KR101817965B1 - Capacitance detecting means, method related AC power - Google Patents

Abstract

The present invention relates to a new type of AC power supply which detects a sensor capacitance based on a charge sharing phenomenon caused by a voltage difference applied to a sensor capacitor and an auxiliary capacitor connected to a detection system when an AC voltage applied to the detection system alternates, And a method of detecting the capacitance.
The capacitance detecting means according to the present invention is a detecting means for detecting that a sensor capacitance CS is generated by an approach of an object 18 and includes a sensor for forming a sensor capacitor cs with the object 18 (14); An auxiliary capacitor caux connected at one side to the sensor 14 and at the other side to the system ground GND1; A switching element 10 for interrupting charging of the sensor capacitor cs and the auxiliary capacitor caux; And the sensor (14), when the sensor capacitor (cs) is formed between the sensor (14) and the object (18) connected to the external ground (VG) And a signal detector (22) for detecting a voltage generated in the voltage detector (14).
According to the present invention, since the sensitivity of the signal detected by the detection system is improved, there is an effect of stably obtaining the size or amount of change of the sensor capacitance.

Description

[0001] Capacitance detecting means and method related AC power [

The present invention relates to a means and a method for detecting the size or capacitance of a capacitor and, more particularly, to a method and apparatus for detecting the magnitude or amount of capacitance of a capacitor, Means for detecting a magnitude or a change amount of capacitance based on a charge sharing phenomenon occurring with a change in a voltage occurring due to charging and discharging of charge and mutually generated with an auxiliary capacitor connected to the same point as the measured capacitor; will be.

When there is a material having a permittivity between two conductors, if a voltage or an electric current is applied to both ends of the two conductors, a capacitor is formed to generate a capacitance which is an ability to accumulate the charge, The dielectric constant of the dielectric between the two conductors and the opposing area and the opposing distance of the two conductors.

Commercial capacitors made using this principle have various types such as ceramic capacitors, electrolytic capacitors, and Mylar capacitors.

The capacitance of these commercial capacitors typically has a size of 1 pF (Pico Farad), 1 nF (Nano Farad), or 1 uF (Micro Farad) or more and it is possible to easily measure the capacitance with a meter such as a multimeter.

However, when the capacitance is less than 1 pF (Pico Farad), accurate measurement can not be performed due to meter error when measuring with a simple meter such as a multimeter, and conditions under which measurement can not be performed using a meter, Sometimes it is not possible to measure the capacitance with a meter, such as when trying to measure the magnitude of the capacitance formed between buttons.

In this case, it is possible to indirectly measure the capacitance, and Figure 1 shows an example of such a method.

1, the uncharged capacitor c1 is connected to the point P1 of the capacitance detection system, ignoring the magnitude of the capacitance, as in the case of the capacitor formed between the human hand and the elevator button, Thereby to know the magnitude of C1, which is the capacitance of the capacitor c1. The signal detector of FIG. 1 is a detector for detecting the voltage at the point P1. When the voltage of the point P1 is detected by the signal detector of FIG. 1, the magnitude of C1, which is the capacitance of the capacitor c1, can be known by calculation.

When the switch SW of FIG. 1 is turned on and the capacitor c2 is connected to the point P1, the potential Vp1 of the point P1 is determined by the following equation (1): " (1) " do.

≪ Formula 1 >

The capacitance C1 of the capacitor c1 to be known is expressed by Equation (2) below.

&Quot; (2) "

Assuming that the potential of Vp1 in Equation (1) detected by the signal detecting unit in Fig. 1 is 5V, C2 is 1pF, and V1 is 10V, it is understood that the size of C1 is 1pF through calculation of Equation (2). Therefore, when the capacitance detection system as shown in FIG. 1 is constructed, the magnitude of the capacitance can be determined without using a meter.

When a system for detecting the capacitance, such as the embodiment of FIG. 1, is applied to a detection system that detects a change in distance between two objects, i.e., a displacement, the magnitude of the capacitance can be detected and the displacement can be detected using the detected capacitance It is also possible.

Fig. 2 shows an example of a sensor for detecting a displacement, wherein two pistons face each other at a certain distance in a plastic, glass, or imaginary cylinder. Referring to Fig. 2, two pistons having the same area of "S" inside the cylinder are initially opposed at a distance "d1 ". D1-d2 ", which is the moving distance of the upper piston when the upper piston is close to the lower piston and the upper and lower piston distances are changed to "d2 " by applying a force to the upper piston, .

2, the capacitance CVR of the capacitor c4 formed at both ends of the piston, when filled with a material having a permittivity of "? 1 " between the pistons of Fig. 2 and an opposite area "S" Respectively.

&Quot; (3) "

Quot; d1 "and a known opposing area" S "and a known permittivity" epsilon 1 "are substituted into Equation (3), the capacitance" CVR1 ", which is the magnitude of the capacitance formed between the two pistons in Fig. 2, ". Further, "CVR2" produced by arbitrary "d2" can be extracted through the calculation of the capacitance detection system of FIG. 1 and the calculations of Equation 1 and Equation 2, and substituting this into Equation 3 yields "d2" The moving distance of the upper piston of Fig. 2 can be known by the calculation of "d1-d2 ".

3 is an embodiment of a capacitance detection system in which the capacitance detection system illustrated in FIG. 1 is further embodied. Referring to FIG. 3, one side of the capacitor c4 generated by the configuration of FIG. 2 is connected to the point P2 of FIG. 3, and the other side of the capacitor c4 is connected to the ground of the system of FIG. c2 and c3 are parasitic capacitors generated in the detection system of Fig. For example, c2 is a layout in which the signal detecting portion of Fig. 3 is built in the IC and the wiring of the point P2 reaching the input terminal of the switching element SW1 and the signal detecting portion is wired or crossed at a small interval with any signal line in the IC And c3 may be a model of a parasitic capacitor formed between the gate of the circuit element constituting the signal detecting unit of FIG. 3 and the system ground. Such parasitic capacitors are not limited, and are distributed in various ways according to the configuration of the detection system.

When the switch SW1 is turned on with the switch SW2 in Fig. 3 turned off and a charging voltage of "Vchg" is supplied to the point P2, the capacitors connected to P2, that is, c2 / c3 / c4 Quot; Vchg "and capacitor c1 is not affected by" Vchg "if it is disconnected from P2 due to off of switch" SW2 " (the lower case c2 / c3 / c4 is a capacitor and the upper case C1 / C2 / C3 / C4 is the capacitance of each capacitor). 3 is connected to the point "P2 ", the potential" Vp2 "detected by the signal detecting portion of Fig. 3 is expressed by Equation 4 and Equation same.

≪ Equation 4 &

In Equation (4), Vp2 can be detected by the signal detector of FIG. 3, and the size can be known. If both V2 and Vchg and C1 / C2 / C3 are known, the CVR size can be extracted through calculation. It is also possible to know the size of "d2 " when the CVR is substituted into Equation (3). Therefore, if "d1" is known in advance, "d1-d2 ", which is the amount of displacement of the upper piston in Fig.

However, in a system having such a modeling, detecting the CVR variation according to the displacement of the upper piston in Fig. 2 has some problems.

For example, Vp2 = 4.2258V, assuming that C1 = C2 = C3 = 10pF, CVR = 1pF, Vchg = 1V, and V2 = 10V in Equation 4. When the CVR changes from 1 pF to 0.9 pF by 0.1 pF due to the displacement of the upper piston in Fig. 2, Vp2 detected by the signal detecting portion of Fig. 3 is 4.2362 V, so that the variation amount of Vp2 when the CVR changes by 0.1 pF is 4.2362-4.2258 = 0.0104 V , That is, 10.4 mV. An ADC for converting an analog value, which is a voltage detected by the signal detecting unit, into a digital signal is used in the signal detecting unit of FIG. Since the detected Vp2 is near 4.2V, the ADC of the signal detecting unit for detecting the magnitude of Vp2 sets the detection band to about 3.5V to 4.5V. Assuming that a 10-bit ADC is used for the detector, the resolution of the ADC is "1V / 1024bit", and the resolution per bit is about 1mV, since a 10-bit ADC needs to detect 4.5V-3.5V, or 1V. Therefore, when the signal variation of the displacement sensor shown in FIG. 2 is 10.4 mV, only about 1% of the performance of a 10-bit ADC having a resolution of 1024 bits is used.

Generally, a signal-to-noise ratio (SNR) of 1% in a system corresponds to a good system, and noise generally exceeds a few percent of a signal. Therefore, if the magnitude of the detected signal is only about 1%, it is difficult to distinguish between the signal and noise when the noise is a few percent, so that the detected signal is unreliable.

Therefore, there arises a problem that when the magnitude of the capacitance CVR detected in such a system is small, the detected signal is unreliable.

The present invention has been proposed in order to solve the problem of a system for detecting the capacitance of a conventional capacitor as described above. The present invention applies AC power to a system power source used in a detection system for detecting a capacitance, Charge sharing occurs with the capacitors connected to the capacitor to be detected and the capacitor to be detected due to the change in the voltage applied to the detection capacitor and the difference in voltage based on the charge sharing is detected to detect the magnitude of the capacitance of the capacitor to be detected and the capacitance variation And a detection method and a detection method for extracting the information.

A sensing means for sensing that a sensor capacitance (CS) is generated by an approach of an object (18), the sensing means comprising: a sensor (14) forming a sensor capacitor (cs) with the object (18); An auxiliary capacitor caux connected at one side to the sensor 14 and at the other side to the system ground GND1; A switching element 10 for interrupting charging of the sensor capacitor cs and the auxiliary capacitor caux; And the sensor (14), when the sensor capacitor (cs) is formed between the sensor (14) and the object (18) connected to the external ground (VG) And a signal detecting unit 22 for detecting a voltage generated in the voltage detecting unit 14.

According to one embodiment, the system power supply is composed of a positive system power supply (Vsupply) and the system ground (GND1), and the positive system power supply (Vsupply) is connected to the system ground (GND1) Voltage.

According to another embodiment, the positive system power supply (Vsupply) and the system ground (GND1) are in an in-phase (Same Phase) and are an AC voltage alternating with respect to the ground ground.

According to another embodiment, the AC voltage includes a DC region at an inflection point at which the magnitude of the AC voltage varies.

According to another embodiment, the capacitor connected to the sensor 14 and the sensor 14 is charged in the DC region or the calculated result in the detection system 20 is outputted to the outside.

According to another embodiment, when the calculation result of the detection system 20 is outputted to the outside, the system ground GDN1 and the external ground are interconnected.

According to another embodiment, the voltage detected by the sensor 14 based on the magnitude of the system power applied to the detection system is based on the charge sharing phenomenon of the auxiliary capacitor caux and the sensor capacitor cs The size changes.

According to another embodiment, the auxiliary capacitor (caux) supplies the charge required by the sensor capacitor (cs) or charges the charge discharged from the sensor capacitor when the charge sharing phenomenon occurs.

According to another embodiment, the auxiliary capacitor caux is a storage capacitor cst.

According to yet another embodiment, the storage capacitor (cst) is formed inside the detection system (20).

According to another embodiment, the auxiliary capacitor caux is a floating capacitor cp.

According to another embodiment, the floating capacitor is an equivalent capacitor of all the floating capacitors observed at the input of the signal detecting section 22. [

According to another embodiment, the external ground (VG) is not affected by the size change of the system power source.

According to another embodiment, the external ground VG is a ground ground.

According to another embodiment, the external ground VG is a DC voltage.

According to another embodiment, the external ground VG is not affected by the AC voltage applied to the system.

According to another embodiment, the voltage at the input of the signal detector 22 is changed in size in synchronism with the change in the magnitude of the system power applied to the detection system 20.

According to another embodiment, the signal detecting unit 22 detects the voltage at the sensor 14 based on the system power source applied to the detection system 20 when the sensor capacitor cs is not generated, The voltage at the sensor 14 is detected when the sensor capacitor cs is added to the sensor 14 and the voltage difference between the object 18 and the sensor 14 Extract the distance or facing area.

According to still another embodiment, the voltage detected by the signal detecting unit 22 when the sensor 14 is charged with the charging voltage Vchg and the sensor capacitor cs is not generated is determined by the following Equation 1 The sensor 14 is charged to the charge voltage Vchg when the object 18 approaches the sensor 14 and the sensor capacitor cs is added and the voltage detected by the signal detection unit 22 is Is determined by Equation (2), and the voltage difference is generated by the difference between Equation (1) and Equation (2).

≪ Formula 1 >

&Quot; (2) "

(Where Vp is the magnitude of the voltage detected by the sensor 14, Vsupply is the magnitude of the alternating voltage of the system power supply, Vchg is the charging voltage with respect to the ground, and CAUX is the capacitance of the auxiliary capacitor caux And CS is the capacitance of the sensing capacitor cs generated between the sensor 14 and the object 18)

According to another embodiment, when a plurality of sensor capacitance (CSn) formed between a plurality of objects and a plurality of sensors 14 is added to the input of the signal detection unit 22 when the object 18 is a plurality, The voltage detected by the signal detecting unit 22 after the sensor is charged with the charging voltage Vchg is determined by the following Equation (3).

&Quot; (3) "

(Where Vp is the magnitude of the voltage detected by the sensor 14, Vsupply is the magnitude of the alternating voltage of the system power supply, Vchg is the charging voltage with respect to the ground, and CAUX is the capacitance of the auxiliary capacitor caux CS is the capacitance of the sensing capacitor cs occurring between the sensor 14 and the object 18 and n is the number of sensor capacitors)

According to another embodiment, based on the difference caused by the time difference of the voltage (Vp) detected by the signal detecting unit 22 by one or a plurality of static objects and one dynamic object 18, The amount of capacitance change caused by the time difference of the sensing capacitance CS formed between the object and the opposing sensor 14 is extracted.

According to another embodiment, the input terminal of the signal detector 22 at the time of detecting the voltage of the sensor 14 is in a high impedance state of at least 1 M ?.

According to another embodiment, the signal detection section 22 includes an ADC.

According to another embodiment, the capacitance of all the capacitors connected to the input of the signal detector 22 is located at the denominator of the "under-swing element ".

According to another embodiment, the capacitance of the fixed capacitor whose other end is connected to the system ground GND1 is located at the denominator of the "under-swing element ", of all the capacitors connected to the input terminal of the signal detector 22.

According to another embodiment, the capacitance of the variable capacitor whose other end is connected to the external ground (VG) is located in the molecule of the "under-swing element ".

According to another embodiment, the fixed capacitor maintains the initial charge amount even when the magnitude of the system power applied to the detection system 20 is changed.

According to another embodiment, the variable capacitor accumulates more charge when the system power applied to the detection system 20 is larger than the external ground potential, and the system power applied to the detection system 20 And discharges the accumulated charges when the external ground potential becomes smaller than the reference potential.

According to another embodiment, the fixed capacitor supplies the charge when the variable capacitor is capable of accumulating more charge, and stores it when the accumulated charge of the variable capacitor discharges.

According to yet another embodiment, a change in the magnitude of the system power applied to the detection system 20 is made in synchronization with the Up or Down signal of the detection system 20. [

According to another embodiment, sensor capacitances (CS) are formed on two faces constituting one sensor (14) connected to one sensor signal line (16), opposing to different objects (18).

A method of detecting the occurrence of a sensor capacitance (CS) by an approach of an object (18) comprising the steps of: (a) contacting the object (18) and the sensor (14) connected to the external ground (VG) Adding a formed sensor capacitor cs; (b) applying a charging voltage (Vchg) to an auxiliary capacitor (caux) having one side commonly connected to the sensor (14) and the other side connected to the system ground (VG); (c) a step of applying an alternating system power to the detection system 20 to which the sensor 14 is connected and detecting the voltage of the sensor capacitor 14 by the signal detection unit 22 .

According to one embodiment, the system power supply is composed of a positive system power supply (Vsupply) and the system ground (GND1), and the positive system power supply (Vsupply) is connected to the system ground (GND1) Voltage.

According to another embodiment, the positive system power supply (Vsupply) and the system ground (GND1) are in an in-phase (Same Phase) and are an AC voltage alternating with respect to the ground ground.

According to another embodiment, the AC voltage includes a DC region at an inflection point at which the magnitude of the AC voltage varies.

According to another embodiment, the capacitor connected to the sensor 14 and the sensor 14 is charged in the DC region or the calculated result in the detection system 20 is outputted to the outside.

According to another embodiment, when the calculation result of the detection system 20 is outputted to the outside, the system ground GDN1 and the external ground are interconnected.

According to another embodiment, the voltage detected by the sensor 14 based on the magnitude of the system power applied to the detection system is based on the charge sharing phenomenon of the auxiliary capacitor caux and the sensor capacitor cs The size changes.

According to another embodiment, the auxiliary capacitor (caux) supplies the charge required by the sensor capacitor (cs) or charges the charge discharged from the sensor capacitor when the charge sharing phenomenon occurs.

According to another embodiment, the auxiliary capacitor caux is a storage capacitor cst.

According to yet another embodiment, the storage capacitor (cst) is formed inside the detection system (20).

According to another embodiment, the auxiliary capacitor caux is a floating capacitor cp.

According to another embodiment, the floating capacitor is an equivalent capacitor of all the floating capacitors observed at the input of the signal detecting section 22. [

According to another embodiment, the external ground (VG) is not affected by the size change of the system power source.

According to another embodiment, the external ground VG is a ground ground.

According to another embodiment, the external ground VG is a DC voltage.

According to another embodiment, the external ground VG is an AC voltage which is not affected by the AC voltage applied to the system.

According to another embodiment, the voltage at the input of the signal detector 22 is changed in size in synchronism with the change in the magnitude of the system power applied to the detection system 20.

According to another embodiment, the signal detecting unit 22 detects the voltage at the sensor 14 based on the system power source applied to the detection system 20 when the sensor capacitor cs is not generated, The voltage at the sensor 14 is detected when the sensor capacitor cs is added to the sensor 14 and the voltage difference between the object 18 and the sensor 14 Extract the distance or facing area.

According to another embodiment, the voltage detected by the signal detecting unit 22 when the sensor 14 is charged with the charging voltage Vchg and the sensor capacitor cs is not generated is determined by the following Equation 4: The sensor 14 is charged to the charge voltage Vchg when the object 18 approaches the sensor 14 and the sensor capacitor cs is added and the voltage detected by the signal detection unit 22 is Is determined by Equation (5), and the voltage difference is generated by the difference between Equation (4) and Equation (5).

≪ Equation 4 &

≪ Eq. 5 &

(Where Vp is the magnitude of the voltage detected by the sensor 14, Vsupply is the magnitude of the alternating voltage of the system power supply, Vchg is the charging voltage with respect to the ground, and CAUX is the capacitance of the auxiliary capacitor caux And CS is the capacitance of the sensing capacitor cs generated between the sensor 14 and the object 18)

According to another embodiment, when a plurality of sensor capacitance (CSn) formed between a plurality of objects and a plurality of sensors 14 is added to the input of the signal detection unit 22 when the object 18 is a plurality, The voltage detected by the signal detecting unit 22 after the sensor is charged with the charging voltage Vchg is determined by the following Equation (6).

&Quot; (6) "

(Where Vp is the magnitude of the voltage detected by the sensor 14, Vsupply is the magnitude of the alternating voltage of the system power supply, Vchg is the charging voltage with respect to the ground, and CAUX is the capacitance of the auxiliary capacitor caux CS is the capacitance of the sensing capacitor cs occurring between the sensor 14 and the object 18 and n is the number of sensor capacitors)

According to another embodiment, based on the difference caused by the time difference of the voltage (Vp) detected by the signal detecting unit 22 by one or a plurality of static objects and one dynamic object 18, The amount of change caused by the time difference of the sensing capacitance CS formed between the object and the opposing sensor 14 is extracted.

According to another embodiment, the input terminal of the signal detector 22 at the time of detecting the voltage of the sensor 14 is in a high impedance state of at least 1 M ?.

According to another embodiment, the signal detection section 22 includes an ADC.

According to another embodiment, the capacitance of all the capacitors connected to the input of the signal detector 22 is located at the denominator of the "under-swing element ".

According to another embodiment, the capacitance of the fixed capacitor whose other end is connected to the system ground GND1 is located at the denominator of the "under-swing element ", of all the capacitors connected to the input terminal of the signal detector 22.

According to another embodiment, the capacitance of the variable capacitor whose other end is connected to the external ground (VG) is located in the molecule of the "under-swing element ".

According to another embodiment, the fixed capacitor maintains the initial charge amount even when the magnitude of the system power applied to the detection system 20 is changed.

According to another embodiment, the variable capacitor accumulates more charge when the system power applied to the detection system 20 is larger than the external ground potential, and the system power applied to the detection system 20 And discharges the accumulated charges when the external ground potential becomes smaller than the reference potential.

According to another embodiment, the fixed capacitor supplies the charge when the variable capacitor is capable of accumulating more charge, and stores it when the accumulated charge of the variable capacitor discharges.

According to another embodiment, a change in the magnitude of the system power applied to the detection system 20 is made in synchronization with the Up or Down signal of the detection system 20. [

According to another embodiment, sensor capacitances (CS) are formed on two faces constituting one sensor 14 connected to one sensor signal line 16, opposite to each other.

According to the capacitance detecting means and the detecting method interlocked with the AC power supply of the present invention, when the magnitude of the system power applied to the capacitance detecting system is changed, the magnitude of the capacitance or the magnitude of the voltage applied to the detected capacitor There is an effect that it is possible to detect the magnitude of the capacitance or the amount of capacitance change by using the phenomenon that a change occurs in the amount of charge accumulated in the detected capacitor and a difference is generated in the voltage detected by the detecting unit according to the change of the amount of charge .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram of an existing embodiment for indirectly measuring capacitance; FIG.
Fig. 2 shows an example of a sensor for detecting displacement
FIG. 3 is a circuit diagram of a more specific embodiment of the capacitance detection system illustrated in FIG. 1
Fig. 4 shows an embodiment of a displacement sensor composed of two pistons
5 is a circuit diagram showing a basic structure of a capacitance detection system according to the present invention.
6 is a circuit diagram of an embodiment of a circuit for detecting the sensor capacitance of the present invention
7 is a diagram of an alternating voltage with regularly alternating magnitude and phase
Figure 8 is a plot of alternating voltage with irregularly alternating magnitude and phase;
Fig. 9 is a diagram showing an example in which a plurality of objects are used in the capacitance detection system of the present invention
10 is a circuit diagram of a detection system in which a plurality of sensor capacitances can be detected

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

The present invention relates to a capacitance detecting means and a detecting method interlocked with an AC power supply. When the distance between two conductors constituting a capacitor changes, or when the capacitance of a capacitor changes due to a change in the area of a facing surface between two conductors, And to a means and a method for easily detecting this.

The present invention detects a capacitance formed between a finger or a conductor (hereinafter referred to as an object) having similar electrical characteristics and a sensor. Here, the term "noncontact input" means that a capacitance is formed in a state where the object and the sensor are separated from each other by a predetermined distance. The object can be brought into contact with the outer surface of the substrate covering the sensor. In this case, however, the object and the sensor remain in a non-contact state. Thus, the contact of the object with respect to the sensor may be expressed in terms of "approach ". On the other hand, since the object may be in contact with the outer surface of the substrate covering the sensor, "approach" and "contact"

In addition, the components such as "to" described below are components that perform certain roles and function as a unit, such as a signal input unit comprising a buffer, or a software or FPGA (Field-Programmable Gate Array) Application Specific Integrated Circuit). Also, "part" may be included in a larger element or "part, " or may include smaller elements and" parts. &Quot; Also, "part" may have its own CPU.

In the following drawings, thicknesses and regions are enlarged to clearly show layers and regions. Like reference numerals are used for like parts throughout the specification. Layer " or " region "is intended to include " on" or " directly on " Conversely, when a part is "directly over" another part, it means that there is no other part in the middle.

Further, the "signal" described in this specification refers to a voltage or a current collectively unless otherwise specified.

Further, in this specification, "Capacitance" refers to the ability to store charge, and "Capacitor" refers to Element with capacitance. In this specification, capacitors are denoted by lower case letters and capacitances are denoted by upper case letters. For example, c1 / C1 means that the capacitance of the capacitor c1 is C1.

The switching element in the present invention may be a relay, a metal oxide semiconductor (MOS) switch, a bipolar junction transistor (BJT), a field effect transistor (MOSFET), a metal oxide semiconductor field effect transistor An Insulated Gate Bipolar Transistor (TFT), a TFT (Thin Film Transistor), and an OPAMP, and may be formed by a combination of the same species or different species. The switching device can be any device that can turn on and off the input / output by means that can turn input / output on / off regardless of the number of input / output terminals.

On the other hand, as an example of a switching element, a CMOS switch is formed by mutual combination of a PMOS and an NMOS, and input / output terminals are connected to each other. However, the on / off control terminals exist separately and are connected to the same control signal, So that the on / off state is determined. Relay is a device in which the voltage or current applied to the input terminal is output without loss when a current is applied to the control terminal. The BJT is a device in which a voltage higher than the threshold voltage of the base is applied to the base , A certain amount of amplified current flows from the collector to the emitter. The TFT is a switching element used in a pixel portion constituting a display device such as an LCD or an AMOLED, and is constituted by a gate terminal serving as a control terminal, a source terminal serving as an input terminal, and a drain terminal serving as an output terminal When a voltage that is higher than the threshold voltage by a voltage applied to the drain terminal is applied to the gate terminal, a current that depends on the magnitude of the voltage applied to the gate terminal as it is conducted flows from the input terminal to the output terminal.

The term "forcing a signal" in this specification means that a level of a signal that has already been maintained is changed, or a signal is connected to a signal in the current floating state It means. For example, the signal applied to the on / off control terminal of the switching element may be used to mean that the existing low level voltage is changed to a high level, Can be used to mean that a certain voltage is applied to turn on / off the switching element to the on / off control terminal of the switching element of FIG.

Also, the present invention detects the magnitude of a capacitance or the amount of change in capacitance formed between a sensor and a conductor, and the magnitude and the capacitance of the capacitance are used in the same sense. A capacitor for detecting the magnitude of the capacitance or the amount of change in the capacitance is referred to as "detected capacitor ".

The detection system used herein may be an IC that is an integrated circuit, or a "circuit" or a portion of an IC or a "circuit", where the various circuit components are interconnected at the PCB. For example, the fact that the AC power is applied to the detection system means that the AC power is applied to the entire IC or the entire circuit, or the AC power is applied to only a part of the IC or a part of the circuit.

Also, in this specification, ground or absolute ground is a ground potential of 0 (zero) V, and earth ground, absolute ground and ground potential are used in the same meaning.

The detection system is supplied with power based on its own ground potential of the detection system, and is collectively referred to as the system power supply. In addition, the system power is separated into positive system power and system ground, and positive system power is the voltage supplied to the detection system based on the system ground.

All voltages and potentials are sized based on the ground potential unless otherwise specified herein. For example, if the positive system power is 20V, the size is 20V based on the ground potential. If the positive system power is 5V relative to the system ground, the potential difference between the positive system power and the system ground is 5V .

In this specification, a voltage and a potential are used in the same sense, and a voltage having a specific magnitude is expressed as a potential.

Also, the system power supplied to the detection system is an internal power supply. Therefore, all power sources other than the internal power source are referred to as external power sources or external potential sources. The ground ground is also an external potential.

The AC voltage applied to the detection system of the present invention can be made using a battery. Since the ground of the battery is a floating ground, the AC voltage of the present invention made of a battery can not define an absolute magnitude based on the ground potential unless the ground of the battery and the ground are interconnected. Therefore, to refer to the absolute magnitude of the AC voltage generated using a floating ground such as a battery, it is assumed that the floating ground, such as ground, ground potential and battery ground, is grounded based on ground potential.

In this specification, the potential at the point P, the potential detected at the sensor 14, or the potential detected at the signal detecting section 22 or the potential at the input terminal of the buffer 15 have the same meaning.

In this specification, Vsupply or VG, which is a symbol representing the magnitude of a voltage, is also used as a symbol indicating a magnitude of a voltage or a specific voltage. For example, Vsupply is a symbol representing positive system power and is used as the magnitude of the voltage representing an alternating voltage of 20V.

Before explaining a specific embodiment of the present invention, the principle of detecting capacitance will be briefly described with reference to Fig. 4, which is an embodiment of a displacement sensor composed of two pistons. Fig. 4 is a cylinder made of glass or plastic or composed of two opposed pistons inside a virtual body. In practical use, the shape of the piston is not limited and has various geometric shapes. For example, the piston may be circular, square, or various polygons. Opposing pistons may have the same geometric shape but different geometric shapes. In this respect, the body supporting the two pistons is a virtual body, and the piston on the upper side of the cylinder or the piston on the lower side may be displaced by the force externally applied, or by their own energy, or their opposite areas may be changed.

Between the two pistons is filled with a material having a predetermined permittivity. For example, the dielectric constant of air is 1 and the glass has a dielectric constant of 5 or 6. In addition, a predetermined voltage may be applied to each of the two pistons. In the embodiment of FIG. 4, a voltage of Vf is applied to the piston at the upper end, and 0 (zero) V is applied to the piston at the lower end.

As in the embodiment of FIG. 4, an attempt to detect the displacement of two pistons, made up of two pistons and using a change in capacitance formed between the two pistons, is a good embodiment of the present invention. Alternatively, an elevator system for driving an elevator on the basis of a distance between a finger and a button by detecting a capacitance of a capacitor formed between a button and a finger of a person by approaching a finger of the person to the button of the electronic elevator It is another embodiment of the invention.

Referring to FIG. 4, which is an embodiment of the present invention, two conductors face an opposite area "S" and an opposite distance "d", and a dielectric with a dielectric constant of "epsilon" is filled between the two conductors. 4, a capacitor is formed between the two conductors, and the formed capacitor has the capacitance C defined in the right-hand expression of FIG.

When a voltage or current is supplied to two conductors having a capacitance "C", the capacitors accumulate charges according to the relation V = Q / C. Where V is the magnitude of the voltage applied to the capacitor, C is the generated capacitance, and Q is the amount of charge stored in the capacitor.

Referring to the expression "V = Q / C ", a change in the voltage applied to the capacitor changes the amount of charge stored in the capacitor having the same capacitance, or even if the voltage applied to the capacitor is the same, A difference occurs in the amount of charge stored in the capacitor.

This principle is applied to FIG. 4 as follows. When the distance of the mutually opposing pistons in Fig. 4 is kept constant, the amount of charge accumulated in the capacitor formed between the opposing pistons increases as the magnitude of the voltage Vf applied to one side of the piston increases, When the distance between the two pistons is narrowed, the capacitance detected in FIG. 4 becomes large, so that the amount of charge accumulated between the pistons by the same applied voltage Vf will increase.

At this time, a ground for moving the current is connected to the piston opposed to the piston to which the voltage Vf is applied. The ground is either a zero V potential or a DC voltage such as 1V or 100V, or an AC voltage whose magnitude and phase vary.

5 is a circuit diagram showing a basic structure of a capacitance detection system according to the present invention. 5, there is shown a basic structure composed of a switching element 10, a sensor 14, a sensor signal line 16, a storage capacitor cst, a floating capacitor cp and a high impedance input element 12 .

The switching element 10 is turned on when a high voltage Von is applied to the switch on / off control terminal 10-3 so that the charging voltage Von connected to the switch input terminal 10-1 Vchg to the switch output terminal 10-2 and applies a charging voltage to the sensor 14 and all the capacitors connected thereto for a predetermined time to charge them to the magnitude of "Vchg". When charging is completed, a low Voff voltage is applied to the switch on / off control terminal 10-3 to turn off the switching device 10, thereby charging the capacitor connected to the P point The charging voltage Vchg is removed and the point P maintains the charging voltage. It is assumed that there is a resistive component of a predetermined magnitude in the path from the switching element 10 to the capacitor connected to the point P and the path to the high impedance input element 12 and thus the charging time is delayed but there is no resistance component in this specification .

In the present invention, a high impedance input element 12 should be used to detect the potential of the P point. Hi Impedance (Hi-z) The input terminal 12 uses a gate terminal such as a buffer, an operational amplifier (OPAMP), or a MOS / FET. In the following description, the Hi-z input element 12 is mixed with the buffer 15. The buffer 15 and the Hi-z input element 12 are elements constituting the signal detecting unit 22 and should be shown inside the signal detecting unit 22 in Fig. 6. In order to emphasize that the Hi-z input is shown in Fig. 6 The signal detecting unit 22 and the buffer 15 are shown separately.

When the switching device 10 is turned off after the point P is charged with the charging voltage Vchg, the discharging of the capacitors connected to the point P in FIG. 5 starts, and in order to minimize the discharge, The buffer 15 is preferably in the Hi-z state. The impedance of the input element in the Hi-z state is at least 1 M OMEGA. The OFF state impedance of the switching element 10 detected at the point P is also at least 1 M OMEGA.

The signal detecting unit 22 detects the voltage at the point P to calculate the capacitance formed between the sensor 14 and the object 18 by the charge sharing phenomenon which will be described later. After the calculation is completed or the calculation is completed, the point P is again set to Vchg And the process of detecting the voltage at the point P based on the charge sharing phenomenon is repeated.

cst is a storage capacitor, which serves to supply charge to the sensor capacitor cs of FIG. 5 or to charge the charge discharged by the sensor capacitor cs. The storage capacitor cst may be built into the detection system 20 to be described later or may be attached to the outside of the detection system.

cp is a parasitic capacitor, which is the sum of all the floating capacitors observed at the point P in Fig. 5, that is, an equivalent capacitor. For example, although not shown, there is also a floating capacitor between the output terminal 10-2 of the switching element 10 and the switch on / off control terminal 10-3, There is also a floating capacitor in the input stage. Also, when a plurality of sensors 14 are used, if a plurality of sensor signal lines 16 are arranged adjacent to each other, there is a floating capacitor between them.

In the detection system 20, since cst is absolutely necessary, cst can be formed in the detection system 20, or cp that is formed naturally can serve as a storage capacitor. Referring to cst and cp in FIG. 5, they are connected to the point P and connected to the same ground. Thus, due to the simple circuit knowledge, cst and cp can be composed of one equivalent circuit, which is then referred to as an auxiliary capacitor (caux) and an auxiliary capacitance (CAUX). The auxiliary capacitor caux serves to supply electric charge to the variable capacitor to be described later in the charge sharing phenomenon to be described later or to accumulate the electric charge emitted by the variable capacitor.

cs has a capacitance of the size of "CS " as a sensor capacitor formed through the sensor 14 and the object 18 and the dielectric between them. The object 18 may be a finger that touches a key of an elevator. Since the size of a finger is different for each person and a change occurs in the opposing area and the opposing distance according to the change of time, the magnitude of the sensor capacitance varies from time to time .

In the present invention, an external power source other than the system power source is used as the ground for the object 18, and the external power source is directly connected to the object 18 as a ground connected to the lower cylinder of FIG. 4, It can be virtually linked with the object 18 as virtually linked. In this specification, an external power source connected to the object 18 through the ground is also referred to as an external ground, and is represented as a virtual ground (VG).

The virtual ground (VG) is the earth ground or the DC voltage or AC voltage relative to the ground. For example, when a person holds a 3-wavelength fluorescent lamp with one hand and presses the elevator key with the other hand, the VG will be the AC voltage output from the 3-wavelength fluorescent lamp. The virtual ground (VG) may be a floating ground such as a battery ground. When a floating ground is used, all voltages of the detection system are sized relative to the floating ground. In this specification, ground ground includes a floating ground and is also used in the same sense.

6 shows an embodiment of a circuit for detecting the sensor capacitance of the present invention, and a method of detecting the capacitance CS of the sensor capacitor cs with reference to FIG. 6 will be described below. The portion surrounded by the ellipse in Fig. 6 is the detection system 20. The detection system 20 includes a signal detection unit 22, and may generate an AC voltage as a system power or may include a CPU. The system power may be generated by the detection system 20 or may be supplied from the outside.

AC power used for detecting the sensor capacitance CS of the sensor capacitor cs in the detection system 20 is referred to as a system power supply or system voltage and the system power supply is connected to positive system power supply Vsupply and system ground GND1 Consists of.

The positive system power supply, Vsupply, is a DC voltage based on GND1, which is the system ground. For example, Vsupply is 3.3V DC voltage relative to GND1.

Although Vsupply is a DC voltage based on GND1, Vsupply is an AC voltage whose magnitude and phase change with respect to the ground level. For example, Vsupply may be 10V or 10V lower in a predetermined period based on the ground level. Or at some point it may rise and fall to 15V, or at some point rise or fall to 20V. In the present specification, it is assumed that the system power source is swung up or down to a predetermined voltage.

Also, the AC voltage used as the system voltage can be varied in phase, such as up or down 10V to 10uS and up or down 10V to 20uS in one embodiment.

Since Vsuppy and GND1 are DC voltage that maintains a voltage difference of a certain size and Vsupply is AC voltage whose size and phase change with respect to the ground ground, GND1 is an AC voltage whose magnitude and phase change with respect to the ground ground like Vsupply.

Since the system power source used in the detection system 20 is an AC power source based on the ground ground but is a DC voltage based on GND1, the system power is used as the voltage for the calculation of the signal detection unit 22 of the detection system 20 It is possible to do.

In order to output a value calculated by the signal detector 22 to the outside, the system ground GND1 and the ground of the external structure receiving the signal are preferably connected to each other. At this time, it is preferable that the AC voltage applied to the signal detection unit 22 maintains the waveform of the DC voltage which does not alternate. This is the time t1 or the time t2 in FIG. 8, and the AC voltage includes a DC region maintaining a constant magnitude for a predetermined time at the alternate inflection point. The DC region included in the AC voltage is a region required to secure a charge time to be described later or to transmit a signal of the signal detection unit to the outside. For example, at time t2 of FIG. 8A, the signal detector 22 completes an operation and outputs 25V to the outside (not shown). The GND1 is connected to the earth ground or the upper system including the detection system 20 And the upper system may have a floating ground in which a DC battery is used.

The external meaning based on the signal detection unit 22 may be the external of the PCB including the IC 22 including the signal detection unit 22 and the signal detection unit 22, But may be another region except for the detection unit 22. [ For example, when the signal detecting portion 22 in the IC and the driving portion for driving the piston in Fig. 4 exist in different regions and the ground of the driving portion and the system ground GND1 used in the signal detecting portion 22 are different from each other, The driving unit existing in the driving unit can be represented externally.

The auxiliary capacitor caux in Fig. 6 is an equivalent capacitor of the storage capacitor cst and the floating capacitor cp. The sensor capacitor cs is a capacitor formed between the sensor 14 and the object 18 in Fig. 5, and the capacitance is CS.

The sensor 14 may be connected to the sensor signal line 16 to be spaced apart from the detection system 20. When a plurality of detection systems 20 are used, a plurality of sensors 14 may be arranged at a predetermined distance apart, and when the sensor signal lines 16 connected to the sensor 14 are adjacent to each other, The capacitor cp is generated and the floating capacitance is included in the auxiliary capacitance CAUX of Fig.

 In the present invention, system power is applied to the switching element 10, the buffer 15, or the signal detection unit 22 as well as the detection system 20 except for the object 18. The system power supply consists of positive system voltage "Vsupply" and system ground "GND1", Vsupply is DC for GND1 and AC for ground. For example, Vsupply and GND1 are DC voltages that maintain a potential difference of 5V each other. However, the system voltage is AC for ground ground, as in the embodiment of FIG. 7 or FIG. 8 to be described later.

The detection system 20 may be implemented as an integrated circuit (IC) or a circuit mounted on a PCB, and the method of implementation is not limited to a combination of various components. If the detection system 20 uses only a part of the IC or PCB, the AC voltage may only be supplied to the detection system 20, which is a part of the IC or PCB. Alternatively, it may be supplied to the whole area of the IC or the circuit of the whole PCB according to the circuit configuration.

The AC voltage, which is the power source of the system, is a voltage in which the amplitude and phase are alternately regulated or non-regulated in magnitude and phase. The AC voltage will be described with reference to FIGS. 7 and 8. FIG.

FIG. 7 is a diagram of alternating voltage with regularly alternating magnitude and phase, and FIG. 8 is a diagram of alternating voltage with magnitude and phase being non-regular. First, the AC voltage having a regular size and phase will be described with reference to FIG.

7 is an AC voltage having a Max voltage of 30 V and a Min voltage of 10 V and an amplitude of an alternating voltage of 20 V based on the ground potential. Therefore, Vsupply alternates 20V based on the ground potential. System ground GND1 maintains Vsupply and 5V. Therefore, GND1, which is the system ground, is an alternate AC power source having a Max voltage of 25 V and a Min voltage of 5 V based on the ground potential. Therefore, the system power supply Vsuppy is an AC voltage based on the ground potential, but is a DC voltage 5V based on GND1 (that is, when GND1 is grounded). Also, the period of the AC voltage is 60 Hz and the phase is also regular.

As shown in FIG. 7, an AC voltage having a regular magnitude and phase with respect to the ground potential can be applied as the system voltage, but an AC voltage having irregular size and phase can be applied to the system power. Fig.

Referring to FIG. 8, since the positive system power supply (Vsupply) is 5V based on the system ground (GND1), Vsupply is a DC voltage based on GND1. The fluctuation range of the AC voltage in the region 1 is 20V, the fluctuation width of the AC voltage in the region 2 is 15V, and the fluctuation width or the size of the AC voltage in the region 3 is 25V. The AC voltage of the region 1 has the same rising period and the falling period, and the AC voltage of the region 2 is different between the rising period and the falling period. When the rising period and the falling period are different from each other, . And the AC voltage in the region 3 is an example in which the vertical rise and the vertical fall occur at the time of rise and fall. Thus, an AC voltage of irregular size and phase can be used as the system power source.

In practical use, various AC voltages, such as those illustrated in regions 1 through 3, are not mixed with the system power supply, and it is desirable to use a single pattern. However, some patterns can be used sequentially by pre-programmed sequences.

Although the configuration of the system power source as in the embodiment of FIG. 8 is irregular, it is a voltage that varies in magnitude based on the ground potential. In the present invention, this voltage is also defined as an AC voltage (or alternating voltage) Regular AC waveforms have the advantage of being able to arbitrarily determine the slope of the period, rising pattern, or falling pattern.

The alternating voltage in FIG. 8 can realize a voltage rise and a voltage fall at a desired point in time. The pattern of the pre-programmed system power supply rise and fall occurs in synchronization with the UP or Down signal provided by the detection system 20. [

6 can be modeled as being grounded at the ground potential when the object 18 is a finger of a person and the finger of the elevator is depressed with a finger. In this case, VG in FIG. 6 is 0 (zero) It does not change. However, since the power of the system is an alternating voltage whose magnitude alternates with respect to the ground potential, when the magnitude of the system power varies, the potential at the point P in FIG. 6 alternates in synchronization with the system power. The potential applied to the sensor 14 via the sensor signal line 16 is also an alternating voltage as in the case of the point P because the potential at the point P is alternated.

The ground of the object 18 is connected to the sensor capacitor cs formed between the object 18 and the sensor 14 when the magnitude of the system power applied to the sensor 14 is changed when the ground potential is 0 V, The magnitude of the applied voltage also changes in synchronization with the system power supply.

When the voltage applied to the capacitor having the same capacitance is changed, a difference occurs in the amount of charge charged by the equation of Q = CV. The capacitance of the sensor capacitor can be detected by using a phenomenon in which a difference in the amount of charge charged in the sensor capacitor occurs when a difference in voltage applied to the sensor capacitor cs occurs, and a detailed method will be described later.

Most of the external potential VG applied to the object 18 is ground level, which is the case when the absolute magnitude is 0 (zero) V and DC. Also, the ground of the upper system including the detection system can be connected, and the ground of the upper system can be the floating ground of the DC battery. The external ground, in some cases, may be DC or higher or lower than the system power. 7, VG = 50V is higher than the system power, and VG = 0 is lower than the system power. The AC power can be used as ground VG to the object 18 and the AC voltage can be directly connected to the object 18 or as if the object 18 were being electromagnetically affected by a three- The AC voltage may be applied to the object 18 indirectly. If the AC power source is used as the ground of the object, it is not associated with the AC power source applied to the detection system 20. The AC power source mentioned later is an AC power source applied to the detection system 20. [

When the system power source is an AC voltage, an AC voltage which is a system power source is applied to the buffer 15 of FIG. 6 and an appropriate voltage is applied to the on / off control terminal and the input terminal 10-1 of the switching element 10, And a DC section is required for the AC voltage, which is a system power supply, in order to apply such a voltage.

In one embodiment, the AC power source has a DC section at the inflection point where rising, falling, or rising of regions 1 to 3 of FIG. 8 are distinguished.

Charges all capacitors commonly connected to the sensor 14 in the DC section of the AC power source. Further, in the DC section of the AC power source, the signal detecting unit 22 or the detecting system 20 performs calculations, or outputs any signal to the outside or receives an external signal. The external structure for exchanging signals with the signal detection unit 22 and the detection system 20 is a CPU or a circuit element associated with input and output of a signal. The ground of the external structure may be the same as or different from the ground of the detection system.

When the ground of the external structure is different from the ground of the detection system 20, it is preferable to generate the signal input / output of the detection system 20 and the external structure with the ground of the external structure and the ground of the detection system 20 interconnected Do.

The AC voltage for detecting the sensor capacitance CS of the present invention can detect the sensor capacitance CS in all the regions where the sensor capacitor CS is rising or falling and in order to use the falling region, , The AC voltage must be lowered in advance to use the rising area.

It is preferable that the charging to the point P in FIG. 6 using Vchg is performed in the DC interval of the AC voltage. However, charging may be performed in the rising interval or the falling interval in advance to raise the AC voltage have.

In the circuit of Fig. 6 for one embodiment of the present invention, the potential at point P is determined by the following equation (5).

≪ Eq. 5 &

In the equation 5, Vp is the potential of the point P input to the buffer 15, Vsupply is the magnitude of the alternating voltage of the positive system voltage, which is 20 V in the case of FIG. 7, Region 2 of 8 is 15V. Vchg is the charge voltage based on the ground ground and CAUX is the capacitance of the equivalent capacitor of the storage capacitor (cst) or the floating capacitor (cp). And CS is a capacitance of the sensing capacitor cs generated between the sensor 14 and the object 18. [

의 항만 작용하여 P점의 전압은 16V가 된다. 그러나 본 발명에서 추가된

가 0.1이라고 가정하면 <수식 5>의 Vp는 15V이며, 이는 16V로 상승하여야 하는 P점이 15V밖에 상승하지 못했음을 의미한다. 후술하겠지만, 상승하지 못한 1V는 "스윙 미달 요인"이라고 하는

의 항(Term)으로 결정되며 CAUX를 미리 알고 있다면 CS를 검출할 수 있으며 또는 시간의 추이에 따른 CS의 변화량을 검출하는 것이 가능하다.In Equation 5, Vsupply is a positive value when the positive system power supply Vsupply rises, and Vsupply is a negative value when Vsupply falls. For example, when the switching element 10 is turned off after the Vchg of FIG. 6 is charged to 6 V and the P point of FIG. 6 is charged to 6 V and the P point becomes Hi-z, 5>

The voltage at the point P becomes 16V. However,

Is 0.1, Vp in Equation 5 is 15V, which means that the point P which needs to be raised to 16V has only risen by 15V. As will be described later, the 1V that did not rise is called the "

, And if the CAUX is known in advance, it is possible to detect the CS, or it is possible to detect the amount of change of the CS according to the change of the time.

가 0.1이라고 가정하면 <수식 5>의 Vp는 다음과 같다. On the other hand, when the system power is lowered in Equation 5, the magnitude of Vsupply should be -10V. In one embodiment, when Vchg is 16V and the system power is lowered by 10V in a state where the P point maintains the charge and Hi-z states, the point P in FIG. 6 is generally 6V. But

Is assumed to be 0.1, Vp in Equation (5) is as follows.

. 이는 P점이 6V가 되어야 하나 1V만큼 하강하지 못했다는 의미이며 1V는 센서커패시턴스의 크기에 좌우되므로 이를 통해 센서커패시턴스의 크기를 알 수 있다.

. This means that the point P has to be 6V but it has not fallen by 1V, and 1V depends on the size of the sensor capacitance, so that the size of the sensor capacitance can be known.

Referring to the waveforms relating to the system voltages in FIGS. 7 and 8, since the positive system voltage Vsuuply and the system ground GND1 maintain a constant DC voltage, the system ground GND1 The positive system voltage (Vsupply) is equal to the alternating alternating voltage and magnitude. Therefore, Equation (5) can be expressed as Equation (6) below.

&Quot; (6) &quot;

In the following description, since Vsupply included in the equation has the same alternating size as GND1, Vsupply and GND1 in Equation can be used with the same meaning, but Vsupply is used as a representative. Therefore, although Vsupply is used in the formula, it is possible to use GND1 instead of GND1.

If there is no object 18 in FIG. 5, the sensor capacitor cs is not formed between the sensor 14 and the object 18, and CS is zero. Thus, Equation 6 can be expressed by Equation Is expressed.

&Quot; (7) &quot;

Equation 5 is the potential of the point P detected by the signal detector 22 when the object 18 is present and Equation 7 is the potential of the point P detected by the signal detector 22 when the object 18 is absent , It is possible to judge whether the object 18 has approached the sensor based on the value obtained by subtracting (Equation 5) from Equation (7).

The present invention can determine the presence or absence of the object 18 approaching the sensor 14 in this way, but it is also possible to detect a change in the opposing distance or the opposing area of the object 18 and the sensor 14 .

4, the distance between the object 18 and the sensor 14, or the distance between the object 14 and the sensor 14, When a change occurs, a change in the capacitance magnitude formed between the sensor 14 and the object 18 occurs. Therefore, when the sensor 14 and the object 18 have a predetermined opposite distance or an opposite area, the detected potential at the point P is Vp1, and the sensor 14 and the object 18 , It is possible to detect the change of the opposing distance or the opposite area of the object 18 and the sensor 14 by the difference between Vp1 and Vp2 detected in the expression (5) Do.

항을 참조하면, 아래와 같이 정리할 수 있다.In Equation 5,

, It can be summarized as follows.

(Theorem 1) The capacitance of all capacitors connected to point P is in the denominator.

(Theorem 2) The capacitance of a capacitor not connected to system ground (GND1) is located in the molecule.

(Theorem 3) The capacitance of the capacitor connected to system ground (GND1) is located in the denominator.

As described above, the CAUX is an equivalent circuit of a plurality of capacitors connected to the point P in FIG. 6 and the other end is connected to the system ground GND1, so that CAUX actually consists of capacitances of many capacitors even though it looks like one capacitance . In Equation (5) based on FIG. 6, there is one capacitor to which the ground is connected to the external power source, but in other embodiments, there may be a plurality of capacitors.

The sensor capacitance CS of the sensor capacitor cs can be detected in all cases in which the AC power source as the system power source rises or falls and the detailed description of the detection of the sensor capacitance CS based on the rise or fall of the AC power source Is as follows.

* Example in case of system power rise

The case where the AC power of FIG. 8 is used as the system power supply in the detection system 20 of FIG. 6 is described as an embodiment of detecting the sensor capacitance when the system power is increased. Assuming that the point P of the detection system 20 is charged at the time point t1 immediately before the region 1 in FIG. 8 and the charge voltage Vchg is 6 V and CAUX = 20 pF and CS = 1 pF, Vsupply changes from 20 V to Min, Vsupply = + 20V in Equation (5) because the value of Vsupply becomes larger. The magnitude of the voltage detected at the point P after the alternation is completed is as follows.

<Formula 1>

Assuming that there is no sensor capacitance CS in Equation 1, the magnitude of Vp is 26V. This means that the P point charged at 6V will be 26V if the detection system is increased by 20V. However, if CS is present and its size is 1pF, it means that it is less than 0.9524V at 26V. In the present invention, this undervoltage can be detected to determine whether a sensor capacitor is present, i.e., whether the finger is depressing the button as shown in the embodiments of the finger and elevator buttons. It is also possible to detect the magnitude of the undershoot voltage and detect how far the sensor 14 and the object 18 are opposed to each other or what the opposed area is. By tracking the amount of change of these values, It is possible to detect a change or a change in the opposite area. 4, when the opposing distance or the facing area between the object 18 and the sensor 14 changes, the capacitance changes. Therefore, it is not possible to determine what the capacitance changes due to the opposing distance or the opposite area being changed at the same time Do. Therefore, in practice, it is desirable to detect a change in the facing area when the opposite distance is constant, or to detect the size and amount of the opposite distance in the case where the system constitutes the opposite area constant and the opposite distance varies.

* Example in case of system power down

A method of detecting the capacitance when the system power supply is lowered using the detection system of Fig. 6 and the AC power supply of Fig. 8 is as follows. First, the point P in FIG. 6 is charged. 8, the magnitude of the voltage of GND1 is 25 V with reference to the ground potential at time point t2, which is the DC region of the region 1 in Fig. Therefore, charging Vchg at 1 V with respect to GND1 at point P in Fig. 6 at time t2 in Fig. 8 region 1 is equivalent to charging Vchg to 26 V with reference to the ground ground. Assume that the point P in FIG. 6 is charged by Vchg of 26V, CAUX is 20pF, and CS = 1pF. Vsupply is -20V when Vsupply falls by 20V from Max to Min, as in the latter embodiment of Region 1 of Fig. Accordingly, the magnitude of the voltage detected at the point P after the system power supply is lowered by 20 V according to Equation (5) is as follows.

<Formula 2>

Referring to Equation 2, the P point charged at 26V means that the system power is lowered by 20V, which is 6V but is lower than 0.9524V due to the sensor capacitor (cs). Referring to this value, it is shown that the value which is less than the target value is the same when the system power is up or down with respect to the same parameter of Equation 5.

6 and FIG. 5 illustrate the case where one object 18 connected to the external ground is one. However, in some systems, a plurality of objects 18 exist and each object 18 has the same size It is connected to another external ground. In the present specification, a plurality of external grounds are denoted by VG1 and VG2, and VG1 and VG2 include cases where the magnitudes are equal to or different from each other.

Fig. 9 shows an embodiment in which a plurality of objects are used in the capacitance detection system 20 of the present invention. Fig. 9A shows a case where two objects 18-1 and 18-2 are fixed and the sensor 14 is moved The case where d1 and d2 are both changed by the movement of the sensor 14 is the case. d1 is the opposing distance between the sensor 14 and the object 1 (18-1), and d2 is the opposing distance between the sensor 14 and the object 2 (18-2). It is assumed that the sensor 14 and the opposing areas of the objects 18-1 and 18-2 are the same. An object capable of moving the sensor 14 is configured as the sensor signal line 16 in the sensor 14 and the sensor 14 and the objects 18-1 and 18-2 A displacement occurs. The external ground 1 (VG1) is connected to the object 1 (18-1) by a spring wire, and the external ground 2 (VG2) is connected to the object 2 (18-2) by a spring wire. A sensor capacitor 1 cs1 is formed to have a capacitance of CS1 between the sensor 14 and the object 1 18-1 and cs2 / CS2 is formed between the sensor 14 and the object 2 18-2 . As the sensor 14 moves, the sizes of CS1 and CS2 change.

9B shows an example in which the sensor 14 and the object 2 18-2 are fixed but the distance between the object 1 18-1 and the sensor 14 is changed by the movement of the object 18-1 to be. Referring to FIG. 9B, an object 1 (18-1) connected to the object 1 (18-1) is connected to an external ground 1 (VG1) connected to the object 1 (18-1). And an external ground 2 (VG2) is connected to the object 2 (18-2). In the embodiment as shown in FIG. 9B, the sensor 14 and the object 2 18-2 are fixed, so that the distance d2 between them is fixed and the magnitude of the capacitance CS2 formed therebetween is fixed. However, on the other side of the sensor 14, there is a capacitance CS1 formed with the object 1, and the size of the capacitance CS1 formed therebetween is changed by the movement of the object 1 18-1.

Although FIGS. 9A and 9B illustrate the case of two objects, a system can be implemented that includes more sensors 14 and many objects that make capacitors opposite to those sensors. Although only two objects are exemplified herein, the principles of the present invention can be applied to objects more than two objects.

10 is a circuit diagram of a detection system in which a plurality of sensor capacitances can be detected. Referring to FIG. 10, there are two objects 14-1 and 14-2 opposed to each other, and two sensors 14 are two-sided or different sensors of one sensor. A signal detected at the point P when alternate AC power is supplied to the detection system 20 detecting the two sensor capacitances CS1 and CS2 at the magnitude of Vsupply is as follows.

&Quot; (8) &quot;

In Equation 8, Vp is the potential of the point P input to the buffer 15, Vsupply is the magnitude of the alternating voltage of the system voltage, and Vchg is the charging voltage with respect to the ground. CAUX is the capacitance of the equivalent capacitor of the storage capacitor (cst) or the floating capacitor (cp) or the capacitance of the equivalent capacitor of cs and cp. CS is the capacitance of the sensor capacitor cs generated between the sensor 14 and the object 18 and CS1 is the capacitance formed between the sensor 14 and the object 1 18-1 and CS2 is the capacitance formed between the sensor 14 and the object 18, 2 (18-2).

In Equation (8), when d1 and d2 are changed as shown in FIG. 9A, it is not easy to individually calculate d1 and d2. However, when d2 is fixed as shown in FIG. 9B, only the amount of change of CS1 occurs. Therefore, the size of d1, the size of the opposing area between the object 1 (18-1) and the sensor 14, Can be detected.

(Theorems 1) to (theorem 3) are similarly applied even when detecting a plurality of sensor capacitances.

Equation 8 is a formula of a signal detected at point P with respect to two objects 18-1 and 18-2 or a signal detected at point P in FIG. 10 when there are two or more objects connected to the external ground The generalization of the equation is shown in Equation (9) below.

&Lt; Equation (9)

In Equation (9), Vp is the potential of the point P input to the buffer 15, Vsupply is the magnitude of the alternating voltage of the system voltage, and Vchg is the charging voltage with respect to the ground. CAUX is the capacitance of the equivalent capacitor of the storage capacitor (cst) or the floating capacitor (cp). CS is the capacitance of the sensor capacitor cs generated between the sensor 14 and the object 18, CS1 is the capacitance formed between the sensor 14 and the object 1 18-1, CS2 is the capacitance between the sensor 14 and the object 18 And the capacitance formed between the object 2 (18-2). Also, n is the number of a plurality of objects facing the sensor 14 connected to the external ground, and is proportional to the number of objects such as 1 in one, 2 in two, and 3 in three. Equation (9) when n is 1 is Equation (5), and when n is 2, Equation (9) is Equation (8).

(Theorems 1) to (theorem 3) are applied to the plurality of objects 18 in the same manner.

When a plurality of sensor capacitors cs are used in the detection system 20, a plurality of objects can be opposed to one sensor 14, and one object can be opposed to one sensor.

A plurality of sensor capacitances CSn generated by a plurality of objects 18 are connected to the signal detection unit 22 of the detection system 20 by a common connection . Since the plurality of sensor capacitors csn are connected to the external ground VG, the plurality of sensor capacitors csn operate as variable capacitors and cause charge sharing with the fixed capacitors as described above. However, if a plurality of objects constituting the plurality of sensor capacitors csn and a plurality of sensors 14 generate a displacement or a change in the area of a counter electrode, You can not tell if a change has occurred. Therefore, a change in the displacement or the opposite area between the sensors 18 opposed to only one of the plurality of objects 18 constituting the plurality of sensor capacitors csn must be caused to cause a change in the sensor capacitance CS The object can be found.

When an object causing a change in the sensor capacitance CS in a plurality of objects is defined as a dynamic object and an object not causing the change is defined as a static object, The change of Vp defined in the equation (9) can be detected because the static object does not cause the change of the sensor capacitance (CS) of the equation (9) I never do that.

The present invention is capable of extracting a variation amount of variable capacitance caused by one dynamic object in a detection system composed of a plurality of variable capacitances using this principle.

Referring to Equation (9), Vp detected due to a dynamic object and a variable object at an arbitrary time point is stored in a memory of a detection system (not shown), and Vp is detected again after a predetermined time has elapsed. By analyzing the difference between the stored Vp and the subsequent Vp, it is possible to know a change in the size of the sensor capacitance CS caused by the size change due to the dynamic object.

Assuming that the distance between the object and the sensor is fixed, it is possible to extract the amount of area change between the dynamic object and the sensor by substituting the amount of change in the sensor capacitance in the equation of FIG. 4, For example, to change the moving speed of the elevator.

It is impossible to detect a plurality of capacitances (CSn) formed between the plurality of objects 18 and the sensor 14 in Equation (9) with one signal detection using Equation (9), and one sensor capacitance It is more preferable to detect one sensor capacitance whose capacitance is not fixed in the state where the remaining sensor capacitances are fixed.

항(term)을 "스윙 미달 요소"라고 정의하면, 스윙 미달 요소는 시스템전원이 교번하는 크기에 비례하며 센서커패시턴스(CS)의 크기와도 비례하는 것을 알 수 있다. "스윙 미달 요소"는 <계산식 1>이나 <계산식 2>를 참조하면, 시스템전원이 교번할 때 센서(14)에서 교번하는 전압이 시스템전원의 변화량과 동일한 크기로 교번하지 못하는 값을 결정하는 인자이다.On the other hand,

If the term is defined as a "sub-swing element," the under-swing element is proportional to the alternating system power and is also proportional to the magnitude of the sensor capacitance (CS). Referring to equations (1) and (2), the term "under-swing element" refers to a factor that determines a value at which the alternating voltage at the sensor (14) to be.

The "swing-underside element" occurs on the basis of the charge sharing phenomenon between the capacitors commonly connected to the P point in FIG. 6 or 10, that is, the input portion of the signal detecting portion 22, and the charge sharing phenomenon of the present invention is as follows You can organize.

(Theorem 4) The capacitors commonly connected to the input terminal 15 of the signal detection unit 22 of the same detection system 20 accumulate a predetermined amount of charge. To this end, the input terminal 15 is charged with Vchg, and the amount of charge accumulated by each capacitor due to Vchg is defined as the initial charge amount.

(Theorem 5) The external ground is connected to part of the capacitor in the theorem 4. The capacitor connected to the external ground is called "variable capacitor ". The sensor capacitor cs is a variable capacitor.

(Theorem 6) The system ground GND1 is connected to part of the capacitor in the theorem 4. The capacitors connected to the system ground are called "fixed capacitors". The auxiliary capacitor (caux) is a fixed capacitor.

(Theorem 7) Since the system power source is AC power, when the system power alternates between rising and falling, the voltage applied to the variable capacitor in (5) changes in size in synchronization with the system power supply. According to the principle of Q = CV, a difference is generated in the amount of charge accumulated by the capacitor due to the change in the voltage applied to the capacitor having the same capacitance, so that when the voltage applied to the variable capacitor is increased, When the voltage applied to the variable capacitor is lowered, it discharges the accumulated charge and accumulates less charge than the initial charge amount.

(Theorem 8) Since the fixed capacitors are connected to the system ground, the magnitude of the voltage applied to the fixed capacitors does not change due to the influence of the alternating system ground even if the P points are synchronized by the alternating system power sources and the same size is alternated. Therefore, the initial charge amount of the fixed capacitor is maintained even when the system voltage alternates.

(Theorem 9) The charge discharged from the variable capacitor is distributed and accumulated in the fixed capacitors, and the voltage of the fixed capacitor rises by the principle of Q = CV.

(Theorem 10) When the variable capacitor can accumulate more charge, the fixed capacitors emit charge to the variable capacitor, and the voltage of the fixed capacitor drops by the principle of Q = CV.

(Theorem 11) Since the voltage at the point P with reference to the system ground GND1 is determined by the magnitude of the voltage applied to the fixed capacitor (theorem 9) and (theorem 10), the voltage at the point P A change in size occurs.

(Theorem 12) When the change in the magnitude of the voltage of the system ground (GND1) is taken as a reference (theorem 11), the magnitude or magnitude of the fluctuating capacitance can be detected.

An example in which charge sharing phenomenon occurs due to the alternation of system power on the basis of such the theorem will be described with reference to Figs. 8 and 10. In the following description, the embodiment of FIG. 9B is cited, whereby two objects are opposed to one sensor 14. Since the object 2 (18-2) and the sensor 14 are fixed, CS2 does not change in size. The sensor capacitance 1 (CS1) formed between the sensor 14 and the object 1 (18-1) maintains the same opposing area and changes the opposing distance or maintains the same opposing distance, The size of the sensor capacitance 1 (CS1) is changed. In this embodiment, the opposite facing area (d1 in FIG. 9) is maintained and the size of CS1 is changed. However, this method is merely an embodiment, and it is a matter of course that the CS1 changes even when the opposite area of the sensor 14 and the object 1 18-1 is constant but the opposing distance d1 changes.

The present invention can detect the presence or absence of the object 1 18-1 and detect the amount of opposing area change between the object 1 18-1 and the sensor 14. [ For example, if the potential Vp of the point P generated by the opposite area of the sensor 14 and the object 1 18-1 at an arbitrary point in time in FIG. 9B is detected and the amount of change in Vp is detected as time elapses, 1 18-1 and the amount of change in the area of the opposing surface of the sensor can be detected. For example, assuming that the magnitude of Vp at an arbitrary point in time is 25V and the magnitude of Vp after 24 hours is 24V, it means that the size of CS1 has increased. Therefore, -1) and the sensor 14 is increased.

The following is a more detailed embodiment for detecting the sensor capacitance CS based on the rise or fall of the system power supply, and is an embodiment applied to the above theorem.

Example of sensor capacitance detection based on rise of system power

1. (Example of the Theorem 4)

In FIG. 10, the object 1 (18-1) is opposed to the sensor 14 at a predetermined fixed distance and variable area so that a variable capacitance having a size of CS1 is formed, and the variable capacitance or capacitance to which the external ground is connected to CS2 is fixed to be.

Assume that the ground VG1 of the object 1 (18-1) is the ground potential and the ground VG2 of the object 2 (18-2) is 4V DC based on the ground potential. Assuming that Vchg based on the ground potential is 6V, the point P in Fig. 10 is charged to 6V when the switching element 10 is turned on at the time point "t1 " in Fig. Therefore, the point P in FIG. 10 is 6V based on the ground potential, but the size of the point P in FIG. 10 based on GND1 having a size of 5V at time t1 in FIG. 8 is 1V.

As the point P in FIG. 10 is charged to the voltage of Vchg, a voltage is formed with respect to the potential applied to another side of the capacitor connected to the point P in FIG. For example, since the system ground GND1 is connected to the auxiliary capacitor caux and the size of the system ground GND1 is 5 V at the time t1 of FIG. 8, the magnitude of the initial voltage formed in the caux is larger than the system ground GND1 Lt; / RTI &gt; The reason why the initial voltage of the auxiliary capacitor caux is based on the system ground GND1 is that the system ground GND1 is connected to the auxiliary capacitor caux and the reference voltage of the sensor capacitor connected to the external ground is the external ground VG ).

Since VG1 connected to the sensor capacitor 1 (cs1) is 0 (zero) V and the point P is 6V, 6V is formed in the sensor capacitor 1 (cs1) based on VG1 and the initial voltage of cs1 is 6V based on VG1 . Since VG2 is 4V and P-point is 6V, the initial voltage of sensor capacitor 2 (cs2) based on VG2 is 2V.

On the other hand, according to the physical quantity Q = CV, a predetermined amount of charge is accumulated in each capacitor according to the capacitance of the capacitor and the formed voltage. For example, cs1 is charged with a predetermined charge amount corresponding to the capacitance CS1 and the initial voltage 6V, and the auxiliary capacitor caux is charged with the capacitance CAUX and the charge amount corresponding to the initial voltage 1V.

Thus, all the capacitors connected to the point P are charged with the charge corresponding to the capacitance and the voltage of the capacitor, and the amount of charge charged before the alternation of the system power source is called the initial charge amount.

2. Examples of (theorem 5) and (theorem 7)

An external ground VG1 is connected to the object 1 18-1 of FIG. 10, not the system ground GND1, and an external ground VG2 is also connected to the object 2 18-2 of FIG. When the system power applied to the detection system 20 of Fig. 10 rises by 20V as in the first half of the area 1 of Fig. 8, the P-viscosity of Fig. 10 rises by 20V in synchronization with the system power supply. Even when the power of the system increases by 20V, the magnitudes of the external grounds VG1 and VG2 do not change. Therefore, the voltage applied to the cs1 and cs2 also changes by 20V due to the increase of the point P by 20V. That is, as the point P gradually increases, the initial voltage of cs1, 6V, becomes 26V, and the initial voltage of cs2, 2V, becomes 22V (actually, an undershoot occurs in the charge sharing phenomenon but the variable capacitor and the fixed capacitor share charges If not done).

As the system voltage rises, the voltage formed in cs1 and cs2 also increases, and the amount of charge stored in cs1 and cs2 also increases with the expression Q = CV. If the initial voltage of cs1 is changed from 6V to 26V and there is no change in the size of CS1, that is, if there is no change in the opposing area and the opposing distance between the object 1 (18-1) and the sensor 14, It is possible to accumulate more electric charge proportional to the difference of 20V at 26V, which is larger than 20V.

Also, since the initial voltage of cs2 is 2V and the power of the system rises, the voltage applied to cs2 rises to 22V, so it is possible to accumulate more charges proportional to cs2, which is the rise of the system voltage, 20V.

3. Examples of (theorem 6) and (theorem 8)

The system ground GND1 is connected to the auxiliary capacitor caux of FIG. Therefore, when the system power applied to the detection system 20 of Fig. 10 rises by 20 V by the pattern of the first half of the area 1 in Fig. 8, the system ground GND1 also rises, (Assuming that it is not influenced by the variable capacitor).

Since the initial voltage applied to the auxiliary capacitor caux is 1 V with respect to the system ground GND1 and the system ground GND1 rises by 20 V even when the system voltage rises by 20 V, the voltage applied to the caux remains at 1 V do. Therefore, the voltage of the auxiliary capacitor connected to the system ground does not change even when the power of the system rises, and the amount of the stored electric charge does not change.

4. Examples of (theorem 9), (theorem 10), (theorem 11)

10, when the system power supply alternation is completed and the charge sharing phenomenon is completed and the detection system 20 detects the voltage at the point P, the switching element 10 is in the OFF state and the input terminal of the buffer 15 is Hi Since the -z state, the point P is a Hi-z state or a floating state. In the Hi-z state or the floating state, it is impossible to supply charge from the outside of the detection system 20 to the point P, and the total amount of charges at the point P is preserved by the law of conservation of charges.

Since the variable capacitors cs1 and cs2 can accumulate more electric charge, the electric charge required by the variable capacitor is supplied from the auxiliary capacitor caux connected to the system ground GND1. Since the accumulated charge amount of the auxiliary capacitor does not change even when the power of the system rises, if the charge of the auxiliary capacitor is supplied to the variable capacitor, the amount of charge of the auxiliary capacitor decreases and the magnitude of the voltage formed in the auxiliary capacitor due to the principle of Q = Becomes smaller. That is, since the size of the auxiliary capacitance CAUX does not change, the voltage V becomes low when the amount of charge Q decreases.

Since the auxiliary capacitor is connected between the point P and the system ground GND1, the voltage of the auxiliary capacitor is lowered, which means that the voltage at the point P is lowered with respect to the system ground GND1. Therefore, the P point charged with 6 V Vchg should be 26 V by the system power source which is 20 V rising as shown in the first half of FIG. 8, but it can not reach 26 V. The size of the voltage that is less than 26 V is called " .

5. (Embodiment 12)

Referring to Equation (8), since there is no CS1 when there is no object 1 (18-1), the detected voltage Vp1 is known at this time and a predetermined CS1 is formed by the appearance of the object 1 (18-1) The difference between Vp1 and Vp2 is calculated to confirm whether the object 1 (18-1) appears or not. Utilizing this principle, it is possible to operate the elevator when it detects that a finger touches the elevator button.

4, the size of the CS1 is changed and the size of the changed CS1 can be known through Equation 5. Accordingly, the object and the sensor 14 It is possible to detect a change in the opposing area of the light-receiving surface (if the opposite surface area is fixed). For example, in Equation 8, based on Vp1 detected for the fixed CS2 and the arbitrary CS1 variable, the magnitude of Vp2 detected when the magnitude of CS1 changes is "Vp1-Vp2" It is possible to detect a change in size of CS1. As a result, if it is detected that the area of contact between the button and the finger is gradually increased due to the tendency of the human's finger to be pressed more and more over time by the elevator button, the speed of the elevator is increased and the contact area between the finger and the button gradually decreases It will be possible to control the speed of the elevator to be slow.

Although the embodiment described above has been described with reference to FIG. 10 having two objects, even when there are two or more objects, it can be generalized by referring to (Equation 9).

Example of sensor capacitance detection based on system power supply drop

It is possible to detect a change in the absolute size or size of the sensor capacitance CS based on the charge sharing phenomenon even when the system power falls as shown in the pattern of the latter half of Fig.

In the case where the system power is lowered after completion of charging at the time point t2 in FIG. 8A, the voltage applied to the variable capacitor decreases, and the amount of charge accumulated in the variable capacitor cs decreases. Because of the decrease in the amount of accumulated charge of the variable capacitor, the discharged charge is accumulated in the fixed capacitor, which raises the voltage of the fixed capacitor caux, so that the voltage of the point P rises. Therefore, when the power of the system is lowered, the point P is an undershoot voltage that can not be lowered by the falling of the system power, and the magnitude of the undershoot voltage is determined based on the " This is the same as the embodiment in which the power source is raised.

Assume that the system capacitance CS1 is detected when the system power supply is lowered. Assuming that Vsupply based on the ground potential in FIG. 10 is 30V, GND1 is 25V, Vchg is 26V, VG1 is 0V, and VG2 is 4V , Vchg means 1V larger than GND1. When the system power is lowered by 20 V by the Down signal in the area 1 in the state where the P point is charged with Vchg and the switching element 10 is turned off, the potential of the P point should be 6 V, Due to the charge sharing phenomenon of the capacitors, the voltage becomes higher than 6V, and the magnitude of the undervoltage of the voltage which is less than 6V is determined based on the "undervoltage factor"

The detection method of the capacitance interlocked with the system power source AC has the effect of increasing the SNR by increasing the detection signal detected at point P in Fig.

If a capacitance of 1 pF is formed between the object 18 and the sensor 14 in Equation 5, Vp = 6.95238 V in Equation (2). If CS = 0.9 pF, the value of Equation 2 becomes Vp = 6.86124 V, because the opposite distance or the opposite area between the object 18 and the sensor 14 changes. The difference of Vp by 0.1pF of CS becomes 91mV. This is about 9% resolution when applied to a 10-bit ADC with a detection range of 1 V, so even if the ADC has a few percent noise, it can be detected. However, according to the capacitance detecting means coupled to the AC power source, the signal detected by the detecting system 20 is nine times as large as that of the signal detected by the detecting system 20, Since the signal level is increased, the SNR is improved and the detection signal can be relied upon.

A signal detection unit 22 is built in the detection system. The signal detection unit 22 includes an ADC unit, a DAC unit, an amplification unit, a power supply unit, and circuit elements necessary for signal detection. The DAC is used to detect the potential of point P, and the detected potential is amplified by the amplifier and input to the ADC. The signal converted to digital by the ADC unit is transferred to the computing unit to calculate the capacitance of cs or to calculate the amount of change of CS. Such a process is one embodiment, and it is natural for a person skilled in the art that another embodiment is possible. Further, other circuits not shown in the figure may be attached to the signal detector 22.

Thus, the capacitance detecting apparatus interlocked with the AC power supply of the present invention has an advantage that the change of the capacitance to be detected is located in the molecule of the detection formula and the detection sensitivity is improved, so that it is possible to stably detect the signal.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention as defined by the appended claims. Will be clear to those who have knowledge of.

10: Switching element 10-1: Switch input terminal
10-2; Switch output terminal 10-3: Switch on / off control terminal
12: high impedance input element 14: sensor
16: sensor signal line 18: object
20: detection system 22: signal detection unit

Claims (10)

A fixed capacitor having a fixed capacitance;
A variable capacitor for generating a variable capacitance;
A switching element for charging the fixed capacitor and the variable capacitor with a DC voltage or keeping the fixed capacitor and the variable capacitor in a floating state after charging; And
And a signal detector for detecting a voltage change due to charges flowing between the fixed capacitor and the variable capacitor,
Wherein the signal detecting unit detects the voltage change in synchronization with an alternating current (AC) voltage applied to the fixed capacitor, acquires the variable capacitance based on the detected voltage change,
Wherein the fixed capacitor is connected to a first ground on the same phase maintaining a constant voltage difference with the alternating voltage and the variable capacitor is attached to the sensor and the variable capacitance is set such that the external object contacts Wherein the first and second capacitances are generated when the variable capacitance is detected.
The method according to claim 1,
Wherein the variable capacitance varies corresponding to an opposing distance or an opposing area between the sensor and the external object.
The method according to claim 1,
Wherein the fixed capacitor has a capacitance of a floating capacitor generated by a connection with the signal detecting unit and an equivalent capacitance corresponding to a capacitance of the storage capacitor storing the charge.
The method according to claim 1,
Wherein the first ground maintains an amplitude difference of a constant magnitude with a frequency of the same phase as the AC voltage,
And a DC voltage is applied to the fixed capacitor based on the first ground.
The method according to claim 1,
The variable capacitor is connected to the second ground,
Wherein the second ground is a ground ground having a DC voltage of zero or a DC voltage of a predetermined magnitude.
6. The method of claim 5,
When outputting the detection result from the signal detecting section,
Wherein the first ground and the second ground are interconnected and the alternating voltage maintains a constant magnitude of DC voltage.
The method according to claim 1,
Wherein the first ground and the alternating-
Having a first frequency of a first duration and a second frequency of a second duration,
Wherein the first frequency and the second frequency are different frequencies,
Wherein the first duration and the second duration are alternating with each other.
The method according to claim 1,
The sensor has a plurality of sensing surfaces facing each other,
And generates a variable capacitance with a plurality of external objects approaching or contacting each of the plurality of sensing surfaces.
A fixed capacitor having a fixed capacitance;
A variable capacitor for generating a variable capacitance;
A switching element for charging the fixed capacitor and the variable capacitor with a DC voltage or keeping the fixed capacitor and the variable capacitor in a floating state after charging; And
And a signal detector for detecting the variable capacitance,
An operation of detecting, by the signal detecting unit, a voltage change caused by a charge floating between the fixed capacitor and the variable capacitor; And
Based on the voltage change, obtaining the variable capacitance by the signal detection unit,
Wherein the fixed capacitor is connected to a first ground on the same phase to which an alternating current (AC) voltage is applied and which maintains a constant voltage difference from the alternating current (AC) voltage,
Wherein the variable capacitor is attached to a sensor and the variable capacitance is generated when an external object contacts or approaches the sensor.
10. The method of claim 9,
Wherein the first ground maintains an amplitude difference of a constant magnitude with a frequency of the same phase as the AC voltage,
Wherein a DC voltage is applied to the fixed capacitor based on the first ground.

Images