Signal sending device, module and equipment for ultrasonic fingerprint identification

Abstract

The embodiment of the invention relates to the field of ultrasonic sensors, and discloses a signal transmitting device, module and equipment for ultrasonic fingerprint identification. The signal transmitting device for ultrasonic fingerprint identification comprises a booster circuit, a control circuit, an oscillating circuit and an ultrasonic transducer, the boosting circuit is used for boosting the power supply voltage into a first voltage according to an input boosting clock; the first voltage is the power supply voltage of the control circuit; the control circuit is used for driving the oscillating circuit to generate a second voltage according to an input control signal; the ultrasonic transducer is used for generating an ultrasonic signal according to the second voltage; and the boost circuit is also used for controlling the input of the boost clock according to the edge detection result of the control signal. Therefore, stepped water ripples with light and shade changes in the fingerprint identification process are avoided. And the accuracy of fingerprint identification is improved.

Description

Technical Field

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

[0002] The ultrasonic signal transmitting device sends a pulse signal through a group of switches to excite an oscillation circuit to generate a relatively high voltage, and then can excite a piezoelectric material (such as an ultrasonic transducer PMUT) to generate ultrasonic waves. Since the intensity of the ultrasonic waves generated by exciting the piezoelectric material is closely related to the voltage input to the piezoelectric material, currently, the magnitude of the voltage generated by the oscillation circuit is not sufficient to excite the piezoelectric material to generate ultrasonic waves with sufficient signal intensity, thereby making the subsequent sampling vulnerable to interference by noise and affecting the accuracy of fingerprint recognition. Summary of the Invention

[0003] An object of an embodiment of the present invention is to provide a signal transmitting device, a module and a device for ultrasonic fingerprint recognition. By arranging a boost circuit in the upstream circuit of the control circuit, the boost circuit is used to increase the supply voltage of the control circuit, thereby increasing the second voltage generated by the oscillation circuit. The second voltage is used to increase the intensity of the ultrasonic signal generated by the ultrasonic transducer. At the same time, by using the edge detection result of the control signal, the input of the boost clock of the boost circuit can be controlled to output a relatively stable first voltage whether there is a load in the boost circuit, so as to avoid the appearance of bright and dark changing stepped water ripples during the fingerprint recognition process.

[0004] To solve the above technical problems, an embodiment of the present invention provides a signal transmitting device for ultrasonic fingerprint recognition, including: a boost circuit, a control circuit, an oscillation circuit and an ultrasonic transducer; the boost circuit is used to increase the power supply voltage to a first voltage according to the input boost clock; the first voltage is the supply voltage of the control circuit; the control circuit is used to drive the oscillation circuit to generate a second voltage according to the input control signal; the ultrasonic transducer is used to generate an ultrasonic signal according to the second voltage; the boost circuit is further 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, including: the above-mentioned signal transmitting device for ultrasonic fingerprint recognition.

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

[0007] Compared with the prior art, in the embodiment of the present invention, a boost circuit is added upstream of the control circuit, and the boost circuit is used to increase the power supply voltage to a first voltage, thereby increasing the supply voltage of the control circuit. Further, the second voltage generated by the oscillation circuit is increased, and the ultrasonic signal intensity generated by the ultrasonic transducer is increased by using the second voltage, improving the anti-interference ability of the subsequent sampling signal to noise. At the same time, by using the edge detection result of the control signal, the input of the boost clock of the boost circuit can output a relatively stable first voltage whether there is a load in the boost circuit or not, avoiding the stepped water ripples of light and dark changes in the fingerprint recognition process caused by different voltage values of the first voltage output by the boost circuit with or without a load, and 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 send a control signal for controlling the input of the boost clock to the clock control module according to the comparison result.

[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 a control signal for controlling the input of the boost clock to the clock control module according to the edge detection result.

[0010] In addition, the signal transmission device for ultrasonic fingerprint recognition further includes: a flying capacitor connected to the boost circuit in an external connection manner.

[0011] In addition, the charge pump is of 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 drains of the first PMOS transistor and 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 sources of the first PMOS transistor and the second NMOS transistor, and the drains of the first NMOS transistor and the second PMOS transistor are respectively connected to the flying capacitor Cfly. The substrates of the first NMOS transistor and the second NMOS transistor are both grounded. The substrates of the first PMOS transistor and the second PMOS transistor are both connected to the output capacitor Cp. The first PMOS transistor includes a parasitic diode connecting the drain and the substrate of the first PMOS transistor, and the parasitic diode is used to boost 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 rises from the preliminary voltage value to the maximum value, where the preliminary 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 control signals for four switching transistors and a braking signal according to the edge detection result and the pulse detection result of the single control signal. Among them, the control signals of the switching transistors are used to control the on / off of the corresponding switching transistors, and the braking signal is used to turn off all the switching transistors.

[0013] In addition, the oscillation circuit includes: 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 series-connected first inductor and second inductor and a 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 = ; where, 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. Description of the Drawings

[0015] One or more embodiments are exemplarily illustrated by the pictures in the corresponding drawings. These exemplary illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are represented as similar elements, unless otherwise stated. The drawings in the figures do not constitute a scale limitation.

[0016] Figure 1 is a circuit diagram of a signal transmitting device for ultrasonic fingerprint recognition according to an embodiment of the present invention; Figure 2 is a schematic diagram showing the change of the first voltage in the case of water ripples according to an embodiment of the present solution; Figure 3 is a schematic diagram showing the ideal change of the first voltage according to an embodiment of the present solution; Figure 4 is a circuit diagram of a signal transmitting device for ultrasonic fingerprint recognition according to an embodiment of the present solution; Figure 5 is a schematic diagram showing the correspondence between a control signal and a second voltage according to an embodiment of the present solution; Figure 6 is a circuit diagram of a charge pump according to an embodiment of the present solution; Figure 7 is a comparison schematic diagram of the charging time of a first voltage according to an embodiment of the present solution; Figure 8 is a circuit diagram of a signal transmitting device for ultrasonic fingerprint recognition according to an embodiment of the present solution; Figure 9 is a circuit diagram of an oscillation circuit according to an embodiment of the present solution. Detailed implementation manners

[0017] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be described in detail below with reference to the drawings. However, those of ordinary skill in the art can understand that in the embodiments of the present invention, many technical details are provided to help readers better understand the present application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solutions claimed in the present application can still be implemented.

[0018] The division of the following embodiments is for convenience of description and should not constitute any limitation on the specific implementation manners of the present invention. The various embodiments can be combined and cross-referenced with each other on the premise of no contradiction.

[0019] The basic principle of ultrasonic fingerprint recognition is that a high-voltage signal is generated by a signal transmission device and transmitted to a piezoelectric ultrasonic transducer PMUT to generate ultrasonic waves. When the ultrasonic waves encounter the "ridges" and "valleys" of the fingerprint, echoes with different paths are generated. The received and amplified and filtered echo signals are processed by an ADC, and the AP performs image processing to generate fingerprint information to achieve fingerprint recognition. Since the piezoelectric conversion of the ultrasonic transducer is related to the voltage magnitude, the higher the voltage, the stronger the echo signal intensity generated. Then, the signal-to-noise ratio of the subsequent ADC processing is higher, it is less likely to be interfered by noise, and the fingerprint recognition accuracy is also higher.

[0020] In order to increase the voltage magnitude during the piezoelectric conversion of the ultrasonic transducer, an embodiment of the present invention provides a signal transmission device for ultrasonic fingerprint recognition, as Figure 1 shown, including: a boost circuit, a control circuit, an oscillation circuit ( Figure 1 the dashed box where the LC resonator is located in Figure 1 is the oscillation circuit) and an ultrasonic transducer; the boost circuit is used to raise 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 control logic and switching transistors controlled by the control logic (such as TX the P0T, N0T, P1T, N1T shown in TX ), and the switching transistors generate two output signals, IND and SWC, according to the input control signal to drive the oscillation circuit to generate a second voltage V

[0021] ; the ultrasonic transducer is used to generate an ultrasonic signal according to the second voltage. It realizes the further increase of the second voltage V TX generated by the oscillation circuit by using the boost circuit.

[0022] In addition, the boost circuit can usually boost VDDCP to twice VDD. VDDCP supplies power to two sets of pulse signal output transistors, increasing the voltages of the two sets of pulse output signals, IND and SWC, thus increasing the V TX voltage. At the same time, in order to ensure the stability of VDDCP, VDDCP can be connected to an external capacitor Cp, and Cp is a voltage stabilizing output capacitor (typical value 1uF).

[0022] In addition, since the VDDCP value output by the boost circuit is different with or without a load, as Figure 2 shown, in the case of no load, the voltage value of VDDCP is higher than that in the case of having a load. In the case of a constant load, the voltage value of VDDCP is stabilized at a stable voltage. And the difference in VDDCP will cause the second voltage VTX generated by the subsequent oscillation circuit to correspond to different values, resulting in stepped water ripples with bright and dark changes during the entire fingerprint recognition process, which will seriously affect the recognition accuracy when severe.

[0023] To solve the problem of stepped water ripples, an embodiment of the present invention proposes to achieve the voltage value of the first voltage VDDCP output by the boost circuit with or without a load as follows Figure 3 shown, with the aim of making the voltage values with or without a load basically the same, and keeping the voltage value of VDDCP as stable as possible.

[0024] 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 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 send a control signal for controlling the input of the boost clock to the clock control module according to the comparison result. Taking Figure 4 the circuit shown as an example, where Figure 4 the second PMOS transistor P2 shown is used as the output MOS transistor, and the 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 small load on VDDCP, the voltage value of the third voltage after IV conversion is low and does not reach the threshold, then the threshold judgment module gives a signal to temporarily stop the boost clock from entering the control module; when the load of the boost circuit increases, that is, the load on VDDCP increases, the voltage value of the third voltage after IV conversion reaches the threshold, then the threshold judgment module gives a signal to resume the boost clock and enter the control module.

[0025] In addition, as Figure 4 shown, 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 according to the edge detection result. When the edge detection module detects a rising edge, it means that the load on VDDCP is about to increase, and immediately controls the threshold judgment module to give a signal to resume the boost clock. Compared with the IV conversion process, directly using edge detection to control the boost clock speeds up the response speed and can prevent VDDCP from dropping due to the slow response of the IV conversion and the threshold judgment module to the increase in the load on VDDCP.

[0026] The above control of the boost clock through edge detection and the control of the boost clock through the IV conversion module can be used alone as a way to control the stable output of VDDCP, or can be detected simultaneously and used together as a way to control the stable output of VDDCP.

[0027] The control circuit includes: an edge detection module, a pulse detection module, and a logic module ( Figure 4the combined logic shown); the 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 switching transistors (such as Figure 4 the P0T control signal, N0T control signal, P1T control signal, N1T control signal shown) and a brake signal; wherein, the control signal of the switching transistor is used to control the on / off of the corresponding switching transistor, and the brake signal is used to turn off all switching transistors, such as the P0T control signal is used to control the on / off of the switching transistor P0T. The correspondence between the single control signal, IND, SWC, brake signal and the output V TX is as shown in Figure 5 wherein, IND and SWC are pulse signals with opposite phases to each other. The brake signal changes the phase position to zero when the first rising edge of the control signal is detected, and when it is detected that the signal of the control signal remains zero for a certain period of time, the brake signal is adjusted to 1 to control all switching transistors to turn off.

[0028] In addition, as shown in Figure 6 , the charge pump adopts an H-bridge structure, and the H-bridge structure 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 drains of the first PMOS transistor and 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 sources of the first PMOS transistor and the second NMOS transistor and the drains of the first NMOS transistor and the second PMOS transistor are respectively connected to the flying capacitor Cfly. The substrates of the first NMOS transistor and the second NMOS transistor are both grounded, and the substrates of the first PMOS transistor and the second PMOS transistor are both connected to the output capacitor Cp; the function of the flying capacitor Cfly is to increase the load-carrying capacity of the boost circuit while reducing the frequency of the boost clock. The function of the output capacitor Cp is to stabilize the output first voltage VDDCP. The first PMOS transistor includes a parasitic diode connecting the drain and the substrate of the first PMOS transistor. The parasitic diode is used to boost 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 rises from the preliminary voltage value to the highest value, wherein the preliminary voltage value is less than the highest value. Using the above parasitic diode can shorten the boost time and does not require additional pre-charge functional circuits, reducing the complexity of the circuit. The charging time of the first voltage VDDCP is compared with that in Figure 7 as shown, when the parasitic diode D1 is not used, the charging time is T1, and after using the parasitic diode D1, the charging time is shortened to T2. In addition, Figure 7 in which VDD represents the trend of the power supply voltage, and VDDCP represents the trend of the first voltage, Figure 7The figure does not limit the magnitudes of the power supply voltage and the first voltage.

[0029] In addition, the setting method of the flying capacitor Cfly, besides being set in the charge pump H-bridge structure as described above, can also be, as Figure 8 shown, a flying capacitor connected to the boost circuit in an external connection manner. The flying capacitor, as an independent external component, is electrically connected to the boost circuit in the signal transmission device through a wire. The flying capacitor Cfly is used to increase the load-carrying capacity of the boost circuit while reducing the frequency of the boost clock, thereby reducing the power consumption of the boost circuit itself.

[0030] In addition, as Figure 9 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 resonance circuit; the series-connected first inductor L1 and second inductor L2 and the second capacitor C_pmut in the ultrasonic transducer together form a second LC resonance 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 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 the pi; f represents the pulse frequency of the control signal. Utilizing the original second capacitor in the ultrasonic transducer to form the second LC resonance circuit further increases the voltage value received by the ultrasonic transducer.

[0031] Through the above setting method, the input of the signal transmission device of the present solution 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 anti-noise ability of the fingerprint recognition system, and thus improve the recognition accuracy.

[0032] Another feasible embodiment of the present invention relates to an ultrasonic fingerprint recognition module, including: the signal transmission device for ultrasonic fingerprint recognition as described above.

[0033] Another feasible embodiment of the present invention relates to an electronic device, including: the signal transmission device for ultrasonic fingerprint recognition as described above, or the ultrasonic fingerprint recognition module as described above.

[0034] The ultrasonic fingerprint recognition module is mainly applied to devices such as smart phones, tablet computers, and smart door locks for biometric identity verification, including the recognition of biological fingerprints in scenarios such as mobile phone unlocking, mobile payment, and device encryption.

[0035] Compared with the related art, the ultrasonic fingerprint recognition module or the electronic device provided by the embodiments of the present invention both include the signal transmission device for ultrasonic fingerprint recognition mentioned above. Therefore, they also have the technical effects provided by the foregoing embodiments, which will not be elaborated here.

[0036] An embodiment of the present invention relates to a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, it implements the control of the above circuit.

[0037] That is, those skilled in the art can understand that all or part of the steps in implementing the methods of the above embodiments can be completed by instructing relevant hardware through a program. The program is stored in a storage medium and includes several instructions for causing a device (which can be a single-chip microcomputer, a chip, etc.) or a processor to execute all or part of the steps of the methods described in the various embodiments of the present application. The foregoing storage medium includes: various media such as USB flash drives, mobile hard disks, read-only memories (ROM, Read-Only Memory), random access memories (RAM, Random Access Memory), magnetic disks, or optical discs that can store program codes.

[0038] Those of ordinary skill in the art can understand that the above embodiments are specific embodiments for implementing the present invention, and in practical applications, various changes can be made in form and details without departing from the spirit and scope of the present invention.

Claims

1. A signal transmission device for ultrasonic fingerprint recognition, characterized in that Comprising: A boost circuit, a control circuit, an oscillation circuit, and a ultrasonic transducer; The boost circuit is configured to boost a power supply voltage to a first voltage according to an input boost clock; the first voltage is the supply voltage for 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.

2. The signal transmitting device for ultrasonic fingerprint recognition according to claim 1, wherein 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 configured to convert the current of the proportional mirror MOS transistor into a third voltage; The threshold judgment module is configured 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 a comparison result.

3. The signal transmission 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 configured to perform edge detection on the control signal, and send the edge detection result to the threshold judgment module; The threshold judgment 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, Further comprising: A flying capacitor connected to the boost circuit in an external connection manner.

5. The signal transmitting device for ultrasonic fingerprint recognition according to claim 1, characterized in that, The boost circuit includes: a charge pump; the charge pump is of 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 drains of the first PMOS transistor and 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 an output capacitor Cp. The sources of the first PMOS transistor and the second NMOS transistor, and the drains of the first NMOS transistor and the second PMOS transistor are respectively connected to a flying capacitor Cfly. The substrates of the first NMOS transistor and the second NMOS transistor are both grounded. The substrates of the first PMOS transistor and the second PMOS transistor are both connected to the output capacitor Cp; The first PMOS transistor includes a parasitic diode connecting the drain and the substrate of the first PMOS transistor. The parasitic diode is configured to boost 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 rises from the preliminary voltage value to the highest value, where the preliminary voltage value is less than the highest value.

6. The signal transmitting device for ultrasonic fingerprint recognition according to claim 1, characterized in that The control circuit includes: an edge detection module, a pulse detection module, and a logic module; The edge detection module is configured to perform edge detection on a single control signal; The pulse detection module is configured to perform pulse detection on the single control signal; The logic module is configured to determine control signals for four switching tubes and a braking signal according to the edge detection result and pulse detection result of the single control signal; wherein, the control signals of the switching tubes are used to control the on / off of the corresponding switching tubes, and the braking signal is used to turn off all the switching tubes.

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

8. The signal transmitting device for ultrasonic fingerprint recognition according to claim 7, characterized in that, 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.

9. An ultrasonic fingerprint recognition module, characterized in that, including: A signal transmitting device for ultrasonic fingerprint identification according to any one of claims 1 to 8.

10. An electronic device, characterized in that, including: A signal transmitting device for ultrasonic fingerprint identification according to any one of claims 1 to 8, or an ultrasonic fingerprint identification module according to claim 9.

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