JP6822029B2 - Capacitance sensor - Google Patents

Description

The present invention relates to a capacitance sensor that detects the presence or absence of an object.

The technique described in Patent Document 1 is known as a capacitance sensor for detecting an object.
The capacitance sensor described in Patent Document 1 includes a capacitor to be measured whose capacitance changes depending on the presence or absence of an object, a reference capacitor having a reference capacitance, a switch arranged between the capacitor to be measured and the reference capacitor, and a capacitor to be measured. It is provided with a comparator for comparing the potential between the measurement capacitor and the reference capacitor and the reference potential, a counting means, and a determining means. The switch repeats on and off. The counting means counts the number of times the switch is operated. The determination means determines the capacitance change of the capacitor to be measured based on the number of operation of the switch until the potential between the capacitor to be measured and the reference capacitor changes from the initial potential to the set potential. The capacitance change determination result can be used to determine the presence or absence of an object placed near the capacitance sensor.

Japanese Unexamined Patent Publication No. 2005-106665

By the way, since the capacitance sensor determines the change in capacitance of the capacitor to be measured based on the number of times the switch is operated, the detection accuracy is limited only by the conventional configuration.

(1) The capacitance sensor that solves the above problems initializes the first capacitor, the second capacitor that is connected to the first capacitor and whose capacitance changes depending on the presence or absence of an object, and the first capacitor. The first switch, the second switch arranged between the first capacitor and the second capacitor, the third switch for initializing the second capacitor, the first switch, the second switch, and the like. The control circuit includes a control circuit for controlling the third switch, and the control circuit comprises an operation of the second switch and an operation of the third switch after the initialization of the first capacitor by the operation of the first switch. Switching control in which the switch operation is performed a plurality of times, and an intermediate potential which is a potential between the first capacitor and the second capacitor is acquired at a plurality of time points for each switch operation, and is based on the plurality of the intermediate potentials. A capacitance sensor that executes an operation to derive the number of detections corresponding to the number of operations of the switch when the intermediate potential exceeds the reference potential, and the control circuit is the switch in the operation. For each operation, a comparison operation for comparing the intermediate potential and the reference potential at a plurality of time points and an index derivation operation for deriving the number of detections based on the plurality of comparison results obtained by the comparison operation are executed. In the index derivation calculation, the control circuit calculates the probability that the intermediate potential exceeds the reference potential based on the plurality of comparison results, and when the probability exceeds the specified probability, the probability is calculated. The number of operations of the switch operation at the time when the specified probability is exceeded is defined as the number of detections .

The number of operation operations, that is, the number of detections of the switch operation when the intermediate potential exceeds the reference potential is an index indicating the capacity of the second capacitor. On the other hand, if there is noise in the intermediate potential, the accuracy of the index will decrease. In the above configuration, the number of detections is derived based on the intermediate potentials acquired at a plurality of time points. Therefore, the accuracy of the number of detections (the accuracy of the index indicating the capacity of the second capacitor) is higher than that in the case of deriving the number of detections based on a single intermediate potential. As a result, the detection accuracy of the capacitance sensor is improved.

According to the above configuration, the number of detections is derived based on a plurality of comparison results obtained for each switch operation. Therefore, the accuracy of the number of detections is higher than that in the case of deriving the number of detections based on a single comparison result obtained for each switch operation.

According to the above configuration, the number of detections is derived based on the above probability.

( 2 ) The capacitance sensor that solves the above problems initializes the first capacitor, the second capacitor that is connected to the first capacitor and whose capacitance changes depending on the presence or absence of an object, and the first capacitor. The first switch, the second switch arranged between the first capacitor and the second capacitor, the third switch for initializing the second capacitor, the first switch, the second switch, and the like. The control circuit includes a control circuit for controlling the third switch, and the control circuit comprises an operation of the second switch and an operation of the third switch after the initialization of the first capacitor by the operation of the first switch. Switching control in which the switch operation is performed a plurality of times, and an intermediate potential which is a potential between the first capacitor and the second capacitor is acquired at a plurality of time points for each switch operation, and is based on the plurality of the intermediate potentials. A capacitance sensor that executes an operation to derive the number of detections corresponding to the number of operations of the switch when the intermediate potential exceeds the reference potential, and the control circuit is the switch in the operation. For each operation, a comparison operation for comparing the intermediate potential and the reference potential at a plurality of time points and an index derivation operation for deriving the number of detections based on the plurality of comparison results obtained by the comparison operation are executed. In the index derivation calculation, the control circuit derives the probability that the intermediate potential exceeds the reference potential based on the plurality of comparison results, and the period before the intermediate potential exceeds the reference potential. The number of detections is derived based on a function that associates the plurality of probabilities obtained at different time points in the above with the number of operations of the plurality of switch operations.
The number of operation operations, that is, the number of detections of the switch operation when the intermediate potential exceeds the reference potential is an index indicating the capacity of the second capacitor. On the other hand, if there is noise in the intermediate potential, the accuracy of the index will decrease. In the above configuration, the number of detections is derived based on the intermediate potentials acquired at a plurality of time points. Therefore, the accuracy of the number of detections (the accuracy of the index indicating the capacity of the second capacitor) is higher than that in the case of deriving the number of detections based on a single intermediate potential. As a result, the detection accuracy of the capacitance sensor is improved.
According to the above configuration, the number of detections is derived based on a plurality of comparison results obtained for each switch operation. Therefore, the accuracy of the number of detections is higher than that in the case of deriving the number of detections based on a single comparison result obtained for each switch operation.
According to the above configuration, the number of detections is obtained before the intermediate potential exceeds the reference potential.

( 3 ) The capacitance sensor that solves the above problems initializes the first capacitor, the second capacitor that is connected to the first capacitor and whose capacitance changes depending on the presence or absence of an object, and the first capacitor. The first switch, the second switch arranged between the first capacitor and the second capacitor, the third switch for initializing the second capacitor, the first switch, the second switch, and the like. The control circuit includes a control circuit for controlling the third switch, and the control circuit comprises an operation of the second switch and an operation of the third switch after the initialization of the first capacitor by the operation of the first switch. Switching control in which the switch operation is performed a plurality of times, and an intermediate potential which is a potential between the first capacitor and the second capacitor is acquired at a plurality of time points for each switch operation, and is based on the plurality of the intermediate potentials. A capacitance sensor that executes an operation to derive the number of detections corresponding to the number of operations of the switch when the intermediate potential exceeds the reference potential, and the control circuit is the switch in the operation. For each operation, a comparison operation for comparing the intermediate potential and the reference potential at a plurality of time points and an index derivation operation for deriving the number of detections based on the plurality of comparison results obtained by the comparison operation are executed. In the index derivation calculation, the control circuit derives the probability that the intermediate potential exceeds the reference potential based on the plurality of comparison results, and in the period before and after the intermediate potential exceeds the reference potential. The number of detections is derived based on a continuous function that associates the plurality of probabilities obtained at different time points with the number of operations of the plurality of switch operations.
The number of operation operations, that is, the number of detections of the switch operation when the intermediate potential exceeds the reference potential is an index indicating the capacity of the second capacitor. On the other hand, if there is noise in the intermediate potential, the accuracy of the index will decrease. In the above configuration, the number of detections is derived based on the intermediate potentials acquired at a plurality of time points. Therefore, the accuracy of the number of detections (the accuracy of the index indicating the capacity of the second capacitor) is higher than that in the case of deriving the number of detections based on a single intermediate potential. As a result, the detection accuracy of the capacitance sensor is improved.
According to the above configuration, the number of detections is derived based on a plurality of comparison results obtained for each switch operation. Therefore, the accuracy of the number of detections is higher than that in the case of deriving the number of detections based on a single comparison result obtained for each switch operation.
According to the above configuration, a continuous function is derived with the number of switch operations as one parameter. Therefore, the number of detections associated with the number of switch operations is obtained as a real number. As a result, the number of detections can be obtained with high resolution.

( 4 ) The capacitance sensor that solves the above problems initializes the first capacitor, the second capacitor that is connected to the first capacitor and whose capacitance changes depending on the presence or absence of an object, and the first capacitor. The first switch, the second switch arranged between the first capacitor and the second capacitor, the third switch for initializing the second capacitor, the first switch, the second switch, and the like. The control circuit includes a control circuit for controlling the third switch, and the control circuit comprises an operation of the second switch and an operation of the third switch after the initialization of the first capacitor by the operation of the first switch. Switching control in which the switch operation is performed a plurality of times, and an intermediate potential which is a potential between the first capacitor and the second capacitor is acquired at a plurality of time points for each switch operation, and is based on the plurality of the intermediate potentials. A capacitance sensor that executes an operation to derive the number of detections corresponding to the number of operations of the switch when the intermediate potential exceeds the reference potential, and the control circuit is the switch in the operation. For each operation, a comparison operation for comparing the intermediate potential and the reference potential at a plurality of time points and an index derivation operation for deriving the number of detections based on the plurality of comparison results obtained by the comparison operation are executed. The control circuit executes the index derivation operation after the time when the intermediate potential exceeds a predetermined potential set between the initial potential of the intermediate potential and the reference potential.
The number of operation operations, that is, the number of detections of the switch operation when the intermediate potential exceeds the reference potential is an index indicating the capacity of the second capacitor. On the other hand, if there is noise in the intermediate potential, the accuracy of the index will decrease. In the above configuration, the number of detections is derived based on the intermediate potentials acquired at a plurality of time points. Therefore, the accuracy of the number of detections (the accuracy of the index indicating the capacity of the second capacitor) is higher than that in the case of deriving the number of detections based on a single intermediate potential. As a result, the detection accuracy of the capacitance sensor is improved.
According to the above configuration, the number of detections is derived based on a plurality of comparison results obtained for each switch operation. Therefore, the accuracy of the number of detections is higher than that in the case of deriving the number of detections based on a single comparison result obtained for each switch operation.
According to the above configuration, the number of operations of the control circuit is limited, so that the load on the control circuit is reduced.

( 5 ) The capacitance sensor that solves the above problems initializes the first capacitor, the second capacitor that is connected to the first capacitor and whose capacitance changes depending on the presence or absence of an object, and the first capacitor. The first switch, the second switch arranged between the first capacitor and the second capacitor, the third switch for initializing the second capacitor, the first switch, the second switch, and the like. The control circuit includes a control circuit for controlling the third switch, and the control circuit comprises an operation of the second switch and an operation of the third switch after the initialization of the first capacitor by the operation of the first switch. Switching control in which the switch operation is performed a plurality of times, and an intermediate potential which is a potential between the first capacitor and the second capacitor is acquired at a plurality of time points for each switch operation, and is based on the plurality of the intermediate potentials. A capacitance sensor that executes an operation to derive the number of detections corresponding to the number of operations of the switch when the intermediate potential exceeds the reference potential, and the control circuit is the switch in the operation. An average value calculation for deriving the average value of the intermediate potential based on the intermediate potential and an index derivation calculation for deriving the number of detections based on the average value of the intermediate potential obtained at a plurality of time points for each operation. To execute.
The number of operation operations, that is, the number of detections of the switch operation when the intermediate potential exceeds the reference potential is an index indicating the capacity of the second capacitor. On the other hand, if there is noise in the intermediate potential, the accuracy of the index will decrease. In the above configuration, the number of detections is derived based on the intermediate potentials acquired at a plurality of time points. Therefore, the accuracy of the number of detections (the accuracy of the index indicating the capacity of the second capacitor) is higher than that in the case of deriving the number of detections based on a single intermediate potential. As a result, the detection accuracy of the capacitance sensor is improved.

According to the above configuration, the number of detections is derived based on the average value of the intermediate potentials obtained for each switch operation. Therefore, the accuracy of the number of detections is higher than that in the case of deriving the number of detections based on a single intermediate potential obtained for each switch operation.

(8) In the capacitance sensor, the control circuit uses the number of operations of the switch when the average value of the intermediate potential exceeds the reference potential as the number of detections in the index derivation calculation. According to this configuration, the number of detections is obtained when the average value of the intermediate potentials exceeds the reference potential.

(9) In the capacitance sensor, the control circuit is a plurality of mean values of the plurality of intermediate potentials obtained at different time points in a period before the intermediate potential exceeds the reference potential in the index derivation calculation. The number of detections is derived based on the function associated with the number of operations of the switch. According to this configuration, the number of detections is obtained before the intermediate potential exceeds the reference potential.

(10) In the capacitance sensor, the control circuit has a plurality of average values of the intermediate potentials obtained at different time points in the period before and after the intermediate potential exceeds the reference potential in the index derivation calculation. The number of detections is derived based on a continuous function that associates with the number of operations of the switch. According to this configuration, a continuous function with the number of switch operations as one parameter is derived. Therefore, the number of detections associated with the number of switch operations is obtained as a real number. As a result, the number of detections can be obtained with high resolution.

(11) In the capacitance sensor, the control circuit performs the index derivation operation after the intermediate potential exceeds a specified potential set between the initial potential of the intermediate potential and the reference potential. Execute. According to this configuration, the number of operations of the control circuit is limited, so that the load on the control circuit is reduced.

(1 0) capacitive sensor for solving the above-mentioned problems, initializes a first capacitor, a second capacitor whose capacitance changes based on the presence or absence of the connection has been an object in the first capacitor, said first capacitor The first switch, the second switch arranged between the first capacitor and the second capacitor, the third switch for initializing the second capacitor, the first switch, the second switch, and the like. And a control circuit for controlling the third switch, the control circuit is composed of the operation of the second switch and the operation of the third switch after the initialization of the first capacitor by the operation of the first switch. Switching control in which the switch operation is performed a plurality of times, and an intermediate potential which is a potential between the first capacitor and the second capacitor is acquired at a plurality of time points for each switch operation, and the intermediate potentials are set to the plurality of intermediate potentials. Based on this, it is a capacitance sensor that executes an operation for deriving the number of detections corresponding to the number of operations of the switch when the intermediate potential exceeds the reference potential, and is attached to at least one electrode of the first capacitor. Is input with noise that follows a normal distribution.
The number of operation operations, that is, the number of detections of the switch operation when the intermediate potential exceeds the reference potential is an index indicating the capacity of the second capacitor. On the other hand, if there is noise in the intermediate potential, the accuracy of the index will decrease. In the above configuration, the number of detections is derived based on the intermediate potentials acquired at a plurality of time points. Therefore, the accuracy of the number of detections (the accuracy of the index indicating the capacity of the second capacitor) is higher than that in the case of deriving the number of detections based on a single intermediate potential. As a result, the detection accuracy of the capacitance sensor is improved.
The intermediate potential contains noise. If there is a bias or peak in this noise, the accuracy of the above-mentioned probability and the average value of the intermediate potential will decrease. In this respect, according to the above configuration, noise following a normal distribution is input to at least one electrode of the first capacitor. As a result, it is possible to suppress the derivation of abnormal comparison results and average values as compared with the case where noise following a normal distribution is not applied.

According to the capacitance sensor, the detection accuracy can be improved.

A circuit diagram of a capacitance sensor according to the first embodiment. Timing chart of each signal for the capacitance sensor. The graph which shows typically the relationship between the capacity of 2nd capacitor and the number of detections. A graph showing noise at intermediate potentials. The graph which shows the transition of an intermediate potential and the noise width of an intermediate potential. A chart showing the output signal of the comparison circuit. A graph showing the relationship between the probability and the number of operations for the second embodiment. A graph schematically showing the relationship between the capacitance of the second capacitor and the detection difference for the third embodiment. A graph showing the relationship between the probability and the number of operations for the third embodiment. A circuit diagram of a capacitance sensor according to a fourth embodiment. A graph showing the relationship between the average value of intermediate potentials and the number of operations for the fifth embodiment. A graph showing the relationship between the average value of intermediate potentials and the number of operations for the sixth embodiment. The graph which shows the distribution of noise about 7th Embodiment.

<First Embodiment>
The capacitance sensor will be described with reference to FIGS. 1 to 6.
The capacitance sensor 1 according to the embodiment can be used as, for example, a touch sensor mounted on a handle of a vehicle door. The capacitance sensor 1 is based on the fact that an object (for example, a hand that is a part of the body, an object attached to the body, or an deposit such as raindrops) is placed in the vicinity of the capacitance sensor 1. , Detect its presence. The information regarding the presence / absence of an object detected by the capacitance sensor 1 is used, for example, for permitting locking / unlocking of a vehicle door.

In some types of capacitance sensor 1, detection of an object within a predetermined distance from the capacitance sensor 1 is required. That is, it is required to detect an object arranged apart from the capacitance sensor 1. In such a case, since the capacitance change of the capacitance sensor 1 is small, such a capacitance sensor 1 is required to have high-precision detection performance. The circuit example shown below is an example of a circuit capable of such high-precision detection, but its application is not limited to the capacitance sensor 1 capable of high-precision detection.

The capacitance sensor 1 includes a first capacitor 11, a second capacitor 12, a first switch 21, a second switch 22, a third switch 23, and a control circuit 30.
The first capacitor 11 has a predetermined capacitance. As the first capacitor 11, a capacitor whose capacitance does not change based on the presence or absence of an object is used.

The capacity of the second capacitor 12 can be changed depending on the presence or absence of an object. For example, the second capacitor 12 is arranged in a place where the capacitance (capacity of the second capacitor 12) can be changed by arranging the second capacitor 12 in the vicinity of the second capacitor 12. "Arranged in the vicinity of the second capacitor 12" means that the object is arranged so as to come into contact with the second capacitor 12, and is arranged in the vicinity of the second capacitor 12 via a cover or the like covering the second capacitor 12. It includes being done, placing an object near the second capacitor 12 through space, passing near the second capacitor 12, and approaching the second capacitor 12. Further, the second capacitor 12 is configured so that the capacitance of the second capacitor 12 changes based on the fact that an object is arranged in the vicinity of the second capacitor 12. For example, at least one of the pair of electrodes constituting the second capacitor 12 is configured to have a size such that the capacitance of the second capacitor 12 can change when an object (for example, a hand) and the electrode face each other. To.

The second capacitor 12 is connected to the first capacitor 11. Specifically, the first capacitor 11 and the second capacitor 12 are connected in series between two wires having different potentials. One end of the first capacitor 11 is connected to the wiring of the first potential V1, and the other end of the first capacitor 11 is connected to one end of the second capacitor 12 via the second switch 22. The other end of the second capacitor 12 is connected to the wiring of the second potential V2. The first potential V1 is larger than the reference potential Vref described later, and the second potential V2 is smaller than the reference potential Vref. The second potential V2 is set to, for example, the same potential as the ground.

The first switch 21 initializes the first capacitor 11. Specifically, the first switch 21 is arranged in the wiring 13 connected in parallel to the first capacitor 11, and connects or disconnects the wiring 13. The second switch 22 is provided in the wiring 14 connecting the first capacitor 11 and the second capacitor 12, and connects or disconnects the wiring 14. The third switch 23 initializes the second capacitor 12. Specifically, the third switch 23 is connected in parallel to the second capacitor 12 and arranged in the wiring 15, and the wiring 15 is connected or disconnected. In the following description, on of the first switch 21, second switch 22 and third switch 23 indicates the connection of the respective wirings 13, 14 and 15, and off indicates the interruption of the respective wirings 13, 14 and 15 ( Electrical disconnection) is shown.

The control circuit 30 includes a switch control circuit 31, a comparison circuit 32, and an arithmetic circuit 33.
The switch control circuit 31 controls the first switch 21, the second switch 22, and the third switch 23 (switching control).

The comparison circuit 32 compares the intermediate potential VM with the reference potential Vref (comparison calculation). The intermediate potential VM indicates the potential of the portion between the first capacitor 11 and the second switch 22 and between the first capacitor 11 and the second switch 22.

The calculation circuit 33 derives the number of detections N (see below) based on the output signal (that is, the comparison result) of the comparison circuit 32 (index derivation calculation).

The operation of the switching control and the arithmetic circuit 33 executed by the switch control circuit 31 will be described with reference to FIG.
The first switch 21, the second switch 22, and the third switch 23 operate in a predetermined cycle. At the beginning of the cycle, the first switch 21 is controlled to be on, and the second switch 22 and the third switch 23 are controlled to be off. As a result, the first capacitor 11 is initialized, and the intermediate potential VM becomes equal to the first potential V1. In the following description, the intermediate potential VM when the first capacitor 11 is initialized is referred to as "initial potential" (the initial potential is equal to the first potential V1).

Next, the first switch 21 is controlled to be off, the second switch 22 is controlled to be on, and the third switch 23 is maintained to be off (hereinafter, this switch operation is referred to as "second switch operation"). .. At this time, a current flows through the first capacitor 11 and the second capacitor 12, and the intermediate potential VM drops.

Next, the first switch 21 is kept off, the second switch 22 is controlled to be off, and the third switch 23 is controlled to be on (hereinafter, this switch operation is referred to as "third switch operation"). .. At this time, the second capacitor 12 is initialized.

Subsequently, the second switch operation and the third switch operation are alternately executed while the first switch 21 is kept off. Therefore, as shown in FIG. 2, the intermediate potential VM gradually decreases. In the following description, a pair of operations of the second switch operation and the third switch operation following this operation will be referred to as "switch operation".

The switch operation is performed a predetermined number of times (a number of times greater than 1). The predetermined number of times is larger than the number of times required for the intermediate potential VM to exceed the reference potential Vref when the second capacitor 12 has the minimum capacitance. That is, no matter what capacity the second capacitor 12 has, the intermediate potential VM exceeds the reference potential Vref by executing the switch operation a predetermined number of times. The fact that the intermediate potential VM exceeds the reference potential Vref indicates that the magnitude relationship between the intermediate potential VM and the reference potential Vref is opposite from the beginning (when the first switch 21 is turned on). In this example, since the intermediate potential VM is initially higher than the reference potential Vref, "exceeding" means that the intermediate potential VM is lower than the reference potential Vref.

The comparison circuit 32 outputs a signal indicating whether or not the intermediate potential VM exceeds the reference potential Vref. In the following description, for convenience, the signal indicating that the intermediate potential VM exceeds the reference potential Vref is referred to as an “on signal”, and the signal indicating that the intermediate potential VM does not exceed the reference potential Vref is “off”. It is called "signal".

The arithmetic circuit 33 performs the following four arithmetic operations.
In the first calculation, the number of switch operations is counted. The number of operations is initialized when the first switch 21 is turned on (that is, the number of operations = "0"). Each time the second switch 22 (or the third switch 23) is turned on by the switch control circuit 31, the arithmetic circuit 33 increments the number of operations by one. In this way, the number of switch operations is counted.

In the second calculation, the probability PE of whether or not the intermediate potential VM exceeds the reference potential Vref is calculated based on the output signal of the comparison circuit 32.
In the third calculation, the number of switch operations (that is, the number of detections N) when the intermediate potential VM exceeds the reference potential Vref is obtained. Probability PE is used to determine "when the intermediate potential VM exceeds the reference potential Vref". For example, when the probability PE exceeds the specified probability (for example, 50%), it is determined that "the intermediate potential VM exceeds the reference potential Vref", and in this determination result, the number of operations counted in the first calculation is ". It is stored as "the number of detections N".

The technical meaning of the number of detections N will be described with reference to FIG. FIG. 3 is a graph schematically showing the relationship between the capacitance of the second capacitor 12 and the number of detections N. When the capacitance of the second capacitor 12 is small, the amount of change in the intermediate potential VM per switch operation is small, so the number of detections N becomes a large value. When the capacity of the second capacitor 12 is large (for example, when an object is arranged near the capacitance sensor 1), the amount of change in the intermediate potential VM per switch operation is large, so the number of detections N is a small value. become. That is, the number of detections N is an index of the capacity of the second capacitor 12.

In the fourth calculation, the detection difference ΔN is calculated based on the number of detections N and the reference value.
The reference value may be a preset value, but it is preferable that the past detection number N is used. The past detection number N1 indicates the detection number N obtained at the time tp before a predetermined time from the time ct at which the detection number N2 related to the fourth calculation was obtained. Then, the difference (− (N2-N1), hereinafter “detection difference ΔN”) between the past (time tp) detection number N1 and the present (time tk) detection number N2 is calculated. The detection difference ΔN serves as an index of the amount of change in the capacitance of the second capacitor 12. Then, the detection difference ΔN and the reference difference ΔNA are compared. When the detection difference ΔN is larger than the reference difference ΔNA, it is determined that an object exists in the vicinity of the capacitance sensor 1.

The reason for using the past number of detections N as the reference value is that the capacity of the second capacitor 12 changes depending on the environment (temperature and humidity), and the capacity of the second capacitor 12 varies due to individual differences. This is because it is difficult to set an appropriate fixed value corresponding to the initial capacitance of the second capacitor 12.

Next, the second operation will be described in detail.
As described above, in the second calculation, the probability PE of whether or not the intermediate potential VM exceeds the reference potential Vref is calculated based on the output signal of the comparison circuit 32. Here, the reason for calculating the "probability PE of whether or not the intermediate potential VM exceeds the reference potential Vref" will be described.

As shown in FIG. 4, the intermediate potential VM fluctuates with time. That is, the intermediate potential VM has "noise". "Noise" is caused by external noise (electromagnetic waves, etc.) and noise of the power supply voltage.

Since the intermediate potential VM contains noise, even when the capacitance of the second capacitor 12 is constant at a predetermined value, the intermediate potential VM becomes a different value depending on the detection time (see the black dot in FIG. 4), and the intermediate potential VM becomes different. The determination result of whether or not the reference potential Vref is exceeded will be different. As a result, the number of detections N and the detection difference ΔN become different. In particular, when the detection difference ΔN is close to the reference difference ΔNA, the determination result of the presence or absence of the object becomes different.

An example in which the presence / absence determination of an object has different results will be described with reference to FIG. FIG. 5 is a diagram showing the transition of the intermediate potential VM, and the two-dot chain line shows the upper limit and the lower limit of the intermediate potential VM caused by noise.

During the comparison operation by the comparison circuit 32, when the intermediate potential VM happens to be the minimum value in the noise width and exceeds the reference potential Vref (see part A in FIG. 5), the intermediate potential VM is referred to in the control circuit 30. It is determined that the potential Vref is exceeded. In this case, the timing at which the intermediate potential VM exceeds the reference potential Vref is earlier than when there is no noise, and the detection difference ΔN becomes smaller. When the detection difference ΔN is close to the reference difference ΔNA, the detection difference ΔN is underestimated, and as a result, the result may be the opposite of the determination result when there is no noise. As described above, the accuracy of determining the existence or nonexistence of an object is limited due to the noise of the intermediate potential VM. Therefore, in the present embodiment, the accuracy of whether or not the intermediate potential VM exceeds the reference potential Vref is improved for the purpose of improving the accuracy of determining the presence or absence of the object. Then, as a means for improving this accuracy, the above-mentioned probability PE, that is, the probability PE of whether or not the intermediate potential VM exceeds the reference potential Vref is introduced. By determining whether or not the intermediate potential VM exceeds the reference potential Vref based on the probability PE, the influence of noise in the determination can be reduced, so that an accurate determination becomes possible.

An example of a method of calculating "probability PE of whether or not the intermediate potential VM exceeds the reference potential Vref" will be described with reference to FIG. In the second calculation, the probability PE is calculated based on the output signal (that is, the comparison result) of the comparison circuit 32. Specifically, in the second calculation, the calculation circuit 33 acquires the output signal of the comparison circuit 32 in each of a plurality of consecutive sections S in the time series, and totals the number of on signals of the output signal in each section S. To do. This aggregation is executed when the second switch 22 is off (see FIG. 2 “Operation of arithmetic circuit”). Then, the arithmetic circuit 33 calculates the probability PE as the number of on signals (that is, the signal indicating that the intermediate potential VM exceeds the reference potential Vref) / the number of sections × 100.

Then, as described above, in the third calculation, when the probability PE calculated by the second calculation exceeds the specified probability (for example, 50%), the calculation circuit 33 counts the number of operations in the first calculation. Is stored as "detection count N". Therefore, the number of detections N is not determined only by the result that the intermediate potential VM accidentally exceeds the reference potential Vref. In this way, the accuracy of determining the existence of an object is improved.

Next, the operation and effect of the capacitance sensor 1 will be described.
(1) The control circuit 30 acquires the intermediate potential VM at a plurality of time points for each switch operation, and derives the number of detections N based on the plurality of intermediate potential VMs.

The number of switch operations, that is, the number of detections N when the intermediate potential VM exceeds the reference potential Vref, is an index indicating the capacity of the second capacitor 12. On the other hand, if there is noise in the intermediate potential VM, the accuracy of the index is lowered. In the above configuration, the number of detections N is derived based on the intermediate potential VM acquired at a plurality of time points. Therefore, the accuracy of the number of detections N (the accuracy of the index indicating the capacity of the second capacitor 12) is higher than in the case of deriving the number of detections N based on a single intermediate potential VM. As a result, the detection accuracy of the capacitance sensor 1 is improved.

(2) Specifically, the control circuit 30 compares the intermediate potential VM and the reference potential Vref at a plurality of time points for each switch operation in the calculation. The number of detections N is derived based on a plurality of comparison results (output signals of the comparison circuit 32 at a plurality of time points) obtained by the comparison.

According to this configuration, it is derived as the number of detections N based on a plurality of comparison results obtained for each switch operation. Therefore, the accuracy of the number of detections N is higher than that in the case of deriving the number of detections N based on a single comparison result obtained for each switch operation.

(3) The control circuit 30 calculates the probability PE at which the intermediate potential VM exceeds the reference potential Vref based on the plurality of comparison results. When the probability PE exceeds the specified probability, the number of switch operations at that time is defined as the number of detections N. According to this configuration, the number of detections N is derived based on the probability PE.

<Second Embodiment>
In this embodiment, a method of estimating the “number of detections N” will be described.
In the first embodiment, when the probability PE exceeds the specified probability (for example, 50%), the number of operations counted in the first calculation is stored as "detection number N". That is, in the first embodiment, the switch operation, the first operation, and the second operation are repeated at least until the probability PE exceeds the specified probability, and thus the "detection number N" is determined. On the other hand, in the present embodiment, the "detection number N" is estimated before the probability PE exceeds the specified probability.

An example of estimating the number of detections N will be described with reference to FIG. 7.
The control circuit 30 calculates the probability PE at which the intermediate potential VM exceeds the reference potential Vref for each switch operation. Then, in the period before the probability PE exceeds the specified probability, a function (for example, a first-order approximate expression φ1) that correlates the number of switch operations by the first operation with the probability PE is derived, and based on this function, Estimate the number of operations for which the probability PE becomes the specified probability. The number of operations estimated in this way is stored as "number of detections N".

The effects of this embodiment will be described below.
In this embodiment, a function for associating a plurality of probability PEs with a plurality of switch operation operations obtained at different time points in a period before the intermediate potential VM exceeds the reference potential Vref is derived. Then, the number of detections N is derived based on this function. According to this configuration, the number of detections N is obtained before the intermediate potential VM exceeds the reference potential Vref. When the number of detections N is obtained, the switching control and the first to third operations can be stopped until the start time of the next cycle. Therefore, according to this configuration, it is possible to suppress the power consumption of the control circuit 30.

<Third Embodiment>
In the present embodiment, the realization of the “detection number N” will be described.
In the first embodiment, when the probability PE exceeds the specified probability, the number of operations counted in the first calculation is stored as "detection number N". Therefore, the number of detections N is an integer. When the number of detections N is an integer, the detection difference ΔN derived from the number of detections N is also an integer. Then, even if the reference difference ΔNA is finely adjusted in the numerical range of less than 1, the change in the reference difference ΔNA due to the fine adjustment does not appear in the comparison between the detection difference ΔN and the reference difference ΔNA. This point will be described below.

FIG. 8 is a diagram showing the relationship between the capacitance change amount of the second capacitor 12 and the detection difference ΔN. The solid line shows the relationship between the “amount of change in capacitance of the second capacitor 12” and the “detection difference ΔN obtained in the first embodiment”. The two-dot chain line shows the relationship between the "capacitive change amount of the second capacitor 12" and the "detection difference ΔN obtained in the present embodiment". One of the alternate long and short dash lines is a line showing the reference difference ΔNA (1) before the change, and the other of the alternate long and short dash lines is a line showing the reference difference ΔNA (2) after the setting change.

When the detection difference ΔN is an integer (that is, a discrete value), the two detection differences ΔN corresponding to the capacitance changes of the two second capacitors 12 in the unit interval SB are equal. Therefore, even if the setting of the reference difference ΔNA is changed in the range after the decimal point (see the reference difference ΔNA (1) and ΔNA (2)), the two detection differences ΔN and the reference difference ΔNA (1) and ΔNA (2) Since the relationship between the two detection differences ΔN does not change, the comparison results between the two detection differences ΔN and the reference differences ΔNA (1) and ΔNA (2) are the same. Therefore, there is no effect by fine-tuning the reference difference ΔNA. That is, it is not possible to distinguish the amount of change in capacitance between the two second capacitors 12 in the unit interval SB. As described above, when the detection difference ΔN is an integer, there is a limit to the resolution for detecting the capacitance change amount of the second capacitor 12. Therefore, in the present embodiment, the "detection number N" is made a real number for the purpose of improving the resolution in detecting the capacitance change amount of the second capacitor 12.

An example of realizing the “number of detections N” will be described with reference to FIG.
For each switch operation, the probability PE at which the intermediate potential VM exceeds the reference potential Vref is calculated. Then, in the period before and after the probability PE exceeds the specified probability (for example, 50%), a continuous function (for example, the first-order approximate expression φ2) that correlates the number of operation of the switch operation by the first operation with the probability PE is derived. Next, the intersection where this function and the line of the specified probability intersect is derived. The number of operations of the intersection derived in this way is stored as "detection number N".

The number of detections N thus obtained is a continuous number (that is, a real number). The relationship between the number of detections N and the amount of change in the capacitance of the second capacitor 12 is as shown by the alternate long and short dash line L in FIG. That is, the number of detections N is a value corresponding to each of the capacitance changes even when the capacitance change of the second capacitor 12 changes slightly. Therefore, when the reference difference ΔNA is finely adjusted, the two detection differences ΔN corresponding to the capacitance changes of the two second capacitors 12 in the unit interval SB are compared with the reference differences ΔNA (1) and ΔNA (2). Then, the comparison result can be different. In this way, the effect of fine-tuning the reference difference ΔNA is exhibited.

The effects of this embodiment will be described below.
In the present embodiment, the control circuit 30 derives a continuous function that associates a plurality of probability PEs obtained at different time points in the period before and after the intermediate potential VM exceeds the reference potential Vref with the number of operations of the plurality of switch operations. Then, the number of detections N is derived based on this continuous function. As a result, the number of detections N associated with the number of switch operations is obtained as a real number. That is, the number of detections N can be obtained with high resolution.

<Fourth Embodiment>
In the present embodiment, a means different from the first embodiment will be described as a means for improving the accuracy of the determination result of the presence or absence of the object. Hereinafter, the differences between the present embodiment and the first embodiment will be described.

As shown in FIG. 10, the capacitance sensor 2 of the present embodiment has the structure of the first embodiment for configurations other than the control circuit 30.
The control circuit 40 includes a switch control circuit 41, an average value calculation circuit 42, and a calculation circuit 43.

The switch control circuit 41 controls the first switch 21, the second switch 22, and the third switch 23 (see below). The switching control executed by the switch control circuit 41 conforms to the switching control shown in the first embodiment.

The mean value calculation circuit 42 calculates the mean value VMA of the intermediate potential VM (mean value calculation). For example, the mean value calculation circuit 42 has an integration circuit that integrates the intermediate potential VM over a predetermined period of time. The mean value calculation circuit 42 outputs a value obtained by dividing the output value of the integrator circuit by a specified value as "the average value VMA of the intermediate potential VM".

The calculation circuit 43 derives the number of detections N based on the “mean value VMA of the intermediate potential VM” calculated by the mean value calculation circuit 42 (index derivation calculation). The arithmetic circuit 43 executes the following four arithmetic operations.

In the first calculation, the number of switch operations is counted. The first operation is the same as that of the first embodiment.
In the second calculation, it is determined whether or not the average value VMA of the intermediate potential VM exceeds the reference potential Vref based on the output signal of the mean value calculation circuit 42. Hereinafter, the determination when the average value VMA of the intermediate potential VM exceeds the reference potential Vref is referred to as “affirmative determination”.

In the third operation, when the determination calculated by the second operation is an affirmative determination, the number of operations counted in the first operation is stored as "detection number N".
In the fourth calculation, the detection difference ΔN is calculated by comparing the number of detections N with the reference value. The fourth operation conforms to the fourth operation of the first embodiment.

The reason for calculating the "mean value VMA of the intermediate potential VM" in the mean value calculation circuit 42 is the same as the reason for calculating the "probability PE of whether or not the intermediate potential VM exceeds the reference potential Vref". That is, due to the noise of the intermediate potential VM, the accuracy of determining the presence or absence of an object is limited. Therefore, the accuracy of the intermediate potential VM is increased for the purpose of improving the accuracy of determining the presence or absence of an object. Then, as a means for improving the accuracy of the intermediate potential VM, the average value VMA of the intermediate potential VM is calculated. In addition, "improvement of accuracy of intermediate potential VM" means that the difference between the intermediate potential VM without noise (that is, the true intermediate potential VM) and the intermediate potential VM becomes small.

The noise is averaged up and down and dispersed with respect to the true value of the intermediate potential VM. Therefore, the average value VMA of the intermediate potential VM is considered to be close to the true value. At least, the dissociation of the mean value VMA of the intermediate potential VM with respect to the true value is smaller than that of the intermediate potential VM acquired at any one time point. Therefore, the accuracy of the intermediate potential VM can be improved by using the average value VMA of the intermediate potential VM.

Then, when it is determined that the "average value VMA of the intermediate potential VM" exceeds the reference potential Vref, the number of operations counted in the first calculation is stored as the "detection number N". That is, the number of detections N is not determined only by the result that the intermediate potential VM accidentally exceeds the reference potential Vref. In this way, the accuracy of the determination result regarding the existence or nonexistence of the object is improved.

The effects of this embodiment will be described below.
In the present embodiment, it is derived as the number of detections N based on the average value VMA of the intermediate potential VM obtained for each switch operation. Therefore, the accuracy of the number of detections N is higher than that in the case of deriving the number of detections N based on a single intermediate potential VM obtained for each switch operation.

Further, when the average value VMA of the intermediate potential VM exceeds the reference potential Vref, the control circuit 40 sets the number of times of switch operation at that time as the number of detections N. According to this configuration, the number of detections N is obtained when the average value VMA of the intermediate potential VM exceeds the reference potential Vref.

<Fifth Embodiment>
In this embodiment, a method of estimating the “number of detections N” will be described.
In the fourth embodiment, when the determination calculated by the second operation is an affirmative determination, the number of operations counted in the first operation is stored as "detection number N". That is, in the fourth embodiment, the switch operation, the first operation, and the second operation are repeated at least until the determination of the second operation becomes a positive determination, and thus the "detection number N" is determined. On the other hand, in the present embodiment, the "detection number N" is estimated before the determination of the second operation becomes an affirmative determination. An example thereof will be described below.

An example of estimating the number of detections N will be described with reference to FIG.
The mean value calculation circuit 42 calculates the mean value VMA of the intermediate potential VM for each switch operation. Then, in the period before the average value VMA of the intermediate potential VM exceeds the reference potential Vref, a function that correlates the number of switch operations by the first calculation with the average value VMA of the intermediate potential VM (for example, the first-order approximate expression φ3). ) Is derived. Then, based on this function, the number of operations in which the average value VMA of the intermediate potential VM becomes equal to the average value VMA of the intermediate potential VM is estimated. The number of operations estimated in this way is stored as "number of detections N".

The effects of this embodiment will be described below.
In the present embodiment, the control circuit 40 associates the mean value VMA of the plurality of intermediate potential VMs obtained at different time points in the period before the intermediate potential VM exceeds the reference potential Vref with the number of operations of the plurality of switch operations. Derive the function. Then, the number of detections N is derived based on this function. According to this configuration, the number of detections N is obtained before the intermediate potential VM exceeds the reference potential Vref. When the number of detections N is obtained, the switching control and the first to third operations can be stopped until the start time of the next cycle. Therefore, according to this configuration, it is possible to suppress the power consumption of the control circuit 40.

<Sixth Embodiment>
In the present embodiment, the realization of the “detection number N” will be described.
In the fourth embodiment, when the average value VMA of the intermediate potential VM exceeds the reference potential Vref (that is, when the "affirmative determination" is made), the number of operations counted in the first calculation is "detection number N". Remember as. Therefore, the number of detections N is an integer. When the number of detections N is an integer, the detection difference ΔN derived from the number of detections N is also an integer. Then, even if the reference difference ΔNA is finely adjusted in the numerical range of less than 1, the change in the reference difference ΔNA due to the fine adjustment does not appear in the comparison between the detection difference ΔN and the reference difference ΔNA. This point is as described with reference to FIG. 8 in the third embodiment. Therefore, in the present embodiment, in the present embodiment, the "detection number N" is made a real number for the purpose of improving the resolution in detecting the capacitance change amount of the second capacitor 12.

The realization of the number of detections N will be described with reference to FIG.
The average value VMA of the intermediate potential VM is calculated for each switch operation. Then, in the period before and after the average value VMA of the intermediate potential VM exceeds the reference value, a continuous function (for example, a first-order approximate expression φ4) that correlates the number of switch operations by the first calculation with the average value VMA of the intermediate potential VM. Is derived. Then, the intersection point where this function and the reference potential Vref intersect is derived. The number of operations of the intersection derived in this way is stored as "detection number N".

The effects of this embodiment will be described below.
In the present embodiment, the control circuit 40 continuously associates the mean value VMA of the plurality of intermediate potential VMs obtained at different time points in the period before and after the intermediate potential VM exceeds the reference potential Vref with the number of operations of the plurality of switch operations. Derive the function. Then, the number of detections N is derived based on this continuous function. As a result, the number of detections N associated with the number of switch operations is obtained as a real number. That is, the number of detections N can be obtained with high resolution.

<7th Embodiment>
In this embodiment, a technique applicable to any of the first to sixth embodiments will be described.

The problem in the first to sixth embodiments is caused by the noise of the intermediate potential VM. Since the noise of the intermediate potential VM is irregular, the distribution of the intermediate potential VM in a predetermined period becomes a normal distribution with the true intermediate potential VM as the median. However, the disturbance may cause noise bias or include abnormally high peaks. Then, the distribution of the intermediate potential VM may not follow the normal distribution. In this case, the accuracy of the average value VMA of the probability PE and the intermediate potential VM calculated in the first to sixth embodiments is lowered. Therefore, in the present embodiment, noise following a normal distribution is input to at least one electrode of the first capacitor 11.

An example of noise input to the electrode of the first capacitor 11 will be described with reference to FIG. Noise that follows a normal distribution means that the frequency distribution of the magnitude (potential) of noise, which has a population of multiple noises in a unit time, has a normal distribution. The preferred normal distribution is shown below. For example, a value three times the standard deviation σ is larger than the average change width ΔVM of the potential change width of the intermediate potential VM, and a value twice the standard deviation σ is the average change width ΔVM of the potential change width of the intermediate potential VM. Smaller than

If the noise dispersion is too small, the influence of noise due to external factors on the comparison result and the average value VMA becomes large, and the effect of noise input is lost. This is because if the noise dispersion is too large, the probability PE and the average value VMA are dispersed. Therefore, it is preferable that the noise dispersion is defined as described above.

By inputting such noise, the original noise and the input noise are combined, and the influence of the original noise on the combined noise is reduced. Therefore, even if the original noise includes disturbance, its influence becomes small, and as a result, the decrease in accuracy of the probability PE and the average value VMA of the intermediate potential VM due to the disturbance is suppressed. As a result, it is possible to suppress the derivation of an abnormal probability PE and an average value VMA as compared with the case where noise following a normal distribution is not applied.

<Other Embodiments>
-In each embodiment, the switch operations (second switch operation and third switch operation) are configured to be executed a predetermined number of times, which can be changed as follows. That is, the switch operation is executed only for the period from the initial potential to the reference potential Vref of the intermediate potential VM. According to this configuration, the number of switch operations is reduced as compared with the example of the embodiment, so that the power consumption of the control circuits 30 and 40 can be suppressed.

-In the first to third embodiments, the calculation of the probability PE for each switch operation may be performed under the following conditions. That is, the probability PE is calculated after the intermediate potential VM exceeds the specified potential Vx. Here, the defined potential Vx (see FIG. 2) is a potential set between the initial potential (first potential V1) of the intermediate potential VM and the reference potential Vref. As a result, when the number of switch operations is small and the probability PE is close to 0%, that is, when the calculation of the probability PE is ineffective, the calculation of the probability PE (index derivation calculation) is not performed. As a result, the number of operations of the control circuit 30 is limited, and the burden on the control circuit 30 can be reduced while exerting the effects of each embodiment.

-In the fourth to sixth embodiments, the calculation of the average value VMA of the intermediate potential VM for each switch operation may be performed under the following conditions. That is, after the intermediate potential VM exceeds the specified potential Vx (see FIG. 2), the average value VMA of the intermediate potential VM is calculated. As a result, the average value VMA is calculated (index derivation operation) when the number of switch operations is small and the possibility that the intermediate potential VM exceeds the reference potential Vref is low, that is, when the calculation of the average value VMA is ineffective. Absent. As a result, the number of operations of the control circuit 40 is limited, and the burden on the control circuit 30 can be reduced while exerting the effects of each embodiment.

1 ... Capacitance sensor, 2 ... Capacitance sensor, 11 ... 1st capacitor, 12 ... 2nd capacitor, 13 ... Wiring, 14 ... Wiring, 15 ... Wiring, 21 ... 1st switch, 22 ... 2nd switch, 23 ... 3rd switch, 30 ... control circuit, 31 ... switch control circuit, 32 ... comparison circuit, 33 ... arithmetic circuit, 40 ... control circuit, 41 ... switch control circuit, 42 ... average value arithmetic circuit, 43 ... arithmetic circuit, PE ... probability, S ... interval, SB ... unit interval, V1 ... first potential, V2 ... second potential, Vref ... reference potential, Vx ... specified potential, VM ... intermediate potential, VMA ... average value, φ1 ... first-order approximation Equation, φ2 ... 1st order approximation expression, φ3 ... 1st order approximation expression, φ4 ... 1st order approximation expression, N ... number of detections, ΔN ... detection difference, ΔNA ... reference difference.

Claims (10)

A first capacitor, a second capacitor connected to the first capacitor and whose capacitance changes depending on the presence or absence of an object, a first switch that initializes the first capacitor, the first capacitor, and the second capacitor. A second switch arranged between the two, a third switch for initializing the second capacitor, and a control circuit for controlling the first switch, the second switch, and the third switch are provided.
The control circuit
Switching control in which after the initialization of the first capacitor by the operation of the first switch, the switch operation including the operation of the second switch and the operation of the third switch is performed a plurality of times.
Each time the switch is operated, an intermediate potential that is a potential between the first capacitor and the second capacitor is acquired at a plurality of time points, and the intermediate potential exceeds the reference potential based on the plurality of intermediate potentials. A capacitance sensor that executes an operation to derive the number of detections corresponding to the number of operations of the switch at that time.
The control circuit is used in the calculation.
A comparison operation for comparing the intermediate potential and the reference potential at a plurality of time points for each switch operation,
An index derivation operation for deriving the number of detections based on a plurality of comparison results obtained by the comparison operation is executed.
The control circuit is used in the index derivation calculation.
The probability that the intermediate potential exceeds the reference potential is calculated based on the plurality of comparison results, and when the probability exceeds the specified probability, the number of operations of the switch operation at the time when the probability exceeds the specified probability is calculated. Capacitance sensor for the number of detections . A first capacitor, a second capacitor connected to the first capacitor and whose capacitance changes depending on the presence or absence of an object, a first switch that initializes the first capacitor, the first capacitor, and the second capacitor. A second switch arranged between the two, a third switch for initializing the second capacitor, and a control circuit for controlling the first switch, the second switch, and the third switch are provided.
The control circuit
Switching control in which after the initialization of the first capacitor by the operation of the first switch, the switch operation including the operation of the second switch and the operation of the third switch is performed a plurality of times.
Each time the switch is operated, an intermediate potential that is a potential between the first capacitor and the second capacitor is acquired at a plurality of time points, and the intermediate potential exceeds the reference potential based on the plurality of intermediate potentials. A capacitance sensor that executes an operation to derive the number of detections corresponding to the number of operations of the switch at that time.
The control circuit is used in the calculation.
A comparison operation for comparing the intermediate potential and the reference potential at a plurality of time points for each switch operation,
An index derivation operation for deriving the number of detections based on a plurality of comparison results obtained by the comparison operation is executed.
The control circuit is used in the index derivation calculation.
Based on the plurality of comparison results, the probability that the intermediate potential exceeds the reference potential is derived, and the plurality of probabilities and the plurality of switches obtained at different time points in the period before the intermediate potential exceeds the reference potential. The number of detections is derived based on the function that associates the number of operations with the number of operations.
Capacitance sensor. A first capacitor, a second capacitor connected to the first capacitor and whose capacitance changes depending on the presence or absence of an object, a first switch that initializes the first capacitor, the first capacitor, and the second capacitor. A second switch arranged between the two, a third switch for initializing the second capacitor, and a control circuit for controlling the first switch, the second switch, and the third switch are provided.
The control circuit
Switching control in which after the initialization of the first capacitor by the operation of the first switch, the switch operation including the operation of the second switch and the operation of the third switch is performed a plurality of times.
Each time the switch is operated, an intermediate potential that is a potential between the first capacitor and the second capacitor is acquired at a plurality of time points, and the intermediate potential exceeds the reference potential based on the plurality of intermediate potentials. A capacitance sensor that executes an operation to derive the number of detections corresponding to the number of operations of the switch at that time.
The control circuit is used in the calculation.
A comparison operation for comparing the intermediate potential and the reference potential at a plurality of time points for each switch operation,
An index derivation operation for deriving the number of detections based on a plurality of comparison results obtained by the comparison operation is executed.
The control circuit is used in the index derivation calculation.
Based on the plurality of comparison results, the probability that the intermediate potential exceeds the reference potential is derived, and the plurality of probabilities and the plurality of switch operations obtained at different time points in the period before and after the intermediate potential exceeds the reference potential are obtained. The number of detections is derived based on the continuous function that associates with the number of operations of.
Capacitance sensor. A first capacitor, a second capacitor connected to the first capacitor and whose capacitance changes depending on the presence or absence of an object, a first switch that initializes the first capacitor, the first capacitor, and the second capacitor. A second switch arranged between the two, a third switch for initializing the second capacitor, and a control circuit for controlling the first switch, the second switch, and the third switch are provided.
The control circuit
Switching control in which after the initialization of the first capacitor by the operation of the first switch, the switch operation including the operation of the second switch and the operation of the third switch is performed a plurality of times.
Each time the switch is operated, an intermediate potential that is a potential between the first capacitor and the second capacitor is acquired at a plurality of time points, and the intermediate potential exceeds the reference potential based on the plurality of intermediate potentials. A capacitance sensor that executes an operation to derive the number of detections corresponding to the number of operations of the switch at that time.
The control circuit is used in the calculation.
A comparison operation for comparing the intermediate potential and the reference potential at a plurality of time points for each switch operation,
An index derivation operation for deriving the number of detections based on a plurality of comparison results obtained by the comparison operation is executed.
The control circuit executes the index derivation operation after the time when the intermediate potential exceeds a predetermined potential set between the initial potential of the intermediate potential and the reference potential.
Capacitance sensor. A first capacitor, a second capacitor connected to the first capacitor and whose capacitance changes depending on the presence or absence of an object, a first switch that initializes the first capacitor, the first capacitor, and the second capacitor. A second switch arranged between the two, a third switch for initializing the second capacitor, and a control circuit for controlling the first switch, the second switch, and the third switch are provided.
The control circuit
Switching control in which after the initialization of the first capacitor by the operation of the first switch, the switch operation including the operation of the second switch and the operation of the third switch is performed a plurality of times.
Each time the switch is operated, an intermediate potential that is a potential between the first capacitor and the second capacitor is acquired at a plurality of time points, and the intermediate potential exceeds the reference potential based on the plurality of intermediate potentials. A capacitance sensor that executes an operation to derive the number of detections corresponding to the number of operations of the switch at that time.
The control circuit is used in the calculation.
An average value calculation for deriving an average value of the intermediate potential based on the intermediate potential obtained at a plurality of time points for each switch operation, and
An index derivation operation for deriving the number of detections based on the average value of the intermediate potential is executed.
Capacitance sensor. The control circuit is used in the index derivation calculation.
The capacitance sensor according to claim 5 , wherein the number of operations of the switch at the time when the average value of the intermediate potential exceeds the reference potential is the number of detections. The control circuit is used in the index derivation calculation.
The number of detections is derived based on a function that associates the average value of the plurality of intermediate potentials obtained at different time points in the period before the intermediate potential exceeds the reference potential with the number of operations of the plurality of switch operations. The capacitance sensor according to claim 5 . The control circuit is used in the index derivation calculation.
The number of detections is derived based on a continuous function that associates the average value of the plurality of intermediate potentials obtained at different time points in the period before and after the intermediate potential exceeds the reference potential with the number of operations of the plurality of switch operations. The capacitance sensor according to claim 5 . The control circuit executes the index derivation operation after the time when the intermediate potential exceeds a predetermined potential set between the initial potential of the intermediate potential and the reference potential, according to claims 5 to 8 . The capacitance sensor according to any one item. A first capacitor, a second capacitor connected to the first capacitor and whose capacitance changes depending on the presence or absence of an object, a first switch that initializes the first capacitor, the first capacitor, and the second capacitor. A second switch arranged between the two, a third switch for initializing the second capacitor, and a control circuit for controlling the first switch, the second switch, and the third switch are provided.
The control circuit
Switching control in which after the initialization of the first capacitor by the operation of the first switch, the switch operation including the operation of the second switch and the operation of the third switch is performed a plurality of times.
Each time the switch is operated, an intermediate potential that is a potential between the first capacitor and the second capacitor is acquired at a plurality of time points, and the intermediate potential exceeds the reference potential based on the plurality of intermediate potentials. A capacitance sensor that executes an operation to derive the number of detections corresponding to the number of operations of the switch at that time.
Noise that follows a normal distribution is input to at least one electrode of the first capacitor.
Capacitance sensor.

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