A capacitive fingerprint recognition device and an electronic device

Abstract

The present invention discloses a capacitive fingerprint recognition device and an electronic device. The device includes a sensing capacitor and a multi-stage amplification circuit. The sensing capacitor generates a sensing signal based on a driving signal. The multi-stage amplification circuit integrally amplifies the sensing signal. One stage or multiple stages in the multi-stage amplification circuit include: an operational amplifier, a first input capacitor, a second input capacitor, and an integrating capacitor. The inverting input terminal of the operational amplifier is connected to the output terminal of the previous-stage amplification circuit through the first input capacitor, the integrating capacitor is connected between the inverting input terminal and the output terminal of the operational amplifier, the first end of the second input capacitor is connected to the inverting input terminal of the operational amplifier, and the second end of the second input capacitor receives a step signal that is out of phase with the driving signal. The second input capacitor cooperating with the step signal can cancel the DC component brought by the relatively large parasitic capacitance of the dielectric layer above the sensing capacitor, effectively improving the sensing sensitivity of the capacitive fingerprint recognition device.

Description

Technical Field

[0001] Embodiments of the present invention relate to the technical field of capacitive sensors, and in particular, to a capacitive fingerprint recognition device and an electronic device. Background Art

[0002] Capacitive fingerprint sensors are widely used in mobile phones and portable terminal devices to provide security and user convenience. There are depth differences in finger patterns. The convex part is called "ridge", and the concave part is called "valley". When a finger presses the surface of the fingerprint sensor, the distances between the ridges and valleys of the sensed fingerprint and the plates of the sensing capacitor are different, resulting in different coupling capacitances, different changes in the sensing capacitance, different sensing signals output by the sensing capacitance in response to the same excitation signal, and thus a fingerprint image is formed.

[0003] Specifically, the distance from the ridge of the fingerprint to the capacitive sensor is relatively close, and the coupling capacitance formed is larger. Under the same row driving signal, the image information of the valleys and ridges of the fingerprint is converted into different electrical signals. Currently, in order to prevent large electrostatic damage to the fingerprint sensor during repeated touches of the finger on the fingerprint sensor and improve the mechanical strength, it is usually necessary to add a thick non-conductive dielectric layer on the surface of the sensor. However, this part of the dielectric layer brings a large parasitic capacitance, which is superimposed on the coupling capacitance formed by an effective fingerprint press, and the converted electrical signal is amplified by the subsequent readout circuit at the same time. The proportion of the effective fingerprint signal in the total signal is small and is not easily sensed, seriously reducing the sensitivity of the fingerprint sensor. In addition, the noise generated by external large electromagnetic interference will be further superimposed on the readout circuit through the coupling capacitance, reducing the signal-to-noise ratio of the fingerprint signal. Summary of the Invention

[0004] The present invention provides a capacitive fingerprint recognition device and an electronic device, which can effectively remove the fixed DC component in the sensing signal and improve the sensing sensitivity of the fingerprint recognition device.

[0005] In a first aspect, an embodiment of the present invention provides a capacitive fingerprint recognition device, including:

[0006] A sensing capacitor that generates a sensing signal in response to a driving signal; and

[0007] A multi-stage amplifier circuit;

[0008] Among them, one or more stages of the multi-stage amplifier circuit include: an operational amplifier, a first input capacitor, a second input capacitor, and an integration capacitor. The inverting input terminal of the operational amplifier is connected to the output terminal of the previous stage amplifier circuit through the first input capacitor, and the integration capacitor is connected between the inverting input terminal and the output terminal of the operational amplifier; the first terminal of the second input capacitor is connected to the inverting input terminal of the operational amplifier, and the second terminal of the second input capacitor receives a step signal that is out of phase with the drive signal.

[0009] Optionally, the sensing capacitor includes an insulating layer touched by a finger and a plate disposed below the insulating layer. In response to the drive signal applied to the finger, the plate generates the sensing signal.

[0010] Optionally, the sensing capacitor includes a first plate and a second plate. The first plate receives the drive signal, and the second plate outputs the sensing signal.

[0011] Optionally, the first stage of the multi-stage amplifier circuit includes: an operational amplifier, an integration capacitor, and a reset switch. The inverting input terminal of the operational amplifier is connected to the sensing capacitor, and the integration capacitor and the reset switch are connected in parallel between the inverting input terminal and the output terminal of the operational amplifier.

[0012] Optionally, the non-inverting input terminal of the operational amplifier of the multi-stage amplifier circuit receives a reference voltage.

[0013] Optionally, the capacitive fingerprint recognition device further includes an analog-to-digital converter, and the analog-to-digital converter converts the output signal of the multi-stage amplifier circuit into a digital signal.

[0014] Optionally, the capacitive fingerprint recognition device further includes: one or more digital-to-analog converters. The output terminal of the digital-to-analog converter is connected to the second terminal of the second input capacitor of the corresponding stage amplifier circuit for providing the DC voltage signal.

[0015] In a second aspect, the present invention further provides a capacitive fingerprint recognition device, including:

[0016] A sensing capacitor that generates a sensing signal in response to a drive signal;

[0017] A differential operational amplifier;

[0018] A first integration capacitor;

[0019] A second integration capacitor;

[0020] Among them, the first integration capacitor is connected between the inverting input terminal and the non-inverting output terminal of the differential amplifier, and the second integration capacitor is connected between the non-inverting input terminal and the inverting output terminal of the differential amplifier.

[0021] Among them, at the rising edge of the drive signal, one of the inverting input terminal and the non-inverting input terminal is connected to the sensing capacitor; at the falling edge of the drive signal, the other of the inverting input terminal and the non-inverting input terminal is connected to the sensing capacitor.

[0022] Optionally, the capacitive fingerprint recognition device further includes a first operational amplifier, a second operational amplifier, a third integration capacitor, a fourth integration capacitor, a first input capacitor, and a second input capacitor;

[0023] Among them, the third integration capacitor is connected between the inverting input terminal and the output terminal of the first operational amplifier, the fourth integration capacitor is connected between the inverting input terminal and the output terminal of the second operational amplifier, the non-inverting input terminals of the first operational amplifier and the second operational amplifier are connected to a common reference potential, the first input capacitor is connected between the output terminal of the first operational amplifier and the inverting input terminal of the differential amplifier, and the second input capacitor is connected between the output terminal of the second operational amplifier and the non-inverting input terminal of the differential amplifier.

[0024] Among them, at the rising edge of the drive signal, one of the inverting input terminals of the first operational amplifier and the inverting input terminal of the second operational amplifier is connected to the sensing capacitor; at the falling edge of the drive signal, the other of the inverting input terminals of the first operational amplifier and the inverting input terminal of the second operational amplifier is connected to the sensing capacitor.

[0025] Optionally, the capacitive fingerprint recognition device further includes: M drive lines and N sensing lines, the intersection of the drive lines is the sensing capacitor, and each sensing line is connected to the multi-stage amplification circuit;

[0026] The capacitive fingerprint recognition device further includes: a processor and a drive circuit.

[0027] The processor is configured to generate M codes having orthogonality in a predetermined time period, the predetermined time period includes M sub-periods, and each of the codes includes M bits taking a first value or a second value;

[0028] The drive circuit is configured to modulate and generate M drive signals according to the M codes and simultaneously provide the M drive signals to the M drive lines. Among them, when the bit takes the first value, the drive signal has a first pulse in the sub-period corresponding to the bit, and when the bit takes the second value, the drive signal has a second pulse in the sub-period corresponding to the bit.

[0029] In a third aspect, the present invention further provides an electronic device, including the capacitive fingerprint recognition device provided in the first aspect and the second aspect above.

[0030] An embodiment of the present invention provides a capacitive fingerprint recognition device, which includes a sensing capacitor and a multi-stage amplification circuit. The sensing capacitor generates a sensing signal based on a driving signal. One or more stages of the multi-stage amplification circuit include: an operational amplifier, a first input capacitor, a second input capacitor, and an integrating capacitor. The inverting input terminal of the operational amplifier is connected to the output terminal of the previous-stage amplification circuit through the first input capacitor. The integrating capacitor is connected between the inverting input terminal and the output terminal of the operational amplifier. The first end of the second input capacitor is connected to the inverting input terminal of the operational amplifier, and the second end of the second input capacitor receives a step signal that is out of phase with the driving signal. The step signal and the second input capacitor form an adjustable fixed DC component at the integrator output terminal, and the DC component brought by the parasitic capacitor with a larger dielectric layer is canceled. The effective fingerprint signal is amplified multiple times in the multi-stage amplification circuit, effectively improving the sensing sensitivity of the capacitive fingerprint recognition device. Description of the Drawings

[0031] Other features, objects, and advantages of the present invention will become more apparent by reading the detailed description of the non-limiting embodiments with reference to the following drawings:

[0032] Figure 1 Schematic diagram of a capacitive fingerprint recognition device provided by an embodiment of the present invention;

[0033] Figure 2 is Figure 1 Schematic diagram of the sensing pixel in

[0034] Figure 3 Schematic diagram of a readout circuit provided by an embodiment of the present invention;

[0035] Figure 4 Schematic diagram of another readout circuit provided by an embodiment of the present invention;

[0036] Figure 5 Schematic diagram of another readout circuit provided by an embodiment of the present invention;

[0037] Figure 6 Driving timing diagram of the capacitive fingerprint recognition device provided by an embodiment of the present invention;

[0038] Figure 7 Another driving timing diagram of the capacitive fingerprint recognition device provided by an embodiment of the present invention;

[0039] Figure 8 Schematic diagram of the sensing pixel of another capacitive fingerprint recognition device provided by an embodiment of the present invention;

[0040] Figure 9 Schematic block diagram of an electronic device provided by an embodiment of the present invention. Detailed Embodiments

[0041] To further illustrate the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following will, in conjunction with the accompanying drawings and preferred embodiments, elaborate in detail on the specific implementation manners, structures, features and effects of a capacitive fingerprint recognition device and an electronic device proposed according to the present invention.

[0042] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0043] In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention may be implemented in other specific embodiments different from those described herein. Those skilled in the art may make similar extensions without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0044] The present invention provides a capacitive fingerprint recognition device. The capacitive fingerprint recognition device includes, for example, sensing pixels arranged in an array, and each sensing pixel includes a sensing capacitor. The capacitive fingerprint recognition device further includes a driving circuit and a reading circuit. The driving circuit is used to provide a driving signal for the sensing pixels. The sensing capacitor generates a sensing signal in response to the driving signal, and the sensing signal characterizes the magnitude of the coupling capacitor between the sensing capacitor and the finger. The reading circuit includes, for example, a multi-stage amplifier circuit and an analog-to-digital converter. One or more stages of the multi-stage amplifier circuit include: an operational amplifier, a first input capacitor, a second input capacitor, and an integrating capacitor. The inverting input terminal of the operational amplifier is connected to the output terminal of the previous stage amplifier circuit through the first input capacitor, and the integrating capacitor is connected between the inverting input terminal and the output terminal of the operational amplifier. The first end of the second input capacitor is connected to the inverting input terminal of the operational amplifier, and the second end of the second input capacitor receives a step signal having a phase opposite to that of the driving signal. The second input capacitor and the step signal cooperate to cancel out the large DC component brought by the dielectric layer above the sensing pixel.

[0045] Figure 1 is a schematic structural diagram of an exemplary capacitive fingerprint recognition device of the present invention. As Figure 1 shown, the capacitive fingerprint recognition device includes a plurality of driving lines TX, a plurality of sensing lines RX, a driving circuit 200, and a reading circuit 100. The driving lines TX extend along a first direction, the sensing lines RX extend along a second direction, and sensing pixels P are formed at the intersections of the driving lines TX and the sensing lines RX. The sensing pixels P include sensing capacitors C. Figure 1The number of driving lines TX and sensing lines RX therein is only an example. In some embodiments, the driving lines TX and the sensing lines RX are disposed on different layers and separated by an insulating layer, and a sensing capacitor is formed at the intersection of the driving lines TX and the sensing lines RX. For example, the coupling capacitor between the driving line TX1 and the sensing line RX1 is the sensing capacitor of the sensing pixel P11 at the intersection of the driving line TX1 and the sensing line RX1. The driving circuit 200 is configured to provide a driving signal (or a coding signal) to the driving line TX, and the driving signal is, for example, a pulse voltage. In response to the driving signal applied to the driving line TX, a sensing signal is generated on the sensing line RX. The reading circuit 100 is connected to the sensing line RX and is configured to determine the magnitude of the sensing signal.

[0046] Figure 2 is Figure 1 A schematic diagram of the sensing pixel in. The sensing capacitor includes a driving electrode plate 120 and a sensing electrode plate 130. The driving electrode plate 120 and the sensing electrode plate 130 are opposite portions of the driving line TX and the sensing line RX at their intersection. A dielectric layer 140 is disposed above the sensing capacitor, and the dielectric layer 140 can protect the sensing capacitor. When performing fingerprint recognition, the finger 160 touches the dielectric layer 140, and a coupling capacitor Cs is formed between the finger 160 and the sensing electrode plate 130. The coupling capacitor Cs causes the induced charge (i.e., the sensing signal) generated on the sensing electrode plate 130 in response to the driving signal to decrease. The reading circuit 100 can detect the amount of the induced charge. Since the distances from the valleys and ridges of the fingerprint to the driving electrode plate 120 are different, the formed coupling capacitors are different, and the amounts of the induced charges generated on the sensing electrode plate 130 are different. Therefore, according to the amount of the induced charge generated on the sensing electrode plate 130 in response to the driving signal, it can be determined whether the ridge or valley of the fingerprint corresponding to the sensing pixel. As Figure 2 shown, the coupling capacitor Cs between the finger 160 and the sensing electrode plate 130 includes a large DC component brought by the dielectric layer 140, and this DC component does not change whether the dielectric layer 140 contacts the ridge or valley of the fingerprint. Therefore, this DC component affects the sensing sensitivity of the fingerprint recognition device.

[0047] Figure 3 is a schematic diagram of a reading circuit provided by an embodiment of the present invention. As Figure 3 shown, the reading circuit 100 includes a multi-stage amplifier circuit 110 (or a multi-stage integration circuit) and an analog-to-digital converter 150. The multi-stage amplifier circuit 110 integrates and amplifies the induced charge to convert the induced charge into a voltage change (fingerprint signal), and the analog-to-digital converter 150 converts the fingerprint signal output by the multi-stage amplifier circuit 110 into a digital signal. Specifically, Figure 1Each sensing line RX shown in the figure is connected to a combination of a multi-stage amplifier circuit 110 and an analog-to-digital converter 150. In other embodiments, multiple sensing lines RX share a combination of a multi-stage amplifier circuit 110 and an analog-to-digital converter 150, and the input terminal of the multi-stage amplifier circuit 110 is connected to one of the multiple sensing lines RX through a selector. The multi-stage amplifier circuit 110 includes a first-stage amplifier circuit 111, a second-stage amplifier circuit 112, a third-stage amplifier circuit 113, and a fourth-stage amplifier circuit 114. Figure 3 The multi-stage amplifier circuit 110 shown includes a 4-stage amplifier circuit, but the number of stages of the amplifier circuit of the readout circuit of the present invention is not limited to this.

[0048] Among them, the first-stage amplifier circuit 111 includes an operational amplifier A1, an integrating capacitor Cf, and a reset switch S1. The integrating capacitor Cf and the reset switch S1 are connected in parallel between the inverting input and the output terminal of the operational amplifier A1. The inverting input terminal of the operational amplifier A1 is connected to the corresponding sensing line RX, and the non-inverting input terminal of the operational amplifier A1 receives the first reference voltage Vref1. When a driving signal (such as a pulsed voltage of 20V) is applied to the driving line TX, induced charges are generated on the sensing line RX, the reset switch S1 is turned off, and the readout circuit 100 detects the magnitude of the induced charges. The voltage change Δu1 at the output terminal of the first-stage amplifier circuit 111 = Δu·(C s / C f ), where Cs is the coupling capacitor between the finger and the sensing plate 130, and Δu is the driving pulsed voltage. Therefore, the gain of the first-stage amplifier circuit 111 is C s / C f .

[0049] The second-stage amplifier circuit 112 includes an operational amplifier A2, a first input capacitor C1, a second input capacitor C2, and an integrating capacitor C3. The inverting input terminal of the operational amplifier A2 is connected to the output terminal of the first-stage amplifier circuit 111 (the output terminal of the operational amplifier A1) through the first input capacitor C1. The first end of the second input capacitor C2 is connected to the inverting input terminal of the operational amplifier A2, and the second end receives the first step signal DC1 that is out of phase with the driving signal. In Figure 3 the embodiment shown, the first step signal DC1 is provided by the digital-to-analog converter DAC1. The integrating capacitor C3 is connected between the inverting input and the output terminal of the operational amplifier A2, and the non-inverting input terminal of the operational amplifier A2 receives the second reference voltage Vref2. According to the conservation of charge, Δu1·C1 + V1·C2 = Δu2·C3, where Δu2 is the voltage change at the output terminal of the operational amplifier A2, and the gain of the second-stage amplifier circuit 112 is C1 / C3. The second input capacitor C2 and the first step signal DC1 are used to cancel out the large DC component brought by the dielectric layer capacitor.

[0050] The third - stage amplifier circuit 113 includes: an operational amplifier A3, a first input capacitor C4 and a second input capacitor C5, an integrating capacitor C6, and a digital - to - analog converter DAC2. The fourth - stage amplifier circuit 114 includes an operational amplifier A4, a first input capacitor C7 and a second input capacitor C8, an integrating capacitor C9, and a digital - to - analog converter DAC3. As Figure 3 shown, the circuit structures of the third - stage amplifier circuit 113 and the fourth - stage amplifier circuit 114 are similar to that of the second - stage amplifier circuit 112. The gain of the third - stage amplifier circuit 113 is C4 / C6, and the gain of the fourth - stage amplifier circuit 114 is C7 / C9. The second input capacitor C5 and the second input capacitor C8 are also used to cancel the DC capacitance of the dielectric layer. The digital - to - analog converter DAC2 provides a second step signal DC2 for the second input capacitor C5, and the digital - to - analog converter DAC3 provides a third step signal DC3 for the second input capacitor C8. The second DC voltage DC2 and the third step signal DC3 have opposite phases to the drive signal. For example, if the drive signal is a positive pulse voltage, the first step signal DC1, the second step signal DC2, and the third step signal DC3 are negative step voltages. By setting appropriate second input capacitors C2, C5, and C8, and the first step signal DC1, the second step signal DC2, and the third step signal DC3, the large DC component brought by the dielectric - layer capacitance can be cancelled, so that the output signal of the multi - stage amplifier circuit 110 does not contain a large DC component brought by the dielectric - layer capacitance or the large DC component brought by the dielectric - layer capacitance is small. Therefore, the second input capacitors C2, C5, and C8 are also called cancellation capacitors, and the first step signal DC1, the second step signal DC2, and the third step signal DC3 are also called cancellation signals. In this embodiment, the first step signal DC1, the second step signal DC2, and the third step signal DC3 are provided by the digital - to - analog converter. It should be understood that the first step signal DC1, the second step signal DC2, and the third step signal DC3 can also be provided by other circuits, such as a voltage source, and the present invention makes no limitation. In some embodiments, the cancellation capacitors are arranged in the amplifier circuits other than the first stage. For example, the cancellation capacitors are arranged in the second - stage amplifier circuit and each subsequent stage amplifier circuit. The read - out circuit 100 of this embodiment amplifies the sensed signal multiple times, and the DC component of the dielectric layer is cancelled, improving the sensing sensitivity of the fingerprint recognition device.

[0051] Figure 4 is a schematic diagram of another read - out circuit provided by an embodiment of the present invention. As Figure 4As shown. The readout circuit 100 includes a differential operational amplifier A5, integration capacitors C51 and C52. The integration capacitor C51 is disposed between the inverting input terminal and the non-inverting output terminal of the differential operational amplifier A5, and the integration capacitor C52 is disposed between the non-inverting input terminal and the inverting output terminal of the differential operational amplifier A5. At the rising edge of the drive signal, the corresponding sense line RX is connected to the inverting input terminal of the differential operational amplifier A5; at the falling edge of the drive signal, the corresponding sense line RX is connected to the non-inverting output terminal of the differential operational amplifier A5. By using a differential operational amplifier, Figure 4 the readout circuit in

[0052] Figure 5 effectively subtracts large DC components and fixed noise signals, further improving the sensing sensitivity. Figure 5 is a schematic diagram of another readout circuit provided by an embodiment of the present invention. As s shown, the readout circuit 100 includes: a first single-ended operational amplifier A6, a second single-ended operational amplifier A7, integration capacitors C55 and C56, a differential operational amplifier A5, integration capacitors C51 and C52, input capacitors C53 and C54. The integration capacitor C55 is disposed between the inverting input terminal and the output terminal of the first single-ended operational amplifier A6. The integration capacitor C56 is disposed between the inverting input terminal and the output terminal of the second single-ended operational amplifier A7. The non-inverting input terminals of the first single-ended operational amplifier A6 and the second single-ended operational amplifier A7 are commonly connected to a reference voltage Vref. The input capacitor C53 is disposed between the output terminal of the first single-ended operational amplifier A6 and the inverting input terminal of the differential operational amplifier A5, and the input capacitor C54 is disposed between the output terminal of the second single-ended operational amplifier A7 and the non-inverting input terminal of the differential operational amplifier A5. The integration capacitor C51 is disposed between the inverting input terminal of the differential operational amplifier A5 and the non-inverting output terminal VO+, and the integration capacitor C52 is disposed between the non-inverting input terminal of the differential operational amplifier A5 and the inverting output terminal VO-. The corresponding sense line RX is connected to one of the negative input terminals of the first single-ended operational amplifier A6 and the second single-ended operational amplifier A7. For example, at the rising edge of the drive signal, the corresponding sense line RX is connected to the negative input terminal of the first single-ended operational amplifier A6; at the falling edge of the drive signal, the corresponding sense line RX is connected to the negative input terminal of the second single-ended operational amplifier A7. The signal amplified by the first single-ended operational amplifier A6 is Δu1 = Δu·(C 55 / C s ), and the signal amplified by the second single-ended operational amplifier A7 is Δu2 = -Δu·(C 56 / C After passing through the differential operational amplifier A5, the effective fingerprint signal is Figure 5The readout circuit in [it] effectively subtracts large DC components and fixed noise signals, further improving the sensing sensitivity.

[0053] A driving method for a capacitive fingerprint recognition device of the present invention includes: sequentially applying driving signals to a plurality of driving lines TX, that is, scanning the driving lines row by row. During the scanning period of each driving line, a plurality of driving pulses are applied to the driving line. Figure 6 is the driving timing diagram of the capacitive fingerprint recognition device provided by an embodiment of the present invention. As Figure 6 shown, during the scanning period Ta, the driving circuit applies 4 driving pulses to the driving line TX1. During the scanning period Tb, the driving circuit applies 4 driving pulses to the driving line TX2. During the scanning period Tc, the driving circuit applies 4 driving pulses to the driving line TX3. During the scanning period Td, the driving circuit applies 4 driving pulses to the driving line TX4. Correspondingly, during each scanning period, the readout circuit correspondingly obtains 4 sensing signals on each sensing line RX. For example, during the time period Ta, the readout circuit correspondingly obtains 4 sensing signals on the sensing line RX1: V1, V2, V3, and V4. Taking the average value (V1 + V2 + V3 + V4) / 4 of the 4 sensing signals as the sensing result of the sensing pixel at the intersection of the driving line TX1 and the sensing line RX1.

[0054] Another driving method provided by an embodiment of the present invention can be used to drive Figure 1 the capacitive fingerprint recognition device shown. In this driving method, during a predetermined time period T, a plurality of orthogonally encoded driving pulses are simultaneously applied to a plurality of driving lines. Specifically, the predetermined time period T includes a plurality of sub-periods. During each sub-period, a driving pulse is simultaneously applied to a plurality of driving lines, and the number of sub-periods is the same as the number of driving lines. Figure 7 is an exemplary timing diagram of this driving method, taking Figure 1 the capacitive fingerprint recognition device with 4 driving lines and 4 sensing lines shown as an example. During the sub-period T1, the driving pulses applied to the driving lines TX1 - TX4 are A11, A21, A31, and A41, where A11, A21, and A31 are the first pulses and A41 is the second pulse. During the sub-period T2, the driving pulses applied to the driving lines TX1 - TX4 are A12, A22, A32, and A42, where A12, A22, and A42 are the first pulses and A32 is the second pulse. During the sub-period T3, the driving pulses applied to the driving lines TX1 - TX4 are A13, A23, A33, and A43, where A13, A33, and A43 are the first pulses and A23 is the second pulse. During the sub-period T4, the driving pulses applied to the driving lines TX1 - TX4 are A14, A24, A34, and A44, where A24, A34, and A44 are the first pulses and A14 is the second pulse. Figure 7This is another driving timing diagram of the capacitive fingerprint recognition device provided by the embodiments of the present invention. As Figure 7 shown, the first pulse marks the number 1, and the second pulse marks the number -1. In some embodiments, the first pulse and the second pulse have different phases. For example, as Figure 7 shown, the first pulse is a positive pulse and the second pulse is a negative pulse. In other embodiments, the first pulse and the second pulse have the same phase but different pulse heights.

[0055] In each sub-cycle, the signal read out by the readout circuit from each sensing line is the superposition of the sensing signals of 4 sensing pixels. For example, in sub-cycle T1, the signal read out from sensing line RX1 is the superposition of the sensing signals of 4 sensing pixels at the intersection of sensing line RX1 and driving lines TX1 - TX4. When the scanning timing of the entire predetermined time period T is completed, the readout circuit obtains 4 signals from sensing line RX1: V1, V2, V3, and V4. V1, V2, V3, and V4 are the corresponding voltage values after the induction charges Q1, Q2, Q3, and Q4 are integrated. The induction charges Q1, Q2, Q3, and Q4 are the induction charges generated on sensing line RX1 by the driving signals on driving line TX during sub-cycles T1 - T4, respectively. Q1, Q2, Q3, and Q4 satisfy:

[0056]

[0057] A ij (i = 1…4, j = 1…4) represents the driving pulse voltage. For example, A 11 represents the pulse voltage applied to driving line TX1 during sub-cycle T1, A 12 represents the pulse voltage applied to driving line TX1 during sub-cycle T2, A 21 represents the pulse voltage applied to driving line TX2 during sub-cycle T1, A 22 represents the pulse voltage applied to driving line TX2 during sub-cycle T2. C 11 , C 21 , C 31 and C 41 are the coupling capacitors between driving lines TX1 - TX4 and sensing line RX1. According to the above formula, the magnitudes of C 11 , C 11 , C 31 and C 41 can be obtained, and then it can be determined whether the four sensing pixels correspond to the ridges or valleys of the fingerprint. Using a similar method, it can be obtained whether the sensing pixels corresponding to sensing lines RX2 - RX4 correspond to the ridges or valleys of the fingerprint.

[0058] The following describes Figure 7Exemplary method for generating a driving signal of a middle driving method. The capacitive fingerprint recognition device of the present invention includes M sensing lines and N driving lines. The processor of the capacitive fingerprint recognition device is configured to generate M codes having orthogonality over a predetermined time period T. The predetermined time period T includes M sub-periods. Each code includes M bits, each bit corresponding to a sub-period, and the value of each bit is one of a first value and a second value. Taking Figure 1 the 4 sensing lines and 4 driving lines shown as an example, the 4 codes generated by the processor are: (1, 1, 1, -1), (1, 1, -1, 1), (1, -1, 1, 1), and (-1, 1, 1, 1). The driving circuit modulates and generates M driving signals according to the M codes, and provides the M driving signals to the M sensing lines simultaneously over the predetermined time period T. When the bit of the code takes the first value, the driving signal has a first pulse in the sub-period corresponding to the bit, and when the bit of the code takes the second value, the driving signal has a second pulse in the sub-period corresponding to the bit. Over the predetermined time period T, the readout circuit obtains M readout signals from each sensing line RX, and each readout signal is the superposition of the sensing signals of the M sensing pixels associated with the sensing line RX. Since the driving signals on the M driving lines TX are orthogonally coded modulated, the processor can determine the coupling capacitance magnitudes of the M sensing pixels associated with the sensing line RX based on the orthogonal codes and the M readout signals, and further determine whether the fingerprint ridges or valleys correspond to each sensing pixel. This driving method Figure 6 compared with the driving method shown reduces the sensing time of the fingerprint sensor and improves the scanning speed. By using the orthogonal coding method, the influence of noise on the effective fingerprint electrical signal is reduced, and the signal-to-noise ratio is improved.

[0059] Figure 8 is a schematic diagram of a sensing pixel of another capacitive fingerprint recognition device provided by an embodiment of the present invention. As Figure 8 shown, as an example, Figure 8 a sensing pixel is shown in. The sensing pixel includes a sensing electrode plate 170. A dielectric layer 180 is covered on the sensing electrode plate 170. During fingerprint recognition detection, the finger 160 touches the dielectric layer 180, and the finger 160 and the sensing electrode plate 170 form a sensing capacitance. The capacitive fingerprint recognition device further includes a driving circuit 200 and a readout circuit 100. The driving circuit 200 is used to provide a driving signal to the finger, and the driving signal is, for example, a pulsed voltage signal. In response to the driving signal applied to the finger, induced charges are generated on the sensing electrode plate 170. The readout circuit includes, for example, the readout circuit in the above embodiment, such as Figures 3 - 5 the readout circuit shown.

[0060] Figure 9 is a schematic structural diagram of an electronic device provided by an embodiment of the present invention. As Figure 9As shown, the electronic device 10 includes the capacitive fingerprint recognition device 20 provided in any embodiment of the present invention. The electronic device 10 further includes a display screen, and the display screen can be a liquid crystal display (LCD) to an organic light emitting diode (OLED) display screen.

[0061] Since the electronic device 10 provided in this embodiment includes any capacitive fingerprint recognition device 20 provided in the embodiments of the present invention, it has the same or corresponding beneficial effects as the capacitive fingerprint recognition device 20, which will not be elaborated here.

[0062] Note that the above is only the preferred embodiment of the present invention and the technical principles applied. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described here, and various obvious changes, re-adjustments, combinations with each other, and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments. Without departing from the concept of the present invention, it can also include more other equivalent embodiments, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A capacitive fingerprint recognition device, characterized in that, Comprising: A sensing capacitor that generates a sensing signal in response to a driving signal; And A multi-stage amplifier circuit; Including at least two serially-connected integrating amplifier stages; Wherein, each stage of the multi-stage amplifier circuit includes: an operational amplifier, a first input capacitor, a second input capacitor, and an integrating capacitor. The inverting input terminal of the operational amplifier is connected to the output terminal of the previous stage amplifier circuit through the first input capacitor, and the integrating capacitor is connected between the inverting input terminal and the output terminal of the operational amplifier; the first terminal of the second input capacitor is connected to the inverting input terminal of the operational amplifier, and the second terminal of the second input capacitor receives a step signal that is out of phase with the driving signal.

2. The capacitive fingerprint recognition device according to claim 1, wherein The sensing capacitor includes an insulating layer touched by a finger and a plate provided under the insulating layer. In response to the driving signal applied to the finger, the plate generates the sensing signal.

3. The capacitive fingerprint recognition device according to claim 1, wherein The sensing capacitor includes a first plate and a second plate. The first plate receives the driving signal, and the second plate outputs the sensing signal.

4. The capacitive fingerprint recognition device according to claim 1, wherein The first stage of the multi-stage amplifier circuit includes: an operational amplifier, an integrating capacitor, and a reset switch. The inverting input terminal of the operational amplifier is connected to the sensing capacitor, and the integrating capacitor and the reset switch are connected in parallel between the inverting input terminal and the output terminal of the operational amplifier.

5. The capacitive fingerprint recognition device according to claim 4, wherein, The non-inverting input terminal of the operational amplifier of the multi-stage amplifier circuit receives a reference voltage.

6. The capacitive fingerprint recognition device according to claim 1, wherein Further including an analog-to-digital converter that converts the output signal of the multi-stage amplifier circuit into a digital signal.

7. The capacitive fingerprint recognition device according to claim 1, wherein, Further including: One or more digital-to-analog converters. The output terminal of the digital-to-analog converter is connected to the second terminal of the second input capacitor of the corresponding stage amplifier circuit for providing a DC voltage signal.

8. A capacitive fingerprint recognition device, characterized in that, Including: A sensing capacitor that generates a sensing signal in response to a driving signal; A differential operational amplifier; A first integrating capacitor; A second integrating capacitor; Wherein, the first integrating capacitor is connected between the inverting input terminal and the non-inverting output terminal of the differential amplifier, and the second integrating capacitor is connected between the non-inverting input terminal and the inverting output terminal of the differential amplifier. Wherein, at the rising edge of the driving signal, one of the inverting input terminal and the non-inverting input terminal is connected to the sensing capacitor; at the falling edge of the driving signal, the other of the inverting input terminal and the non-inverting input terminal is connected to the sensing capacitor.

9. The capacitive fingerprint recognition device according to claim 8, wherein, Further including a first operational amplifier, a second operational amplifier, a third integrating capacitor, a fourth integrating capacitor, a first input capacitor, and a second input capacitor; Wherein, the third integrating capacitor is connected between the inverting input terminal and the output terminal of the first operational amplifier, the fourth integrating capacitor is connected between the inverting input terminal and the output terminal of the second operational amplifier, the non-inverting input terminals of the first operational amplifier and the second operational amplifier are connected to a common reference potential, the first input capacitor is connected between the output terminal of the first operational amplifier and the inverting input terminal of the differential amplifier, and the second input capacitor is connected between the output terminal of the second operational amplifier and the non-inverting input terminal of the differential amplifier. Wherein, at the rising edge of the driving signal, one of the inverting inputs of the first operational amplifier and the inverting input of the second operational amplifier is connected to the sensing capacitor; at the falling edge of the driving signal, the other of the inverting inputs of the first operational amplifier and the inverting input of the second operational amplifier is connected to the sensing capacitor.

10. The capacitive fingerprint recognition device according to claim 1, characterized in that, The capacitive fingerprint recognition device further includes: M driving lines and N sensing lines, and the intersection of the driving lines and the sensing lines is the sensing capacitor; The capacitive fingerprint recognition device further includes: a processor and a driving circuit, the processor is configured to generate M codes having orthogonality over a predetermined time period, the predetermined time period includes M sub-periods, and each of the codes includes M bits taking a first value or a second value; The driving circuit is configured to modulate and generate M driving signals according to the M codes, and simultaneously provide the M driving signals to the M driving lines, wherein when the bit takes the first value, the driving signal has a first pulse in the sub-period corresponding to the bit, and when the bit takes the second value, the driving signal has a second pulse in the sub-period corresponding to the bit.

11. An electronic device, characterized in that, Including the capacitive fingerprint recognition device according to any one of claims 1-10.

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