JPS58158560A - Over-current detection circuit - Google Patents

Abstract

PURPOSE:To facilitate the decision on characteristic of an eddy current in the operation thereof while enabling a stable operation when the lead is short- circuited by dividing the input of a comparator with an output voltage and a reference voltage after a reference voltage source and a resistance are added. CONSTITUTION:When a current supply passage is normal, potentials v1 and v2 at voltage division points d1 and d2 are set equal and an output terminal S of an comparator COM is at a high level. Then, when an over-current state takes place, an output terminal T0 declines in the voltage and with the potential v2 at the division point d2 down from v1, the output terminal S of the comparator COM is switched over to the low level. Here, if the load is about to be short circuited, the output terminal T0 gives zero volt. But as current flows from a reference voltage source P through resistances R5 and R4, the potential v2 at the division point d2 does not reach zero volt thereby maintaining the operation of the comparator COM. The characteristic during the operation of the over- current can be determined by the selection of the resistances R2-R6.

Description

【発明の詳細な説明】 この発明は、定電圧安定器の保護などに用いられる過電
流検出回路の改良に関するものである。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an overcurrent detection circuit used to protect a constant voltage stabilizer.

定電圧回路では、負荷にトラブルが発生して過電流状態
になると、用いられている制御素子に定格以上の負担が
かかり破壊することが多い。したがって、一般には過電
流になったことを検出して通電を停止させる保護回路が
設けられている。この種の保睦回路に用いられる従来の
過電流検出回路としては、第１図に示されるものがある
。In a constant voltage circuit, if a problem occurs in the load and an overcurrent condition occurs, the control element used is often subjected to a load exceeding its rating and is destroyed. Therefore, a protection circuit is generally provided to detect an overcurrent and stop the current supply. A conventional overcurrent detection circuit used in this type of protection circuit is shown in FIG.

第１図において、Ｔ１は入力端子も直流−―圧が印加さ
れる。Ｔｏは出力端子で％ＴＩＴＯ間の電流供給路には
抵抗Ｒ１が接続されている。この抵抗几ｌを流れる電流
によって、その両端には電位差ができる。この両端の各
電位の変化を抵抗Ｒ２゜Ｒ３からなる分圧器と、抵抗Ｒ
４，Ｒ，、からなる分圧器によってそれぞれ取出すよう
になっている。In FIG. 1, a direct current voltage is applied to the input terminal T1 as well. To is an output terminal, and a resistor R1 is connected to the current supply path between %TITO. The current flowing through this resistor creates a potential difference between its ends. A voltage divider consisting of resistors R2 and R3 and a resistor R
They are each taken out by a voltage divider consisting of 4, R, .

分圧点ｄ、の電圧Ｖ１ｔ／ｉ比較器ＣＯＭの反転入ヵ端
子に印加され、他方の分圧点ｄ２の電圧ｖ２は比較器Ｃ
ＯＭの非反転入力端子に印加され、その電圧を比較して
いる。すなわち、通常時においては電圧ｖ２はｖｌと同
じ値に設定されており、比較器ＣＯＭの出力端子Ｓはロ
ーレベルとなっている。そして、過電流検出時において
はＶ、が低くなるため、比較器ＣＯＭは反転動作し、出
力端子Ｓはハイレベルとなる。したがって、比較器Ｃ０
Ｍの出力で電流路を遮断すれば、各種の保膿を行なうこ
とができるわけである。The voltage V1t/i at the voltage dividing point d is applied to the inverting input terminal of the comparator COM, and the voltage v2 at the other voltage dividing point d2 is applied to the comparator C
It is applied to the non-inverting input terminal of OM, and the voltages are compared. That is, under normal conditions, the voltage v2 is set to the same value as vl, and the output terminal S of the comparator COM is at a low level. Then, when an overcurrent is detected, V becomes low, so the comparator COM performs an inverting operation, and the output terminal S becomes high level. Therefore, comparator C0
If the current path is cut off with the output of M, various types of purulent retention can be performed.

ところが、第１図の回路配置による過電流抄出回路には
幾つかの問題がある。電流供給路の人力。However, the overcurrent extraction circuit with the circuit arrangement shown in FIG. 1 has several problems. Human power in the current supply path.

出力電圧をＶＩＮ　＋　ｖｏｔｒ’ｒとし、電流を■と
すると、ＶｒＮ＝Ｖｏｕｒ　＋Ｒ１１（１） となり、ここで ｖｌ＝＝ｖ、　　　　　　　　　　　　　　　　　（４
）とすると、（１）、（２）、（３）式からとおくと、
（５）式は となる。すなわち、第１図の回路構成の過電流検出回路
を電源回路に設けると、第３図に示すようなフの字特性
を持つことになる。このような特性を有することは、仮
設に適用される負荷の種類によっては好ましくない。If the output voltage is VIN + votr'r and the current is ■, then VrN=Vour +R11(1), where vl==v, (4
), then from equations (1), (2), and (3),
Equation (5) becomes. That is, if an overcurrent detection circuit having the circuit configuration shown in FIG. 1 is provided in a power supply circuit, it will have a fold-back characteristic as shown in FIG. 3. Having such characteristics is undesirable depending on the type of load applied to the temporary structure.

また、出力電圧が短絡状態に近づいた場合、比較器ＣＯ
Ｍの入力が零ボルトに近づくが、比較器は正常に動作せ
ず、検出能力に信頼性が無かった。Also, if the output voltage approaches a short circuit condition, the comparator CO
M's input approached zero volts, but the comparator did not work properly and its detection ability was unreliable.

本発明は、以上のような問題点を考慮して開発されたも
のであり、任意の過電流特性が得られ、また出力電圧の
状態がいかなる場合においても安定して動作する過電流
検出回路を提供するものである。本発明は、そのため電
流供給路に電流検出用の抵抗を挿入し、電流供給路の電
流および電圧とは無関係に独立安定化した基準電圧電源
を設け、電流検出用の抵抗の入力端と基準電圧源間に第
１の分圧器が設けられ、また電流検出用の抵抗の出力端
と基準電圧源間に第２の分圧器が設けられ、これら分圧
器の各分圧点の電圧を比較器により比較し、第１の分圧
器の分圧点とアース間に所定の抵抗を接続するようにし
たものである。本発明の実施例を以下図面に従って説明
する。The present invention was developed in consideration of the above-mentioned problems, and provides an overcurrent detection circuit that can obtain arbitrary overcurrent characteristics and operates stably under any output voltage condition. This is what we provide. Therefore, the present invention inserts a current detection resistor in the current supply path, provides a reference voltage power supply that is independently stabilized independently of the current and voltage of the current supply path, and connects the input end of the current detection resistor to the reference voltage. A first voltage divider is provided between the sources, and a second voltage divider is provided between the output terminal of the current detection resistor and the reference voltage source. In comparison, a predetermined resistance is connected between the voltage dividing point of the first voltage divider and the ground. Embodiments of the present invention will be described below with reference to the drawings.

第２図は本発明の実施例に係る回路図である。FIG. 2 is a circuit diagram according to an embodiment of the present invention.

この図で第１図の従来回路と異なるのは、各分圧器の抵
抗Ｒ３，几Ｓの他端が接地される代りに基準電圧電源Ｐ
に接続されていることと、分圧点ｄ。This diagram differs from the conventional circuit in Figure 1 in that the other ends of the resistor R3 and S of each voltage divider are grounded, but instead of the reference voltage power supply P
and the voltage dividing point d.

が抵抗Ｒ６によって接地されている点である。is the point that is grounded by resistor R6.

第２図の回路配置で、電流供給路が正常である場合、分
圧点ｄ、、ｄ！の各電位ｖｌ、Ｖ２は等しく設定され、
比較器ＣＯＭの出力端子Ｓはハイレベルとなっている。In the circuit arrangement shown in Figure 2, if the current supply path is normal, the voltage dividing points d,,d! The respective potentials vl and V2 are set equal,
The output terminal S of the comparator COM is at a high level.

次に過電流状態になると、出力端子Ｔ。は電位が下がる
。したがって分圧点５− ｄ２の電位ｖ２がｖｌより下り、比較器ＣＯＭの出力端
子Ｓはローレベルに切換わる。ここで、もし負荷が短絡
に近づいたとすると、すなわち出力端子Ｔｏが零ボルト
となるが、基準電源から抵抗Ｒ５，几４を通して電流が
流れるため、分圧点ｄ２の電位Ｖｆｉは零ボルトになら
ない。その結果、この場合にも比較器ＣＯＭの動作は維
持される。Next, when an overcurrent condition occurs, the output terminal T. The potential decreases. Therefore, the potential v2 at the voltage dividing point 5-d2 becomes lower than vl, and the output terminal S of the comparator COM is switched to a low level. Here, if the load approaches a short circuit, that is, the output terminal To becomes zero volts, but since current flows from the reference power source through the resistor R5 and the resistor 4, the potential Vfi at the voltage dividing point d2 does not become zero volts. As a result, the operation of the comparator COM is maintained in this case as well.

また、第２図の回路配置の場合、 となる。但しｖＲは基準電圧源の出力電圧である。In addition, in the case of the circuit layout shown in Figure 2, becomes. However, vR is the output voltage of the reference voltage source.

この式によって明らかなように、抵抗Ｒ１〜Ｒ６の値を
選択することにより、過電流動作時の特性を決めること
ができる。例えば、フの字特性を得ようとする場合には
、Ｉ（ＷｋＶｏｔｙＴとなるようにするため、 ｆｔ、　Ｒ３Ｒ４＋　Ｒ，几４Ｒ６Ｒ１几５Ｒ６＝０と
なるように各抵抗を選べばよい。また定電流特６− 性とするには工とＶＯＵＴを無関係にすればよく、すな
わち 几、Ｒ，Ｒ，＋Ｒ１，Ｒ，Ｉ’ｔ、−Ｒ３几４Ｒ１１＝
０となるようにすればよいわけである。As is clear from this equation, the characteristics during overcurrent operation can be determined by selecting the values of the resistors R1 to R6. For example, when trying to obtain a foldback characteristic, in order to obtain I(WkVotyT), each resistor should be selected so that ft, R3R4+ R, 4R6R1 5R6 = 0. Also, constant current Characteristic 6- In order to make it a
All you have to do is set it to 0.

本発明は、以上のように基準電圧源と抵抗を付加するだ
けで、過電流動作時の特性を容易に決定でき、かつ負荷
が短絡した場合においても、比較器の入力は出力電圧と
基準電圧で分圧して得るようにしているので動作が不安
定となることもない。According to the present invention, the characteristics during overcurrent operation can be easily determined by simply adding a reference voltage source and a resistor as described above, and even if the load is short-circuited, the input of the comparator is connected to the output voltage and the reference voltage. Since the voltage is obtained by dividing the pressure at , the operation will not become unstable.

なお、上記実施例において、比較器の入力端子に与えて
いる分圧点の電圧を入れ代えて印加するように接続した
場合、検出出力は通常時ローレベルで、過電流検出時に
はハイレベルとすることもできる。In addition, in the above example, if the voltages at the voltage dividing points applied to the input terminals of the comparator are connected in such a way that they are applied interchangeably, the detection output is normally at a low level, and when an overcurrent is detected, it is at a high level. You can also do that.

【図面の簡単な説明】[Brief explanation of the drawing]

第１図は従来の過電流検出回路の回路図、第２図は本発
明の実施例に係る回路図、第３図は回路動作を説明する
ための電流対電圧特性図である。 なお図面に使用した符号はそれぞれ以下のものを示す。 Ｒ，−Ｒ６・・・・・・第１〜第６の抵抗、ＣＯＭ・・
・・・・比較器、Ｐ・・・・・・基準電圧源。 第　／ｌ￥１ ３４１− 第３　図FIG. 1 is a circuit diagram of a conventional overcurrent detection circuit, FIG. 2 is a circuit diagram according to an embodiment of the present invention, and FIG. 3 is a current vs. voltage characteristic diagram for explaining the circuit operation. The symbols used in the drawings indicate the following. R, -R6... 1st to 6th resistors, COM...
...Comparator, P...Reference voltage source. /l￥1 341- Figure 3

Claims (1)

【特許請求の範囲】[Claims] 電流供給路に挿入され電流を検出するだめの第１の抵抗
と、前記電流供給路の電流および電圧とは独立して安定
化された基準電圧源と、前記第１の抵抗の入力端と前記
基準電圧源間に接続された第２および第３の抵抗の直列
接続からなる第１の分圧器と、前記第１の抵抗の出力端
と前記基準電圧源間に接続された第４および第５の抵抗
の直列接続からなる第２の分圧器と、反転・非反転入力
端子を持ち、これら１対の入力端子の一方に前記第１の
分圧器の分圧点の電圧が印加され、他方に前記第２の分
圧器の分圧点の電圧が印加されるように接続され、両分
圧点の電圧の比較出力を得る比較器と、前記第１の分圧
器の分圧点とアース間に接続された第６の抵抗とを備え
／こことを特徴とする過電流検出回路。a first resistor inserted into the current supply path for detecting current; a reference voltage source stabilized independently of the current and voltage of the current supply path; an input terminal of the first resistor; a first voltage divider consisting of a series connection of second and third resistors connected between a reference voltage source; fourth and fifth voltage dividers connected between an output terminal of the first resistor and the reference voltage source; a second voltage divider consisting of a series connection of resistors, and an inverting/non-inverting input terminal, the voltage at the dividing point of the first voltage divider is applied to one of the pair of input terminals, and the voltage at the dividing point of the first voltage divider is applied to the other. a comparator connected so that the voltage at the voltage dividing point of the second voltage divider is applied to obtain a comparison output of the voltages at both voltage dividing points, and between the voltage dividing point of the first voltage divider and ground. An overcurrent detection circuit comprising/characterized in that a sixth resistor is connected to the overcurrent detection circuit.