JPH0158462B2 - - Google Patents
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- Publication number
- JPH0158462B2 JPH0158462B2 JP59128511A JP12851184A JPH0158462B2 JP H0158462 B2 JPH0158462 B2 JP H0158462B2 JP 59128511 A JP59128511 A JP 59128511A JP 12851184 A JP12851184 A JP 12851184A JP H0158462 B2 JPH0158462 B2 JP H0158462B2
- Authority
- JP
- Japan
- Prior art keywords
- resistor
- voltage
- circuit
- current
- output
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 238000001514 detection method Methods 0.000 claims description 15
- 238000006243 chemical reaction Methods 0.000 claims description 9
- 238000010586 diagram Methods 0.000 description 7
- 238000009413 insulation Methods 0.000 description 5
- 230000035945 sensitivity Effects 0.000 description 3
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 230000003321 amplification Effects 0.000 description 1
- 239000003990 capacitor Substances 0.000 description 1
- 238000003199 nucleic acid amplification method Methods 0.000 description 1
Description
【発明の詳細な説明】
本発明は、電流検出範囲が広範囲でかつ高感度
を有する高感度電流検出回路に関する。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a highly sensitive current detection circuit having a wide current detection range and high sensitivity.
従来電流検出回路では、たとえば第１図に示す
ようなボルテージフオロワー回路、第２図に示す
ような電流−電圧変換回路が用いられている。 Conventional current detection circuits use, for example, a voltage follower circuit as shown in FIG. 1 and a current-voltage conversion circuit as shown in FIG.
第１図に示すボルテージフオロワー回路で電源
Vccから負荷１を介してオペアンプ２の非反転入
力に接続する。そしてこの非反転入力を抵抗３を
介して基準電位に接続する。そしてオペアンプ２
の反転入力を出力に接続する。このようにすれば
出力電圧e1は抵抗３の値R1とこの抵抗３を流れ
る電流i1の積e1＝i1・R1で与えられる。 The voltage follower circuit shown in Figure 1 is used as a power source.
Connect from V cc to the non-inverting input of operational amplifier 2 via load 1 . This non-inverting input is then connected to a reference potential via a resistor 3. and op amp 2
Connect the inverting input of to the output. In this way, the output voltage e 1 is given by the product e 1 =i 1 ·R 1 of the value R 1 of the resistor 3 and the current i 1 flowing through the resistor 3.
また第２図に示す電流−電圧変換回路では電流
i2をオペアンプ４の反転入力へ与えるとともに、
この反転入力と出力との間に抵抗５を介挿する。
そして非反転入力を基準電位に接続するようにし
ている。このようにすれば出力電圧e2は電流i2と
抵抗５の値R2の積に−１を乗じてe2＝−i2・R2で
与えられる。 In addition, in the current-voltage conversion circuit shown in Figure 2, the current
While giving i 2 to the inverting input of operational amplifier 4,
A resistor 5 is inserted between this inverting input and the output.
The non-inverting input is connected to a reference potential. In this way, the output voltage e 2 is obtained by multiplying the product of the current i 2 and the value R 2 of the resistor 5 by −1, and is given by e 2 =−i 2 ·R 2 .
しかしながらこのようなもので電流感度の切換
を行なう場合は、たとえば第１図に示すボルテー
ジフオロワー回路では抵抗３に適宜にタツプを設
け、このタツプを機械的あるいは電子的なスイツ
チで選択するようにしている。一方高感度電流検
出回路の場合オペアンプ２の入力回路は極めて高
インピーダンスなので上記スイツチの絶縁抵抗が
電流検出感度に大きく影響する。このために上記
スイツチを含む回路は高い絶縁抵抗を維持できる
ようにし、さらに所謂ガーデイング対策を施す必
要があるがその実施は極めて困難である。 However, when switching the current sensitivity with such a device, for example, in the voltage follower circuit shown in Fig. 1, an appropriate tap is provided on the resistor 3, and this tap is selected by a mechanical or electronic switch. ing. On the other hand, in the case of a high-sensitivity current detection circuit, since the input circuit of the operational amplifier 2 has extremely high impedance, the insulation resistance of the switch greatly affects the current detection sensitivity. For this reason, it is necessary for the circuit including the switch to maintain a high insulation resistance and to take so-called guarding measures, which are extremely difficult to implement.
また第２図に示す電流−電圧切換変換回路の場
合も抵抗５を複数個、並列に設けてスイツチで切
換えるために第１図と同様にガーデイング対策を
施す必要がある。 Also, in the case of the current-voltage switching conversion circuit shown in FIG. 2, since a plurality of resistors 5 are provided in parallel and switched by a switch, it is necessary to take measures against guarding as in FIG. 1.
本発明は上記の事情に鑑みてなされたもので簡
単な構成で微小電流を正確に検出することができ
る高感度電流検出回路を提供することを目的とす
るものである。 The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a highly sensitive current detection circuit that can accurately detect minute currents with a simple configuration.
以下本発明の一実施例を第３図に示す回路図を
参照して詳細に説明する。図中１１，１２は入力
端子で検出すべき電流を与える。そして入力端子
１１を第１のオペアンプ１３の非反転入力へ接続
するとともに電流検出用の抵抗値R3の第１の抵
抗１４を介して第２のオペアンプ１５の反転入力
に接続してボルテージフオロワー回路を構成して
いる。そして第１のオペアンプ１３の反転入力と
出力を接続するとともにこの出力を第１の出力端
子１５を介して切換回路１６に接続している。こ
こで第２のオペアンプが飽和しない状態において
Ｂ点の電位は０である。 Hereinafter, one embodiment of the present invention will be described in detail with reference to the circuit diagram shown in FIG. In the figure, 11 and 12 give currents to be detected at input terminals. Then, the input terminal 11 is connected to the non-inverting input of the first operational amplifier 13 and connected to the inverting input of the second operational amplifier 15 via the first resistor 14 with a resistance value R 3 for current detection. It constitutes a circuit. The inverting input and output of the first operational amplifier 13 are connected, and this output is also connected to the switching circuit 16 via the first output terminal 15. Here, the potential at point B is 0 when the second operational amplifier is not saturated.
そして第２のオペアンプの非反転入力を抵抗値
R4の抵抗１７を介して入力端子１２および基準
電位に接続している。そして第２のオペアンプ１
５の反転入力と出力との間に抵抗値R5の抵抗１
８およびカソードを共通に直列接続にしたツエナ
ー電圧Vtのツエナーダイオード１９，２０を介
挿し電流−電圧変換回路を構成している。そして
第２のオペアンプ１５の出力を第２の出力端子２
１を介して切換回路１６へ与える。なお切換回路
１６は第１、第２の出力端子１５，２１の出力の
一方を選択して第３の出力端子２２から出力す
る。なお上記ツエナーダイオード１９，２０はア
ノードを共通に接続してもよい。 Then, connect the non-inverting input of the second operational amplifier to the resistance value
It is connected to the input terminal 12 and the reference potential via a resistor 17 of R4 . and the second operational amplifier 1
A resistor 1 with resistance value R 5 is connected between the inverting input of 5 and the output.
Zener diodes 19 and 20 having a Zener voltage V t and whose cathodes are commonly connected in series are inserted to form a current-voltage conversion circuit. Then, the output of the second operational amplifier 15 is connected to the second output terminal 2.
1 to the switching circuit 16. Note that the switching circuit 16 selects one of the outputs from the first and second output terminals 15 and 21 and outputs it from the third output terminal 22. Note that the anodes of the Zener diodes 19 and 20 may be connected in common.
なおここで第４、第５の抵抗１７，１８の抵抗
値R4，R5は等しく、かつ第３の抵抗１４の抵抗
値R3に比して第５の抵抗１８の抵抗値は遥かに
大きいとする。 Note that the resistance values R 4 and R 5 of the fourth and fifth resistors 17 and 18 are equal, and the resistance value of the fifth resistor 18 is much larger than the resistance value R 3 of the third resistor 14. Suppose it is large.
たとえば第３の抵抗１４は1MΩ、第４、第５
の抵抗１７，１８を1GΩとすれば端子１１，１
２間を流れる電流i3が1μAで出力端子１５の電圧
e3は1Vとなる。また上記電流i3が1nAで出力端子
２１の電圧e4は1Vとなる。すなわち電流i3と出力
電圧e3，e4は第４図に示すような関係となる。し
たがつて、たとえば第２の出力端子e4の電圧が
10Vまで、すなわち電流i3が10nAまでは切換回路
１６で電圧e4を選択して出力し、電流i3が10nAを
越えると第１の出力端子１５の電圧e3を選択して
出力すれば広い範囲の微小電流を正確かつ安定に
検出することができる。またオペアンプ１５の出
力電圧e4はツエナー電圧Vtと順方向電圧VFとの
和で飽和する。 For example, the third resistor 14 is 1MΩ, and the fourth and fifth resistors
If the resistances 17 and 18 are 1GΩ, the terminals 11 and 1
When the current i3 flowing between 2 is 1 μA, the voltage at output terminal 15 is
e 3 becomes 1V. Further, when the current i 3 is 1 nA, the voltage e 4 at the output terminal 21 is 1V. That is, the current i 3 and the output voltages e 3 and e 4 have a relationship as shown in FIG. 4. Therefore, for example, the voltage at the second output terminal e4 is
If the voltage e4 is selected and outputted by the switching circuit 16 up to 10V, that is, the current i3 is up to 10nA, and the voltage e3 at the first output terminal 15 is selected and outputted when the current i3 exceeds 10nA. It is possible to accurately and stably detect minute currents over a wide range. Further, the output voltage e4 of the operational amplifier 15 is saturated at the sum of the Zener voltage Vt and the forward voltage VF .
なお切換回路１６で出力端子電圧e3，e4の一方
を選択する場合、オペアンプ１３，１５の出力は
充分に低インピーダンスであり格別に大きな絶縁
抵抗も必要としない。 Note that when the switching circuit 16 selects one of the output terminal voltages e 3 and e 4 , the outputs of the operational amplifiers 13 and 15 have sufficiently low impedance, and no particularly large insulation resistance is required.
第５図は本発明を応用した耐電圧および絶縁試
験を行なう装置の要部を示す回路図である。すな
わち図示Ａ点を被試験装置の、たとえば電源の一
次側を介して高圧電源の一端に接続し、この高圧
電源の他端を基準電位に接続する。そして上記Ａ
点と基準電位との間にサージアブリーバ３０を介
挿し、かつ抵抗３１，３２を介してオペアンプ３
３の非反転入力に接続する。そしてこのオペアン
プ３３の反転入力を出力に接続する。なお抵抗３
４可変抵抗３５をオフセツト調整のために設けて
いる。そしてオペアンプ３３の出力を抵抗３６、
可変抵抗３７を介してオペアンプ３８の反転入力
へ与える。またこの反転入力を増幅度を設定する
抵抗10kΩ、100kΩまたは1MΩの抵抗３９を選択
的に介して出力に接続している。また非反転入力
を抵抗４０を介して基準電位に接続している。そ
して抵抗４１、可変抵抗４２をオフセツト調整の
ために設け、出力を出力端子４３に接続してい
る。そして抵抗３１，３２の直列接続点と基準電
位およびオペアンプの非反転入力と基準電位との
間にそれぞれ２個のツエナーダイオードのアノー
ドを共通に接続した直列回路４４，４５を介挿
し、過電圧に対して保護を行なうようにしてい
る。なお上記ツエナーダイオードはカソードを共
通に接続してもよい。そして抵抗３１，３２の直
列接続点を抵抗４６を介してオペアンプ４７の反
転入力に接続している。またこのオペアンプ４７
の反転入力と基準電位との間に２個のダイオード
４８，４９を逆並列に接続して介挿している。ま
たこのオペアンプ４７の反転入力と出力との間に
ツエナーダイオード５０、コンデンサ５１および
抵抗５２、可変抵抗５３の直列回路を並列に接続
している。さらにこのオペアンプ４７の非反転入
力を抵抗５４を介して基準電位に接続し、可変抵
抗５５、抵抗５６によりオフセツト調整行なうよ
うにしている。そしてオペアンプ４７の出力を抵
抗５７を介してログアンプ５８へ与えこのログア
ンプ５８の出力を出力端子５９へ与えるようにし
ている。そして出力端子４３から得られた測定値
により耐電圧試験を行ない、また出力端子５９か
ら得られた測定値により絶縁試験を行なうように
している。 FIG. 5 is a circuit diagram showing the main parts of an apparatus for carrying out withstand voltage and insulation tests to which the present invention is applied. That is, the point A shown in the figure is connected to one end of a high-voltage power supply of the device under test, for example, via the primary side of the power supply, and the other end of this high-voltage power supply is connected to a reference potential. And above A
A surge breaker 30 is inserted between the point and the reference potential, and the operational amplifier 3 is connected via resistors 31 and 32.
Connect to the non-inverting input of 3. Then, the inverting input of this operational amplifier 33 is connected to the output. Note that resistance 3
4 variable resistors 35 are provided for offset adjustment. Then, the output of the operational amplifier 33 is connected to the resistor 36,
It is applied to the inverting input of an operational amplifier 38 via a variable resistor 37. Further, this inverting input is connected to the output via a resistor 39 of 10 kΩ, 100 kΩ or 1 MΩ selectively for setting the degree of amplification. Further, the non-inverting input is connected to a reference potential via a resistor 40. A resistor 41 and a variable resistor 42 are provided for offset adjustment, and the output is connected to an output terminal 43. Then, series circuits 44 and 45 each having the anodes of two Zener diodes connected in common are inserted between the series connection point of the resistors 31 and 32 and the reference potential, and the non-inverting input of the operational amplifier and the reference potential to prevent overvoltage. We are trying to protect them. Note that the cathodes of the Zener diodes may be connected in common. The series connection point of the resistors 31 and 32 is connected to the inverting input of an operational amplifier 47 via a resistor 46. Also, this operational amplifier 47
Two diodes 48 and 49 are connected in anti-parallel and inserted between the inverting input and the reference potential. Further, a series circuit including a Zener diode 50, a capacitor 51, a resistor 52, and a variable resistor 53 is connected in parallel between the inverting input and output of the operational amplifier 47. Further, the non-inverting input of the operational amplifier 47 is connected to a reference potential via a resistor 54, and offset adjustment is performed by a variable resistor 55 and a resistor 56. The output of the operational amplifier 47 is applied to a log amplifier 58 via a resistor 57, and the output of the log amplifier 58 is applied to an output terminal 59. A withstand voltage test is performed using the measured value obtained from the output terminal 43, and an insulation test is performed using the measured value obtained from the output terminal 59.
以上詳述したように本発明は、電流検出抵抗の
一端にボルテージフオロワー回路の入力を接続
し、他端を差動増幅器の一方の入力へ接続し、こ
の差動増幅器の一方の入力と出力との間に帰還抵
抗を介挿するとともに他方の入力を基準電位に接
続したものである。したがつて広い範囲の微小電
流を正確かつ安定に測定することができる高感度
電流検出回路を提供することができる。 As detailed above, the present invention connects the input of a voltage follower circuit to one end of the current detection resistor, connects the other end to one input of a differential amplifier, and connects one input and output of this differential amplifier to one end of the voltage follower circuit. A feedback resistor is inserted between the two inputs and the other input is connected to a reference potential. Therefore, it is possible to provide a highly sensitive current detection circuit that can accurately and stably measure minute currents over a wide range.
第１図はボルテージフオロワー回路の一例を示
す回路図、第２図は電流−電圧変換回路の一例を
示す回路図、第３図は本発明の一実施例を示す回
路図、第４図は第３図に示す回路の動作を示すグ
ラフ、第５図は本発明の応用例を示す回路図であ
る。
１１，１２……入力端子、１３，１５……オペ
アンプ、１４……抵抗（電流検出）、１５，２１
……出力端子、１８……抵抗（帰還）。
Fig. 1 is a circuit diagram showing an example of a voltage follower circuit, Fig. 2 is a circuit diagram showing an example of a current-voltage conversion circuit, Fig. 3 is a circuit diagram showing an example of the present invention, and Fig. 4 is a circuit diagram showing an example of a current-voltage conversion circuit. FIG. 3 is a graph showing the operation of the circuit shown in FIG. 3, and FIG. 5 is a circuit diagram showing an example of application of the present invention. 11, 12... Input terminal, 13, 15... Operational amplifier, 14... Resistor (current detection), 15, 21
...Output terminal, 18...Resistor (feedback).
Claims (1)
子電圧を測定するボルテージフオロワー回路と、 一方の入力を電流検出抵抗の他端に接続すると
ともに出力との間に帰還抵抗を介挿し他方の入力
と基準電位との間に入力抵抗を介挿した差動増幅
器からなる電流−電圧変換回路と、 上記差動増幅器の帰還抵抗に並列に接続しこの
帰還抵抗の端子間電圧が一定電圧を越えると導通
するツエナーダイオードとを具備し、上記電流検
出抵抗の抵抗値よりも上記帰還抵抗の抵抗値を大
きくしたことを特徴とする高感度電流検出回路。 ２ 特許請求の範囲第１項記載のものにおいてボ
ルテージフオロワー回路および電流−電圧変換回
路の各出力を切換回路により選択的に出力するこ
とを特徴とする高感度電流検出回路。[Claims] 1. A voltage follower circuit whose input is connected to one end of a current detection resistor to measure this terminal voltage, and one input is connected to the other end of the current detection resistor and a feedback circuit is provided between the output and the voltage follower circuit. A current-voltage conversion circuit consisting of a differential amplifier with an input resistor inserted between the other input and a reference potential, and a current-voltage conversion circuit that is connected in parallel to the feedback resistor of the differential amplifier and between the terminals of this feedback resistor. A high-sensitivity current detection circuit comprising a Zener diode that becomes conductive when a voltage exceeds a certain voltage, and wherein the resistance value of the feedback resistor is greater than the resistance value of the current detection resistor. 2. A highly sensitive current detection circuit according to claim 1, characterized in that each output of the voltage follower circuit and the current-voltage conversion circuit is selectively outputted by a switching circuit.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP59128511A JPS618673A (en) | 1984-06-22 | 1984-06-22 | High sensitivity current detecting circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP59128511A JPS618673A (en) | 1984-06-22 | 1984-06-22 | High sensitivity current detecting circuit |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS618673A JPS618673A (en) | 1986-01-16 |
| JPH0158462B2 true JPH0158462B2 (en) | 1989-12-12 |
Family
ID=14986549
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP59128511A Granted JPS618673A (en) | 1984-06-22 | 1984-06-22 | High sensitivity current detecting circuit |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS618673A (en) |
-
1984
- 1984-06-22 JP JP59128511A patent/JPS618673A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS618673A (en) | 1986-01-16 |
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