KR101613123B1 - Fingerprint detecting apparatuse and driving signal attenuation compensation method - Google Patents

Abstract

According to an embodiment, an external electrode to which a driving signal is applied; A sensor array including a plurality of sensor pads for outputting a response signal in response to application of the driving signal, the sensor array being disposed adjacent to the external electrodes; A driving signal supplier including a buffer for outputting the driving signal according to a predetermined gain corresponding to an input signal; And a compensating unit for compensating for the attenuation of the driving signal based on the magnitude of the driving signal output from the driving signal supplying unit.

Description

TECHNICAL FIELD [0001] The present invention relates to a fingerprint detection device and a driving signal attenuation compensation method for the fingerprint detection device,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a fingerprint detection apparatus and a method for compensating a drive signal attenuation thereof, and more particularly, And a driving signal attenuation compensation method therefor.

Since fingerprints vary from person to person, they are widely used in the field of personal identification. In particular, fingerprints are widely used in various fields such as finance, crime investigation and security as personal authentication means.

A fingerprint recognition sensor has been developed to recognize these fingerprints and identify them. The fingerprint recognition sensor is a device for recognizing a fingerprint of a finger by contacting a finger of a person, and is used as a means for determining whether or not the user is a legitimate user.

Various recognition methods such as an optical method, a thermal sensing method, and a capacitive sensing method are known as a method of implementing a fingerprint recognition sensor. Among them, the capacitive type fingerprint recognition sensor acquires the shape of the fingerprint (fingerprint pattern) by detecting the change of capacitance according to the shape of the fingerprint and the floor when the finger surface of the person touches the conductive detection pattern.

In recent years, various additional functions utilizing personal information such as finance and security have been provided not only in communication functions such as telephone and text message transmission service through portable devices, but also in the necessity of locking devices of portable devices. . In order to improve the locking effect of such a portable device, a terminal equipped with a locking device through fingerprint recognition is being developed in earnest.

When a fingerprint is sensed, a driving signal is applied and sensing is performed based on the response signal. At this time, each sensing pad can sense an accurate response signal only when the driving signal is applied to the finger to be sensed. However, in actual fingerprint recognition, the user holds the terminal with one hand and senses the fingerprint of the other hand. At this time, the drive signal is distributed from the finger to be sensed through the metal case part of the terminal in contact with the hand holding the terminal. That is, the driving signal may be voltage-divided and attenuated by the finger to be sensed, another circuit configuration connected to the metal case, and the like.

As the driving signal is attenuated, the output signal from the sensor pad for outputting the response in response to the driving signal supply can also be attenuated in size and output, thereby adversely affecting the fingerprint sensing.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-described problems of the prior art.

It is another object of the present invention to provide a fingerprint sensor that monitors the degree to which a drive signal applied to a finger during fingerprint detection is attenuated as the voltage is distributed between the finger and the metal case and measures the magnitude of the Tara drive signal or the output signal size from the sensor pad So that normal fingerprint detection can be performed.

According to an aspect of the present invention, there is provided an electronic device including: an external electrode to which a drive signal is applied to a finger; A sensor array including a plurality of sensor pads for outputting a response signal in response to application of the driving signal, the sensor array being disposed adjacent to the external electrodes; A driving signal supplier including a buffer for outputting the driving signal according to a predetermined gain corresponding to an input signal; And a compensator for compensating for attenuation of the drive signal by voltage division into the finger and the metal case based on the magnitude of the drive signal outputted from the drive signal supply unit and applied to the finger / RTI >

Wherein the buffer outputs the driving signal between a power supply voltage and a ground potential, the compensating unit compares the magnitude of the driving signal with at least one reference value, and adjusts the power supply voltage of the buffer based on the comparison result The buffer power supply voltage control value can be determined.

The compensating unit may compare the magnitude of the driving signal with at least one reference value and determine a buffer gain control value for adjusting the gain of the buffer based on the comparison result.

The compensation unit may compare a magnitude of the driving signal with at least one reference value and determine a sensing voltage control value for compensating a sensing voltage output from the sensor pad based on the comparison result.

The fingerprint detection device may further include a signal processing unit for processing the output signal from the sensing circuit and the sensing circuit connected to each of the sensor pads, and the compensating unit may apply the determined sensing voltage control value to the sensing circuit or the signal processing unit can do.

The sensing voltage control value may be applied to a Programmable Gain Amplifier (PGA) or an Analog-to-Digital Converter (ADC) in the signal processing unit.

The compensation unit may perform the compensation by comparing the magnitude of the drive signal with a predetermined ideal value.

According to another aspect of the present invention, there is provided a method of operating a fingerprint detection device including a plurality of sensor pads for outputting a response signal from a finger in response to application of a driving signal, Causing the buffer to output a driving signal according to a predetermined gain; Measuring a size of a driving signal outputted from the buffer and applied to the finger; And determining a control value for compensating for attenuation of the drive signal by voltage division between the finger and the metal case, in accordance with the measurement result.

According to an embodiment of the present invention, since the actual voltage of the driving signal applied to the finger is monitored, the degree of attenuation due to the voltage distribution between the metal case and the finger can be monitored in real time. Accordingly, since the magnitude of the driving signal is controlled or the magnitude of the output signal from the sensor pad is controlled, the influence of the driving signal attenuation can be effectively compensated. As a result, a normal fingerprint image can be generated without being influenced by the drive signal attenuation.

It should be understood that the effects of the present invention are not limited to the above effects and include all effects that can be deduced from the detailed description of the present invention or the configuration of the invention described in the claims.

1 is a view showing a schematic configuration of an electronic apparatus according to an embodiment of the present invention.
2 is a view schematically showing a configuration of a fingerprint detecting apparatus according to an embodiment of the present invention.
FIG. 3 is a diagram showing a configuration of a fingerprint detecting apparatus according to an embodiment of the present invention.
4 is a waveform diagram of a driving signal according to an embodiment of the present invention.
5 is a diagram illustrating a configuration of a comparison unit of a fingerprint detection apparatus according to an embodiment of the present invention.
6 is a view for explaining operations of a comparison unit of a fingerprint detection apparatus according to an embodiment of the present invention.
7 is a diagram showing the configuration of a fingerprint detection apparatus according to another embodiment of the present invention.
8 is a waveform diagram for explaining a result of controlling a driving signal according to another embodiment of the present invention.
9 is a flowchart illustrating a method of compensating a driving signal attenuation in a fingerprint detecting apparatus according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout the specification, when a part is referred to as being "connected" to another part, it includes not only "directly connected" but also "indirectly connected" . Also, when an element is referred to as "comprising ", it means that it can include other elements, not excluding other elements unless specifically stated otherwise.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a view showing a schematic configuration of an electronic apparatus according to an embodiment of the present invention.

Referring to FIG. 1, the electronic device may include a fingerprint detection device 100 at least in part. Although the fingerprint detection device 100 is illustrated as being formed on one edge of the electronic device, the fingerprint detection device 100 may be formed at any position without departing from the scope of the present invention.

The electronic device according to an embodiment of the present invention may be a digital device that performs predetermined data processing to perform a desired operation by the user. The electronic device may include an input unit and a display unit 300 and may provide a status of an operation performed by a user's predetermined operation command through the input unit to the user through the display unit 300. [ In addition, the electronic apparatus may include a cover glass 500 that protects the display unit 300 and forms a front surface of the electronic apparatus.

1, the display unit 300 of the electronic device is implemented by a touch screen method and functions as an input unit itself. However, the input unit may be implemented by a keyboard or a keypad, for example, .

An electronic apparatus according to an embodiment of the present invention includes a memory unit and a microprocessor for loading a digital signal such as a tablet PC, a smart phone, a personal computer, a workstation, a PDA, a web pad, a mobile phone, It should be understood as a term covering equipment.

The fingerprint detecting apparatus 100 according to an embodiment of the present invention can be implemented by an area method in which a fingerprint is read when a finger is placed on the sensor. However, the fingerprint detection apparatus 100 according to the embodiment of the present invention is not limited thereto and can be implemented as a slide type. The slide type fingerprint detection apparatus 100 reads a fingerprint image of a finger moving in a sliding manner to read a fragmentary fingerprint image and then integrates the fingerprint image into a single image to implement a complete fingerprint image. .

The fingerprint detection device 100 includes a sensor array 110 and external electrodes 130, which are composed of a plurality of fingerprint sensor elements. The external electrode 130 is provided separately from the sensor array 110. The external electrode 130 functions to transmit a driving signal for fingerprint detection to a subject (finger).

1, the external electrodes 130 are formed in the form of a ring surrounding the sensor array 110. However, the external electrodes 130 may be formed to surround only a part of the sensor array 110 have. It is also possible to form the sensor array 110 apart from the sensor array 110 in the form of a frame and to have a predetermined shape (for example, a reversed "U" Shape). The external electrode 130 according to the embodiment of the present invention is not limited to a specific form.

The external electrode 130 is formed of a conductive metal to transmit the driving signal to the subject, and the fingerprint detection device 100 is mounted on the electronic device in a module form together with the external electrode.

In fingerprint sensing, a response signal from a finger is applied when a driving signal is applied. When a driving signal is applied only to a finger to be sensed, each sensing pad can output an accurate sensing signal. However, in actual fingerprint recognition, the user grasps the terminal with one hand and recognizes the fingerprint with the other hand. Therefore, the driving signal is distributed from the finger to be recognized through the metal packing portion of the terminal in contact with the hand holding the terminal . In other words, the drive signal is distributed to the metal case of the finger and the terminal to be sensed and attenuated.

One method for compensating for this is to arrange a monitoring pad in the sensor pad area of the sensor array of the fingerprint detection device 100 and to compensate the output voltage of the sensor pad through the output signal size from the monitoring pad.

Specifically, the magnitude of the output signal from the monitoring pad, which is isolated from the sensor pad or isolated from the sensor pad and spaced apart from the sensor pad, is measured, and the control value is determined according to the measured value. It can be used to compensate.

In the present invention, the driving signal supplied to the external electrode 130 is compared with a reference value, and if the driving signal is less than a predetermined value, the operation is compensated. If a plurality of external electrodes 130 are provided, a driving signal supplied to at least one external electrode 130 is compared with a reference value. Hereinafter, this will be described.

2 is a circuit diagram showing a configuration of a fingerprint detecting apparatus according to an embodiment of the present invention.

Referring to FIG. 2, the fingerprint detection device 100 includes an external electrode 130 provided on an external chip, and a sensor array 110 including a plurality of sensor pads. Each sensor pad is connected to a sensing circuit. When the finger contacts the fingerprint detecting device 100, the sensing result based on the finger surface is output. This will be described later in detail.

The size of the driving signal Vdrv output from the driving signal supplying unit 210 and the driving signal supplying unit 210 is measured in the chip internal of the fingerprint detecting device 100 and applied to the circuit according to the measured value And a compensation unit 220 for determining a gain control value. The compensating unit 220 compensates for the attenuation based on the magnitude of the driving signal Vdrv. The compensation unit 220 may be included in the control logic of the chip according to an embodiment, but the scope of the present invention is not limited thereto. In addition, the chip may further include a sensing circuit for processing a signal output from the sensor array 110, which will be described later in more detail.

As described above, the driving signal Vdrv applied through the external electrode 130 is input to the sensor pad through the object. The driving signal Vdrv may be supplied through the driving signal supply unit 210.

The driving signal supply unit 210 may include one or more power supply buffers 211. The buffer 211 receives the enable signal ENB and outputs the driving signal Vdrv through the first terminal A so that the driving signal Vdrv is not affected by the circuit or the environment.

The buffer 211 outputs the driving signal Vdrv according to a predetermined gain corresponding to the input signal VdrvIN between the power supply voltage VDD supplied from the mobile device and the ground potential.

The compensating unit 220 includes a comparator 221 for comparing the magnitude of the driving signal Vdrv output from the first terminal A with one or more reference values, And a control value determiner 222 for determining a control value for the gain. The drive signal Vdrv from the first terminal A is input to the comparator 221 through the second terminal B and the output signal from the control value determiner 222 is input to the third terminal C And is utilized as a gain control value for a part of the circuit.

The first terminal A connected to the buffer 211 and the second terminal B connected to the comparator 221 are connected to each other through an intermediate node TxOUT IN. The intermediate node TxOUT IN is a node formed outside the chip and is a node for measuring the actual driving signal applied to the finger in consideration of the voltage distribution between the metal case and the finger. The operation of the comparator 221 and the control value determiner 222 of the compensator 220 will be described later in detail.

FIG. 3 is a diagram illustrating a configuration of a fingerprint detection apparatus according to an embodiment of the present invention.

Referring to FIG. 3, the fingerprint detection apparatus includes a sensor array 110 including a plurality of fingerprint sensor elements 111 forming a plurality of rows and columns. Each of the fingerprint sensor elements 111 includes a sensor pad SP and a sensing circuit SC into which an output signal from the sensor pad SP is input. Although only one sensing circuit SC is shown in FIG. 3, one sensing circuit SC is provided for each fingerprint sensor element 111. FIG. The sensing circuit SC may include an operational amplifier for amplifying an output signal from each sensor pad SP.

The output signals from the plurality of sensing circuits SP are input to the signal processing unit 140.

The signal processing unit 140 includes a filter unit 141, a sample and hold unit 142, a Related Data Calibration (RDC) 143, a Programmable Gain Amplifier 144, a DSG (Differential Signal Generator) And an analog-to-digital converter (ADC) 146.

The filter unit 141 functions to remove noise of output data from the fingerprint sensor element 111. [ The fingerprint image is obtained by analyzing the data output from the plurality of fingerprint sensor elements 111. The output data of the fingerprint sensor element 111 must contain a data component due to external noise or the like. Therefore, the filter unit 141 includes a low-pass filter or the like to remove such noise.

The sample and hold unit 142 functions to sample the noise-removed data by the filter unit 141, to hold the sampled data, and to store the sampled value. The sampling period of the sample and hold section 142 is controlled by a predetermined clock signal.

The RDC 143 controls the offset of the output data of the sample and hold unit 142, that is, the output data from the fingerprint sensor element 111 sampled at regular intervals after the influence of the noise is removed.

The PGA 144 functions to amplify the sensing data at a predetermined ratio. Since the fingerprint of a person's finger is composed of ridges and valleys, different output data are generated depending on whether the fingerprint sensor element 111 is ridged or tangled. In other words, output data of different sizes are generated when the ridge touches the fingerprint sensor element 111 and when the finger touches the fingerprint. In order to increase the size difference, the gain of the PGA 144 is increased, The gain of the PGA 144 can be controlled to be lowered.

The ADC 146 functions to digitize the sensing data of the analog form. The data converted into the digital form is input to the input / output unit 150.

The data input to the input / output unit 150 is output as the entire data format of the sensor array 110, and the value output from the input / output unit 150 is output to a host device (for example, a mobile device or a specific intelligent device Or a specific application), and the fingerprint image can be generated through the collection.

The sensing circuit SC, the signal processing unit 140, and the input / output unit 150 are provided in the chip internal area in FIG.

The driving signal supply unit 210 according to one embodiment includes the buffer 211 that outputs the driving signal Vdrv through the first terminal A as described above. The driving signal supply unit 210 may include a power supply unit 212 for supplying the power supply voltage VDD to the buffer 211. [

The compensation unit 220 according to an embodiment further includes a compensation unit 220 that compares the magnitude of the driving signal Vdrv applied to the external electrode 130 with a reference value and controls a gain of a part of the circuit.

The compensation unit 220 includes a comparator 221 for comparing the magnitude of the driving signal Vdrv output from the first terminal A connected to the buffer 211 and the external electrode 130 to one or more reference values, A control value determiner 222 for determining the control value of the gain to be applied to a part of the circuit, that is, the degree of compensation and determining the control value for applying the degree of compensation, according to the comparison result of the comparator 221 .

The comparator 221 may be implemented by a conventional analog circuit capable of comparing the magnitude of the driving signal Vdrv with one or more reference values. As an example, the comparator 221 may include a comparator that selectively varies the reference voltage by a voltage divider and compares the reference voltage with the driving signal (Vdrv), which will be described in detail later. The reference value may be a predetermined ideal value, for example, an output voltage value of the sensor pad measured when a human's finger touches the sensor pad SP before the fingerprint detection device is metallized, It does not.

The control value determination unit 222 may determine a sensing voltage control value for amplifying and compensating the output signal from the sensor pad SP, that is, the sensing voltage, based on the output value of the comparison unit 221. [ For example, the control value determination unit 222 may previously match and store sensing voltage control values corresponding to the output values output from the comparison unit 221, and may store the sensing voltage control values based on the output value of the comparison unit 221 The sensing voltage control value can be utilized to amplify the sensing voltage output from the sensor pad SP.

In one embodiment, the control value determination unit 222 may apply the determined sensing voltage control value to the sensing circuit SC connected to the sensor pad SP (CON1). Specifically, the gain of the operational amplifier included in the sensing circuit SC and amplifying the output signal from the sensor pad SP can be controlled to be controlled.

In another embodiment, the control value determination unit 222 may reflect the determined sensing voltage control value to the PGA 144 included in the signal processing unit 140 (CON2). The PGA 144 is a component that allows the amplifier or amplification factor to be selected as needed through a programmatic approach. Since the PGA 144 functions to amplify the output signals of the sensing circuit SC, when the determined sensing voltage control value is applied to the PGA 144, the output signal from the sensor pad SP, which contacts the ridge of the finger, And the output signal from the sensor pad (SP) touching the valley.

In another embodiment, the control value determination unit 222 may reflect the determined sensing voltage control value to the gain at the time of conversion from the ADC 146 to the digital signal (CON3).

That is, the control value determining unit 222 may apply the determined sensing voltage control value to at least one of the sensing circuit SC, the PGA 144, and the ADC 146. [

The control value determination unit 222 may be implemented by a program module or firmware that performs a predetermined algorithm.

Hereinafter, the attenuation of the driving signal applied to the external electrode 130 and the compensation thereof will be described in detail.

4 is a graph showing a waveform of a driving signal according to an embodiment. The graph shown at the top of FIG. 4 shows the drive signal waveform in the ideal case, and the graph at the bottom shows the waveform of the actual drive signal.

Referring to FIG. 4, in an ideal case, the driving signal Vdrv applied to the external electrode 130 may be a square wave signal. That is, the duty ratio may be constant, and the high signal Vdrv_H and the low signal Vdrv_L may be output alternately.

However, in the actual case, the maximum value magnitude of the driving signal Vdrv may be attenuated by a certain portion Vloss due to the operation of the buffer 211 or the surrounding environment. When the size of the driving signal Vdrv is attenuated, the size of the signal output from the fingerprint sensor element is reduced, which may adversely affect fingerprint image generation.

Therefore, when the magnitude of the driving signal Vdrv output from the actual buffer 211 and applied to the external electrode 130 is compared with the reference value, the degree of attenuation of the current driving signal Vdrv can be measured Based on which the gain for amplifying the output voltage from the sensor pad can be determined. 5 is a diagram illustrating an example of a comparison unit according to an embodiment of the present invention.

As described above, the comparator 211 includes a comparator com which compares the driving signal Vdrv with one or more reference values.

The first input terminal of the comparator com receives the driving signal Vdrv, and the second input terminal receives one or more reference voltages. The comparator com outputs a value corresponding to the comparison result between the driving signal Vdrv and the reference voltage as the output value Vout.

The driving signal Vdrv can be converted and input by a predetermined resistor Rx. The resistor Rx may have a predetermined resistance value or may be a variable resistor. The resistance Rx may be omitted, or it may be a parasitic resistance value generated by the circuit design. When the resistor Rx is omitted, the driving signal Vdrv is directly input to the comparator com.

A plurality of output nodes of the voltage divider VD may be alternately connected to the second input terminal of the comparator com. The voltage divider VD may include a plurality of resistors connected in series between the power supply voltage VDD and the ground potential.

The power supply voltage VDD may be supplied to a plurality of resistors to be distributed to one or more reference voltages. As the power supply voltage VDD, the power supply voltage of the elements mounted inside the fingerprint detection device can be used as it is, or it can be used as a voltage converted by level shifting or the like.

One or more reference voltages distributed by a plurality of resistors are alternately input to the second input terminal of the comparator com. The number of reference voltages can be varied depending on how many bits of the output value of the comparator com are divided into signals. When the number of reference voltages is N, the output value of the comparator com may be log2N bits. For example, when the reference voltage of the comparator com is four, a 2-bit signal such as '00', '01', '10', or '11' is output as an output value of the comparator 210.

For example, as shown in FIG. 6, in order to detect the magnitude of the driving signal Vdrv by dividing into four levels, the number of reference voltages, that is, the N value should be 4. At this time, Is output in 2 bits. If the driving signal Vdrv is larger than the reference voltage VT [2], the most significant bit value of the output value of 2 bits becomes '1', and if it is smaller than the reference value, the most significant bit value becomes '0'. If the voltage Vdetect from the monitoring pad 120 is greater than the reference voltage VT [2] and greater than the reference voltage VT [3] (VT [3]> VT [2]), And the final output value Vout of the comparator 210 becomes '11'. Conversely, if it is larger than the reference voltage VT [2] but smaller than the reference voltage VT [3], the final output value Vout of the comparator 210 becomes '10'.

The distribution interval between the reference voltages may be set constant between the maximum value and the minimum value of the driving signal Vdrv. However, since the purpose is to indirectly measure the damping value (Vloss) due to environmental factors, For example, in the ideal case, the closer the reference voltage Vdrv_H (see FIG. 4) to the maximum value of the driving signal Vdrv, the more compact the reference voltage distribution interval. However, the present invention is not limited thereto, and it is possible to appropriately select the values of the resistors included in the voltage divider VD to produce a desired reference voltage.

Although FIG. 5 illustrates an embodiment including only one comparator com, it is needless to say that the present invention can be implemented by a plurality of comparators com depending on the number of reference voltages.

The control value determination unit 222 may determine a sensing voltage control value for compensating the output voltage of the sensor pad SP based on the output value Vout of the comparison unit 221. [ The sensing voltage control value for compensating the output voltage of the sensor pad SP can be determined based on the magnitude of the driving signal Vdrv obtained through the output value Vout of the comparator 221. [

In one embodiment, the control value determining unit 222 may previously store a matching voltage value or a sensing voltage control value to be applied for each binary signal according to an output value of the comparing unit 221 in one embodiment. Alternatively, the control value determining unit 222 may store a matching voltage value or a sensing voltage control value to be applied for each binary signal according to the output value of the comparing unit 221 in advance.

7 is a view for explaining the configuration and operation of a fingerprint detecting apparatus according to another embodiment of the present invention.

Referring to FIG. 7, it can be seen that the configuration or operation of the driving signal supplying unit 710 and the compensating unit 720 in the fingerprint detecting apparatus of FIG. 3 are changed.

In the driving signal supply unit 710 according to another embodiment of the present invention, the gain of the buffer 711 that outputs the driving signal Vdrv may be varied. Further, in the driving signal supply unit 710 according to another embodiment of the present invention, the magnitude of the power supply voltage VDD supplied thereto is variable.

The compensator 720 according to another embodiment of the present invention includes a comparator 721 for comparing the driving signal Vdrv applied to the external electrode 130 with one or more reference values, A control value determiner 722 for determining a buffer power supply voltage control value for controlling the magnitude of the power supply voltage VDD to be supplied to the buffer 711 or a buffer gain control value for controlling the gain of the buffer 711, . 2, the output of the control value determining unit 722 may be connected to a buffer power supply voltage control value or a buffer 711 by signal lines separately connected in the chip. 7, the output of the control value determiner 722 is connected to an AP (Application Processor) of the host apparatus, and the AP receives the output of the buffer power source 722 based on the output of the control value determiner 722, The voltage control value or the control signal to the buffer 711, respectively.

More specifically, the comparator 721 compares the magnitude of the drive signal Vdrv applied to the external electrode 130, that is, the magnitude of the output signal of the buffer 711 with one or more reference values. The detailed configuration of the comparison unit 721 is the same as that described with reference to Fig.

The comparison result by the comparator 721 is input to the control value determiner 722. [ The control value determiner 722 generates a buffer gain control value for controlling the gain of the buffer 711 and applies the buffer gain control value to the buffer 711 (CON4) or controls the buffer 711 And generates a buffer power supply voltage control value for controlling the magnitude of the power supply voltage VDD of the power supply unit 712 (CON 5). 7 shows an example in which the gain of the buffer 711 is adjusted to M times by this control and an example in which the power supply voltage supplied to the buffer 711 in the power supply unit 712 is adjusted to N times. The power supply voltage regulating circuit in the power supply unit 712 can be realized through a normal voltage converting circuit. For example, a charge pump circuit, which charges a predetermined electrostatic capacity and outputs a boosted voltage by adding a voltage due to the charged electric charge and an input voltage, or a mutual inductance between inductors, A transformer for boosting the voltage, and the like.

For example, the control value determiner 722 generates a buffer gain control value for determining the gain of the buffer 711 based on the output signal from the comparator 721, and outputs the buffer gain control value to the buffer 711 directly or indirectly To be applied (CON4). The gain of the buffer 711 may be adjusted in a conventional manner, such as by adjusting the magnitude of the feedback impedance.

Alternatively, the control value determiner 722 may generate a buffer power supply voltage control value for controlling the magnitude of the power supply voltage VDD of the buffer 711 and supply the buffer power supply voltage control value to the power supply unit 712 (CON5). The power supply unit 712 receiving the buffer power supply voltage control value can increase the magnitude of the power supply voltage VDD supplied to the buffer 711, for example, N times. To this end, the power supply unit 712 may be provided with an amplifying circuit for increasing the voltage VDD by N times. Where N and M may be integers greater than zero.

The control value determination unit 722 may store the type or the size of the control value to be generated or transferred according to the output signal from the comparison unit 712 for the above operation.

8 is a waveform diagram showing a result of amplification of a driving signal in the embodiment described with reference to FIG.

Referring to FIG. 8, the driving signal Vdrv may be a square wave signal alternately outputting a high signal Vdrv_H and a low signal Vdrv_L having a constant magnitude in an ideal case.

If the magnitude of the driving signal Vdrv is attenuated by Vloss by the parasitic component present in the circuit, this phenomenon can be detected through the comparator 721. That is, the comparator 721 senses that the magnitude of the driving signal Vdrv is a magnitude that is attenuated by Vloss, and in response to the detection, the control value determiner 722 determines the gain of the buffer 711 (CON4), and generates a buffer power supply voltage control value for controlling the size of the power supply voltage VDD of the buffer 711 and transmits the buffer power supply voltage control value to the power supply unit 712 5).

According to this control, the driving signal Vdrv output through the driving signal supply unit 710 is raised to a certain extent.

For example, as shown in Fig. 8, the minimum value (Vdrv-Vloss) of the high signal of the driving signal (Vdrv) can be controlled to be equal to the value of the high signal (Vdrv_H) in the ideal case.

Although the embodiment of FIG. 3 and the embodiment of FIG. 7 are separately described above, the two embodiments may be combined with each other.

For example, the gain of the buffer may be adjusted according to the output signal from the comparator, and the gain of the sensing circuit, PGA, or ADC that processes the output signal of the sensor pad may be adjusted. Also, in the above example, the power supply voltage of the buffer may be controlled instead of controlling the gain of the buffer, and all of the gain control described above may be simultaneously performed.

It goes without saying that at least two of the control methods (CON1 to CON5) described in the above embodiments may be performed simultaneously.

9 is a flowchart illustrating a method of compensating a driving signal attenuation in a fingerprint detecting apparatus according to an embodiment of the present invention.

Hereinafter, a driving signal attenuation compensation method will be described with reference to FIGS. 3, 7, and 9. FIG.

First, the driving signal Vdrv supplied to the external electrode 130 disposed adjacent to the sensor array 110 including the plurality of sensor pads SP is extracted (S910).

The magnitude of the drive signal Vdrv currently supplied to the external electrode 130 is determined by comparing the extracted drive signal Vdrv with one or more reference values (S920). This comparison may be performed by comparing the drive signal Vdrv with at least one reference value output from the voltage divider VD (see FIG. 5) by the comparators 221 and 721.

After determining the magnitude of the driving signal Vdrv, the control object is determined based on the magnitude of the driving signal Vdrv and the control value to be applied is determined (S930). This determination is made by the control value determination unit 222 or 722, and information on the compensation method for the magnitude of the measured driving signal Vdrv may be stored in advance.

When the control value is determined in this manner, the control value determination unit 222 or 722 controls the drive signal supply unit 710 to increase the size of the drive signal Vdrv or to increase the size of the sensor pad SP, To be compensated for (S940).

The control for the driving signal supply unit 710 generates a buffer gain control value for controlling the gain of the buffer 711 that outputs the driving signal Vdrv in operation S941, The buffer power supply voltage control value may be generated to control the power supply unit 712 (S942).

On the other hand, a method of compensating the output signal from the sensor pad SP is to apply a sensing voltage control value determined as a result of the comparison to the operational amplifier of the sensing circuit SC receiving the output signal from the sensor pad SP S943), the determined sensing voltage control value may be applied to the PGA 144 amplifying the output signal of the entire sensor array 110 (S944). Also, the sensing voltage control value may be applied to the digital conversion of the ADC 146 that converts the output signal of the entire sensor array 110 into a digital signal (S945).

According to the present invention, the magnitude of the driving signal applied to the external electrode is measured, the magnitude of the driving signal is amplified according to the degree of attenuation, or the gain of a part of the circuit for processing the signal output from the sensor pad is controlled , The size of a signal necessary for generating a fingerprint image can be appropriately maintained.

Further, according to the present invention, since the compensation operation is performed based on the magnitude of attenuation from the driving signal itself initially supplied to the fingerprint detecting device, direct control according to the degree of the driving signal attenuation is possible. Accordingly, the problem that the fingerprint image which is sensed in response to the attenuated driving signal is dispersed to the metal case other than the finger is radically solved.

Meanwhile, according to the present invention, the attenuation of the driving signal can be compensated in various ways in accordance with the convenience of circuit design.

It will be understood by those skilled in the art that the foregoing description of the present invention is for illustrative purposes only and that those of ordinary skill in the art can readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

100: fingerprint detection device
300:
500: Cover glass
110: sensor array
111: fingerprint sensor element
130: external electrode
140: Signal processor
141:
142: Sample and hold section
143: RDC
144: PGA
145: DSG
146: ADC
150: Input /
210, 710: driving signal supply unit
211, 711: buffer
212, 712: Power supply
220:
221, 721:
222: Control value determination unit
722: Control value determination unit

Claims (8)

A driving electrode for applying a driving signal with a finger;
A sensor array including a plurality of sensor pads for outputting a response signal in response to application of the driving signal, the sensor array being disposed adjacent to the driving electrode;
A driving signal supplier including a buffer for outputting the driving signal according to a predetermined gain corresponding to an input signal; And
A control signal for amplifying the drive signal or an output signal from the plurality of sensor pads according to a magnitude of a drive signal applied to the drive electrode from the drive signal supply unit, And a compensation unit for compensating for attenuation of the drive signal by the distribution. The method according to claim 1,
The buffer outputs the drive signal between a power supply voltage and a ground potential,
Wherein the compensating unit compares the magnitude of the driving signal with at least one reference value and determines a buffer power supply voltage control value for adjusting the power supply voltage of the buffer based on the comparison result. The method according to claim 1,
Wherein the compensation unit comprises:
And compares the magnitude of the drive signal with at least one reference value and determines a buffer gain control value for adjusting the gain of the buffer based on the comparison result. The method according to claim 1,
Wherein the compensation unit comprises:
And compares the magnitude of the drive signal with at least one reference value and determines a sensing voltage control value for compensating a sensing voltage output from the sensor pad based on the comparison result. 5. The method of claim 4,
Further comprising a sensing circuit coupled to each of the sensor pads and a signal processor for processing an output signal from the sensing circuit,
Wherein the compensation unit applies the determined sensing voltage control value to the sensing circuit or the signal processing unit. 6. The method of claim 5,
The sensing voltage control value is a value
And is applied to a PGA (Programmable Gain Amplifier) or an ADC (Analog to Digital Converter) in the signal processing unit. The method according to claim 1,
Wherein the compensation unit comprises:
And compares the magnitude of the drive signal with a predetermined ideal value to perform the compensation. And a plurality of sensor pads for outputting a response signal from a finger in response to application of a driving signal through the driving electrode,
Supplying an enable signal and a predetermined input signal to the buffer so that the buffer outputs the drive signal according to a predetermined gain;
Measuring a magnitude of a driving signal output from the buffer and applied to the driving electrode; And
According to the measurement result, a control value for amplifying the drive signal or the output signal from the plurality of sensor pads is output to compensate the attenuation of the drive signal by voltage distribution to the finger and the metal case Determining a control value to be used for the fingerprint detection device.

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