WO2023160391A1 - 指纹检测放大电路以及指纹识别装置 - Google Patents

指纹检测放大电路以及指纹识别装置 Download PDF

Info

Publication number
WO2023160391A1
WO2023160391A1 PCT/CN2023/074960 CN2023074960W WO2023160391A1 WO 2023160391 A1 WO2023160391 A1 WO 2023160391A1 CN 2023074960 W CN2023074960 W CN 2023074960W WO 2023160391 A1 WO2023160391 A1 WO 2023160391A1
Authority
WO
WIPO (PCT)
Prior art keywords
voltage
signal
output terminal
fingerprint detection
auxiliary switch
Prior art date
Application number
PCT/CN2023/074960
Other languages
English (en)
French (fr)
Inventor
蒋新喜
程珍娟
孙天奇
张靖恺
Original Assignee
敦泰电子（深圳）有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 敦泰电子（深圳）有限公司 filed Critical 敦泰电子（深圳）有限公司
Publication of WO2023160391A1 publication Critical patent/WO2023160391A1/zh

Links

Classifications

    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
    • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
    • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
    • G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
    • G06K7/08—Methods or arrangements for sensing record carriers, e.g. for reading patterns by means detecting the change of an electrostatic or magnetic field, e.g. by detecting change of capacitance between electrodes
    • 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
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/45—Differential amplifiers

Definitions

  • the invention relates to a fingerprint detection amplifier circuit and a fingerprint identification device.
  • the capacitive fingerprint recognition solution is not affected by the light source, and the active unlocking experience is especially good.
  • the fingerprint information is judged by sensing the sensing capacitance formed by the valleys and ridges of the finger and the sensing electrodes.
  • the capacitance value of the sensing capacitor is amplified by the fingerprint detection amplifier circuit and then provided to an analog-to-digital converter (ADC) to be converted into a digital signal, and then restored to a fingerprint image through digital processing. Since the capacitance value of the sensing capacitor is usually very small, it is easily affected by the thickness of the cover plate.
  • ADC analog-to-digital converter
  • the noise signal and the sensing capacitor are input to the fingerprint detection amplifier circuit.
  • the single-ended input mode is adopted in the fingerprint detection amplifier circuit, so that the noise signal and the sensing capacitor are amplified at the same time, and the noise signal on the signal path cannot be effectively suppressed.
  • a fingerprint detection amplification circuit used to detect the capacitance value of the sensing capacitance formed between the sensing electrode and the finger and convert it into a voltage signal; the fingerprint detection amplification circuit includes:
  • a fully differential amplifier having a first input terminal, a second input terminal, a first output terminal and a second output terminal;
  • a switch group electrically connected between the sensing electrode and the fully differential amplifier, for controlling the first input terminal and the second input terminal to be electrically connected to the sensing electrode alternately;
  • the first feedback circuit is electrically connected to both ends of the first input terminal and the first output terminal, and is used to convert the capacitance value of the sensing capacitor input to the first input terminal into a voltage signal and perform Points;
  • the second feedback circuit is electrically connected to both ends of the second input terminal and the second output terminal, and is used to convert the capacitance value of the sensing capacitor input to the second input terminal into a voltage signal and perform integral;
  • the signals in the fingerprint detection amplifier circuit work in a specified voltage domain; the low-level signal in the specified voltage domain is a floating signal; the low-level signal can be between the first low voltage and the second low voltage switching; wherein, the first low voltage is greater than the second low voltage; when the low level signal is switched between the first low voltage and the second low voltage, the first output of the fully differential amplifier terminal and the second output terminal alternately output; the voltage at the first output terminal and the voltage at the second output terminal have a common-mode voltage.
  • a fingerprint recognition device comprising a fingerprint sensing circuit, a fingerprint detection amplification circuit, a digital-to-analog conversion circuit, and a data processing circuit;
  • the fingerprint detection amplification circuit is used to detect the capacitance value of a sensing capacitor formed between a sensing electrode and a finger Converted to a voltage signal;
  • the fingerprint detection amplification circuit includes:
  • a fully differential amplifier having a first input terminal, a second input terminal, a first output terminal and a second output terminal;
  • a switch group electrically connected between the sensing electrode and the fully differential amplifier, for controlling the first input terminal and the second input terminal to be electrically connected to the sensing electrode alternately;
  • the first feedback circuit is electrically connected to both ends of the first input terminal and the first output terminal, and is used to convert the capacitance value of the sensing capacitor input to the first input terminal into a voltage signal and perform Points;
  • the second feedback circuit is electrically connected to both ends of the second input terminal and the second output terminal, and is used to convert the capacitance value of the sensing capacitor input to the second input terminal into a voltage signal and perform integral;
  • the signals in the fingerprint detection amplifier circuit work in a specified voltage domain; the low-level signal in the specified voltage domain is a floating signal; the low-level signal can be between the first low voltage and the second low voltage switching; wherein, the first low voltage is greater than the second low voltage; when the low level signal is switched between the first low voltage and the second low voltage, the first output of the fully differential amplifier terminal and the second output terminal alternately output; the voltage at the first output terminal and the voltage at the second output terminal have a common-mode voltage.
  • the low-level signal in the specified voltage domain is a floating signal
  • the output signal of the full differential amplifier can be controlled on the rising and falling edges of the low-level signal, so as to Increasing the output gain of the fingerprint detection amplifier circuit can improve the common-mode noise suppression capability of the fingerprint detection amplifier circuit, effectively reduce noise, and further improve the signal-to-noise ratio of the fingerprint detection amplifier circuit.
  • FIG. 1 is a three-dimensional schematic diagram of a fingerprint recognition device according to a preferred embodiment of the present invention.
  • FIG. 2 is a schematic diagram of modules of the fingerprint recognition device in a preferred embodiment in FIG. 1 .
  • FIG. 3 is a block diagram of the fingerprint sensing circuit in a preferred implementation manner in FIG. 1 .
  • FIG. 4 is a schematic diagram of an equivalent circuit of the fingerprint detection amplifier circuit of the first embodiment in FIG. 2 .
  • FIG. 5 is a timing diagram of the reset signal, the precharge signal, the first sensing enable signal, the second sensing enable signal, the control signal and the low level signal in FIG. 4 .
  • FIG. 6 is a schematic diagram of voltage changes at the first output terminal and the second output terminal of the fully differential amplifier in FIG. 4 .
  • FIG. 7 is a schematic diagram of an equivalent circuit of the fingerprint detection amplifier circuit of the second embodiment in FIG. 2 .
  • FIG. 8 shows the reset signal, reverse reset signal, precharge signal, first sensing enable signal, A timing diagram of the second sensing enable signal, the control signal and the low level signal.
  • FIG. 9 is a schematic diagram of voltage changes at the first output terminal and the second output terminal of the fully differential amplifier in FIG. 7 .
  • Fingerprint identification device 100 Fingerprint Sensing Circuit 10 Fingerprint detection amplifier circuit 20, 20a, 20b Digital-to-analog conversion circuit 30 Data processing circuit 40 Sensing electrodes 12 High signal NVDDA Low signal NVSS Sensing Capacitance Cf
  • connection should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection ; It can be a mechanical connection, or an electrical connection, or can communicate with each other; it can be a direct connection, or an indirect connection through an intermediate connection, and it can be the internal communication of two components or the interaction relationship between two components.
  • connection should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection ; It can be a mechanical connection, or an electrical connection, or can communicate with each other; it can be a direct connection, or an indirect connection through an intermediate connection, and it can be the internal communication of two components or the interaction relationship between two components.
  • connection should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection ; It can be a mechanical connection, or an electrical connection, or can communicate with each other; it can be a direct connection, or an indirect connection through an intermediate
  • FIG. 1 is a schematic perspective view of a fingerprint recognition device 100 according to an embodiment of the present invention.
  • the fingerprint identification device 100 can be a personal computer, a tablet computer, a smart phone, a personal digital assistant (Personal Digital Assistant, PDA), a game machine, an interactive network television (Internet Protocol Television, Mobile devices such as IPTV), smart wearable devices, navigation devices, etc., can also be fixed devices such as desktop computers, servers, digital TVs, etc.
  • the fingerprint identification device 100 may further include a combination of one or more of a touch function, a display function, and a camera function.
  • the fingerprint identification device 100 includes a fingerprint sensing circuit 10 , a fingerprint detection amplifier circuit 20 , a digital-to-analog conversion circuit 30 and a data processing circuit 40 .
  • the fingerprint sensing circuit 10 is used to generate a sensing capacitance Cf (as shown in FIG. 4 ) when a user's fingerprint is detected.
  • the fingerprint detection amplifier circuit 20 is used for integrating and amplifying the capacitance value of the sensing capacitor Cf to output a sensing voltage to the digital-to-analog conversion circuit 30 .
  • the data processing circuit 40 processes the sensing voltage to convert it into a fingerprint image of the user.
  • the fingerprint sensing circuit 10 scans according to a certain timing control to detect the user's fingerprint to generate the sensing capacitance Cf.
  • the fingerprint sensing circuit 10 includes the sensing electrodes 12 arranged in an m*n matrix. Wherein, m and n are positive integers, and the two may be the same or different.
  • the sensing electrodes 12 in the touch area sense the finger to form a corresponding sensing capacitance Cf.
  • the sensing electrodes 12 are electrically connected to the fingerprint detection amplifier circuit 20 through sensing lines (not shown).
  • the fingerprint detection amplifier circuit 20 is electrically connected to the fingerprint sensing circuit 10 .
  • the fingerprint detection amplifying circuit 20 detects the capacitance of the sensing capacitor Cf and converts it into a voltage signal to perform an integration operation, then outputs the sensing voltage to the digital-to-analog conversion circuit 30, and then realizes the detection by the data processing circuit 40. detection of the capacitance value of the sensing capacitor Cf.
  • FIG. 4 is a schematic diagram of an equivalent circuit of the fingerprint detection amplifier circuit 20a according to the first embodiment of the present invention.
  • the signals in the fingerprint detection amplifier circuit 20a work in a specified voltage domain.
  • the specified voltage domain defines the voltage variation range of the fingerprint identification device 100
  • the specified voltage domain uses the high-level signal NVDDA as the upper limit voltage
  • the low-level signal NVSS as the lower limit voltage.
  • the high-level signal NVDDA can also be used as the working voltage of the fingerprint identification device 100
  • the low-level signal NVSS can also be used as the ground voltage.
  • the low-level signal NVSS is a floating signal.
  • the voltage of the low-level signal NVSS is a periodically changing pulse signal. Meanwhile, the voltage difference between the high-level signal NVDDA and the low-level signal NVSS remains unchanged.
  • the low level signal NVSS is switched under the control of the control signal TX.
  • the low level signal NVSS is switchable between a first low voltage and a second low voltage. Wherein, the first low voltage is greater than the second low voltage.
  • the low level signal NVSS and the control signal TX are complementary pulse signals.
  • the low-level signal NVSS and the control signal TX have the same pulse width and pulse frequency,
  • the control signal TX is at a high level
  • the low level signal NVSS is controlled to be at the second low voltage;
  • the control signal TX is at a low level
  • the low level signal NVSS is at the first low voltage.
  • the first low voltage may be 0 volts
  • the second low voltage may be a negative voltage, and the voltage value thereof may be set according to user requirements.
  • the fingerprint detection amplifier circuit 20a performs a charge transfer operation on the sensing capacitor Cf when the low-level signal NVSS is at the first low voltage and the second low voltage, and outputs first output signals VOUTP and The second output signal VOUTN.
  • the voltage variation directions of the first output signal VOUTP and the second output signal VOUTN are opposite.
  • the first output signal VOUTP is a decreasing signal
  • the second output signal VOUTN is an increasing signal.
  • the first output signal VOUTP and the second output signal VOUTN have a common mode voltage.
  • the common-mode voltage is the reference voltage VCM.
  • the fingerprint detection amplifier circuit 20a includes a fully differential amplifier 21, a switch group 23, a first feedback circuit 25a and a second feedback circuit 27a.
  • the fully differential amplifier 21 is electrically connected to the sensing electrode 12 through the switch group 23, and is used for sensing the sensing capacitor Cf through the switch group 23 and setting the capacitance value of the sensing capacitor Cf After being converted into the voltage signal, an integral operation is performed to realize amplification processing.
  • the switch group 23 includes a first switch K1 , a second switch K2_1 and a third switch K2_2 .
  • One end of the first switch K1 is electrically connected to the sensing electrode 12 , and the other end receives the reference voltage VCM.
  • the first switch K1 is controlled by a precharge signal PRE.
  • One end of the second switch K2_1 is electrically connected to the sensing electrode 12 , and the other end is electrically connected to the first input end 211 of the fully differential amplifier 21 .
  • the second switch K2_1 is controlled by the first sensing enable signal SENSOR_EN_P.
  • One end of the third switch K2_2 is electrically connected to the sensing electrode 12 , and the other end is electrically connected to the second input end 213 of the fully differential amplifier 21 .
  • the third switch K2_2 is controlled by the second sensing enable signal SENSOR_EN_N.
  • the fully differential amplifier 21 has the first input terminal 211 , the second input terminal 213 , the first output terminal 215 and the second output terminal 217 .
  • the first output terminal 215 serves as the output terminal of the first output signal VOUTP
  • the second output terminal 217 serves as the output terminal of the second output signal VOUTN.
  • the first input terminal 211 is an inverting input terminal
  • the second input terminal 213 is a forward input terminal
  • the first output terminal 215 is a forward output terminal
  • the second output terminal 217 is a reverse output terminal.
  • the common mode voltage is greater than the minimum value of the first output terminal 215 and less than the maximum value of the first output terminal 215; the common mode voltage is greater than the minimum value of the second output terminal 217 and less than the The maximum value of the second output terminal 217 is mentioned above.
  • the first feedback circuit 25 a is electrically connected to both ends of the first input terminal 211 and the first output terminal 215 .
  • the first feedback circuit 25a is used for converting the capacitance value of the sensing capacitor Cf input through the second switch K2_1 into the voltage signal to perform an integral operation.
  • the first feedback circuit 25a includes a first feedback capacitor CFB1 and a first main control switch K3_1. Both ends of the first feedback capacitor CFB1 are electrically connected to the first input end 211 and the first output end 215 respectively. Both ends of the first main control switch K3_1 are electrically connected to the first input end 211 and the first output end 215 respectively.
  • the first main control switch K3_1 is controlled by a reset signal RST.
  • the second feedback circuit 27 b is electrically connected to both ends of the second input end 213 and the second output end 217 .
  • the second feedback circuit 27a is used for converting the capacitance value of the sensing capacitor Cf input through the third switch K2_2 into the voltage signal to perform an integral operation.
  • the second feedback circuit 27a includes a second feedback capacitor CFB2 and a second main control switch K3_2. Both ends of the second feedback capacitor CFB2 are electrically connected to the second input end 213 and the second output end 217 respectively. Both ends of the second main control switch K3_2 are electrically connected to the second input end 213 and the second output end 217 respectively.
  • the second main control switch K3_2 is controlled by the reset signal RST. In this implementation manner, the second feedback capacitor CFB2 and the first feedback capacitor CFB1 have the same capacitance value.
  • FIG. 5 shows the reset signal RST, the precharge signal PRE, the first sensing enable signal SENSOR_EN_P, the second sensing enabling signal SENSOR_EN_N, the control signal TX and the low power Timing diagram of flat signal NVSS.
  • the specific working principle of the fingerprint detection amplification circuit 20a is as follows:
  • the fingerprint detection amplifier circuit 20a can work in the reset phase T1, the pre-charge phase T2, the first charge transfer phase T3 and the second charge transfer phase T4. Wherein, the fingerprint detection amplifier circuit 20 first works sequentially in the reset phase T1 and the pre-charge phase T2, and then the fingerprint detection amplifier circuit 20a alternately works in the first charge transfer phase T3 and the second charge transfer phase T3 Transfer stage T4. In this embodiment, there is a preset time interval between the reset phase T1 and the pre-charge phase T2. During the preset time interval, the fingerprint detection amplifier circuit 20a does not perform any operation.
  • the precharge signal PRE, the first sensing enable signal SENSOR_EN_P, the second sensing enable signal SENSOR_EN_N, and the control signal TX are at a low level, and the reset The signal RST is set at a high level, and the low level signal NVSS is at the first low voltage.
  • the first switch K1 is turned off.
  • the second switch K2_1 is turned off.
  • the third switch K2_2 is turned off.
  • Q CFB1 represents the charge on the first feedback capacitor CFB1
  • Q CFB2 represents the charge on the second feedback capacitor CFB2.
  • the reset signal RST, the first sensing enable signal SENSOR_EN_P, the second sensing enabling signal SENSOR_EN_N, and the control signal TX are at low level, and the pre-charging The charge signal PRE is at a high level, and the low level signal NVSS is at the first low voltage.
  • the first switch K1 is closed, so that the reference voltage VCM performs a precharge operation on the sensing capacitor Cf.
  • the total charge in the fingerprint detection amplifier circuit 20b is the charge on the sensing capacitor Cf.
  • the charge on the sensing capacitor Cf can be calculated by formula one.
  • Q cf VCM*C f Formula 1
  • Q CF represents the charge on the sensing capacitor Cf during the pre-charging phase T2
  • VCM represents the reference voltage VCM
  • Cf represents the capacitance of the sensing capacitor Cf.
  • the second switch K2_1 under the control of the first sensing enable signal SENSOR_EN_P, the second switch K2_1 is turned off. Under the control of the second sensing enable signal SENSOR_EN_N, the third switch K2_2 is turned off. Under the control of the reset signal RST, the first main control switch K3_1 and the second main control switch K3_2 are turned off.
  • the reset signal RST, the precharge signal PRE and the second sensing enable signal SENSOR_EN_N are at low level, and the first sensing enable signal SENSOR_EN_P is at high level, the control signal TX is switched from low level to high level, and the low level signal NVSS is switched from the first low voltage to the second low voltage.
  • the charge on the sensing capacitor Cf is transferred to the first feedback capacitor CFB1 in the first feedback circuit 25a to charge the first input terminal 211 of the fully differential amplifier 21 to realize the integration once. operate.
  • the total charge of the fingerprint detection amplifier circuit 20a is composed of the charge on the sensing capacitor Cf and the charge on the first feedback capacitor CFB1. That is, the total charge in the fingerprint detection amplifier circuit 20a can be calculated by Formula 2.
  • Q cf1 represents the total charge of the sensing capacitor Cf before the charge transfer in the first charge transfer stage T3
  • VCM represents the reference voltage
  • V OUTP represents the voltage of the first output terminal 215
  • C FB1 represents the capacitance value of the first feedback capacitor CFB1
  • NVDDA represents the system power supply voltage
  • Cf represents the capacitance value of the sensing capacitor Cf.
  • the voltage difference between the two ends of the first feedback capacitor CFB1 is the voltage difference between the reference voltage VCM and the first output terminal 215 .
  • the voltage at the end of the sensing capacitor Cf electrically connected to the first input terminal 211 changes to the reference voltage VCM and the sum of the second low voltages.
  • V OUTP represents the voltage of the first output terminal 215
  • VCM represents the reference voltage
  • C f represents the capacitance value of the sensing capacitor Cf
  • C FB1 represents the capacitance value of the first feedback capacitor CFB1
  • NVDDA Indicates the system supply voltage.
  • the reset signal RST, the precharge signal PRE and the first sensing enable signal SENSOR_EN_P are at low level, and the second sensing enable signal SENSOR_EN_N is at high level, the control signal TX is switched from high level to low level, and the low level signal NVSS is switched from the second low voltage to the first low voltage.
  • the total charge of the fingerprint detection amplifier circuit 20a is composed of the charge on the sensing capacitor Cf and the charge on the first feedback capacitor CFB1. That is, the total charge in the fingerprint detection amplifier circuit 20a can be calculated by Formula 4.
  • Q cf2 represents the total charge of the sensing capacitor Cf before the charge transfer in the second charge transfer stage T4
  • VCM represents the reference voltage VCM
  • NVDDA represents the system power supply voltage
  • Cf represents the sensing capacitor Cf.
  • the capacitance value of the capacitor Cf, V OUTN represents the voltage of the second output terminal 217
  • C FB2 represents the capacitance value of the second feedback capacitor CFB2 .
  • the voltage difference between the two ends of the second feedback capacitor CFB2 is the voltage difference between the reference voltage VCM and the second output terminal 217 .
  • the low-level signal NVSS is switched to the first low voltage
  • the voltage at the end of the sensing capacitor Cf electrically connected to the first input end 211 changes to the reference voltage VCM.
  • V OUTN represents the voltage of the second output terminal 217
  • VCM represents the reference voltage
  • C f represents the capacitance value of the sensing capacitor Cf
  • C FB2 represents the capacitance value of the second feedback capacitor CFB2
  • NVDDA Indicates the system supply voltage.
  • the difference between the first output terminal 215 and the second output terminal 217 can be expressed as the following formula 6.
  • the low-level signal NVSS in the specified voltage domain is a floating signal, and the rising and falling edges of the low-level signal NVSS can control the
  • the output signal of the fully differential amplifier 21 is used to increase the output gain of the fingerprint detection amplifier circuit 20a. That is, compared with the conventional differential amplifier with the same number of integration operations, the gain of the output signal using the fully differential amplifier 21 is doubled.
  • the common-mode noise suppression capability of the fingerprint detection amplifier circuit 20a can be improved, noise can be effectively reduced, and the signal-to-noise ratio of the fingerprint detection amplifier circuit 20a can be improved.
  • FIG. 7 is a schematic diagram of an equivalent circuit of the fingerprint detection amplifier circuit 20 b according to the second embodiment of the present invention.
  • the signals in the fingerprint detection amplifier circuit 20b work in a specified voltage domain.
  • the specified voltage domain defines the voltage variation range of the fingerprint identification device 100
  • the specified voltage domain uses the high-level signal NVDDA as the upper limit voltage
  • the low-level signal NVSS as the lower limit voltage.
  • the high-level signal NVDDA can also be used as the working voltage of the fingerprint identification device 100
  • the low-level signal NVSS can also be used as the ground voltage.
  • the low-level signal NVSS is a floating signal.
  • the voltage of the low-level signal NVSS is a periodically changing pulse signal. Meanwhile, the voltage difference between the high-level signal NVDDA and the low-level signal NVSS remains unchanged.
  • the low level signal NVSS is switched under the control of the control signal TX.
  • the low level signal NVSS is switchable between a first low voltage and a second low voltage. Wherein, the first low voltage is greater than the second low voltage.
  • the low level signal NVSS and the control signal are complementary pulse signals.
  • the low-level signal NVSS and the control signal TX have the same pulse width and pulse frequency, and when the control signal TX is at a high level, the low-level signal NVSS is controlled to be at the second Low voltage: when the control signal TX is at low level, the low level signal NVSS is at the first low voltage.
  • the first low voltage may be 0 volts
  • the second low voltage may be a negative voltage
  • the voltage value thereof may be set according to user requirements.
  • the fingerprint detection amplifier circuit 20b is based on the rising and falling edges of the low-level signal NVSS After converting the sensing capacitor Cf into a voltage signal, two integration operations are performed and a fully differential circuit is used to generate a first output signal VOUTP and a second output signal VOUTN.
  • the voltage variation directions of the first output signal VOUTP and the second output signal VOUTN are opposite.
  • the first output signal VOUTP is a decreasing signal
  • the second output signal VOUTN is an increasing signal.
  • the first output signal VOUTP and the second output signal VOUTN have the same initial voltage.
  • the starting voltage is the reference voltage VCM.
  • the fingerprint detection amplifier circuit 20b includes a fully differential amplifier 21, a switch group 23, a first feedback circuit 25b and a second feedback circuit 27b.
  • the fully differential amplifier 21 is electrically connected to the sensing electrode 12 through the switch group 23, and is used for sensing the sensing capacitor Cf through the switch group 23 and setting the capacitance value of the sensing capacitor Cf Integral processing is carried out after being converted into a voltage signal to realize amplification processing.
  • the switch group 23 includes a first switch K1 , a second switch K2_1 and a third switch K2_2 .
  • One end of the first switch K1 is electrically connected to the sensing electrode 12 , and the other end receives the reference voltage VCM.
  • the first switch K1 is controlled by a precharge signal PRE.
  • One end of the second switch K2_1 is electrically connected to the sensing electrode 12 , and the other end is electrically connected to the first input end 211 of the fully differential amplifier 21 .
  • the second switch K2_1 is controlled by the first sensing enable signal SENSOR_EN_P.
  • One end of the third switch K2_2 is electrically connected to the sensing electrode 12 , and the other end is electrically connected to the second input end 213 of the fully differential amplifier 21 .
  • the third switch K2_2 is controlled by the second sensing enable signal SENSOR_EN_N.
  • the fully differential amplifier 21 has the first input terminal 211 , the second input terminal 213 , the first output terminal 215 and the second output terminal 217 .
  • the first output terminal 215 serves as the output terminal of the first output signal VOUTP
  • the second output terminal 217 serves as the output terminal of the second output signal VOUTN.
  • the first input terminal 211 is an inverting input terminal
  • the second input terminal 213 is a forward input terminal
  • the first output terminal 215 is a forward output terminal
  • the second output terminal 213 is a reverse output terminal.
  • the first output terminal 215 and the second output terminal 217 of the fully differential amplifier 21 output alternately.
  • the first feedback circuit 25 b is electrically connected to both ends of the first input terminal 211 and the first output terminal 215 .
  • the first feedback circuit 25b is used for converting the capacitance value of the sensing capacitor Cf input through the second switch K2_1 into a voltage signal to perform an integral operation.
  • the first feedback circuit 25b includes a first feedback capacitor CFB1, a first main control switch K3_1, a first auxiliary switch K4_1, a second auxiliary switch K5_1, a third auxiliary switch K6_1 and a fourth auxiliary switch K7_1. Both ends of the first main control switch K3_1 are electrically connected to the first input end 211 of the fully differential amplifier 21 and the first output end 215 respectively.
  • One end of the first feedback capacitor CFB1 is electrically connected to the first input end 211 of the fully differential amplifier 21 through the first auxiliary switch K4_1, and receives the low-level signal through the third auxiliary switch K6_1 NVSS; the other end of the first feedback capacitor CFB1 is electrically connected to the first output end 215 of the fully differential amplifier 21 through the second auxiliary switch K5_1, and receives the power supply voltage VDC_OS through the fourth auxiliary switch K7_1 .
  • the first main control switch K3_1 , the third auxiliary switch K6_1 and the fourth auxiliary switch K7_1 are controlled by a reset signal RST.
  • the first auxiliary switch K4_1 and the second auxiliary switch K5_1 are controlled by a reverse reset signal NRST.
  • the reset signal RST and the reverse reset signal NRST are complementary pulse signals.
  • the reset signal RST and the reverse reset signal NRST have the same pulse width and pulse frequency, and when the reset signal RST is at a high level, the reverse reset signal NRST is at The low level; when the reset signal RST is at low level, the reverse reset signal NRST is at high level.
  • the second feedback circuit 27 b is electrically connected to both ends of the second input end 213 and the second output end 217 .
  • the second feedback circuit 27b is used for converting the capacitance value of the sensing capacitor Cf input through the third switch K2_2 into a voltage signal to perform an integral operation.
  • the second feedback circuit 27b includes a second feedback capacitor CFB2, a second main control switch K3_2, a fifth auxiliary switch K4_2, a sixth auxiliary switch K5_2, a seventh auxiliary switch K6_2 and an eighth auxiliary switch K7_2. Both ends of the second main control switch K3_2 are electrically connected to the second input end 213 and the second output end 217 of the fully differential amplifier 21 respectively.
  • One end of the second feedback capacitor CFB2 is electrically connected to the second input end 213 of the fully differential amplifier 21 through the fifth auxiliary switch K4_2, and receives the low-level signal through the seventh auxiliary switch K6_2 NVSS: the other end of the second feedback capacitor CFB2 is electrically connected to the second output end 217 of the fully differential amplifier 21 through the sixth auxiliary switch K5_2, and receives the power through the eighth auxiliary switch K7_2 Voltage VDC_OS.
  • the second main control switch K3_2 , the seventh auxiliary switch K6_2 and the eighth auxiliary switch K7_2 are controlled by a reset signal RST.
  • the fifth auxiliary switch K4_2 and the sixth auxiliary switch K5_2 are controlled by the reverse reset signal NRST. In this implementation manner, the second feedback capacitor CFB2 and the first feedback capacitor CFB1 have the same capacitance value.
  • FIG. 8 shows the reset signal RST, reverse reset signal NRST, precharge signal PRE, first sensing enable signal SENSOR_EN_P, second sensing enabling signal SENSOR_EN_N, control Schematic diagram of the timing of the signal TX and the low-level signal NVSS.
  • the specific working principle of the fingerprint detection amplification circuit 20b is as follows:
  • the fingerprint detection amplifier circuit 20b can work in the reset phase T1, the pre-charge phase T2, the first charge transfer phase T3 and the second charge transfer phase T4. Wherein, after the reset phase T1 and the pre-charge phase T2, the fingerprint detection amplifier circuit 20b alternately works in the first charge transfer phase T3 and the second charge transfer phase T4. In this embodiment, there is a preset time interval between the reset phase T1 and the pre-charge phase. During the preset time interval, the fingerprint detection amplifier circuit 20b does not perform any operation.
  • the reverse reset signal NRST, the precharge signal PRE, the first sense enable signal SENSOR_EN_P, the second sense enable signal SENSOR_EN_N and the control signal TX is at low level
  • the reset signal RST is at high level
  • the low level signal NVSS is at the first low voltage.
  • the first switch K1 is turned off.
  • the second switch K2_1 is turned off.
  • the third switch K2_2 is turned off.
  • the first main control switch K3_1, the third auxiliary switch K6_1 and the fourth auxiliary switch K7_1 in the first feedback circuit 25a are closed, and at the same time, the first The second main control switch K3_2, the seventh auxiliary switch K6_2 and the eighth auxiliary switch K7_2 in the second feedback circuit 27b are closed.
  • the first auxiliary switch K4_1 and the second auxiliary switch K5_1 of the first feedback circuit 25a are turned off, and at the same time, the The fifth auxiliary switch K4_2 and the sixth auxiliary switch K5_2 are turned off.
  • the charge at both ends of the first feedback capacitor CFB1 is calculated by formula 8.
  • Q CFB1 C FB1 *(NVSS-VDC_OS) Formula 8
  • Q CFB1 represents the charge on the first feedback capacitor CFB1 in the reset phase T1
  • C FB1 represents the capacitance value of the first feedback capacitor CFB1
  • NVSS represents the low-level signal NVSS
  • VDC_OS represents The supply voltage VDC_OS.
  • the reset signal RST, the first sensing enable signal SENSOR_EN_P, the second sensing enabling signal SENSOR_EN_N and the control signal TX are at low level
  • the pre-charging The signal PRE and the reverse reset signal NRST are at a high level
  • the low level signal NVSS is at the first low voltage.
  • the first switch K1 is closed, so that the reference voltage VCM performs a precharge operation on the sensing capacitor Cf.
  • the charge of the sensing capacitor Cf can be calculated by the above formula 1.
  • the second switch K2_1 under the control of the first sensing enable signal SENSOR_EN_P, the second switch K2_1 is turned off. Under the control of the second sensing enable signal SENSOR_EN_N, the third switch K2_2 is turned off. Under the control of the reset signal RST, the first main control switch K3_1, the third auxiliary switch K6_1 and the fourth auxiliary switch K7_1 in the first feedback circuit 25a are turned off, and the The second main control switch K3_2, the seventh auxiliary switch K6_2 and the eighth auxiliary switch K7_2 in the second feedback circuit 27b are turned off.
  • the first auxiliary switch K4_1 and the second auxiliary switch K5_1 of the first feedback circuit 25a are closed, and at the same time, all the auxiliary switches in the second feedback circuit 27b
  • the fifth auxiliary switch K4_2 and the sixth auxiliary switch K5_2 are closed. Since the first feedback capacitor CFB1 and the second feedback capacitor CFB2 have no discharge loop, the charges on the first feedback capacitor CFB1 and the second feedback capacitor CFB2 remain unchanged.
  • the reset signal RST, the precharge signal PRE and the second sensing enable signal SENSOR_EN_N are at low level, and the first sensing enable signal SENSOR_EN_P and The reverse reset signal NRST is at high level, the control signal TX is switched from low level to high level, and the low level signal NVSS is switched from the first low voltage to the second low voltage .
  • the charge on the sensing capacitor Cf is transferred to the first feedback capacitor CFB1 in the first feedback circuit 25b to charge the first input terminal 211 of the fully differential amplifier 21 to realize the integration once. operate.
  • the total charge of the fingerprint detection amplifier circuit 20b is composed of the charge on the sensing capacitor Cf and the charge on the first feedback capacitor CFB1.
  • the total charge in the fingerprint detection amplifier circuit 20b can be calculated by Formula 10.
  • Q cf1 represents the total charge on the fingerprint detection amplifier circuit 20b and the first input terminal 211 before the charge transfer in the first charge transfer stage T3
  • VCM represents the reference voltage VCM
  • Cf represents the The capacitance value of the sensing capacitor Cf
  • C FB1 represents the capacitance value of the first feedback capacitor CFB1
  • NVSS represents the low level signal NVSS
  • VDC_OS represents the power supply voltage VDC_OS
  • V OUTP represents the first output terminal 215
  • the voltage, NVDDA represents the system supply voltage.
  • the voltage difference between the two ends of the first feedback capacitor CFB1 is the voltage difference between the reference voltage VCM and the first output terminal 215 .
  • the voltage at the end of the sensing capacitor Cf electrically connected to the first input terminal 211 changes to the reference voltage VCM and the sum of the second low voltages.
  • V OUTP represents the voltage of the first output terminal 215
  • VCM represents the reference voltage
  • VDC_OS represents the power supply voltage
  • C f represents the capacitance value of the sensing capacitor Cf
  • C FB2 represents the second feedback
  • NVDDA represents the system power supply voltage.
  • the reset signal RST, the precharge signal PRE and the first sensing enable signal SENSOR_EN_P are at low level, and the second sensing enable signal SENSOR_EN_N is at high level
  • the control signal TX is switched from high level to low level
  • the low level signal NVSS is switched from the second low voltage to the first low voltage.
  • the total charge of the fingerprint detection amplifier circuit 20b is composed of the charge on the sensing capacitor Cf and the charge on the first feedback capacitor CFB1.
  • the total charge in the fingerprint detection amplifier circuit 20b can be calculated by Formula 12.
  • Q cf1 represents the total charge of the sensing capacitor Cf before the charge transfer in the second charge transfer stage T4
  • VCM represents the reference voltage VCM
  • C f represents the capacitance value of the sensing capacitor Cf
  • C FB2 represents the capacitance value of the second feedback capacitor CFB2
  • NVSS represents the low-level signal NVSS
  • VDC_OS represents the power supply voltage VDC_OS
  • V OUTP represents the voltage of the first output terminal 215
  • NVDDA represents the system power supply Voltage.
  • the voltage difference between the two ends of the second feedback capacitor CFB2 is the voltage difference between the reference voltage VCM and the second output terminal 217 .
  • the low-level signal NVSS is switched to the first low voltage
  • the voltage at the end of the sensing capacitor Cf electrically connected to the first input end 211 changes to the reference voltage VCM.
  • V OUTN represents the voltage of the second output terminal 217
  • VCM represents the reference voltage
  • VDC_OS represents the power supply voltage
  • C f represents the capacitance value of the sensing capacitor Cf
  • C FB2 represents the second The capacitance value of the feedback capacitor CFB2
  • NVDDA represents the system power supply voltage
  • the difference between the first output terminal 215 and the second output terminal 217 can be expressed as the following formula 15.
  • the first output signal VOUTP shows a decreasing linear change between the first preset value and the second preset value
  • the second output signal VOUTN There is an increasing linear change between the third preset value and the fourth preset value.
  • the first preset value is greater than the second preset value
  • the third preset value is smaller than the fourth preset value.
  • the first preset value and the fourth preset value may be equal, and the second preset value may be equal to the third preset value.
  • the low-level signal NVSS in the specified voltage domain is a floating signal, and the rising and falling edges of the low-level signal NVSS can control the
  • the output signal of the fully differential amplifier 21 is used to increase the output gain of the fingerprint detection amplifier circuit 20b. That is, compared with the conventional differential amplifier with the same number of integration operations, the gain of the output signal using the fully differential amplifier 21 is doubled.
  • the common-mode noise suppression capability of the fingerprint detection amplifier circuit 20b can be improved, noise can be effectively reduced, and the signal-to-noise ratio of the fingerprint detection amplifier circuit 20b can be improved.
  • the first output terminal 215 can be reduced from the highest value, and the second output terminal The voltage of 217 can be changed gradually from the lowest value to make full use of the dynamic voltage range of the fingerprint detection amplifier circuit 20b.

Landscapes

  • Engineering & Computer Science (AREA)
  • Theoretical Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Human Computer Interaction (AREA)
  • General Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Computer Vision & Pattern Recognition (AREA)
  • Artificial Intelligence (AREA)
  • Multimedia (AREA)
  • Image Input (AREA)
  • Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
  • Measurement Of The Respiration, Hearing Ability, Form, And Blood Characteristics Of Living Organisms (AREA)
  • Collating Specific Patterns (AREA)
  • Testing Of Coins (AREA)
  • Control Of Vending Devices And Auxiliary Devices For Vending Devices (AREA)

Abstract

提供一种指纹检测放大电路（20a）和指纹识别装置。指纹检测放大电路（20a）包括全差分放大器（21）、开关组（23）、第一反馈电路（25a）及第二反馈电路（27a）。开关组控制全差分放大器的第一输入端（211）与第二输入端（213）交替与感测电极电性连接。第一反馈电路（25a）对输入至第一输入端（211）的感测电容的电容值转换为电压信号。第二反馈电路（27a）对输入至第二输入端（213）的感测电容的电容值转换为电压信号。指纹检测放大电路内的信号工作在指定电压域。在指定电压域中的低电平信号为浮动信号。低电平信号在第一低电压和第二低电压之间切换。低电平信号在第一低电压和第二低电压之间切换时，全差分放大器的第一输出端（VOUTP）和第二输出端（VOUTN）交替输出；第一输出端（VOUTP）的电压和第二输出端（VOUTN）的电压具有共模电压。

Description

指纹检测放大电路以及指纹识别装置 技术领域
本发明涉及一种指纹检测放大电路以及指纹识别装置。
背景技术
随着智能手机全面屏普及，指纹采集与识别方案趋于光学式屏下指纹识别和电容式指纹识别两种方案。其中，电容式式指纹识别方案不受光源影响，主动解锁的体验尤佳。现有的指纹采集与识别方案中，通过感应手指的谷和脊与感应电极的形成的感应电容，而判断指纹信息。感应电容的电容值通过指纹检测放大电路进行放大处理后提供给模数转换器(Analog to digital converter,ADC)转换为数字信号，通过数字处理恢复为指纹图像。由于感应电容的电容值通常非常小，且容易受到盖板厚度影响。同时，存在噪声信号与感应电容一并输入给指纹检测放大电路。通常指纹检测放大电路中采用单端输入的模式，使得噪声信号与感应电容同时被放大，进而导致信号通路上的噪音信号无法被有效抑制。
发明内容
有鉴于此，有必要提供一种指纹检测放大电路以及指纹识别装置，旨在解决现有技术中单端输入的指纹检测放大电路无法有效抑制噪音信号的技术问题。
一种指纹检测放大电路，用于检测感测电极与手指之间形成的感测电容的电容值转换为电压信号；所述指纹检测放大电路包括：
全差分放大器，具有第一输入端、第二输入端、第一输出端以及第二输出端；
开关组，电性连接在所述感测电极和所述全差分放大器之间，用于控制所述第一输入端与所述第二输入端交替与所述感测电极电性连接；
第一反馈电路，与所述第一输入端和所述第一输出端的两端电性连接，用于对输入至所述第一输入端的所述感测电容的电容值转换为电压信号后进行积分；以及
第二反馈电路，与所述第二输入端和所述第二输出端的两端电性连接，用于对输入至所述第二输入端的所述感测电容的电容值转换为电压信号后进行积分；
所述指纹检测放大电路内的信号工作在指定电压域；在所述指定电压域中的低电平信号为浮动信号；所述低电平信号可在第一低电压和第二低电压之间 切换；其中，所述第一低电压大于第二低电压；所述低电平信号在所述第一低电压和所述第二低电压之间切换时，所述全差分放大器的第一输出端和所述第二输出端交替输出；所述第一输出端的电压和所述第二输出端的电压具有共模电压。
一种指纹识别装置，包括指纹感测电路、指纹检测放大电路、数模转换电路以及数据处理电路；所述指纹检测放大电路用于检测感测电极与手指之间形成的感测电容的电容值转换为电压信号；所述指纹检测放大电路包括：
全差分放大器，具有第一输入端、第二输入端、第一输出端以及第二输出端；
开关组，电性连接在所述感测电极和所述全差分放大器之间，用于控制所述第一输入端与所述第二输入端交替与所述感测电极电性连接；
第一反馈电路，与所述第一输入端和所述第一输出端的两端电性连接，用于对输入至所述第一输入端的所述感测电容的电容值转换为电压信号后进行积分；以及
第二反馈电路，与所述第二输入端和所述第二输出端的两端电性连接，用于对输入至所述第二输入端的所述感测电容的电容值转换为电压信号后进行积分；
所述指纹检测放大电路内的信号工作在指定电压域；在所述指定电压域中的低电平信号为浮动信号；所述低电平信号可在第一低电压和第二低电压之间切换；其中，所述第一低电压大于第二低电压；所述低电平信号在所述第一低电压和所述第二低电压之间切换时，所述全差分放大器的第一输出端和所述第二输出端交替输出；所述第一输出端的电压和所述第二输出端的电压具有共模电压。
上述指纹检测放大电路以及指纹识别装置，所述指定电压域的所述低电平信号为浮动信号，在所述低电平信号的上升沿和下降沿可控制所述全差分放大器输出信号，以提高所述指纹检测放大电路的输出增益，可提高所述指纹检测放大电路的共模噪声抑制能力，可有效降低噪音，进而提高所述指纹检测放大电路的信噪比。
附图说明
图1为本发明较佳实施例之指纹识别装置的立体示意图。
图2为图1中较佳实施方式之所述指纹识别装置的模块示意图。
图3为图1中较佳实施方式之所述指纹感测电路的模块示意图。
图4为图2中第一实施方式之所述指纹检测放大电路的等效电路示意图。
图5为图4中重置信号、预充电信号、第一感测使能信号、第二感测使能信号、控制信号以及低电平信号的时序示意图。
图6为图4中所述全差分放大器的第一输出端和第二输出端的电压变化示意图。
图7为图2中第二实施方式之所述指纹检测放大电路的等效电路示意图。
图8为图7中重置信号、反向重置信号、预充电信号、第一感测使能信号、 第二感测使能信号、控制信号以及低电平信号的时序示意图。
图9为图7中所述全差分放大器的第一输出端和第二输出端的电压变化示意图。
主要元件符号说明
指纹识别装置                     100
指纹感测电路                     10
指纹检测放大电路                 20、20a、20b
数模转换电路                     30
数据处理电路                     40
感测电极                         12
高电平信号                       NVDDA
低电平信号                       NVSS
感测电容                         Cf
第一输出信号                     VOUTP
第二输出信号                     VOUTN
参考电压                         VCM
差分放大器                       21
开关组                           23
第一反馈电路                     25a、25b
第二反馈电路                     27a、27b
第一开关                         K1
第二开关                         K2_1
第三开关                         K2_2
第一反馈电容                     CFB1
第二反馈电容                     CFB2
第一主控制开关                   K3_1
第二主控制开关                   K3_2
重置信号                         RST
反向重置信号                     NRST
预充电信号                     PRE
第一感测使能信号                  SENSOR_EN_P
第二感测使能信号                  SENSOR_EN_N
控制信号                          TX
重置阶段                          T1
预充电阶段                        T2
第一电荷转移阶段                  T3
第二电荷转移阶段                  T4
第一辅助开关                      K4_1
第二辅助开关                      K5_1
第三辅助开关                      K6_1
第四辅助开关                      K7_1
第五辅助开关                      K4_2
第六辅助开关                      K5_2
第七辅助开关                      K6_2
第八辅助开关                      K7_2
电源电压                          VDC_OS
如下具体实施方式将结合上述附图进一步说明本发明。
具体实施方式
为了使本技术领域的人员更好地理解本发明方案，下面将结合本发明实施例中的附图，对本发明实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅仅是本发明一部分的实施例，而不是全部的实施例。基于本发明中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都应当属于本发明保护的范围。
在本发明的实施方式的描述中，需要说明的是，除非另有明确的规定和限定，术语“连接”应做广义理解，例如，可以是固定连接，也可以是拆卸连接，或一体地连接；可以是机械连接，也可以是电连接或可以相互通讯；可以是直接连接，也可以通过中间没接间接连接，可以是两个元件内部的连通或两个元件的相互作用关系。对于本领域的普通技术人员而言，可以根据具体情况立即上述术语在本发明中的具体含义。
本发明的说明书及上述附图中的术语“第一”、“第二”和“第三”等是用于区别不同对象，而非用于描述特定顺序。此外，术语“包括”以及它们任何 变形，意图在于覆盖不排他的包含。
除非另有定义，本文所使用的所有的技术和科学术语与属于本发明的技术领域的技术人员通常理解的含义相同。本文中在本发明的说明书中所使用的术语只是为了描述具体的实施例的目的，不是旨在于限制本发明。
下面结合附图对本发明的指纹检测放大电路以及指纹识别装置的具体实施方式进行说明。
请参照图1，其为本发明一实施方式的指纹识别装置100的立体示意图。在本发明的至少一个实施方式中，所述指纹识别装置100可以为个人计算机、平板电脑、智能手机、个人数字助理(Personal Digital Assistant，PDA)、游戏机、交互式网络电视(Internet Protocol Television,IPTV)、智能式穿戴式设备、导航装置等等的可移动设备，也可以为台式电脑、服务器、数字电视等等的固定设备。所述指纹识别装置100可进一步包括触控功能、显示功能以及摄像功能中的一种或多种的结合。
请一并参阅图2，其为所述指纹识别装置100的模块示意图。所述指纹识别装置100包括指纹感测电路10、指纹检测放大电路20、数模转换电路30以及数据处理电路40。所述指纹感测电路10用于在检测到用户的指纹时产生感测电容Cf(如图4所示)。所述指纹检测放大电路20用于对所述感测电容Cf的电容值进行积分放大后输出感测电压给所述数模转换电路30。所述数据处理电路40对所述感测电压进行处理以转换成用户的指纹图像。
所述指纹感测电路10按照一定的时序控制进行扫描以检测用户的指纹以产生所述感测电容Cf。如图3所示，所述指纹感测电路10包括呈m*n矩阵排列的所述感测电极12。其中，m，n为正整数，且二者可以相同也可以不同。用户手指触摸后，触摸区域的所述感测电极12与手指进行感应，以形成对应的感测电容Cf。所述感测电极12通过感测线(图未示)与所述指纹检测放大电路20电性连接。
所述指纹检测放大电路20与所述指纹感测电路10电性连接。所述指纹检测放大电路20检测所述感测电容Cf的电容并转换为电压信号后进行积分操作，然后输出感测电压给所述数模转换电路30，再通过所述数据处理电路40实现对所述感测电容Cf的电容值的检测。
请参阅图4，其为本发明第一实施方式之所述指纹检测放大电路20a的等效电路示意图。所述指纹检测放大电路20a内的信号工作在指定电压域。所述指定电压域限定所述指纹识别装置100的电压变化范围，所述指定电压域以高电平信号NVDDA为上限电压，低电平信号NVSS为下限电压。其中，所述高电平信号NVDDA还可作为所述指纹识别装置100的工作电压，所述低电平信号NVSS还可作为接地电压。在所述指定电压域中，所述低电平信号NVSS为浮动信号。即，所述低电平信号NVSS的电压为周期性变化的脉冲信号。同时，所述高电平信号NVDDA和所述低电平信号NVSS之间的电压差保持不变。所述低电平信号NVSS在控制信号TX的控制下进行切换。所述低电平信号NVSS可在第一低电压和第二低电压之间切换。其中，所述第一低电压大于第二低电压。所述低电平信号NVSS和所述控制信号TX为互补的脉冲信号。换句话说，所述低电平信号NVSS和所述控制信号TX具有相同的脉冲宽度以及脉冲频率， 在所述控制信号TX处于高电平时，控制所述低电平信号NVSS处于所述第二低电压；在所述控制信号TX处于低电平时，所述低电平信号NVSS处于所述第一低电压。在本发明的至少一个实施方式中，所述第一低电压可以为0伏特，所述第二低电压为负电压，其电压值可根据用户的需求进行设置。
所述指纹检测放大电路20a在所述低电平信号NVSS处于所述第一低电压和所述第二低电压时对所述感测电容Cf进行电荷转移操作并分别输出第一输出信号VOUTP和第二输出信号VOUTN。所述第一输出信号VOUTP和所述第二输出信号VOUTN的电压变化方向相反。在本实施方式中，所述第一输出信号VOUTP为递减信号，所述第二输出信号VOUTN为递增信号。所述第一输出信号VOUTP和所述第二输出信号VOUTN具有共模电压。在本实施方式中，所述共模电压为参考电压VCM。
所述指纹检测放大电路20a包括全差分放大器21、开关组23、第一反馈电路25a以及第二反馈电路27a。所述全差分放大器21通过所述开关组23与所述感测电极12电性连接，用于通过所述开关组23感测所述感测电容Cf并将所述感测电容Cf的电容值转换为所述电压信号后进行积分操作，以实现放大处理。
所述开关组23包括第一开关K1、第二开关K2_1以及第三开关K2_2。所述第一开关K1的一端与所述感测电极12电性连接，另一端接收所述参考电压VCM。所述第一开关K1受控于预充电信号PRE。所述第二开关K2_1的一端与所述感测电极12电性连接，另一端与所述全差分放大器21的第一输入端211电性连接。所述第二开关K2_1受控于第一感测使能信号SENSOR_EN_P。所述第三开关K2_2的一端与所述感测电极12电性连接，另一端与所述全差分放大器21的第二输入端213电性连接。所述第三开关K2_2受控于第二感测使能信号SENSOR_EN_N。
所述全差分放大器21具有所述第一输入端211、所述第二输入端213、第一输出端215以及第二输出端217。其中，所述第一输出端215作为所述第一输出信号VOUTP的输出端，所述第二输出端217作为所述第二输出信号VOUTN的输出端。在本实施方式中，所述第一输入端211为反向输入端，所述第二输入端213为正向输入端。所述第一输出端215为正向输出端，所述第二输出端217为反向输出端。其中，所述共模电压大于所述第一输出端215的最小值且小于所述第一输出端215的最大值；所述共模电压大于所述第二输出端217的最小值且小于所述第二输出端217的最大值。
所述第一反馈电路25a电性连接在所述第一输入端211和所述第一输出端215的两端。所述第一反馈电路25a用于将通过所述第二开关K2_1输入的所述感测电容Cf的电容值转换为所述电压信号后进行积分操作。所述第一反馈电路25a包括第一反馈电容CFB1以及第一主控制开关K3_1。所述第一反馈电容CFB1的两端分别与所述第一输入端211和所述第一输出端215电性连接。所述第一主控制开关K3_1的两端分别与所述第一输入端211和所述第一输出端215电性连接。所述第一主控制开关K3_1受控于重置信号RST。
所述第二反馈电路27b电性连接在所述第二输入端213和所述第二输出端217的两端。所述第二反馈电路27a用于将通过所述第三开关K2_2输入的所述感测电容Cf的电容值转换为所述电压信号后进行积分操作。所述第二反馈电路 27a包括第二反馈电容CFB2以及第二主控制开关K3_2。所述第二反馈电容CFB2的两端分别与所述第二输入端213和所述第二输出端217电性连接。所述第二主控制开关K3_2的两端分别与所述第二输入端213和所述第二输出端217电性连接。所述第二主控制开关K3_2受控于所述重置信号RST。在本实施方式中，所述第二反馈电容CFB2和所述第一反馈电容CFB1具有相同的电容值。
请一并参阅图5，其为第一实施方式中所述重置信号RST、预充电信号PRE、第一感测使能信号SENSOR_EN_P、第二感测使能信号SENSOR_EN_N、控制信号TX以及低电平信号NVSS的时序示意图。所述指纹检测放大电路20a的具体工作原理如下：
所述指纹检测放大电路20a可工作在重置阶段T1、预充电阶段T2、第一电荷转移阶段T3以及第二电荷转移阶段T4。其中，所述指纹检测放大电路20首先依次工作在所述重置阶段T1和所述预充电阶段T2，然后所述指纹检测放大电路20a交替工作在第一电荷转移阶段T3和所述第二电荷转移阶段T4。在本实施方式中，所述重置阶段T1和所述预充电阶段T2之间存在预设时间间隔。在所述预设时间间隔里，所述指纹检测放大电路20a不执行任何操作。
在所述重置阶段T1，所述预充电信号PRE、所述第一感测使能信号SENSOR_EN_P、所述第二感测使能信号SENSOR_EN_N以及所述控制信号TX处于低电平，所述重置信号RST处于高电平，所述低电平信号NVSS处于所述第一低电压。在所述预充电信号PRE的控制下，所述第一开关K1断开。在所述第一感测使能信号SENSOR_EN_P的控制下，所述第二开关K2_1断开。在所述第二感测使能信号SENSOR_EN_N的控制下，所述第三开关K2_2断开。在所述重置信号RST的控制下，所述第一主控制开关K3_1和所述第二主控制开关K3_2闭合。因此，所述第一反馈电容CFB1和所述第二反馈电容CFB2两端的电荷分别为0。即，QCFB1＝0，QCFB2＝0。其中，QCFB1表示所述第一反馈电容CFB1上的电荷，QCFB2表示所述第二反馈电容CFB2上的电荷。
在所述预充电阶段T2，所述重置信号RST、所述第一感测使能信号SENSOR_EN_P、所述第二感测使能信号SENSOR_EN_N以及所述控制信号TX处于低电平，所述预充电信号PRE处于高电平，所述低电平信号NVSS处于所述第一低电压。在所述预充电信号PRE的控制下，所述第一开关K1闭合，使得所述参考电压VCM对所述感测电容Cf进行预充电操作。此时，所述指纹检测放大电路20b内的总电荷为所述感测电容Cf上的电荷。所述感测电容Cf上的电荷可通过公式一进行计算得到。
Qcf＝VCM*Cf     公式一
其中，QCF表示在所述预充电阶段T2时所述感测电容Cf上的电荷，VCM表示所述参考电压VCM，Cf表示所述感测电容Cf的电容值。
同时，在所述第一感测使能信号SENSOR_EN_P的控制下，所述第二开关K2_1断开。在所述第二感测使能信号SENSOR_EN_N的控制下，所述第三开关K2_2断开。在所述重置信号RST的控制下，所述第一主控制开关K3_1和所述第二主控制开关K3_2断开。
在所述第一电荷转移阶段T3，所述重置信号RST、所述预充电信号PRE以及所述第二感测使能信号SENSOR_EN_N处于低电平，所述第一感测使能信号 SENSOR_EN_P处于高电平，所述控制信号TX由低电平切换为高电平，所述低电平信号NVSS由所述第一低电压切换至所述第二低电压。所述感测电容Cf上的电荷向所述第一反馈电路25a内的所述第一反馈电容CFB1转移，对所述全差分放大器21的第一输入端211进行充电，以实现一次所述积分操作。在所述第一电荷转移阶段T3时，所述指纹检测放大电路20a的总电荷由所述感测电容Cf上的电荷和所述第一反馈电容CFB1上的电荷构成。即，所述指纹检测放大电路20a内的总电荷可通过公式二计算得出。
Qcf1＝VCM*Cf＝(VCM-VOUTP)*CFB1+(VCM-NVDDA)*Cf     公式二
其中，Qcf1表示在所述第一电荷转移阶段T3进行电荷转移之前所述感测电容Cf的总电荷，VCM表示所述参考电压，VOUTP表示所述第一输出端215的电压，CFB1表示所述第一反馈电容CFB1的电容值，NVDDA表示系统供电电压，Cf表示所述感测电容Cf的电容值。
所述第一反馈电容CFB1两端的电压差为所述参考电压VCM和所述第一输出端215的电压差。同时，由于所述低电平信号NVSS切换至所述第二低电压，使得所述感测电容Cf与所述第一输入端211电性连接的一端的电压发生变化为所述参考电压VCM和所述第二低电压之和。
根据电荷守恒定律，即，QCf1＝QCf。因此，结合公式一和公式二，所述第一输出端215的电压可根据公式三计算得出。
其中，VOUTP表示所述第一输出端215的电压，VCM表示所述参考电压，Cf表示所述感测电容Cf的电容值，CFB1表示所述第一反馈电容CFB1的电容值，NVDDA表示所述系统供电电压。
在所述第二电荷转移阶段T4，所述重置信号RST、所述预充电信号PRE以及所述第一感测使能信号SENSOR_EN_P处于低电平，所述第二感测使能信号SENSOR_EN_N处于高电平，所述控制信号TX由高电平切换为低电平，所述低电平信号NVSS由所述第二低电压切换至所述第一低电压。将所述感测电容Cf上存储的电荷向所述第二反馈电路27内的所述第二反馈电容CFB2转移，对所述全差分放大器21的第二输入端213进行充电，以实现一次所述积分操作。在所述第二电荷转移阶段T4时，所述指纹检测放大电路20a的总电荷由所述感测电容Cf上的电荷和所述第一反馈电容CFB1上的电荷构成。即，所述指纹检测放大电路20a内的总电荷可通过公式四计算得出。
Qcf2＝(VCM-NVDDA)*Cf＝(VCM-VOUTN)*CFB2+VCM*Cf        公式四
其中，Qcf2表示在所述第二电荷转移阶段T4进行电荷转移之前所述感测电容Cf的总电荷，VCM表示所述参考电压VCM，NVDDA表示所述系统供电电压，Cf表示所述感测电容Cf的电容值，VOUTN表示所述第二输出端217的电压，CFB2表示所述第二反馈电容CFB2的电容值。
所述第二反馈电容CFB2两端的电压差为所述参考电压VCM和所述第二输出端217的电压差。同时，由于所述低电平信号NVSS切换至所述第一低电压，使得所述感测电容Cf与所述第一输入端211电性连接的一端的电压发生变化为所述参考电压VCM。
根据电荷守恒定律，即，QCf＝QCf2。因此，结合公式一和公式四，所述第一输出端215和第二输出端217的电压可通过如下公式五计算得出。
其中，VOUTN表示所述第二输出端217的电压，VCM表示所述参考电压，Cf表示所述感测电容Cf的电容值，CFB2表示所述第二反馈电容CFB2的电容值，NVDDA表示所述系统供电电压。
因此，所述第一输出端215和所述第二输出端217的差值可如下公式六所示。
重复N次所述第一电荷转移阶段T3和所述第二电荷转移阶段T4时，所述第一输出端215和所述第二输出端217的差值可如下公式七所示。
从上述公式七中可以看出，所述全差分放大器21的所述第一输出端215的电压和所述第二输出端217的电压存在共模电压，所述共模电压为所述高电平信号NVDDA的一半。如图6所示，所述第一输出信号VOUTP由所述共模电压递减变化，所述第二输出信号VOUTN由所述共模电压递增变化。
上述所述指纹检测放大电路20a以及所述指纹识别装置100，所述指定电压域的所述低电平信号NVSS为浮动信号，在所述低电平信号NVSS的上升沿和下降沿可控制所述全差分放大器21输出信号，以提高所述指纹检测放大电路20a的输出增益。即，相较于常规差分放大器在相同的积分操作次数下，采用所述全差分放大器21的输出信号的增益增加一倍。同时，可提高所述指纹检测放大电路20a的共模噪声抑制能力，可有效降低噪音，进而提高所述指纹检测放大电路20a的信噪比。
请参阅图7，其为本发明第二实施方式之所述指纹检测放大电路20b的等效电路示意图。所述指纹检测放大电路20b内的信号工作在指定电压域。所述指定电压域限定所述指纹识别装置100的电压变化范围，所述指定电压域以高电平信号NVDDA为上限电压，低电平信号NVSS为下限电压。其中，所述高电平信号NVDDA还可作为所述指纹识别装置100的工作电压，所述低电平信号NVSS还可作为接地电压。在所述指定电压域中，所述低电平信号NVSS为浮动信号。即，所述低电平信号NVSS的电压为周期性变化的脉冲信号。同时，所述高电平信号NVDDA和所述低电平信号NVSS之间的电压差保持不变。所述低电平信号NVSS在控制信号TX的控制下进行切换。所述低电平信号NVSS可在第一低电压和第二低电压之间切换。其中，所述第一低电压大于第二低电压。所述低电平信号NVSS和所述控制信号为互补的脉冲信号。换句话说，所述低电平信号NVSS和所述控制信号TX具有相同的脉冲宽度以及脉冲频率，在所述控制信号TX处于高电平时，控制所述低电平信号NVSS处于所述第二低电压；在所述控制信号TX处于低电平时，所述低电平信号NVSS处于所述第一低电压。在本发明的至少一个实施方式中，所述第一低电压可以为0伏特，所述第二低电压为负电压，其电压值可根据用户的需求进行设置。
所述指纹检测放大电路20b基于所述低电平信号NVSS的上升沿和下降沿 将所述感测电容Cf转换为电压信号后进行两次积分操作并采用全差分电路产生第一输出信号VOUTP和第二输出信号VOUTN。所述第一输出信号VOUTP和所述第二输出信号VOUTN的电压变化方向相反。在本实施方式中，所述第一输出信号VOUTP为递减信号，所述第二输出信号VOUTN为递增信号。所述第一输出信号VOUTP和所述第二输出信号VOUTN具有相同的起始电压。在本实施方式中，所述起始电压为参考电压VCM。
所述指纹检测放大电路20b包括全差分放大器21、开关组23、第一反馈电路25b以及第二反馈电路27b。所述全差分放大器21通过所述开关组23与所述感测电极12电性连接，用于通过所述开关组23感测所述感测电容Cf并将所述感测电容Cf的电容值转换为电压信号后进行积分处理，以实现放大处理。
所述开关组23包括第一开关K1、第二开关K2_1以及第三开关K2_2。所述第一开关K1的一端与所述感测电极12电性连接，另一端接收所述参考电压VCM。所述第一开关K1受控于预充电信号PRE。所述第二开关K2_1的一端与所述感测电极12电性连接，另一端与所述全差分放大器21的第一输入端211电性连接。所述第二开关K2_1受控于第一感测使能信号SENSOR_EN_P。所述第三开关K2_2的一端与所述感测电极12电性连接，另一端与所述全差分放大器21的第二输入端213电性连接。所述第三开关K2_2受控于第二感测使能信号SENSOR_EN_N。
所述全差分放大器21具有所述第一输入端211、所述第二输入端213、第一输出端215以及第二输出端217。其中，所述第一输出端215作为所述第一输出信号VOUTP的输出端，所述第二输出端217作为所述第二输出信号VOUTN的输出端。在本实施方式中，所述第一输入端211为反向输入端，所述第二输入端213为正向输入端。所述第一输出端215为正向输出端，所述第二输出端213为反向输出端。在所述低电平信号NVSS的上升沿和下降沿，所述全差分放大器21的第一输出端215和所述第二输出端217交替输出。
所述第一反馈电路25b电性连接在所述第一输入端211和所述第一输出端215的两端。所述第一反馈电路25b用于将通过所述第二开关K2_1输入的所述感测电容Cf的电容值转换为电压信号后进行积分操作。所述第一反馈电路25b包括第一反馈电容CFB1、第一主控制开关K3_1、第一辅助开关K4_1、第二辅助开关K5_1、第三辅助开关K6_1以及第四辅助开关K7_1。所述第一主控制开关K3_1的两端分别与所述全差分放大器21的第一输入端211和所述第一输出端215电性连接。所述第一反馈电容CFB1的一端通过所述第一辅助开关K4_1与所述全差分放大器21的第一输入端211电性连接，且通过所述第三辅助开关K6_1接收所述低电平信号NVSS；所述第一反馈电容CFB1的另一端通过所述第二辅助开关K5_1与所述全差分放大器21的第一输出端215电性连接，且通过所述第四辅助开关K7_1接收电源电压VDC_OS。所述第一主控制开关K3_1、所述第三辅助开关K6_1以及所述第四辅助开关K7_1受控于重置信号RST。所述第一辅助开关K4_1以及所述第二辅助开关K5_1受控于反向重置信号NRST。其中，所述重置信号RST和所述反向重置信号NRST为互补的脉冲信号。换句话说，所述重置信号RST和所述反向重置信号NRST具有相同的脉冲宽度以及脉冲频率，在所述重置信号RST处于高电平时，所述反向重置信号NRST处于 所述低电平；在所述重置信号RST处于低电平时，所述反向重置信号NRST处于高电平。
所述第二反馈电路27b电性连接在所述第二输入端213和所述第二输出端217的两端。所述第二反馈电路27b用于将通过所述第三开关K2_2输入的所述感测电容Cf的电容值转换为电压信号后进行积分操作。所述第二反馈电路27b包括第二反馈电容CFB2、第二主控制开关K3_2、第五辅助开关K4_2、第六辅助开关K5_2、第七辅助开关K6_2以及第八辅助开关K7_2。所述第二主控制开关K3_2的两端分别与所述全差分放大器21的第二输入端213和所述第二输出端217电性连接。所述第二反馈电容CFB2的一端通过所述第五辅助开关K4_2与所述全差分放大器21的第二输入端213电性连接，且通过所述第七辅助开关K6_2接收所述低电平信号NVSS；所述第二反馈电容CFB2的另一端通过所述第六辅助开关K5_2与所述全差分放大器21的第二输出端217电性连接，且通过所述第八辅助开关K7_2接收所述电源电压VDC_OS。所述第二主控制开关K3_2、所述第七辅助开关K6_2以及所述第八辅助开关K7_2受控于重置信号RST。所述第五辅助开关K4_2以及所述第六辅助开关K5_2受控于反向重置信号NRST。在本实施方式中，所述第二反馈电容CFB2和所述第一反馈电容CFB1具有相同的电容值。
请一并参阅图8，其为第二实施方式中重置信号RST、反向重置信号NRST、预充电信号PRE、第一感测使能信号SENSOR_EN_P、第二感测使能信号SENSOR_EN_N、控制信号TX以及低电平信号NVSS的时序示意图。所述指纹检测放大电路20b的具体工作原理如下：
所述指纹检测放大电路20b可工作在重置阶段T1、预充电阶段T2、第一电荷转移阶段T3以及第二电荷转移阶段T4。其中，在所述重置阶段T1和所述预充电阶段T2后，所述指纹检测放大电路20b交替工作在第一电荷转移阶段T3和所述第二电荷转移阶段T4。在本实施方式中，所述重置阶段T1和所述预充电阶段之间存在预设时间间隔。在所述预设时间间隔里，所述指纹检测放大电路20b不执行任何操作。
在所述重置阶段T1，所述反向重置信号NRST、所述预充电信号PRE、所述第一感测使能信号SENSOR_EN_P、所述第二感测使能信号SENSOR_EN_N以及所述控制信号TX处于低电平，所述重置信号RST处于高电平，所述低电平信号NVSS处于所述第一低电压。在所述预充电信号PRE的控制下，所述第一开关K1断开。在所述第一感测使能信号SENSOR_EN_P的控制下，所述第二开关K2_1断开。在所述第二感测使能信号SENSOR_EN_N的控制下，所述第三开关K2_2断开。在所述重置信号RST的控制下，所述第一反馈电路25a中的所述第一主控制开关K3_1、所述第三辅助开关K6_1以及所述第四辅助开关K7_1闭合，同时所述第二反馈电路27b中所述第二主控制开关K3_2、所述第七辅助开关K6_2以及所述第八辅助开关K7_2闭合。在所述反向重置信号NRST的控制下，所述第一反馈电路25a的所述第一辅助开关K4_1以及所述第二辅助开关K5_1断开，同时，所述第二反馈电路27b中的所述第五辅助开关K4_2以及所述第六辅助开关K5_2断开。所述第一反馈电容CFB1两端的电荷通过公式八计算得出。
QCFB1＝CFB1*(NVSS-VDC_OS)     公式八
其中，QCFB1表示在所述重置阶段T1时所述第一反馈电容CFB1上的电荷，CFB1表示所述第一反馈电容CFB1的电容值，NVSS表示所述低电平信号NVSS，VDC_OS表示所述电源电压VDC_OS。
所述第二反馈电容CFB2两端的电荷通过公式九计算得出。
QFB2＝CFB2*(VDC_OS-NVSS) 公式九
在所述预充电阶段T2，所述重置信号RST所述第一感测使能信号SENSOR_EN_P、所述第二感测使能信号SENSOR_EN_N以及所述控制信号TX处于低电平，所述预充电信号PRE和所述反向重置信号NRST处于高电平，所述低电平信号NVSS处于所述第一低电压。在所述预充电信号PRE的控制下，所述第一开关K1闭合，使得所述参考电压VCM对所述感测电容Cf进行预充电操作。此时，所述感测电容Cf的电荷可通过上述公式一进行计算得到。
同时，在所述第一感测使能信号SENSOR_EN_P的控制下，所述第二开关K2_1断开。在所述第二感测使能信号SENSOR_EN_N的控制下，所述第三开关K2_2断开。在所述重置信号RST的控制下，所述第一反馈电路25a中的所述第一主控制开关K3_1、所述第三辅助开关K6_1以及所述第四辅助开关K7_1断开，同时所述第二反馈电路27b中所述第二主控制开关K3_2、所述第七辅助开关K6_2以及所述第八辅助开关K7_2断开。在所述反向重置信号NRST的控制下，所述第一反馈电路25a的所述第一辅助开关K4_1以及所述第二辅助开关K5_1闭合，同时，所述第二反馈电路27b中的所述第五辅助开关K4_2以及所述第六辅助开关K5_2闭合。由于所述第一反馈电容CFB1和所述第二反馈电容CFB2没有放电回路，所述第一反馈电容CFB1和所述第二反馈电容CFB2上的电荷保持不变。
在所述第一电荷转移阶段T3，所述重置信号RST、所述预充电信号PRE以及所述第二感测使能信号SENSOR_EN_N处于低电平，所述第一感测使能信号SENSOR_EN_P和所述反向重置信号NRST处于高电平，所述控制信号TX由低电平切换为高电平，所述低电平信号NVSS由所述第一低电压切换至所述第二低电压。所述感测电容Cf上的电荷向所述第一反馈电路25b内的所述第一反馈电容CFB1转移，对所述全差分放大器21的第一输入端211进行充电，以实现一次所述积分操作。在所述第一电荷转移阶段T3时，所述指纹检测放大电路20b的总电荷由所述感测电容Cf上的电荷和所述第一反馈电容CFB1上的电荷构成。即，所述指纹检测放大电路20b内的总电荷可通过公式十计算得出。
Qcf1＝VCM*Cf+CFB1*(NVSS-VDC_OS)
＝(VCM-VOUTP)*CFB1+(VCM-NVDDA)     公式十
其中，Qcf1表示在所述第一电荷转移阶段T3进行电荷转移之前所述指纹检测放大电路20b以及所述第一输入端211上的总电荷，VCM表示所述参考电压VCM，Cf表示所述感测电容Cf的电容值，CFB1表示所述第一反馈电容CFB1的电容值，NVSS表示所述低电平信号NVSS，VDC_OS表示所述电源电压VDC_OS，VOUTP表示所述第一输出端215的电压，NVDDA表示所述系统供电电压。
所述第一反馈电容CFB1两端的电压差为所述参考电压VCM和所述第一输出端215的电压差。同时，由于所述低电平信号NVSS切换至所述第二低电压，使得所述感测电容Cf与所述第一输入端211电性连接的一端的电压发生变化为所述参考电压VCM和所述第二低电压之和。
根据电荷守恒定律，即，QCf＝QCf1。因此，结合公式一、公式八以及公式十，所述第一输出端215的电压可根据公式十一计算得出。
其中，VOUTP表示所述第一输出端215的电压，VCM表示所述参考电压，VDC_OS表示所述电源电压，Cf表示所述感测电容Cf的电容值，CFB2表示所述第二反馈电容CFB2的电容值，NVDDA表示所述系统供电电压。
在所述第二电荷转移阶段T4，所述重置信号RST、所述预充电信号PRE以及所述第一感测使能信号SENSOR_EN_P处于低电平，所述第二感测使能信号SENSOR_EN_N处于高电平，所述控制信号TX由高电平切换为低电平，所述低电平信号NVSS由所述第二低电压切换至所述第一低电压。将所述感测电容Cf上存储的电荷向所述第二反馈电路27内的所述第二反馈电容CFB2转移，对所述全差分放大器21的第二输入端213进行充电，以实现一次积分操作。在所述第二电荷转移阶段T4时，所述指纹检测放大电路20b的总电荷由所述感测电容Cf上的电荷和所述第一反馈电容CFB1上的电荷构成。即，所述指纹检测放大电路20b内的总电荷可通过公式十二计算得出。
Qcf1＝(VCM-NVDDA)*Cf+CFB2*(VDC_OS-NVSS)
＝(VCM-VOUTP)*CFB2+VCM*Cf      公式十二
其中，Qcf1表示在所述第二电荷转移阶段T4进行电荷转移之前所述感测电容Cf的总电荷，VCM表示所述参考电压VCM，Cf表示所述感测电容Cf的电容值，CFB2表示所述第二反馈电容CFB2的电容值，NVSS表示所述低电平信号NVSS，VDC_OS表示所述电源电压VDC_OS，VOUTP表示所述第一输出端215的电压，NVDDA表示所述系统供电电压。
所述第二反馈电容CFB2两端的电压差为所述参考电压VCM和所述第二输出端217的电压差。同时，由于所述低电平信号NVSS切换至所述第一低电压，使得所述感测电容Cf与所述第一输入端211电性连接的一端的电压发生变化为所述参考电压VCM。
根据电荷守恒定律，即，QCf2＝QCf。因此，结合公式一、公式九以及公式十二，所述第二输出端217的电压可通过公式十三计算得出。
其中，VOUTN表示所述第二输出端217的电压，VCM表示所述参考电压，VDC_OS表示所述电源电压VDC_OS，Cf表示所述感测电容Cf的电容值，CFB2表示所述第二反馈电容CFB2的电容值，NVDDA表示所述系统供电电压。
因此，所述第一输出端215和所述第二输出端217的差值可如下方公式十四所示。
重复N次所述第一电荷转移阶段T3和所述第二电荷转移阶段T4时，所述第一输出端215和所述第二输出端217的差值可如下方公式十五所示。
从上述公式十五中可以看出，所述全差分放大器21的所述第一输出端215的电压和所述第二输出端217的电压存在共模电压，所述共模电压为所述高电平信号NVDDA的一半。如图9所示，通过调整所述电源电压VDC_OS的电压值，所述第一输出信号VOUTP在第一预设值和第二预设值之间呈递减线性变化，所述第二输出信号VOUTN从第三预设值和第四预设值之间呈递增线性变化。其中，所述第一预设值大于所述第二预设值；所述第三预设值小于所述第四预设值。在本发明的至少一个实施方式中，所述第一预设值和所述第四预设值可以相等，所述第二预设值和所述第三预设值可以相等。
上述所述指纹检测放大电路20b以及所述指纹识别装置100，所述指定电压域的所述低电平信号NVSS为浮动信号，在所述低电平信号NVSS的上升沿和下降沿可控制所述全差分放大器21输出信号，以提高所述指纹检测放大电路20b的输出增益。即，相较于常规差分放大器在相同的积分操作次数下，采用所述全差分放大器21的输出信号的增益增加一倍。同时，可提高所述指纹检测放大电路20b的共模噪声抑制能力，可有效降低噪音，进而提高所述指纹检测放大电路20b的信噪比。另外，通过将所述第一反馈电路25b和所述第二反馈电路27b受控于所述电源电压VDC_OS，可实现所述第一输出端215从最高值呈递减变化，所述第二输出端217的电压可从最低值呈递增变化，充分利用指纹检测放大电路20b的动态电压范围。
本技术领域的普通技术人员应当认识到，以上的实施方式仅是用来说明本发明，而并非用作为对本发明的限定，只要在本发明的实质精神范围之内，对以上实施例所作的适当改变和变化都落在本发明要求保护的范围之内。

Claims (10)

  1. 一种指纹检测放大电路，用于检测感测电极与手指之间形成的感测电容的电容值转换为电压信号；其特征在于，所述指纹检测放大电路包括：
    全差分放大器，具有第一输入端、第二输入端、第一输出端以及第二输出端；
    开关组，电性连接在所述感测电极和所述全差分放大器之间，用于控制所述第一输入端与所述第二输入端交替与所述感测电极电性连接；
    第一反馈电路，与所述第一输入端和所述第一输出端的两端电性连接，用于对输入至所述第一输入端的所述感测电容的电容值转换为电压信号后进行积分；以及
    第二反馈电路，与所述第二输入端和所述第二输出端的两端电性连接，用于对输入至所述第二输入端的所述感测电容的电容值转换为电压信号后进行积分；
    所述指纹检测放大电路内的信号工作在指定电压域；在所述指定电压域中的低电平信号为浮动信号，且在控制信号的控制下进行切换；所述低电平信号可在第一低电压和第二低电压之间切换；其中，所述第一低电压大于第二低电压；所述低电平信号在所述第一低电压和所述第二低电压之间切换时，所述全差分放大器的第一输出端和所述第二输出端交替输出；所述第一输出端的电压和所述第二输出端的电压具有共模电压。
  2. 如权利要求1所述的指纹检测放大电路，其特征在于，所述指纹检测放大电路工作在重置阶段、预充电阶段、第一电荷转移阶段以及第二电荷转移阶段；所述指纹检测放大电路首先依次工作在所述重置阶段和所述预充电阶段，然后所述指纹检测放大电路交替工作在第一电荷转移阶段和所述第二电荷转移阶段；所述低电平信号的上升沿或下降沿控制所述指纹检测放大电路在所述第一电荷转移阶段和所述第二电荷转移阶段之间切换。
  3. 如权利要求2所述的指纹检测放大电路，其特征在于，在所述第一电荷转移阶段，所述指纹检测放大电路将所述感测电容的电容值转换为电压信号后执行一次积分操作，并通过所述第一输出端输出所述感测电压；在所述第二电荷转移阶段，所述指纹检测放大电路对所述感测电容的电容值转换为电压信号后执行一次积分操作，并通过所述第二输出端输出所述感测电压。
  4. 如权利要求2所述的指纹检测放大电路，其特征在于，在所述第一电荷转移阶段，所述第一反馈电路控制所述第一输出端的电压以所述共模电压为起点呈线性变化；在所述第二电荷转移阶段，所述第二反馈电路控制所述第二输出端的电压以所述共模电压为起点呈线性变化。
  5. 如权利要求4所述的指纹检测放大电路，其特征在于，所述第一反馈电路包括第一反馈电容以及第一主控制开关；所述第一反馈电容的两端分别与所述第一输入端和所述第一输出端电性连接；所述第一主控制开关的两端分别与所述第一输入端和所述第一输出端电性连接；所述第二反馈电路包括第二反馈电容以及第二主控制开关；所述第二反馈电容的两端分别与所述第二输入端和 所述第二输出端电性连接；所述第二主控制开关的两端分别与所述第二输入端和所述第二输出端电性连接；所述第一主控制开关和所述第二主控制开关均受控于重置信号。
  6. 如权利要求4所述的指纹检测放大电路，其特征在于，所述第一输出端的电压递减变化，所述第二输出信号为递增变化。
  7. 如权利要求2所述的指纹检测放大电路，其特征在于，在所述第一电荷转移阶段，所述第一反馈电路控制所述第一输出端的电压在第一预设值和第二预设值之间呈线性变化；在所述第二电荷转移阶段，所述第二反馈电路控制所述第二输出端的电压在第三预设值和第四预设值之间呈线性变化；其中，所述第一预设值大于所述第二预设值；所述第三预设值小于所述第四预设值。
  8. 如权利要求7所述的指纹检测放大电路，其特征在于，所述第一反馈电路包括第一反馈电容、第一主控制开关、第一辅助开关、第二辅助开关、第三辅助开关以及第四辅助开关；所述第一主控制开关的两端分别与所述第一输入端和所述第一输出端电性连接；所述第一反馈电容的一端通过所述第一辅助开关与所述第一输入端电性连接，且通过所述第三辅助开关接收所述低电平信号；所述第一反馈电容的另一端通过所述第二辅助开关与所述第一输出端电性连接，且通过所述第四辅助开关接收电源电压；所述第一主控制开关、所述第三辅助开关以及所述第四辅助开关受控于重置信号；所述第一辅助开关以及所述第二辅助开关受控于反向重置信号；所述第二反馈电路包括第二反馈电容、第二主控制开关、第五辅助开关、第六辅助开关、第七辅助开关以及第八辅助开关；所述第二主控制开关的两端分别与所述第二输入端和所述第二输出端电性连接；所述第二反馈电容的一端通过所述第五辅助开关与所述第二输入端电性连接，且通过所述第七辅助开关接收所述低电平信号；所述第二反馈电容的另一端通过所述第六辅助开关与所述第二输出端电性连接，且通过所述第八辅助开关接收所述电源电压；所述第二主控制开关、所述第七辅助开关以及所述第八辅助开关受控于重置信号；所述第五辅助开关以及所述第六辅助开关受控于反向重置信号；所述重置信号和所述反向重置信号为互补的脉冲信号。
  9. 如权利要求7所述的指纹检测放大电路，其特征在于，所述共模电压大于所述第一输出端的最小值且小于所述第一输出端的最大值；所述共模电压大于所述第二输出端的最小值且小于所述第二输出端的最大值。
  10. 一种指纹识别装置，包括指纹感测电路、指纹检测放大电路、数模转换电路以及数据处理电路；其特征在于，所述指纹检测放大电路采用如权利要求1至9中任意一项所述的所述指纹检测放大电路。
PCT/CN2023/074960 2022-02-28 2023-02-08 指纹检测放大电路以及指纹识别装置 WO2023160391A1 (zh)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CN202210187865.8 2022-02-28
CN202210187865.8A CN114627514A (zh) 2022-02-28 2022-02-28 指纹检测放大电路以及指纹识别装置

Publications (1)

Publication Number Publication Date
WO2023160391A1 true WO2023160391A1 (zh) 2023-08-31

Family

ID=81900034

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CN2023/074960 WO2023160391A1 (zh) 2022-02-28 2023-02-08 指纹检测放大电路以及指纹识别装置

Country Status (3)

Country Link
CN (1) CN114627514A (zh)
TW (1) TWI818459B (zh)
WO (1) WO2023160391A1 (zh)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114627514A (zh) * 2022-02-28 2022-06-14 敦泰电子（深圳）有限公司 指纹检测放大电路以及指纹识别装置
TWI831479B (zh) * 2022-11-18 2024-02-01 大陸商北京集創北方科技股份有限公司 電容式指紋識別方法、電容式指紋識別裝置及資訊處理裝置

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110363184A (zh) * 2019-08-08 2019-10-22 上海思立微电子科技有限公司 指纹感测系统
CN110390317A (zh) * 2019-07-30 2019-10-29 上海思立微电子科技有限公司 像素电路、像素阵列以及光学指纹传感器
CN110598515A (zh) * 2018-06-13 2019-12-20 联咏科技股份有限公司 信号处理电路及系统
US20200161493A1 (en) * 2018-11-16 2020-05-21 Lg Display Co., Ltd. Display panel with photo sensor and display device using the same
US20200343864A1 (en) * 2019-04-24 2020-10-29 Novatek Microelectronics Corp. Signal processing circuit with reduction or cancelation of signal-dependent component
CN112016378A (zh) * 2019-05-29 2020-12-01 联咏科技股份有限公司 信号处理电路及处理感测信号的方法
CN113922776A (zh) * 2021-10-12 2022-01-11 天津理工大学 一种基于开关电容式共模反馈电荷放大器的c/v转换电路
CN114627514A (zh) * 2022-02-28 2022-06-14 敦泰电子（深圳）有限公司 指纹检测放大电路以及指纹识别装置

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2016095268A (ja) * 2014-11-17 2016-05-26 株式会社デンソー 信号処理装置
US20200334437A1 (en) * 2019-04-22 2020-10-22 Himax Technologies Limited Optical fingerprint detecting system
TWI773328B (zh) * 2020-05-21 2022-08-01 聯詠科技股份有限公司 光學指紋感測裝置以及光學指紋感測方法

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110598515A (zh) * 2018-06-13 2019-12-20 联咏科技股份有限公司 信号处理电路及系统
US20200161493A1 (en) * 2018-11-16 2020-05-21 Lg Display Co., Ltd. Display panel with photo sensor and display device using the same
US20200343864A1 (en) * 2019-04-24 2020-10-29 Novatek Microelectronics Corp. Signal processing circuit with reduction or cancelation of signal-dependent component
CN112016378A (zh) * 2019-05-29 2020-12-01 联咏科技股份有限公司 信号处理电路及处理感测信号的方法
CN110390317A (zh) * 2019-07-30 2019-10-29 上海思立微电子科技有限公司 像素电路、像素阵列以及光学指纹传感器
CN110363184A (zh) * 2019-08-08 2019-10-22 上海思立微电子科技有限公司 指纹感测系统
CN113922776A (zh) * 2021-10-12 2022-01-11 天津理工大学 一种基于开关电容式共模反馈电荷放大器的c/v转换电路
CN114627514A (zh) * 2022-02-28 2022-06-14 敦泰电子（深圳）有限公司 指纹检测放大电路以及指纹识别装置

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
JIANG, PEILIANG ET AL.: "Discussion on Pressure Sensor based on Plantar Pressure Information Collection", ZHONGGUO GAO-XIN JISHU QIYE = CHINA HIGH TECHNOLOGY ENTERPRISES, ZHONGGUO GAO-XIN JISHU QIYE FAZHAN PINGJIA ZHONGXIN, CN, no. 15, 20 May 2015 (2015-05-20), CN , pages 66 - 67, XP009548886, ISSN: 1009-2374, DOI: 10.13535/j.cnki.11-4406/n.2015.15.034 *

Also Published As

Publication number Publication date
TWI818459B (zh) 2023-10-11
TW202234286A (zh) 2022-09-01
CN114627514A (zh) 2022-06-14

Similar Documents

Publication Publication Date Title
WO2023160391A1 (zh) 指纹检测放大电路以及指纹识别装置
US10949032B2 (en) Circuit, touch chip, and electronic device for capacitance detection
CN110059536B (zh) 信号处理电路及处理感测信号的方法
KR101573698B1 (ko) 터치 데이터 프로세싱 회로, 이를 포함하는 디스플레이 구동 회로 및 디스플레이 장치
CN111460882B (zh) 电容式图像感测装置与电容式图像感测方法
WO2021036306A1 (zh) 电容感测装置
US20160070381A1 (en) Semiconductor device and semiconductor system for producing noise differences between points of time
CN216053107U (zh) 电容式指纹感测装置
US11029777B2 (en) Touch sensing device and display apparatus including the same
CN109214252B (zh) 一种指纹感测电路及指纹感测装置
TWI356292B (en) Image processing system and method of processing a
CN110411483B (zh) 新型大尺寸传感阵列的读出电路及其传感器阵列
WO2023226475A1 (zh) 触控电路、触控检测放大电路以及触控装置
CN108700621B (zh) 电容感测电路及指纹辨识系统
US11079881B2 (en) Signal processing circuit and system
US10491213B2 (en) Self-capacitive touch sensing circuit and noise suppressing method applied to self-capacitive touch panel
US10379674B2 (en) Mutual-capacitive touch sensing circuit and noise suppressing method applied to mutual-capacitive touch panel
CN110598515B (zh) 信号处理电路及系统
US11023701B2 (en) Signal processing circuit and related method of processing sensing signal
US11012039B2 (en) Signal processing circuit with reduction or cancelation of signal-dependent component
CN209897167U (zh) 像素电路、图像传感器和电子设备
US10942604B2 (en) Touch sensing device and display apparatus including the same
TWI812959B (zh) 指紋採集電路、晶片及電子設備
CN110771154B (zh) 像素电路、图像传感器和电子设备
WO2020252754A1 (zh) 读出电路、图像传感器和电子设备

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 23759016

Country of ref document: EP

Kind code of ref document: A1