# US 2018/0025198 A1 · Fingerprint detection circuit and method, electronic device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2018/0025198 A1 - Document ID: US20180025198A1 - Status: Published application - Kind: A1 - Application number: 15/549,896 - Filed: 2016-01-05 - Published: 2018-01-25 - Earliest claimed: 2015-02-13 - Assignees: BYD Company Limited - Applicants: BYD Company Limited - Inventors: Zhengang LI; Kunping XU; Yun YANG - Web page: https://patentgrep.com/patent/US20180025198A1 ## CPC - G06V 40/1306: {non-optical, e.g. ultrasonic or capacitive sensing} - G06V: IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING ## Abstract The present disclosure provides a fingerprint detection circuit and method. The circuit includes a fingerprint collecting module and a processing module. The fingerprint collecting module includes a plurality of collecting units, and each collecting unit has a regulation voltage and is configured to output a first voltage or a second voltage according to a capacitance value of one of ridge capacitors, a capacitance value of one of ridge capacitors and the regulation voltage. The processing module is configured to amplify the first and second voltages by a predetermined factor, to calculate a difference between the amplified first and second voltages, and to determine whether the difference is greater than or equal to the predetermined threshold. If no, the processing module adjusts at least one parameter, and configures the fingerprint detection circuit using at least one adjusted parameter. ## Claims ### Claim 1 A fingerprint detection circuit, configured to apply an excitation signal to a finger so as to generate ridge capacitors and valley capacitors, and comprising: a fingerprint collecting module comprising a plurality of collecting units, wherein each of the plurality of collecting units has a regulation voltage, and is configured to output a first voltage or a second voltage according to a capacitance value of one of the ridge capacitors, a capacitance value of one of the ridge capacitors, and the regulation voltage; and a processing module connected with the fingerprint collecting module, and configured to amplify the first voltage and the second voltage by a predetermined factor, to calculate a difference between art amplified first voltage and an amplified second voltage, and to determine whether the difference is greater than or equal to a predetermined threshold; wherein: when the difference is greater than or equal to the predetermined threshold, the processing module is further configured to calculate the capacitance value of one of the ridge capacitors according to the first voltage, and to calculate the capacitance value of one of the valley capacitors according to the second voltage; and when the difference is less than the predetermined threshold, the processing module is further configured to adjust at least one of an excitation voltage, the predetermined factor and the regulation voltage according to the predetermined threshold and the difference, and to configure the fingerprint collecting module and the processing module using at least one adjusted parameter, in which the excitation voltage is a voltage magnitude of the excitation signal. ### Claim 2 (depends on 1) The fingerprint detection circuit according to claim 1, wherein when the predetermined factor is adjusted, the processing module is further configured to amplify the first voltage and the second voltage by an adjusted predetermined factor, to calculate an adjusted difference between an adjusted value of the amplified first voltage and an adjusted value of the amplified second voltage, and to determine whether the adjusted difference is greater than or equal to the predetermined threshold; and when at least one of the excitation voltage and the regulation voltage is adjusted, or when each of the excitation voltage, the regulation voltage and the predetermined factor is adjusted, the collecting unit is further configured to output a first adjusted voltage or a second adjusted voltage according to the capacitance value of one of the valley capacitors, the capacitance value of one of the ridge capacitors and the adjusted regulation voltage, and the processing module is further configured to amplify the first adjusted voltage and the second adjusted voltage by the predetermined factor or by the adjusted predetermined factor, to calculate the adjusted difference between the amplified value of the first adjusted voltage and the amplified value of the second adjusted voltage, and to determine whether the adjusted difference is greater than or equal to the predetermined threshold. ### Claim 3 (depends on 1) The fingerprint detection circuit according to claim 1, wherein the first voltage has a non-linear relationship with the capacitance value of one of the ridge capacitors, and the second voltage has a non-linear relationship with the capacitance value of one of the valley capacitors. ### Claim 4 (depends on 1) The fingerprint detection circuit according to claim 1, wherein each collecting unit comprises a signal amplifier, a capacitor and a switch unit; the signal amplifier has a negative input terminal connected with one of the ridge capacitors or one of the valley capacitors, a positive input terminal connected with a voltage reference terminal, and an output terminal configured to output the first voltage or the second voltage; and the switch unit is connected with the negative input terminal and the output terminal of the signal amplifier respectively, and is configured to control the capacitor connected between the negative input terminal and the output terminal of the signal amplifier. ### Claim 5 (depends on 4) The fingerprint detection circuit according to claim 4, further comprising a first power supply connected with the capacitor via the switch unit, wherein the switch unit is configured to control the first power supply to charge the capacitor or to control the capacitor to disconnect front the first power supply; and wherein a voltage between two terminals of the capacitor is configured to be the regulation voltage. ### Claim 6 (depends on 4) The fingerprint detection circuit according to claim 4, wherein the reference voltage terminal is a ground terminal. ### Claim 7 (depends on 4) The fingerprint detection circuit according to claim 4, wherein the switch unit comprises a first switch and a second switch; the first switch has a first selecting terminal, a first power terminal and a first connecting terminal, the first selecting terminal is connected with a first terminal of the capacitor, the first power terminal is connected with a first electrode of the first power supply, and the first connecting terminal is connected with the negative input terminal of the signal amplifier; the second switch has a second selecting terminal, a second power terminal and a second connecting terminal, the second selecting terminal is connected with a second terminal of the capacitor, the second power terminal is connected with a second electrode of the first power supply, and the second connecting terminal is connected with the output terminal of the signal amplifier, and the first selecting terminal is configured to be connected with the first connecting terminal or the first power terminal, and the second selecting terminal is configured to be connected with the second connecting terminal or the second power terminal. ### Claim 8 (depends on 7) The fingerprint detection circuit according to claim 7, wherein, when the first selecting terminal is connected with the first connecting terminal and disconnected from the first power terminal, and the second selecting terminal is connected with the second connecting terminal and disconnected from the second power terminal, the capacitor is connected between the negative input terminal and the output terminal of the signal amplifier, and disconnected from the first power supply. ### Claim 9 (depends on 7) The fingerprint detection circuit according to claim 7, wherein, when the first selecting terminal is connected with the first power terminal and disconnected from the first connecting terminal, and the second selecting terminal is connected with the second power terminal and disconnected from the second connecting terminal, the first power supply is configured to charge the capacitor. ### Claim 10 (depends on 4) The fingerprint detection circuit according to claim 4, further comprising a second power supply, wherein; the reference voltage terminal is an output terminal of the second power supply, the switch unit is connected to the capacitor in parallel, and the voltage of the second power supply is configured to be the regulation voltage; when the switch unit is turned off, the capacitor is communicated with the negative input terminal of the signal amplifier and the output terminal of the signal amplifier respectively; and when the switch unit is turned on, the capacitor is disconnected between the negative input terminal and the output terminal of the signal amplifier. ### Claim 11 (depends on 5) The fingerprint detection circuit according to claim 5, wherein the capacitance value of one of the ridge capacitors or the capacitance value of one of the valley capacitors is determined according to a formula of Vo=(Vs−Vt*Cx/Ci), wherein Vo is the first voltage or the second voltage, Vt is the excitation voltage, Cx is the capacitance value of one of the ridge capacitors or the capacitance value of one of the valley capacitors, Ci is the capacitance value of the capacitor, and Vs is the regulation voltage. ### Claim 12 (depends on 1) The fingerprint detection circuit according to claim 1, wherein: each collecting unit comprises a signal amplifier, a capacitor, a rheostat and a switch unit; the signal amplifier has a negative input terminal connected with one of the ridge capacitors or one of the valley capacitors, a positive input terminal connected with a voltage reference terminal, and an output terminal configured to output the first voltage or the second voltage; the capacitor is connected between the negative input terminal of the signal amplifier and the output terminal of the signal amplifier; and the switch units connected with the rheostat in series and is configured to control the rheostat to be connected with the capacitor in parallel. ### Claim 13 (depends on 12) The fingerprint detection circuit according to claim 12, wherein the capacitance value of one of the ridge capacitors or the capacitance value of one of the valley capacitors is determined according to formulas of Vo=(Vs−Ct*Cx/Ci) Vs=Vt*Cx*Ts/(Ci*Ci*Rs), wherein Vo is the first voltage or the second voltage, Vt is the excitation voltage, Cx is the capacitance value of one of the ridge capacitors or the capacitance value of one of the valley capacitors, Ci is the capacitance value of the capacitor, Vs is the regulation voltage, Rs is a resistance value of the rheostat, and Ts a detecting period. ### Claim 14 (depends on 1) The fingerprint detection circuit according to claim 1, wherein the processing module further comprises a sampling hold circuit and an analog-to-digital converter, and the sampling hold circuit is connected between the output terminal of the signal amplifier and the analog-to-digital converter. ### Claim 15 A fingerprint detection method, comprising: applying an excitation signal to a finger so as to generate ridge capacitors and valley capacitors; generating a first voltage or a second voltage by a collecting unit according to a regulation voltage, a capacitance value of one of the ridge capacitors and a capacitance value of one of the valley capacitors; amplifying the first voltage and the second voltage with a predetermined factor by a processing module; calculating a difference between an amplified first voltage and an amplified second voltage by the processing module; determining whether the difference is greater than or equal to a predetermined threshold by the processing module; when the difference is greater than or equal to the predetermined threshold, calculating the capacitance value of one of the ridge capacitors according to the first voltage and calculating the capacitance value of one of the valley capacitors according to the second voltage by the processing module; and when the difference is less than the predetermined threshold, adjusting at least one of an excitation voltage, the predetermined factor and the regulation voltage according to the predetermined threshold and the difference by the processing module, and configuring the collecting unit and the processing module with at least one adjusted parameter. ### Claim 16 An electronic device, comprising a fingerprint detection circuit configured to apply an excitation signal to a finger so as to generate ride capacitors and valley capacitors, wherein the fingerprint detection circuit further comprises: a fingerprint collecting module comprising a plurality of collecting units, wherein each of the plurality of collecting units has a regulation voltage, and is configured to output a first voltage or a second voltage according to a capacitance value of one of the ridge capacitors, a capacitance value of one of the ridge capacitors, and the regulation voltage; and a processing module connected with the fingerprint collecting module, and configured to amplify the first voltage and the second voltage by a predetermined factor, to calculate a difference between an amplified first voltage and an amplified second voltage, and to determine whether the difference is greater than or equal to a predetermined threshold; wherein; where the difference is greater than or equal to the predetermined threshold, the processing module is further configured to calculate the capacitance value of one of the ridge capacitors according to the first voltage, and to calculate the capacitance value of one of the valley capacitors according to the second voltage; and when the difference is less than the predetermined threshold, the processing module is further configured to adjust at least one of an excitation voltage, the predetermined factor and the regulation voltage according to the predetermined threshold and the difference, and to configure the fingerprint collecting module and the processing module using at least one adjusted parameter, in which the excitation voltage is a voltage magnitude of the excitation signal, ### Claim 17 (depends on 16) The electronic device according to claim 16, wherein: when the predetermined factor is adjusted, the processing module is further configured to amplify the first voltage and the second voltage by an adjusted predetermined factor, to calculate an adjusted difference between an adjusted value of the amplified first voltage and an adjusted value of the amplified second voltage, and to determine whether the adjusted difference is greater than or equal to the predetermined threshold; and when at least one of the excitation voltage and the regulation voltage is adjusted, or when each of the excitation voltage, the regulation voltage and the predetermined factor is adjusted, the collecting unit is further configured to output a first adjusted voltage or a second adjusted voltage according to the capacitance value of one of the valley capacitors the capacitance value of one of the ridge capacitors and the adjusted regulation voltage, and the processing module is further configured to amplify the first adjusted voltage and the second adjusted voltage by the predetermined factor or by the adjusted predetermined factor, to calculate the adjusted difference between the amplified value of the first adjusted voltage and the amplified value of the second adjusted voltage, and to determine whether the adjusted difference is greater than or equal to the predetermined threshold. ### Claim 18 (depends on 16) The electronic device according to claim 16, wherein the first voltage has a non-linear relationship with the capacitance value of one of the ridge capacitors, and the second voltage has a non-linear relationship with the capacitance value of one of the valley capacitors.