WO2016106943A1 - 指纹识别传感器和终端设备 - Google Patents

指纹识别传感器和终端设备 Download PDF

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Publication number
WO2016106943A1
WO2016106943A1 PCT/CN2015/072430 CN2015072430W WO2016106943A1 WO 2016106943 A1 WO2016106943 A1 WO 2016106943A1 CN 2015072430 W CN2015072430 W CN 2015072430W WO 2016106943 A1 WO2016106943 A1 WO 2016106943A1
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WIPO (PCT)
Prior art keywords
sensor
fingerprint recognition
sensor unit
terminal
power supply
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PCT/CN2015/072430
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English (en)
French (fr)
Inventor
杜灿鸿
卓光明
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深圳市汇顶科技股份有限公司
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.)
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Publication date
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
Priority to EP15874636.2A priority Critical patent/EP3242246B1/en
Priority to KR1020167021917A priority patent/KR102014121B1/ko
Priority to CN201590000374.1U priority patent/CN206601715U/zh
Publication of WO2016106943A1 publication Critical patent/WO2016106943A1/zh
Priority to US15/246,991 priority patent/US9965667B2/en
Priority to US15/928,077 priority patent/US10152626B2/en

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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
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/94—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the way in which the control signals are generated
    • H03K17/96—Touch switches
    • H03K17/962—Capacitive touch switches

Definitions

  • the present invention relates to the field of fingerprint recognition technologies, and in particular, to a fingerprint recognition sensor and a terminal device.
  • Capacitive fingerprint recognition sensor is one of the widely used fingerprint sensors. It is composed of a miniaturized array of capacitor plates. The top of the plate is covered with an insulating plate. When the user puts his finger on the insulating plate, the skin is composed. The other plate of the capacitor array. Since the distance between the ridges and valleys of the fingerprints of different regions and the array of capacitor plates is not equal, the capacitance of each of the capacitor plates is changed accordingly, whereby a fingerprint image can be obtained.
  • FIG. 1 shows a conventional capacitive fingerprint sensor including a sensor unit, a drive amplifier 101, a drive metal ring 103, and a power supply (not shown) for powering the sensor unit.
  • the sensor unit comprises a capacitor array consisting of a number of capacitive sensing units 102, of which any one of the capacitive sensing units 102 is schematically represented in FIG.
  • the sensor unit outputs a driving signal to the driving amplifier 101.
  • the driving amplifier 101 amplifies the driving signal and outputs the driving signal to the driving metal ring 103.
  • the coupling capacitance between the finger and the capacitance sensing unit 102 is CX.
  • the driving signal is coupled from the metal ring 103 to the finger through the capacitor CT.
  • the CX between the ridges and valleys of the fingerprints of different regions and the capacitance sensing unit 102 are not equal, and the capacitance sensing unit 102 measures the voltage to change accordingly, thereby obtaining a fingerprint image.
  • the fingerprint recognition sensor of this structure needs to have a metal ring 103 externally, and in order to increase the capacitance CT as much as possible and reduce the signal attenuation, the area of the fingerprint recognition sensor needs to be hollowed out to place the metal ring 103 so that the finger can directly touch To the metal ring 103.
  • the equivalent capacitance formed by the terminal device of the fingerprint recognition sensor to the capacitance CS of the earth and the capacitance CM of the human body to the earth, and the capacitance CH of the human body directly to the device will drive
  • the drive signal above the moving metal ring 103 produces an attenuation.
  • the terminal device adopts a metal casing the attenuation becomes more serious when the user holds the device, thereby reducing the clarity of the fingerprint image and affecting the fingerprint recognition effect.
  • the main object of the present invention is to provide a fingerprint recognition sensor and a terminal device, which aim to expand the application range of the fingerprint recognition sensor and improve the fingerprint recognition effect.
  • the present invention provides a fingerprint recognition sensor, and the fingerprint recognition sensor is applied to the terminal device, including:
  • the sensor unit comprises a capacitor array composed of a plurality of capacitive sensing units, having an output end, a power supply end and a sensor ground end, and the output end outputs a driving signal;
  • the modulation circuit connects the device ground of the terminal device, the output end of the sensor unit, the power supply end and the sensor ground end, and modulates the driving signal into a modulated signal and outputs the signal to the ground end of the sensor, and the voltage of the power supply end changes with the change of the modulation signal.
  • the modulation circuit comprises:
  • a conversion circuit connecting the device ground of the terminal device, and the output end of the sensor unit and the sensor ground, modulating the driving signal into a modulated signal and outputting to the sensor ground;
  • a storage capacitor connected between the power supply end and the sensor ground to stabilize the operating voltage of the sensor unit
  • a high-speed transistor switch connected to the power supply end, and synchronously switching according to the state of the conversion circuit, so that the voltage of the power supply terminal changes with the change of the modulation signal;
  • the power supply, the connection conversion circuit, and the power supply terminal of the sensor unit are connected through a high speed transistor switch to supply power to the conversion circuit and the sensor unit.
  • the sensor unit is connected to the main control module of the terminal device through a communication interface, and the sensor unit outputs a driving signal of a low level when modulating the idle interval, so that the levels of the device ground and the sensor ground are approximately equal.
  • the sensor unit is directly connected to the main control module through the wire, and keeps the communication interface low when the conversion circuit modulates the driving signal; or the fingerprint recognition sensor further includes a resistor array, and the sensor unit passes through the resistance array and the main control module
  • the fingerprint identification sensor further includes a relay module, and the sensor unit is connected to the main control module of the terminal device through the relay module.
  • the relay module receives The data sent by the sensor unit is cached, and the main control module acquires data from the relay module.
  • the sensor unit and the relay module are integrated in a sensor chip.
  • the power source is connected to the sensor unit through a power switch, and the main control module or the relay module controls the opening and closing of the power switch.
  • the conversion circuit, the high speed transistor switch, the power switch, and the relay module are integrated in one chip.
  • the conversion circuit is composed of any one or a combination of at least two of a transistor, an operational amplifier, an inverter, a level shifter, and a digital buffer gate, and a resistor or/and a capacitor.
  • the conversion circuit is composed of two inverters and a resistor
  • the inverter includes a first inverter and a second inverter; a positive input power terminal of the first inverter is connected to a power supply terminal of the sensor unit, and a negative input
  • the power terminal is connected to the device ground, the input terminal is connected to the output end of the sensor unit, and the negative input power terminal and the device ground of the second inverter are connected through a resistor, and the output terminal is connected to the input end of the second inverter;
  • the second inverter is The positive input power terminal is connected to the power supply, the negative input power terminal is connected to the device ground, and the output terminal is connected to the sensor ground end.
  • the first inverter is composed of a first NMOS transistor, a first PMOS transistor and a first resistor, and the gates of the first NMOS transistor and the first PMOS transistor are connected to each other to form an input end of the first inverter
  • a source of a PMOS transistor serves as a positive input power terminal of the first inverter
  • a source of the first NMOS transistor serves as a negative input power terminal of the first inverter
  • a drain of the first NMOS transistor and the first PMOS transistor passes a first resistor is connected, a drain of the first NMOS transistor and the first PMOS transistor can be used as an output end of the first inverter
  • a second inverter is composed of a second NMOS transistor, a second PMOS transistor, and a second resistor.
  • the connection relationship is the same as that of the first inverter.
  • the high speed transistor switch is comprised of any one or a combination of at least two of a Schottky diode, a fast recovery diode, a transistor, a field effect transistor, and a thyristor.
  • a low dropout linear regulator is further included, and the low dropout linear regulator is connected between the power supply terminal and the storage capacitor.
  • the invention also provides a terminal device, the terminal device comprises a fingerprint recognition sensor, and the fingerprint recognition sensor comprises:
  • the sensor unit comprises a capacitor array composed of a plurality of capacitive sensing units, having an output end, a power supply end and a sensor ground end, and the output end outputs a driving signal;
  • a conversion circuit connecting the device ground of the terminal device, and the output end of the sensor unit and the sensor ground, modulating the driving signal into a modulated signal and outputting to the sensor ground;
  • a storage capacitor connected between the power supply end and the sensor ground to stabilize the operating voltage of the sensor unit
  • a high-speed transistor switch connected to the power supply end, and synchronously switching according to the state of the conversion circuit, so that the voltage of the power supply terminal changes with the change of the modulation signal;
  • the power supply, the connection conversion circuit, and the power supply terminal of the sensor unit are connected through a high speed transistor switch to supply power to the conversion circuit and the sensor unit.
  • the invention provides a fingerprint recognition sensor, wherein a high-speed transistor switch and a storage capacitor form a power supply circuit of the sensor unit, and the conversion circuit drives the drive signal outputted by the sensor unit to drive the sensor terminal of the sensor unit. Since the driving signal of the sensor unit is modulated into a modulation signal, when the finger presses the capacitive sensing unit of the sensor unit, the modulated signal forms a loop through the capacitance between the capacitor C X between the finger and the device and the ground of the device of the terminal device. When C X changes, the measured voltage of the capacitive sensing unit of the sensor unit also changes, so that a fingerprint image can be obtained and fingerprint recognition is realized.
  • the fingerprint recognition sensor of the present invention does not need to drive the metal ring, there is no need to open a hole in the surface of the terminal device to place the driving metal ring, so the design of the terminal device is not affected, and can be applied to a mobile phone that does not want to be opened on the screen.
  • Terminal devices such as tablets have expanded the application range of fingerprint recognition sensors.
  • FIG. 1 is a schematic structural view of a fingerprint recognition sensor in the prior art
  • FIG. 2 is a schematic diagram showing the circuit structure of a fingerprint recognition sensor of the present invention.
  • FIG. 3 is a schematic circuit diagram of a conversion circuit in an embodiment of the present invention.
  • FIG. 4 is a schematic diagram showing the circuit connection of the first embodiment of the fingerprint recognition sensor of the present invention.
  • FIG. 6 is a schematic diagram showing the circuit connection of the second embodiment of the fingerprint recognition sensor of the present invention.
  • Figure 7 is a circuit connection diagram of a third embodiment of the fingerprint recognition sensor of the present invention.
  • Figure 8 is a circuit connection diagram of a fourth embodiment of the fingerprint recognition sensor of the present invention.
  • FIG. 9 is a schematic diagram of a fingerprint recognition sensor of the present invention applied to a mobile phone.
  • the fingerprint recognition sensor of the invention is a capacitive fingerprint recognition sensor, and can be applied to terminal devices such as mobile phones, tablet computers, palm devices, smart wearable devices, multimedia players, notebook computers, desktop computers, and access control security.
  • the fingerprint recognition sensor comprises a sensor unit and a modulation circuit.
  • the sensor unit has a capacitor array composed of a plurality of capacitance sensing units, an output end, a power supply end and a sensor ground end, and the output end outputs a driving signal; the modulation circuit is connected to the device ground of the terminal device.
  • the output end of the sensor unit, the power supply end and the sensor ground end modulate the drive signal into a modulated signal and output it to the sensor ground.
  • the voltage at the power supply end changes as the modulation signal changes.
  • the fingerprint recognition sensor is as shown in FIG. 2.
  • the sensor unit 210 includes a conversion circuit 230, a storage capacitor 240, a high speed transistor switch 250, and a power source 260.
  • the sensor unit 210 has an output end, a power supply end (Sensor VDD, hereinafter referred to as SVDD) and a sensor ground end (Sorsor Ground, hereinafter referred to as SGND), and the output end is connected to the conversion circuit 230;
  • the conversion circuit 230 is connected to the device ground of the terminal device (Ground , hereinafter referred to as GND) and the SGND of the sensor unit;
  • the high speed transistor switch 250 is connected to the SVDD of the sensor unit 210, and the high speed transistor 250 can be any one of a Schottky diode, a fast recovery diode, a transistor, a field effect transistor, and a thyristor.
  • the power supply 260 is connected to the conversion circuit 230, and through the high speed
  • the transistor 250 is connected to the SVDD of the sensor unit 210 to supply power to the conversion circuit 230 and the sensor unit 210.
  • the storage capacitor 240 is connected between SVDD and SGND of the sensor unit 210 to stabilize the operating voltage of the sensor unit 210.
  • the high speed transistor switch 250 and the storage capacitor 240 constitute a power supply circuit of the sensor unit 210.
  • the conversion circuit 230 may be composed of any one or a combination of at least two of a transistor, an operational amplifier, an inverter, a level shifter, and a digital buffer gate, and is combined with a resistor or/and a capacitor.
  • the conversion circuit 230 is preferably composed of two inverters (231, 232) and a resistor R3 as shown in FIG. 3.
  • the two inverters include a first inverter 231 and a second inverter 232.
  • the positive input power terminal of the first inverter 231 Connect the SVDD of the sensor unit 210, the negative input power terminal is connected to the GND of the terminal device, the input terminal is connected to the output end of the sensor unit 210, and the negative input power terminal of the second inverter 232 and the GND of the terminal device are connected through the resistor R3, and the output terminal
  • the input terminal of the second inverter 232 is connected; the positive input power terminal of the second inverter 232 is connected to the power source 260, the negative input power terminal is connected to the GND of the terminal device, and the output terminal is connected to the SGND of the sensor unit.
  • the inverter is preferably composed of two transistors and a resistor, wherein the transistor is a metal oxide semiconductor field effect transistor (hereinafter referred to as a MOS transistor), and includes a PMOS transistor (Positive Channel Metal Oxide Semiconductor). Oxide semiconductor field effect transistor) and NMOS transistor (Negative Channel Metal Oxide Semiconductor). As shown in Figure 3, the gates of the PMOS transistors (Q1, Q3) and the NMOS transistors (Q2, Q4) are connected to each other to form the input terminals of the inverters (231, 232), and the source of the PMOS transistors (Q1, Q3) is inverted.
  • MOS transistor metal oxide semiconductor field effect transistor
  • the drains are connected through resistors (R1, R2), and the drains of the PMOS transistors (Q1, Q3) and NMOS transistors (Q2, Q4) can be used as the output terminals of the inverters (231, 232).
  • the sensor unit 210 includes a drive amplifier 220 and a capacitor array composed of a plurality of capacitance sensing units 211, wherein any one of the capacitance sensing units 211 is schematically illustrated in FIG.
  • the output end of the driving amplifier 220 is connected to the conversion circuit 230 as an output end of the sensor unit.
  • the driving amplifier 220 amplifies the driving signal of the sensor unit 210 and outputs the signal to the conversion circuit 230.
  • the conversion circuit 230 modulates the driving signal into a modulation signal and outputs the signal to the modulation signal.
  • the SGND of the sensor unit 210 and the high speed transistor switch 250 are synchronously switched in accordance with the state of the conversion circuit 230 so that the voltage of SVDD of the sensor unit 210 changes as the modulation signal changes.
  • the equivalent capacitance formed by the terminal device's capacitance CS in series with the earth's capacitance CM and the capacitance CH of the human body directly to the terminal device will cause coupling between the human body and the GND of the terminal device. Any application scenario is always there. Since the driving signal of the sensor unit 210 is modulated into a modulation signal, when the finger presses the capacitance sensing unit 211 of the sensor unit 210, the modulation signal forms a loop through the capacitance between the capacitor CX between the finger and the human body and the terminal device GND. When CX changes, the measured voltage of the capacitance sensing unit 211 of the sensor unit 210 also changes, thereby obtaining a fingerprint image.
  • FIG. 4 shows a first embodiment of a specific application of the fingerprint recognition sensor of the present invention.
  • the sensor unit is integrated in a sensor chip, and the sensor chip includes a scanning module and a serial peripheral device.
  • Interface Serial Peripheral Interface, SPI
  • the scanning module outputs a driving signal to scan the capacitor array
  • the SPI module provides an SPI interface, which is a communication interface of the sensing chip and is connected with a communication interface of the terminal module of the terminal device to pass
  • the communication interface communicates with the main control module, for example, the sensor chip sends fingerprint image data to the main control module, and the main control module sends a control command to the sensor chip.
  • the communication interface can also be an I2C (Inter-Inegrated Circuit) interface and other serial/parallel interfaces.
  • I2C Inter-Inegrated Circuit
  • the conversion circuit 230 is composed of four transistors and three resistors as shown in FIG. Wherein, the transistor is a MOS transistor, including PMOS transistors Q1 and Q3, and NMOS transistors Q2 and Q4, and the resistors include R1, R2 and R3.
  • the transistor is a MOS transistor, including PMOS transistors Q1 and Q3, and NMOS transistors Q2 and Q4, and the resistors include R1, R2 and R3.
  • the sensor chip scans the capacitor array and reads the voltages of different capacitance sensing units.
  • the scanning mode is controlled by a scanning module (Scan Block), and the scanning module outputs a driving signal TX.
  • the driving signal TX is a high frequency alternating current signal, which may be a sine wave. Square wave, triangular wave, etc. In the present example, the driving signal TX is a square wave signal with a frequency of 800 kHz, and of course other frequency values.
  • the driving signal TX is modulated to SGND by the conversion circuit 230.
  • the peak-to-peak value of the modulation signal depends on the size of the power supply 260. In this embodiment, it is approximately equal to the input voltage of 2.8V, and of course other voltage values.
  • the driving signal TX is low level SGND
  • the driving signal TX and SVDD voltage difference is close to 2.8V
  • the PMOS transistor Q1 is turned on
  • the R1 resistance value is much larger than the PMOS tube Q1 and the NMOS tube Q2 are turned on.
  • Resistor due to the presence of resistor R1, the node TX_S voltage is pulled high to SVDD regardless of whether NMOS transistor Q2 is turned on or off. Then, the SVDD voltage of TX_S will turn on NMOS transistor Q4, and PMOS transistor Q3 is turned off.
  • NMOS transistor Q4 Connect SGND to GND, and then drive the drive signal TX to maintain the GND voltage, so that the NMOS transistor Q2 is turned off, the state of the PMOS transistor Q1, the PMOS transistor Q3, and the NMOS transistor Q4 remains unchanged, and the voltage of the SGND is maintained at GND, as shown in the figure.
  • the waveform of 5 is shown in phase 1 (Stage1).
  • the drive signal TX becomes a high level
  • the drive signal TX and the SVDD voltage are approximately equal.
  • the PMOS transistor Q1 is turned off, the NMOS transistor Q2 is turned on, and the node TX_S voltage is pulled down to GND, then the low voltage of the TX_S will turn on the PMOS transistor Q3, and the NMOS transistor Q4 is turned off.
  • the PMOS transistor Q3 will force the SGND. Pull up to 2.8V. Since the voltage across the storage capacitor 240 cannot be abruptly changed, it remains approximately 2.8V, so the SVDD voltage will be forced to "pump" to approximately 5.6V, and the high speed transistor switch 250 is naturally turned off due to reverse bias.
  • the driving signal TX changes from a high level to a low level
  • the driving signal TX and the SGND voltage are approximately equal to about 2.8V.
  • the SVDD voltage is 5.6V
  • the PMOS transistor Q1 and the NMOS transistor Q2 are simultaneously turned on, due to the resistance R1.
  • the TX_S voltage is approximately SVDD
  • the NMOS transistor Q4 is turned on
  • the PMOS transistor Q1 is turned off
  • the SGND is connected to GND, and the process of the phase 1 is repeated.
  • the process of driving signal TX from high level to low level is shown in phase 3 (Stage 3) of the waveform of FIG.
  • the above is the working process of the conversion circuit.
  • the SGND of the sensing chip will be modulated into a square wave waveform of the same frequency as the driving signal TX, and the voltage of the modulation signal is equal to the power supply voltage of the power supply 260.
  • the data needs to be transmitted to the main control module of the terminal device, and the main control module performs data processing and recognizes the fingerprint object.
  • the fingerprint sensor chip and the main control module are connected by using the SPI interface, and the communication interface has Multiple ways of implementation, not limited to the SPI interface of this example.
  • the conversion circuit 230 modulates the SGND into an AC square wave signal
  • the signal of the SPI interface is also modulated at the same time, and the modulated SPI signal cannot be directly recognized by the SPI module of the main control module, resulting in communication abnormality.
  • the sensor chip is not a continuous uninterrupted array of scanning capacitors, there is a time interval between the scanning of different capacitive sensing units. In most cases, the interval is large enough to directly use this time interval for data transmission. . Therefore, it is only necessary to scan the idle interval during the scanning interval, that is, the scanning module inside the sensing chip outputs a low-level driving signal, so that the levels of SGND and GND are approximately equal, and the SPI module inside the sensing chip is at this time. It can communicate normally with the SPI module of the main control module.
  • the fingerprint recognition sensor further includes a resistor array 270.
  • the sensor chip is connected to the main control module through the resistor array 270.
  • the resistors in the resistor array 270 may be a series resistor, an upper pull-down resistor, a pull-up TVS tube, or the like.
  • the voltage on the communication line may be high voltage (5.6V in this example, which is high voltage compared to 2.8V), which may cause potential damage to the communication interface. 270 can avoid this problem, its resistance value is about 20 ⁇ 2000 ohms, depending on the actual situation.
  • the resistor array 270 can also be omitted, and the sensor chip is directly connected to the main control module through a wire.
  • the conversion circuit 230 modulates the driving signal (that is, when the signal of SGND is modulated into a square wave signal)
  • the communication interface such as the SPI interface in this embodiment
  • the power supply 260 is connected to the sensor chip through a controllable power switch 280, and the main control module controls the opening (opening or opening) of the power switch 280, thereby controlling the power supply of the conversion circuit 230 and the sensor chip.
  • the sensor chip turns off or turns off the power switch 280 when the modulation is idle, reducing system power consumption.
  • the reset RST pin of the sensor chip is also modulated to cause an external reset abnormality.
  • the power switch 280 can be controlled to re-power the sensor chip. Implement a reset.
  • the power switch 280 may be composed of a transistor or/and a field effect transistor, and may be a single component or a plurality of combinations, for example, may be composed of a PMOS transistor.
  • a low-dropout linear regulator can be connected between the SVDD of the sensor chip and the storage capacitor to improve the stability of the power supply of the sensor chip.
  • FIG. 6 shows a second embodiment of the fingerprint recognition sensor of the present invention.
  • the difference between this embodiment and the first embodiment is that the sensor chip is connected to the main control module of the terminal device through a relay block.
  • the relay module has two SPI interfaces, SPI-A and SPI-B.
  • the SPI-A interface is connected to the SPI interface of the sensor chip
  • the SPI-B interface is connected to the SPI interface of the central control module (of course, other communication interfaces are also available. connection).
  • the relay module receives the data sent by the sensor chip through the SPI-A interface and caches the data, and the main control module acquires data through the SPI-B interface of the relay module.
  • the relay module passes the SPI-B interface according to the command of the main control module. Send the data to the master module.
  • the relay module also receives the command of the main control module, and controls the sensor chip according to the main control command.
  • the main control module needs to receive and process the data of the sensing chip in time during the scanning time interval of the capacitor array (ie, when adjusting the idle interval), and the scanning time interval may be less than 1 ms.
  • the relay module is composed of an MCU (Micro Control Unit), and the MCU has two independent SPI communication interfaces SPI-A and SPI-B.
  • the MCU controls the SPI-A interface to receive the data of the sensor chip and buffer when adjusting the idle interval.
  • the MCU is also responsible for forwarding the commands of the master module to the sensor chip and controlling the SW signal.
  • the relay module may also be any one or at least one of an MCU, an FPGA (Field-Programmable Gate Array), a Flash (Flash), and a FIFO (First In First Out). It consists of two combinations.
  • the opening of the power switch 280 can be controlled by a master module or a relay module.
  • FIG. 7 shows a third embodiment of the fingerprint recognition sensor of the present invention.
  • This embodiment and the second embodiment The difference between the embodiments is that the conversion circuit 230, the high-speed transistor switch 250, the power switch 280 and the relay module are integrated on the same chip, and the fingerprint identification system is mainly composed of two chips, and the peripheral circuit of the chip is more compact to adapt to the small The need for size terminal equipment.
  • FIG. 8 shows a fourth embodiment of the fingerprint recognition sensor of the present invention.
  • the relay module and the sensor unit are integrated together in the sensor chip, thereby further reducing the size of the fingerprint identification system to adapt to small sizes. The needs of terminal equipment.
  • the fingerprint recognition sensor of the invention can work normally without driving the metal ring, so there is no need to open a hole in the surface of the terminal device, and only the sensor is installed in an area under the insulating cover of the device, and the hidden fingerprint sensor technology is realized.
  • IFS technology Invisible Fingerprint Sensor, referred to as IFS technology.
  • FIG. 9 shows an application scenario in which the IFS technology is applied to a smart phone.
  • the smart phone includes a display cover 10, the central portion is a screen display area 20, and the fingerprint recognition sensor 30 is “hidden” under the display cover 10 without A hole is formed in the display cover 10 to accommodate the driving metal ring, so that the design of the display cover 10 is minimally affected, and a full mirror effect can be achieved.
  • the equivalent capacitance formed by the terminal device in series with the capacitance CS of the earth and the capacitance CM of the human body to the earth, and the capacitance CH of the human body directly to the terminal device their attenuation effects on the driving signal will no longer exist.
  • the invention also proposes a terminal device, which comprises a fingerprint recognition sensor, the fingerprint recognition sensor comprises a sensor unit, a conversion circuit, a storage capacitor, a high speed transistor switch and a power source.
  • the sensor unit has an output end, a power supply end and a sensor ground end, and the output end outputs a driving signal;
  • the conversion circuit is connected to the device ground of the terminal device, and the output end of the sensor unit and the sensor ground end, and the driving signal is modulated into a modulation signal and output to the sensor.
  • the storage capacitor is connected between the power supply end and the sensor ground to stabilize the working voltage of the sensor unit; the high speed transistor switch is connected to the power supply end, and the synchronous switch is performed according to the state of the conversion circuit, so that the voltage of the power supply terminal follows the modulation signal.
  • the change is changed; the power supply is connected to the conversion circuit and the power supply terminal of the sensor unit is connected through a high speed transistor switch to supply power to the conversion circuit and the sensor unit.
  • the terminal device of the present invention after the above-mentioned fingerprint recognition sensor is used, it is not necessary to open a hole in the surface to place the driving metal ring, so the design is not affected.
  • the equivalent capacitance of the terminal device to the earth's capacitance CS and the human body to the earth's capacitance CM, and the human body directly to the terminal device Capacitors CH their effects on the attenuation of the drive signal will no longer exist.
  • the larger these capacitors the stronger the coupling, the higher the voltage across Cx, and the clearer the fingerprint image effect, thus improving the fingerprint recognition effect.
  • the invention provides a fingerprint recognition sensor, wherein a high-speed transistor switch and a storage capacitor form a power supply circuit of the sensor unit, and the conversion circuit drives the drive signal outputted by the sensor unit to drive the sensor terminal of the sensor unit. Since the driving signal of the sensor unit is modulated into a modulation signal, when the finger presses the capacitive sensing unit of the sensor unit, the modulated signal forms a loop through the capacitance between the capacitor C X between the finger and the device and the ground of the device of the terminal device. When C X changes, the measured voltage of the capacitive sensing unit of the sensor unit also changes, so that a fingerprint image can be obtained and fingerprint recognition is realized.
  • the fingerprint recognition sensor of the present invention does not need to drive the metal ring, there is no need to open a hole in the surface of the terminal device to place the driving metal ring, so the design of the terminal device is not affected, and can be applied to a mobile phone that does not want to be opened on the screen.
  • Terminal devices such as tablets have expanded the application range of fingerprint recognition sensors.

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Abstract

一种指纹识别传感器和终端设备，指纹识别传感器应用于终端设备，包括：传感器单元（210），包括由多个电容感应单元（211）组成的电容阵列，具有一输出端、供电端（SVDD）和传感器地端（SGND），所述输出端输出驱动信号；转换电路（230），连接终端设备的设备地（GND）以及传感器单元（210）的输出端和传感器地端（SGND），将驱动信号调制为调制信号后输出至传感器地端（SGND）；储能电容（240），连接于供电端（SVDD）和传感器地端（SGND）之间，以稳定传感器单元（210）的工作电压；高速晶体管开关（250），连接供电端（SVDD），根据转换电路（230）的状态进行同步开关，以使供电端（SVDD）的电压随着调制信号的变化而变化；电源（260），连接转换电路（230）以及通过高速晶体管开关（250）连接传感器单元（210）的供电端（SVDD）。

Description

指纹识别传感器和终端设备 技术领域
本发明涉及指纹识别技术领域，尤其是涉及一种指纹识别传感器和终端设备。
背景技术
指纹识别技术广泛应用于电子安防领域，是进行身份认证的一种比较可靠的方法。电容式指纹识别传感器是目前广泛使用的指纹传感器之一，它是由微型化的电容极板阵列构成的，极板的上面覆盖绝缘板，当用户将手指放在绝缘板上时，皮肤就组成了电容阵列的另一个极板。由于不同区域指纹的脊和谷与电容极板阵列之间的距离不相等，使得每个电容极板的电容量随之而变，由此可获得指纹图像。
图1所示为一种常见的电容式指纹识别传感器，包括传感器单元、驱动放大器101、驱动金属环103以及为传感器单元供电的电源(图未示)。传感器单元包括由若干电容感应单元102组成的电容阵列，其中图1中示意性的表示了其中任意一个电容感应单元102。传感器单元输出驱动信号至驱动放大器101，驱动放大器101对驱动信号进行放大处理后输出至驱动金属环103，手指104按压到传感器单元的电容阵列时，手指和电容感应单元102之间耦合电容为CX，驱动信号从金属环103通过电容CT耦合到手指，不同区域指纹的脊和谷与电容感应单元102之间CX不相等，电容感应单元102测量到电压随之变化，由此获得指纹图像。
这种结构的指纹识别传感器，需要外置一个金属环103，而为了尽可能增大电容CT，减小对信号衰减，指纹识别传感器所在区域需要挖空以放置金属环103，让手指能直接触摸到金属环103。然而，对于某些应用场合，如手机、平板的外观设计，为了达到镜面的屏幕效果，提高防水性能，并不希望在显示屏幕上开孔，这就限制了指纹识别传感器的应用范围。
此外，指纹识别传感器搭载的终端设备对大地的电容CS与人体对大地的电容CM相串联形成的等效电容，以及人体直接对设备的电容CH，均会对驱 动金属环103上面的驱动信号产生衰减。当终端设备采用金属外壳，用户手握设备时，衰减会变得更严重，从而降低了指纹图像的清晰程度，影响了指纹识别效果。
发明内容
本发明的主要目的在于提供一种指纹识别传感器和终端设备，旨在扩大指纹识别传感器的应用范围，提高指纹识别效果。
为达以上目的，本发明提出一种指纹识别传感器，指纹识别传感器应用于终端设备，包括：
传感器单元，包括由多个电容感应单元组成的电容阵列，具有一输出端、供电端和传感器地端，输出端输出驱动信号；
调制电路，连接终端设备的设备地、传感器单元的输出端、供电端和传感器地端，将驱动信号调制为调制信号后输出至传感器地端，供电端的电压随着调制信号的变化而变化。
优选地，调制电路包括：
转换电路，连接终端设备的设备地以及传感器单元的输出端和传感器地端，将驱动信号调制为调制信号后输出至传感器地端；
储能电容，连接于供电端和传感器地端之间，以稳定传感器单元的工作电压；
高速晶体管开关，连接供电端，根据转换电路的状态进行同步开关，以使供电端的电压随着调制信号的变化而变化；
电源，连接转换电路以及通过高速晶体管开关连接传感器单元的供电端，为转换电路和传感器单元供电。
优选地，传感器单元通过通信接口连接终端设备的主控模块，传感器单元在调制空闲间隔时输出低电平的驱动信号，使得设备地和传感器地端的电平近似相等。
优选地，传感器单元通过导线直接与主控模块连接，且在转换电路调制驱动信号时保持通信接口为低电平；或者，指纹识别传感器还包括一电阻阵列，传感器单元通过电阻阵列与主控模块连接；或者，指纹识别传感器还包括一中继模块，传感器单元通过中继模块连接终端设备的主控模块。
优选地，当传感器单元通过中继模块与主控模块连接时，中继模块接收 传感器单元发送的数据并缓存，主控模块从中继模块获取数据。
优选地，传感器单元和中继模块集成于一传感芯片。
优选地，电源通过一电源开关与传感器单元连接，主控模块或中继模块控制电源开关的开断。
优选地，转换电路、高速晶体管开关、电源开关和中继模块集成于一芯片中。
优选地，转换电路由晶体管、运算放大器、反相器、电平移位器和数字缓冲门中的任意一种或至少两种的组合以及电阻或/和电容构成。
优选地，转换电路由两反相器和一电阻构成，反相器包括第一反相器和第二反相器；第一反相器的正输入电源端连接传感器单元的供电端，负输入电源端连接设备地，输入端连接传感器单元的输出端以及通过电阻连接第二反相器的负输入电源端和设备地，输出端连接第二反相器的输入端；第二反相器的正输入电源端连接电源，负输入电源端连接设备地，输出端连接传感器地端。
优选地，第一反相器由第一NMOS管、第一PMOS管和第一电阻构成，第一NMOS管和第一PMOS管的栅极互相连接，构成第一反相器的输入端，第一PMOS管的源级作为第一反相器的正输入电源端，第一NMOS管的源级作为第一反相器的负输入电源端，第一NMOS管和第一PMOS管的漏极通过第一电阻连接，第一NMOS管和第一PMOS管的漏级均可以作为第一反相器的输出端；第二反相器由第二NMOS管、第二PMOS管和第二电阻构成，连接关系与第一反相器相同。
优选地，高速晶体管开关由肖特基二极管、快恢复二极管、晶体三极管、场效应管和可控硅中的任意一种或至少两种的组合构成。
优选地，还包括一低压差线性稳压器，低压差线性稳压器连接于供电端和储能电容之间。
本发明同时提出一种终端设备，终端设备包括一指纹识别传感器，指纹识别传感器包括：
传感器单元，包括由多个电容感应单元组成的电容阵列，具有一输出端、供电端和传感器地端，输出端输出驱动信号；
转换电路，连接终端设备的设备地以及传感器单元的输出端和传感器地端，将驱动信号调制为调制信号后输出至传感器地端；
储能电容，连接于供电端和传感器地端之间，以稳定传感器单元的工作电压；
高速晶体管开关，连接供电端，根据转换电路的状态进行同步开关，以使供电端的电压随着调制信号的变化而变化；
电源，连接转换电路以及通过高速晶体管开关连接传感器单元的供电端，为转换电路和传感器单元供电。
本发明所提供的一种指纹识别传感器，由高速晶体管开关和储能电容构成传感器单元的供电电路，由转换电路对传感器单元输出的驱动信号进行调制后驱动传感器单元的传感器地端。由于传感器单元的驱动信号被调制为调制信号，当手指按压传感器单元的电容感应单元时，调制信号通过它与手指之间的电容CX和人体与终端设备的设备地之间的电容形成回路，当CX变化时，传感器单元的电容感应单元的测量电压也随之变化，从而可以获得指纹图像，实现了指纹识别。
由于本发明的指纹识别传感器不需要驱动金属环，因此无需在终端设备的表面开孔来安置驱动金属环，所以不会影响终端设备的外观设计，可以应用于不希望在屏幕上开孔的手机、平板等终端设备，扩大了指纹识别传感器的应用范围。
同时，终端设备对大地的电容CS与人体对大地的电容CM相串联形成的等效电容，以及人体直接对终端设备的电容CH，它们对驱动信号的衰减影响将不复存在。相反地，这些电容越大，耦合越强，Cx两端电压越大，指纹图像效果就越清晰，因此提高了指纹识别效果。
附图说明
图1是现有技术中指纹识别传感器的结构示意图；
图2是本发明的指纹识别传感器的电路结构示意图；
图3是本发明实施例中转换电路的电路连接示意图；
图4是本发明的指纹识别传感器第一实施例的电路连接示意图；
图5是本发明实施例中转换电路工作过程时序图；
图6是本发明的指纹识别传感器第二实施例的电路连接示意图；
图7是本发明的指纹识别传感器第三实施例的电路连接示意图；
图8是本发明的指纹识别传感器第四实施例的电路连接示意图；
图9是本发明的指纹识别传感器应用于手机的示意图。
本发明目的的实现、功能特点及优点将结合实施例，参照附图做进一步说明。
具体实施方式
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。
本发明的指纹识别传感器为电容式指纹识别传感器，可以应用于手机、平板电脑、掌上设备、智能穿戴设备、多媒体播放器、笔记本电脑、台式电脑、门禁安防等终端设备。其中，指纹识别传感器包括传感器单元和调制电路，传感器单元具有由多个电容感应单元组成的电容阵列、输出端、供电端和传感器地端，输出端输出驱动信号；调制电路连接终端设备的设备地、传感器单元的输出端、供电端和传感器地端，将驱动信号调制为调制信号后输出至传感器地端，供电端的电压随着调制信号的变化而变化。
作为本发明的一个实施例，指纹识别传感器如图2所示，传感器单元210，调制电路包括转换电路230、储能电容240、高速晶体管开关250和电源260。传感器单元210具有一输出端、供电端(Sensor VDD，以下简称SVDD)和一传感器地端(Sensor Ground，以下简称SGND)，输出端连接转换电路230；转换电路230连接终端设备的设备地(Ground，以下简称GND)和传感器单元的SGND；高速晶体管开关250连接传感器单元210的SVDD，高速晶体管250可以由肖特基二极管、快恢复二极管、晶体三极管、场效应管和可控硅中的任意一种或至少两种的组合构成，包括单个构成、多个通过串联或/和并联的连接方式构成，或者多种通过串联或/和并联的连接方式构成；电源260连接转换电路230，以及通过高速晶体管250开关连接传感器单元210的SVDD，为转换电路230和传感器单元210供电；储能电容240连接于传感器单元210的SVDD和SGND之间，以稳定传感器单元210的工作电压。其中，高速晶体管开关250和储能电容240构成了传感器单元210的供电电路。
转换电路230可以由晶体管、运算放大器、反相器、电平移位器和数字缓冲门中的任意一种或至少两种的组合并配合电阻或/和电容构成。转换电路230优选如图3所示，由两反相器(231,232)和一电阻R3构成，两反相器包括第一反相器231和第二反相器232。其中，第一反相器231的正输入电源端 连接传感器单元210的SVDD，负输入电源端连接终端设备的GND，输入端连接传感器单元210的输出端以及通过电阻R3连接第二反相器232的负输入电源端和终端设备的GND，输出端连接第二反相器232的输入端；第二反相器232的正输入电源端连接电源260，负输入电源端连接终端设备的GND，输出端连接传感器单元的SGND。
其中，反相器优选由两个晶体管和一个电阻构成，其中晶体管为金属氧化物半导体场效应晶体管(Metal Oxid Semiconductor，以下简称MOS管),包括PMOS管(Positive Channel Metal Oxide Semiconductor，P沟道金属氧化物半导体场效应晶体管)和NMOS管(Negative Channel Metal Oxide Semiconductor，N沟道金属氧化物半导体场效应晶体管)。如图3所示，PMOS管(Q1,Q3)和NMOS管(Q2,Q4)的栅极互相连接，构成反相器(231,232)的输入端，PMOS管(Q1,Q3)的源级作为反相器(231,232)的正输入电源端，NMOS管(Q2,Q4)的源级作为反相器(231,232)的负输入电源端，PMOS管(Q1,Q3)和NMOS管(Q2,Q4)的漏极通过电阻(R1,R2)连接，PMOS管(Q1,Q3)和NMOS管(Q2,Q4)的漏级均可以作为反相器(231,232)的输出端。
传感器单元210包括驱动放大器220和由若干电容感应单元211组成的电容阵列，其中图2中示意性的表示了其中任意一个电容感应单元211。驱动放大器220的输出端作为传感器单元的输出端连接转换电路230，驱动放大器220对传感器单元210的驱动信号进行放大处理后输出至转换电路230，转换电路230将驱动信号调制为调制信号后输出至传感器单元210的SGND，高速晶体管开关250根据转换电路230的状态进行同步开关，以使传感器单元210的SVDD的电压随着调制信号的变化而变化。
终端设备对大地的电容CS与人体对大地的电容CM相串联形成的等效电容，以及人体直接对终端设备的电容CH，会使人体与终端设备的GND之间产生耦合，这种耦合不管在任何应用场景都始终存在。由于传感器单元210的驱动信号被调制为调制信号，当手指按压传感器单元210的电容感应单元211时，调制信号通过它与手指之间的电容CX和人体与终端设备GND之间的电容形成回路，当CX变化时，传感器单元210的电容感应单元211的测量电压也随之变化，从而获得指纹图像。
如图4所示为本发明的指纹识别传感器具体应用的第一实施例。本实施例中传感器单元集成于一传感芯片，该传感芯片包括一扫描模块和串行外设 接口(Serial Peripheral Interface，SPI)模块，扫描模块输出驱动信号以对电容阵列进行扫描，SPI模块提供SPI接口，为传感芯片的通信接口，与终端设备的主控模块的通信接口连接，以通过该通信接口与主控模块进行通信，如传感芯片向主控模块发送指纹图像数据，主控模块向传感芯片发送控制命令等。通信接口除了SPI接口外，还可以是I2C(Inter-Inegrated Circuit)接口和其他串/并行接口等。
转换电路230如图3所示，由四个晶体管和三个电阻构成。其中，晶体管为MOS管,包括PMOS管Q1和Q3，以及NMOS管Q2和Q4，电阻包括R1、R2和R3。
结合参见图4和图5，转换电路的工作原理如下：
传感芯片对电容阵列进行扫描并读取不同电容感应单元的电压，扫描方式由扫描模块(Scan Block)控制，扫描模块输出驱动信号TX，驱动信号TX是高频交流信号，可以是正弦波、方波、三角波等，在本实例中，驱动信号TX为方波信号，频率800kHz，当然也可以是其它频率值。驱动信号TX经过转换电路230调制到SGND，调制信号的峰峰值取决于供电电源260的大小，在本实施例近似等于输入电压2.8V，当然也可以是其它电压值。
传感芯片在调制空闲间隔时驱动信号TX是低电平SGND，驱动信号TX和SVDD压差接近2.8V，PMOS管Q1导通，R1阻值远大于PMOS管Q1、NMOS管Q2的导通内阻，由于电阻R1的存在，无论NMOS管Q2导通或截止，节点TX_S电压都被拉高至SVDD，然后TX_S的SVDD电压将使NMOS管Q4导通，PMOS管Q3截止，此时NMOS管Q4将SGND连接到GND，然后使驱动信号TX维持GND电压，从而NMOS管Q2截止，PMOS管Q1、PMOS管Q3、NMOS管Q4的状态保持不变，SGND的电压维持在GND稳定不变，如图5的波形中阶段1(Stage1)所示。
当驱动信号TX变为高电平时，驱动信号TX和SVDD电压近似相等。此时，PMOS管Q1截止，NMOS管Q2导通，节点TX_S电压都被拉低至GND，然后TX_S的低电压将使PMOS管Q3导通，NMOS管Q4截止，此时PMOS管Q3将SGND强制拉高到2.8V。由于储能电容240两端电压不能突变，近似保持为2.8V，因此SVDD电压将被强制“泵”到大约5.6V，高速晶体管开关250由于反向偏置而自然关断。SVDD电压变为5.6V之后，驱动信号TX和SVDD电压近似相等，因此驱动信号TX电压近似为5.6V，MOS管Q1-Q4 的状态维持不变，SGND电压维持2.8V稳定不变，如图5的波形中阶段2(Stage2)所示。
当驱动信号TX由高电平变为低电平时，驱动信号TX和SGND电压近似相等约为2.8V，此时SVDD电压为5.6V，PMOS管Q1、NMOS管Q2将同时导通，由于电阻R1，TX_S电压近似为SVDD，令NMOS管Q4导通、PMOS管Q1截止，SGND连通GND，之后将重复阶段1的过程。驱动信号TX由高电平变为低电平的过程，如图5的波形中阶段3(Stage3)所示。
上述即为转换电路的工作过程，传感芯片的SGND将被调制到和驱动信号TX同频率同相位的方波波形，调制信号的电压等于电源260供电电压。
传感芯片获得指纹图像数据后，需要将数据传输到终端设备的主控模块，主控模块进行数据处理并识别指纹对象，本实例是采用SPI接口连接指纹传感器芯片和主控模块，通信接口有多种方式实现，不局限于本实例的SPI接口。
转换电路230将SGND调制为交流方波信号时，SPI接口的信号也同时被调制，被调制的SPI信号无法直接被主控模块的SPI模块识别，导致通信异常。但是，由于传感芯片并不是连续不间断的扫描电容阵列，不同的电容感应单元的扫描之间存在时间间隔，大部分情况下这个间隔时间足够大，以至于可以直接利用这个时间间隔进行数据传输。因此，只需要在这个扫描时间间隔内，即调制空闲间隔时，传感芯片内部的扫描模块输出低电平驱动信号，使得SGND和GND的电平近似相等，这时传感芯片内部的SPI模块就能和主控模块的SPI模块正常通信。
进一步地，指纹识别传感器还包括一电阻阵列270，传感芯片通过该电阻阵列270与主控模块连接，电阻阵列270中的电阻可以是串联电阻、上下拉电阻、上下拉TVS管等。当传感芯片的SGND被调制为交流方波时，在通信线上的电压可能为高压(本实例为5.6V，相对于2.8V为高压)，这可能会对通信接口造成潜在伤害，电阻阵列270则可以避免这个问题，其电阻值约为20～2000欧姆，视实际情况而定。
在某些实施例中，电阻阵列270也可以省略，传感芯片直接通过导线与主控模块连接，此时在转换电路230调制驱动信号时(即SGND的信号被调制为方波信号时)，保持通信接口(如本实施例中的SPI接口)为低电平，则通信线上最高电压仅2.8V，避免了上述问题。
进一步地，电源260通过一可控的电源开关280与传感芯片连接，主控模块控制电源开关280的开断(开通或断开)，进而控制转换电路230和传感芯片的电源供电，当传感芯片在调制空闲时关闭或断开电源开关280，降低系统功耗。同时，由于传感芯片的SGND被调制为交流方波时，传感芯片的复位RST引脚也被调制而导致外部复位异常，此时可以通过控制电源开关280，让传感芯片重新上电而实现复位。电源开关280可以由晶体三极管或/和场效应管构成，可以是单个也可以由多个组合构成，例如可以由PMOS管构成。
进一步地，还可以在传感芯片的SVDD和储能电容之间连接一低压差线性稳压器，以提高传感芯片供电的稳定性。
图6所示为本发明的指纹识别传感器的第二实施例，本实施例与第一实施例的区别是，传感芯片通过中继模块(Relay Block)连接终端设备的主控模块。中继模块具有SPI-A和SPI-B两个SPI接口，其中SPI-A接口与传感芯片的SPI接口连接，SPI-B接口与中控模块的SPI接口连接(当然也可以通过其它通信接口连接)。中继模块通过SPI-A接口接收传感芯片发送的数据并缓存，主控模块通过中继模块的SPI-B接口获取数据，例如，中继模块根据主控模块的命令，通过SPI-B接口将数据发送给主控模块。同时，中继模块还接收主控模块的命令，并根据主控命令对传感芯片进行控制。
图4所示的第一实施例中，主控模块需要在电容阵列的扫描时间间隔内(即调整空闲间隔时)及时接收传感芯片的数据并处理，而扫描时间间隔可能不到1ms，对大部分主控系统，这个实时性要求太高难以实现，限制了实用范围。在本实例中，中继模块由MCU(Micro Control Unit，微控制单元)构成，MCU具备两组独立的SPI通信接口SPI-A和SPI-B。MCU控制SPI-A接口在调整空闲间隔时接收传感芯片的数据并缓存，在主控模块空闲时根据主控模块的命令将数据通过SPI-B接口传输到主控模块，这就大大降低了主控模块的实时性要求，提高了实用范围。MCU同时负责转发主控模块对传感芯片的命令，并控制SW信号。此外，中继模块也可以由MCU、FPGA(Field－Programmable Gate Array，现场可编程门阵列)、Flash(闪存)和FIFO(First In First Out，先入先出缓存器)中的任意一种或至少两种的组合所构成。
在存在中继模块的实施例中，可以由主控模块或中继模块来控制电源开关280的开断。
图7所示为本发明的指纹识别传感器的第三实施例，本实施例与第二实 施例的区别是，将转换电路230、高速晶体管开关250、电源开关280和中继模块集成于同一芯片，则指纹识别系统主要由两颗芯片组成，芯片的外围电路更简洁，以适应对小尺寸终端设备的需求。
图8所示为本发明的指纹识别传感器的第四实施例，本实施例将中继模块和传感器单元一起集成于传感芯片，从而可以进一步减小指纹识别系统的尺寸，以适应对小尺寸终端设备的需求。
本发明的指纹识别传感器，不需要驱动金属环便可正常工作，因此无需在终端设备的表面开孔，只需将传感器安装于设备绝缘盖板下的某一区域，实现了隐藏式指纹传感器技术(Invisible Fingerprint Sensor，简称IFS技术)。如图9显示了IFS技术应用于智能手机的应用场景，智能手机包括一显示屏盖板10，中央部分为屏幕显示区域20，指纹识别传感器30则“隐藏”于显示屏盖板10下面，无需在显示屏盖板10上开孔来安置驱动金属环，因此对显示屏盖板10的外观设计影响很小，能实现完整镜面的屏幕效果。
另外，终端设备对大地的电容CS与人体对大地的电容CM相串联形成的等效电容，以及人体直接对终端设备的电容CH，它们对驱动信号的衰减影响将不复存在。相反地，这些电容越大，耦合越强，Cx两端电压越大，指纹图像效果就越清晰。从而解决了设备金属壳衰减驱动信号，造成指纹信号清晰度下降的问题。
本发明同时提出一种终端设备，终端设备包括一指纹识别传感器，指纹识别传感器包括传感器单元、转换电路、储能电容、高速晶体管开关和电源。传感器单元具有一输出端、供电端和传感器地端，输出端输出驱动信号；转换电路连接终端设备的设备地以及传感器单元的输出端和传感器地端，将驱动信号调制为调制信号后输出至传感器地端；储能电容连接于供电端和传感器地端之间，以稳定传感器单元的工作电压；高速晶体管开关连接供电端，根据转换电路的状态进行同步开关，以使供电端的电压随着调制信号的变化而变化；电源连接转换电路以及通过高速晶体管开关连接传感器单元的供电端，为转换电路和传感器单元供电。本实施例中所描述的指纹识别传感器为本发明中上述实施例所涉及的指纹识别传感器，在此不再赘述。
本发明的终端设备，采用上述指纹识别传感器后，无需在表面开孔来安置驱动金属环，所以不会影响外观设计。同时，终端设备对大地的电容CS与人体对大地的电容CM相串联形成的等效电容，以及人体直接对终端设备的 电容CH，它们对驱动信号的衰减影响将不复存在。相反地，这些电容越大，耦合越强，Cx两端电压越大，指纹图像效果就越清晰，因此提高了指纹识别效果。
以上参照附图说明了本发明的优选实施例，并非因此局限本发明的权利范围。本领域技术人员不脱离本发明的范围和实质，可以有多种变型方案实现本发明，比如作为一个实施例的特征可用于另一实施例而得到又一实施例。凡在运用本发明的技术构思之内所作的任何修改、等同替换和改进，均应在本发明的权利范围之内。
工业实用性
本发明所提供的一种指纹识别传感器，由高速晶体管开关和储能电容构成传感器单元的供电电路，由转换电路对传感器单元输出的驱动信号进行调制后驱动传感器单元的传感器地端。由于传感器单元的驱动信号被调制为调制信号，当手指按压传感器单元的电容感应单元时，调制信号通过它与手指之间的电容CX和人体与终端设备的设备地之间的电容形成回路，当CX变化时，传感器单元的电容感应单元的测量电压也随之变化，从而可以获得指纹图像，实现了指纹识别。
由于本发明的指纹识别传感器不需要驱动金属环，因此无需在终端设备的表面开孔来安置驱动金属环，所以不会影响终端设备的外观设计，可以应用于不希望在屏幕上开孔的手机、平板等终端设备，扩大了指纹识别传感器的应用范围。
同时，终端设备对大地的电容CS与人体对大地的电容CM相串联形成的等效电容，以及人体直接对终端设备的电容CH，它们对驱动信号的衰减影响将不复存在。相反地，这些电容越大，耦合越强，Cx两端电压越大，指纹图像效果就越清晰，因此提高了指纹识别效果。

Claims (15)

  1. 一种指纹识别传感器，应用于终端设备，包括：
    传感器单元，包括由多个电容感应单元组成的电容阵列，具有一输出端、供电端和传感器地端，所述输出端输出驱动信号；
    调制电路，连接所述终端设备的设备地、所述传感器单元的输出端、供电端和传感器地端，将所述驱动信号调制为调制信号后输出至所述传感器地端，所述供电端的电压随着所述调制信号的变化而变化。
  2. 如权利要求1所述的指纹识别传感器，其中，所述调制电路包括：
    转换电路，连接所述终端设备的设备地以及所述传感器单元的输出端和传感器地端，将所述驱动信号调制为调制信号后输出至所述传感器地端；
    储能电容，连接于所述供电端和所述传感器地端之间，以稳定所述传感器单元的工作电压；
    高速晶体管开关，连接所述供电端，根据所述转换电路的状态进行同步开关，以使所述供电端的电压随着所述调制信号的变化而变化；
    电源，连接所述转换电路以及通过所述高速晶体管开关连接所述传感器单元的供电端，为所述转换电路和传感器单元供电。
  3. 根据权利要求2所述的指纹识别传感器，其中，所述传感器单元通过通信接口连接所述终端设备的主控模块，所述传感器单元在调制空闲间隔时输出低电平的驱动信号，使得所述设备地和所述传感器地端的电平近似相等。
  4. 根据权利要求3所述的指纹识别传感器，其中，
    所述传感器单元通过导线直接与所述主控模块连接，且在所述转换电路调制所述驱动信号时保持所述通信接口为低电平；或者，
    所述指纹识别传感器还包括一电阻阵列，所述传感器单元通过所述电阻阵列与所述主控模块连接；或者，
    所述指纹识别传感器还包括一中继模块，所述传感器单元通过所述中继模块连接所述终端设备的主控模块。
  5. 根据权利要求4所述的指纹识别传感器，其中，当所述传感器单元通过所述中继模块与所述主控模块连接时，所述中继模块接收所述传感器单元发送的数据并缓存，所述主控模块从所述中继模块获取所述数据。
  6. 根据权利要求5所述的指纹识别传感器，其中，所述传感器单元和所述中继模块集成于一传感芯片中。
  7. 根据权利要求3所述的指纹识别传感器，其中，所述电源通过一电源开关与所述传感器单元连接，所述主控模块控制所述电源开关的开断。
  8. 根据权利要求5所述的指纹识别传感器，其中，所述电源通过一电源开关与所述传感器单元连接，所述主控模块或中继模块控制所述电源开关的开断。
  9. 根据权利要求8所述的指纹识别传感器，其中，所述转换电路、所述高速晶体管开关、所述电源开关和所述中继模块集成于一芯片中。
  10. 根据权利要求2-9任一项所述的指纹识别传感器，其中，所述转换电路由晶体管、运算放大器、反相器、电平移位器和数字缓冲门中的任意一种或至少两种的组合以及电阻或/和电容构成。
  11. 根据权利要求10所述的指纹识别传感器，其中，所述转换电路由两反相器和一电阻构成，所述反相器包括第一反相器和第二反相器；所述第一反相器的正输入电源端连接所述传感器单元的供电端，负输入电源端连接所述设备地，输入端连接所述传感器单元的输出端以及通过所述电阻连接所述第二反相器的负输入电源端和所述设备地，输出端连接所述第二反相器的输入端；所述第二反相器的正输入电源端连接所述电源，负输入电源端连接所述设备地，输出端连接所述传感器地端。
  12. 根据权利要求11所述的指纹识别传感器，其中，所述第一反相器由第一NMOS管、第一PMOS管和第一电阻构成，所述第一NMOS管和第一PMOS管的栅极互相连接，构成第一反相器的输入端，所述第一PMOS管的源级作为第一反相器的正输入电源端，所述第一NMOS管的源级作为第一反相器的负输入电源端，所述第一NMOS管和第一PMOS管的漏极通过所述第一电阻连接，所述第一NMOS管和第一PMOS管的漏级均可以作为第一反相器的输出端；所述第二反相器由第二NMOS管、第二PMOS管和第二电阻构成，连接关系与所述第一反相器相同。
  13. 根据权利要求2-9任一项所述的指纹识别传感器，其中，所述高速晶体管开关由肖特基二极管、快恢复二极管、晶体三极管、场效应管和可控硅中的任意一种或至少两种的组合构成。
  14. 根据权利要求2-9任一项所述的指纹识别传感器，其中，还包括一低压差线性稳压器，所述低压差线性稳压器连接于所述供电端和储能电容之间。
  15. 一种终端设备，包括如权利要求1-14任一项所述的指纹识别传感器。
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US20180211083A1 (en) 2018-07-26
US9965667B2 (en) 2018-05-08
KR20160106734A (ko) 2016-09-12
CN104573649B (zh) 2019-04-02
CN104573649A (zh) 2015-04-29
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US10152626B2 (en) 2018-12-11

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