JP4602941B2 - Capacitance sensor circuit - Google Patents
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Description
本発明は、静電容量センサ回路に関する。 The present invention relates to a capacitance sensor circuit.
従来、機器の操作用スイッチ等として、機械構造を持たず、操作者が操作面に触れた事を検出するセンサ回路が用いられている。前記センサ回路は機械構造によるスイッチと比べて設置スペースが少なくて済む等の利点があり、様々な形態の前記センサ回路が提案されている。それらセンサ回路のひとつとして広く用いられている回路に、操作者が操作面等に指等で触れることで、操作面等に生じる静電容量の変化に基づいて前記静電容量の変化を検出する静電容量センサがある。 2. Description of the Related Art Conventionally, a sensor circuit that does not have a mechanical structure and detects that an operator touches an operation surface is used as an operation switch for an apparatus. The sensor circuit is advantageous in that it requires less installation space than a switch having a mechanical structure, and various forms of the sensor circuit have been proposed. When the operator touches the operation surface or the like with a finger or the like on a circuit widely used as one of these sensor circuits, the change in the capacitance is detected based on the change in the capacitance generated on the operation surface or the like. There is a capacitance sensor.
静電容量センサ回路は、例えば特許文献１に示すように、パルス信号発生回路と抵抗、第１コンデンサ、第２コンデンサ、検出電極、差動増幅回路、交流−直流変換回路、比較回路を備える。そして、前記パルス信号発生回路の出力は差動増幅回路の反転（マイナス）入力端子に入力され、前記パルス信号発生回路の出力は抵抗を介して差動増幅回路の非反転（プラス）入力端子に入力される。又、差動増幅回路の非反転（プラス）入力端子には、第１コンデンサを介して検出電極が接続されると共に、第２コンデンサが接続されている。このように構成された静電容量センサ回路によれば、検出電極の静電容量が変化すると、差動増幅回路の反転（マイナス）入力端子と非反転（プラス）入力端子との間の電圧の位相差が変化し、前記位相差の変化に基づいて差動増幅回路の出力電圧に変化が生じる。そして、前記出力電圧を交流−直流変換回路にて直流にし、その直流電圧の変化を比較回路によって予め設定された閾値と比較することで、検出電極に操作者が接触したか否かを判断することのできる信号を出力する。 As shown in Patent Document 1, for example, the capacitance sensor circuit includes a pulse signal generation circuit, a resistor, a first capacitor, a second capacitor, a detection electrode, a differential amplifier circuit, an AC-DC conversion circuit, and a comparison circuit. The output of the pulse signal generating circuit is input to the inverting (minus) input terminal of the differential amplifier circuit, and the output of the pulse signal generating circuit is input to the non-inverting (plus) input terminal of the differential amplifier circuit via a resistor. Entered. A detection electrode is connected to the non-inverted (plus) input terminal of the differential amplifier circuit via a first capacitor, and a second capacitor is connected. According to the capacitance sensor circuit configured as described above, when the capacitance of the detection electrode changes, the voltage between the inverting (minus) input terminal and the non-inverting (plus) input terminal of the differential amplifier circuit is changed. The phase difference changes, and the output voltage of the differential amplifier circuit changes based on the change in the phase difference. Then, the output voltage is converted to a direct current by an AC-DC conversion circuit, and a change in the DC voltage is compared with a preset threshold value by a comparison circuit to determine whether an operator has touched the detection electrode. Outputs a signal that can
しかしながら、特許文献１に記載された静電容量センサ回路は、検出電極側からの信号とパルス信号発生回路からの信号との位相差から操作者が検出電極に接触しているか否かの判定をした。その為、操作者が検出電極に接触しているか否かの判定を行なうために比較回路で用いる閾値は、差動増幅回路の出力状態に合わせて調整が必要であった。そして、差動増幅回路の出力状態はパルス信号発生回路の周波数によって変化するので、前記閾値の設定には前記周波数の影響を考慮する必要があった。 However, the capacitance sensor circuit described in Patent Document 1 determines whether or not the operator is in contact with the detection electrode from the phase difference between the signal from the detection electrode side and the signal from the pulse signal generation circuit. did. Therefore, the threshold value used in the comparison circuit for determining whether or not the operator is in contact with the detection electrode needs to be adjusted according to the output state of the differential amplifier circuit. Since the output state of the differential amplifier circuit changes depending on the frequency of the pulse signal generation circuit, it is necessary to consider the influence of the frequency in setting the threshold value.
そこで、従来、図２に示すような静電容量センサ１１が提案されている。
図２に示す静電容量センサ１１は、静電容量検出回路１２、操作面１３を備え、操作面１３には検出電極１４が埋設されている。そして、検出電極１４は電線で静電容量検出回路１２の検出電圧端子１２ａと接続されている。
Therefore, conventionally, a capacitance sensor 11 as shown in FIG. 2 has been proposed.
A capacitance sensor 11 shown in FIG. 2 includes a capacitance detection circuit 12 and an operation surface 13, and a detection electrode 14 is embedded in the operation surface 13. The detection electrode 14 is connected to the detection voltage terminal 12a of the capacitance detection circuit 12 by an electric wire.
そして、この静電容量検出回路１２は、図３に示すように、発信器Ｖ１ｃ、出力抵抗Ｒ１ｏ、整流回路２１、フィルタ回路２２、差動増幅回路２３、基準電圧源Ｖｒｅｆ及び分圧抵抗Ｒ１、Ｒ２を備える。発信器Ｖ１ｃは、出力抵抗Ｒ１ｏと整流回路２１、フィルタ回路２２を介して差動増幅回路２３の非反転（プラス）入力端子に接続されている。又、出力抵抗Ｒ１ｏと整流回路２１との間には、検出電圧端子１２ａを介して検出電極１４が接続されている。さらに、差動増幅回路２３の反転（マイナス）入力端子は、分圧抵抗Ｒ２を介して差動増幅回路２３の出力端子に接続されると共に、分圧抵抗Ｒ１を介して基準電圧源Ｖｒｅｆの陽極側に接続されている。 As shown in FIG. 3, the capacitance detection circuit 12 includes a transmitter V1c, an output resistor R1o, a rectifier circuit 21, a filter circuit 22, a differential amplifier circuit 23, a reference voltage source Vref, and a voltage dividing resistor R1, R2 is provided. The transmitter V1c is connected to the non-inverting (plus) input terminal of the differential amplifier circuit 23 via the output resistor R1o, the rectifier circuit 21, and the filter circuit 22. A detection electrode 14 is connected between the output resistor R1o and the rectifier circuit 21 via a detection voltage terminal 12a. Further, the inverting (minus) input terminal of the differential amplifier circuit 23 is connected to the output terminal of the differential amplifier circuit 23 via the voltage dividing resistor R2, and the anode of the reference voltage source Vref via the voltage dividing resistor R1. Connected to the side.
このように構成された静電容量検出回路１２によれば、検出電極１４に人体が接触すると、検出電極１４の静電容量が人体と検出電極１４との間にある静電容量Ｃ１の分だけ増
加し、検出電圧端子１２ａにかかる検出電圧Ｖｄが下がる。その結果、差動増幅回路２３の出力電圧Ｖ１ｏに変化が生じる。前記出力電圧Ｖ１ｏの変化を図示しない判定回路に入力することによって、判定回路が操作面１３に操作者が接触したか否かを判定した信号を出力する。
しかしながら、静電容量センサ１１の静電容量検出回路１２は、差動増幅回路２３の出力を効率よく増幅するために、差動増幅回路２３の反転（マイナス）入力端子には、操作者が操作面１３に接触していない場合に非反転（プラス）入力端子に入力される電圧に近い電圧を、基準電圧源Ｖｒｅｆを調整して供給しなければならなかった。又、操作者が操作面１３に接触した場合に、検出電極１４にかかる電圧Ｖｄの変化を大きくするためには発信器Ｖ１ｃの周波数を高くする必要があった。そこで、静電容量検出回路１２の周波数を高くすると回路に用いる素子が高価になる問題があった。さらに、発信器Ｖ１ｃの周波数を高くすると、放射が起こる問題もあった。 However, since the capacitance detection circuit 12 of the capacitance sensor 11 efficiently amplifies the output of the differential amplifier circuit 23, an operator operates the inverting (minus) input terminal of the differential amplifier circuit 23. When the surface 13 is not touched, a voltage close to the voltage input to the non-inverting (plus) input terminal must be supplied by adjusting the reference voltage source Vref. Further, when the operator touches the operation surface 13, in order to increase the change in the voltage Vd applied to the detection electrode 14, it is necessary to increase the frequency of the transmitter V1c. Therefore, when the frequency of the capacitance detection circuit 12 is increased, there is a problem that an element used in the circuit becomes expensive. Furthermore, there is a problem that radiation occurs when the frequency of the transmitter V1c is increased.
本発明の目的は、発信器の周波数の影響の少ない静電容量センサ回路を提供することにある。 An object of the present invention is to provide a capacitance sensor circuit that is less affected by the frequency of the transmitter.
請求項１に記載の静電容量センサ回路は、発信器から出力される発信信号を、抵抗を介して検出電極に印加し、その検出電極の静電容量の変化を検出する静電容量センサ回路において、前記抵抗と前記検出電極との間に接続したコンデンサと、前記コンデンサの前記抵抗側の電圧と前記コンデンサの前記検出電極側の電圧との差の電圧を増幅する増幅回路とを備えたことを要旨とする。 The capacitance sensor circuit according to claim 1, wherein a transmission signal output from a transmitter is applied to a detection electrode via a resistor, and a change in capacitance of the detection electrode is detected. And a capacitor connected between the resistor and the detection electrode, and an amplifier circuit for amplifying the difference voltage between the voltage on the resistance side of the capacitor and the voltage on the detection electrode side of the capacitor. Is the gist.
請求項２に記載の静電容量センサ回路は、請求項１に記載の静電容量センサ回路において、前記増幅器は、差動増幅回路であることを要旨とする。
請求項３に記載の静電容量センサ回路は、請求項１又は２に記載の静電容量センサ回路において、前記増幅回路の出力端子には整流回路が接続され、前記増幅回路からの検出信号を前記整流回路を介して出力させることを要旨とする。
The capacitance sensor circuit according to claim 2 is the capacitance sensor circuit according to claim 1, wherein the amplifier is a differential amplifier circuit.
A capacitance sensor circuit according to a third aspect is the capacitance sensor circuit according to the first or second aspect, wherein a rectifier circuit is connected to an output terminal of the amplifier circuit, and a detection signal from the amplifier circuit is received. The gist is to output via the rectifier circuit.
請求項４に記載の静電容量センサ回路は、請求項３に記載の静電容量センサ回路において、前記整流回路の出力端子にはフィルタ回路が接続され、前記整流回路からの検出信号を前記フィルタ回路を介して出力させることを要旨とする。 The capacitance sensor circuit according to claim 4 is the capacitance sensor circuit according to claim 3, wherein a filter circuit is connected to an output terminal of the rectifier circuit, and a detection signal from the rectifier circuit is transmitted to the filter. The gist of the output is through a circuit.
請求項５に記載の静電容量センサ回路は、請求項１〜４のいずれか１つに記載の静電容量センサ回路において、前記コンデンサの静電容量は、検出電極の静電容量よりも十分小さい静電容量を有することを要旨とする。 The capacitance sensor circuit according to claim 5 is the capacitance sensor circuit according to any one of claims 1 to 4, wherein the capacitance of the capacitor is sufficiently larger than the capacitance of the detection electrode. The gist is to have a small capacitance.
請求項１の発明によれば、増幅回路は、抵抗とコンデンサ間の電圧と、コンデンサと検出電極間の電圧との差分を増幅する。この時、抵抗とコンデンサ間の電圧と、コンデンサと検出電極間の電圧の関係は、コンデンサの静電容量と検出電極の静電容量との関係で求められ、発信器の周波数の影響を受けない。その結果、発信器の周波数の影響の少ない静電容量センサ回路を構成することができる。 According to the invention of claim 1, the amplifier circuit amplifies the difference between the voltage between the resistor and the capacitor and the voltage between the capacitor and the detection electrode. At this time, the relationship between the voltage between the resistor and the capacitor and the voltage between the capacitor and the detection electrode is determined by the relationship between the capacitance of the capacitor and the capacitance of the detection electrode, and is not affected by the frequency of the transmitter. . As a result, it is possible to configure a capacitance sensor circuit that is less affected by the frequency of the transmitter.
又、周波数の影響が少ないため、好適に検出電極の静電容量の変化を検出するために発信器の周波数を高くする必要がなく、発信器の周波数が低くても好適に検出電極の静電容
量の変化を検出できる。従って、周波数が高いと問題となる放射を抑制できると共に、回路の部品に高い精度を求められない。さらに、発信器の周波数の変更に伴う回路の調整も不要になる。その結果、低い周波数でも好適に検出電極の静電容量の変化が検出できて、調整の煩わしさの少ない静電容量センサ回路を提供することができる。
In addition, since the influence of the frequency is small, it is not necessary to increase the frequency of the transmitter in order to detect a change in the capacitance of the detection electrode, and the electrostatic capacitance of the detection electrode is preferably set even if the frequency of the transmitter is low. Capacitance change can be detected. Therefore, radiation that becomes a problem when the frequency is high can be suppressed, and high accuracy is not required for circuit components. Furthermore, it is not necessary to adjust the circuit according to the change in the frequency of the transmitter. As a result, it is possible to provide a capacitance sensor circuit that can detect a change in the capacitance of the detection electrode suitably even at a low frequency and has less troublesome adjustment.
請求項２の発明によれば、差動増幅回路は、非反転（プラス）入力端子に入力された抵抗とコンデンサ間の電圧から反転（マイナス）入力端子に入力されたコンデンサと検出電極間電圧を引いた差分の電圧を増幅する。その結果、増幅回路の構造を容易にすることができる。 According to the second aspect of the present invention, the differential amplifier circuit obtains the voltage between the capacitor and the detection electrode input to the inverting (minus) input terminal from the voltage between the resistor and the capacitor input to the non-inverting (plus) input terminal. Amplifies the difference voltage. As a result, the structure of the amplifier circuit can be facilitated.
請求項３の発明によれば、増幅回路からの検出信号は、整流回路にて整流される。検出信号は利用が容易な直流成分の信号として出力することができる。
請求項４の発明によれば、整流回路からの検出信号は、フィルタ回路にてノイズが除去される。従って、ノイズが混入した検出信号であってもフィルタ回路を通ることによって、信号に混入したノイズを好適に除去され、誤差の少ない検出結果信号をフィルタ回路から出力することができる。
According to the invention of claim 3, the detection signal from the amplifier circuit is rectified by the rectifier circuit. The detection signal can be output as a DC component signal that is easy to use.
According to the invention of claim 4, noise is removed from the detection signal from the rectifier circuit by the filter circuit. Therefore, even if the detection signal is mixed with noise, the noise mixed in the signal is suitably removed by passing through the filter circuit, and a detection result signal with few errors can be output from the filter circuit.
請求項５の発明によれば、コンデンサの静電容量が検出電極の静電容量より十分小さければ、増幅回路からの検出信号にコンデンサの静電容量がほとんど影響しなくなる。なぜなら、増幅回路が増幅する、抵抗とコンデンサ間の電圧と、コンデンサと検出電極間の電圧の差は、コンデンサの静電容量と検出電極の静電容量との和で検出電極の静電容量を除した値に比例する。その為、コンデンサの静電容量が検出電極の静電容量より十分小さければ、前記値に対するコンデンサの静電容量の影響が小さくなるからである。その結果、電気的にはコンデンサの静電容量をほとんど考慮する必要がなくなり、より調整に煩わされない静電容量センサ回路を提供することができる。 According to the invention of claim 5, if the capacitance of the capacitor is sufficiently smaller than the capacitance of the detection electrode, the capacitance of the capacitor hardly affects the detection signal from the amplifier circuit. This is because the difference between the voltage between the resistor and the capacitor amplified by the amplifier circuit and the voltage between the capacitor and the detection electrode is the sum of the capacitance of the capacitor and the capacitance of the detection electrode. It is proportional to the divided value. Therefore, if the capacitance of the capacitor is sufficiently smaller than the capacitance of the detection electrode, the influence of the capacitance of the capacitor on the value is reduced. As a result, it is not necessary to consider the capacitance of the capacitor electrically, and a capacitance sensor circuit that is not bothered by adjustment can be provided.
（実施形態）
以下、本発明を具体化した実施形態を図１に従って説明する。
図１に、静電容量センサ回路１の回路図を示す。
(Embodiment)
Hereinafter, an embodiment of the present invention will be described with reference to FIG.
FIG. 1 shows a circuit diagram of the capacitance sensor circuit 1.
静電容量センサ回路１は、発信器Ｖｃ、抵抗Ｒｏ、コンデンサＣｏ、検出電極２、増幅回路としての差動増幅回路３、整流回路４、フィルタ回路５、外部出力端子６を備える。
発信器Ｖｃは、交流信号発信回路（例えば正弦波発信回路）であって、抵抗ＲｏとコンデンサＣｏを介して検出電極２に接続されている。
The capacitance sensor circuit 1 includes a transmitter Vc, a resistor Ro, a capacitor Co, a detection electrode 2, a differential amplifier circuit 3 as an amplifier circuit, a rectifier circuit 4, a filter circuit 5, and an external output terminal 6.
The transmitter Vc is an AC signal transmission circuit (for example, a sine wave transmission circuit), and is connected to the detection electrode 2 via a resistor Ro and a capacitor Co.
検出電極２は、人が指などで接触するため電極であり、導電性のある部材、例えば、金属などのような部材である。
差動増幅回路３の非反転（プラス）入力端子は、抵抗ＲｏとコンデンサＣｏとの間の接続点Ｐａに接続されると共に、その反転（マイナス）入力端子は、コンデンサＣｏと検出電極２との間の接続点Ｐｂに接続されている。さらに、差動増幅回路３の出力端子は整流回路４とフィルタ回路５を介して外部出力端子６に接続されている。又、差動増幅回路３の電圧増幅率は、増幅率Ｇとする。
The detection electrode 2 is an electrode for a person to contact with a finger or the like, and is a conductive member such as a metal.
The non-inverting (plus) input terminal of the differential amplifier circuit 3 is connected to the connection point Pa between the resistor Ro and the capacitor Co, and the inverting (minus) input terminal is connected to the capacitor Co and the detection electrode 2. It is connected to the connection point Pb. Further, the output terminal of the differential amplifier circuit 3 is connected to the external output terminal 6 via the rectifier circuit 4 and the filter circuit 5. The voltage amplification factor of the differential amplifier circuit 3 is assumed to be amplification factor G.
整流回路４は、交流信号を直流信号に変換する回路、例えば、全波整流回路であって、フィルタ回路５は、信号に含まれるノイズを除去するための回路、例えば、ローパスフィルタである。又、整流回路４から出力される直流信号の電力と、整流回路４に入力される交流信号の電力の比を、整流効率Ａとする。 The rectifier circuit 4 is a circuit that converts an AC signal into a DC signal, for example, a full-wave rectifier circuit, and the filter circuit 5 is a circuit for removing noise contained in the signal, for example, a low-pass filter. The ratio of the power of the DC signal output from the rectifier circuit 4 and the power of the AC signal input to the rectifier circuit 4 is defined as a rectification efficiency A.
本実施形態の静電容量センサ回路１の作用を説明する。尚、説明の便宜上、発信器Ｖｃ
は動作状態であるとする。
検出電極２に人体が触れていない通常の状態（非検出状態）では、検出電極２は開放状態である。従って、発信器Ｖｃが抵抗ＲｏとコンデンサＣｏに電力を供給しようとしても、検出電極２が開放状態なので、抵抗ＲｏとコンデンサＣｏに電気は流れない。抵抗ＲｏやコンデンサＣｏに電気が流れないことから、抵抗ＲｏとコンデンサＣｏの間の接続点Ｐａの電圧Ｖａも、コンデンサＣｏと検出電極２の間の接続点Ｐｂの電圧Ｖｂも発生しないため、前記電圧Ｖａ，Ｖｂはともに０Ｖである。
The operation of the capacitance sensor circuit 1 of the present embodiment will be described. For convenience of explanation, the transmitter Vc
Is the operating state.
In a normal state where the human body is not touching the detection electrode 2 (non-detection state), the detection electrode 2 is in an open state. Therefore, even if the transmitter Vc tries to supply power to the resistor Ro and the capacitor Co, electricity does not flow through the resistor Ro and the capacitor Co because the detection electrode 2 is in an open state. Since electricity does not flow through the resistor Ro and the capacitor Co, the voltage Va at the connection point Pa between the resistor Ro and the capacitor Co and the voltage Vb at the connection point Pb between the capacitor Co and the detection electrode 2 are not generated. The voltages Va and Vb are both 0V.
一方、検出電極２に人体が触れた場合（検出状態）では、検出電極２は人体を通してグランドに接続される。人体は静電容量を持つコンデンサとして電気的に等価表現できるので人体を検出容量Ｃとすると、発信器Ｖｃは、抵抗Ｒｏ、コンデンサＣｏ、検出電極２を介し検出容量Ｃからグランドに接続されたことになる。この時、発信器Ｖｃが抵抗ＲｏとコンデンサＣｏに電力を供給すると、抵抗ＲｏやコンデンサＣｏには電気が流れる。従って、抵抗ＲｏとコンデンサＣｏ間の接続点Ｐａ及びコンデンサＣｏと検出電極２の間の接続点Ｐｂに、それぞれ電圧Ｖａ、Ｖｂが発生する。 On the other hand, when the human body touches the detection electrode 2 (detected state), the detection electrode 2 is connected to the ground through the human body. Since the human body can be electrically expressed as a capacitor having electrostatic capacity, if the human body is a detection capacitor C, the transmitter Vc is connected from the detection capacitor C to the ground via the resistor Ro, the capacitor Co, and the detection electrode 2. become. At this time, when the transmitter Vc supplies power to the resistor Ro and the capacitor Co, electricity flows through the resistor Ro and the capacitor Co. Accordingly, voltages Va and Vb are generated at the connection point Pa between the resistor Ro and the capacitor Co and the connection point Pb between the capacitor Co and the detection electrode 2, respectively.
この時、接続点Ｐｂの電圧Ｖｂは、接続点Ｐａの電圧Ｖａと静電容量（コンデンサ）の合成・分圧の関係とから式（１）の様に表すことができる。尚、式（１）〜（４）では、便宜上、検出容量Ｃの静電容量をＣ、コンデンサＣｏの静電容量をＣｏと表現している。 At this time, the voltage Vb at the connection point Pb can be expressed as in Expression (1) from the relationship between the voltage Va at the connection point Pa and the combined / divided voltage of the capacitance (capacitor). In formulas (1) to (4), for the sake of convenience, the capacitance of the detection capacitor C is expressed as C, and the capacitance of the capacitor Co is expressed as Co.
差動増幅回路３の非反転（プラス）入力端子に前記電圧Ｖａが、反転（マイナス）入力端子に前記電圧Ｖｂが入力されることから、差動増幅回路３は電圧Ｖａと電圧Ｖｂの差分、（電圧Ｖａ−電圧Ｖｂ）を増幅することとなる。差動増幅回路３の増幅対象である（電圧Ｖａ−電圧Ｖｂ）は式（１）の結果を利用すると、式（２）の様に表すことができる。 Since the voltage Va is input to the non-inverting (plus) input terminal of the differential amplifier circuit 3 and the voltage Vb is input to the inverting (minus) input terminal, the differential amplifier circuit 3 has a difference between the voltage Va and the voltage Vb, (Voltage Va−Voltage Vb) will be amplified. (Voltage Va−Voltage Vb) to be amplified by the differential amplifier circuit 3 can be expressed as Equation (2) by using the result of Equation (1).
出力電圧Ｖｇ＝Ｇ×（Ｖａ×Ｃ／（Ｃｏ＋Ｃ））・・・（３）
差動増幅回路３の出力端子の出力電圧Ｖｇは、整流回路４とフィルタ回路５からなる信号調整回路を介して外部出力端子６に検出信号としての検出電圧Ｖｏとして出力される。
Output voltage Vg = G × (Va × C / (Co + C)) (3)
The output voltage Vg at the output terminal of the differential amplifier circuit 3 is output as a detection voltage Vo as a detection signal to the external output terminal 6 through a signal adjustment circuit including the rectifier circuit 4 and the filter circuit 5.
整流回路４は、例えば整流効率Ａの全波整流回路であるから、出力電圧Ｖｇは、おおよそ整流効率Ａ×｜出力電圧Ｖｇ｜に変換される。又、フィルタ回路５は｜出力電圧Ｖｇ｜に含まれる不要なノイズ成分を除去することが目的であることから、｜出力電圧Ｖｇ｜の主成分には変化を与えない。従って、外部出力端子６に出力される検出電圧Ｖｏは、おおよそ検出電圧Ｖｏ∝整流効率Ａ×｜出力電圧Ｖｇ｜となる。これに式（３）の結果を用いると検出電圧Ｖｏは式（４）の様に表すことができる。 Since the rectifier circuit 4 is, for example, a full-wave rectifier circuit with a rectification efficiency A, the output voltage Vg is approximately converted into a rectification efficiency A × | output voltage Vg |. Since the filter circuit 5 is intended to remove unnecessary noise components contained in the | output voltage Vg |, the main component of the | output voltage Vg | is not changed. Therefore, the detection voltage Vo output to the external output terminal 6 is approximately the detection voltage Vo∝rectification efficiency A × | output voltage Vg |. If the result of Formula (3) is used for this, detection voltage Vo can be expressed like Formula (4).
検出電圧Ｖｏ∝（Ａ×Ｇ｜Ｖａ｜×Ｃ）／（Ｃｏ+Ｃ）・・・（４）
上記作用により、検出電極２に人体が触れていない非検出状態の場合は、電圧Ｖａも検出容量Ｃも０であるので、検出電圧Ｖｏは０となる。一方、検出電極２に人体が触れている検出状態の場合は、検出容量Ｃがあり、電圧Ｖａも発生し、検出電圧Ｖｏに式（４）に基づいた電圧が出力される。
Detection voltage Vo∝ (A × G | Va | × C) / (Co + C) (4)
Due to the above action, in the non-detection state where the human body is not touching the detection electrode 2, the voltage Va and the detection capacitance C are 0, so the detection voltage Vo is 0. On the other hand, in the detection state where the detection electrode 2 is touched by a human body, there is a detection capacitor C, a voltage Va is also generated, and a voltage based on the expression (4) is output as the detection voltage Vo.
又、本実施形態の静電容量センサ回路１の外部出力端子６の検出電圧Ｖｏは、式（４）に示すように、検出容量Ｃの静電容量、コンデンサＣｏの静電容量、整流効率Ａ、増幅率Ｇ、電圧Ｖａの影響を受けるが、周波数の影響は抑制されている。 In addition, the detection voltage Vo at the external output terminal 6 of the capacitance sensor circuit 1 of the present embodiment, as shown in the equation (4), is the capacitance of the detection capacitor C, the capacitance of the capacitor Co, and the rectification efficiency A. Although influenced by the amplification factor G and the voltage Va, the influence of the frequency is suppressed.
本実施形態によれば以下のような効果を得ることができる。
（１）本実施形態によれば、検出電圧Ｖｏは、抵抗ＲｏとコンデンサＣｏとの間の電圧Ｖａと、コンデンサＣｏと検出電極２との間の電圧Ｖｂの差分を差動増幅回路３で増幅して求めた。この時、電圧Ｖａと電圧Ｖｂの差分である、（電圧Ｖａ−電圧Ｖｂ）は、式（２）に示すようにコンデンサＣｏと検出容量Ｃとの静電容量の関係だけで求められる。その結果、発信器Ｖｃの周波数による影響が少ない静電容量センサ回路１を構成することができた。
According to this embodiment, the following effects can be obtained.
(1) According to the present embodiment, the detection voltage Vo amplifies the difference between the voltage Va between the resistor Ro and the capacitor Co and the voltage Vb between the capacitor Co and the detection electrode 2 by the differential amplifier circuit 3. And asked. At this time, (voltage Va−voltage Vb), which is the difference between the voltage Va and the voltage Vb, is obtained only by the relationship between the capacitance of the capacitor Co and the detection capacitor C as shown in the equation (2). As a result, it was possible to configure the capacitance sensor circuit 1 that is less affected by the frequency of the transmitter Vc.
（２）本実施形態によれば、静電容量センサ回路１は発信器Ｖｃの周波数による影響が少ないことから、静電容量センサ回路１は、静電容量センサ回路１の構成条件に発信器Ｖ
ｃの周波数の影響を少なくすることができた。その結果、発信器Ｖｃの周波数を低くすることが可能となり、周波数が高いほど問題となる放射の影響を抑制することができた。又、周波数の変更による回路調整が不要で、調整が非常に容易となる静電容量センサ回路１を提供することができた。
(2) According to the present embodiment, the capacitance sensor circuit 1 is less affected by the frequency of the transmitter Vc.
The influence of the frequency of c could be reduced. As a result, the frequency of the transmitter Vc can be lowered, and the influence of radiation that becomes a problem can be suppressed as the frequency becomes higher. In addition, it is possible to provide the capacitance sensor circuit 1 which does not require circuit adjustment by changing the frequency and can be adjusted very easily.
（３）本実施形態によれば、静電容量センサ回路１は発信器Ｖｃの周波数による影響が少ないことから、発信器Ｖｃの周波数が低くても検出状態を検出できることができた。その結果、低い周波数でも良好に検出状態を検出することができる、静電容量センサ回路１を提供することができた。 (3) According to the present embodiment, since the capacitance sensor circuit 1 is less affected by the frequency of the transmitter Vc, the detection state can be detected even when the frequency of the transmitter Vc is low. As a result, it was possible to provide the capacitance sensor circuit 1 that can detect the detection state satisfactorily even at a low frequency.
（４）本実施形態によれば、静電容量センサ回路１は発信器Ｖｃの周波数による影響が少ないことから、発信器Ｖｃの周波数を低くすることが可能となり、周波数特性の低い安価な部品を採用することができた。その結果、静電容量センサ回路１のコストを抑えることができた。 (4) According to the present embodiment, since the capacitance sensor circuit 1 is less affected by the frequency of the transmitter Vc, it is possible to lower the frequency of the transmitter Vc, and an inexpensive component with low frequency characteristics can be obtained. I was able to adopt it. As a result, the cost of the capacitance sensor circuit 1 could be suppressed.
（５）本実施形態によれば、静電容量センサ回路１の発信器Ｖｃは、例えば、正弦波発信回路とした。従って、電圧Ｖａや電圧Ｖｂ、電圧Ｖｇに混入したノイズをフィルタ回路５によって好適に取り除くことができた。その結果、誤差の少ない検出電圧Ｖｏを出力する静電容量センサ回路１を提供することができた。 (5) According to the present embodiment, the transmitter Vc of the capacitance sensor circuit 1 is, for example, a sine wave transmission circuit. Therefore, the noise mixed in the voltage Va, the voltage Vb, and the voltage Vg can be suitably removed by the filter circuit 5. As a result, it was possible to provide the capacitance sensor circuit 1 that outputs the detection voltage Vo with little error.
（６）本実施形態によれば、静電容量センサ回路１は整流回路４とフィルタ回路５を備えた。従って、ノイズを好適に除去できた検出電圧Ｖｏを出力できると共に、検出電圧Ｖｏをその後の利用が容易な直流成分として出力をすることができた。その結果、静電容量センサ回路１の検出電圧Ｖｏを誤差の少なく、利用を容易にすることができた。 (6) According to the present embodiment, the capacitance sensor circuit 1 includes the rectifier circuit 4 and the filter circuit 5. Therefore, it is possible to output the detection voltage Vo from which noise can be suitably removed, and to output the detection voltage Vo as a DC component that can be easily used thereafter. As a result, the detection voltage Vo of the capacitance sensor circuit 1 can be easily used with little error.
（７）本実施形態によれば、検出電極２が非検出状態の場合は、検出電圧Ｖｏは０Ｖであり、検出状態の場合に検出電圧Ｖｏに電圧が発生するようにした。従って、非検出状態と検出状態の区別を検出電圧Ｖｏの電圧から非常に容易にできる。その結果、検出状態、非検出状態の判断の誤りの少ない、かつ、判断のための回路の調整を非常に容易とすることができる静電容量センサ回路１を提供することができる。 (7) According to the present embodiment, when the detection electrode 2 is in the non-detection state, the detection voltage Vo is 0 V, and when the detection electrode 2 is in the detection state, a voltage is generated in the detection voltage Vo. Therefore, the non-detection state and the detection state can be distinguished very easily from the voltage of the detection voltage Vo. As a result, it is possible to provide the capacitance sensor circuit 1 in which the detection state / non-detection state determination error is small and the adjustment of the circuit for determination can be made very easy.
（８）本実施形態によれば、コンデンサＣｏの両端の電圧Ｖａと電圧Ｖｂの差分を差動増幅回路３で増幅する。従って、気温や湿度による他の構成要素の影響を抑制することができた。又、比較のための基準電圧源なども省略することができた。その結果、気温や湿度の変化にも影響を受けづらく、構成部品の少ない静電容量センサ回路１を構成することができた。 (8) According to this embodiment, the differential amplifier 3 amplifies the difference between the voltage Va and the voltage Vb across the capacitor Co. Therefore, the influence of other components due to temperature and humidity could be suppressed. Also, a reference voltage source for comparison could be omitted. As a result, it was possible to configure the capacitance sensor circuit 1 that is not easily affected by changes in temperature and humidity and has few components.
（９）本実施形態によれば、電圧Ｖａと電圧Ｖｂの差は式（２）のように求められるので、コンデンサＣｏと検出容量Ｃの比率を調整して、検出感度を調整することができた。例えば、コンデンサＣｏの静電容量が検出容量Ｃの静電容量と比べて十分に小さければ、感度はほぼ「１」であり、コンデンサＣｏが検出容量Ｃと同じであれば、感度は１／２となる。その結果、容易に感度調整が行える静電容量センサ回路１を構成することができた。 (9) According to the present embodiment, the difference between the voltage Va and the voltage Vb can be obtained as shown in Equation (2). Therefore, the detection sensitivity can be adjusted by adjusting the ratio of the capacitor Co and the detection capacitor C. It was. For example, if the capacitance of the capacitor Co is sufficiently smaller than the capacitance of the detection capacitor C, the sensitivity is almost “1”, and if the capacitor Co is the same as the detection capacitor C, the sensitivity is 1/2. It becomes. As a result, it was possible to configure the capacitance sensor circuit 1 that can easily adjust the sensitivity.
尚、実施の形態は以下のように変更してもよい。
・上記実施形態では、検出電極２には人体が直接触れることとしたが、検出電極２に静電容量の変化が生じるのであれば、検出電極２は、例えば、合成樹脂フィルムで覆われていてもよい。そうすれば、対気候性、対環境性のある検出電極２を提供することができる。
The embodiment may be changed as follows.
In the above embodiment, the human body directly touches the detection electrode 2. However, if the capacitance of the detection electrode 2 changes, the detection electrode 2 is covered with, for example, a synthetic resin film. Also good. By doing so, it is possible to provide the detection electrode 2 having climate resistance and environmental resistance.
・上記実施形態では、発信器Ｖｃは交流信号発信器、例えば、正弦波発信器とした。しかしこれに限らず、他の波形の発信器、例えば、パルス発信器、三角波発信器でもよい。又、直流電源でもよい。そうすれば、回路特性や設置状況に応じた好適な発信器を静電容量センサ回路１に用いることができる。 In the above embodiment, the transmitter Vc is an AC signal transmitter, for example, a sine wave transmitter. However, the present invention is not limited to this, and other waveform transmitters such as a pulse transmitter and a triangular wave transmitter may be used. A DC power supply may also be used. Then, a suitable transmitter according to circuit characteristics and installation conditions can be used for the capacitance sensor circuit 1.
・上記実施形態では、整流回路４とフィルタ回路５からなる信号調整回路を設けた。しかしこれに限らず、信号整流回路は、その他の回路を含んでもよい。又、整流回路４とフィルタ回路５とその他の回路の少なくとも一つの構成であってもよい。そうすれば、差動増幅回路３の出力する電圧Ｖｇを好適に調整する信号調整回路を設けることができる。 In the above embodiment, the signal adjustment circuit including the rectifier circuit 4 and the filter circuit 5 is provided. However, the present invention is not limited to this, and the signal rectifier circuit may include other circuits. Further, at least one configuration of the rectifier circuit 4, the filter circuit 5, and other circuits may be employed. Then, a signal adjustment circuit that suitably adjusts the voltage Vg output from the differential amplifier circuit 3 can be provided.
・上記実施形態では、信号調整回路を設けたが、これを省略しても良い。そうすれば、差動増幅回路３の出力する電圧Ｖｇを自由に処理することができる。
・上記実施形態では、検出容量ＣとコンデンサＣｏの静電容量の関係はどのような関係でもよい。しかし、特に検出容量Ｃの静電容量に比べてコンデンサＣｏの静電容量を十分小さくすれば、外部出力端子６の検出電圧Ｖｏは式（５）のようにみなすことができる。そうすれば、より調整に煩わされない静電容量センサ回路１を提供することができる。
In the above embodiment, the signal adjustment circuit is provided, but this may be omitted. Then, the voltage Vg output from the differential amplifier circuit 3 can be freely processed.
In the above embodiment, the relationship between the detection capacitance C and the capacitance of the capacitor Co may be any relationship. However, if the capacitance of the capacitor Co is made sufficiently smaller than the capacitance of the detection capacitor C in particular, the detection voltage Vo at the external output terminal 6 can be regarded as shown in Expression (5). If it does so, the electrostatic capacitance sensor circuit 1 which is not bothered by adjustment can be provided.
検出電圧Ｖｏ∝（Ａ×Ｇ｜Ｖａ｜）・・・（５）
・上記実施形態では、検出電極２に人体が触れることで生じる静電容量の変化により検出状態を検出することとした。しかし、静電容量センサ回路１は、検出電極２にどのような手段で静電容量の変化があっても、検出状態であるか否かを検出することができるように構成しても良い。
Detection voltage Vo∝ (A × G | Va |) (5)
In the embodiment described above, the detection state is detected by a change in capacitance that occurs when the human body touches the detection electrode 2. However, the capacitance sensor circuit 1 may be configured to detect whether or not the detection electrode 2 is in a detection state regardless of the change in the capacitance of the detection electrode 2.
例えば、オイルケース内に収容された液状の静電容量媒体と、前記静電容量媒体に浸漬された部分によりコンデンサを構成する差動電極及び共通電極を備える。さらに、前記オイルケースの傾きに応じて移動する静電容量媒体により変化するコンデンサの容量に基づいて傾きを検出するようにした静電容量式傾斜角センサにおいて、静電容量媒体により変化するコンデンサの容量を検出するために用いてもよい。そうすれば、静電容量傾斜センサにも周波数の影響が少ない静電容量センサ回路１を備えることができる。 For example, a liquid capacitive medium housed in an oil case, and a differential electrode and a common electrode constituting a capacitor by a portion immersed in the capacitive medium are provided. Furthermore, in the capacitance type inclination angle sensor that detects the inclination based on the capacitance of the capacitor that changes depending on the capacitance medium that moves according to the inclination of the oil case, the capacitance of the capacitor that changes depending on the capacitance medium It may be used to detect the capacity. By doing so, the capacitance inclination sensor can also be provided with the capacitance sensor circuit 1 that is less affected by the frequency.
Ｃ…検出容量、Ｃｏ…コンデンサ、Ｒｏ…抵抗、Ｖａ、Ｖｂ、Ｖｇ…電圧、Ｖｃ…発信器、Ｖｏ…検出電圧、１…静電容量センサ回路、２…検出電極、３…差動増幅回路、４…整流回路、５…フィルタ回路、６…外部出力端子。
C: Detection capacitance, Co: Capacitor, Ro: Resistance, Va, Vb, Vg ... Voltage, Vc ... Transmitter, Vo ... Detection voltage, 1 ... Capacitance sensor circuit, 2 ... Detection electrode, 3 ... Differential amplification circuit 4, rectifier circuit, 5 ... filter circuit, 6 ... external output terminal.
Claims (5)
前記抵抗と前記検出電極との間に接続したコンデンサと、
前記コンデンサの前記抵抗側の電圧と、前記コンデンサの前記検出電極側の電圧との差の電圧を増幅する増幅回路と
を備えたことを特徴とする静電容量センサ回路。 In a capacitance sensor circuit that applies a transmission signal output from a transmitter to a detection electrode via a resistor and detects a change in capacitance of the detection electrode.
A capacitor connected between the resistor and the detection electrode;
An electrostatic capacitance sensor circuit comprising: an amplifier circuit that amplifies a voltage difference between the voltage on the resistance side of the capacitor and the voltage on the detection electrode side of the capacitor.
前記増幅回路は、差動増幅回路であることを特徴とする静電容量センサ回路。 The capacitance sensor circuit according to claim 1,
The capacitance sensor circuit, wherein the amplification circuit is a differential amplification circuit.
前記増幅回路の出力端子には整流回路が接続され、前記増幅回路からの検出信号を前記整流回路を介して出力させることを特徴とする静電容量センサ回路。 The capacitance sensor circuit according to claim 1 or 2,
A rectifier circuit is connected to an output terminal of the amplifier circuit, and a detection signal from the amplifier circuit is output via the rectifier circuit.
前記整流回路の出力端子にはフィルタ回路が接続され、前記整流回路からの検出信号を前記フィルタ回路を介して出力させることを特徴とする静電容量センサ回路。 The capacitance sensor circuit according to claim 3,
A filter circuit is connected to an output terminal of the rectifier circuit, and a detection signal from the rectifier circuit is output via the filter circuit.
前記コンデンサの静電容量は、検出電極の静電容量よりも十分小さい静電容量を有することを特徴とする静電容量センサ回路。
In the capacitance sensor circuit according to any one of claims 1 to 4,
The capacitance sensor circuit according to claim 1, wherein the capacitance of the capacitor is sufficiently smaller than the capacitance of the detection electrode.
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| WO2011149750A2 (en) | 2010-05-25 | 2011-12-01 | 3M Innovative Properties Company | High speed low power multi-touch touch device and controller therefor |
| US9389724B2 (en) | 2010-09-09 | 2016-07-12 | 3M Innovative Properties Company | Touch sensitive device with stylus support |
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| US8890841B2 (en) | 2013-03-13 | 2014-11-18 | 3M Innovative Properties Company | Capacitive-based touch apparatus and method therefor, with reduced interference |
| WO2020027026A1 (en) * | 2018-07-30 | 2020-02-06 | 日本電産株式会社 | Measurement device and measurement method |
| JP2021129262A (en) * | 2020-02-17 | 2021-09-02 | ソニーセミコンダクタソリューションズ株式会社 | Touch sensor device and electronic device including the same |
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| JPH06140902A (en) * | 1992-10-26 | 1994-05-20 | Mitsubishi Electric Home Appliance Co Ltd | Input device for equipment |
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Also Published As
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| JP2007334690A (en) | 2007-12-27 |
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