CN107491774B - Fingerprint sensor and driving method thereof - Google Patents
Fingerprint sensor and driving method thereof Download PDFInfo
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- CN107491774B CN107491774B CN201710920212.5A CN201710920212A CN107491774B CN 107491774 B CN107491774 B CN 107491774B CN 201710920212 A CN201710920212 A CN 201710920212A CN 107491774 B CN107491774 B CN 107491774B
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- 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
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Abstract
The invention discloses a fingerprint sensor and a driving method thereof. The fingerprint sensor includes: a chip; a driving element for emitting an ultrasonic signal when turned on; the piezoelectric element is arranged on one surface of the chip and used for converting ultrasonic signals reflected by a target finger into electric charge; the pixel units are arranged in an array mode and comprise sensing electrodes, and the sensing electrodes are electrically connected with the piezoelectric elements; and each signal detection circuit is electrically connected with the corresponding sensing electrode, is used for detecting the charge quantity on the sensing electrode and outputs an electric signal corresponding to fingerprint information. The effects of simplifying the manufacturing process of the fingerprint sensor and reducing the power consumption are achieved.
Description
Technical Field
The embodiment of the invention relates to a fingerprint sensor technology, in particular to a fingerprint sensor and a driving method thereof.
Background
With the development of science and technology, the application of the fingerprint sensor is more and more extensive.
At present, the fingerprint identification function is built in the bottom of a screen, the fingerprint sensor needs to reach the penetrating power of 400um chemically strengthened glass, and a noise signal generates relatively large interference on an image under the size, so the signal penetrating power of the capacitive fingerprint sensor is limited by the thickness of the screen glass. The ultrasonic fingerprint sensor has strong penetrating power, and is provided with an ultrasonic transmitting element and an ultrasonic receiving element, so that the positions of fingerprint ridges and valleys can be distinguished. The existing ultrasonic technology uses a piezoelectric element array as an ultrasonic receiving unit, and typically uses a piezoelectric ceramic array as an ultrasonic receiving unit, for example.
However, the conventional array-type ultrasonic receiving unit needs to manufacture a piezoelectric unit array, which is generally a physical device, and the manufacturing process of the piezoelectric unit array is difficult, mass production is not easy, and the power consumption of the conventional fingerprint sensor is also large.
Disclosure of Invention
The invention provides a fingerprint sensor and a driving method thereof, which aim to reduce the process difficulty of the existing fingerprint sensor manufacturing process and solve the problems of high manufacturing process difficulty, high power consumption and difficult mass production of the existing fingerprint sensor.
In a first aspect, embodiments of the present invention provide a fingerprint sensor. The fingerprint sensor includes:
a chip;
a driving element for emitting an ultrasonic signal when turned on;
the piezoelectric element is arranged on one surface of the chip and used for converting ultrasonic signals reflected by a target finger into electric charge;
the pixel units are arranged in an array mode and comprise sensing electrodes, and the sensing electrodes are electrically connected with the piezoelectric elements;
and each signal detection circuit is electrically connected with the corresponding sensing electrode, is used for detecting the charge quantity on the sensing electrode and outputs an electric signal corresponding to fingerprint information.
In a second aspect, an embodiment of the present invention further provides a driving method for driving a fingerprint sensor provided in any embodiment of the present invention, where the driving method includes:
when the signal detection circuit does not output an electric signal corresponding to fingerprint information, the driving element is closed;
when the signal detection circuit outputs an electric signal corresponding to fingerprint information, the driving element is started;
and receiving the electric signal output by the signal detection circuit.
According to the fingerprint sensor provided by the embodiment of the invention, the piezoelectric element is an integral piece, the logical ultrasonic signal receiving unit is formed, the ultrasonic signal is received, the electric charge is generated, and the generated electric charge is respectively transmitted to each sensing electrode, so that the fingerprint detection is realized.
Drawings
Fig. 1a is a schematic structural diagram of a fingerprint sensor according to an embodiment of the present invention.
Fig. 1b is a top view of a pixel unit in a fingerprint sensor according to an embodiment of the present invention.
Fig. 2 is a schematic structural diagram of another fingerprint sensor provided in an embodiment of the present invention.
Fig. 3 is a schematic circuit diagram of a fingerprint sensor according to an embodiment of the present invention.
Fig. 4a is a schematic diagram of another integration circuit according to an embodiment of the present invention.
Fig. 4b is a schematic diagram of another integration circuit according to an embodiment of the present invention.
Fig. 5a is a schematic diagram of another charge generation circuit according to an embodiment of the present invention.
Fig. 5b is a schematic diagram of another charge generation circuit according to an embodiment of the present invention.
Fig. 6 is a schematic circuit diagram of another fingerprint sensor according to an embodiment of the present invention.
Fig. 7 is a schematic circuit diagram of another fingerprint sensor according to an embodiment of the present invention.
Fig. 8a is a schematic diagram of another compensation circuit according to an embodiment of the present invention.
Fig. 8b is a schematic diagram of another compensation circuit according to an embodiment of the present invention.
Fig. 9 is a graph illustrating output voltage characteristics of an integration circuit according to an embodiment of the present invention.
Fig. 10 is a flowchart of a driving method for driving a fingerprint sensor according to any of the embodiments of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.
Fig. 1a is a schematic structural diagram of a fingerprint sensor according to an embodiment of the present invention, and referring to fig. 1a, the fingerprint sensor specifically includes:
a chip 100;
a driving element 200 for emitting an ultrasonic signal when turned on;
a piezoelectric element 300 disposed on one surface of the chip 100, for converting an ultrasonic signal reflected by a target finger into an electric charge amount;
a plurality of pixel units arranged in an array, each pixel unit including a sensing electrode 410, the sensing electrode 410 being disposed on the surface of the chip 100 and located between the piezoelectric element 300 and the chip 100, each sensing electrode 410 being electrically connected to the piezoelectric element 300;
at least one signal detection circuit 500, wherein the signal detection circuit 500 may be located on the surface of the chip 100, and each signal detection circuit 500 is electrically connected to the corresponding sensing electrode 410, and is configured to detect an amount of charge on the sensing electrode 410 and output an electrical signal corresponding to fingerprint information.
The driving element 200 may include an on state and an off state, and in the on state, the driving element 200 serves as an ultrasonic signal transmitting unit to transmit an ultrasonic signal; in the off state, the driving element 200 does not emit an ultrasonic signal.
Fig. 1b is a top view of a pixel unit in a fingerprint sensor according to an embodiment of the present invention. Referring to fig. 1a and 1b, the piezoelectric element 300 may be an integral piece, and may be disposed on the surface of the chip 100 as a piezoelectric cover plate, that is, as an ultrasonic signal receiving unit, covering the surface of the chip 100. The amount of charge generated by the piezoelectric element 300 is related to the mechanical shock energy received by the piezoelectric element 300. The piezoelectric element 300 is used in cooperation with the driving element 200, the driving element 200 transmits an ultrasonic signal, such as an ultrasonic beam, to the finger waiting detection target, and the piezoelectric element 300 receives the ultrasonic signal reflected by the finger waiting detection target and generates electric charges through acoustic vibration.
Illustratively, when a finger presses the surface of the fingerprint sensor, the driving element 200 emits an ultrasonic beam to the finger, the ultrasonic beam is reflected to the piezoelectric element by the finger, the piezoelectric element 300 generates charges, and since the material of the piezoelectric element 300 is insulating, the charges generated by the piezoelectric element 300 are transmitted along the first direction in the figure, i.e. along the y-axis direction in fig. 1a, i.e. are conductive along the first direction, but are not transmitted along the second direction, i.e. along the x-axis direction in fig. 1a, i.e. are non-conductive along the second direction, and the piezoelectric element 300 forms a plurality of ultrasonic signal receiving units logically. The ultrasonic signal receiving units in logic generate vibration to generate electric charges after receiving the ultrasonic signals, the electric charges generated by the piezoelectric element 300 are related to the mechanical vibration energy received by the piezoelectric element 300, and the electric charges generated by the piezoelectric element 300 are correspondingly changed along with the texture change of the fingerprint surface due to different energies contained in the ultrasonic waves reflected by the ridge lines and the valley lines of the finger, namely, the ultrasonic signal receiving units in logic generate corresponding electric charges along with the texture of the corresponding fingerprint surface. Each logical ultrasonic wave receiving unit transmits the generated electric charge to each sensing electrode 410, that is, each logical ultrasonic wave receiving unit corresponds to one sensing electrode 410, and transmits the electric charge generated by the logical ultrasonic wave receiving unit to the corresponding sensing electrode 410.
The signal detection circuit 500 may detect the amount of charge on each of the sensing electrodes 410, and read out an electrical signal corresponding to fingerprint information.
Specifically, the working principle of the fingerprint sensor is as follows: when a finger to be detected touches the fingerprint sensor, the driving element 200 transmits an ultrasonic signal in an on state, the piezoelectric element 300 forms a plurality of ultrasonic signal receiving units logically, the ultrasonic signal reflected by the finger is received, the received ultrasonic signal vibrates to generate charges, the charge amount generated by the piezoelectric element 300 is related to the mechanical vibration energy received by the piezoelectric element 300, and the charges generated by the piezoelectric element 300 generate corresponding changes along with the texture change of the fingerprint surface due to different energies contained in the ultrasonic waves reflected by the ridge line and the valley line of the finger. Since the sensing electrodes 410 are electrically connected to the piezoelectric element 300, the electric charges generated by the ultrasonic receiving units are respectively transmitted to the sensing electrodes 410, the signal detection circuit is electrically connected to each sensing electrode 410, and the signal detection circuit 500 detects the amount of electric charges on each sensing electrode 410 and outputs an electric signal corresponding to fingerprint information.
According to the fingerprint sensor provided by the scheme, the piezoelectric element is an integral piece, the plurality of ultrasonic signal receiving units in logic are formed, ultrasonic signals reflected by a finger waiting for detection targets are received, electric charges are generated, the generated electric charges are transmitted to the sensing electrodes respectively, fingerprint detection is realized, compared with a piezoelectric ceramic array formed in the prior art, only one integral piezoelectric element needs to be formed, the process difficulty is greatly reduced, the sensing electrodes can be formed through a semiconductor film forming process, the process is relatively simple, the problems that the process difficulty of the existing ultrasonic sensor is high, the mass production is difficult are solved, and the effect of simplifying the manufacturing process of the ultrasonic sensor is achieved.
Illustratively, the fingerprint sensor may also operate in the following modes: since each pixel unit includes the sensing electrode 410, the surface of the object to be detected, such as a finger, forms an object electrode, and the sensing electrode 410 and the object electrode form an object capacitance therebetween. When a finger presses on the surface of the fingerprint sensor, the size of a target capacitance in the fingerprint sensor is related to the distance d of the texture of the fingerprint surface, according to the capacitance formula C ═ epsilon S/4 pi kd where d is the distance between the texture of the finger surface and the sensing electrode 410, the target capacitance formed by the distance d being smaller when the sensing electrode 410 forms the target capacitance with the ridge line of the fingerprint surface is larger, and the target capacitance formed by the distance d being larger when the sensing electrode 410 forms the target capacitance with the valley line of the fingerprint surface is smaller. Thus, the sensing electrode 410 and the valley line of the fingerprint surface form a target capacitance, and the sensing electrode 410 and the ridge line of the fingerprint surface form a target capacitance, so that the charges on the sensing electrode 410 are changed, the target capacitance is electrically connected with the signal detection circuit 500, the signal detection circuit 500 detects the corresponding charges, and it is determined that a finger is pressed on the surface of the fingerprint sensor. At this time, the driving element 200 may be turned on. The ultrasonic beam generated by the driving element 200, the piezoelectric element 300 receives the ultrasonic wave reflected by the target finger, and generates electric charges, and the electric charges generated by the piezoelectric element 300 are correspondingly changed along with the texture change of the fingerprint surface. Since the sensing electrodes 410 are electrically connected to the piezoelectric element 300, the electric charges generated by the ultrasonic receiving units are transmitted to the sensing electrodes 410, the signal detection circuit 500 is electrically connected to each sensing electrode 410, and the signal detection circuit 500 detects the amount of electric charges on each sensing electrode 410 and outputs an electric signal corresponding to fingerprint information.
For example, the fingerprint sensor provided by the embodiment of the present invention may include a control unit configured to turn off the driving element 200 when the signal detection circuit 500 is not detected to output an electrical signal corresponding to the fingerprint information (when no finger presses the surface of the fingerprint sensor), turn off the driving element 200 when the signal detection circuit 500 is detected to output an electrical signal corresponding to the fingerprint information (when a finger presses the surface of the fingerprint sensor), where the signal may be weak, and then control the driving element 200 to be turned on. The driving element 200 emits an ultrasonic beam, the ultrasonic beam is reflected by a target finger, after the piezoelectric element receives a reflected ultrasonic signal, the piezoelectric element generates charges corresponding to fingerprint information, since the sensing electrodes 410 are electrically connected with the piezoelectric element 300, the charges generated by each ultrasonic receiving unit are respectively transmitted to each sensing electrode 410, the signal detection circuit 500 detects the magnitude of the charge on each sensing electrode 410, and outputs an electric signal corresponding to the fingerprint information. When the finger waits for the detection target to leave the fingerprint sensor, the signal detection circuit 500 does not output any more electric signal, and the control unit controls to turn off the driving element 200. The fingerprint sensor provided by the embodiment of the present invention may also receive a control instruction from an external control unit, for example, an external MCU, and turn on or turn off the driving element 200 according to the control fingerprint of the external control unit.
It can be seen that according to the technical scheme provided by the embodiment of the invention, when a finger waits for a detection target to press the fingerprint sensor, the driving element in the fingerprint sensor can not be started, and when the finger presses the surface of the fingerprint sensor, the driving element is not started at this time, so that the ultrasonic signal is not emitted. The target electrode formed between the sensing electrode and the target finger senses the change of charges on the sensing electrode, then the signal detection circuit detects the charges corresponding to fingerprints on the sensing electrode, it is determined that a finger presses the fingerprint sensor, then the driving element is started, the piezoelectric element receives ultrasonic signals reflected by the target finger, charges are generated and transmitted to the sensing electrode, and then the signal detection circuit detects corresponding charges by checking each sensing electrode, and electric signals corresponding to fingerprint information of the target finger are generated. Have capacitanc fingerprint sensor and ultrasonic wave formula fingerprint sensor's advantage concurrently, when having the finger to press fingerprint sensor's surface, just open drive element moreover, can further reduce fingerprint sensor's consumption.
In addition, when fingerprint detection is carried out, for example, when a finger presses the surface of the fingerprint sensor, a target electrode is formed on the surface of the finger, a target capacitor is formed between the target electrode and the sensing electrode, the electric charge quantity generated by the target capacitor and the electric charge quantity generated by the piezoelectric body are superposed on the sensing electrode, the electric charge superposed on the sensing electrode is output to a signal detection circuit, the electric charge quantity intensity of an output corresponding fingerprint signal is enhanced, and the quality of a figure grabbed by fingerprint identification can be improved.
In addition to the above, the material of the piezoelectric element 300 and/or the driving element 200 is preferably piezoelectric ceramics.
Fig. 2 is an enlarged schematic structural view of a fingerprint sensor according to an embodiment of the present invention, and referring to fig. 2, a passivation layer 101 may be disposed on a chip 100, where the passivation layer is used to protect the chip 100, and a material of the passivation layer 101 may be silicon oxide, silicon nitride, or the like. The passivation layer 101 is disposed on the surface of the chip 100, and covers the sensing electrode 410, a plurality of through holes are disposed on the passivation layer 101, and each sensing electrode 410 is electrically connected to the piezoelectric element 300 through the conductive body 111 in one of the through holes. The material of the conductive body 111 may be nickel. For example, when a finger waits for a detection target to touch the fingerprint sensor, the driving element 200 emits an ultrasonic signal in an on state, and after the finger waits for the detection target to reflect, the piezoelectric element 300 receives the ultrasonic signal reflected by the finger waiting for the detection target, vibrates and generates charges, and the generated charges are conducted to the sensing electrode 410 through the conductive material nickel in the through hole formed in the chip 100.
Fig. 3 is a schematic circuit diagram of a fingerprint sensor according to an embodiment of the present invention. Referring to fig. 3, the piezoelectric element 300 and the sensing electrode 410 form a logic pixel unit 700.
The pixel cell also includes a charge transfer switch 420; referring to fig. 3, the logic pixel unit 700 is respectively connected to the sixth reference voltage 511 and the first terminal of the charge transfer switch 420, the logic pixel unit 700 and the charge transfer switch 420 may form a charge generation circuit 800 for outputting an amount of charge corresponding to a finger fingerprint, the second terminal of the charge transfer switch 420 is connected to the output terminal of the charge generation circuit 800, and the output terminal of the charge generation circuit 800 is connected to the input terminal of the signal detection circuit 500.
With continued reference to fig. 3, the signal detection circuit may include an integration circuit 520, the second port of the charge transfer switch 420 being electrically connected to an input of the integration circuit 520; an integrating circuit 520 for accumulating the charge amount and outputting an electrical signal corresponding to the fingerprint information at an output terminal, the integrating circuit 520 including an amplifier 521, an integrating capacitor 522, and a second reset switch 523; a first input terminal of the amplifier 521 is electrically connected to the input terminal of the integrating circuit 520, an output terminal thereof is electrically connected to the output terminal of the integrating circuit 520, and a second input terminal thereof is used for inputting a third reference voltage 524; a first pole of the integrating capacitor 522 is electrically connected to the first input terminal of the amplifier 521, and a second pole of the integrating capacitor 522 is electrically connected to the output terminal of the amplifier 521; the second reset switch 523 is used to reset the integrating capacitor 522. When the second reset switch 523 is turned on, the levels at both ends of the integration capacitor 522 are the same, and the charge in the integration capacitor 522 is reset and cleared. The signal detection circuit 500 further includes at least one first reset switch 512, a second terminal of each of the charge transfer switches 420 is electrically connected to a corresponding one of the first reset switches 512, a second terminal of the first reset switch 512 is used for inputting a first reference voltage 513, for example, the second terminal of the first reset switch 512 may be grounded.
Fig. 4a is a schematic diagram of another integration circuit according to an embodiment of the present invention, and the integration circuit 520 shown in fig. 4a is different from fig. 3 in that two reset switches are included, a first pole of the integration capacitor 522 is connected to a third reference voltage 524 through a fourth reset switch 525, the third reference voltage 524 is multiplexed with a reference voltage at the second input terminal of the amplifier 521, a second pole of the integration capacitor 522 is connected to a fifth reference voltage 527 through a fifth reset switch 526, and a second pole of the integration capacitor 522 is connected to the output terminal of the amplifier 521 through a follower switch 528, the integration circuit 520 has two operation states, one is an integration state and the other is a reset state, in the integration state, the charge transfer switch 420 and the follower switch 528 are closed, and the fourth reset switch 525 and the fifth reset switch 526 are open. The second is a reset state, in which the charge transfer switch 420 and the follower switch 528 are open, and the fourth reset switch 525 and the fifth reset switch 526 are closed.
Fig. 4b is a schematic diagram of another integration circuit according to an embodiment of the present invention, and the integration circuit 520 shown in fig. 4b is different from the integration circuits shown in fig. 3 and 4a in that a first pole of an integration capacitor 522 is connected to an input terminal of the integration circuit 520 and an output terminal of the integration circuit 520, a second pole of the integration capacitor 522 is connected to ground, and a second pole of the integration capacitor 522, which is well known to those skilled in the art, may also be connected to a reference voltage. The first pole of the integration circuit 520 is connected to the fourth reset switch 525, the fourth reset switch 525 is connected to the third reference voltage 524, and the integration circuit 520 has two operation states, one is that the integration state fourth reset switch 525 is open, and the other is that the integration state fourth reset switch 525 is closed.
Fig. 5a is a schematic diagram of another charge generation circuit according to an embodiment of the present invention. As shown in fig. 5a, a plurality of charge generation circuits form a charge generation array, the plurality of charge generation circuits can use the charge transfer switch 420 and the first reference voltage 513, a similar plurality of charge generation circuits can use the charge transfer switch 420, the charge transfer switch 420 is used as a primary switch, a secondary switch 514 is arranged inside the charge generation circuits, the logic pixel unit 700 is connected to a first end of the secondary switch 514, a second end of the secondary switch 514 is connected to a first end of the charge transfer switch 420, and a second end of the charge transfer switch 420 is connected to an output end.
Fig. 5b is a schematic diagram of another charge generation circuit according to an embodiment of the present invention. As shown in fig. 5b, a plurality of charge generation circuits are connected to bus 515, with bus 515 serving as the output of the plurality of charge generation circuits and the input of the integration circuit.
Fig. 6 is a schematic circuit diagram of another fingerprint sensor according to an embodiment of the present invention. As shown in fig. 6, the signal detection circuit further includes a comparison circuit 530, and the comparison circuit 530 may be a comparator; a first input end of the comparison circuit 530 is electrically connected with an output end of the integration circuit 520, an output end of the comparison circuit is electrically connected with an output end of the signal detection circuit, and a second input end of the comparison circuit is used for inputting a second reference voltage 531; wherein, the integration voltage output by the output terminal of the integration circuit 520 is crossed with the second reference voltage 531 in a way of increasing or decreasing with time; the comparator circuit 530 outputs a time-dependent flipped voltage signal when the integrated voltage crosses the second reference voltage.
Fig. 7 is a schematic circuit diagram of another fingerprint sensor according to an embodiment of the present invention. Referring to fig. 7, the signal detection circuit 500 further includes: a compensation circuit 540, as shown in fig. 7, the compensation circuit 540 is electrically connected to the input terminal of the integration circuit 520, and is configured to inject charges into the integration circuit 520 to adjust the charge accumulation amount of the integration circuit 520, and the compensation circuit 540 includes a compensation switch 541, a compensation capacitor 542, and a third reset switch 543; a first pole of the compensation capacitor 542 is connected to the input terminal of the integrating circuit 520 through the compensation switch 541; the second pole of the compensation capacitor 542 is connected to a level driver 544; a first pole of the compensation capacitor 542 is electrically connected to a first end of the third reset switch 543, and a second end of the third reset switch 543 is used for inputting a fourth reference voltage 545.
Wherein the voltage of the level driver 544 may be variable or fixed.
The compensation capacitor 542 shown in fig. 7 has two operation states, one of which is a reset state, specifically, the third reset switch 543 is closed, the compensation switch 541 is opened, the compensation capacitor 542 is turned on to the level driver 544, and the compensation capacitor 542 is provided with an initial charge amount determined by the capacitance value of the compensation capacitor 542, the driving voltage value of the level driver 544, and the fourth reference voltage 545. In the second compensation state, the compensation switch 541 is closed, and the third reset switch 543 is opened to turn on the compensation capacitor 542 for the integration circuit 520, so that the stored charge in the compensation capacitor 542 is injected into the integration circuit 520 to adjust the integration speed of the integration circuit 520. When the compensation circuit 540 including the capacitor is used to compensate the charge accumulated in the integration circuit 520, it can be seen from the integration process that the charge compensation amount of the compensation circuit 540 is repeatedly injected into the integration circuit 520 for a plurality of times, i.e. the compensation of the integration circuit 520 is discontinuous in time.
Fig. 8a is a schematic diagram of another compensation circuit according to an embodiment of the present invention. Wherein the level driver 544 may also be replaced by a fixed seventh reference voltage 546.
Fig. 8b is a schematic diagram of another compensation circuit according to an embodiment of the present invention, referring to the compensation circuit 540 shown in fig. 8b, which includes a current source 548, the current source 548 is connected to the charge generation circuit 800 and the integration circuit 520 through a compensation switch 541, the charge injection integration circuit 520 of the current source 548 when the compensation switch 541 is closed, and the integration speed of the compensation integration circuit 520 are different from the compensation circuit 540 shown in fig. 7 and fig. 8a, two operation states of the compensation circuit 540 are a compensation state and a reset state, and the charge injection integration circuit 520 of the current source 548 is in the compensation state when the compensation switch 541 is closed. The compensation switch 541 is in a reset state when turned off. When the current source 548 is used to compensate the circuit 540 for the amount of charge accumulated by the integration circuit 520, the integrator may be compensated to be continuous or discontinuous in time according to the integrator process.
The overall operation and principle of operation of the fingerprint sensor incorporating the compensation circuit 540 is described further below.
Referring to the overall circuit of the fingerprint sensor shown in fig. 7, using the charge generation circuit 800, in order to make the charges corresponding to the ridges and valleys of the piezoelectric charge generation circuit form a measurable voltage signal, the output terminal of the piezoelectric charge generation circuit 800 is connected to the input terminal of the integration circuit 520 through the charge transfer switch 420, and the total set of the fingerprint sensor includes:
s1 resets the integrating circuit 520;
s2 reset the charge generation circuit 800, reset the compensation circuit 540;
s3 closes the charge transfer switch 420, opens the first reset switch 512, closes the compensation switch 541;
s4 returns to step S2.
In step S1, in order to ensure the consistency of the measurement, the integrating capacitor 522 needs to be reset in advance before integration, and the resetting process is to make the integrating capacitor 522 have an initial electric quantity, for example, assuming that the reference voltages at the two ends of the integrating capacitor 522 are Vref3 and Vref5, the electric charge quantity of the integrating capacitor 522 after reset is Qrst ═ Vref3-Vref5 × Cr, and Cr is the value of the integrating capacitor 522, in order to simplify the structure of the resetting circuit, the second resetting switch 523 can be directly connected to the two ends of the integrating capacitor 522 (as shown in fig. 3), that is, the electric quantity of the integrating capacitor 522 after reset, Qrst, is 0. The integrating circuit 520 repeats the process of reintegration, that is, the process of charging the integrating capacitor 522 with the electric charge generated by the electric charge generating circuit 800, for a plurality of times. Each time the integration capacitor 522 is charged, the compensation circuit 540 is connected to the integration circuit 520 and the charge generation circuit 800 via the compensation switch 541, and charges are injected into the integration circuit 520.
Step S2 includes: in step S21, the charge generation circuit 800 closes the first reset switch 512 to reset; in step S22, the compensation circuit 540 is reset by opening the compensation switch 541 and closing the third reset switch 543.
In step S3, the charge transfer switch 420 is closed, the charge generation circuit 800 is electrically connected to the integration circuit 520, and the compensation circuit 540 injects charge into the integration circuit 520 to adjust the integrated charge accumulation amount of the integration circuit 520. The output end of the charge generation circuit 800 is connected to the input end of the integration circuit 520 through the charge transfer switch 420, the output end of the integration circuit 520 is connected to the input end of the comparison circuit 530, the output end of the comparison circuit 530 is used as the output of the sensor, and the time T of the comparison circuit 530 outputting the turnover voltage signal reflects the charge amount of the charge generation circuit 800.
When the value of the output voltage of the integrating circuit 520 changes to cross the value of the reference voltage in the comparing circuit 530, the comparing circuit 530 inverts the output signal.
The flip time of the comparator 530 is T ═ qr.end-qr.rst)/Δ Q, where qr.end is the charge amount of the integrating capacitor at the time of flip, qr.rst is the initial charge amount of the integrating capacitor, and is constant for a given fingerprint sensor design (qr.end-qr.rst), while the initialization charge amount of the compensation capacitor 542 is related according to the equation Δ Q. In engineering practice, T is rounded for simplicity and convenience and is output as a result.
Fig. 9 is a graph of output voltage characteristics of an integration circuit according to an embodiment of the present invention, and fig. 9 is a graph of output voltage characteristics of an integration circuit 520, where the abscissa represents voltage units and the ordinate represents time units. The four oblique lines are output voltage characteristic curves of the integrating circuit 520, and the output voltage characteristic curves of the integrator corresponding to the different charge generation circuits 800 are respectively represented as L1, L2, L3, and L4. The horizontal line is a characteristic curve of the second reference voltage 531 of the comparator, and it can be seen from the figure that as the electric charges are accumulated in the integrating capacitor 522, the output voltages (L1, L2, L3, and L4) are continuously decreased and finally cross the horizontal reference voltage, at this time, the output signal of the comparator is inverted, and the time for the crossing to occur differs for different output voltages (L1, L2, L3, and L4), and the crossing time is short, i.e., the voltage is decreased at the ridge line position of the finger, and is long, and the crossing time is slow, i.e., the voltage is decreased at the valley line position of the finger. Meanwhile, the integration process is adjusted by using an adjusting circuit in the integration process of the integrating circuit 520, and positive charges or negative charges are injected into the integrating capacitor 522, so that the integration time of the integrating circuit 520 is correspondingly prolonged/shortened. The charging time used by the integrating capacitor 522 is determined by detecting the inverted output inverted signal of the comparing circuit 530; and finally, the T is used as the system output, and the system output is more linear compared with the system output of the L-Q-T type signal detection circuit 500 in the prior art.
The advantage of the present invention over the prior art is that the compensation circuit 540 injects positive or negative charges into the integration circuit 520 to adjust the integration rate of the integration circuit 520. The adjustment of the charge integration rate to compensate for the mismatch of the integration circuit 520 can be achieved by setting the polarity and rate of charge injection by the charge adjustment circuit.
Fig. 10 is a flowchart of a driving method for driving a fingerprint sensor according to any embodiment of the present invention, the method including:
step 110, turning off the driving element 200 when the signal detection circuit does not output the electric signal corresponding to the fingerprint information; when the signal detection circuit outputs an electrical signal corresponding to fingerprint information, the driving element 200 is turned on;
and step 120, receiving the electrical signal output by the signal detection circuit.
It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.
Claims (6)
1. A fingerprint sensor, comprising:
a chip;
a driving element for emitting an ultrasonic signal when turned on;
the piezoelectric element is arranged on one surface of the chip and used for converting ultrasonic signals reflected by a target finger into electric charge;
the pixel units are arranged in an array mode and comprise sensing electrodes, and the sensing electrodes are electrically connected with the piezoelectric elements;
the signal detection circuit is electrically connected with the corresponding sensing electrode, and is used for detecting the charge amount on the sensing electrode and outputting an electric signal corresponding to fingerprint information; the pixel unit further comprises a charge transfer switch, the piezoelectric element and the sensing electrode form a logic pixel unit, the logic pixel unit is respectively connected with a sixth reference voltage and a first end of the charge transfer switch, the logic pixel unit and the charge transfer switch form a charge generation circuit for outputting the charge amount corresponding to the finger fingerprint, a second end of the charge transfer switch is connected with an output end of the charge generation circuit, and an output end of the charge generation circuit is connected with an input end of the signal detection circuit; the signal detection circuit comprises an integrating circuit; the input end of the integration circuit is electrically connected with the corresponding sensing electrode, and the integration circuit is used for accumulating the electric charge and outputting an electric signal corresponding to fingerprint information at the output end; a first end of the charge transfer switch is electrically connected with the sensing electrode, and a second end of the charge transfer switch is electrically connected with an input end of the integrating circuit;
the signal detection circuit further comprises at least one first reset switch, a second end of each charge transfer switch is correspondingly and electrically connected with one first reset switch, and a second end of each first reset switch is used for inputting a first reference voltage; the signal detection circuit further comprises a comparison circuit;
a first input end of the comparison circuit is electrically connected with an output end of the integration circuit, an output end of the comparison circuit is electrically connected with an output end of the signal detection circuit, and a second input end of the comparison circuit is used for inputting a second reference voltage; the integrating circuit comprises an amplifier, an integrating capacitor and a second reset switch;
the first input end of the amplifier is electrically connected with the input end of the integrating circuit, the output end of the amplifier is electrically connected with the output end of the integrating circuit, and the second input end of the amplifier is used for inputting a third reference voltage;
a first pole of the integrating capacitor is electrically connected with a first input end of the amplifier, and a second pole of the integrating capacitor is electrically connected with an output end of the amplifier; the second reset switch is used for resetting the integrating capacitor; the signal detection circuit further includes:
the compensation circuit is electrically connected with the input end of the integration circuit and is used for injecting charges into the integration circuit so as to adjust the charge accumulation amount of the integration circuit; the compensation circuit comprises a compensation switch, a compensation capacitor and a third reset switch; the first pole of the compensation capacitor is connected with the input end of the integrating circuit through the compensation switch; the second pole of the compensation capacitor is connected with the level driver; a first pole of the compensation capacitor is electrically connected with a first end of the third reset switch, and a second end of the third reset switch is used for inputting a fourth reference voltage;
the working steps of the fingerprint sensor comprise: s1 resets the integrating circuit; the second reset switch is directly connected with two ends of the integrating capacitor, and the electric quantity of the integrating capacitor is equal to 0 after reset;
s2 resetting the charge generation circuit, resetting the compensation circuit, comprising: the charge generation circuit closes the first reset switch to reset; the compensation circuit is reset by opening the compensation switch and closing the third reset switch;
s3 closing the charge transfer switch, opening the first reset switch, and closing the compensation switch; closing the charge transfer switch at step S3, the charge generation circuit being electrically connected to the integration circuit, the compensation circuit injecting charge into the integration circuit and adjusting the integrated charge accumulation amount of the integration circuit; the output end of the charge generation circuit is connected to the input end of the integration circuit through the charge transfer switch, the output end of the integration circuit is connected to the input end of the comparison circuit, the output end of the comparison circuit is used as the output of the sensor, and the time T of the comparison circuit outputting the turnover voltage signal reflects the magnitude of the charge generation amount of the charge generation circuit; when the change of the value of the output voltage of the integrating circuit is crossed with the reference voltage value in the comparison circuit, the comparison circuit inverts the output signal; the flip time of the comparator circuit is T = (qr. end-qr. rst)/Δ Q, where qr.end is the charge amount of the integrating capacitor when the comparator circuit flips, qr.rst is the initial charge amount of the integrating capacitor, and is constant for a given fingerprint sensor design (qr. end-qr. rst), and is related to the compensation capacitor initialization charge amount according to the equation Δ Q; s4 returns to step S2.
2. The fingerprint sensor of claim 1, wherein the chip has through holes, and each of the sensing electrodes is electrically connected to the piezoelectric element through an electrical conductor in the through hole.
3. The fingerprint sensor of claim 2, wherein the conductive body is nickel.
4. The fingerprint sensor of claim 1, wherein the piezoelectric element and/or the driving element is a piezoelectric ceramic.
5. The fingerprint sensor of claim 1, wherein a target capacitance is formed between the sensing electrode and the finger during fingerprint detection, and an amount of charge generated by the target capacitance and an amount of charge generated by the piezoelectric element are superimposed and output to the signal detection circuit.
6. The fingerprint sensor of claim 1, further comprising a control unit configured to turn off the driving element when the signal detection circuit is not detected to output an electrical signal corresponding to the finger information, and turn on the driving element when the signal detection circuit is detected to output an electrical signal corresponding to the finger information.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201710920212.5A CN107491774B (en) | 2017-09-30 | 2017-09-30 | Fingerprint sensor and driving method thereof |
| PCT/CN2018/108702 WO2019062932A1 (en) | 2017-09-30 | 2018-09-29 | Fingerprint sensor and driving method therefor |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201710920212.5A CN107491774B (en) | 2017-09-30 | 2017-09-30 | Fingerprint sensor and driving method thereof |
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| CN107491774B (en) * | 2017-09-30 | 2021-04-27 | 苏州迈瑞微电子有限公司 | Fingerprint sensor and driving method thereof |
| CN109598258B (en) * | 2018-12-30 | 2024-01-30 | 苏州迈瑞微电子有限公司 | Ultrasonic detection circuit, image sensor pixel circuit and signal detection method |
| CN110110691B (en) | 2019-05-16 | 2021-04-02 | 京东方科技集团股份有限公司 | Fingerprint identification driving circuit, fingerprint identification driving device, touch screen and driving method |
| CN112418201A (en) * | 2019-08-22 | 2021-02-26 | 京东方科技集团股份有限公司 | Fingerprint identification module, driving method thereof and display device |
| TWI708235B (en) * | 2019-10-18 | 2020-10-21 | 友達光電股份有限公司 | Pixel sensor circuit |
| KR20210048952A (en) | 2019-10-24 | 2021-05-04 | 삼성전자주식회사 | A method for generating a fingerprint image and a fingerprint sensor |
| CN113038324B (en) * | 2021-03-09 | 2023-08-15 | 维沃移动通信有限公司 | Audio playing method, device and equipment of wireless earphone and readable storage medium |
| CN113920551B (en) * | 2021-09-30 | 2023-02-07 | 深圳市汇顶科技股份有限公司 | Ultrasonic image sensor and related electronic device |
| WO2024011519A1 (en) * | 2022-07-14 | 2024-01-18 | 深圳市汇顶科技股份有限公司 | Ultrasonic fingerprint detection apparatus and electronic equipment |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105264545A (en) * | 2013-06-03 | 2016-01-20 | 高通股份有限公司 | Ultrasonic receiver with coated piezoelectric layer |
| CN105683883A (en) * | 2013-11-04 | 2016-06-15 | 高通股份有限公司 | Piezoelectric force sensing array |
| CN106980411A (en) * | 2017-04-28 | 2017-07-25 | 北京集创北方科技股份有限公司 | Induction installation and driving method |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9945818B2 (en) * | 2014-02-23 | 2018-04-17 | Qualcomm Incorporated | Ultrasonic authenticating button |
| US9195879B1 (en) * | 2014-08-31 | 2015-11-24 | Qualcomm Incorporated | Air/object determination for biometric sensors |
| CN107203739A (en) * | 2017-04-14 | 2017-09-26 | 杭州士兰微电子股份有限公司 | Ultrasonic sensor and its manufacture method |
| CN107491774B (en) * | 2017-09-30 | 2021-04-27 | 苏州迈瑞微电子有限公司 | Fingerprint sensor and driving method thereof |
-
2017
- 2017-09-30 CN CN201710920212.5A patent/CN107491774B/en active Active
-
2018
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105264545A (en) * | 2013-06-03 | 2016-01-20 | 高通股份有限公司 | Ultrasonic receiver with coated piezoelectric layer |
| CN105683883A (en) * | 2013-11-04 | 2016-06-15 | 高通股份有限公司 | Piezoelectric force sensing array |
| CN106980411A (en) * | 2017-04-28 | 2017-07-25 | 北京集创北方科技股份有限公司 | Induction installation and driving method |
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| WO2019062932A1 (en) | 2019-04-04 |
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