JP2002300773A - Switching regulator circuit - Google Patents
Switching regulator circuitInfo
- Publication number
- JP2002300773A JP2002300773A JP2001100749A JP2001100749A JP2002300773A JP 2002300773 A JP2002300773 A JP 2002300773A JP 2001100749 A JP2001100749 A JP 2001100749A JP 2001100749 A JP2001100749 A JP 2001100749A JP 2002300773 A JP2002300773 A JP 2002300773A
- Authority
- JP
- Japan
- Prior art keywords
- circuit
- overcurrent
- switching regulator
- voltage
- load short
- 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.)
- Withdrawn
Links
Landscapes
- Dc-Dc Converters (AREA)
Abstract
Description
【発明の属する技術分野】この発明は、過電流検出回路
を出力電圧の電圧値に関わらず確実に過電流保護をおこ
なうことが可能な、スイッチングレギュレータ回路に関
する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching regulator circuit capable of reliably performing an overcurrent protection for an overcurrent detection circuit regardless of a voltage value of an output voltage.
【従来の技術】従来の、降圧型スイッチングレギュレー
タ回路としては、図２の回路図に示されるような回路が
知られていた。即ち、電源１０と外付けトランジスタ１
８を接続し、前記外付けトランジスタの他端にはコイル
１９と外付けダイオード２３が接続され、前記コイルの
他端にセンス抵抗２０が接続されている。センス抵抗の
他端は、スイッチングレギュレータ回路の出力端子ＶＯ
ＵＴとなり、前記出力端子には容量２１が接続され、あ
る一定の電圧になるようにスイッチングレギュレータ制
御回路２４が外付けトランジスタ１８のＯＮ時間やＯＦ
Ｆ時間を制御する。図２の場合、センス抵抗２０により
過電流検出をおこなう。電流がセンス抵抗に流れると、
センス端子２５と出力端子２６との間に電位差ができ
る。そして、センス抵抗に過電流が流れ、前記電圧差が
所望の値になると、過電流コンパレータ１２の出力が反
転し”Ｌ”を出力する。次に、前記出力は低電圧検出回
路１４とのＮＯＲ回路２７に入力され、このとき低電圧
検出回路は”Ｌ”出力のため、ＮＯＲ回路２７は”Ｈ”
を出力する。そして内部回路１７とのＯＲ回路１５に入
力され”Ｈ”を出力し、強制的に外付けトランジスタ１
８をＯＦＦし、出力端子ＶＯＵＴをオープン状態にす
る。よって過電流検出回路が動作することにより過電流
状態が継続するのを防ぎ、外付けトランジスタ等が過電
流により破壊されることを防ぐ。2. Description of the Related Art As a conventional step-down switching regulator circuit, a circuit as shown in a circuit diagram of FIG. 2 has been known. That is, the power supply 10 and the external transistor 1
8, a coil 19 and an external diode 23 are connected to the other end of the external transistor, and a sense resistor 20 is connected to the other end of the coil. The other end of the sense resistor is connected to the output terminal VO of the switching regulator circuit.
A capacitor 21 is connected to the output terminal, and the switching regulator control circuit 24 controls the ON time of the external transistor 18 and the OF so that the voltage becomes a certain constant voltage.
Control the F time. In the case of FIG. 2, overcurrent detection is performed by the sense resistor 20. When current flows through the sense resistor,
There is a potential difference between the sense terminal 25 and the output terminal 26. Then, when an overcurrent flows through the sense resistor and the voltage difference reaches a desired value, the output of the overcurrent comparator 12 is inverted to output “L”. Next, the output is input to the NOR circuit 27 with the low voltage detection circuit 14. At this time, since the low voltage detection circuit outputs "L", the NOR circuit 27 outputs "H".
Is output. Then, it is input to the OR circuit 15 with the internal circuit 17 and outputs “H”, forcing the external transistor 1
8 is turned off, and the output terminal VOUT is opened. Therefore, the operation of the overcurrent detection circuit prevents the overcurrent state from continuing, and prevents the external transistor and the like from being damaged by the overcurrent.
【発明が解決しようとする課題】しかし、従来の降圧型
スイッチングレギュレータ回路の過電流検出回路では、
過電流検出回路内部の内部コンパレータ回路である入力
段電位となるセンス端子、出力端子が約１Ｖ以下である
と誤動作をし、過電流状態ではないにも関わらず過電流
状態と判断し、強制的に外付けトランジスタ１８をＯＦ
Ｆしてしまうことがある。過電流検出回路が誤動作をし
たまま、外付けトランジスタをＯＦＦしてしまうと、セ
ンス端子、出力端子が低い電位のまま維持されるため、
過電流検出回路の状態は解除されることがない。いわゆ
る、出力電圧が立ち上がらなくなってしまうという状態
が起こる可能性があった。前記状態を回避するため、低
電圧検出回路１４を設け、出力端子が１Ｖ程度以下にな
ると強制的に過電流回路を停止させていた。そのため、
従来の降圧型スイッチングレギュレータ回路では負荷短
絡等で出力電圧がＧＮＤにまで下がった場合には、過電
流の保護はできないという問題があった。However, in a conventional overcurrent detection circuit of a step-down switching regulator circuit,
If the voltage of the sense terminal and output terminal of the input stage, which is the internal comparator circuit inside the overcurrent detection circuit, is about 1 V or less, malfunction occurs. External transistor 18 to OF
F. If the external transistor is turned off while the overcurrent detection circuit malfunctions, the sense terminal and the output terminal are maintained at a low potential.
The state of the overcurrent detection circuit is not released. In other words, there is a possibility that the output voltage does not rise. In order to avoid the above state, the low voltage detection circuit 14 is provided, and when the output terminal becomes lower than about 1 V, the overcurrent circuit is forcibly stopped. for that reason,
The conventional step-down switching regulator circuit has a problem that overcurrent cannot be protected when the output voltage drops to GND due to a load short circuit or the like.
【課題を解決するための手段】このような問題を解決す
るために、過電流保護回路の他に負荷短絡用保護回路を
内蔵することで、負荷短絡等により出力電圧がＧＮＤ付
近に下がった場合も確実に過電流を停止させることを特
徴としたものである。In order to solve such a problem, by incorporating a load short-circuit protection circuit in addition to the overcurrent protection circuit, when the output voltage drops to the vicinity of GND due to a load short circuit or the like. Also, the overcurrent is surely stopped.
【発明の実施の形態】本発明は低電圧検出回路、過電流
回路を内蔵しているスイッチングレギュレータにおい
て、負荷短絡用保護回路を内蔵することで、負荷変動ま
たは、負荷短絡等による過電流を出力端子の電位に関わ
らず確実に停止させる。DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a switching regulator having a built-in low voltage detection circuit and an overcurrent circuit, and having a built-in protection circuit for load short-circuit, thereby outputting an overcurrent due to load fluctuation or load short-circuit. Stop the operation irrespective of the potential of the terminal.
【実施例】図１は本発明の第１の実施例を示す過電流検
出回路図である。これは、スイッチングレギュレータ回
路内部の過電流検出回路として知られている回路であ
る。次にその動作を説明する。電源投入時、センス端
子、ＶＯＵＴ端子がＧＮＤ近くの場合低電圧検出回路１
４はＯＦＦすることで”Ｈ”を出力。また、内蔵ソフト
スタート回路によりセンス抵抗に過電流がほとんど流れ
ないため、センス端子２５と出力端子２６の電圧差はな
くトランジスタ２８はＯＦＦすることで負荷短絡用保護
回路は”Ｈ”を出力。故に、ＮＡＮＤ回路２９は”Ｌ”
を出力することで過電流状態になることはなく出力電圧
は所望の電圧値まで上昇する。ここで、センス抵抗を１
００ｍΩとし、過電流検出回路１２はＶＯＵＴ入力側に
オフセット電圧１００ｍＶをもたせてあるとすると、過
電流１Ａがセンス抵抗に流れたとき、センス端子、出力
端子の電圧差は１００ｍＶとなり、過電流検出回路は反
転する。また、低電圧検出回路１４のトランジスタのＶ
ｔｈを１Ｖとすると、低電圧検出回路１４は出力端子が
１Ｖ以下の場合に、低電圧検出回路１４は”Ｈ”を出力
し、過電流検出回路１２を停止させる。このとき、負荷
短絡用保護回路は”Ｈ”を出力したままである。また、
負荷短絡等により出力端子電圧がＧＮＤ付近まで下がり
過電流が３Ａ以上流れたとする。ここで、負荷短絡用保
護回路１３のトランジスタ２８のＶｔｈを０．３Ｖとす
ると、負荷短絡用保護回路１３に３Ａの過電流が流れ、
センス端子、出力端子間に０．３Ｖの電圧差が生じた場
合にトランジスタ２８がＯＮすることで、トランジスタ
２８のソース電圧である出力端子の電圧を出力する。こ
こで、出力端子は負荷短絡等によりＧＮＤ付近まで下が
っているため、負荷短絡用保護回路は”Ｌ”を出力する
こととなり、ＮＡＮＤ回路２９は”Ｈ”を出力し、強制
的に外付けトランジスタ１８をＯＦＦし、出力端子ＶＯ
ＵＴをオープン状態にする。過電流状態が継続するのを
防ぎ、外付けトランジスタ等が過電流により破壊される
ことを防ぐ。いわゆる、第１の実施例で示したような、
負荷短絡用保護回路を内蔵することで負荷短絡等により
出力電圧がＧＮＤ近くまで下がった場合にも、確実に出
力電圧の電位に関わらず保護回路が働くこととなる。ま
た、過電流保護検出回路や負荷短絡用保護回路の検出動
作をＯＲ回路、ＮＯＲ回路、ＮＡＮＤ回路によりおこな
っているが、他のロジック回路等を用いても、同様の動
作をおこなえることは明白であり、負荷短絡等により、
出力電圧がＧＮＤ付近まで下がった時にも確実に過電流
検出をおこなうことが本発明の目的である。また、本発
明においては、降圧型スイッチングレギュレータ回路に
おいて示したが、同期整流方式降圧型スイッチングレギ
ュレータ回路、及び昇圧型スイッチングレギュレータ回
路、反転型スイッチングレギュレータ回路についても、
本発明が適用されることは明白である。FIG. 1 is an overcurrent detection circuit diagram showing a first embodiment of the present invention. This is a circuit known as an overcurrent detection circuit inside the switching regulator circuit. Next, the operation will be described. When the power supply is turned on and the sense terminal and the VOUT terminal are close to GND, the low voltage detection circuit 1
4 outputs "H" when turned off. Also, since an overcurrent hardly flows through the sense resistor due to the built-in soft start circuit, there is no voltage difference between the sense terminal 25 and the output terminal 26 and the transistor 28 is turned off, so that the load short-circuit protection circuit outputs "H". Therefore, the NAND circuit 29 is "L"
Is output, the output voltage rises to a desired voltage value without causing an overcurrent state. Here, the sense resistance is set to 1
Assuming that the overcurrent detection circuit 12 has an offset voltage of 100 mV on the VOUT input side, when the overcurrent 1A flows through the sense resistor, the voltage difference between the sense terminal and the output terminal becomes 100 mV, and the overcurrent detection circuit 12 Is inverted. Also, the V of the transistor of the low-voltage detection circuit 14
Assuming that th is 1 V, when the output terminal of the low voltage detection circuit 14 is 1 V or less, the low voltage detection circuit 14 outputs “H” and stops the overcurrent detection circuit 12. At this time, the load short-circuit protection circuit keeps outputting “H”. Also,
It is assumed that the output terminal voltage drops to near GND due to a load short circuit or the like, and an overcurrent of 3 A or more flows. Here, assuming that Vth of the transistor 28 of the protection circuit 13 for load short circuit is 0.3 V, an overcurrent of 3 A flows through the protection circuit 13 for load short circuit,
When a voltage difference of 0.3 V occurs between the sense terminal and the output terminal, the transistor 28 is turned on, so that the output terminal voltage which is the source voltage of the transistor 28 is output. Here, since the output terminal has dropped to the vicinity of GND due to a load short circuit or the like, the load short circuit protection circuit outputs "L", the NAND circuit 29 outputs "H", and the external transistor is forcibly forced. 18 is turned off and the output terminal VO
Open the UT. An overcurrent state is prevented from continuing, and an external transistor or the like is prevented from being damaged by an overcurrent. So-called, as shown in the first embodiment,
By incorporating a protection circuit for load short-circuit, even when the output voltage drops to near GND due to a load short-circuit or the like, the protection circuit reliably operates regardless of the potential of the output voltage. Further, the detection operation of the overcurrent protection detection circuit and the load short-circuit protection circuit is performed by the OR circuit, the NOR circuit, and the NAND circuit, but it is obvious that the same operation can be performed by using other logic circuits and the like. Yes, due to load short circuit, etc.
It is an object of the present invention to reliably perform overcurrent detection even when the output voltage drops to near GND. In the present invention, the step-down switching regulator circuit has been described, but the synchronous rectification step-down switching regulator circuit, the step-up switching regulator circuit, the inverting switching regulator circuit,
It is clear that the invention applies.
【発明の効果】この発明は、低電圧検出回路、過電流回
路を内蔵しているスイッチングレギュレータにおいて、
負荷短絡用保護回路を内蔵することで、負荷変動また
は、負荷短絡等による過電流を出力端子の電位に関わら
ず確実に停止させ、外付けトランジスタ等を確実に保護
するスイッチングレギュレータ回路を簡単な回路構成で
実現できるという効果がある。The present invention relates to a switching regulator having a built-in low voltage detection circuit and overcurrent circuit.
A built-in load short-circuit protection circuit ensures that overcurrents due to load fluctuations or load short-circuits are reliably stopped irrespective of the potential of the output terminal, and a simple switching regulator circuit that reliably protects external transistors, etc. There is an effect that it can be realized by the configuration.
【図１】本発明の第１の実施例の電源回路説明図であ
る。FIG. 1 is an explanatory diagram of a power supply circuit according to a first embodiment of the present invention.
【図２】従来の電源回路説明図である。FIG. 2 is an explanatory diagram of a conventional power supply circuit.
１０ 電源 １２ 過電流検出回路 １３ 負荷短絡用保護回路 １４ 低電圧検出回路 １５ ＯＲ回路 １６ ＥＸＴ端子 １７ 内部回路 １８ 外付けトランジスタ １９ コイル ２０ センス抵抗 ２３ ダイオード ２４ スイッチングレギュレータ制御回路 ２５ センス端子 ２６ 出力端子 ２７ ＮＯＲ回路 ２８ 負荷短絡用保護回路内部トランジスタ １１、２１ 容量 Reference Signs List 10 power supply 12 overcurrent detection circuit 13 load short-circuit protection circuit 14 low voltage detection circuit 15 OR circuit 16 EXT terminal 17 internal circuit 18 external transistor 19 coil 20 sense resistor 23 diode 24 switching regulator control circuit 25 sense terminal 26 output terminal 27 NOR circuit 28 Load transistor protection circuit internal transistor 11, 21 capacitance
Claims (1)
するスイッチングレギュレータ制御回路において、負荷
短絡保護用回路を内蔵することで、出力電圧の電圧値に
関わらず確実に過電流保護をおこなうことを特徴とした
スイッチングレギュレータ回路。In a switching regulator control circuit including an overcurrent detection circuit and a low voltage detection circuit, by incorporating a load short-circuit protection circuit, overcurrent protection is reliably performed regardless of the output voltage value. Switching regulator circuit characterized by the following.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2001100749A JP2002300773A (en) | 2001-03-30 | 2001-03-30 | Switching regulator circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2001100749A JP2002300773A (en) | 2001-03-30 | 2001-03-30 | Switching regulator circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JP2002300773A true JP2002300773A (en) | 2002-10-11 |
Family
ID=18954165
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2001100749A Withdrawn JP2002300773A (en) | 2001-03-30 | 2001-03-30 | Switching regulator circuit |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2002300773A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7576531B2 (en) | 2005-03-28 | 2009-08-18 | Rohm Co., Ltd. | Switching regulator and electronic device therewith |
| JP2017158399A (en) * | 2016-03-04 | 2017-09-07 | 株式会社デンソー | Switching power source device |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH05328711A (en) * | 1992-05-15 | 1993-12-10 | Fuji Electric Co Ltd | Short circuit protection network for dc-dc converter |
| JP2000245142A (en) * | 1999-02-19 | 2000-09-08 | Sharp Corp | Switching power supply |
-
2001
- 2001-03-30 JP JP2001100749A patent/JP2002300773A/en not_active Withdrawn
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH05328711A (en) * | 1992-05-15 | 1993-12-10 | Fuji Electric Co Ltd | Short circuit protection network for dc-dc converter |
| JP2000245142A (en) * | 1999-02-19 | 2000-09-08 | Sharp Corp | Switching power supply |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7576531B2 (en) | 2005-03-28 | 2009-08-18 | Rohm Co., Ltd. | Switching regulator and electronic device therewith |
| JP2017158399A (en) * | 2016-03-04 | 2017-09-07 | 株式会社デンソー | Switching power source device |
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