KR101897150B1 - Fingerprint detection apparatus and the method - Google Patents

Abstract

The present invention relates to an apparatus and a method for detecting a fingerprint to increase the detection sensitivity and to improve the accuracy of fingerprint detection by easily changing a potential change for the fingerprint detection. The apparatus for detecting a fingerprint of the present invention comprises: a signal processing circuit for receiving and processing a signal corresponding to a capacitance due to a fingerprint from a sensor array; and a power circuit for providing a power voltage high potential and a power voltage low potential to the signal processing circuit. The signal processing circuit can use the power voltage low potential as a signal processing circuit reference potential, and can use a difference between the power voltage high potential and the power voltage low potential as a power voltage. The power voltage low potential can be varied with respect to a virtual reference potential according to an operation mode.

Description

[0001] FINGERPRINT DETECTION APPARATUS AND THE METHOD [0002]

The present invention relates to a fingerprint detection device and a fingerprint detection method.

Recently, the security level for the system has been increasing, and the interest in the biometric system has been increased by the security method considering the user convenience. Among biometric systems, fingerprint detection systems are already widely used in various applications.

The fingerprint detection system can use various principles such as the capacitance type, the optical type, and the thermal type. Of these, the capacitive type having excellent performance in terms of size and power consumption is the most widely used.

The capacitive fingerprint detection system recognizes the fingerprint using the 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 fingerprint, a method of applying the excitation signal to the fingerprint and sensing the change of the electric signal generated in the capacitance between the sensor array and the fingerprint is mainly used.

However, the method of applying the excitation signal to the fingerprint has a problem in that the structure is complex and the sensing sensitivity is weak.

SUMMARY OF THE INVENTION An object of the present invention is to provide a fingerprint detection device in a manner that does not directly apply an excitation signal for fingerprint detection to a fingerprint.

Another object of the present invention is to make it possible to easily change the excitation signal for fingerprint detection, thereby increasing the detection sensitivity and improving the accuracy of the fingerprint detection.

According to an aspect of the present invention, there is provided a signal processing circuit for receiving and processing a signal corresponding to a capacitance due to a fingerprint from a sensor array and a signal processing circuit for providing a high power supply voltage and a low power supply voltage Wherein the signal processing circuit uses the power supply voltage low potential as a signal processing circuit reference potential and uses a difference between the power supply voltage high potential and the power supply voltage low potential as a power supply voltage, And the potential is varied with respect to the virtual reference potential according to the operation mode.

 In the fingerprint detection device, the difference between the power supply voltage high potential and the power supply voltage low potential may be maintained substantially constant despite the change of the operation mode.

The fingerprint detection device according to claim 1, wherein the operation mode includes a reference state detection mode, a fingerprint detection mode, and an evaluation mode, and the signal processing circuit includes a first high potential level (VH1) and a first low potential (VH2) and the second low potential level (VL2) are used in the fingerprint detection mode and the third high potential level (VH3) and the third low potential level A potential level VL3 can be used.

In the fingerprint detection device, the first low potential level (VL1) and the second low potential level (VL2) may be different from each other.

In the fingerprint detection device, the signal processing circuit may include an operational amplifier receiving a reference voltage through an input terminal, and in the fingerprint detection mode, a difference between the reference voltage and the second low potential level (VL2) May be different from the difference between the reference voltage and the first low potential level (VL1) in the state detection mode.

The signal processing circuit includes a first signal processing circuit for receiving a first power supply voltage high potential (VHA) and a first power supply voltage low potential (VLA) through a first power supply line, And a second signal processing circuit for receiving a second power supply voltage high potential (VHB) and a second power supply voltage low potential (VLB) via a wiring, wherein the first power supply voltage low potential (VLA) And the second power supply voltage low potential (VLB) has the first low potential level (VL1) in the evaluation mode and the second low potential level (VL2) in the fingerprint detection mode in the evaluation mode, (VL3).

In the fingerprint detection device, the second power supply voltage low potential (VLB) supplied to the second signal processing circuit can maintain substantially the same potential in the reference state detection mode, the fingerprint detection mode, and the evaluation mode.

In the fingerprint detection device, the same potential held by the second power supply voltage low potential (VLB) is substantially equal to either the first low potential level (VL1) or the second low potential level (VL2) .

In the fingerprint detection device, the reference state detection mode, the fingerprint detection mode, and the evaluation mode may be sequentially performed.

In the fingerprint detection device, the reference state detection mode and the fingerprint detection mode may be sequentially performed, and the evaluation mode may be performed simultaneously with the reference state detection mode and the fingerprint detection mode.

In the above fingerprint detection device, the first power supply line includes a first high potential wiring providing a first power supply voltage high potential (VHA) and a first low potential wiring providing a first power supply voltage low potential (VLA) And the second power supply wiring may include a second high potential wiring providing a second power supply voltage high potential (VHB) and a second low potential wiring providing a second power supply voltage low potential (VLB).

According to another aspect of the present invention, there is provided a signal processing circuit including a signal processing circuit for receiving and processing a signal corresponding to a capacitance of a fingerprint from a sensor array, and a power supply circuit for providing a power supply voltage high potential and a power supply voltage low potential to the signal processing circuit A fingerprint detection method performed by a fingerprint detection device, wherein the signal processing circuit receives a first high potential level (VH1) and a first low potential level (VL1) from the power supply circuit and receives the first high potential level (VH1) And a reference state detecting step of detecting a reference state using a difference between the first low potential level (VL1) as a power supply voltage; Wherein the signal processing circuit receives a second high potential level (VH2) and a second low potential level (VL2) from the power supply circuit and receives the difference between the second high potential level (VH2) and the second low potential level A fingerprint detection step of detecting a fingerprint state using a power supply voltage; And the signal processing circuit receives the third high potential level (VH3) and the third low potential level (VL3) from the power supply circuit and receives the third high potential level (VH3) and the third low potential level And evaluating the fingerprint state using the difference as a power supply voltage.

In the fingerprint detection method, the first low potential level (VL1) and the second low potential level (VL2) may be different from each other.

Wherein the difference between the first high potential level (VH1) and the first low potential level (VL1), the difference between the second high potential level (VH2) and the second low potential level (VL2) And the difference between the third high potential level (VH3) and the third low potential level (VL3) may be substantially the same.

In the fingerprint detection method, the signal processing circuit may include an operational amplifier receiving a reference voltage through an input terminal, and the difference between the reference voltage and the second low potential level (VL2) May be different from the difference between the reference voltage and the first low potential level (VL1) in the state detecting step.

In the fingerprint detection method, the reference state detection step, the fingerprint detection step, and the evaluation step may be performed sequentially.

In the fingerprint detection method, the reference state detection step and the fingerprint detection step may be performed sequentially, and the evaluation step may be performed simultaneously with the reference state detection step and the fingerprint detection step.

According to the present invention, the potential of the fingerprint can be stably maintained without applying the excitation signal for detecting the fingerprint directly to the fingerprint, thereby reducing the influence of noise and improving the accuracy of fingerprint detection.

Further, according to the present invention, the excitation signal for fingerprint detection can be easily varied to increase the detection sensitivity and improve the accuracy of fingerprint detection.

1 illustrates a fingerprint detection apparatus according to an embodiment of the present invention.
Fig. 2 exemplarily and schematically shows a partial configuration of a fingerprint detection apparatus according to an embodiment of the present invention.
FIG. 3 is an exemplary diagram illustrating a power supply voltage waveform in three operation modes.
4 illustrates a fingerprint detection apparatus according to another embodiment of the present invention.
5 is an exemplary diagram illustrating another embodiment of the supply voltage waveform in three operation modes.
6 illustrates a fingerprint detection apparatus according to another embodiment of the present invention.
7 illustrates a fingerprint detection apparatus according to another embodiment of the present invention.
8 illustrates a fingerprint detection apparatus according to another embodiment of the present invention.
Figure 9 illustrates an equivalent circuit for calculating the voltage gain.
Figure 10 illustrates waveforms of the main parameters of the equivalent circuit of Figure 9;
11 illustrates a fingerprint detection method according to another embodiment of the present invention.
12 is a diagram illustrating a power supply voltage waveform according to another embodiment of the present invention.

Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. It should be noted that, in adding reference numerals to the constituent elements of the drawings, the same constituent elements are denoted by the same reference symbols as possible even if they are shown in different drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

In describing the components of the present invention, terms such as first, second, A, B, (a), and (b) may be used. These terms are intended to distinguish the constituent elements from other constituent elements, and the terms do not limit the nature, order or order of the constituent elements. When a component is described as being "connected", "coupled", or "connected" to another component, the component may be directly connected to or connected to the other component, It should be understood that an element may be "connected," "coupled," or "connected."

FIG. 1 illustrates a fingerprint detection apparatus 100 according to an embodiment of the present invention. Referring to FIG. 1, the fingerprint detection apparatus 100 may include a sensor array 110, a signal processing circuit 130, and a power supply circuit 150.

The sensor array 110 is provided with a signal for fingerprint detection from the signal processing circuit 130 and may provide a signal corresponding to the shape of the fingerprint to the signal processing circuit 130.

The signal processing circuit 130 may provide a signal for fingerprint detection to the sensor array 110 and may receive and process a signal corresponding to the fingerprint capacitance from the sensor array 110. The signal processing circuit 130 can operate by receiving the power supply voltage from the power supply circuit 150 through the power supply line PL. The power supply line PL may be composed of a pair of wirings, and the pair of wirings may be composed of a high potential wiring providing a high power supply voltage and a low potential wiring providing a power supply voltage low potential. The signal processing circuit 130 can use the difference between the power supply voltage high potential supplied from the high potential wiring and the power supply voltage low potential supplied through the low potential wiring as the power supply voltage. The power supply voltage low potential supplied through the low potential wiring can be used as the signal processing circuit reference potential which is a reference of the operation of the signal processing circuit. The power supply voltage low potential can be varied with respect to the virtual reference potential (VGND) corresponding to the potential of the fingerprint according to the operation mode, which will be described in detail below.

The power supply circuit 150 can supply various voltages to be used in the signal processing circuit 130 and supply the signal to the signal processing circuit 130 by receiving the power supply Vcc from the outside. The voltage that the power supply circuit 150 supplies to the signal processing circuit 130 may include a power supply voltage high potential and a power supply voltage low potential.

Fig. 2 exemplarily and schematically shows a partial configuration of a fingerprint detection apparatus according to an embodiment of the present invention. Fig. 2 is a simplified illustration of only some of the configurations of the sensor array and the signal processing circuit that are necessary for the description of this embodiment.

Referring to FIG. 2, the sensor array may include a sensing electrode 220, a feedback electrode 230, a protective layer 240, and an insulating layer 250. It is obvious that the sensor array may include various other configurations.

The fingerprint capacitance Cf is a capacitance formed between the sensing electrode 220 and the fingerprint 210. The sensing electrode 220 may be electrically connected to the signal processing circuit through a wiring. In FIG. 2, the sensing electrode 220 is illustrated as being electrically connected to the input terminal (-) of the amplifier through the first switching device S1.

The fingerprint capacitance Cf may have a capacitance value depending on the shape of the fingerprint between the sensing electrode 220 and the finger. The fingerprint 210 may be electrically connected to the device reference potential (ground), but the fingerprint 210 may not be connected to a specific reference potential.

The feedback capacitance Cg is a capacitance formed between the feedback electrode 230 and the sensing electrode 220. The feedback electrode 230 may be electrically connected to the signal processing circuit through the wiring. In FIG. 2, the feedback electrode 230 is illustrated as being electrically connected to the output terminal of the amplifier (A). The output terminal of the amplifier A may be connected to the negative input terminal (-) of the amplifier through the second switching element S2 to perform a feedback function.

The protective layer 240 may be formed on top of the sensor array to protect the sensor array from ESD, mechanical shock or wear, and the like. The protective layer 240 may include a known material such as resin and glass, and may include a general insulating layer.

The insulating layer 250 may be added for electrical insulation between the sensing electrode 220 and the feedback electrode 230. As the insulating layer 250, a usual insulating material such as SiO 2, SiN, glass, or the like can be used. The insulating layer 250 may function to adjust the feedback capacitance Cg between the sensing electrode 220 and the feedback electrode 230 in addition to the insulating function. The feedback capacitance Cg can be controlled not only by the sizes of the sensing electrode 220 and the feedback electrode 230 but also through the thickness and permittivity of the insulating layer 250 and the like.

In addition to the configuration illustrated in FIG. 2, a variety of metal layers, insulating layers, and the like may be added to the sensor array, and detailed description thereof will be omitted in order to avoid obscuring the gist of the present invention.

The amplifier A, the first switching element S1, the second switching element S2, the amplifier reference voltage Vref, the power supply voltage high potential VH and the power supply voltage low potential VL shown in Fig. A part of the processing circuit is exemplified.

The negative input terminal (-) of the amplifier is electrically connected to the sensing electrode 220 through the first switching element S1, the positive input terminal (+) of the amplifier is connected to the amplifier reference voltage Vref, The output terminal of the amplifier A may be connected to the input terminal (-) of the amplifier sound through the second switching element S2. The amplifier A can be used as an analog power source by receiving the high voltage VH of the power supply voltage and the low potential VL of the power supply voltage. In this case, the power supply voltage low potential (VL) can be used as a reference potential (ground) for signal processing of the amplifier (A).

The first switching device S1 may selectively connect the sensing electrode 220 to the negative input terminal of the amplifier and the second switching device S2 may selectively connect the negative input terminal of the amplifier to the negative input terminal of the amplifier, A) output terminal can be selectively connected. For example, the first switching element S1 is turned off in the reference state detection mode so that the amplifier A can generate the output voltage in the state in which the influence of the fingerprint is excluded, the amplifier A is turned on in the fingerprint detection mode, To generate an output voltage that is affected by the state of the fingerprint. Further, the first switching device S1 can be controlled to be on / off controlled so as not to be affected by the operation of the adjacent sensor unit. The second switching element S2 may be used to initialize (discharge) the feedback capacitance Cg.

The configuration related to the amplifier A illustrated in FIG. 2 is one example, and the signal processing circuit of the present embodiment is not limited to the example illustrated in FIG. 2, and various modifications are possible.

3 is a diagram exemplarily showing a power supply voltage waveform supplied from a power supply circuit to a signal processing circuit in three operation modes.

Referring to Fig. 3, the fingerprint detection apparatus of this embodiment can operate in three operation modes. The first mode (mode 1) may be a reference state detection mode, the second mode (mode 2) may be a fingerprint detection mode, and the third mode (mode 3) may be an evaluation mode.

The reference state detection mode (mode 1) may be an operation mode for detecting the state of the sensor array and / or the signal processing circuit in the absence of the influence of the fingerprint. The fingerprint detection mode (mode 2) may be an operation mode for detecting information on the status of the sensor array and / or the signal processing circuit while reflecting the influence of the fingerprint. The evaluation mode (mode 3) may be an operation mode for evaluating the state of the fingerprint based on the information detected in the reference state detection mode and the fingerprint detection mode.

FIG. 3 illustrates four cases (case 1, case 2, case 3, case 4) of the waveforms of the power supply voltage high potential VH and the power supply voltage low potential VL in three operation modes. In the four examples, both the power supply voltage high potential (VH) and the power supply voltage low potential (VL) show the magnitude relative to the virtual reference potential (VGND). It can be understood that the virtual reference potential VGND recognizes the potential of the fingerprint as a virtual reference potential.

In the reference state detection mode (mode 1), the power supply voltage high potential VH may have a first high potential level VH1 and the power supply voltage low potential VL may have a first low potential level VL1. The first high potential level VH1 and the first low potential level VL1 may be selectively provided to the circuits operating in the reference state detection mode (mode 1) among the signal processing circuits and used as a power supply voltage.

In the fingerprint detection mode (mode 2), the power supply voltage high potential VH may have the second high potential level VH2 and the power supply voltage low potential VL may have the second low potential level VL2. The second high potential level VH2 and the second low potential level VL2 may be selectively provided to circuits operating in the fingerprint detection mode (mode 2) among the signal processing circuits and used as a power supply voltage.

In the evaluation mode (mode 3), the power supply voltage high potential VH may have the third high potential level VH3 and the power supply voltage low potential VL may have the third low potential level VL3. The third high potential level VH3 and the third low potential level VL3 may be selectively provided to the circuits operating in the evaluation mode (mode 3) among the signal processing circuits and used as a power supply voltage.

At this time, the difference between the power supply voltage high potential (VH) and the power supply voltage low potential (VL) remains substantially constant in all three modes despite the change of the operation mode, It can be used as the power supply voltage of the processing circuit. And stable operation is possible when the power supply voltage is maintained constant. However, since the difference between the power supply voltage high potential (VH) and the power supply voltage low potential (VL) must not be kept constant to be used as the power supply voltage, the present embodiment is not limited to keeping the difference constant.

The first case (case 1) illustrated in FIG. 3 illustrates a case where VH1> VH3> VH2, and VL1> VL3> VL2. The second case (case 2) illustrates the case where VH2> VH1> VH3, and VL2> VL1> VL3. The third case (case 3) illustrates the case where VH1> VH2> VH3, and VL1> VL2> VL3. The fourth case (case 4) illustrates the case where VH3> VH2> VH1, and VL3> VL2> VL1. As described above, the first low potential level VL1, the second low potential level VL2 and the third low potential level VL3 can have different levels according to the operation mode, and the high and low potentials The level can be set to various levels. Although the first low potential level VL1, the second low potential level VL2, and the third low potential level VL3 are illustrated as having different levels according to the operation mode in FIG. 3, The third low potential level VL3 may be set to be equal to either the first low potential level VL1 or the second low potential level VL2.

As illustrated in Fig. 3, the power supply voltage low potential VL can be varied with respect to the virtual reference potential VGND according to the operation mode. The power supply voltage low potential VL can be used as a reference potential (ground) of the signal processing circuit. In this case, the reference potential of the signal processing circuit is varied according to the operation mode when the virtual reference potential VGND is used as a reference. When the potential of the fingerprint is the virtual reference potential (VGND), a change in the power supply voltage low potential (VL) relative to the virtual reference potential (VGND) can be understood as an excitation voltage applied to the fingerprint capacitance.

For example, when it is assumed that the amplifier reference voltage Vref illustrated in FIG. 2 is maintained at a constant potential with respect to the signal processing circuit reference potential VL, the amplifier reference voltage Vref is set to be higher than the virtual reference potential VGND The electric potential changes according to the operation mode and the potential difference between the fingerprint having the virtual reference electric potential VGND and the input terminal (-) of the amplifier sound is changed. Therefore, the fingerprint capacitance Cf and the feedback electrostatic capacitance Cg Current flows. The signal processing circuit can obtain fingerprint information from the current flow through the fingerprint capacitance (Cf) and the feedback capacitance (Cg) to recognize the fingerprint.

In this manner, when the power supply voltage high potential VH and the power supply voltage low potential VL are set differently in the three operation modes, the signal processing circuit reference potential (i.e., VL2) used in the fingerprint detection mode (mode 2) Can be set differently from the signal processing circuit reference potential (i.e., VL3) used in the evaluation mode (mode 3), so that the magnitude of the excitation signal for fingerprint detection (that is, the change in Vref with respect to the virtual reference potential VGND) There is an advantage that it can be.

Although it is assumed that the amplifier reference voltage Vref maintains a constant potential relative to the signal processing circuit reference potential for the convenience of the foregoing description, even if the amplifier reference voltage Vref does not maintain the same potential with respect to the signal processing circuit reference potential The principle of the fingerprint detection can be similarly applied. In this case, by adjusting the excitation signal by appropriately changing the amplifier reference voltage Vref, the sensing gain can be increased to improve the accuracy of detection, which will be described later .

4 illustrates a fingerprint detection apparatus 400 according to another embodiment of the present invention. Referring to FIG. 4, the fingerprint detection device 400 may include a sensor array 410, a signal processing circuit 430, and a power supply circuit 450.

The fingerprint detecting device 400 of FIG. 4 may operate similarly to the fingerprint detecting device 100 described with reference to FIG. 1 except that the signal processing circuit 430 and the power supply circuit 450 are connected to the first power supply line PL1 and the second power supply line PL2. That is, the signal processing circuit 430 can receive two kinds of power from the power supply circuit 450 through the first power supply line PL1 and the second power supply line PL2. In this case, the signal processing circuit 430 can sequentially receive the power to be used in the reference state detection mode and the power source to be used in the fingerprint detection mode through the first power wiring line PL1, Mode power supply.

In the embodiment of FIG. 4, the signal processing circuit 430 may internally separate the two types of power supplied through the two power lines PL1 and PL2 and provide the power to the circuit. For example, the power supply to be used in the reference state detection mode and the power source to be used in the fingerprint detection mode are sequentially supplied through the first power supply line PL1 to the internal circuit performing the reference state detection and fingerprint detection operation, It can be supplied to the internal circuit which receives the power to be used in the evaluation mode through the power supply line PL2 and performs the evaluation operation.

FIG. 5 is a graph showing the relationship between the first power supply voltage high potential VHA and the first power supply voltage VH when the signal processing circuit receives two kinds of power from the power supply circuit through the first power supply line PL1 and the second power supply line PL2, (VLA), a second power supply voltage high potential (VHB), and a second power supply voltage low potential (VLB) waveform. The four voltages VHA, VLA, VHB and VLB all show the voltage level with reference to the virtual reference potential VGND.

Referring to FIG. 5, the first power supply voltage high potential VHA transmitted through the first power supply line PL1 has a first high potential level VH1 in the reference state detection mode (mode 1) mode 2) and the second high potential level (VH2) in the evaluation mode (mode 3). The first power supply voltage low potential VLA transmitted through the first power supply line PL1 has a first low potential level VL1 in the reference state detection mode (mode 1) (mode 3) and a second low potential level VL2.

The second power supply voltage high potential VHB transmitted through the second power supply line PL2 is supplied to the third high potential level VHB in the reference state detection mode (mode 1), the fingerprint detection mode (mode 2) And the second power supply voltage low potential VLB may have the third low potential level VL3 in the reference state detection mode (mode 1), the fingerprint detection mode (mode 2), and the evaluation mode (mode 3) Lt; / RTI >

In this way, when the signal processing circuit divides the circuit for performing the reference state detection and the fingerprint detection and the circuit for performing the evaluation function to supply the power, the circuit performing the evaluation function can perform stable operation without changing the reference potential Since the reference potential can be used, the circuit for performing the reference state detection and the fingerprint detection function can freely change the reference potential, so that the excitation voltage applied to the fingerprint capacitance can be freely set and the accuracy of the fingerprint detection can be enhanced.

The first power supply line PL1 and the second power supply line PL2 illustrated in Fig. 4 may include low-potential wiring and high-potential wiring, respectively. For example, the first power supply line PL1 may include a first high potential wiring providing a first power supply voltage high potential (VHA) and a first low potential wiring providing a first power supply voltage low potential (VLA) And the second power supply line PL2 may include a second high potential wiring for providing a second power supply voltage high potential VHB and a second low potential wiring for providing a second power supply voltage low potential VLB have.

6 illustrates a fingerprint detection apparatus 600 according to another embodiment of the present invention. 6, the fingerprint detection device 600 may include a sensor array 610, a first signal processing circuit 631, a second signal processing circuit 633, and a power supply circuit 650.

The fingerprint detecting apparatus 600 according to the embodiment of FIG. 6 includes a first signal processing circuit 631 and a second signal processing circuit 633 as compared with the fingerprint detecting apparatus 400 according to the embodiment of FIG. 4 There is a difference in point. For example, the signal processing circuit 430 of FIG. 4 may be separated into a first signal processing circuit 631 and a second signal processing circuit 633 as shown in FIG. Here, 'separation' may be a spatial separation, but may not be spatially separated but may be separated from a reference potential (ground) perspective.

The first signal processing circuit 631 includes a circuit that operates for reference state detection and fingerprint detection and receives a first power supply voltage high potential and a first power supply voltage low potential through the first power supply line PL1 can do. For example, the first signal processing circuit 631 may include circuitry for applying an excitation signal to the sensor array 610 and detecting the response of the sensor array to the excitation signal, circuitry for processing the control signal, Circuits, and the like.

The second signal processing circuit 633 includes a circuit which operates for the evaluation mode and can operate by receiving the second power supply voltage high potential and the second power supply voltage low potential via the second power supply line PL2. For example, the second signal processing circuit 633 may include a sample and hold, a gain amplifier, an analog-to-digital converter, and the like.

The power supply voltage supplied through the first power supply line PL1 and the second power supply line PL2 may be similar to the embodiment of Fig. The first power supply voltage low potential VLA supplied through the first power supply line PL1 has the first low potential level VL1 in the reference state detection mode (mode 1) (mode 3) and a second low potential level VL2. For example, the first power supply voltage low potential VLA can maintain the second low potential level VL2 which is substantially equal to the fingerprint detection mode (mode 2) in the evaluation mode (mode 3). In this case, the circuit used for fingerprint detection does not change the operation reference potential (ground) in the fingerprint detection mode (mode 2) and the evaluation mode (mode 3), so the fingerprint detection mode (mode 2) The signal obtained from the signal processing apparatus can be stably maintained.

The second power supply voltage low potential VLB supplied through the second power supply line PL2 is substantially the same in the reference state detection mode (mode 1), the fingerprint detection mode (mode 2) and the evaluation mode (mode 3) The low potential level VL3 can be maintained. In this case, the second signal processing circuit 633 including the circuit operating in the evaluation mode can operate stably because there is no change in the operation reference potential. The third low potential level VL3 may be different from the first low potential level VL1 and the second low potential level VL2 but the first low potential level VL1 and the second low potential level VL2, It may be the same level as any one of them.

FIG. 7 illustrates a fingerprint detection apparatus 700 according to another embodiment of the present invention. 7, the fingerprint detection device 700 includes a sensor array 710, a first signal processing circuit 731, a second signal processing circuit 733, a first power supply circuit 751, and a second power supply circuit 753).

7 differs from the fingerprint detection device 600 of FIG. 6 in that it includes a first power supply circuit 751 and a second power supply circuit 753 There is a difference. For example, the power supply circuit 650 of FIG. 6 may be separated into a first power supply circuit 751 and a second power supply circuit 753 as shown in FIG.

The first power supply circuit 751 may receive the power supply Vcc from the outside and may provide the first power supply voltage to the first signal processing circuit 731 through the first power supply line PL1. The second power supply circuit 753 may receive the power supply Vcc from the outside and provide the second power supply voltage to the second signal processing circuit 733 through the second power supply line PL2. Here, the first power supply voltage supplied through the first power supply line PL1 and the second power supply voltage supplied through the second power supply line PL2 may be similar to those described with reference to FIGS.

FIG. 8 illustrates a fingerprint detection device 800 according to another embodiment of the present invention. 8, the fingerprint detection device 800 includes a sensor array 810, a first signal processing circuit 831, a second signal processing circuit 833, a level shifter 835, a first power supply circuit 851, And a second power supply circuit 853.

The fingerprint detecting apparatus 800 according to the embodiment of FIG. 8 differs from the fingerprint detecting apparatus 700 according to the embodiment of FIG. 7 in that it includes a level shifter 835. As described above, the first signal processing circuit 831 can perform the reference state detection and the fingerprint detection using the first power supply voltage supplied through the first wiring PL1, and the second signal processing circuit 833 operate using the second power supply voltage supplied through the second wiring line PL2 to receive the signal detected by the first signal processing circuit 831 and perform an evaluation function for the detected signal. In this case, since the first signal processing circuit 831 and the second signal processing circuit 833 can operate at different reference potentials and voltage levels, the first signal processing circuit 831 and the second signal processing circuit 833 An adjustment to the operating voltage difference may be necessary. The level shifter 835 converts the signal detected by the first signal processing circuit 831 into a signal of a voltage level usable in the second signal processing circuit 833 and provides the signal to the second signal processing circuit 833 Can be performed. Although the level shifter 835 is illustrated as being separate from the first signal processing circuit 831 and the second signal processing circuit 833 in Fig. 8, the level shifter 835 includes the first signal processing circuit 831 and the second signal processing circuit 833, Or may be included in any one of the second signal processing circuits 833.

Fig. 9 illustrates an equivalent circuit for calculating the voltage gain of the signal processing circuit, and Fig. 10 illustrates an exemplary waveform of the main parameters of the equivalent circuit of Fig.

9, the fingerprint capacitance Cf is connected between the virtual reference potential VGND and the negative input terminal (-) of the amplifier, and the feedback capacitance Cg is connected to the negative input terminal (-) of the amplifier. And the amplifier output terminal. When the amplifier reference voltage Vref is varied with respect to the virtual reference potential VGND, the change in the amplifier reference voltage Vref becomes the excitation voltage, so that information on the fingerprint capacitance Cf can be obtained. 9 is an equivalent circuit that can be applied to a method of using a change in the amplifier reference voltage Vref as an excitation voltage.

The amplifier reference voltage Vref, the amplifier output voltage Vo, the feedback capacitance voltage Vcg, and the upper voltage Vc are calculated to calculate the amplifier output voltage Vo through the equivalent circuit of Fig. The voltage change amount according to the mode change can be defined as illustrated in FIG. The first mode (mode 1) may be a reference state detection mode, and the second mode (mode 2) may be a fingerprint detection mode.

10, the power supply voltage low potential VL, the amplifier reference voltage Vref, the amplifier output voltage Vo, and the feedback capacitance voltage Vcg all have a voltage level based on the virtual reference potential VGND And the virtual reference potential VGND may be the potential of the fingerprint. The power supply voltage low potential VL, the amplifier reference voltage Vref, the amplifier output voltage Vo and the feedback capacitance voltage Vcg are both higher than the first mode (mode 1) Level, which can be interpreted to be due to a change in the amplifier reference voltage Vref. The amount of change ΔVref of the amplifier reference voltage may include ΔVp which is the variation amount of the power source voltage low potential VL and ΔVr which is the amount of variation of the amplifier reference voltage Vref itself.

Vr1, which is the variation amount of the amplifier reference voltage Vref, is calculated by multiplying the amplitude Vref1-VL1 of the reference voltage Vref1 with respect to the amplifier reference voltage VL1 in the first mode (mode 1) (Vref2 - VL2) of the reference voltage (Vref2) to the amplifier reference potential (VL2) in the first mode (mode 2). That is, the amount of change of the reference voltage Vref when the amplifier reference potential VL is taken as a reference.

[Equation 1]

As described above, the difference between the reference voltage Vref2 and the second low potential level VL2 in the fingerprint detection mode (mode 2) is the difference between the reference voltage Vref1 in the reference state detection mode (mode 1) (VL1). Vr represents the magnitude of the reference voltage Vref with respect to the amplifier reference potential VL except for the change by the change amount DELTA Vp which is the variation amount of the power supply voltage low potential VL from the total variation amount DELTA Vref of the reference voltage Vref It may be understood as an amount that has been changed by itself. DELTA Vo is a change amount of the amplifier output voltage, and DELTA Vcg is a voltage change amount of the feedback capacitance Cg.

9 and 10, the change amount of the amplifier output voltage Vo can be calculated. First, the amplifier output voltage Vo1 in the first mode (mode 1) can be calculated from the amplifier reference voltage Vref1 and the feedback capacitance voltage Vcg1 as shown in Equation 2 below. Equation 2 assumes that the input terminal (-) of the amplifier sound is at the same potential as the positive input terminal (+) when the amplifier A is ideal.

&Quot; (2) "

When the mode is switched from the first mode (mode 1) to the second mode (mode 2), the potential difference between the input terminal (-) of the amplifier sound and the virtual reference potential VGND changes due to the change amount ΔVref of the amplifier reference voltage And the current flows to the fingerprint capacitance Cf. Since the current flowing in the fingerprint capacitance Cf is supplied from the output terminal of the amplifier A through the feedback capacitance Cg, the potential of the feedback capacitance Cg also changes. If the potential Vcg2 of the feedback capacitance in the second mode (mode 2) is derived using the principle that the amount of charge change of the fingerprint capacitance Cf is the same as the amount of change in charge of the feedback capacitance Cg, Respectively.

&Quot; (3) "

The output voltage Vo2 in the second mode is calculated using Equation 3 and then the difference Vo between the output voltage Vo1 in the first mode obtained in Equation 2 is calculated, same.

&Quot; (4) "

One thing to consider in Equation (4) is that the output voltage change amount? Vo is a change amount of the amplifier output voltage Vo with reference to the virtual reference potential VGND. Since the signal processing circuit including the amplifier A and its peripheral circuit uses the power supply voltage low potential VL as the reference voltage (ground), the amplifier output voltage recognized by the signal processing circuit is the output voltage Vo Is the value obtained by subtracting the power supply voltage low potential (VL). Therefore, the change amount? Vo 'of the amplifier output voltage from the viewpoint of the signal processing circuit can be defined as shown in Equation (5) below.

&Quot; (5) "

Substituting Equation (4) into Equation (5), the amount of change (? Vo ') of the amplifier output voltage in terms of the signal processing circuit can be calculated by Equation (6) below.

&Quot; (6) "

As can be seen from Equation (6), according to the fingerprint detection apparatus according to the embodiment of the present invention, the amount of change (? Vo ') of the amplifier output voltage from the viewpoint of the signal processing circuit is also the power supply voltage low potential change amount (Vr) of the amplifier reference voltage, thereby increasing the detection sensitivity by increasing the amount of change in the output signal when detecting the fingerprint capacitance (Cg). have.

11 illustrates a fingerprint detection method according to another embodiment of the present invention. The fingerprint detection method illustrated in Fig. 11 can be performed by any of the embodiments of the various fingerprint detection devices described with reference to Figs. The fingerprint detection method illustrated in FIG. 11 will be described with reference to FIG.

In step S1110, the signal processing circuit receives the first high potential level VH1 and the first low potential level VL1 from the power supply circuit and receives the difference between the first high potential level VH1 and the first low potential level VL1 Can be used as a power supply voltage to detect the reference state.

In step S1130, the signal processing circuit receives the second high level (VH2) and the second low level (VL2) from the power supply circuit and receives the difference between the second high level (VH2) and the second low level Can be used as a power supply voltage to detect the fingerprint state.

In step S1150, the signal processing circuit receives the third high potential level VH3 and the third low potential level VL3 from the power supply circuit and receives the difference between the third high potential level VH3 and the third low potential level VL3 The power supply voltage can be used to evaluate the fingerprint status.

The first low potential level VL1, the second low potential level VL2 and the third low potential level VL3 may be set to be different from each other in the case of performing the fingerprint detection method illustrated in Fig. 11, Since the signal processing circuit reference potential (ground) used in the fingerprint detection step can be set different from the signal processing circuit reference potential (ground) used in the evaluation step, the magnitude of the excitation signal for fingerprint detection can be freely set. However, the present embodiment is not limited in this manner, and the third low potential level VL3 may be the same as either the first low potential level VL1 or the second low potential level VL2.

The difference between the first high potential level VH1 and the first low potential level VL1, the difference between the second high potential level VH2 and the second low potential level VL2, and the difference between the third high potential level VH3, And the third low potential level VL3 may be substantially equal to each other. In this case, since the power supply voltage of the signal processing circuit is commonly kept constant in three stages, stable signal processing is possible.

The difference between the amplifier reference voltage and the second low potential level VL2 in the fingerprint detection step can be set to be different from the difference between the amplifier reference voltage and the first low potential level VL1 in the reference state detection step, In this case, as described with reference to Fig. 10, since the output voltage is influenced not only by the variation amount (? Vp) of the power supply voltage low potential but also the variation amount (? Vr) of the amplifier reference voltage itself, .

12 is a diagram exemplarily showing a power supply voltage waveform supplied to a signal processing circuit according to another embodiment.

12, the reference state detection mode (mode 1) and the fingerprint detection mode (mode 2) are sequentially performed, and the evaluation mode (mode 3) is a reference state detection mode (mode 1) ). ≪ / RTI > In this case, since there is no need to allocate a separate time for the evaluation mode (mode 3), it is possible to operate at a high speed. In this case, the evaluation mode (mode 3) is a mode in which the signals detected through the reference state detection mode (mode 1) and the fingerprint detection mode (mode 2) in the previous step are processed in the current step, And the fingerprint detection mode (mode 2). However, the present embodiment is not limited to this, and the signals detected through the reference state detection mode (mode 1) and the fingerprint detection mode (mode 2) Can be processed at the same time.

12, the first power supply voltage high potential VHA, the first power supply voltage low potential VLA, and the second power supply line PL2, which are supplied to the signal processing circuit through the first power supply line PL1, The second power supply voltage high potential VHB and the second power supply voltage low potential VLB that are supplied to the second power supply voltage VLB may be similar to those described with reference to FIG.

11, the reference state detecting step (S1110) and the fingerprint detecting step (S1130) are sequentially performed, and the evaluation step (S1150) is performed in the same manner as described above with reference to Fig. 12 The reference state detecting step S1110 and the fingerprint detecting step S1130.

As described above, according to the embodiments of the present invention, by using the reference potential having a different level from each other for the virtual reference potential (e.g., fingerprint potential) in the reference state detection mode, the fingerprint detection mode, and the evaluation mode, And the circuit performing the evaluation function can stably operate by keeping the reference potential constant in spite of the mode change. In addition, as the excitation signal for fingerprint detection, not only the change in the power supply voltage low potential but also the change in the amplifier reference voltage itself can be used to increase the detection sensitivity of the fingerprint capacitance.

It is to be understood that the terms "comprises", "comprising", or "having" as used in the foregoing description mean that the constituent element can be implanted unless specifically stated to the contrary, But should be construed as further including other elements. All terms, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, unless otherwise defined. Commonly used terms, such as predefined terms, should be interpreted to be consistent with the contextual meanings of the related art, and are not to be construed as ideal or overly formal, unless expressly defined to the contrary.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

Claims (17)

A signal processing circuit including an amplifier for receiving and processing a signal corresponding to a capacitance due to a fingerprint from the sensor array; And
And a power supply circuit for providing the signal processing circuit with two types of power supplies: a first power supply voltage and a second power supply voltage,
The first power supply voltage is provided in a pair of a first power supply voltage high potential (VHA) and a first power supply voltage low potential (VLA), and the second power supply voltage is supplied to a second power supply voltage high potential (VHB) Are provided in a pair of voltage low potential (VLB)
Wherein the signal processing circuit uses the first power supply voltage in the reference state detection mode and the fingerprint detection mode and uses the second power supply voltage in the evaluation mode,
The first power supply voltage low potential (VLA) is changed to a predetermined variation amount (? Vp) with respect to the virtual reference potential when the reference state detection mode is switched to the fingerprint detection mode, and the reference voltage of the amplifier Is changed to its own change amount (DELTA Vr) with respect to one power supply voltage low potential (VLA)
The variation amount? Vp of the first power supply voltage low potential and the variation amount? Vr of the amplifier reference voltage itself are included in the variation amount? Vref of the amplifier reference voltage and used as the excitation voltage for fingerprint detection The fingerprint detection device comprising: The method of claim 1, wherein the difference between the first power supply voltage high potential (VHA) and the first power supply voltage low potential (VLA) is kept constant in the reference state detection mode and the fingerprint detection mode Device. delete delete delete delete The fingerprint detection device according to claim 1, wherein the second power supply voltage low potential (VLB) maintains the same potential with respect to the virtual reference potential in the reference state detection mode, the fingerprint detection mode, and the evaluation mode. delete The fingerprint detection apparatus according to claim 1, wherein the reference state detection mode, the fingerprint detection mode, and the evaluation mode are sequentially performed. The method according to claim 1,
Wherein the reference state detection mode and the fingerprint detection mode are sequentially performed,
Wherein the evaluation mode is performed simultaneously with the reference state detection mode and the fingerprint detection mode. The method according to claim 1,
Wherein the first power supply voltage and the second power supply voltage are provided through different power wiring lines. A signal processing circuit including an amplifier for receiving and processing a signal corresponding to a capacitance due to the fingerprint from the sensor array, and a signal processing circuit provided in a pair of the first power supply voltage high potential (VHA) and the first power supply voltage low potential And a second power supply voltage provided as a pair of a first power supply voltage, a second power supply voltage high potential (VHB) and a second power supply voltage low potential (VLB) to the signal processing circuit A fingerprint detection method performed by a fingerprint detection device comprising:
A reference state detecting step in which the signal processing circuit detects a reference state using the first power supply voltage;
A fingerprint detection step in which the signal processing circuit detects the fingerprint state using the first power supply voltage; And
And an evaluation step of the signal processing circuit evaluating a fingerprint state using the second power supply voltage,
Wherein the first power supply voltage low potential (VLA) is changed to a predetermined variation amount (? Vp) with respect to a virtual reference potential when the reference state detecting step is switched to the fingerprint detecting step, and the reference voltage of the amplifier Is changed to its own change amount (DELTA Vr) with respect to one power supply voltage low potential (VLA)
The variation amount? Vp of the first power supply voltage low potential and the variation amount? Vr of the amplifier reference voltage itself are included in the variation amount? Vref of the amplifier reference voltage and used as the excitation voltage for fingerprint detection The fingerprint detection method comprising: delete 13. The method of claim 12, wherein the difference between the first power supply voltage high potential (VHA) and the first power supply voltage low potential (VLA) is kept constant in the reference state detection step and the fingerprint detection step Way. The fingerprint detection method according to claim 12, wherein the second power supply voltage low potential (VLB) maintains the same potential with respect to the virtual reference potential in the reference state detection step, the fingerprint detection step, and the evaluation step. The fingerprint detection method according to claim 12, wherein the reference state detection step, the fingerprint detection step, and the evaluation step are performed sequentially. The method of claim 12,
Wherein the reference state detecting step and the fingerprint detecting step are sequentially performed,
Wherein the evaluating step is performed simultaneously with the reference state detecting step and the fingerprint detecting step.

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