A signal sending device, module and equipment for ultrasonic fingerprint recognition

Abstract

Embodiments of the present invention relate to the field of ultrasonic sensors and disclose a signal transmitting device, module, and equipment for ultrasonic fingerprint recognition. The signal transmitting device for ultrasonic fingerprint recognition in the present invention includes: a boost circuit, a control circuit, an oscillation circuit, and an ultrasonic transducer; the boost circuit is configured to increase the power supply voltage to a first voltage based on an input boost clock; the first voltage is the power supply voltage of the control circuit; the control circuit is configured to drive the oscillation circuit to generate a second voltage based on an input control signal; the ultrasonic transducer is configured to generate an ultrasonic signal based on the second voltage; and the boost circuit is further configured to control the input of the boost clock based on the edge detection result of the control signal. This avoids the occurrence of light and dark step-shaped water ripples during the fingerprint recognition process and improves the accuracy of fingerprint recognition.

Description

Technical Field

[0001] The present invention relates to the field of ultrasonic sensors, and in particular to a signal sending device, module and equipment for ultrasonic fingerprint recognition. Background Art

[0002] The ultrasonic signal transmitter uses a set of switches to send pulse signals, stimulating an oscillator circuit to generate a high voltage, which in turn excites a piezoelectric material (e.g., an ultrasonic transducer PMUT) to produce ultrasonic waves. Because the intensity of the ultrasonic waves generated by the piezoelectric material is closely related to the voltage input to the piezoelectric material, the voltage currently generated by the oscillator circuit is insufficient to stimulate the piezoelectric material to produce ultrasonic waves of sufficient signal strength. This, in turn, makes subsequent sampling susceptible to noise interference, affecting the accuracy of fingerprint recognition. Summary of the Invention

[0003] The purpose of the embodiments of the present invention is to provide a signal transmission device, module, and equipment for ultrasonic fingerprint recognition. By providing a boost circuit upstream of a control circuit, the boost circuit increases the control circuit's supply voltage, thereby increasing the second voltage generated by the oscillation circuit, and using the second voltage to increase the ultrasonic signal intensity generated by the ultrasonic transducer. Furthermore, by using the edge detection results of the control signal, the boost clock input of the boost circuit is controlled to output a relatively stable first voltage regardless of whether the boost circuit is loaded or not, thus avoiding the appearance of step-like water ripples that change light and dark during the fingerprint recognition process.

[0004] To solve the above technical problems, an embodiment of the present invention provides a signal sending device for ultrasonic fingerprint recognition, comprising: a boost circuit, a control circuit, an oscillation circuit and an ultrasonic transducer; the boost circuit is used to boost the power supply voltage to a first voltage according to an input boost clock; the first voltage is the power supply voltage of the control circuit; the control circuit is used to drive the oscillation circuit to generate a second voltage according to an input control signal; the ultrasonic transducer is used to generate an ultrasonic signal according to the second voltage; the boost circuit is also used to control the input of the boost clock according to the edge detection result of the control signal.

[0005] An embodiment of the present invention further provides an ultrasonic fingerprint recognition module, comprising: the above-mentioned ultrasonic fingerprint recognition signal sending device.

[0006] An embodiment of the present invention further provides an electronic device, comprising: the above-mentioned ultrasonic fingerprint recognition signal sending device, or the above-mentioned ultrasonic fingerprint recognition module.

[0007] Compared to the prior art, the embodiments of the present invention add a boost circuit upstream of the control circuit and utilize the boost circuit to increase the power supply voltage to a first voltage, thereby increasing the supply voltage of the control circuit and, in turn, increasing the second voltage generated by the oscillation circuit. The second voltage is then utilized to increase the ultrasonic signal intensity generated by the ultrasonic transducer, thereby improving the noise immunity of subsequent sampling signals. Simultaneously, by utilizing the edge detection results of the control signal, the input of the boost clock of the control boost circuit can output a relatively stable first voltage regardless of whether the boost circuit is loaded or not. This avoids the occurrence of light and dark step ripples during the fingerprint recognition process caused by the different voltage values ​​of the first voltage output by the boost circuit when loaded or not, thereby improving the accuracy of fingerprint recognition.

[0008] In addition, the boost circuit includes: a clock control module, a charge pump, an IV conversion module, and a threshold judgment module; the charge pump includes: an output MOS transistor and a proportional mirror MOS transistor connected in parallel with the output MOS transistor; the proportional mirror MOS transistor is connected to the IV conversion module, and the IV conversion module is used to convert the current of the proportional mirror MOS transistor into a third voltage; the threshold judgment module is used to compare the third voltage with a preset threshold and, based on the comparison result, send a control signal for controlling the input of the boost clock to the clock control module.

[0009] In addition, the control circuit includes: an edge detection module; the edge detection module is connected to the threshold judgment module; the edge detection module is used to perform edge detection on the control signal and send the edge detection result to the threshold judgment module; the threshold judgment module sends the control signal for controlling the input of the boost clock to the clock control module based on the edge detection result.

[0010] In addition, the signal sending device for ultrasonic fingerprint recognition further includes: a flying capacitor externally connected to the boost circuit.

[0011] In addition, the charge pump has an H-bridge structure, which is composed of a first NMOS transistor, a second NMOS transistor, a first PMOS transistor, and a second PMOS transistor. The drain of the first PMOS transistor and the drain of the second NMOS transistor are both connected to the power supply voltage, the source of the first NMOS transistor is grounded, the source of the second PMOS transistor is connected to the output capacitor Cp, the source of the first PMOS transistor and the source of the second NMOS transistor, as well as the drain of the first NMOS transistor and the drain of the second PMOS transistor are respectively connected to the flying capacitor Cfly, the substrate of the first NMOS transistor and the substrate of the second NMOS transistor are both grounded, and the substrate of the first PMOS transistor and the substrate of the second PMOS transistor are both connected to the output capacitor Cp; the first PMOS transistor includes a parasitic diode connecting the drain and substrate of the first PMOS transistor, and the parasitic diode is used to increase the first voltage to a reserve voltage value when the power supply voltage is powered on; when the boost circuit is enabled, the first voltage increases from the reserve voltage value to a maximum value, wherein the reserve voltage value is less than the maximum value.

[0012] In addition, the control circuit includes: an edge detection module, a pulse detection module and a logic module; the edge detection module is used to perform edge detection on a single control signal; the pulse detection module is used to perform pulse detection on a single control signal; the logic module is used to determine the control signals and a brake signal for four switching tubes based on the edge detection results and pulse detection results of the single control signal; wherein the control signal of the switching tube is used to control the on and off of the corresponding switching tube, and the brake signal is used to turn off all switching tubes.

[0013] In addition, the oscillation circuit includes: a first capacitor and a first inductor arranged in series, and a second inductor connected in series with the first inductor; the first capacitor and the first inductor together form a first LC resonant circuit; the first inductor and the second inductor connected in series and the second capacitor in the ultrasonic transducer together form a second LC resonant circuit.

[0014] In addition, the first capacitor, the second capacitor, the first inductor, and the second inductor satisfy the following formula: L1×C1=(L1+L2)×C_pmut= ; Wherein, L1 represents the inductance value of the first inductor; L2 represents the inductance value of the second inductor; C1 represents the capacitance value of the first capacitor; C_pmut represents the capacitance value of the second capacitor; π represents pi; f represents the pulse frequency of the control signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] One or more embodiments are exemplarily illustrated by pictures in the corresponding drawings. These exemplifications do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings are represented as similar elements. Unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0016] Figure 1 is a circuit diagram of a signal sending device for ultrasonic fingerprint recognition according to an embodiment of the present invention;

[0017] Figure 2 This is a schematic diagram of the change of the first voltage when water ripples appear in the embodiment of this solution;

[0018] Figure 3 is a schematic diagram of an ideal change of the first voltage according to an embodiment of this solution;

[0019] Figure 4 is a circuit diagram of a signal sending device for ultrasonic fingerprint recognition according to an embodiment of the present solution;

[0020] Figure 5 is a schematic diagram of a corresponding relationship between a control signal and a second voltage according to an embodiment of this solution;

[0021] Figure 6 is a circuit diagram of a charge pump according to an embodiment of the present invention;

[0022] Figure 7 This is a schematic diagram comparing the first voltage charging time according to an embodiment of this solution;

[0023] Figure 8 is a circuit diagram of a signal sending device for ultrasonic fingerprint recognition according to an embodiment of the present solution;

[0024] Figure 9 2 is a circuit diagram of an oscillating circuit according to an embodiment of the present invention. DETAILED DESCRIPTION

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more apparent, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will appreciate that many technical details are provided in the embodiments of the present invention to help readers better understand the present application. However, even without these technical details and the various variations and modifications based on the following embodiments, the technical solutions claimed in the present application can still be implemented.

[0026] The following embodiments are divided for the convenience of description and should not constitute any limitation on the specific implementation of the present invention. The various embodiments can be combined with each other and referenced to each other under the premise of no contradiction.

[0027] The basic principle of ultrasonic fingerprint recognition is to generate a high-voltage signal through a signal transmitter, which is then transmitted to a piezoelectric ultrasonic transducer (PMUT) to generate ultrasonic waves. When the ultrasonic waves encounter the "ridges" and "valleys" of the fingerprint, they produce echoes along different paths. The filtered echo signals are then received, amplified, and processed by the ADC. The AP then performs image processing to generate fingerprint information for fingerprint recognition. Because the piezoelectric conversion of the ultrasonic transducer is related to the voltage level, a higher voltage produces a stronger echo signal. This results in a higher signal-to-noise ratio (SNR) in the subsequent ADC processing, making it less susceptible to noise interference and increasing fingerprint recognition accuracy.

[0028] In order to increase the voltage level of the ultrasonic transducer during piezoelectric conversion, an embodiment of the present invention provides a signal sending device for ultrasonic fingerprint recognition, such as Figure 1 As shown, it includes: boost circuit, control circuit, oscillation circuit ( Figure 1 The dotted box where the LC resonator is located is an oscillation circuit) and an ultrasonic transducer; a boost circuit, used to increase the power supply voltage VDD to a first voltage VDDCP according to the input boost clock; the first voltage is the power supply voltage of the control circuit; the control circuit includes a control logic and a switch tube controlled by the control logic (such as Figure 1 The switch generates two output signals, IND and SWC, according to the input control signal to drive the oscillation circuit to generate the second voltage V TX The ultrasonic transducer is used to generate an ultrasonic signal according to the second voltage. The boost circuit is used to generate the second voltage V TX further improvement.

[0029] The boost circuit can usually increase VDDCP to twice VDD. VDDCP provides power to the two sets of pulse signal output tubes, increasing the voltage of the two sets of pulse output signals IND and SWC, thereby increasing V TX At the same time, in order to ensure the stability of VDDCP, VDDCP can be connected to an external capacitor Cp, which is a voltage stabilization output capacitor (typical value 1uF).

[0030] In addition, since the VDDCP value output by the boost circuit is different when there is a load or not, such as Figure 2 As shown in the figure, the VDDCP voltage value is higher under no-load conditions than under load conditions. Under constant load conditions, the VDDCP voltage value stabilizes at a stable voltage. However, the difference in VDDCP will cause the second voltage VTX generated by the subsequent oscillation circuit to have different values, resulting in the appearance of light and dark stepped water ripples throughout the fingerprint recognition process, which can seriously affect recognition accuracy.

[0031] In order to solve the problem of step water ripples, the embodiment of the present invention proposes that the voltage value of the first voltage VDDCP output by the boost circuit under load or no load is as follows: Figure 3 As shown, the purpose is to make the voltage value basically consistent with or without load, and to keep the voltage value of VDDCP at a stable voltage as much as possible.

[0032] Specifically, the boost circuit includes: a clock control module, a charge pump, an IV conversion module, and a threshold judgment module; the charge pump includes: an output MOS tube and a proportional mirror MOS tube connected in parallel with the output MOS tube; the proportional mirror MOS tube is connected to the IV conversion module, and the IV conversion module is used to convert the current of the proportional mirror MOS tube into a third voltage; the threshold judgment module is used to compare the third voltage with a preset threshold and send a control signal for controlling the input of the boost clock to the clock control module based on the comparison result. Figure 4 The circuit shown is an example, where Figure 4 The second PMOS transistor P2 shown serves as an output MOS transistor, and a corresponding proportional mirror MOS transistor P2M is connected in parallel with the second PMOS transistor P2. When the boost circuit has no load, that is, there is no load or a very light load on VDDCP, the voltage value of the third voltage after IV conversion is low and does not reach the threshold. The threshold judgment module then generates a signal to temporarily stop the boost clock from entering the control module. When the boost circuit load increases, that is, the load on VDDCP increases, the voltage value of the third voltage after IV conversion reaches the threshold. The threshold judgment module then generates a signal to resume the boost clock from entering the control module.

[0033] In addition, if Figure 4 As shown, the control circuit includes an edge detection module connected to a threshold determination module. The edge detection module is configured to perform edge detection on a control signal and transmit the edge detection result to the threshold determination module. Based on the edge detection result, the threshold determination module transmits a control signal for controlling the input of the boost clock to the clock control module. When the edge detection module detects a rising edge, indicating that the load on VDDCP is about to increase, the threshold determination module is immediately controlled to generate a signal to restore the boost clock. Compared to the IV conversion process, directly using edge detection to control the boost clock speeds up the response time and prevents a drop in VDDCP due to the IV conversion and threshold determination modules being slow to respond to the increase in the VDDCP load.

[0034] The control of the boost clock by edge detection and the control of the boost clock by the IV conversion module can be used alone as a method of controlling the stable output of VDDCP, or they can be used together as a method of controlling the stable output of VDDCP.

[0035] The control circuit includes: edge detection module, pulse detection module and logic module ( Figure 4The edge detection module is used to detect the edge of a single control signal; the pulse detection module is used to detect the pulse of the input single control signal; the logic module is used to determine the control signals for the four switch tubes (such as Figure 4 The P0T control signal, N0T control signal, P1T control signal, N1T control signal) and a brake signal are shown; wherein, the control signal of the switch tube is used to control the on and off of the corresponding switch tube, and the brake signal is used to turn off all switch tubes, such as the P0T control signal is used to control the on and off of the switch tube P0T. Single control signal, IND, SWC, brake signal and output V TX The corresponding relationship is as follows Figure 5 As shown in the figure, IND and SWC are pulse signals with opposite phases. The brake signal changes its phase to zero when the first rising edge of the control signal is detected. When the control signal remains zero for a certain period of time, the brake signal is adjusted to 1 to control all switch tubes to be turned off.

[0036] In addition, if Figure 6 As shown, the charge pump adopts an H-bridge structure, which is composed of a first NMOS transistor N1, a second NMOS transistor N2, a first PMOS transistor P1, and a second PMOS transistor P2. The drain of the first PMOS transistor and the drain of the second NMOS transistor are both connected to the power supply voltage, the source of the first NMOS transistor is grounded, the source of the second PMOS transistor is connected to the output capacitor Cp, the source of the first PMOS transistor and the source of the second NMOS transistor, as well as the drain of the first NMOS transistor and the drain of the second PMOS transistor are respectively connected to the flying capacitor Cfly, the substrate of the first NMOS transistor and the substrate of the second NMOS transistor are both grounded, and the substrate of the first PMOS transistor and the substrate of the second PMOS transistor are both connected to the output capacitor Cp. The function of the output capacitor Cp is to stabilize the output first voltage VDDCP. The first PMOS transistor includes a parasitic diode connected to the drain and substrate of the first PMOS transistor. The parasitic diode is used to boost the first voltage to a reserve voltage value when the power supply voltage is turned on. When the boost circuit is enabled, the first voltage is increased from the reserve voltage value to the maximum value, wherein the reserve voltage value is less than the maximum value. The parasitic diode can shorten the boost time and does not need to add any additional pre-charge functional circuit, thus reducing the complexity of the circuit. Figure 7 As shown in the figure, when the parasitic diode D1 is not used, the required charging time is T1, and after the parasitic diode D1 is used, the charging time is shortened to T2. In addition, Figure 7 Where VDD represents the trend of the power supply voltage, VDDCP represents the trend of the first voltage, Figure 7 The figures do not limit the magnitudes of the power supply voltage and the first voltage.

[0037] In addition, in addition to the above-mentioned arrangement of the flying capacitor Cfly in the charge pump H-bridge structure, the flying capacitor Cfly can also be arranged as follows: Figure 8 As shown, a flying capacitor is externally connected to the boost circuit. As an independent external component, the flying capacitor is electrically connected to the boost circuit in the signal transmitting device via a wire. The external flying capacitor Cfly is used to increase the load capacity of the boost circuit while reducing the frequency of the boost clock, thereby reducing the power consumption of the boost circuit itself.

[0038] In addition, if Figure 9 As shown, the oscillation circuit includes: a first capacitor C1 and a first inductor L1 connected in series, and a second inductor L2 connected in series with the first inductor L1; the first capacitor C1 and the first inductor L1 together form a first LC resonant circuit; the first inductor L1 and the second inductor L2 connected in series and the second capacitor C_pmut in the ultrasonic transducer together form a second LC resonant circuit. The first capacitor, the second capacitor, the first inductor and the second inductor satisfy the following formula: L1×C1=(L1+L2)×C_pmut= Where L1 represents the inductance of the first inductor; L2 represents the inductance of the second inductor; C1 represents the capacitance of the first capacitor; C_pmut represents the capacitance of the second capacitor; π represents the circumference of the circle; and f represents the pulse frequency of the control signal. The second LC resonant circuit, formed by utilizing the original second capacitor in the ultrasonic transducer, further increases the voltage received by the ultrasonic transducer.

[0039] Through the above-mentioned setting method, the input of the signal sending device of this scheme only requires a control signal and a clock signal, which can significantly increase the voltage output to the ultrasonic transducer, improve the signal-to-noise ratio and noise resistance of the fingerprint recognition system, and thus improve the recognition accuracy.

[0040] Another feasible embodiment of the present invention relates to an ultrasonic fingerprint recognition module, including: the above-mentioned ultrasonic fingerprint recognition signal sending device.

[0041] Yet another feasible embodiment of the present invention relates to an electronic device, comprising: the above-mentioned ultrasonic fingerprint recognition signal sending device, or the above-mentioned ultrasonic fingerprint recognition module.

[0042] Ultrasonic fingerprint recognition modules are mainly used in smartphones, tablets, smart door locks and other devices for biometric identity authentication, including biometric fingerprint recognition in scenarios such as mobile phone unlocking, mobile payment, and device encryption.

[0043] Compared with the related art, the ultrasonic fingerprint recognition module or electronic device provided by the embodiments of the present invention includes the above-mentioned ultrasonic fingerprint recognition signal sending device. Therefore, it also has the technical effects provided by the aforementioned embodiments and will not be described in detail here.

[0044] An embodiment of the present invention relates to a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the control of the above-mentioned circuit.

[0045] That is, those skilled in the art will understand that all or part of the steps in the above-mentioned embodiments can be implemented by instructing the relevant hardware through a program. The program is stored in a storage medium and includes a number of instructions for causing a device (which may be a single-chip microcomputer, chip, etc.) or a processor to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes: a USB flash drive, a mobile hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk, etc., various media that can store program code.

[0046] Those skilled in the art will appreciate that the above embodiments are specific embodiments for implementing the present invention, and that in actual applications, various changes may be made thereto in form and detail without departing from the spirit and scope of the present invention.

Claims

1. A signal sending device for ultrasonic fingerprint recognition, characterized in that: include: Boost circuit, control circuit, oscillation circuit and ultrasonic transducer; The boost circuit is configured to boost the power supply voltage to a first voltage according to an input boost clock; the first voltage is the power supply voltage of the control circuit; The control circuit is configured to drive the oscillation circuit to generate a second voltage according to an input control signal; The ultrasonic transducer is configured to generate an ultrasonic signal according to the second voltage; The boost circuit is further configured to control the input of the boost clock according to an edge detection result of the control signal; The boost circuit includes: a charge pump; the charge pump is an H-bridge structure, and the H-bridge structure is composed of a first NMOS transistor, a second NMOS transistor, a first PMOS transistor, and a second PMOS transistor. The drain of the first PMOS transistor and the drain of the second NMOS transistor are both connected to the power supply voltage, the source of the first NMOS transistor is grounded, the source of the second PMOS transistor is connected to the output capacitor Cp, the source of the first PMOS transistor and the source of the second NMOS transistor, as well as the drain of the first NMOS transistor and the drain of the second PMOS transistor are respectively connected to a flying capacitor Cfly, the substrate of the first NMOS transistor and the substrate of the second NMOS transistor are both grounded, and the substrate of the first PMOS transistor and the substrate of the second PMOS transistor are both connected to the output capacitor Cp; The first PMOS transistor includes a parasitic diode connected to the drain and substrate of the first PMOS transistor, and the parasitic diode is used to increase the first voltage to a preliminary voltage value when the power supply voltage is powered on; when the boost circuit is enabled, the first voltage increases from the preliminary voltage value to a maximum value, wherein the preliminary voltage value is less than the maximum value; The control circuit includes: an edge detection module, a pulse detection module and a logic module; The edge detection module is used to perform edge detection on a single control signal; The pulse detection module is used to perform pulse detection on the single control signal; The logic module is used to determine control signals and a brake signal for four switching tubes based on the edge detection result and the pulse detection result of the single control signal; wherein the control signal of the switching tube is used to control the on and off of the corresponding switching tube, and the brake signal is used to turn off all switching tubes.

2. The signal transmitting device for ultrasonic fingerprint recognition according to claim 1, characterized in that: The boost circuit includes: a clock control module, a charge pump, an IV conversion module, and a threshold judgment module; The charge pump includes: an output MOS tube, and a proportional mirror MOS tube connected in parallel with the output MOS tube; The proportional mirror MOS tube is connected to the IV conversion module, and the IV conversion module is used to convert the current of the proportional mirror MOS tube into a third voltage; The threshold judgment module is used to compare the third voltage with a preset threshold, and send a control signal for controlling the input of the boost clock to the clock control module according to the comparison result.

3. The signal transmitting device for ultrasonic fingerprint recognition according to claim 2, characterized in that: The control circuit includes: an edge detection module; the edge detection module is connected to the threshold judgment module; The edge detection module is used to perform edge detection on the control signal and send the edge detection result to the threshold judgment module; The threshold determination module sends a control signal for controlling the input of the boost clock to the clock control module according to the edge detection result.

4. The signal transmitting device for ultrasonic fingerprint recognition according to claim 1, characterized in that: Also includes: A flying capacitor is externally connected to the boost circuit.

5. The signal transmitting device for ultrasonic fingerprint recognition according to claim 1, characterized in that: The oscillation circuit comprises: a first capacitor and a first inductor connected in series, and a second inductor connected in series with the first inductor; The first capacitor and the first inductor together form a first LC resonant circuit; The first inductor and the second inductor connected in series together with the second capacitor in the ultrasonic transducer form a second LC resonant circuit.

6. The signal transmitting device for ultrasonic fingerprint recognition according to claim 5, characterized in that: The first capacitor, the second capacitor, the first inductor, and the second inductor satisfy the following formula: <h2 style=";text-align:left;direction:ltr">L1×C1=(L1+L2)×C_pmut=<h2 style=";text-align:left;direction:ltr"> <h2 style=";text-align:left;direction:ltr"> ; Among them, L1 represents the inductance value of the first inductor; L2 represents the inductance value of the second inductor; C1 represents the capacitance value of the first capacitor; C_pmut represents the capacitance value of the second capacitor; π represents pi; and f represents the pulse frequency of the control signal.

7. An ultrasonic fingerprint recognition module, characterized in that: include: A signal sending device for ultrasonic fingerprint recognition according to any one of claims 1 to 6.

8. An electronic device, characterized in that: include: The signal sending device for ultrasonic fingerprint recognition according to any one of claims 1 to 6, or the ultrasonic fingerprint recognition module according to claim 7.

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