving transistor T11 is equal to the reset voltage Vinit.
  • the reset voltage Vinit is less than the turn-on voltage of the driving transistor T11 to prevent the driving transistor T11 from being turned on during the reset phase.
  • the reset transistor T12 adopts a thin film transistor (TFT), for example, it may be a low temperature polysilicon thin film transistor (LTPS_TFT) prepared based on a low temperature polysilicon process.
  • TFT thin film transistor
  • the gate of the thin film transistor (TFT) serves as the control terminal of the reset transistor T12.
  • the anode of the photodiode D11 is connected to a gate scan line for receiving the scan signal Gn, and its cathode is connected to the gate of the driving transistor T11.
  • the photodiode D11 enters a reverse bias state when the scan signal Gn is at a first level, and enters a forward conduction state when the scan signal Gn is at a second level.
  • the second level is higher than the first level, for example, the second level is a high level, and the first level is a low level, so that the photodiode D11 realizes the reverse Bias/forward conduction.
  • the photodiode D11 is an organic light emitting diode (OLED).
  • the first pole of the coupling capacitor C11 and the anode of the photodiode D11 are connected to the same gate scan line for receiving the same scan signal Gn, and the second pole of the coupling capacitor C11 is connected to the driving transistor T11. ⁇ Grid.
  • the coupling capacitor C11 voltage-couples the gate voltage of the driving transistor T11 to increase the gate voltage to turn on the driving transistor.
  • the voltage coupling is performed through the coupling capacitor C11, so that the gate voltage of the driving transistor T11 is increased.
  • the driving transistor T11 is turned on , In order to complete the output of the optical signal.
  • the first terminal of the driving transistor T11 is used to receive a power supply voltage VDD, and the second terminal thereof is connected to a data read line RD (Readout).
  • the driving transistor T11 When the driving transistor T11 is turned on, it outputs the optical signal to the data reading line RD, and the related IC can obtain the optical signal through the data reading line RD for fingerprint identification.
  • the driving transistor T11 also adopts a thin film transistor (TFT), for example, it may be a low temperature polysilicon thin film transistor (LTPS_TFT) prepared based on a low temperature polysilicon process, thereby facilitating the implementation of the manufacturing process and facilitating in-plane integration.
  • TFT thin film transistor
  • LTPS_TFT low temperature polysilicon thin film transistor
  • Reset phase A11 The scan signal Gn is Low, the reset signal RST1 is High, the reset transistor T12 is turned on, and the reset voltage Vinit is input to the gate of the drive transistor T11 (indicated by Q1) Perform a reset; the voltage at point Q1 is equal to the reset voltage Vinit.
  • Exposure stage A12 the reset signal RST1 jumps to low level, the reset transistor T12 is turned off; the scanning signal Gn signal is still low, due to the higher voltage at point Q1, the photodiode D11 is in a reverse biased state; the photodiode D11 is at Exposure is performed under light signals of different light intensities corresponding to the fingerprint valley/fingerprint ridge; when the light is irradiated on the photodiode D11, the photodiode D11 generates a certain photocurrent; the photocurrent discharges the Q1 point, and the voltage at the Q1 point drops. The light intensity and the voltage drop are different.
  • Reading stage A13 the scanning signal Gn jumps to high level, and the voltage coupling to point Q1 is performed through the coupling capacitor C11, so that the voltage at point Q1 rises; when the voltage at point Q1 is greater than the turn-on voltage of the driving transistor T11, drive The transistor T11 is turned on, and the optical signal is output to the data reading line RD (RD1 in FIG. 3 indicates the optical signal read), and then output to the corresponding IC through the data reading line RD.
  • RD1 in FIG. 3 indicates the optical signal read
  • FIGS. 4 to 5 are circuit diagram of a conventional optical fingerprint recognition circuit
  • FIG. 5 is a driving timing diagram of the optical fingerprint recognition circuit shown in FIG. 4.
  • the anode of the photodiode D21 is connected to a reset signal line for receiving the reset signal PR1 to reset the driving transistor T21; its coupling capacitor C21 is connected to a gate scanning line for receiving scanning
  • the signal Gn is used to control the driving transistor T21 to turn on.
  • Reset phase A21 the scan signal Gn is low, the reset signal PR1 is high, the photodiode D21 is turned on, and the gate of the driving transistor T21 (represented by Q2) is reset.
  • Exposure stage A22 the reset signal PR1 jumps to a low level, and the photodiode D21 is in a reverse-biased state; the photodiode D21 is exposed to light signals of different light intensities corresponding to the fingerprint valley/fingerprint ridge to generate a certain photocurrent; The photocurrent discharges point Q2, and the voltage at point Q2 drops. Different light intensities have different voltage drops.
  • Reading stage A23 The scanning signal Gn jumps to high level, and the voltage coupling to point Q2 is performed through the coupling capacitor C21, so that the voltage at point Q2 rises; when the voltage at point Q2 is greater than the turn-on voltage of the driving transistor T21, drive The transistor T21 is turned on and outputs an optical signal to the data reading line RD (RD1 in FIG. 5 indicates the optical signal read.
  • the driving transistor T21 In order to ensure that the driving transistor T21 is effectively turned on, the voltage at point Q2 is required to be high enough, so that the reverse bias voltage of the photodiode D21 is high, and there is a risk of reverse breakdown. Therefore, the driving scheme requires the reverse breakdown voltage of the photodiode D21 to be sufficiently high In order to avoid breakdown, the preparation requirements for photosensitive sensors are relatively high.
  • the present application also provides a display panel.
  • FIG. 6 is a schematic diagram of the display panel structure of the present application.
  • the display panel 60 includes an array substrate 61, and the array substrate 61 includes at least one optical fingerprint recognition circuit 611.
  • the optical fingerprint identification circuit 611 adopts the optical fingerprint identification circuit described in FIG. 1 of this application.
  • the connection mode and working principle of the circuit components of the optical fingerprint identification circuit 611 have been described in detail above, and will not be repeated here.
  • the display panel adopting the optical fingerprint identification circuit of the present application can effectively avoid the risk of reverse breakdown of the photodiode while realizing the output of the optical signal to complete the fingerprint identification.
  • the preparation requirements of the photosensitive sensor, and the circuit structure is simple, the required TFT is less, which is conducive to in-plane integration.

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Abstract

本申请公开了一种光学指纹识别电路及显示面板。本申请电路通过增加用于响应复位信号以传送复位电压，进而复位驱动晶体管的栅极电压的复位单元，使得在驱动晶体管输出光信号以完成指纹识别时，光电二极管两端电压同时抬升，而不会增加反偏电压。本申请可以有效避免光电二极管反向击穿风险，且电路结构简单，利于面内集成。

Description

光学指纹识别电路及显示面板 技术领域
本申请涉及指纹识别技术领域，尤其涉及一种光学指纹识别电路及显示面板。
 背景技术
指纹是人体与生俱来独一无二并可与他人相区别的不变特征。指纹图案具有唯一性，它由指端皮肤表面上的一系列脊和谷组成，由之发展起来的指纹识别技术是较早被用作为个人身份验证的技术。光学指纹识别技术作为一种成熟的指纹识别技术早已融入人们的日常生活中，指纹锁、指纹考勤等都不乏其身影。光学指纹识别技术利用光的折射和反射原理，当光照射到手指上，经手指反射后由感光传感器(sensor)接收，感光传感器可将光信号转换为电学信号，从而进行读取。由于指纹谷和脊对光的反射不同，感光传感器所接收到谷和脊的反射光强不同，所转换的电流或者电压的大小也就不同，因此可以抓取指纹中的特殊点，提供唯一性的确认信息。但光学系统体积较大，导致光学指纹识别技术应用受限。
随着全面屏智能手机的兴起，采用光学指纹识别的屏内指纹识别大热，基于有机发光二极管(Organic Light Emitting Diode，简称OLED)显示屏幕，光学指纹系统可以省略复杂而体积庞大的光学系统，基于低温多晶硅(Low Temperature Poly-Silicon，简称LTPS) 工艺，使得屏下指纹识别成为可能。然而，利用OLED显示屏幕的光触发感光传感器，其亮度较低，导致感光传感器的光生电流微弱，对信号的采集与处理提出挑战。
 技术问题
现有技术中，有通过采用主动式驱动方案用于像素(Pixel)信号输出，实现提升指纹识别效率。但是，现有主动式驱动方案一般需要的薄膜晶体管(TFT)数量较多，不利于面内集成；而采用较少TFT的架构，对感光传感器的特性需求较高，提高了感光传感器的制备要求，不利于推广。
 技术解决方案
本申请实施例提供一种光学指纹识别电路及显示面板，在实现信号输出完成指纹识别的同时，可以降低对光电二极管反向击穿电压的要求，即降低对感光传感器的特性需求。
本申请实施例提供了一种光学指纹识别电路，所述电路包括一驱动晶体管以及一光电二极管；所述电路还包括：一复位单元，用于响应一复位信号以传送一复位电压，复位所述驱动晶体管的栅极电压；所述光电二极管的阳极接入一栅极扫描线，用于接收一扫描信号，其阴极接入所述驱动晶体管的栅极，所述光电二极管用于响应一第一电平的扫描信号进入反偏状态，在指纹谷或指纹脊对应的光强的光信号下进行曝光，产生相应的光电流对所述驱动晶体管的栅极进行放电，拉低所述驱动晶体管的栅极电压，所述光电二极管进一步用于响应一第二电平的扫描信号进入正向导通状态，其中，所述第二电平高于所述第一电平；一耦合电容，用于响应所述第二电平的扫描信号，以开启所述驱动晶体管；所述驱动晶体管，用于输出所述光信号，以进行指纹识别。
本申请实施例还提供了一种光学指纹识别电路，所述电路包括一驱动晶体管以及一光电二极管；所述电路还包括：一复位单元，用于响应一复位信号以传送一复位电压，复位所述驱动晶体管的栅极电压；所述光电二极管，用于响应一第一电平的扫描信号进入反偏状态，根据一光信号产生光电流输出至所述驱动晶体管的栅极，以及响应一第二电平的扫描信号进入正向导通状态，其中，所述第二电平高于所述第一电平；一耦合电容，用于响应一第二电平的扫描信号，以开启所述驱动晶体管；所述驱动晶体管，用于输出所述光信号，以进行指纹识别。
本申请实施例还提供了一种显示面板，包括阵列基板；所述阵列基板包括至少一光学指纹识别电路，所述光学指纹识别电路包括一驱动晶体管以及一光电二极管；所述光学指纹识别电路还包括：一复位单元，用于响应一复位信号以传送一复位电压，复位所述驱动晶体管的栅极电压；所述光电二极管，用于响应一第一电平的扫描信号进入反偏状态，根据一光信号产生光电流输出至所述驱动晶体管的栅极，以及响应一第二电平的扫描信号进入正向导通状态，并且其中，所述第二电平高于所述第一电平；一耦合电容，用于响应所述第二电平的扫描信号，以开启所述驱动晶体管；所述驱动晶体管，用于输出所述光信号，以进行指纹识别。
 有益效果
本申请在实现光信号输出以完成指纹识别的同时，可以有效避免光电二极管反向击穿风险，降低了对光电二极管反向击穿电压的要求，即降低了对感光传感器的特性要求，且电路结构简单，所需TFT较少，利于面内集成。
 附图说明
为了更清楚地说明本申请实施例中的技术方案，下面将对实施例描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例，对于本领域技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其它的附图。
图1为本申请光学指纹识别电路一实施例的电路图；
图2为光电二极管的伏安特性曲线；
图3为图1所示光学指纹识别电路的驱动时序图；
图4为现有光学指纹识别电路的电路图；
图5为图4所示光学指纹识别电路的驱动时序图；
图6为本申请显示面板架构示意图。
 本发明的实施方式
下面详细描述本申请的实施方式，所述实施方式的示例在附图中示出，其中自始至终相同或类似的标号表示相同或类似的组件或具有相同或类似功能的组件。本申请的说明书和权利要求书以及附图中的术语“第一”“第二”“第三”等(如果存在)是用于区别类似的对象，而不必用于描述特定的顺序或先后次序。应当理解，这样描述的对象在适当情况下可以互换。在本申请的描述中，“多个”的含义是两个或两个以上，除非另有明确具体的限定。此外，术语“包括”和“具有”以及它们的任何变形，意图在于覆盖不排它的包含。本申请所提到的方向用语，例如：上、下、左、右、前、后、内、外、侧面等，仅是参考附图的方向。
在本申请的描述中，需要说明的是，除非另有明确的规定和限定，术语“相连”、“连接”应做广义理解。例如，可以是电连接或相互通讯，可以是直接相连，也可以通过中间媒介间接相连，可以是两个元件内部的连通或两个元件的相互作用关系。应当理解，当称元件“耦接到”另一元件时，存在中间元件。对于本领域的普通技术人员而言，可以根据具体情况理解上述术语在本申请中的具体含义。
本申请提出一种光学指纹识别电路，通过在驱动晶体管的栅极增加复位单元，同时将光电二极管的阳极接入栅极扫描线；在复位阶段，通过复位单元对驱动晶体管的栅极进行复位，在曝光阶段，光电二极管处于反偏状态，在指纹谷/指纹脊对应的不同光强下进行曝光，对驱动晶体管的栅极进行放电，拉低驱动晶体管的栅极电压；在读取阶段，通过耦合电容对驱动晶体管的栅极进行电压耦合，使得驱动晶体管开启，输出光信号，同时，光电二极管两端电压同时抬升，不会增加反偏电压。本申请在实现光信号输出以完成指纹识别的同时，可以有效避免光电二极管反向击穿风险，降低了对光电二极管反向击穿电压的要求，即降低了对感光传感器的特性要求，且电路结构简单，所需TFT较少，利于面内集成。
请一并参阅图1-图3，其中，图1为本申请光学指纹识别电路一实施例的电路图，图2为光电二极管的伏安特性曲线，横坐标为电压值(单位V)，纵坐标为电流值(单位A)，图3为图1所示光学指纹识别电路的驱动时序图。
如图1所示，所述光学指纹识别电路包括一驱动晶体管T11、一光电二极管D11、一复位单元101以及一耦合电容C11。所述复位单元101用于响应一复位信号RST1以传送一复位电压Vinit，复位所述驱动晶体管T11的栅极电压。所述光电二极管D11用于响应一第一电平的扫描信号Gn进入反偏状态，根据一光信号产生光电流输出至所述驱动晶体管T11的栅极。所述耦合电容C11用于响应一第二电平的扫描信号Gn，以开启所述驱动晶体管T11；所述驱动晶体管T11用于输出所述光信号，以进行指纹识别；所述光电二极管D11进一步响应所述第二电平的扫描信号Gn进入正向导通状态。
其中，所述光电二极管D11进入反偏状态后，在指纹谷或指纹脊对应的光强的光信号下进行曝光，产生相应的光电流对所述驱动晶体管T11的栅极进行放电，拉低所述驱动晶体管T11的栅极电压。不同光强的光信号，对所述驱动晶体管T11的栅极进行放电的能力不同，进而使得所述驱动晶体管T11的栅极电压下降幅度不同，从而可以在后续进行指纹识别。
光电二极管是由一个PN结组成的半导体器件，具有单方向导电特性，是可以把光信号转换成电信号的光电传感器件。光电二极管在设计和制作时尽量使PN结的面积相对较大，以便接收入射光。光电二极管是在反向电压作用下工作的，没有光照时，反向电流极其微弱，叫暗电流；有光照时，反向电流迅速增大到几十微安，称为光电流。光的强度越大，反向电流也越大。光的变化引起光电二极管电流变化，这就可以把光信号转换成电信号。
如图2所示，光电二极管的工作区间分为正向工作区201、反向工作区202和反向击穿区203。当光电二极管的反偏电压的绝对值大于其所允许的反向工作电压的最高绝对值时，光电二极管会被反向击穿。本实施在所述驱动晶体管T11输出所述光信号的同时，所述光电二极管由反偏状态跳变为正向导通状态；为了保证所述驱动晶体管T11有效开启，栅极电压需要足够高，但由于所述光电二极管D11两端电压同时抬升，不会增加反偏电压，可以有效避免反向击穿风险，降低了对所述光电二极管D11反向击穿电压的要求，即降低了对感光传感器的特性要求。
继续参阅图1，在本实施例中，所述复位单元101包括：一复位晶体管T12，其控制端接入一复位扫描线，用于接收所述复位信号RST1，其第一端用于接收所述复位电压Vinit，其第二端接入所述驱动晶体管T11的栅极。所述复位晶体T12在所述复位信号RST1的控制下开启，将所述复位电压Vinit传送至所述驱动晶体管T11的栅极进行复位。即，在复位阶段所述驱动晶体管T11的栅极电压等于所述复位电压Vinit。其中，所述复位电压Vinit小于所述驱动晶体管T11的开启电压，以避免所述驱动晶体管T11在复位阶段导通。
进一步的实施例中，所述复位晶体管T12采用薄膜晶体管(TFT)，例如，可以为基于低温多晶硅工艺制备的低温多晶硅薄膜晶体管(LTPS_TFT) 。薄膜晶体管(TFT)的栅极作为所述复位晶体管T12的控制端。
在本实施例中，所述光电二极管D11的阳极接入一栅极扫描线，用于接收所述扫描信号Gn，其阴极接入所述驱动晶体管T11的栅极。所述光电二极管D11在所述扫描信号Gn为第一电平时进入反偏状态，在所述扫描信号Gn为第二电平时进入正向导通状态。其中，所述第二电平高于所述第一电平，例如，所述第二电平为高电平，所述第一电平为低电平，从而使得所述光电二极管D11实现反向偏置/正向导通。
进一步的实施例中，所述光电二极管D11为有机发光二极管(OLED)。
在本实施例中，所述耦合电容C11的第一极与所述光电二极管D11的阳极接入同一栅极扫描线，用于接收同一扫描信号Gn，其第二极接入所述驱动晶体管T11的栅极。所述耦合电容C11在所述扫描信号Gn为第二电平时，对所述驱动晶体管T11的栅极电压进行电压耦合，拉升所述栅极电压，以开启所述驱动晶体管。通过耦合电容C11进行电压耦合，使得所述驱动晶体管T11的栅极电压升高，当所述驱动晶体管T11的栅极电压大于所述驱动晶体管T11的开启电压时，使得所述驱动晶体管T11的开启，以完成光信号的输出。
在本实施例中，所述驱动晶体管T11的第一端用于接收一电源电压VDD，其第二端接入一数据读取线RD(Readout)。所述驱动晶体管T11在开启时，输出所述光信号至所述数据读取线RD，相关的IC通过所述数据读取线RD即可获取所述光信号进行指纹识别。
进一步的实施例中，所述驱动晶体管T11也采用薄膜晶体管(TFT)，例如，可以为基于低温多晶硅工艺制备的低温多晶硅薄膜晶体管(LTPS_TFT) ，从而利于制备工艺的实施以及利于面内集成。
以下结合图1、图3，对本申请光学指纹识别电路的工作原理作进一步解释说明。
具体工作原理如下：
1)复位阶段A11：扫描信号Gn为低电平(Low)，复位信号RST1为高电平(High)，复位晶体管T12开启，将复位电压Vinit输入到驱动晶体管T11的栅极(以Q1表示)进行复位；Q1点电压等于复位电压Vinit。
2)曝光阶段A12：复位信号RST1跳变为低电平，复位晶体管T12关闭；扫描信号Gn信号仍为低电平，由于Q1点电压较高，光电二极管D11处于反偏状态；光电二极管D11在指纹谷/指纹脊对应的不同光强的光信号下进行曝光；光照射在光电二极管D11上时，光电二极管D11生成一定的光电流；光电流对Q1点进行放电，Q1点电压出现下降，不同光强，电压下降幅度不同。
3)读取阶段A13：扫描信号Gn跳变为高电平，并通过耦合电容C11对Q1点进行电压耦合，使得Q1点电压升高；当Q1点电压大于驱动晶体管T11的开启电压时，驱动晶体管T11开启，输出光信号至数据读取线RD(图3中RD1示意读取的光信号)，进而通过数据读取线RD输出至相应IC。在此阶段，由于光电二极管D11两端电压同时抬升(Gn跳变为高电平、同时Q1点电压升高)，所以光电二极管D11的反偏电压不会增加，可以有效避免反向击穿风险。
作为对比，请一并参阅图4-图5，其中，图4为现有光学指纹识别电路的电路图，图5为图4所示光学指纹识别电路的驱动时序图。
如图4所示，其光电二极管D21的阳极接入一复位信号线，用于接收复位信号PR1，以对驱动晶体管T21进行复位；其耦合电容C21接入一栅极扫描线，用于接收扫描信号Gn，以控制驱动晶体管T21开启。
结合图4-图5，现有光学指纹识别电路的工作原理如下：
a)复位阶段A21：扫描信号Gn为低电平(Low)，复位信号PR1为高电平(High)，光电二极管D21正向导通，对驱动晶体管T21的栅极(以Q2表示)进行复位。
b)曝光阶段A22：复位信号PR1跳变为低电平，光电二极管D21处于反偏状态；光电二极管D21在指纹谷/指纹脊对应的不同光强的光信号下进行曝光生成一定的光电流；光电流对Q2点进行放电，Q2点电压出现下降，不同光强，电压下降幅度不同。
c)读取阶段A23：扫描信号Gn跳变为高电平，并通过耦合电容C21对Q2点进行电压耦合，使得Q2点电压升高；当Q2点电压大于驱动晶体管T21的开启电压时，驱动晶体管T21开启，输出光信号至数据读取线RD(图5中RD1示意读取的光信号。
为了保证驱动晶体管T21有效开启，Q2点电压要求足够高，使得光电二极管D21的反偏电压较高，存在反向击穿的风险，因此该驱动方案要求光电二极管D21的反向击穿电压足够高，以避免击穿，对感光传感器的制备要求较高。
基于同一发明构思，本申请还提供了一种显示面板。
请参阅图6，本申请显示面板架构示意图。所述显示面板60包括阵列基板61，所述阵列基板61包括至少一光学指纹识别电路611。所述光学指纹识别电路611采用本申请图1所述的光学指纹识别电路。所述光学指纹识别电路611的电路组件连接方式及工作原理已详述于前，此处不再赘述。
采用本申请光学指纹识别电路的显示面板，在实现光信号输出以完成指纹识别的同时，可以有效避免光电二极管反向击穿风险，降低了对光电二极管反向击穿电压的要求，即降低了对感光传感器的的制备要求，且电路结构简单，所需TFT较少，利于面内集成。
可以理解的是，对本领域普通技术人员来说，可以根据本申请的技术方案及其发明构思加以等同替换或改变，而所有这些改变或替换都应属于本申请所附的权利要求的保护范围。

Claims (20)

  1. 一种光学指纹识别电路，所述电路包括一驱动晶体管以及一光电二极管；其中，所述电路还包括：
    一复位单元，用于响应一复位信号以传送一复位电压，复位所述驱动晶体管的栅极电压；
    所述光电二极管的阳极接入一栅极扫描线，用于接收一扫描信号，其阴极接入所述驱动晶体管的栅极，所述光电二极管用于响应一第一电平的扫描信号进入反偏状态，在指纹谷或指纹脊对应的光强的光信号下进行曝光，产生相应的光电流对所述驱动晶体管的栅极进行放电，拉低所述驱动晶体管的栅极电压，所述光电二极管进一步用于响应一第二电平的扫描信号进入正向导通状态，并且其中，所述第二电平高于所述第一电平；
    一耦合电容，用于响应所述第二电平的扫描信号，以开启所述驱动晶体管；
    所述驱动晶体管，用于输出所述光信号，以进行指纹识别。
  2. 如权利要求1所述的电路，其中，所述复位单元包括：一复位晶体管，其控制端接入一复位扫描线，用于接收所述复位信号，其第一端用于接收所述复位电压，其第二端接入所述驱动晶体管的栅极；并且其中，所述复位晶体在所述复位信号的控制下开启，将所述复位电压传送至所述驱动晶体管的栅极进行复位。
  3. 如权利要求2所述的电路，其中，所述复位晶体管采用薄膜晶体管。
  4. 如权利要求1所述的电路，其中，所述耦合电容的第一极接入所述栅极扫描线，用于接收所述扫描信号，其第二极接入所述驱动晶体管的栅极；并且其中，所述耦合电容在所述扫描信号为第二电平时，对所述驱动晶体管的栅极电压进行电压耦合，拉升所述栅极电压，以开启所述驱动晶体管。
  5. 如权利要求1所述的电路，其中，所述驱动晶体管的第一端用于接收一电源电压，其第二端接入一数据读取线；并且其中，所述驱动晶体管在开启时，输出所述光信号至所述数据读取线。
  6. 如权利要求1所述的电路，其中，所述光电二极管为有机发光二极管。
  7. 如权利要求1所述的电路，其中，所述驱动晶体管采用薄膜晶体管。
  8. 一种光学指纹识别电路，所述电路包括一驱动晶体管以及一光电二极管；其中，所述电路还包括：
    一复位单元，用于响应一复位信号以传送一复位电压，复位所述驱动晶体管的栅极电压；
    所述光电二极管，用于响应一第一电平的扫描信号进入反偏状态，根据一光信号产生光电流输出至所述驱动晶体管的栅极，以及响应一第二电平的扫描信号进入正向导通状态，并且其中，所述第二电平高于所述第一电平；
    一耦合电容，用于响应所述第二电平的扫描信号，以开启所述驱动晶体管；
    所述驱动晶体管，用于输出所述光信号，以进行指纹识别。
  9. 如权利要求8所述的电路，其中，所述光电二极管进入反偏状态后，在指纹谷或指纹脊对应的光强的光信号下进行曝光，产生相应的光电流对所述驱动晶体管的栅极进行放电，拉低所述驱动晶体管的栅极电压。
  10. 如权利要求8所述的电路，其中，所述复位单元包括：一复位晶体管，其控制端接入一复位扫描线，用于接收所述复位信号，其第一端用于接收所述复位电压，其第二端接入所述驱动晶体管的栅极；并且其中，所述复位晶体在所述复位信号的控制下开启，将所述复位电压传送至所述驱动晶体管的栅极进行复位。
  11. 如权利要求10所述的电路，其中，所述复位晶体管采用薄膜晶体管。
  12. 如权利要求8所述的电路，其中，所述光电二极管的阳极接入一栅极扫描线，用于接收一扫描信号，其阴极接入所述驱动晶体管的栅极；并且其中，所述光电二极管在所述扫描信号为第一电平时进入反偏状态，在所述扫描信号为第二电平时进入正向导通状态。
  13. 如权利要求12所述的电路，其中，所述耦合电容的第一极接入所述栅极扫描线，用于接收所述扫描信号，其第二极接入所述驱动晶体管的栅极；并且其中，所述耦合电容在所述扫描信号为第二电平时，对所述驱动晶体管的栅极电压进行电压耦合，拉升所述栅极电压，以开启所述驱动晶体管。
  14. 如权利要求8所述的电路，其中，所述驱动晶体管的第一端用于接收一电源电压，其第二端接入一数据读取线；并且其中，所述驱动晶体管在开启时，输出所述光信号至所述数据读取线。
  15. 如权利要求8所述的电路，其中，所述光电二极管为有机发光二极管。
  16. 如权利要求8所述的电路，其中，所述驱动晶体管采用薄膜晶体管。
  17. 一种显示面板，包括阵列基板；其中，所述阵列基板包括至少一光学指纹识别电路，所述光学指纹识别电路包括一驱动晶体管以及一光电二极管；所述光学指纹识别电路还包括：
    一复位单元，用于响应一复位信号以传送一复位电压，复位所述驱动晶体管的栅极电压；
    所述光电二极管，用于响应一第一电平的扫描信号进入反偏状态，根据一光信号产生光电流输出至所述驱动晶体管的栅极，以及响应一第二电平的扫描信号进入正向导通状态，并且其中，所述第二电平高于所述第一电平；
    一耦合电容，用于响应所述第二电平的扫描信号，以开启所述驱动晶体管；
    所述驱动晶体管，用于输出所述光信号，以进行指纹识别。
  18. 如权利要求17所述的显示面板，其中，所述复位单元包括：一复位晶体管，其控制端接入一复位扫描线，用于接收所述复位信号，其第一端用于接收所述复位电压，其第二端接入所述驱动晶体管的栅极；并且其中，所述复位晶体在所述复位信号的控制下开启，将所述复位电压传送至所述驱动晶体管的栅极进行复位。
  19. 如权利要求17所述的显示面板，其中，所述光电二极管进入反偏状态后，在指纹谷或指纹脊对应的光强的光信号下进行曝光，产生相应的光电流对所述驱动晶体管的栅极进行放电，拉低所述驱动晶体管的栅极电压。
  20. 如权利要求17所述的显示面板，其中，所述光电二极管的阳极接入一栅极扫描线，用于接收一扫描信号，其阴极接入所述驱动晶体管的栅极；所述耦合电容的第一极接入所述栅极扫描线，用于接收所述扫描信号，其第二极接入所述驱动晶体管的栅极，并且其中，所述耦合电容在所述扫描信号为第二电平时，对所述驱动晶体管的栅极电压进行电压耦合，拉升所述栅极电压，以开启所述驱动晶体管。
PCT/CN2020/097760 2020-06-09 2020-06-23 光学指纹识别电路及显示面板 WO2021248561A1 (zh)

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