KR101456649B1 - Capacitive Sensor and Method for Elimination of Noise Therefor - Google Patents

Abstract

A capacitive sensor capable of automatically removing a noise component and a noise removing method therefor. The capacitive sensor according to an embodiment of the present invention detects a change in capacitance, And a noise canceller for selecting a valid detection frequency based on the rate of change of each of the plurality of detection frequencies and determining whether to enable the detection signal based on the selected effective detection frequency.

Description

Technical Field [0001] The present invention relates to a capacitive sensor and a noise canceling method for the same,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensing device, and more particularly, to a capacitive sensor and a noise removing method therefor.

The electrostatic capacitance sensor is a sensor that quantifies a physical quantity by utilizing the effect of accumulating electric charge when a potential is applied to a conductor. Such capacitive sensors have various applications such as a touch sensor, a bidet seat sensor, and a water level sensor such as a water purifier.

Generally, the capacitance sensor is configured to compare a change in the sensing frequency, which changes in accordance with a change in capacitance, with a reference frequency, and output a sensing signal when a difference is greater than a predetermined value. Recently, an MFM (Multi-Frequency Modulation) method has been used to detect a capacitance change using a plurality of detection frequencies in order to improve an error due to a charge / discharge delay component of a frequency generator generating a detection frequency.

1 is a configuration diagram of a general capacitance sensor.

1, the electrostatic capacitance sensor 10 includes a capacitance change detecting unit 101, a frequency generating unit 103, a frequency counter 105, a change reference value providing unit 107, a capacitance change calculating unit 109, an output reference value providing unit 111, a comparing unit 113, and an output unit 115.

The frequency generating unit 103 generates a plurality of detection frequencies, for example, and applies the detected frequency to the capacitance change detecting unit 101. [

The detection frequency generated by the frequency generator 103 is applied to the frequency counter 105 through the capacitance change detecting unit 101 or the pad so that the frequency counter 105 counts the number of oscillations per detection frequency.

The capacitance change calculator 109 compares the number of oscillations of each sensing frequency outputted from the change reference value providing unit 107 with the number of oscillations of each sensing frequency counted by the frequency counter 105.

The comparison unit 113 compares the average value of the variation amounts of the respective detection frequencies obtained from the output values of the frequency counter 105 with the reference values provided by the output reference value providing unit 111 to generate an output control signal. Accordingly, the output unit 115 outputs a control signal according to whether the input signal is sensed in response to the output control signal of the comparison unit 113.

In such a capacitance sensor, the capacitance change detection unit 101 includes a capacitor whose capacitance value changes according to whether or not it is in contact. This capacitor is configured to repeatedly perform charging and discharging in accordance with the predetermined maximum voltage VH and the lowest voltage VL, and has a voltage waveform as shown in Fig.

2 is a diagram showing a capacitor voltage waveform in a general capacitance change detecting apparatus.

A constant current is applied to the capacitor whose capacitance value changes according to the contact, and when the voltage of the capacitor reaches the predetermined maximum voltage (VH), the capacitor starts discharging. When the capacitor starts discharging and reaches the predetermined lowest voltage VL, the charging operation is performed until the voltage reaches the maximum voltage VH again.

The frequency generating unit 103 shown in FIG. 1 provides at least one sensing signal corresponding to a capacitance change of the capacitor as shown in FIG. 2 to the capacitance change detecting unit 101, and the frequency counter 105 The number of times of oscillation of the sensing signal is counted for a predetermined period of time to detect a capacitance change of the capacitor. That is, by measuring the charging and discharging time of the capacitor, the capacitance change is detected by using the characteristic that the charging and discharging time is increased when the capacitance is increased and the charging and discharging time is decreased when the capacitance is decreasing.

In this way, noise can be added due to external application environment such as temperature / humidity change, instantaneous static electricity, system power supply noise, and the like when detecting a change in capacitance of the capacitor by such a method. This interference is received, and an error may occur in detecting a change in capacitance.

FIGS. 3 and 4 are diagrams for explaining a change in sensing frequency according to the generation of a touch in a general capacitive sensor, and an example in which the frequency generating unit 103 senses a change in capacitance at n sensing frequencies will be described as an example.

First, FIG. 3A shows the patterns of the detection frequencies f1 to fn in a situation where no touch occurs. FIG. 3B shows the change patterns f1 'to fn' of the sensing frequency f1 to fn when a touch occurs. When the touch occurs, it is found that the detection frequencies f1 to fn are moved to the left (arrow direction) as a whole as shown in FIG. 3B. That is, the detection frequencies f1 to fn have a positive rate of change.

FIG. 4 shows a result obtained by digitizing the frequency change of FIG. 3B. When the rate of change of the detection frequencies f1 to fn is equal to or greater than a preset threshold value TH, the touch is recognized as having occurred.

In this way, when a normal touch occurs, it can be seen that the detection frequencies f1 to fn are shifted in the same direction by a similar rate of change. When the rate of change is equal to or greater than a preset threshold value TH, do.

5A and 5B are diagrams for explaining a change in the detection frequency according to noise.

5A shows patterns of the detection frequencies f1 to fn when no touch or noise is generated and FIG. 5B shows patterns f1 to fn in which the detection frequencies f1 to fn are changed by noise .

In particular, when noise of a frequency component is interfered with by an external environment such as an illumination or a radio, the detection frequencies f1 to fn shift to the frequency side of the noise component.

For example, it is assumed that the frequency of the noise component is a value (fx) between f2 and f3 as shown in Fig. 5B. It can be seen that the detection frequency of the frequency lower than the frequency component fx of the noise component moves to the fx side and the detection frequency of the frequency component higher than the frequency component fx of the noise component moves to the fx side.

That is, a detection frequency lower than fx moves at a rate of change of negative (-), and a detection frequency higher than fx moves at a rate of change of positive (+).

Then, the change rate of the detection frequencies around the fx is very large, but the change rate of the detection frequency components far from the fx will be very small.

However, the current capacitive sensor performs an internal operation for processing a noise component, especially a noise component of a frequency component, as an event and outputting a control signal according to whether the signal is sensed. Accordingly, the capacitive sensor can perform unnecessary operation, and the sensing reliability can not be secured by recognizing the capacitance change due to the noise component as a touch.

The present technology has a technical problem of providing a capacitance sensor capable of automatically removing a noise component and a noise removal method therefor.

The capacitance sensor according to an embodiment of the present invention includes a frequency generator for outputting a plurality of detection frequencies; And a noise eliminator for selecting a valid sensed frequency based on the rate of change of each of the plurality of sensed frequencies through the electrostatic capacity change detecting unit and determining whether to enable the sensed signal based on the selected sensed sensed frequency have.

According to another aspect of the present invention, there is provided a capacitive sensor comprising: a frequency generator for generating a plurality of detection frequencies; A capacitance change detector for detecting a capacitance change in response to the plurality of detection frequencies generated by the frequency generator; A sensing unit for selecting a sensing frequency in which a rate of change of each of the plurality of sensing frequencies is within a specified range, in response to a capacitance change provided by the capacitance change detecting unit, and outputting an enable signal of the sensing signal; And an output control unit responsive to the enable signal of the sensing signal for outputting a control signal according to a comparison result between the rate of change of the effective sensing frequency and the output reference value. . ≪ / RTI >

Meanwhile, a noise removing method for a capacitive sensor according to an embodiment of the present invention includes a sensing unit for outputting an enable signal of a sensing signal based on a rate of change of a plurality of sensing frequencies varying in response to a change in capacitance A noise removing method for a capacitive sensor, comprising: counting a number of oscillations of each of a plurality of sensing frequencies as a capacitance change is detected; Comparing the count result of each of the plurality of detection frequencies with the reference oscillation frequency; And a noise removal process for selecting at least one detection frequency included in the predetermined range based on a rate of change of each of the plurality of detection frequencies and determining whether to enable the detection signal.

In this technology, it is possible to remove noise based on the rate of change of the detection frequency when noise, particularly, noise of frequency components occurs, thereby improving the sensing reliability of the capacitance sensor.

In addition, when it is determined that the event is caused by noise, the following unnecessary operation can be omitted, and the operation efficiency of the capacitance sensor can be improved.

1 is a schematic view of a general capacitance sensor,
2 is a diagram showing a capacitor voltage waveform in a general capacitance change detecting apparatus,
FIGS. 3 and 4 are diagrams for explaining a change in sensing frequency according to a touch generation in a general capacitance sensor,
FIGS. 5A and 5B are diagrams for explaining changes in the detection frequency according to noise;
6 is a configuration diagram of a capacitance sensor according to an embodiment of the present invention;
FIG. 7 is an example of the noise removing unit shown in FIG. 6,
8A and 8B are diagrams for explaining the operation of the alignment unit shown in FIG. 7,
9A and 9B are diagrams for explaining the operation of the filtering unit shown in FIG. 7,
10 and 11 are flowcharts for explaining a noise removing method according to an embodiment of the present invention.

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

6 is a configuration diagram of a capacitance sensor according to an embodiment of the present invention.

6, the capacitance sensor 20 according to an exemplary embodiment of the present invention includes a capacitance change detection unit 210, a sensing unit 220, a frequency generation unit 230, and an output control unit 240 . ≪ / RTI >

The capacitance change detecting unit 210 may be formed of, for example, a pad including a capacitor, and detects a capacitance change of the capacitor.

The frequency generator 230 periodically generates a signal corresponding to a plurality of detection frequencies, for example, and provides the signal to the capacitance change detector 210. In an embodiment of the present invention, the plurality of detection frequencies generated by the frequency generator 230 may be a frequency generated by time-sharing the initial frequency with respect to the capacitance change.

The sensing unit 220 outputs a sensing signal in which the noise component is removed as the capacitance change is detected by the capacitance change detecting unit 210. In particular, the sensing unit 220 according to an embodiment of the present invention may include a frequency counter 222, a capacitance change calculator 224, a noise eliminator 226, and a change reference value provider 228 .

More specifically, the frequency counter 222 counts the number of oscillations per sensing frequency as the sensing frequency is applied through the electrostatic capacitance change detector 101. The capacitance change calculator 224 compares the number of reference oscillations per detection frequency output from the change reference value providing unit 228 with the number of oscillations per detection frequency counted by the frequency counter 222. On the other hand, the noise removing unit 226 removes the detection frequency in which noise components are reflected from the plurality of detection frequencies according to the comparison result calculated by the capacitance change calculating unit 224, that is, And generates the remaining detection frequency as a detection signal and provides it to the output control unit 240.

In general, the change reference value providing unit 228 may obtain the number of times of the initial oscillation at the time when the electric power is applied to the capacitance sensor 20 as a change reference value, or may provide a preset reference value. In this embodiment, the change reference value providing portion 228 preferably provides the number of times of initial oscillation at the time of power application as a change reference value.

The output control unit 240 compares the sensing signal provided from the sensing unit 220 with an output reference value and outputs a control signal according to whether the input signal is sensed. In an embodiment of the present invention, the output controller 240 may include a comparator, an output reference value supplier, and an output unit as shown in FIG. 1, but the present invention is not limited thereto. That is, the output controller 240 compares the average value of the amount of change of the noise components removed by the sensing unit 220 with the output reference value to generate an output control signal, and in response to the output control signal, And outputs the control signal.

Regardless of the configuration of the frequency generator 230 and the output controller 240, in the present invention, even if a change in capacitance is detected in the sensing unit 220, if the cause of the change is due to noise, It is possible to control the frequency counter 230 and the output control unit 240 not to perform unnecessary operations.

5, when the noise of the frequency component occurs, the change rate of the detection frequency around the frequency component of the noise is significant, and as the distance from the frequency component of the noise increases, the change rate of the detection frequency Will smile. In the present invention, it is determined whether or not the detection signal is enabled by selecting only the detection frequency in which the rate of change in frequency among the plurality of detection frequencies is equal, that is, the change rate is within the specified range.

7 is a diagram illustrating an example of the noise removing unit shown in FIG.

7, the noise removing unit 224 includes an aligning unit 310, a filtering unit 320, and a calculating unit 330. [ Optionally, the option setting unit 340 may be further included. However, it is also possible to set the option value to a fixed value through other storage means without employing the option setting unit 340. [

More specifically, the alignment unit 310 aligns the rate of change for each sensing frequency according to the comparison result of the capacitance change calculator 224 as the capacitance change is detected by the capacitance change detector 210. In an embodiment of the present invention, the sorting unit 310 arranges the rate of change of the detection frequency in ascending order, but is not limited thereto.

FIGS. 8A and 8B are diagrams for explaining the frequency alignment process of the noise canceling method according to an embodiment of the present invention.

8A shows the rate of change of the detection frequencies f1 to fn according to the noise components and the detection frequencies f1 and f2 have a rate of change of negative and the other frequencies have a rate of change of positive have.

FIG. 8B shows a state in which the change rates of the detection frequencies f1 to fn shown in FIG. 8 are arranged in ascending order.

As described above, when noise of a frequency component occurs, the detection frequency lower than the frequency of the noise has a rate of change of negative (-), and the detection frequency higher than the frequency of the noise has a rate of change of positive (+). Referring to FIGS. 8A and 8B, it can be deduced that noises of frequency components occur between the detection frequencies f2 and f3. Accordingly, it can be seen that the change rates of the detection frequencies f1, f2, f3, f4, and the like are significant, and the rate of change of the remaining detection frequencies is small.

On the other hand, the filtering unit 320 selects only the detection frequency having the frequency change rate as the effective detection frequency by referring to the sorting result of the sorting unit 310.

For this, the filtering unit 320 removes a first number of detection frequencies designated in descending order of change rate from the alignment result of the alignment unit 310, removes the second number of detection frequencies designated for the remaining detection frequency sequentially .

9A and 9B are views for explaining a frequency filtering process in a noise removing method according to an embodiment of the present invention.

First, FIG. 9A shows a result obtained by removing a first number, for example, three detection frequencies, for an array of detected frequencies as shown in FIG. 8B. The first number may be fixed or variable through the option setting unit 340, but the present invention is not limited thereto.

Meanwhile, FIG. 9B shows a case where a second number, for example, four detection frequencies are sequentially selected after the first number of detection frequencies are removed as shown in FIG. 9A. By selecting the second number of detection frequencies, other frequencies, that is, detection frequencies having a large change rate, are automatically removed. Also, in this case, the criterion for selecting the detection frequency with a constant rate of change, that is, the second number may be fixed or variable through the option setting unit 340, but is not limited thereto.

Referring to FIG. 7 again, the operation unit 330 calculates an average value of the rate of change of the selected sensing frequency when the sensing frequency having a constant rate of change is selected as the effective sensing frequency. Then, the operation unit 330 enables the sensing signal when the calculated average value is higher than the set value. That is, it is determined that a capacitance change has occurred due to the occurrence of a touch, not a noise, so that a sensing signal is outputted, and an operation for outputting a control signal according to whether or not the constituent part of the rear end senses an input signal is performed.

On the other hand, if the calculated average value is equal to or less than the specified set value, the detection signal is disabled and control is performed such that the constituent part at the rear end does not operate. In other words, when the capacitance changes due to noise, the frequency counter 230 and the output control unit 240 are disabled.

Accordingly, unnecessary operations are not performed when the capacitance changes due to an event caused by noise, so that power consumption can be reduced and detection reliability can be improved.

10 and 11 are flowcharts for explaining a noise removing method according to an embodiment of the present invention.

Referring to FIG. 10, the frequency generator 230 generates a plurality of detection frequencies, for example, at predetermined intervals (S10). If a capacitance change is detected by the capacitance change detecting unit 210 in this state (S20), the sensing unit 220 counts the number of oscillations per sensing frequency (S30), and compares the count result with the change reference value (S35).

Then, at step S40, the noise component is removed by selecting at least one detection frequency having a rate of change based on the rate of change of each of the plurality of detection frequencies, that is, within a specified range.

11 is a flowchart for explaining an example of the noise removal process (S40).

In an embodiment of the present invention, the alignment unit 310 of the noise removing unit 224 aligns the detection frequency according to the change rate to remove the noise of the capacitance sensor (S401). In this case, it is preferable to arrange the detection frequencies in ascending order according to the change rate.

The filtering unit 320 performs a first filtering process for deleting the first number of detection frequencies in descending order of the rate of change of the detected detection frequency (S403), and sequentially sets the detection frequency after the deletion (Step S405). In step S405, the second filtering process is performed. In the present embodiment, the second number of detection frequencies are sequentially selected in the second filtering process. However, the second filtering process can be performed by deleting a specified third number of detection frequencies having a high rate of change Of course.

Next, the operation unit 330 averages the rate of change with respect to the finally selected detection frequencies in step S405, and compares the calculated average value with the set value in step S409. If the calculated average value is larger than the set value, the detection signal is enabled (S411). If the average value is less than the set value, the detection signal is disabled (S413).

10, when the sensing signal is enabled (S50), a process of outputting a control signal according to whether the input signal is sensed is performed through the frequency counter 230 and the output control unit 240 S60). The control signal output process S60 may be performed in various manners. For example, it is possible to output the control signal according to whether the input signal is detected by comparing the noise-removed detection frequency with the output reference value, but the present invention is not limited thereto.

As a result, in the present invention, when a capacitance change occurs, it is possible to determine whether the capacitance is detected by using only a detection frequency having a relatively low rate of change or a high detection frequency except for a high detection rate.

Accordingly, when the capacitance changes due to the noise having the frequency component, it can be recognized as noise, thereby preventing unnecessary operation, thereby reducing power consumption and improving the operational reliability of the capacitance sensor. have.

Thus, those skilled in the art will appreciate that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the embodiments described above are to be considered in all respects only as illustrative and not restrictive. The scope of the present invention is defined by the appended claims rather than the detailed description and all changes or modifications derived from the meaning and scope of the claims and their equivalents are to be construed as being included within the scope of the present invention do.

20: Capacitive sensor
210: Capacitance change detector
220:
230: Frequency generator
240:

Claims (14)

A frequency generator for outputting a plurality of detection frequencies; And
And a noise removing unit for selecting a valid detection frequency based on a change rate of each of the plurality of detection frequencies through the capacitance change detection unit and determining whether to enable the detection signal by averaging the change rates of the selected effective detection frequencies ,
Wherein the noise eliminator comprises: an alignment unit for aligning the plurality of detection frequencies according to the rate of change;
A filtering unit for selecting the effective detection frequency from an alignment result of the alignment unit; And
And a calculator for determining whether to enable the sensing signal by averaging the rate of change of the effective sensing frequency selected by the filtering unit. The method according to claim 1,
Wherein the noise removing unit selects, as the effective detection frequency, a detection frequency that includes the change rate within a specified range for each of the plurality of detection frequencies. delete The method according to claim 1,
Wherein the sorting unit arranges the plurality of detection frequencies in ascending order according to the change rate,
Wherein the filtering unit removes a first number of detection frequencies designated in descending order of the rate of change from the results sorted in ascending order and selects a second number of the effective detection frequencies sequentially from the next frequency of the detected frequency, . 5. The method of claim 4,
And an option setting unit for setting the first number and the second number to fixed or variable. A frequency generator for generating a plurality of detection frequencies;
A capacitance change detector for detecting a capacitance change in response to the plurality of detection frequencies generated by the frequency generator;
Wherein the electrostatic capacity change detecting unit selects a sensing frequency in which a rate of change of each of the plurality of sensing frequencies is within a specified range as a valid sensing frequency in response to a change in capacitance provided by the capacitance change detecting unit, A sensing unit for outputting an enable signal of the sensing unit; And
And an output control unit responsive to the enable signal of the sensing signal for outputting a control signal according to a comparison result between the rate of change of the effective sensing frequency and the output reference value,
Wherein the sensing unit comprises: a frequency counter for counting the number of oscillations of each of the plurality of sensing frequencies provided by the capacitance change detecting unit;
A change reference value providing unit for comparing the number of oscillations counted by the frequency counter and the reference oscillation count;
Selecting a valid detection frequency based on the rate of change of each of the plurality of detection frequencies compared in the change reference value providing unit and determining whether to enable the detection signal by averaging a rate of change of the selected effective detection frequency, A filtering unit for selecting the effective detection frequency from the alignment result of the alignment unit; and a controller for averaging the rate of change of the effective detection frequency selected by the filtering unit, A noise eliminator having an arithmetic section for determining whether or not it can be ablated;
. delete The method according to claim 6,
Wherein the noise removing unit selects, as the effective detection frequency, a detection frequency that includes the change rate within a specified range for each of the plurality of detection frequencies. delete The method according to claim 6,
Wherein the sorting unit arranges the plurality of detection frequencies in ascending order according to the change rate,
Wherein the filtering unit removes a first number of detection frequencies designated in descending order of the rate of change from the alignment result of the alignment unit and sequentially selects a second number of effective detection frequencies starting from the next frequency of the detected frequency. And a sensing unit for outputting an enable signal of a sensing signal based on a rate of change of a plurality of sensing frequencies varying in response to a change in capacitance, the method comprising:
Counting the number of oscillations of each of the plurality of sensing frequencies as the sensing unit detects a change in capacitance;
Comparing the number of oscillation counts of each of the plurality of detection frequencies with the reference oscillation number; And
Selecting at least one detection frequency in which the rate of change is within a specified range as a valid detection frequency based on a rate of change of each of the plurality of detection frequencies and averaging the rate of change of the selected effective frequency to check whether the detection signal is enabled And a noise removal process for determining a noise reduction process,
The noise removal process may include: sorting the detection frequency according to the change rate;
Deleting a first number of detection frequencies in descending order of the change rate of the detection frequency;
Selecting an effective detection frequency by sequentially selecting a second number of detection frequencies remaining after the deletion; And
And determining whether to enable the sensing signal by comparing the average value of the rate of change with respect to the valid detection frequencies selected in the valid detection frequency selection step. delete 12. The method of claim 11,
And arranging the detection frequencies in ascending order according to the change rate. 12. The method of claim 11,
Further comprising the step of outputting a control signal depending on whether the capacitance sensor senses an input signal as the sensing signal is enabled after the noise removal process.

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