JP2901284B2 - Overcurrent protection circuit - Google Patents
Overcurrent protection circuitInfo
- Publication number
- JP2901284B2 JP2901284B2 JP26152389A JP26152389A JP2901284B2 JP 2901284 B2 JP2901284 B2 JP 2901284B2 JP 26152389 A JP26152389 A JP 26152389A JP 26152389 A JP26152389 A JP 26152389A JP 2901284 B2 JP2901284 B2 JP 2901284B2
- Authority
- JP
- Japan
- Prior art keywords
- overcurrent protection
- protection circuit
- output
- transistor
- power supply
- 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 - Lifetime
Links
Description
【発明の詳細な説明】 〔産業上の利用分野〕 本発明は集積化された定電圧回路において、特に出力
段トランジスタに流れる電流が規定のレベルに達した点
を検出し出力段トランジスタを保護する過電流保護回路
に関し、起動時の誤動作を防止する回路に関する。Description: BACKGROUND OF THE INVENTION The present invention relates to an integrated constant voltage circuit, and in particular, detects a point at which a current flowing through an output stage transistor reaches a specified level to protect the output stage transistor. The present invention relates to an overcurrent protection circuit and a circuit for preventing a malfunction at startup.
一般に定電圧回路には、出力段トランジスタの破壊保
護として該出力段トランジスタの出力電流を制限する過
電流保護回路が付備されている。In general, the constant voltage circuit is provided with an overcurrent protection circuit for limiting the output current of the output stage transistor as protection against destruction of the output stage transistor.
従来の定電圧回路を第２図に示す。図においてPNPト
ランジスタ（以下Trとする。）22が、出力段Trで出力端
子２の電圧を抵抗20,21で分割した電圧と基準電圧源４
の出力電圧とを誤差増幅器５により比較し、帰還をかけ
出力端子２の電圧を一定に保つ定電圧回路において電源
端子１より抵抗15,16を通し、接続した過電流検出回路
８を付備し、抵抗15,16を共通とし、ツェナーダイオー
ド17を通し、抵抗18を通し、Di19のアノードに接続し、
過電流保護の電圧を決める為に前記Di19を１ケ又は複数
ケ接続し、Di19のカソードを出力端子２に接続した過電
圧検出回路とを付備している。FIG. 2 shows a conventional constant voltage circuit. In the figure, a PNP transistor (hereinafter referred to as Tr) 22 is composed of a reference voltage source 4 and a voltage obtained by dividing the voltage of the output terminal 2 by resistors 20 and 21 in the output stage Tr.
The output voltage of the power supply terminal 1 is compared with the output voltage of the power supply terminal 1 and the output voltage of the output terminal 2 is kept constant. , The resistors 15 and 16 are made common, through the Zener diode 17, through the resistor 18, and connected to the anode of Di19,
In order to determine the voltage for overcurrent protection, one or more of the Di19s are connected, and an overvoltage detection circuit is provided with the cathode of the Di19 connected to the output terminal 2.
ここで、過電流検出回路８は電源端子１より流入し出
力端子２から流出する出力電流を抵抗15で検出し、出力
段Tr22の過電流時に出力段Tr22をOFFさせ保護する。こ
の過電流検出回路８と過電圧検出回路からなる過電流保
護回路により、第３のように出力段Trの動作限界（安全
動作領域）まで特性を引き出せる様になっている。Here, the overcurrent detection circuit 8 detects the output current flowing from the power supply terminal 1 and flowing out of the output terminal 2 with the resistor 15, and when the output stage Tr22 is overcurrent, turns off the output stage Tr22 and protects it. With the overcurrent protection circuit including the overcurrent detection circuit 8 and the overvoltage detection circuit, the characteristics can be brought out to the operation limit (safe operation area) of the output stage Tr as described in the third aspect.
上述した従来の過電流保護回路は、電流が一定値以上
となれば動作してしまう為、電源端子１へ電源投入時に
電源端子１と出力端子２の電位はほぼ同電位で立ち上が
り、このとき出力端子電圧が設定の電圧に達していない
場合、出力段Tr22が飽和し、ベース電流が増加し通常の
IB22の数百倍程度のIB22′が流れる。またIB22′は出力
段Tr22のエミッタ電流として抵抗15を流れ出力電流とし
て検出されるので、保護回路が働き出力に定電圧が出力
されず、保護回路の動作した点でつりあい、第５図のよ
うに低い電圧で出力が保たれてしまうという欠点があ
る。Since the above-mentioned conventional overcurrent protection circuit operates when the current exceeds a predetermined value, the potentials of the power supply terminal 1 and the output terminal 2 rise at substantially the same potential when the power supply to the power supply terminal 1 is turned on. If the terminal voltage does not reach the set voltage, the output stage Tr22 saturates, the base current increases, and the normal
Hundreds of times the I B22 I B22 'flows. Further, since IB22 'flows through the resistor 15 as the emitter current of the output stage Tr22 and is detected as an output current, the protection circuit operates and a constant voltage is not output to the output. There is a disadvantage that the output is maintained at such a low voltage.
本発明の過電流保護回路は、電源ラインにエミッタが
接続され出力端子にコレクタが接続された出力トランジ
スタの出力電流を制限する過電流保護回路であって、前
記出力トランジスタを動作させるためのベース電流を供
給する第１のトランジスタと、前記出力トランジスタに
流れる電流が規定のレベルに達したときに前記第１のト
ランジスタをOFFさせる第１の過電流保護回路と、前記
電源ラインにエミッタが接続され前記出力端子にベース
が接続された第２のトランジスタと、この第２のトラン
ジスタがOFFのときに前記第１の過電流保護回路を動作
させずONのときに前記第１の過電流保護回路を正常動作
させる第２の過電流保護回路とをさらに有する。An overcurrent protection circuit according to the present invention is an overcurrent protection circuit for limiting an output current of an output transistor whose emitter is connected to a power supply line and whose collector is connected to an output terminal, and a base current for operating the output transistor. A first overcurrent protection circuit that turns off the first transistor when a current flowing through the output transistor reaches a predetermined level; and an emitter connected to the power supply line, A second transistor having a base connected to the output terminal, and the first overcurrent protection circuit operating normally when the second transistor is off and not operating when the second transistor is off. A second overcurrent protection circuit to be operated.
次に、本発明を実施例により説明する。 Next, the present invention will be described with reference to examples.
第１図は本発明の一実施例である。第１図において、
PNP Tr22が出力段Tr22で定電圧回路の基本動作は従来例
と同じで、電源端子19を抵抗13を通しPNP Tr14のエミッ
タに接続して該PNP Tr14のベースを出力端子２に、コレ
クタをエミッタ接地されたNPN Tr12のベースに接続しNP
N Tr12のコレクタを電源端子１に接続された定電流源11
の他端とエミッタ接地のNPN Tr10のベースに共通に接続
しコレクタをNPN Tr7のベースに接続した過電流保護回
路と従来例と同様の過電流保護回路を付備している。こ
の第１図において電源端子１に電圧が印加され電源が立
ち上る時のPNP Tr14は電源端子１と出力端子２がほぼ同
電位である為OFFし、NPN Tr12もOFFし、既に起動してい
る定電流源11によりNPN Tr10がONしコレクタ電流として
NPN Tr7のベース電流を引く。このためNPN Tr7はOFFと
なり、出力段Tr22が飽和してIB22′が増加し過電流とし
て検出されても、過電流保護回路は動作しない為、第４
図のように出力端子２は正常に設定電圧まで上昇するこ
とができる。その後も電源電圧が上昇を続け、安定動作
に必要な分だけ出力端子２より高い電圧になると出力段
Tr22が飽和しなくなり、PNP Tr14はONしてPNP Tr14のコ
レクタ電流として定電流源の出力電流を引く為、NPN Tr
10はOFFし、従来例と同様な動作で出力段トランジスタ
の過電流を抵抗９で検出でき、過電流保護回路が正常動
作することができる。FIG. 1 shows an embodiment of the present invention. In FIG.
The basic operation of the constant voltage circuit is the same as that of the conventional example. The power supply terminal 19 is connected to the emitter of the PNP Tr14 through the resistor 13, the base of the PNP Tr14 is connected to the output terminal 2, and the collector is connected to the emitter. Connect to the grounded NPN Tr12 base and
Constant current source 11 with collector of N Tr12 connected to power supply terminal 1
An overcurrent protection circuit in which the other end of the NPN transistor is commonly connected to the base of the NPN Tr10 having a common emitter and a collector is connected to the base of the NPN Tr7, and an overcurrent protection circuit similar to the conventional example are provided. In FIG. 1, when a voltage is applied to the power supply terminal 1 and the power supply rises, the PNP Tr 14 is turned off because the power supply terminal 1 and the output terminal 2 have substantially the same potential, the NPN Tr 12 is also turned off, and the PNP Tr 12 is already started. NPN Tr10 is turned on by current source 11 and becomes collector current.
Subtract the base current of NPN Tr7. Therefore, even if the output stage Tr22 is saturated and IB22 'increases and is detected as an overcurrent, the overcurrent protection circuit does not operate.
As shown in the figure, the output terminal 2 can normally rise to the set voltage. After that, the power supply voltage continues to rise, and when the voltage becomes higher than the output terminal 2 by the amount necessary for stable operation, the output stage
Tr22 is no longer saturated, PNP Tr14 turns ON, and the output current of the constant current source is subtracted as the collector current of PNP Tr14.
The reference numeral 10 turns OFF, and the overcurrent of the output stage transistor can be detected by the resistor 9 in the same operation as the conventional example, and the overcurrent protection circuit can operate normally.
このように本発明によれば、電源立上り途中での過電
流による誤動作が防止でき、しかも、電源端子電圧が一
定以上となったのちは、過電流に対する保護が正常に動
作する過電流保護回路が得られる。As described above, according to the present invention, it is possible to prevent a malfunction due to an overcurrent during power-up, and furthermore, to provide an overcurrent protection circuit in which the overcurrent protection operates normally after the power supply terminal voltage becomes higher than a certain value. can get.
第１図は本発明実施例の回路図、第２図は従来例の回路
図、第３図はトランジスタの動作限界（安全動作領域）
の特性図、第４図は本発明実施例の電源電圧特性図、第
５図は従来例の電源電圧特性図。 １……電源端子、２……出力端子、３……接地端子、４
……基準電圧源、５……誤差増幅器、6,7,10,12……NPN
Tr、８……過電流検出回路、9,13,15,16,18,20,21……
抵抗、11……定電流源、14……PNP Tr、17……ツェナー
Di、19……ダイオード、22……出力段Tr。1 is a circuit diagram of an embodiment of the present invention, FIG. 2 is a circuit diagram of a conventional example, and FIG. 3 is an operation limit of a transistor (safe operation area).
FIG. 4 is a power supply voltage characteristic diagram of the embodiment of the present invention, and FIG. 5 is a power supply voltage characteristic diagram of a conventional example. 1 power supply terminal, 2 output terminal, 3 ground terminal, 4
…… Reference voltage source, 5 …… Error amplifier, 6,7,10,12 …… NPN
Tr, 8 ... Overcurrent detection circuit, 9,13,15,16,18,20,21 ...
Resistor, 11 constant current source, 14 PNP Tr, 17 Zener
Di, 19: Diode, 22: Output stage Tr.
Claims (1)
にコレクタが接続された出力トランジスタの出力電流を
制限する過電流保護回路であって、前記出力トランジス
タを動作させるためのベース電流を供給する第１のトラ
ンジスタと、前記出力トランジスタに流れる電流が規定
のレベルに達したときに前記第１のトランジスタをOFF
させる第１の過電流保護回路と、前記電源ラインにエミ
ッタが接続され前記出力端子にベースが接続された第２
のトランジスタと、この第２のトランジスタがOFFのと
きに前記第１の過電流保護回路を動作させずONのときに
前記第１の過電流保護回路を正常動作させる第２の過電
流保護回路とをさらに有することを特徴とする過電流保
護回路。1. An overcurrent protection circuit for limiting an output current of an output transistor having an emitter connected to a power supply line and a collector connected to an output terminal, wherein the overcurrent protection circuit supplies a base current for operating the output transistor. The first transistor is turned off when the current flowing through the first transistor and the output transistor reaches a specified level.
A first overcurrent protection circuit, and a second overcurrent protection circuit having an emitter connected to the power supply line and a base connected to the output terminal.
And a second overcurrent protection circuit that normally operates the first overcurrent protection circuit when the second transistor is OFF and does not operate the first overcurrent protection circuit when the second transistor is OFF. An overcurrent protection circuit, further comprising:
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP26152389A JP2901284B2 (en) | 1989-10-06 | 1989-10-06 | Overcurrent protection circuit |
| CA 2026929 CA2026929A1 (en) | 1989-10-06 | 1990-10-04 | Chord truss roof structure |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP26152389A JP2901284B2 (en) | 1989-10-06 | 1989-10-06 | Overcurrent protection circuit |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH03123914A JPH03123914A (en) | 1991-05-27 |
| JP2901284B2 true JP2901284B2 (en) | 1999-06-07 |
Family
ID=17363087
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP26152389A Expired - Lifetime JP2901284B2 (en) | 1989-10-06 | 1989-10-06 | Overcurrent protection circuit |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2901284B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4771868B2 (en) | 2006-06-06 | 2011-09-14 | サンコール株式会社 | Valve structure for internal combustion engine |
-
1989
- 1989-10-06 JP JP26152389A patent/JP2901284B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH03123914A (en) | 1991-05-27 |
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