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WO2015139447A1 - 电容指纹感应电路和感应器 - Google Patents

电容指纹感应电路和感应器 Download PDF

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Publication number
WO2015139447A1
WO2015139447A1 PCT/CN2014/088451 CN2014088451W WO2015139447A1 WO 2015139447 A1 WO2015139447 A1 WO 2015139447A1 CN 2014088451 W CN2014088451 W CN 2014088451W WO 2015139447 A1 WO2015139447 A1 WO 2015139447A1
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WO
WIPO (PCT)
Prior art keywords
amplifier
cancellation
sensing circuit
capacitive fingerprint
output
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PCT/CN2014/088451
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English (en)
French (fr)
Inventor
张均军
詹昶
Original Assignee
深圳市汇顶科技股份有限公司
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Application filed by 深圳市汇顶科技股份有限公司 filed Critical 深圳市汇顶科技股份有限公司
Publication of WO2015139447A1 publication Critical patent/WO2015139447A1/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
    • G06V40/1306—Sensors therefor non-optical, e.g. ultrasonic or capacitive sensing

Definitions

  • the invention belongs to the field of fingerprint recognition, and in particular relates to a capacitive fingerprint sensing circuit and an inductor.
  • Capacitive fingerprint sensing system uses different sizes of sensing capacitors corresponding to "peak” and “valley” contained in the fingerprint, and the amplitude of the output signal is different under the excitation of the same AC signal, and the images of "peak” and “valley” are used. The information is converted into a corresponding electrical signal.
  • a non-conductive thick dielectric layer is placed on the surface of the fingerprint sensor to generate a dielectric layer-related capacitance (common mode portion); That is, the fingerprint "peak” and “valley” produce capacitances related to the depth of the texture, which constitute the coupling capacitance (differential mode portion) of the finger to the sensor sensing electrode.
  • the prior art is shown in FIG. 1.
  • the sum of the differential mode portion and the common mode portion is directly amplified by the charge amplifier, and the proportion of the differential mode portion in the sum is small, so that the differential mode portion is submerged in the sum, It is easy to distinguish the difference between "peak” and “valley", that is, the sensitivity of the fingerprint sensor is low.
  • An object of the present invention is to provide a capacitive fingerprint sensing circuit and an inductor, which are intended to solve the problem of poor sensitivity of the existing fingerprint sensor.
  • a capacitive fingerprint sensing circuit includes a cancellation module and a feedback amplifier.
  • the first input end of the cancellation module is connected to the first external driving source, and the second input end of the cancellation module is pressed by the first
  • the finger of the two input ends is connected with the second external driving source, and the output end of the canceling module is connected with the input end of the feedback amplifier, and the signals output by the first external driving source and the second external driving source are mutually inverted, and the first external driving source is sent
  • the signal input to the cancellation module and the signal coupled to the cancellation module by the second external driving source are offset, and a fingerprint sensing signal related to the fingerprint depth is obtained, and the output of the feedback amplifier outputs the amplified fingerprint sensing signal.
  • the cancellation module includes a sensing capacitor C s and a cancellation capacitor C c .
  • the input terminal of the sensing capacitor C s is a second input terminal of the cancellation module, and the output terminal of the sensing capacitor C s is connected to the output terminal of the cancellation capacitor C c to cancel
  • the input of C c of the capacitor is the first input of the cancellation module, and the connection point of the sensing capacitor C s and the cancellation capacitor C c is the output of the cancellation module.
  • the second input end of the canceling module comprises an inductive plate, and the finger and the inductive plate are separated by a dielectric layer to form a sensing capacitor C s , and the first input end of the canceling module comprises an offset plate, an inductive plate and an offset A cancellation capacitor C c is formed between the plates.
  • the inductive plate and the counterplate are each formed of a metal layer.
  • the feedback amplifier is a current amplifier comprising a first low noise amplifier and a resistor connected between the input and the output of the first low noise amplifier.
  • the feedback amplifier is a charge amplifier and the charge amplifier comprises a second low noise amplifier And a feedback capacitor connected between the input and the output of the second low noise amplifier.
  • the feedback amplifier further includes a reset switch coupled between the input and the output of the first low noise amplifier or the second low noise amplifier.
  • the capacitive fingerprint sensing circuit further comprises a driving amplifier and a cancellation amplifier, wherein the input end of the driving amplifier is connected to the external driving source, and the output end of the driving amplifier is connected with the finger pressed on the second input end of the canceling module; the input end of the canceling amplifier is externally connected
  • the driving source is connected, and the output of the cancellation amplifier is connected to the first input of the cancellation module; the gains of the driving amplifier and the cancellation amplifier are inverted.
  • the invention also provides a capacitive fingerprint sensor.
  • the capacitive fingerprint sensor comprises a plurality of pixel units, each pixel unit corresponds to a capacitive fingerprint sensing circuit, and the capacitive fingerprint sensing circuit is any one of the above capacitive fingerprint sensing circuits.
  • the capacitive fingerprint sensor further comprises a driving amplifier and a cancellation amplifier, wherein the input end of the driving amplifier is connected to the external driving source, and the output end of the driving amplifier is connected to the finger of the second input end of the canceling module of each capacitive fingerprint sensing circuit.
  • the input end of the cancellation amplifier is connected to an external driving source, and the output end of the cancellation amplifier is connected to the first input end of the cancellation module of each capacitive fingerprint sensing circuit, and the gains of the driving amplifier and the cancellation amplifier are inverted.
  • the invention attenuates the portion unrelated to the fingerprint by the external driving source and the canceling module which are mutually inverted, and only amplifies the differential mode signal related to the depth of the fingerprint, so that the subsequent cascaded amplifier is not easy to be saturated, thereby reducing the realization of the fingerprint sensor. Difficulty, improving the sensitivity of the fingerprint sensor.
  • the dielectric layer of different thicknesses and materials can be adapted to improve the compatibility of the fingerprint sensor. Due to the introduction of feedback amplifier stability
  • the voltage of the plate should be independent of the parasitic capacitance of the sensing electrode, which improves the reliability of the system.
  • the capacitive fingerprint sensing circuit of the present invention has a simple structure, is compatible with a standard CMOS process, and has low integration cost.
  • FIG. 1 is a circuit diagram of a prior art fingerprint sensor
  • FIG. 2 is a circuit diagram of a capacitive fingerprint sensing circuit according to Embodiment 1 of the present invention.
  • FIG. 3 is another circuit diagram of a capacitive fingerprint sensing circuit according to Embodiment 1 of the present invention.
  • FIG. 4 is a structural diagram of a capacitive fingerprint sensing circuit according to Embodiment 1 of the present invention.
  • FIG. 5 is a circuit diagram of a capacitive fingerprint sensor according to Embodiment 2 of the present invention.
  • a first embodiment of the present invention provides a capacitive fingerprint sensing circuit.
  • the capacitive fingerprint sensing circuit of the first embodiment of the present invention includes a cancellation module 10 and a feedback amplifier 20.
  • the first input end of the cancellation module 10 is connected to the first external driving source VS1, and the second input end of the cancellation module 10 is provided.
  • the finger connected to the second input terminal is connected to the second external driving source VS2, and the output end of the canceling module 10 is connected to the input end of the feedback amplifier 20, and the signals output by the first external driving source VS1 and the second external driving source VS2 are mutually For inversion, the first The signal sent from the external driving source VS1 to the canceling module 10 and the signal coupled to the second external driving source VS2 to the canceling module 10 are offset, and the fingerprint sensing signal related to the fingerprint depth is obtained, and the output of the feedback amplifier 20 is amplified. Fingerprint sensing signal.
  • the feedback amplifier 20 can be a current amplifier or a charge amplifier. For convenience of description, the charge amplifier 20 will be described as an example.
  • the signal portion unrelated to the fingerprint is first attenuated by the canceling operation of the canceling module 10, and then the weak signal portion related to the texture is amplified by the charge amplifier 20, and then output to the fingerprint sensor.
  • the other parts perform operations such as enlargement, analog-to-digital conversion, image stitching, etc., extracting valid fingerprint information, and realizing the processing of the fingerprint signal.
  • the cancellation module 10 includes a sensing capacitor C s and a cancellation capacitor C c .
  • An input terminal for sensing capacitor C s cancellation module 10 a second input terminal, the sensing capacitor C s is connected to the output terminal of the output capacitor C c is canceled, canceling the capacitance C c is input to a first input 10 of the cancellation module
  • the connection point of the sensing capacitor C s and the cancellation capacitor C c is the output of the cancellation module 10 .
  • the charge amplifier 20 includes a second Low Noise Amplifier (LNA) 107 and a feedback capacitor C fb connected between the input and output of the second low noise amplifier 107.
  • the charge amplifier 20 can also include a reset switch SW coupled between the input and output of the second low noise amplifier 107 for setting the input and output node voltages to a bias voltage during the reset phase.
  • the capacitive fingerprint sensing circuit may further include a driving amplifier 101 and a cancellation amplifier 102, and an input terminal of the driving amplifier 101 and an external driving source VS.
  • the output terminal is connected to the finger pressed on the second input end of the canceling module 10, the input end of the canceling amplifier 102 is connected to the external driving source VS, the output end is connected to the first input end of the canceling module 10, and the driving amplifier 101 and the canceling amplifier 102 are connected.
  • the gain is inverted.
  • FIG. 4 The structure diagram of the capacitive fingerprint sensing circuit is shown in FIG. 4, which includes an induction plate 201, a canceling plate 202 and a feedback plate 203.
  • the finger and the sensing plate 201 are separated by an insulating dielectric layer 204 when the finger contacts or When pressed on a pixel unit of the fingerprint sensor, a sensing capacitor C s is formed between the finger and the sensing plate, a canceling capacitor C c is formed between the sensing plate 201 and the canceling plate 202, and the feedback plate 203 and the sensing pole are formed.
  • a feedback capacitance C fb is formed between the plates 202.
  • the induction plate 201, the canceling plate 202 and the feedback plate 203 are each formed of a metal layer.
  • the capacitance value of the sensing capacitor C s is proportional to the dielectric constant of the insulating material, and inversely proportional to the distance between the upper and lower plates, so the size of the sensing capacitor C s corresponding to the peaks and valleys of the finger
  • the sensing capacitor C s can be divided into two parts: a common mode part (related to the material and thickness of the insulating dielectric layer 204), and a differential mode part (related to the depth of the fingerprint line).
  • the signals coupled to the sensing plate 201 are also correspondingly divided into a common mode portion and a differential mode portion, and the capacitance difference between the fingerprint peaks and valleys is an effective detection target of the fingerprint sensing circuit.
  • the driving amplifier 101, the finger and the sensing capacitor C s form a coupling signal path
  • the cancellation amplifier 102 and the cancellation capacitor C c form a cancellation signal path, which are connected to the induction plate 201 and then sent to the second low noise.
  • the amplifier 107 performs signal amplification.
  • the capacitance associated with the fingerprint path is distinguished, and the gray scale information of the peaks and valleys is retained.
  • the external driving source VS is amplified A1 times by the driving amplifier 101 and then loaded onto the finger, and coupled to the sensing plate 201 through the sensing capacitor C s .
  • the external driving source VS is amplified by A2 times by the cancellation amplifier 102 and coupled to the induction plate 201 through the cancellation capacitor C c .
  • the common mode portion of the coupled signal is partially or completely cancelled, and the differential mode portion is fed to the negative input terminal of the second low noise amplifier 107.
  • the feedback capacitor C fb is connected between the negative input terminal of the second low noise amplifier 107 and the output. Due to the negative feedback of the second low noise amplifier 107, the voltage of the induction plate 201 remains unchanged, and the sensing capacitor C s and the cancellation capacitor After the charge of C c is summed, it is transferred to the feedback capacitor C fb to obtain an output voltage VOUT.
  • the reset switch SW is connected between the input and output of the second low noise amplifier 107, and sets the input and output node voltages to the bias voltage VCM during the reset phase.
  • the charge coupled to the inductive plate 201 by the external drive source VS through the coupling signal path is: Vs*A1*Cs.
  • the charge coupled to the sensing electrode 201 through the cancellation signal path is: Vs*A2*Cc.
  • the voltage of the sensing plate 201 remains unchanged, and the charge of the parasitic capacitance Cg does not change, and does not participate in the signal amplification process.
  • the output voltage is:
  • Vout (VS*A1*Cs+VS*A2*Cc)/Cfb;
  • Voutr (VS*A1*Csr+VS*A2*Cc)/Cfb;
  • the output voltage corresponding to the valley is:
  • the insulating material has a relative dielectric constant of 10 and a thickness of 300 um.
  • the contact between the finger and the fingerprint sensing circuit can be assumed to be a plate capacitor.
  • the area corresponding to a single pixel is 50 um * 50 um.
  • the sensing capacitance The size is: Cs ⁇ 0.74fF.
  • the subsequent amplifier gain of the capacitive fingerprint sensing circuit can be set to be large enough (eg, 15 times) without saturation.
  • the amplitude of the effective signal, that is, the differential mode signal, is amplified by a factor of 15 to improve the sensitivity of the texture recognition.
  • the charge amplifier 20 in the above embodiment can also be replaced with a current amplifier to perform the same function.
  • the current amplifier includes a first low noise amplifier 107 and a resistor Rfb coupled between the input and output of the first low noise amplifier 107, and may further include a connection between the input and the output of the first low noise amplifier 107. Reset switch SW.
  • the capacitive fingerprint sensing circuit of the first embodiment of the present invention improves the sensitivity of the fingerprint sensing circuit by offset operation, facilitates subsequent amplification, and improves subsequent processing accuracy. Further, by changing the gain of the cancellation amplifier, the dielectric layer of different thicknesses and materials can be adapted to improve the compatibility of the fingerprint sensor. Stable due to the introduction of feedback amplifier Inductive plate voltage, so the signal processing process is independent of the parasitic capacitance of the sensing electrode, which improves system reliability.
  • the circuit structure of the embodiment of the invention is simple, compatible with a standard CMOS process, and the integration cost is low.
  • the capacitive fingerprint sensing circuit can be used in a small area, one pixel unit corresponds to one capacitive fingerprint sensing circuit, and the driving amplifier and the cancellation amplifier can be shared by a plurality of pixel units. Therefore, the second embodiment of the present invention provides a capacitive fingerprint sensor. As shown in FIG. 6, the capacitive fingerprint sensor of the second embodiment of the present invention includes a plurality of pixel units, and each pixel unit corresponds to a capacitive fingerprint sensing circuit. The driver amplifier 401 and the canceling amplifier 402 are further included.
  • the input end of the driving amplifier 401 is connected to the external driving source VS, and the output terminal is connected to the second input end of the canceling module 40 of each capacitive fingerprint sensing circuit to cancel the amplifier 402.
  • the input terminal is connected to the external driving source VS, and the output terminal is connected to the first input terminal of the cancellation module 40 of each capacitive fingerprint sensing circuit, and the gains of the driving amplifier 401 and the cancellation amplifier 402 are inverted.
  • the structure and working principle of the capacitive fingerprint sensing circuit are similar to those of the capacitive fingerprint sensing circuit shown in FIG. 2 to FIG. 3, and are not described herein again.
  • the capacitive fingerprint sensing circuit is a basic unit of the capacitive fingerprint sensor.
  • the finger couples the driving signal to the sensing electrode 301 through the dielectric layer, and the driving signal is also sent to the sensing electrode 301 through the built-in cancellation capacitor C c , thereby attenuating or eliminating the fingerprint.
  • the unrelated common coupled signals are amplified and output to subsequent processing circuits.
  • the invention attenuates the portion unrelated to the fingerprint by the external driving source and the canceling module which are mutually inverted, and only amplifies the differential mode signal related to the depth of the fingerprint, so that the subsequent cascaded amplifier is not easy to be saturated, thereby reducing the realization of the fingerprint sensor. Difficulty, improving the sensitivity of the fingerprint sensor. Further, by changing the gain of the cancellation amplifier, the dielectric layer of different thicknesses and materials can be adapted to improve the compatibility of the fingerprint sensor. Since the feedback amplifier is used to stabilize the voltage of the sensing plate, the signal processing process is independent of the parasitic capacitance of the sensing electrode, and the reliability of the system is improved.
  • the capacitive fingerprint sensing circuit of the present invention has a simple structure, is compatible with a standard CMOS process, and has low integration cost.

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Abstract

本发明适用于指纹识别领域，提供了一种电容指纹感应电路和感应器，感应电路包括抵消模块和反馈放大器，抵消模块的第一输入端与第一外接驱动源连接，抵消模块的第二输入端通过按压在该第二输入端的手指与第二外接驱动源连接，抵消模块的输出端与反馈放大器的输入端连接，第一外接驱动源和第二外接驱动源输出的信号互为反相，第一外接驱动源接入到抵消模块的信号与第二外接驱动源耦合到抵消模块的信号产生抵消，得到与指纹深度相关的指纹感应信号，反馈放大器的输出端输出经放大后的指纹感应信号。本发明实施例的电容指纹感应电路和感应器通过互为反相的外接驱动源和抵消模块衰减了与指纹无关的部分，仅放大差模信号，提高指纹感应的灵敏度。

Description

电容指纹感应电路和感应器 技术领域
本发明属于指纹识别领域，尤其涉及一种电容指纹感应电路和感应器。
背景技术
人的手指纹路有深度差异，凸的地方称为“峰(ridge)”，凹的地方称为“谷(valley)”。电容式指纹感应系统利用指纹上包含的“峰”和“谷”对应的感应电容大小不同，在同样的交流信号激励下输出信号的幅度也不同的原理，将“峰”和“谷”的图像信息转化为相应的电信号。
为防止反复触摸过程对指纹感应器的静电损伤，以及提高机械强度，需在指纹感应器表面放置不导电的厚介质层(cover)，从而产生介质层相关电容(共模部分)；另外指纹深度即指纹“峰”和“谷”产生与纹路深度相关的电容，两者构成了手指到传感器感应电极的耦合电容(差模部分)。现有技术如图1所示，通过电荷放大器将差模部分和共模部分的总和直接放大，差模部分在该总和中所占的比例很小，如此差模部分会淹没在总和里，不容易分辨出“峰”和“谷”的区别，即指纹感应器的灵敏度较低。
发明内容
本发明实施例的目的在于提供一种电容指纹感应电路和感应器，旨在解决现有的指纹感应器灵敏度差的问题。
本发明实施例是这样实现的，一种电容指纹感应电路，包括抵消模块和反馈放大器，抵消模块的第一输入端与第一外接驱动源连接，抵消模块的第二输入端通过按压在该第二输入端的手指与第二外接驱动源连接，抵消模块的输出端与反馈放大器的输入端连接，第一外接驱动源和第二外接驱动源输出的信号互为反相，第一外接驱动源送入到抵消模块的信号与第二外接驱动源耦合到抵消模块的信号产生抵消，得到与指纹深度相关的指纹感应信号，反馈放大器的输出端输出经放大后的指纹感应信号。
优选地，抵消模块包括感应电容Cs和抵消电容Cc，感应电容Cs的输入端为抵消模块的第二输入端，感应电容Cs的输出端与抵消电容Cc的输出端连接，抵消电容的Cc的输入端为抵消模块的第一输入端，感应电容Cs和抵消电容Cc的连接点为抵消模块的输出端。
优选地，抵消模块的第二输入端包含感应极板，手指和感应极板之间通过介质层隔离，形成感应电容Cs，抵消模块的第一输入端包含抵消极板，感应极板和抵消极板之间形成抵消电容Cc。
优选地，感应极板和抵消极板均由金属层构成。
优选地，反馈放大器为电流放大器，电流放大器包括第一低噪放大器以及连接在第一低噪放大器的输入端和输出端之间的电阻。
优选地，反馈放大器为电荷放大器，电荷放大器包括第二低噪放 大器以及连接在第二低噪放大器的输入端和输出端之间的反馈电容。
优选地，反馈放大器还包括连接在第一低噪放大器或者第二低噪放大器的输入端和输出端之间的复位开关。
优选地，电容指纹感应电路还包括驱动放大器和抵消放大器，驱动放大器的输入端与外接驱动源连接，驱动放大器的输出端与按压在抵消模块第二输入端的手指连接；抵消放大器的输入端与外接驱动源连接，抵消放大器的输出端与抵消模块的第一输入端连接；驱动放大器和抵消放大器的增益反相。
本发明还提出一种电容指纹感应器，电容指纹感应器包括多个像素单元，每个像素单元对应一个电容指纹感应电路，电容指纹感应电路为如上的任一种电容指纹感应电路。
优选地，电容指纹感应器还包括驱动放大器和抵消放大器，驱动放大器的输入端与外接驱动源连接，驱动放大器的输出端与按压在每一电容指纹感应电路的抵消模块的第二输入端的手指连接，抵消放大器的输入端与外接驱动源连接，抵消放大器的输出端与每一电容指纹感应电路的抵消模块的第一输入端连接，驱动放大器和抵消放大器的增益反相。
本发明通过互为反相的外接驱动源和抵消模块衰减了与指纹无关的部分，仅放大与指纹深度相关的差模信号，因此后续级联的放大器不容易饱和，降低了指纹感应器的实现难度，提高了指纹感应器的灵敏度。优选地，通过改变抵消放大器的增益，可适应不同厚度和材料的介质层，提高指纹传感器的兼容性。由于引入反馈放大器稳定感 应极板的电压，因此信号处理过程与感应电极的寄生电容无关，提高了系统可靠性，本发明中的电容指纹感应电路结构简洁，兼容标准CMOS工艺，集成成本低。
附图说明
图1是现有技术的指纹感应器的电路图；
图2是本发明实施例一提供的电容指纹感应电路的电路图；
图3是本发明实施例一提供的电容指纹感应电路的另一电路图；
图4是本发明实施例一提供的电容指纹感应电路的结构图；
图5是本发明实施例二提供的电容指纹感应器的电路图。
具体实施方式
为了使本发明的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本发明进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不用于限定本发明。
实施例一
本发明实施例一提出一种电容指纹感应电路。如图2所示，本发明实施例一的电容指纹感应电路包括抵消模块10和反馈放大器20，抵消模块10的第一输入端与第一外接驱动源VS1连接，抵消模块10的第二输入端通过按压在该第二输入端的手指与第二外接驱动源VS2连接，抵消模块10的输出端与反馈放大器20的输入端连接，第一外接驱动源VS1和第二外接驱动源VS2输出的信号互为反相，第 一外接驱动源VS1送入到抵消模块10的信号与第二外接驱动源VS2耦合到抵消模块10的信号产生抵消，得到与指纹深度相关的指纹感应信号，反馈放大器20的输出端输出经放大后的指纹感应信号。在本发明实施例一中，反馈放大器20可为电流放大器或者电荷放大器，为说明方便，以电荷放大器20为例进行说明。
本发明实施例一在放大手指耦合信号之前，首先通过抵消模块10的抵消操作，衰减与指纹无关的信号部分，然后通过电荷放大器20放大与纹路相关的微弱信号部分，再输出至指纹感应器的其他部分进行放大、模数转换、图像拼接等操作，提取出有效的指纹信息，实现对指纹信号的处理。
如图3所示，抵消模块10包括感应电容Cs和抵消电容Cc。感应电容Cs的输入端为抵消模块10的第二输入端，感应电容Cs的输出端与抵消电容Cc的输出端连接，抵消电容的Cc的输入端为抵消模块10的第一输入端，感应电容Cs和抵消电容Cc的连接点为抵消模块10的输出端。
电荷放大器20包括第二低噪放大器(Low Noise Amplifier，LNA)107以及连接在第二低噪放大器107的输入端和输出端之间的反馈电容Cfb。电荷放大器20还可包括连接在第二低噪放大器107的输入端和输出端之间的复位开关SW，用于在复位阶段将输入和输出节点电压置为偏置电压。
在本发明实施例一中，电容指纹感应电路还可包括驱动放大器101和抵消放大器102，驱动放大器101的输入端与外接驱动源VS 连接，输出端与按压在抵消模块10第二输入端的手指连接，抵消放大器102的输入端与外接驱动源VS连接，输出端与抵消模块10的第一输入端连接，驱动放大器101和抵消放大器102的增益反相。
电容指纹感应电路的结构图如图4所示，其中包含感应极板201、抵消极板202和反馈极板203，手指与感应极板201之间通过绝缘的介质层204隔离，当手指接触或按压在指纹感应器的某一像素单元上时，手指和感应极板之间形成感应电容Cs，感应极板201与抵消极板202之间形成抵消电容Cc，反馈极板203与感应极板202之间形成反馈电容Cfb。为了提高电路的集成度，感应极板201、抵消极板202和反馈极板203均采用金属层构成。
根据平板电容的计算公式可知，感应电容Cs的电容值与绝缘材料的介电常数成正比，与上下极板之间的距离成反比，因此手指的峰和谷所对应的感应电容Cs大小不同，感应电容Cs可分为两部分：共模部分(与绝缘的介质层204的材料、厚度等因素相关)；差模部分(与指纹纹路的深浅相关)。耦合到感应极板201的信号也相应的区分为共模部分以及差模部分，而手指纹路峰和谷的电容差即为指纹感应电路的有效探测对象。
本发明实施例一中，驱动放大器101、手指、感应电容Cs构成耦合信号通路，抵消放大器102、抵消电容Cc构成抵消信号通路，两者连接到感应极板201，再送入第二低噪放大器107进行信号放大。在手指到指纹感应电路较弱的耦合电容中区分出与手指纹路相关的电容，并保留峰谷的灰度信息。
具体地，当手指接触到指纹感应电路的表面时，外接驱动源VS经过驱动放大器101放大A1倍后加载到手指上，并通过感应电容Cs耦合到感应极板201。同时，外接驱动源VS经抵消放大器102放大A2倍后通过抵消电容Cc耦合到感应极板201。两个信号叠加之后，耦合信号的共模部分被部分或者完全抵消，差模部分送入第二低噪放大器107的负输入端。
反馈电容Cfb连接在第二低噪放大器107的负输入端和输出之间，由于第二低噪放大器107的负反馈作用，感应极板201的电压保持不变，感应电容Cs和抵消电容Cc的电荷求和之后，转移到反馈电容Cfb上，得到输出电压VOUT。
复位开关SW连接在第二低噪放大器107的输入和输出之间，在复位阶段将输入和输出节点电压置为偏置电压VCM。
为进一步说明本发明实施例一的抵消模块10的抵消作用，下面列出相关参数的计算。
指纹到感应极板201的耦合电容与介质层和手指的按压情况均有关。如果手指与指纹感应电路的表面接触紧密，则耦合电容主要取决于介质层的介电常数、厚度以及感应极板201的面积。如果峰谷与指纹感应电路的接触不够紧密，则有与按压情况相关的空气介质电容部分。假设手指的峰对应的感应电容为Csr,谷对应的感应电容为Csv，两者的差值为ΔCs，即Csv＝Csr+ΔCs。
外接驱动源VS通过耦合信号通路耦合到感应极板201的电荷为：Vs*A1*Cs。
通过抵消信号通路耦合到感应电极201的电荷为：Vs*A2*Cc。
由于负反馈的存在，感应极板201电压保持不变，寄生电容Cg的电荷不变，不参与信号放大过程。
电荷在感应电容Cs、抵消电容Cc和反馈电容Cfb之间转移完成后，输出电压为：
Vout＝(VS*A1*Cs+VS*A2*Cc)/Cfb；
峰对应的输出电压为：Voutr＝(VS*A1*Csr+VS*A2*Cc)/Cfb；
谷对应的输出电压为：
Voutv＝(VS*A1*Csv+VS*A2*Cc)/Cfb＝(VS*A1*Csr+VS*A2*Cc)/Cfb+VS*A1*ΔCs/Cfb；
记录Voutc＝(VS*A1*Csr+VS*A2*Cc)/Cfb，为共模部分；Voutd＝VS*A1*ΔCs/Cfb，为差模部分。由于指纹信息只关心峰谷之间的灰度，因此通过调整A2，使得A2*Cc＝-A1*Csr(由此可知A1和A2的符号相反，即驱动放大器101和抵消放大器102的增益反相，进入抵消模块10的第一输入端和第二输入端的信号互为反相)，可衰减甚至消除Voutc，同时不减小Voutd。
假设采用的绝缘材料的相对介电常数为10，厚度为300um，手指与指纹感应电路的接触可假设为平板电容，单个像素点对应的面积为50um*50um，根据平板电容的计算公式，感应电容大小为：Cs≈0.74fF。
假设Csr＝1fF，Csv＝0.95fF，ΔCs＝-0.05fF，Cfb＝10fF,Cc＝10fF；VS＝1V，A1＝10。如果未经过抵消操作，第二低噪放大器107输出信 号的幅值为：Voutr＝Voutc＝1V，Voutv＝Voutc+Voutd＝950mV。如果电容指纹感应电路的后续放大器(与第二低噪放大器107的VOUT端相连)的工作电源为2V，共模点VCM＝1V，则增益设为1倍后输出信号幅度可达到0～2V，放大器出现饱和，有效信号即差模信号的幅度不能放大。
如果设定抵消放大器102的增益A2＝-1，将共模部分完整抵消，那么第二低噪放大器107输出信号的幅值为：Voutr＝Voutc＝0，Voutv＝Voutc+Voutd＝-50mV。电容指纹感应电路的后续放大器增益可设为足够大(如15倍)，而不出现饱和。有效信号即差模信号的幅度被放大了15倍，从而提高了纹路识别的灵敏度。
从上述分析过程可知，一个效果良好的抵消操作，改变A1/A2，满足条件：A1*Csr＝-A2*Cc。由于Csr与介质的材料和厚度有关，因此通过改变A2的大小，可适应不同的介质层。
如图5所示，上述实施例中的电荷放大器20也可用电流放大器代替，以完成相同的功能。电流放大器包括第一低噪放大器107以及连接在第一低噪放大器107的输入端和输出端之间的电阻Rfb，还可包括连接在第一低噪放大器107的输入端和输出端之间的复位开关SW。
综上所述，本发明实施例一的电容指纹感应电路，通过抵消操作，提高了指纹感应电路灵敏度的同时，方便进行后续放大，提高后续处理精度。进一步地，通过改变抵消放大器的增益，可适应不同厚度和材料的介质层，提高指纹传感器的兼容性。由于引入反馈放大器稳定 感应极板的电压，因此信号处理过程与感应电极的寄生电容无关，提高了系统可靠性。本发明实施例电路结构简洁，兼容标准CMOS工艺，集成成本低。
实施例二
为了达到足够的分辨率DPI(dots per inch)，电容指纹感应电路可用的面积较小，一个像素单元对应一个电容指纹感应电路，而驱动放大器和抵消放大器则可由多个像素单元共用。因此，本发明实施例二提出一种电容指纹感应器，如图6所示，本发明实施例二的电容指纹感应器包括多个像素单元，每个像素单元对应一个电容指纹感应电路。还包括驱动放大器401和抵消放大器402，驱动放大器401的输入端与外接驱动源VS连接，输出端通过按压在每一电容指纹感应电路的抵消模块40的第二输入端的手指连接，抵消放大器402的输入端与外接驱动源VS连接，输出端与每一电容指纹感应电路的抵消模块40的第一输入端连接，驱动放大器401和抵消放大器402的增益反相。
电容指纹感应电路的结构和工作原理与图2至图3所示的电容指纹感应电路类似，此处不再赘述。
电容指纹感应电路是电容式指纹感应器的基本单元，手指通过介质层将驱动信号耦合到感应电极301，同时驱动信号也通过内置的抵消电容Cc送入感应电极301，从而衰减或者消除与指纹无关的公共耦合信号，再放大剩余信号并输出到后续处理电路。
以上仅为本发明的较佳实施例而已，并不用以限制本发明，凡在 本发明的精神和原则之内所作的任何修改、等同替换和改进等，均应包含在本发明的保护范围之内。
工业实用性
本发明通过互为反相的外接驱动源和抵消模块衰减了与指纹无关的部分，仅放大与指纹深度相关的差模信号，因此后续级联的放大器不容易饱和，降低了指纹感应器的实现难度，提高了指纹感应器的灵敏度。进一步地，通过改变抵消放大器的增益，可适应不同厚度和材料的介质层，提高指纹传感器的兼容性。由于引入反馈放大器稳定感应极板的电压，因此信号处理过程与感应电极的寄生电容无关，提高了系统可靠性，本发明中的电容指纹感应电路结构简洁，兼容标准CMOS工艺，集成成本低。

Claims (10)

  1. 一种电容指纹感应电路，包括抵消模块和反馈放大器，所述抵消模块的第一输入端与第一外接驱动源连接，所述抵消模块的第二输入端通过按压在该第二输入端的手指与第二外接驱动源连接，所述抵消模块的输出端与所述反馈放大器的输入端连接，所述第一外接驱动源和所述第二外接驱动源输出的信号互为反相，所述第一外接驱动源送入到所述抵消模块的信号与所述第二外接驱动源耦合到所述抵消模块的信号产生抵消，得到与指纹深度相关的指纹感应信号，所述反馈放大器的输出端输出经放大后的指纹感应信号。
  2. 如权利要求1所述的电容指纹感应电路，其中，所述抵消模块包括感应电容(Cs)和抵消电容(Cc)，所述感应电容(Cs)的输入端为所述抵消模块的第二输入端，所述感应电容(Cs)的输出端与所述抵消电容(Cc)的输出端连接，所述抵消电容(Cc)的输入端为所述抵消模块的第一输入端，所述感应电容(Cs)和所述抵消电容(Cc)的连接点为所述抵消模块的输出端。
  3. 如权利要求2所述的电容指纹感应电路，其中，所述抵消模块的第二输入端包含感应极板，手指和所述感应极板之间通过介质层隔离，形成所述感应电容(Cs)，所述抵消模块的第一输入端包含抵消极板，所述感应极板和所述抵消极板之间形成所述抵消电容(Cc)。
  4. 如权利要求3所述的电容指纹感应电路，其中，所述感应极板和所述抵消极板均采用金属层构成。
  5. 如权利要求1所述的电容指纹感应电路，其中，所述反馈放大器为电流放大器，所述电流放大器包括第一低噪放大器以及连接在所述第一低噪放大器的输入端和输出端之间的电阻。
  6. 如权利要求1所述的电容指纹感应电路，其中，所述反馈放大器为电荷放大器，所述电荷放大器包括第二低噪放大器以及连接在所述第二低噪放大器的输入端和输出端之间的反馈电容。
  7. 如权利要求5或者6所述的电容指纹感应电路，其中，所述反馈放大器还包括连接在所述第一低噪放大器或者所述第二低噪放大器的输入端和输出端之间的复位开关。
  8. 如权利要求1至6中任一项所述的电容指纹感应电路，其中，还包括驱动放大器和抵消放大器，所述驱动放大器的输入端与外接驱动源连接，所述驱动放大器的输出端与按压在所述抵消模块第二输入端的手指连接；所述抵消放大器的输入端与所述外接驱动源连接，所述抵消放大器的输出端与所述抵消模块的第一输入端连接；所述驱动放大器和所述抵消放大器的增益反相。
  9. 一种电容指纹感应器，所述电容指纹感应器包括多个像素单元，每个像素单元对应一个电容指纹感应电路，所述电容指纹感应电路为权利要求1至8中任一项所述的电容指纹感应电路。
  10. 如权利要求9所述的电容指纹感应器，其中，还包括驱动放大器和抵消放大器，所述驱动放大器的输入端与外接驱动源连接，所述驱动放大器的输出端与按压在每一电容指纹感应电路的抵消模块的第二输入端的手指连接，所述抵消放大器的输入端与所述外接驱动源连接，所述抵消放大 器的输出端与每一电容指纹感应电路的抵消模块的第一输入端连接，所述驱动放大器和所述抵消放大器的增益反相。
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CN107368773A (zh) * 2016-05-12 2017-11-21 戴孟均 一种指纹传感器及应用其的智能设备
CN106293299B (zh) 2016-08-16 2018-01-12 北京集创北方科技股份有限公司 用于电容感应识别系统的装置和方法
EP3321849B1 (en) 2016-09-27 2020-07-22 Shenzhen Goodix Technology Co., Ltd. Fingerprint recognition system and electronic device
CN107092407B (zh) * 2017-04-12 2023-10-03 北京集创北方科技股份有限公司 感应电容测量装置
CN109308143A (zh) * 2017-07-26 2019-02-05 深圳指芯智能科技有限公司 一种电容感应器及其感应电路
CN108701226B (zh) 2017-11-07 2021-11-05 深圳市汇顶科技股份有限公司 指纹传感器和终端设备
US10650214B2 (en) * 2018-04-24 2020-05-12 Image Match Design Inc. Fingerprint sensor and method of fingerprint detection
CN110781868A (zh) * 2019-11-21 2020-02-11 上海思立微电子科技有限公司 像素电路、像素阵列、光学指纹传感器及指纹采集方法

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6636053B1 (en) * 2001-11-02 2003-10-21 Stmicroelectronics, Inc. Capacitive pixel for fingerprint sensor
US20040096061A1 (en) * 2001-07-12 2004-05-20 Motoyasu Yano Electrostatic capacitance sensor and fingerprint collator comprising it
US20090123039A1 (en) * 2007-11-13 2009-05-14 Upek, Inc. Pixel Sensing Circuit with Common Mode Cancellation

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4036798B2 (ja) * 2003-07-29 2008-01-23 アルプス電気株式会社 容量検出回路および検出方法並びに指紋センサ
JP4432625B2 (ja) * 2003-09-05 2010-03-17 セイコーエプソン株式会社 静電容量検出装置
CN1278270C (zh) * 2004-04-22 2006-10-04 芯微技术（深圳）有限公司 半导体指纹采集器件
JP4604087B2 (ja) * 2004-06-18 2010-12-22 フィンガープリント カーズ アーベー 指紋センサ素子
CN101858941A (zh) * 2010-03-30 2010-10-13 矽创电子股份有限公司 具抗电磁干扰能力的电容感测电路
JP5231605B2 (ja) * 2011-06-10 2013-07-10 シャープ株式会社 タッチパネルコントローラ、及びこれを用いた電子機器

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20040096061A1 (en) * 2001-07-12 2004-05-20 Motoyasu Yano Electrostatic capacitance sensor and fingerprint collator comprising it
US6636053B1 (en) * 2001-11-02 2003-10-21 Stmicroelectronics, Inc. Capacitive pixel for fingerprint sensor
US20090123039A1 (en) * 2007-11-13 2009-05-14 Upek, Inc. Pixel Sensing Circuit with Common Mode Cancellation

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2017058076A1 (en) * 2015-09-29 2017-04-06 Fingerprint Cards Ab Fingerprint sensing device with common mode suppression
CN108021843A (zh) * 2016-10-31 2018-05-11 深圳指瑞威科技有限公司 基于bcd工艺的高灵敏度指纹传感器
CN108469551A (zh) * 2018-05-25 2018-08-31 河北工业大学 一种多路微小电容信号采集处理电路
CN108469551B (zh) * 2018-05-25 2023-08-01 河北工业大学 一种多路微小电容信号采集处理电路
CN110265457A (zh) * 2019-06-27 2019-09-20 京东方科技集团股份有限公司 有机发光显示面板以及制备方法
CN111769828A (zh) * 2020-07-14 2020-10-13 成都芯思源科技有限公司 一种电容式触摸按键电路及电子设备
CN113467648A (zh) * 2021-07-01 2021-10-01 维沃移动通信有限公司 电子设备

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