KR102052941B1 - A fingerprint detection device and a fingerprint detection method USING TOUCH PRESSURE INFORMATION - Google Patents

Abstract

The present invention can provide a fingerprint detection device and a fingerprint detection method, which can reduce an unnecessary fingerprint detection operation by unintentional contact of a user, and power consumption resulting from the unnecessary fingerprint detection operation. In one aspect of the present invention, the fingerprint detection device comprises a fingerprint sensor for detecting information of the fingerprint; and an information processing unit for processing the information detected from the fingerprint sensor, wherein the information processing unit determines whether there is a fingerprint pattern based on the information received from the fingerprint sensor in a low power fingerprint detection mode, and the fingerprint sensor operates in a precision fingerprint detection mode to detect fingerprint information if it is determined that there is a fingerprint pattern as the result of the determination, transmits the information detected in the precision fingerprint detection mode by the fingerprint sensor to a main processor, and does not operate the fingerprint sensor in the precise fingerprint detection mode if it is determined that there is no fingerprint pattern as the result of the determination.

Description

A fingerprint detection device and a fingerprint detection method USING TOUCH PRESSURE INFORMATION}

The present invention relates to a fingerprint detection device and a fingerprint detection method. Specifically, the present invention relates to a fingerprint detection device and a fingerprint detection method for reducing power consumption by utilizing touch pressure information.

Recently, the security level of the system is increasing, and interest in biometric devices is increasing as a security method considering user convenience. Among biometric systems, fingerprint detection devices are already used in a variety of applications.

The fingerprint detection device may use various principles such as a capacitance method, a resistance method, an optical method, and a thermal method. Among them, the capacitive method having excellent performance in terms of size and power consumption is most widely used.

The fingerprint detection apparatus detects fingerprint information, transmits the detected fingerprint information to the main processor, and analyzes the fingerprint in the main processor, which may cause power consumption.

When the fingerprint detection device is used in a portable device such as a smart phone, there is a problem that a part of the user's hand accidentally touches the fingerprint detection device to operate the fingerprint detection device unnecessarily. In this case, the fingerprint detection operation of the fingerprint detection apparatus and the fingerprint analysis operation of the main processor are repeated and unnecessary power consumption may occur.

The present invention can provide a fingerprint detection device and a fingerprint detection method capable of reducing unnecessary fingerprint detection operation due to an unintended contact of a user and power consumption thereby.

One aspect of the invention, the fingerprint sensor for detecting information about the fingerprint; And an information processor configured to process information detected by the fingerprint sensor, wherein the information processor determines whether the fingerprint pattern is a fingerprint pattern based on information received from the fingerprint sensor in a low power fingerprint detection mode. If it is determined as a pattern, the fingerprint sensor operates in the precision fingerprint detection mode to detect fingerprint information, and in the precision fingerprint detection mode, the information detected by the fingerprint sensor is transmitted to the main processor. If not, the fingerprint sensor is characterized in that the fingerprint sensor does not operate in the precision fingerprint detection mode.

In the fingerprint detection device, the fingerprint sensor may be a capacitive fingerprint sensor that detects information on capacitance between a finger and the fingerprint sensor.

In the fingerprint detection device, the fingerprint detection device receives pressure information from a pressure sensor, the information processing unit operates in a pressure detection mode to determine whether or not an effective touch based on the pressure information received from the pressure sensor, If it is determined that the effective touch is determined, the low power fingerprint detection mode may be entered. If it is determined that the touch is not an effective touch, the low power fingerprint detection mode may not be entered.

In the fingerprint detection device, the information processor may determine that the touch is effective when the pressure detected by the pressure sensor is equal to or greater than a reference value.

The fingerprint detection device, wherein the information processing unit comprises: a first analog circuit for converting information detected by the fingerprint sensor into a voltage signal; And a second analog circuit configured to perform offset adjustment and gain amplification on the output signal of the first analog circuit and output the same.

In the fingerprint detection device, the output signal of the pressure sensor may be transmitted to the second analog circuit.

In the fingerprint detection device, the information processing unit may further include an impedance matching circuit that receives the output signal of the pressure sensor and transmits it to the second analog circuit.

In the fingerprint detection device, the impedance matching circuit may block the pressure detection operation of the pressure sensor.

In the fingerprint detection device, the information processor may perform the pressure detection while changing the amplification gain of the second analog circuit in the pressure detection mode.

In the fingerprint detection device, the pressure sensor may be a capacitive pressure sensor, and the output signal of the capacitive pressure sensor may be input to the second analog circuit through a variable capacitance detection circuit.

In the fingerprint detection device, the information processing unit may perform the pressure detection while changing the feedback capacitance of the variable capacitance detection circuit in the pressure detection mode.

In the fingerprint detection device, the capacitive pressure sensor may be configured as a single cell.

In the fingerprint detection device, the pressure sensor may be a resistive pressure sensor.

Another aspect of the present invention provides a fingerprint detection method performed by a fingerprint detection device, the fingerprint detection method comprising: a pressure detection step of detecting pressure through a pressure sensor; An effective touch determination step of determining whether an effective touch is made based on the pressure information detected in the pressure detection step; A low power fingerprint detection step of detecting fingerprint information through a fingerprint sensor by operating in a low power fingerprint detection mode when it is determined as an effective touch in the valid touch determination step; A fingerprint pattern determining step of determining whether a fingerprint pattern is based on fingerprint information detected in the low power fingerprint detection step; A precision fingerprint detection step of detecting fingerprint information through a fingerprint sensor by operating in a precision fingerprint detection mode when it is determined as a fingerprint pattern; And a fingerprint information transmitting step of transmitting the fingerprint information detected in the precise fingerprint detection step to the main processor.

In the fingerprint detection method, when the pressure detected by the pressure sensor is greater than or equal to the threshold pressure may be determined to be an effective touch.

In the fingerprint detection method, in the pressure detection step, pressure detection may be performed while changing an amplification gain for the pressure signal.

In the fingerprint detection method, the pressure sensor is a capacitive pressure sensor, and in the pressure detection step, pressure detection may be performed while changing the feedback capacitance.

According to the present invention, by first determining whether or not an effective touch is performed using the touch pressure information, and starting the fingerprint detection operation, unnecessary fingerprint detection operation due to unintended contact of the user can be reduced, thereby reducing power consumption.

1 is a diagram schematically illustrating a fingerprint detection device according to an embodiment of the present invention.
2 is a diagram schematically illustrating a fingerprint detection device according to another embodiment of the present invention.
3 is a diagram schematically illustrating the structures of a fingerprint sensor and a pressure sensor.
4 is a diagram schematically illustrating a structure of a fingerprint sensor.
5 is a diagram illustrating an example of an information processing unit.
6 is a diagram illustrating the characteristics of the digital conversion value according to the detection voltage of the resistive pressure sensor.
7 is a diagram for describing an impedance matching circuit.
8 is a diagram illustrating another example of the information processing unit.
9 is a diagram illustrating the capacitance characteristics according to the distance of the capacitive pressure sensor.
10 is a diagram illustrating an example of a variable capacitance detection circuit.
11 is a diagram illustrating a fingerprint detection method according to another embodiment of the present invention.

Hereinafter, some embodiments of the present invention will be described in detail through exemplary drawings. In adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are assigned to the same components as much as possible even though they are shown in different drawings. In addition, in describing the present invention, when it is determined that the detailed description of the related well-known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted.

In addition, in describing the component of this invention, terms, such as 1st, 2nd, A, B, (a), (b), can be used. These terms are only for distinguishing the components from other components, and the nature, order or order of the components are not limited by the terms. If a component is described as being "connected", "coupled" or "connected" to another component, that component may be directly connected to or connected to that other component, but there may be another configuration between each component. It is to be understood that the elements may be "connected", "coupled" or "connected".

1 is a diagram schematically illustrating a fingerprint detection device according to an embodiment of the present invention. Referring to FIG. 1, the fingerprint detection apparatus 100 may include an information processor 110, a fingerprint sensor 120, and a pressure sensor 130.

The fingerprint sensor 120 may detect information about the fingerprint. For example, the fingerprint sensor 120 may be a capacitive fingerprint sensor that detects information about the capacitance between the finger and the fingerprint sensor 120. The capacitive fingerprint sensor can recognize a fingerprint by detecting a capacitance formed between the fingerprint sensor array and the ridge of the fingerprint. In order to recognize the capacitance between the fingerprint sensor array and the finger, a method of applying an excitation signal between the finger and the detection circuit and sensing a change in the electrical signal generated in the capacitance between the sensor array and the finger may be used. As a method of applying an excitation signal between the finger and the detection circuit, a method of connecting a finger to a fixed potential (eg, ground) and applying an excitation signal to the detection circuit or applying an excitation signal to the finger may be used. In the present embodiment, a capacitive fingerprint sensor will be described as an example, but the fingerprint sensor 120 may be a fingerprint sensor of another type such as a resistive method, an optical method, or a thermal method.

The pressure sensor 130 may detect a force (pressure) that the user's finger presses on the fingerprint detection apparatus 100. The pressure information detected by the pressure sensor 130 may be used to determine whether it is an intentional contact by the user. The pressure sensor 130 may be a resistive pressure sensor or a capacitive pressure sensor, but is not limited thereto. The resistive pressure sensor may be a sensor having a characteristic in which a resistance value changes with pressure. The capacitive pressure sensor may be a sensor having a characteristic in which capacitance changes with pressure. The capacitive pressure sensor may be composed of a single cell.

The information processor 110 may process information detected by the fingerprint sensor 120 and the pressure sensor 130. For example, the information processing unit 110 may operate in the pressure detection mode to determine whether or not the effective touch is based on the pressure information received from the pressure sensor 130, and when it is determined as the effective touch, enter the low power fingerprint detection mode, If it is determined that the touch is not an effective touch, it may not enter the low power fingerprint detection mode. In this case, the information processor 110 may determine that the touch is effective when the pressure detected by the pressure sensor is equal to or greater than the reference value. Effective touch may be understood to mean a state in which the touch of the fingerprint detection device by the user is determined to have the intention of fingerprint recognition.

For example, the information processor 110 may determine whether the fingerprint pattern is a fingerprint pattern based on the information received from the fingerprint sensor 120 in the low power fingerprint detection mode, and if the determination result is the fingerprint pattern, the fingerprint sensor 120 may be precise. The fingerprint sensor detects fingerprint information by operating in the fingerprint detection mode, and transmits the information detected by the fingerprint sensor 120 to the main processor in the precision fingerprint detection mode. 120 may not operate in the precision fingerprint detection mode.

In an exemplary embodiment, the low power fingerprint detection mode may selectively select one or more methods of operating only a part of the cell arrays constituting the fingerprint sensor 120, reducing the magnitude of the excitation voltage, or reducing the number of bits of the analog-to-digital converter. It can be used in the fingerprint detection mode that can reduce the power consumption while lowering the accuracy of fingerprint detection. For example, in the low power fingerprint detection mode, the fingerprint may be detected with a precision enough to analyze the curvature of the fingerprint (the interval between the fingerprint ridges), and it may be determined whether or not the fingerprint pattern is through the curvature of the analyzed fingerprint. The precision fingerprint detection mode may be a fingerprint detection mode that detects a fingerprint with a high precision enough to perform fingerprint analysis (fingerprint recognition and fingerprint matching, etc.) but consumes more power than a low power fingerprint detection mode.

The information processor 110 may transmit the fingerprint information collected in the precision fingerprint detection mode to an external main processor so that the main processor analyzes the fingerprint. For example, when the fingerprint detection apparatus 100 is used in a smartphone, the fingerprint detection apparatus 100 transmits the fingerprint information collected in the precision fingerprint detection mode to the smartphone's main processor, and the smartphone's main processor analyzes the fingerprint. Can be performed. However, the present exemplary embodiment is not limited thereto, and according to an exemplary embodiment, the main processor may be included in the fingerprint detection apparatus 100. For example, when the main processor is disposed outside the fingerprint detection apparatus 100, the fingerprint detection apparatus 100 does not transmit the fingerprint information collected in the low power fingerprint detection mode to the main processor, but the information processing unit 110 therein. By determining whether the fingerprint pattern in the can reduce the burden and power consumption of the main processor.

As described above, the fingerprint detection apparatus 100 determines whether or not the effective touch is based on the pressure information detected by the pressure sensor, and enters the low power fingerprint detection mode when it is determined as the effective touch. Fingerprint detection operation is performed by an unintentional touch of the user, thereby reducing the unnecessary waste of power. In addition, the fingerprint detection apparatus 100 determines whether the fingerprint pattern is determined through the low power fingerprint detection mode and enters the precision fingerprint detection mode when it is determined as the fingerprint pattern, thereby reducing the number of operations of the precision fingerprint detection mode with high power consumption, thereby reducing power consumption. Can be reduced.

2 is a diagram schematically illustrating a fingerprint detection device according to another embodiment of the present invention. The fingerprint detection apparatus 200 of FIG. 2 has a difference in that a pressure sensor is not included in the fingerprint detection apparatus 200 compared to the fingerprint detection apparatus 100 of FIG. 1. In this case, the information processing unit 110 may receive pressure information from an external pressure sensor, and utilize the pressure information similarly as described with reference to FIG. 1.

3 is a diagram schematically illustrating the structures of a fingerprint sensor and a pressure sensor.

Referring to FIG. 3, the fingerprint sensor 120 may be formed on the semiconductor chip 340, and the pressure sensor 350 may be formed separately under the semiconductor chip 340. The information processor 110 may be formed together on the semiconductor chip 340.

The pressure sensor 350 may include two electrodes 351 and 352 and an intermediate layer 353. When the user presses the fingerprint sensor 120 for fingerprint recognition, the pressing force of the user is transmitted to the pressure sensor 350 so that the distance between the two electrodes 351 and 352 of the pressure sensor 350 is changed, which causes the two electrodes. The physical quantity (eg, capacitance or resistance) between can vary. The information processor 110 may receive information about the pressure from the two electrodes 351 and 352 of the pressure sensor 350.

In FIG. 3, the pressure sensor 350 is illustrated as being formed under the semiconductor chip 340, but the present embodiment is not limited thereto. The pressure sensor 350 may be formed directly on the semiconductor chip 340 or may be variously modified, such as formed along the outer periphery of the semiconductor chip 340. However, when the pressure sensor 350 is formed below the semiconductor chip 340 as shown in FIG. 3, there is an advantage of minimizing the entire area.

4 is a diagram schematically illustrating a structure of a fingerprint sensor. 4 is a simplified illustration of only some components necessary for explanation among the components of the fingerprint sensor and the information processor. In addition, the fingerprint sensor may have a structure in which a plurality of cells are arranged in an array having rows and columns, and only a portion corresponding to one cell is illustrated in FIG. 4.

Referring to FIG. 4, the fingerprint sensor may include a sensing electrode 422, a feedback electrode 423, a protective layer 424, and an insulating layer 425. The fingerprint sensor may include various configurations.

The fingerprint capacitance Cf may be a capacitance between the sensing electrode 422 and the finger. The fingerprint capacitance Cf may have a capacitance value depending on the shape of the fingerprint between the sensing electrode 422 and the finger. The finger may be electrically connected to the device reference potential (ground), but the finger may be in a state that is not connected to a particular reference potential. The sensing electrode 422 may be electrically connected to the fingerprint capacitance detection circuit 411 inside the information processor through the wire 427. In FIG. 4, the sensing electrode 422 is illustrated as being electrically connected to the negative input terminal (−) of the amplifier A through the first switching element S1, but the present exemplary embodiment is not limited thereto.

The feedback capacitance Cg may be a capacitance between the feedback electrode 423 and the sensing electrode 422. As the feedback capacitance Cg, a capacitance naturally formed between the feedback electrode 423 and the sensing electrode 422 may be used, but a separate capacitor element may be added if necessary. The feedback electrode 423 may be electrically connected to the fingerprint capacitance detection circuit 411 through the wiring 426. 4 illustrates that the feedback electrode 423 is electrically connected to the output terminal of the amplifier A, but the present embodiment is not limited thereto.

The protective layer 424 may be formed on the fingerprint sensor to protect the fingerprint sensor from ESD, mechanical shock or abrasion. The protective layer 424 may contain well-known materials, such as resin and glass, and may also include a general insulating layer.

The insulating layer 425 may be added for electrical insulation between the sensing electrode 422 and the feedback electrode 423. As the insulating layer 425, conventional insulating materials such as SiO ₂ , SiN, and glass may be used. In addition to the insulating function, the insulating layer 425 may perform a function of adjusting the feedback capacitance Cg between the sensing electrode 422 and the feedback electrode 423. The feedback capacitance Cg may be adjusted not only through the sizes of the sensing electrode 422 and the feedback electrode 423, but also by the thickness and dielectric constant of the insulating layer 425.

In addition to the configuration illustrated in FIG. 4, various types of metal layers, insulating layers, and the like may be added to the fingerprint sensor, and the description thereof will be omitted in order not to obscure the subject matter of the present invention.

The amplifier A, the first switching element S1, the second switching element S2, the amplifier reference voltage Vref, the supply voltage high potential VH and the supply voltage low potential VL shown in FIG. The fingerprint capacitance detection circuit 411 in the processor 110 is illustrated. The fingerprint capacitance detection circuit 411 may constitute a part of the first analog circuit (see 111 in FIG. 5). It should be understood that the fingerprint capacitance detection circuit 411 illustrated in FIG. 4 is simply illustrated to understand the operation of the fingerprint sensor. In addition, although one fingerprint capacitance detection circuit 411 is illustrated as being connected to one fingerprint sensor cell in FIG. 4, one fingerprint capacitance detection circuit 411 is connected to a plurality of fingerprint sensor cells and thus a plurality of fingerprint sensor cells. It is possible to selectively process the signal received from.

The negative input terminal (-) of the amplifier of the fingerprint capacitance detection circuit 411 is electrically connected to the sensing electrode 422 through the first switching element S1, and the positive input terminal (+) of the amplifier is referred to the amplifier. It is connected to the voltage (Vref), the output terminal of the amplifier (A) may be connected to the input terminal (-) of the amplifier negative through the second switching element (S2). The amplifier A may receive a power supply voltage high potential (VH) and a power supply voltage low potential (VL) to be used as a power source for operation. The power supply voltage low potential VL may be used as a reference potential (ground) for signal processing of the amplifier A.

The first switching element S1 may selectively connect the sensing electrode 422 and the negative input terminal (-) of the amplifier, and the second switching element S2 may have a negative input terminal (-) of the amplifier and the amplifier ( A) The output terminal can be selectively connected. For example, the fingerprint detection may be performed by turning on the first switching element after detecting the reference state in which the influence of the fingerprint is excluded while the first switching element S1 is turned off. The second switching element S2 may be used to initialize (discharge) the feedback capacitance Cg.

5 is a diagram illustrating an example of an information processing unit.

Referring to FIG. 5, the information processing unit 110 may include a first analog circuit 111, a data transfer circuit 112, a second analog circuit 113, an analog-digital converter 114, a logic circuit 115, and input / output. Circuit 116 and impedance matching circuit 117.

The information processor 110 may receive fingerprint information from the fingerprint sensor 120, receive pressure information from the pressure sensor, and transmit fingerprint information detected in the precision fingerprint detection mode to the main processor.

The first analog circuit 111 may receive a signal including fingerprint information from the fingerprint sensor 120 and convert it to a voltage signal. For example, when the fingerprint sensor 120 is capacitive, the signal received from the fingerprint sensor 120 includes information on capacitance, and the first analog circuit 111 receives the fingerprint sensor 120 from the fingerprint sensor 120. A signal including information on the capacitance can be converted into a voltage signal. In exemplary embodiments, the first analog circuit 111 may include the fingerprint capacitance detection circuit 411 of FIG. 4. In exemplary embodiments, the fingerprint sensor 120 may be configured as an array including M x N cells, and the first analog circuit 111 may be configured to simultaneously process some of the M x N cells. To this end, the first analog circuit 111 may include n fingerprint capacitance detection circuits. Here, n may be a number equal to M or N or smaller than M or N. That is, the first analog circuit 111 includes n fingerprint capacitance detection circuits and simultaneously processes one column of a cell array composed of M x N (n = M) or simultaneously processes one row (n = N) or signals received from cells in units smaller than a row or column may be processed simultaneously (n <M or N).

The data transfer circuit 112 may selectively transmit voltage signals received from the first analog circuit 111 to the second analog circuit. By way of example, when the first analog circuit 111 outputs n voltage signals simultaneously and the second analog circuit can process one signal, the data transfer circuit 112 from the first analog circuit 111. The received n voltage signals may be sequentially transmitted to the second analog circuit 113 over time. To this end, the data transfer circuit 112 may include a multiplexer and a sample-hold circuit.

The second analog circuit 113 may perform offset adjustment and / or gain amplification on the output signal of the first analog circuit 111 received through the data transfer circuit 112. In addition, the second analog circuit 113 may perform offset adjustment and / or gain amplification on the output signal of the pressure sensor received through the impedance matching circuit 117. In exemplary embodiments, the second analog circuit 113 processes a signal received through the impedance matching circuit 117 in the pressure detection mode, and receives the data received from the data transfer circuit 112 in the low power fingerprint detection mode and the precision fingerprint detection mode. You can process the signal.

The control signal gain_con for adjusting the amplification gain and the control signal offset_con for adjusting the offset may be input to the second analog circuit 113. These control signals gain_con and offset_con may be generated by the logic circuit 115. The second analog circuit 113 adjusts the amplification gain based on the control signal gain_con for adjusting the amplification gain received from the logic circuit 115 and / or based on the control signal offset_con for adjusting the offset. By adjusting the offset, the dynamic range can be extended and the accuracy of detection can be increased.

The analog-digital converter 114 may convert an analog signal received from the second analog circuit 113 into a digital signal and output the digital signal.

The logic circuit 115 may perform overall control, determination, and arithmetic functions in the information processor 110. In exemplary embodiments, the logic circuit 115 generates the offset control signal offset_con and the gain control signal gain_con of the second analog circuit 113, and enables and impedances of the impedance matching circuit 117. The control signal Z_con may be generated. Also, as an example, the logic circuit 115 may lead the operation mode control (pressure detection mode, low power fingerprint detection mode, precision fingerprint detection mode) and the fingerprint detection method described later. The logic circuit 115 may be implemented by hardware such as an ASIC, but is not limited thereto. The logic circuit 115 may be implemented by software or firmware. However, when the logic circuit 115 is implemented in hardware such as an ASIC, there is an advantage that the operation speed is faster than that implemented in software or firmware.

The input / output circuit 116 may provide a path through which the information processor 110 transmits and receives information with the main processor. In exemplary embodiments, the input / output circuit 116 may receive the fingerprint information detected in the precision fingerprint detection mode from the logic circuit 115 and transmit it to the main processor.

The impedance matching circuit 117 may receive and process the output signal of the pressure sensor and transmit the processed signal to the second analog circuit 113. In exemplary embodiments, the impedance matching circuit 117 may block the pressure detection operation of the pressure sensor based on an enable signal received from the logic circuit 115. Here, blocking the pressure detection operation of the pressure sensor may be, for example, reducing or blocking the pressure sensor from consuming power for pressure detection. Also, for example, the impedance matching circuit 117 may adjust the impedance inside the impedance matching circuit 117 based on the impedance control signal Z_con received from the logic circuit 115. The adjustment of the impedance inside the impedance matching circuit 117 is to increase the accuracy of pressure detection by adjusting the impedance inside the impedance matching circuit 117 according to the impedance (resistance or capacitance) detected by the pressure sensor.

6 is a diagram illustrating the characteristics of the digital conversion value according to the detection voltage of the resistive pressure sensor.

A resistive pressure sensor may be used for the pressure sensor of this embodiment. The information detected by the resistive pressure sensor can be converted into a voltage and then converted back into a digital value by the analog-to-digital converter. For example, when the analog-to-digital converter operates in 8 bits, the digital conversion value may be divided into 256 steps. When the entire voltage range corresponding to the detected pressure is expressed in 8 bits, the resolution may be lowered. To solve this problem, a portion of the entire voltage range can be represented by 8 bits and the offset can be adjusted according to the voltage range corresponding to the detected signal. In the present exemplary embodiment, the second analog circuit 113 illustrated in FIG. 5 may have a function of adjusting such an offset, thereby increasing resolution and enabling accurate determination of valid touch.

The second analog circuit 113 may include an adjustment function of the amplification gain in addition to the offset adjustment function. In this case, as in the offset adjustment, the accuracy of pressure detection may be increased to accurately determine whether an effective touch is performed.

7 is a diagram for describing an impedance matching circuit. In FIG. 7, the pressure sensor is illustrated as a variable impedance Za in consideration of a characteristic in which impedance varies with pressure. The impedance matching circuit 117 is shown as including a variable impedance Zb and a switching element SW, which does not represent the actual circuit of the impedance matching circuit 117 but describes the operation of the impedance matching circuit 117. It should be understood as a conceptual example. It can be understood that the variable impedance Zb of the impedance matching circuit 117 describes the impedance matching function with the pressure sensor and the switching element SW describes the operation blocking function of the pressure sensor.

The impedance matching circuit 117 may adjust the internal impedance Zb based on the impedance control signal Z_con received from the logic circuit. This is to increase the accuracy of pressure detection by changing the impedance Zb inside the impedance matching circuit 117 in response to the impedance Za that changes according to the pressure of the pressure sensor as described above.

In addition, the impedance matching circuit 117 may control the on / off of the internal switching element SW based on an enable signal received from the logic circuit. When the switching element SW is turned on, current flows through the impedance Za of the pressure sensor and the internal impedance Zb of the impedance matching circuit 117, and the second analog circuit 113 includes information about pressure. Can be input. When the switching element SW is turned off, current cannot flow through the impedance Za of the pressure sensor, and thus power consumption by the pressure sensor can be cut off or reduced instead of losing the pressure detection function of the pressure sensor. Therefore, in the pressure detection mode, the switching element SW is turned on to detect the pressure, and in the non-pressure detection mode, the switching element SW is turned off to cut off the pressure detection operation of the pressure sensor, thereby reducing power consumption by the pressure sensor. have.

7 conceptually illustrates an impedance matching circuit 117 assuming a case where a resistive pressure sensor is used. When the capacitive pressure sensor is used, the operation of the impedance matching circuit 117 described with reference to FIG. 7 will be similar, but the internal structure of the impedance matching circuit 117 may vary.

8 is a diagram illustrating another example of the information processing unit. The information processor 810 of FIG. 8 differs from the information processor 110 of FIG. 5 in that it further includes a variable capacitance detection circuit 818.

The variable capacitance detection circuit 818 may optionally be used when a capacitive pressure sensor is used. The variable capacitance detection circuit 818 may receive a signal about the capacitance of the pressure sensor from the impedance matching circuit 117, process it, and output the signal to the second analog circuit. In this case, the variable capacitance detecting circuit 818 may convert and output the received signal while changing the feedback capacitance inside the pressure detecting mode.

Hereinafter, the variable capacitance detection circuit 818 will be described in detail with reference to FIGS. 9 and 10. FIG. 9 is a diagram illustrating capacitance characteristics according to a distance of a capacitive pressure sensor, and FIG. 10 is a diagram illustrating an example of a variable capacitance detection circuit.

As illustrated in FIG. 9, the capacitance of the capacitive pressure sensor may have a property that is inversely proportional to the distance between two electrodes. By way of example, the capacitance in region A may have a fairly large value, the capacitance in region C may have a relatively small value, and the region B may have a medium value. At this time, the difference between the capacitance in the region A and the capacitance in the region C may be large.

As illustrated in FIG. 10, in consideration of the large change range of the capacitance of the capacitive pressure sensor, the variable capacitance detection circuit 818 may be configured to change the capacitance of the internal feedback capacitor Cg. Can be. To this end, the variable capacitance detection circuit 818 includes a plurality of feedback capacitors CgA, CgB, and CgC, and each feedback capacitor CgA, CgB, and CgC is selectively used through switching elements SWA, SWB, and SWC. It may be configured to. For example, the plurality of feedback capacitors CgA, CgB, and CgC may have different capacities, and the plurality of feedback capacitors CgA, CgB, and CgC may correspond to a capacitance range according to the distance of the capacitive pressure sensor. ), An appropriately sized feedback capacitor may optionally be used. For example, in FIG. 9, a feedback capacitor CgA is used for the region A, a feedback capacitor CgB is used for the region B, and a feedback capacitor CgC is used for the region C. In FIG. In addition, when three feedback capacitors CgA, CgB, and CgC are included and two or more may be simultaneously used through three switching elements SWA, SWB, and SWC, an eight-step capacitance may be used. It can be configured to cope with the capacitance of the capacitive pressure sensor more precisely.

11 is a diagram illustrating a fingerprint detection method according to another embodiment of the present invention.

In step S1101, the fingerprint detection device may detect the pressure through the pressure sensor (pressure detection step). A resistive pressure sensor or a capacitive pressure sensor may be used as the pressure sensor, but is not limited thereto. In exemplary embodiments, the fingerprint detection device may detect the pressure more precisely by performing pressure detection while changing the offset and / or amplification gain for the pressure signal in the pressure detection step. For example, when the pressure sensor is a capacitive pressure sensor, the fingerprint detection device may detect the pressure more precisely by performing pressure detection while changing the feedback capacitance in the pressure detection step.

In operation S1103, the fingerprint detection apparatus may determine whether or not the effective touch is based on the pressure information detected in the pressure detection step (effective touch determination step). For example, the fingerprint detection apparatus may determine that the touch is effective when the pressure detected by the pressure sensor is equal to or greater than the reference value.

If it is determined in step S1103 that the effective touch, the flow proceeds to step S1105 to detect the fingerprint information through the fingerprint sensor in the low power fingerprint detection mode (low power fingerprint detection step). If it is determined in step S1103 that the touch is not an effective touch, it may return to step S1101. For example, in the low power fingerprint detection step, fingerprint detection may be performed by selectively using one or more methods of operating only a part of the array constituting the fingerprint sensor, reducing the magnitude of the excitation voltage, or reducing the number of bits of the analog-to-digital converter. The power consumption can be reduced while lowering the precision of.

In step S1107, it may be determined whether the fingerprint is a pattern based on the fingerprint information detected in the low power fingerprint detection step (fingerprint pattern determination step). For example, in the low power fingerprint detection step, the fingerprint is detected with a precision enough to analyze the curvature of the fingerprint (the gap between the fingerprint ridges), and in the fingerprint pattern determination step, whether the fingerprint pattern is determined by the curvature of the analyzed fingerprint is determined. You can judge.

If it is determined in step S1107 that the fingerprint pattern, the flow proceeds to step S1109 to detect the fingerprint information through the fingerprint sensor in the precision fingerprint detection mode (precision fingerprint detection step). For example, in the precision fingerprint detection step, the fingerprint may be detected with high precision to perform fingerprint analysis, but the power consumption may be relatively higher than that of the low power fingerprint detection step.

If it is determined in step S1107 that it is not the fingerprint pattern, it may be selectively returned to either step S1101 (pressure detection step) or S1107 step (low power fingerprint detection step). For example, if it is determined in step S1107 that the fingerprint pattern is not the same as the fingerprint pattern (Case 1), the process returns to step S1105 to perform the low power fingerprint detection step again, and in step S1107 the reason why the fingerprint pattern is not determined is If there is a contact failure (Case 2), the process returns to step S1101 and the pressure detection step can be performed again.

After performing the fine fingerprint detection in step S1109, the flow proceeds to step S1111 to transmit the fingerprint information detected in the fine fingerprint detection step to the main processor (fingerprint information transmitting step).

The main processor may receive the fingerprint information collected by the fingerprint detection device in the precision fingerprint detection step, and perform fingerprint analysis such as fingerprint recognition and fingerprint matching based on the received fingerprint information. When the main processor cannot perform fingerprint analysis due to an error in the fingerprint information received from the fingerprint detection device, the main processor transmits the error information to the fingerprint detection device, and the fingerprint detection device detects the pressure based on the error information received from the main processor. The process may return to any one of step S1101, low power fingerprint detection step S1105, and precision fingerprint detection step S1109.

Here, step S1101 (pressure detection step) and step S1103 (effective touch determination step) are included in the above-described pressure detection mode, and step S1105 (low power fingerprint detection step) and step S1107 (fingerprint pattern determination step) are described above. Included in the detection mode, steps S1109 (precision fingerprint detection step) and step S1111 (fingerprint information transmission step) can be understood to be included in the above-described precision fingerprint detection mode.

As described above, according to an exemplary embodiment of the present invention, by determining whether an effective touch is first performed by using touch pressure information, the fingerprint detection operation is started, thereby reducing power consumption by reducing unnecessary fingerprint detection operation due to unintended contact of the user. Can be. In addition, according to an embodiment, by determining whether the fingerprint pattern through the low power fingerprint detection mode and enters the precision fingerprint detection mode when it is determined that the fingerprint pattern, the power consumption is reduced by reducing the number of operations of the high power consumption of the fingerprint detection mode You can. Further, according to the embodiment, by processing the signal while automatically changing the offset and / or amplification gain with respect to the signal detected by the pressure sensor, it is possible to expand the dynamic range and increase the accuracy of the detection. In addition, according to the embodiment, the accuracy of the pressure detection may be increased by matching the impedance with respect to the output signal of the pressure sensor. In addition, according to the embodiment, it is possible to block the operation of the pressure sensor to reduce the power consumption by the pressure sensor. In addition, according to the embodiment, when the capacitive pressure sensor is used, it is possible to change the feedback capacitance of the variable capacitance detection circuit, thereby enabling precise detection of a wide range of capacitance of the pressure sensor.

The terms "comprise", "comprise" or "having" described above mean that a corresponding component may be included unless specifically stated otherwise, and thus does not exclude other components. It should be construed that it may further include other components. All terms, including technical and scientific terms, have the same meanings as commonly understood by one of ordinary skill in the art unless otherwise defined. Terms commonly used, such as terms defined in a dictionary, should be interpreted to coincide with the contextual meaning of the related art, and shall not be construed in an ideal or excessively formal sense unless explicitly defined in the present invention.

The above description is merely illustrative of the technical idea of the present invention, and those skilled in the art to which the present invention pertains may make various modifications and changes without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention but to describe the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The protection scope of the present invention should be interpreted by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

Claims (17)

A fingerprint sensor detecting information about the fingerprint; And
And an information processor configured to process fingerprint information detected by the fingerprint sensor and pressure information detected by the pressure sensor.
The information processing unit,
It operates in the pressure detection mode to determine whether the effective touch based on the pressure information received from the pressure sensor,
If it is determined that the valid touch is a valid touch, the device operates in a low power fingerprint detection mode and detects fingerprint information through the fingerprint sensor. To avoid
In the low power fingerprint detection mode, it is determined whether the fingerprint pattern is based on the fingerprint information received from the fingerprint sensor.
If it is determined that the fingerprint pattern is the fingerprint pattern, the fingerprint sensor operates in the precision fingerprint detection mode to detect the fingerprint information with higher precision than the low power fingerprint detection mode, and the fingerprint sensor in the precision fingerprint detection mode. Transmitting the detected fingerprint information to the main processor to cause the main processor to analyze the fingerprint information detected in the precision fingerprint detection mode, and if it is determined that the fingerprint pattern is not the fingerprint pattern, the fingerprint sensor is Do not perform the precision fingerprint detection mode,
The low power fingerprint detection mode may include at least one of a method of operating only a portion of the array constituting the fingerprint sensor or reducing the magnitude of an excitation voltage for fingerprint detection as compared to the precision fingerprint detection mode. A fingerprint detection device characterized by detecting fingerprint information with low precision. The method according to claim 1,
The fingerprint sensor is a fingerprint detection device, characterized in that the capacitive fingerprint sensor for detecting information about the capacitance between the finger and the fingerprint sensor. delete The method according to claim 1,
And the information processing unit determines that the touch is effective when the pressure detected by the pressure sensor is equal to or greater than a reference value. The method according to claim 1,
The information processing unit,
A first analog circuit for converting information detected by the fingerprint sensor into a voltage signal; And
And a second analog circuit configured to perform offset adjustment and gain amplification on the output signal of the first analog circuit for output. The method according to claim 5,
And the output signal of the pressure sensor is transmitted to the second analog circuit. The method according to claim 6,
The information processing unit,
And an impedance matching circuit which receives the output signal of the pressure sensor and transfers it to the second analog circuit. The method according to claim 7,
The impedance matching circuit can block the pressure detection operation of the pressure sensor. The method according to claim 5,
And the information processing unit performs the pressure detection while changing the amplification gain of the second analog circuit in the pressure detection mode. The method according to claim 9,
The pressure sensor is a capacitive pressure sensor,
The output signal of the capacitive pressure sensor is input to the second analog circuit through a variable capacitance detection circuit. The method according to claim 10,
And the information processing unit performs the pressure detection while changing the feedback capacitance of the variable capacitance detection circuit in the pressure detection mode. The method according to claim 10,
The capacitive pressure sensor is a fingerprint detection device, characterized in that consisting of a single cell. The method according to claim 5,
The pressure sensor is a fingerprint detection device, characterized in that the resistive pressure sensor. In the fingerprint detection method performed by the fingerprint detection device,
A pressure detecting step of detecting pressure through the pressure sensor;
An effective touch determination step of determining whether or not an effective touch is based on the pressure information detected in the pressure detection step;
A low power fingerprint detection step of detecting fingerprint information through a fingerprint sensor by operating in a low power fingerprint detection mode when it is determined as an effective touch in the valid touch determination step;
A fingerprint pattern determining step of determining whether a fingerprint pattern is based on the fingerprint information detected in the low power fingerprint detection step;
A precision fingerprint detection step of detecting fingerprint information again at a higher precision than the low power fingerprint detection mode through a fingerprint sensor when the fingerprint pattern is determined in the fingerprint pattern determination step; And
And a fingerprint information transmitting step of transmitting the fingerprint information detected in the precision fingerprint detection step to a main processor.
If it is determined that the valid touch is not an effective touch, the fingerprint sensor does not perform the low power fingerprint detection mode.
If it is determined in the fingerprint pattern determination step that the fingerprint pattern is not the fingerprint pattern, the fingerprint sensor does not perform the precise fingerprint detection mode,
Fingerprint information detected in the precision fingerprint detection mode is used for fingerprint analysis by the main processor.
The low power fingerprint detection mode may include at least one of a method of operating only a portion of the array constituting the fingerprint sensor or reducing the magnitude of an excitation voltage for fingerprint detection as compared to the precision fingerprint detection mode. A fingerprint detection method for detecting fingerprint information with low precision. The method according to claim 14,
Fingerprint detection method characterized in that it is determined that the effective touch if the pressure detected by the pressure sensor is more than the threshold pressure. The method according to claim 14,
And the pressure detection step performs pressure detection while changing the amplification gain for the pressure signal. The method according to claim 14,
The pressure sensor is a capacitive pressure sensor,
And in the pressure detecting step, pressure detection is performed while changing the feedback capacitance.

Images