JP4281124B2

JP4281124B2 - Peak detector

Info

Publication number: JP4281124B2
Application number: JP21091798A
Authority: JP
Inventors: 一夫栗原
Original assignee: Sony Corp
Current assignee: Sony Corp
Priority date: 1998-07-27
Filing date: 1998-07-27
Publication date: 2009-06-17
Anticipated expiration: 2018-07-27
Also published as: JP2000046876A

Description

【０００１】
【発明の属する技術分野】
本発明は、各種センサの検出手段等に用いられるピーク検波器に関し、特に簡単な構造で低価格化を図った新規なピーク検波器に関するものである。
【０００２】
【従来の技術】
従来より、各種センサの検出手段としてピーク検波器が広く使用されている。例えば、フラックスゲートセンサを用いた磁気探知装置にオペアンプを使用したピーク検波器が使用されている。
フラックスゲート・センサを用いた磁気探知装置は、図３に示すように、微弱磁界の中でもヒステリシス曲線がシフトする特殊な高透磁率材料からなる環状の磁気コア１０に、励磁用コイル２０及び検出用コイル３０を巻回した構成のものである。
この磁気探知装置で外部磁界を検出するには、環状の磁気コア１０を過飽和状態に励磁するような交流電流を励磁用コイル２０に流す。
ここで、外部磁界が磁気コア１０に作用しなければ、検出用コイル３０の左右のコイル３０Ａ、３０Ｂからの出力は同じ出力波形となる。そして、左右のコイル３０Ａ、３０Ｂは逆相に接続されているので、各々の出力は互いに打ち消し合い、検出用コイル３０全体からは何も出力されない。
【０００３】
一方、例えば、励磁用コイル２０によって右回りの磁束Ｂが磁気コア１０内に発生しているときに、ＮからＳ方向に外部磁界Ｈｅを加えると、外部磁界Ｈｅがバイアス磁界として作用するため、磁気コア１０の右側は早く飽和し、左側は逆に遅れて飽和する。
このため、検出用コイル３０の左右のコイル３０Ａ、３０Ｂは逆相に接続されているので、各々の出力の差分の電圧が外部磁界Ｈｅの大きさに応じて出力される。
そして、このようなセンサに用いられる検出回路は、磁気コア１０内に発生する磁束Ｂが右回りのときに検出用コイル３０に発生する出力のピーク電圧値と、磁東Ｂが左回りのときに検出用コイル３０に発生する出力のピーク電圧値とを検出し、それらのピーク電圧値を差動増幅することによって検出を行うものである。
【０００４】
図２は、このようなピーク検波器を用いた検出回路の従来例を示す回路図である。
この検出回路は、それぞれオペアンプを使用して構成した一般的なピーク検波部４０Ａ、４０Ｂと差動増幅部５０とで構成される。
そして、ピーク検波部４０Ａは、交流信号を入力する第１のオペアンプ４２Ａと、この第１のオペアンプ４２Ａからの出力信号のピーク検波を行う第１のピーク検波回路４４Ａと、この第１のピーク検波回路４４Ａからのピーク検出値を差動増幅部５０に出力する第２のオペアンプ４６Ａとを有する。
【０００５】
また、ピーク検波部４０Ｂは、交流信号を入力する第３のオペアンプ４２Ｂと、この第３のオペアンプ４２Ｂからの出力信号のピーク検波を行う第２のピーク検波回路４４Ｂと、この第２のピーク検波回路４４Ｂからのピーク検出値を差動増幅部５０に出力する第４のオペアンプ４６Ｂとを有する。
また、差動増幅部５０は、ピーク検波部４０Ａ、４０Ｂの各オペアンプ４６Ａ、４６Ｂからの出力電圧の差分を検出し、検出信号を出力する第５のオペアンプ５２を有する。
【０００６】
【発明が解決しようとする課題】
しかしながら、上述した従来のピーク検波器では、５つのオペアンプ４２Ａ、４２Ｂ、４６Ａ、４６Ｂ、５２を使用して構成されるため、低価格化が困難であるという問題があった。
【０００７】
そこで本発明の目的は、使用するオペアンプの数を減らすことができ、低価格化が容易なピーク検波器を提供することにある。
【０００８】
【課題を解決するための手段】
本発明は前記目的を達成するため、第１の入力信号を検波する第１のピーク検波部と、第２の入力信号を検波する第２のピーク検波部と、前記第１のピーク検波部が検波した検波信号と前記第２のピーク検波部が検波した検波信号との差分を検出信号として出力する差分検出部とを備えたピーク検波器であって、前記第２のピーク検波部の出力段に設けられた第２のオペアンプとによって前記差分検出部が構成され、前記第１のピーク検波部は、第１のオペアンプと、第１のピーク検波回路と、第２のオペアンプとを有し、前記第１のオペアンプの出力部が前記第１のピーク検波回路の入力部に接続され、前記第１のピーク検波回路の出力部が前記第２のオペアンプの正入力部に接続され、前記第２のオペアンプの出力部が第１の抵抗を通して第１のオペアンプと第２のオペアンプの負入力部に接続され、前記第２のピーク検波部は、第３のオペアンプと、第２のピーク検波回路と、第４のオペアンプとを有し、前記第３のオペアンプの出力部が前記第２のピーク検波回路の入力部に接続され、前記第２のピーク検波回路の出力部が第４のオペアンプの正入力部に接続され、前記第４のオペアンプの出力部が第３の抵抗を通して第３のオペアンプと第４のオペアンプの負入力部と第４の抵抗の一方の端子に接続され、前記第４の抵抗の他方の端子は基準電位に接続され、さらに前記差分検出部では、前記第２のピーク検波部の第４のオペアンプの出力部が第２の抵抗を通して前記第１のピーク検波部の第１のオペアンプと第２のオペアンプの負入力部に接続され、前記第１のオペアンプと前記第３のオペアンプの正入力部に入力された信号の各ピーク電圧値を検出し、前記各ピーク電圧値を差動増幅した信号を前記第２のオペアンプより出力するようにしたことを特徴とする。
【０００９】
具体的には、前記第１のピーク検波部は、第１のオペアンプと第１のピーク検波回路と第２のオペアンプとを有し、前記第１のオペアンプの出力端子が前記第１のピーク検波回路の入力端子に接続され、前記第１のピーク検波回路の出力端子が前記第２のオペアンプの正入力端子に接続され、前記第２のオペアンプの出力端子が第１の抵抗を通して第１のオペアンプと第２のオペアンプの負入力端子に接続されるように構成する。
【００１０】
また、前記第２のピーク検波部は、第３のオペアンプと第２のピーク検波回路と第４のオペアンプとを有し、前記第３のオペアンプの出力端子が前記第２のピーク検波回路の入力端子に接続され、前記第２のピーク検波回路の出力端子が第４のオペアンプの正入力端子に接続され、前記第４のオペアンプの出力端子が第３の抵抗を通して第３のオペアンプと第４のオペアンプの負入力端子と第４の抵抗の一方の端子に接続され、前記第４の抵抗の他方の端子は基準電位に接続されるように構成する。
さらに前記差動増幅部では、前記第２のピーク検波部の第４のオペアンプの出力端子が第２の抵抗を通して前記第１のピーク検波部の第１のオペアンプと第２のオペアンプの負入力端子に接続されるように構成する。
【００１１】
これにより、前記第１のオペアンプと前記第３のオペアンプの正入力端子に入力された信号の各ピーク電圧値を検出し、各ピーク電圧値を差動増幅した信号を前記第２のオペアンプより出力するようにして、ピーク検波部と差動増幅部とを一体型にすることによって、オペアンプを４個で構成することができ、従来に比してオペアンプの数を１つ減少できる。
【００１２】
【発明の実施の形態】
以下、本発明によるピーク検波器の実施の形態について説明する。なお、本発明は、以下の例に限定されるものではなく、本発明の要旨を逸脱しない範囲で変更が可能であることは言うまでもない。
図１は、本発明によるピーク検波器の構成例を示す回路図である。
このピーク検波器は、第１の入力信号Ｖｉ１を検波する第１のピーク検波部と、第２の入力信号Ｖｉ２を検波する第２のピーク検波部と、各ピーク検波部による各検波信号の差分に基づいて検出信号を出力する差動増幅部とを有し、各ピーク検波部と差動増幅部とを一体化して構成したものである。
【００１３】
図１において、第１のピーク検波部は、第１のオペアンプ６０Ａ、第１のピーク検波回路７０Ａ、第２のオペアンプ６０Ｂ、及び第１の抵抗８０Ａにより構成されている。
同様に、第２のピーク検波部は、第３のオペアンプ６０Ｃ、第２のピーク検波回路７０Ｂ、第４のオペアンプ６０Ｄ、及び第３の抵抗８０Ｃにより構成されている。
また、差動増幅部は、第２のオペアンプ６０Ｂ、第４のオペアンプ６０Ｄ、及び第１〜第４の抵抗８０Ａ、８０Ｂ、８０Ｃ、８０Ｄにより構成されている。
【００１４】
第１のピーク検波部において、第１のオペアンプ６０Ａの出力端子が第１のピーク検波回路７０Ａの入力端子に接続され、この第１のピーク検波回路７０Ａの出力端子が第２のオペアンプ６０Ｂの正入力端子に接続され、この第２のオペアンプ６０Ｂの出力端子が第１の抵抗８０Ａを通して第１のオペアンプ６０Ａと第２のオペアンプ６０Ｂの負入力端子に接続されている。
また、第２のピーク検波部において、第３のオペアンプ６０Ｃの出力端子が第２のピーク検波回路７０Ｂの入力端子に接続され、この第２のピーク検波回路７０Ｂの出力端子が第４のオペアンプ６０Ｄの正入力端子に接続され、この第４のオペアンプ６０Ｄの出力端子が第３の抵抗８０Ｃを通して第３のオペアンプ６０Ｃと第４のオペアンプ６０Ｄの負入力端子と第４の抵抗８０Ｄに接続され、この第４の抵抗８０Ｄの他方の端子が基準電源９０に接続されている。
【００１５】
また、差動増幅部において、第２のピーク検波部の第４のオペアンプ６０Ｄの出力端子が第２の抵抗８０Ｂを通して第１のピーク検波部の第１のオペアンプ６０Ａと第２のオペアンプ６０Ｂの負入力端子に接続されている。
このようなピーク検波器の入力端子は、第１のオペアンプ６０Ａと第３のオペアンプ６０Ｃの正入力端子である。
すなわち、第１のオペアンプ６０Ａの正入力端子に交流信号Ｖｉ１を加え、第３のオペアンプ６０Ｃの正入力端子に交流信号Ｖｉ２を加えると、第１のピーク検波回路７０Ａでは、交流信号Ｖｉ１のピーク値を検出して電圧値Ｖｐ１を出力端子し、第２のピーク検波回路７０Ｂでは、交流信号Ｖｉ２のピーク値を検出して電圧値Ｖｐ２を出力する。
一方、このピーク検波器の出力端子は、第２のオペアンプ６０Ｂの出力端子である。この端子からピーク電圧値Ｖｐ１、Ｖｐ２を差動増幅した信号Ｖｏが出力端子される。
【００１６】
次に、ピーク検波回路７０Ａの動作原理について説明する。
図１に示すように、ピーク検波回路７０Ａは、ダイオード（スイッチング手段Ｓ）７０ＡＡ、抵抗（放電手段）７０ＡＢ、及びコンデンサ（充電手段）７０ＡＣによって構成されている。
交流信号Ｖｉ１がピーク値になったときに、ダイオード７０ＡＡを通してコンデンサ７０ＡＣが充電されて、ピーク電圧値Ｖｐ１が保持される。
次に、交流信号Ｖｉ１がピーク値より低いときには、コンデンサ７０ＡＣに保持された電圧によりダイオード７０ＡＡがオフとなり、コンデンサ７０ＡＣの電荷は抵抗７０ＡＢを通して大きな時定数で放電される。
ここで、ピーク検波回路７０Ａで検出した電圧値Ｖｐ１と交流信号Ｖｉ１のピーク値とが一致するのは、オペアンプ６０Ａとピーク検波回路７０Ａとオペアンプ６０Ｂと抵抗８０Ａによる負帰還ループが構成されているためである。
したがって、オペアンプ６０Ａとオペアンプ６０Ｂの負入力端子は電圧値Ｖｐ１となる。
【００１７】
また、ピーク検波回路７０Ｂ（ダイオード７０ＢＡ、抵抗７０ＢＢ、及びコンデンサ７０ＢＣ）の動作原理も同様であり、オペアンプ６０Ｃとオペアンプ６０Ｄの負入力端子は電圧値Ｖｐ２となる。
そして、これらのピーク電圧値Ｖｐ１、Ｖｐ２の差動増幅は、オペアンプ６０Ｂ、オペアンプ６０Ｄ、及び抵抗８０Ａ、８０Ｂ、８０Ｃ、８０Ｄによって行われる。
ここで、抵抗８０Ａと抵抗８０Ｄの値をＲｏとし、抵抗８０Ｂと抵抗８０Ｃの値をＲｉとし、基準電源９の値をＶｒとすると、ピーク検波器の出力信号Ｖｏは、次の式（１）のように表される。
Ｖｏ＝（Ｒｏ／Ｒｉ＋１）（Ｖｐ１−Ｖｐ２）＋Ｖｒ …… （１）
上述のように、このピーク検波器の出力端子は第２のオペアンプ６０Ｂの出力端子であり、この出力端子からピーク電圧値Ｖｐ１、Ｖｐ２を差動増幅した信号Ｖｏが出力される。
【００１８】
したがって、本例のピーク検波器によれば、ピーク検波部と差動増幅部とを一体化することにより、オペアンプを４つで構成でき、上述した従来のピーク検波器に比してオペアンプを１つ減らすことができ、ピーク検波器の低価格化を図ることができる。
なお、上述の例では、ピーク検波回路７０Ａは、ダイオード７０ＡＡと抵抗７０ＡＢとコンデンサ７０ＡＣによって構成したが、抵抗７０ＡＢの代わりに電流源によりコンデンサ７０ＡＣの電荷を放電するようにしてもよい。また、ダイオード７０ＡＡをトランジスタで代用できることは言うまでもない。
また、本例のピーク検波器は、上述したフラックスゲートセンサを用いた磁気探知装置に限らず、各種の検出装置に広く応用し得るものである。
【００１９】
以上説明したように本発明のピーク検波器では、第１の入力信号を検波する第１のピーク検波部と、第２の入力信号を検波する第２のピーク検波部と、各ピーク検波部による各検波信号の差分に基づいて検出信号を出力する差分検出部とを有するピーク検波器において、第１のピーク検波部の出力段に設けられたオペアンプと第２のピーク検波部の出力段に設けられたオペアンプとによって差分検出部を構成した。したがって、ピーク検波部と差分検出部とを一体化することにより、オペアンプの数を減らすことができ、ピーク検波器の低価格化を図ることができる。
【図面の簡単な説明】
【図１】本発明によるピーク検波器の構成例を示す回路図である。
【図２】従来のピーク検波器の構成例を示す回路図である。
【図３】従来のピーク検波器を用いた磁気探知装置の磁気回路の構成例を示す正面図である。
【符号の説明】
６０Ａ、６０Ｂ、６０Ｃ、６０Ｄ……オペアンプ、７０Ａ、７０Ｂ……第１のピーク検波回路、７０ＡＢ、７０ＢＢ、８０Ａ、８０Ｂ、８０Ｃ、８０Ｄ……抵抗、７０ＡＡ、７０ＢＡ……ダイオード、７０ＡＣ、７０ＢＣ……コンデンサ、９０……基準電源。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a peak detector used for detection means of various sensors, and more particularly to a novel peak detector that is simple in structure and reduced in price.
[0002]
[Prior art]
Conventionally, peak detectors have been widely used as detection means for various sensors. For example, a peak detector using an operational amplifier is used in a magnetic detector using a fluxgate sensor.
As shown in FIG. 3, a magnetic detector using a fluxgate sensor has an annular magnetic core 10 made of a special high permeability material whose hysteresis curve shifts even in a weak magnetic field, an excitation coil 20 and a detection coil. The coil 30 is wound around.
In order to detect an external magnetic field with this magnetic detector, an alternating current that excites the annular magnetic core 10 into a supersaturated state is passed through the exciting coil 20.
Here, if the external magnetic field does not act on the magnetic core 10, the outputs from the left and right coils 30A and 30B of the detection coil 30 have the same output waveform. Since the left and right coils 30A and 30B are connected in opposite phases, their outputs cancel each other, and nothing is output from the entire detection coil 30.
[0003]
On the other hand, for example, when an external magnetic field He is applied in the S direction from N when the clockwise magnetic flux B is generated in the magnetic core 10 by the exciting coil 20, the external magnetic field He acts as a bias magnetic field. The right side of the magnetic core 10 is saturated early, and the left side is saturated later.
For this reason, since the left and right coils 30A and 30B of the detection coil 30 are connected in opposite phases, a difference voltage between the respective outputs is output according to the magnitude of the external magnetic field He.
The detection circuit used for such a sensor has a peak voltage value of the output generated in the detection coil 30 when the magnetic flux B generated in the magnetic core 10 is clockwise, and when the magnetic east B is counterclockwise. The detection is performed by detecting the peak voltage value of the output generated in the detection coil 30 and differentially amplifying the peak voltage value.
[0004]
FIG. 2 is a circuit diagram showing a conventional example of a detection circuit using such a peak detector.
The detection circuit includes general peak detection units 40A and 40B and a differential amplification unit 50, each of which is configured using an operational amplifier.
The peak detection unit 40A includes a first operational amplifier 42A that receives an AC signal, a first peak detection circuit 44A that performs peak detection of an output signal from the first operational amplifier 42A, and the first peak detection. And a second operational amplifier 46A that outputs the peak detection value from the circuit 44A to the differential amplifier 50.
[0005]
The peak detection unit 40B includes a third operational amplifier 42B that receives an AC signal, a second peak detection circuit 44B that performs peak detection of an output signal from the third operational amplifier 42B, and the second peak detection. A fourth operational amplifier 46B that outputs the peak detection value from the circuit 44B to the differential amplifier 50;
The differential amplifying unit 50 includes a fifth operational amplifier 52 that detects a difference between output voltages from the operational amplifiers 46A and 46B of the peak detection units 40A and 40B and outputs a detection signal.
[0006]
[Problems to be solved by the invention]
However, since the above-described conventional peak detector is configured using the five operational amplifiers 42A, 42B, 46A, 46B, and 52, there is a problem that it is difficult to reduce the price.
[0007]
Accordingly, an object of the present invention is to provide a peak detector that can reduce the number of operational amplifiers to be used and can be easily reduced in price.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a first peak detection unit for detecting a first input signal, a second peak detection unit for detecting a second input signal, and the first peak detection unit. A peak detector comprising a difference detection unit that outputs a difference between a detection signal detected and a detection signal detected by the second peak detection unit as a detection signal, and an output stage of the second peak detection unit The difference detection unit is configured by a second operational amplifier provided in the first operational amplifier, and the first peak detection unit includes a first operational amplifier, a first peak detection circuit, and a second operational amplifier. The output section of the first operational amplifier is connected to the input section of the first peak detection circuit, the output section of the first peak detection circuit is connected to the positive input section of the second operational amplifier, and the second operational amplifier The output of the op amp through the first resistor The second operational amplifier is connected to the negative input section of the first operational amplifier and the second operational amplifier, and the second peak detection section includes a third operational amplifier, a second peak detection circuit, and a fourth operational amplifier, An output section of a third operational amplifier is connected to an input section of the second peak detection circuit, an output section of the second peak detection circuit is connected to a positive input section of a fourth operational amplifier, and the fourth operational amplifier Is connected to the negative input of the third operational amplifier, the fourth operational amplifier, and one terminal of the fourth resistor through the third resistor, and the other terminal of the fourth resistor is connected to the reference potential. Further, in the difference detection unit, the output unit of the fourth operational amplifier of the second peak detection unit passes through the second resistor and the first operational amplifier of the first peak detection unit and the negative input unit of the second operational amplifier. Connected to the first pair Detects each peak voltage value of the input signal to the positive input of flop and said third operational amplifier, in that the signal of each peak voltage value and the differential amplifier and to output from the second operational amplifier Features.
[0009]
Specifically, the first peak detection unit includes a first operational amplifier, a first peak detection circuit, and a second operational amplifier, and an output terminal of the first operational amplifier is the first peak detection. Connected to the input terminal of the circuit, the output terminal of the first peak detection circuit is connected to the positive input terminal of the second operational amplifier, and the output terminal of the second operational amplifier is connected to the first operational amplifier through the first resistor. And connected to the negative input terminal of the second operational amplifier.
[0010]
The second peak detection unit includes a third operational amplifier, a second peak detection circuit, and a fourth operational amplifier, and an output terminal of the third operational amplifier is an input of the second peak detection circuit. The output terminal of the second operational amplifier is connected to the positive input terminal of the fourth operational amplifier, and the output terminal of the fourth operational amplifier is connected to the third operational amplifier and the fourth through the third resistor. The operational amplifier is connected to a negative input terminal and one terminal of a fourth resistor, and the other terminal of the fourth resistor is connected to a reference potential.
Further, in the differential amplifier section, the output terminal of the fourth operational amplifier of the second peak detection section is connected to the first operational amplifier of the first peak detection section and the negative input terminal of the second operational amplifier through a second resistor. To be connected to.
[0011]
As a result, each peak voltage value of the signals input to the positive input terminals of the first operational amplifier and the third operational amplifier is detected, and a signal obtained by differentially amplifying each peak voltage value is output from the second operational amplifier. Thus, by integrating the peak detection unit and the differential amplification unit, four operational amplifiers can be formed, and the number of operational amplifiers can be reduced by one as compared with the conventional one.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of a peak detector according to the present invention will be described. Needless to say, the present invention is not limited to the following examples, and modifications can be made without departing from the scope of the present invention.
FIG. 1 is a circuit diagram showing a configuration example of a peak detector according to the present invention.
The peak detector includes a first peak detection unit that detects the first input signal Vi1, a second peak detection unit that detects the second input signal Vi2, and a difference between the detection signals by the peak detection units. And a differential amplifying unit that outputs a detection signal based on the above, and each peak detection unit and the differential amplifying unit are integrated.
[0013]
In FIG. 1, the first peak detection unit includes a first operational amplifier 60A, a first peak detection circuit 70A, a second operational amplifier 60B, and a first resistor 80A.
Similarly, the second peak detection unit includes a third operational amplifier 60C, a second peak detection circuit 70B, a fourth operational amplifier 60D, and a third resistor 80C.
The differential amplifier section includes a second operational amplifier 60B, a fourth operational amplifier 60D, and first to fourth resistors 80A, 80B, 80C, and 80D.
[0014]
In the first peak detection unit, the output terminal of the first operational amplifier 60A is connected to the input terminal of the first peak detection circuit 70A, and the output terminal of the first peak detection circuit 70A is the positive terminal of the second operational amplifier 60B. The output terminal of the second operational amplifier 60B is connected to the negative input terminals of the first operational amplifier 60A and the second operational amplifier 60B through the first resistor 80A.
In the second peak detection unit, the output terminal of the third operational amplifier 60C is connected to the input terminal of the second peak detection circuit 70B, and the output terminal of the second peak detection circuit 70B is the fourth operational amplifier 60D. And the output terminal of the fourth operational amplifier 60D is connected to the third operational amplifier 60C, the negative input terminal of the fourth operational amplifier 60D, and the fourth resistor 80D through the third resistor 80C. The other terminal of the fourth resistor 80D is connected to the reference power supply 90.
[0015]
Further, in the differential amplifier, the output terminal of the fourth operational amplifier 60D of the second peak detector is connected to the negative terminal of the first operational amplifier 60A and the second operational amplifier 60B of the first peak detector through the second resistor 80B. Connected to the input terminal.
The input terminals of such a peak detector are the positive input terminals of the first operational amplifier 60A and the third operational amplifier 60C.
That is, when the AC signal Vi1 is applied to the positive input terminal of the first operational amplifier 60A and the AC signal Vi2 is applied to the positive input terminal of the third operational amplifier 60C, the peak value of the AC signal Vi1 is obtained in the first peak detection circuit 70A. Is detected and the voltage value Vp1 is output, and the second peak detection circuit 70B detects the peak value of the AC signal Vi2 and outputs the voltage value Vp2.
On the other hand, the output terminal of this peak detector is the output terminal of the second operational amplifier 60B. A signal Vo obtained by differentially amplifying the peak voltage values Vp1 and Vp2 is output from this terminal.
[0016]
Next, the operation principle of the peak detection circuit 70A will be described.
As shown in FIG. 1, the peak detection circuit 70A includes a diode (switching means S) 70AA, a resistor (discharge means) 70AB, and a capacitor (charging means) 70AC.
When the AC signal Vi1 reaches the peak value, the capacitor 70AC is charged through the diode 70AA, and the peak voltage value Vp1 is maintained.
Next, when the AC signal Vi1 is lower than the peak value, the diode 70AA is turned off by the voltage held in the capacitor 70AC, and the charge of the capacitor 70AC is discharged through the resistor 70AB with a large time constant.
Here, the reason why the voltage value Vp1 detected by the peak detection circuit 70A matches the peak value of the AC signal Vi1 is that a negative feedback loop is constituted by the operational amplifier 60A, the peak detection circuit 70A, the operational amplifier 60B, and the resistor 80A. It is.
Therefore, the negative input terminals of the operational amplifier 60A and the operational amplifier 60B have the voltage value Vp1.
[0017]
The operation principle of the peak detection circuit 70B (the diode 70BA, the resistor 70BB, and the capacitor 70BC) is the same, and the negative input terminals of the operational amplifier 60C and the operational amplifier 60D have the voltage value Vp2.
The differential amplification of these peak voltage values Vp1 and Vp2 is performed by the operational amplifier 60B, the operational amplifier 60D, and the resistors 80A, 80B, 80C, and 80D.
Here, assuming that the values of the resistors 80A and 80D are Ro, the values of the resistors 80B and 80C are Ri, and the value of the reference power supply 9 is Vr, the output signal Vo of the peak detector is expressed by the following equation (1). It is expressed as
Vo = (Ro / Ri + 1) (Vp1-Vp2) + Vr (1)
As described above, the output terminal of the peak detector is the output terminal of the second operational amplifier 60B, and a signal Vo obtained by differentially amplifying the peak voltage values Vp1 and Vp2 is output from the output terminal.
[0018]
Therefore, according to the peak detector of this example, the operational amplifier can be constituted by four by integrating the peak detection unit and the differential amplification unit, and the operational amplifier is 1 in comparison with the above-described conventional peak detector. The cost of the peak detector can be reduced.
In the above-described example, the peak detection circuit 70A is configured by the diode 70AA, the resistor 70AB, and the capacitor 70AC. However, instead of the resistor 70AB, the charge of the capacitor 70AC may be discharged by a current source. It goes without saying that the diode 70AA can be substituted by a transistor.
The peak detector of this example is not limited to the magnetic detection device using the above-described fluxgate sensor, and can be widely applied to various detection devices.
[0019]
As described above, in the peak detector according to the present invention, the first peak detector for detecting the first input signal, the second peak detector for detecting the second input signal, and the peak detectors are used. In a peak detector having a difference detection unit that outputs a detection signal based on a difference between detection signals, an operational amplifier provided in the output stage of the first peak detection unit and an output stage of the second peak detection unit The difference detection unit is configured by the operational amplifier. Therefore, by integrating the peak detector and the difference detector , the number of operational amplifiers can be reduced, and the price of the peak detector can be reduced.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a configuration example of a peak detector according to the present invention.
FIG. 2 is a circuit diagram showing a configuration example of a conventional peak detector.
FIG. 3 is a front view showing a configuration example of a magnetic circuit of a magnetic detection device using a conventional peak detector.
[Explanation of symbols]
60A, 60B, 60C, 60D: operational amplifier, 70A, 70B ... first peak detection circuit, 70AB, 70BB, 80A, 80B, 80C, 80D ... resistor, 70AA, 70BA ... diode, 70AC, 70BC ... Capacitor, 90 ... reference power supply.

Claims

A first peak detector for detecting a first input signal; a second peak detector for detecting a second input signal; a detection signal detected by the first peak detector; and the second peak. A peak detector including a difference detection unit that outputs a difference from a detection signal detected by the detection unit as a detection signal,
The first peak detection unit includes a first operational amplifier, a first peak detection circuit, and a second operational amplifier, and an output unit of the first operational amplifier is an input of the first peak detection circuit. Is connected to the positive input portion of the second operational amplifier, and the output portion of the second operational amplifier is connected to the first operational amplifier and the second through the first resistor. Connected to the negative input of the op amp
The second peak detection unit includes a third operational amplifier, a second peak detection circuit, and a fourth operational amplifier, and an output unit of the third operational amplifier is an input of the second peak detection circuit. Is connected to the positive input portion of the fourth operational amplifier, and the output portion of the fourth operational amplifier is connected to the third operational amplifier and the fourth through the third resistor. The negative input of the operational amplifier and one terminal of the fourth resistor are connected, the other terminal of the fourth resistor is connected to the reference potential,
Further, in the difference detection unit, the output unit of the fourth operational amplifier of the second peak detection unit passes through the second resistor to the first operational amplifier of the first peak detection unit and the negative input unit of the second operational amplifier. Each peak voltage value of a signal connected to the positive input portion of the first operational amplifier and the third operational amplifier is detected, and a signal obtained by differentially amplifying the peak voltage value is detected by the second operational amplifier. Output,
A peak detector characterized by that.

Each of the peak detection circuits is charged with the output voltage of the first or third operational amplifier to hold a peak voltage value, and between the first or third operational amplifier and the charging means. 2. The peak detector according to claim 1, further comprising switching means for turning off and discharging means for discharging the charging means.

The peak detector according to claim 2, wherein the charging means is a capacitor.

The peak detector according to claim 2, wherein the switching means is a diode.

3. The peak detector according to claim 2, wherein the switching means is a transistor.

3. The peak detector according to claim 2, wherein the discharging means is a resistor connected to a reference potential.

The peak detector according to claim 2, wherein the discharging means is a current source.

2. The peak detector according to claim 1, comprising a magnetic detection circuit of a magnetic detector using a fluxgate sensor.