JP2001119932A - Switching power supply protection circuit - Google Patents
Switching power supply protection circuitInfo
- Publication number
- JP2001119932A JP2001119932A JP29334099A JP29334099A JP2001119932A JP 2001119932 A JP2001119932 A JP 2001119932A JP 29334099 A JP29334099 A JP 29334099A JP 29334099 A JP29334099 A JP 29334099A JP 2001119932 A JP2001119932 A JP 2001119932A
- Authority
- JP
- Japan
- Prior art keywords
- power supply
- circuit
- switching power
- protection circuit
- 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.)
- Granted
Links
Landscapes
- Dc-Dc Converters (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】この発明は交流電源から直流
電源を得る場合等に用いられるスイッチング電源の保護
回路に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching power supply protection circuit used for obtaining a DC power supply from an AC power supply.
【０００２】[0002]
【従来の技術】図３は従来のスイッチング電源の保護回
路の一例である。トランス１の一次側コイルにはスイッ
チング素子駆動回路１７により駆動されるスイッチング
素子１４が接続されている。スイッチング素子１４のエ
ミッタ出力とグランド間には過電流検出回路１６が挿入
されており、この過電流検出回路１６の出力はスイッチ
ング素子駆動回路１７に接続されている。トランス１の
二次側コイルは２つの出力＋Ｂ１，＋Ｂ２を備えており
＋Ｂ１には＋Ｂ２より大きい負荷が接続される。Ｄ１，
Ｄ２は整流用のダイオードであり、Ｃ１，Ｃ２は平滑用
コンデンサである。2. Description of the Related Art FIG. 3 shows an example of a conventional protection circuit for a switching power supply. The switching element 14 driven by the switching element drive circuit 17 is connected to the primary coil of the transformer 1. An overcurrent detection circuit 16 is inserted between the emitter output of the switching element 14 and the ground, and the output of the overcurrent detection circuit 16 is connected to a switching element drive circuit 17. The secondary coil of the transformer 1 has two outputs + B1 and + B2, and a load larger than + B2 is connected to + B1. D1,
D2 is a rectifying diode, and C1 and C2 are smoothing capacitors.
【０００３】以上のように構成されたスイッチング電源
の保護回路について、以下その動作を説明する。一次側
整流電圧入力端子からの入力電圧によりスイッチング素
子駆動回路１７がスイッチング素子１４を駆動する。こ
れにより一次側コイルにスイッチング電流が流れ、トラ
ンス二次側出力＋Ｂ１，＋Ｂ２から二次側コイルに電圧
が生じる。二次側コイルでコイル巻線同士等による部分
短絡（以下これをレアショートと称す）が生じると短絡
部分に異常過熱が生じる。レアショートが生じると、二
次側コイルの巻数が減少するため一次側コイル電流Ｉが
増加する。過電流検出回路１６はレアショート発生によ
り二次側コイルが異常過熱するときの電流を過電流とし
て検出し、スイッチング素子駆動回路１７にスイッチン
グ素子１４の駆動を停止させる。[0003] The operation of the protection circuit for a switching power supply configured as described above will be described below. The switching element drive circuit 17 drives the switching element 14 by the input voltage from the primary side rectified voltage input terminal. As a result, a switching current flows in the primary coil, and a voltage is generated in the secondary coil from the transformer secondary outputs + B1 and + B2. When a partial short circuit (hereinafter, referred to as a rare short circuit) occurs between the coil windings and the like in the secondary coil, abnormal overheating occurs in the short circuit portion. When a rare short circuit occurs, the primary coil current I increases because the number of turns of the secondary coil decreases. The overcurrent detection circuit 16 detects a current when the secondary coil abnormally overheats due to the occurrence of a rare short circuit as an overcurrent, and causes the switching element driving circuit 17 to stop driving the switching element 14.
【０００４】[0004]
【発明が解決しようとする課題】上記のような、多出力
スイッチング電源の保護回路では、過電流検出回路１６
により検出される一次側コイル電流Ｉの検出レベルがト
ランス二次側出力＋Ｂ１，＋Ｂ２のそれぞれのコイルが
異常加熱するときに一次側コイルに流れる電流の合計で
あるため、負荷が小さい出力＋Ｂ１のコイルでレアショ
ートが生じても過電流検出回路１６はこのときの一次側
コイル電流の増加を検出することは困難である。In the protection circuit for a multi-output switching power supply as described above, an overcurrent detection circuit 16 is provided.
Is the sum of the currents flowing through the primary side coils when the respective coils of the transformer secondary side outputs + B1 and + B2 are abnormally heated, so that the coil of the output + B1 with a small load is detected. Therefore, even if a rare short circuit occurs, it is difficult for the overcurrent detection circuit 16 to detect an increase in the primary side coil current at this time.
【０００５】この発明は、上述のような問題を解消する
ためになされたもので、複数の出力が存在するスイッチ
ング電源において、一次側コイルの過電流検出回路では
検出が困難な負荷が軽い二次側出力巻線に生じるレアシ
ョートを確実に検出し、トランスが異常過熱温度に至る
前に確実に安定して保護動作に至る保護回路を提供する
ことを目的とする。SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem. In a switching power supply having a plurality of outputs, a secondary load having a light load which is difficult to detect by an overcurrent detection circuit of a primary coil is provided. It is an object of the present invention to provide a protection circuit that reliably detects a rare short-circuit occurring in a side output winding and reliably and stably performs a protection operation before a transformer reaches an abnormally high temperature.
【０００６】[0006]
【課題を解決するための手段】本発明におけるスイッチ
ング電源の保護回路は、スイッチング素子を介して通電
される一次側コイルと複数の出力端子を有する二次側コ
イルとから構成されたトランスを備え、トランスの二次
側コイルの出力のうち負荷が最小の電圧を検出し、電圧
が所定値以下となった場合に前記スイッチング素子の駆
動を停止するものである。A protection circuit for a switching power supply according to the present invention comprises a transformer comprising a primary coil energized through a switching element and a secondary coil having a plurality of output terminals. The load of the output of the secondary coil of the transformer is detected as a minimum voltage, and when the voltage falls below a predetermined value, the driving of the switching element is stopped.
【０００７】[0007]
【発明の実施の形態】以下、この過負荷時の保護回路を
その実施の形態を示す図面に基づいて説明する。尚、従
来のものと同一または相当のものについては同一符号を
付し、説明を省略する。 実施の形態１．図１は本発明実施の形態におけるスイッ
チング電源の保護回路の構成を示す図である。図におい
て、１９は電圧検出回路でありトランス二次側出力＋Ｂ
２の電圧を抵抗Ｒ１，Ｒ２により分圧した電圧が入力さ
れる。また、電圧検出回路１９の出力はスイッチング素
子駆動回路１７に接続されている。BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an overload protection circuit according to an embodiment of the present invention. The same or corresponding components as those in the related art are denoted by the same reference numerals, and description thereof is omitted. Embodiment 1 FIG. FIG. 1 is a diagram showing a configuration of a protection circuit for a switching power supply according to an embodiment of the present invention. In the figure, reference numeral 19 denotes a voltage detection circuit which is a transformer secondary side output + B
2 is divided by resistors R1 and R2. The output of the voltage detection circuit 19 is connected to the switching element drive circuit 17.
【０００８】図１に示したスイッチング電源の保護回路
において、トランス二次側出力＋Ｂ２コイルがレアショ
ートするとレアショート発生部に定格電流を超える電流
が流れ、これにより＋Ｂ２の出力電圧が低下する。電圧
検出回路１９はレアショートにより＋Ｂ２の出力電圧が
所定値を下回って検出されるとスイッチング素子駆動回
路１７に、スイッチング素子１４の駆動を停止させる。
これによってトランス１は異常過熱状態に至らずに保護
される。例えば、＋Ｂ１および＋Ｂ２の出力電圧がそれ
ぞれ１８０Ｖ，８Ｖである場合を想定する。ここで、負
荷電力が小さい＋Ｂ２コイルにレアーショートが生じる
とレアーショート発生部に過電流が流れ、異常過熱が発
生する。レアーショートにより＋Ｂ２コイルに異常過熱
が生じるときの＋Ｂ２コイルの出力電圧を６Ｖとする
と、＋Ｂ出力電圧が６Ｖ以下になった場合、電圧検出回
路１９がスイッチング素子駆動回路１７にスイッチング
素子１４の駆動を停止する命令を送るよう、分圧抵抗Ｒ
１, Ｒ２および電圧検出回路１９の検出電圧レベルを設
定する。ここで、レアショート検出時の電圧低下レベル
は、電源トランス１の各２次巻線のレアショート発生時
において、温度上昇が規格内でおさまるような過電流レ
ベルを測定し、その時の電圧低下量に基づいて設定する
ことができる。In the protection circuit of the switching power supply shown in FIG. 1, when the transformer secondary-side output + B2 coil is short-circuited, a current exceeding the rated current flows in the rare-short generation section, and the output voltage of + B2 is reduced. The voltage detection circuit 19 causes the switching element drive circuit 17 to stop driving the switching element 14 when the output voltage of + B2 is detected to fall below a predetermined value due to a rare short.
Thereby, the transformer 1 is protected without reaching an abnormal overheating state. For example, assume that the output voltages of + B1 and + B2 are 180V and 8V, respectively. Here, if a short-circuit occurs in the + B2 coil with a small load power, an overcurrent flows in the rare-short generating section, and abnormal overheating occurs. Assuming that the output voltage of the + B2 coil is 6 V when abnormal overheating occurs in the + B2 coil due to a layer short, when the + B output voltage becomes 6 V or less, the voltage detection circuit 19 causes the switching element drive circuit 17 to drive the switching element 14. To send a command to stop,
1, R2 and the detection voltage level of the voltage detection circuit 19 are set. Here, the voltage drop level at the time of detecting a rare short is measured by measuring an overcurrent level at which a temperature rise falls within a standard when a rare short occurs in each secondary winding of the power transformer 1, and the voltage drop amount at that time. Can be set based on the
【０００９】また、出力が３系統以上あるものについて
も負荷が軽い二次側出力巻線に電圧検出回路を設けるこ
とで、電源トランス巻線のレアショートに対応できる。
また、負荷が軽い二次側出力が複数存在するには二次側
出力毎に電圧検出回路を複数設けてもよい。尚、図１の
電圧検出回路１９はマイコン等によって構成することも
できる。[0009] In addition, even for those having three or more outputs, by providing the voltage detection circuit on the secondary output winding having a light load, it is possible to cope with rare short-circuit of the power transformer winding.
Further, if there are a plurality of secondary outputs with a light load, a plurality of voltage detection circuits may be provided for each secondary output. Note that the voltage detection circuit 19 in FIG. 1 can also be constituted by a microcomputer or the like.
【００１０】また、図２に示すスイッチング電源の保護
回路のように出力に負荷が軽い負極性出力−Ｂ２が含ま
れる場合、負荷が最も大きい出力＋Ｂ１と出力−Ｂ２間
に分圧抵抗Ｒ１，Ｒ２を設け、分圧点にスイッチング素
子１５のベース入力を接続する構成としてもより。この
構成によれば、出力＋Ｂ３コイルにレアショートが発生
し、負極性電圧の低下により通常ローレベルのスイッチ
ング素子１５のベース入力がハイレベルとなることによ
り電流検出回路２０に電流が流れる。電流検出回路２０
はこのときスイッチング素子駆動回路１７にスイッチン
グ素子１４の駆動を停止させる。ここで、＋Ｂ１および
−Ｂ２の出力電圧がそれぞれ１８０Ｖ，−８Ｖである場
合を想定する。レアショートにより−Ｂ２コイルに異常
過熱が生じるときの−Ｂ２コイルの出力電圧を約−６Ｖ
とすると、抵抗Ｒ１，Ｒ２の値は例えば、それぞれ２５
０ＫΩ，１０ＫΩとすることができる。この場合、−Ｂ
２コイルにレアショートが発生し、−Ｂ２出力電圧の負
極性出力が−６Ｖより小さくなると、スイッチング素子
１５のベース入力電圧がオンレベルまで上昇し、電流検
出回路２０に電流が流れる。When the output includes a light output of the negative polarity output -B2 as in the protection circuit of the switching power supply shown in FIG. 2, the voltage dividing resistors R1 and R2 are connected between the output + B1 and the output -B2 with the largest load. Is provided, and the base input of the switching element 15 is connected to the voltage dividing point. According to this configuration, a rare short circuit occurs in the output + B3 coil, and the base input of the normally low-level switching element 15 becomes high level due to a decrease in the negative voltage, so that a current flows through the current detection circuit 20. Current detection circuit 20
Causes the switching element drive circuit 17 to stop driving the switching element 14 at this time. Here, it is assumed that the output voltages of + B1 and -B2 are 180V and -8V, respectively. The output voltage of the -B2 coil is approximately -6 V when abnormal overheating occurs in the -B2 coil due to a rare short circuit.
Then, the values of the resistors R1 and R2 are, for example, 25
0 KΩ and 10 KΩ can be set. In this case, -B
When a rare short occurs in the two coils and the negative output of the −B2 output voltage becomes smaller than −6 V, the base input voltage of the switching element 15 rises to the on level, and the current flows to the current detection circuit 20.
【００１１】[0011]
【発明の効果】本発明が提供するスイッチング電源の保
護回路は、複数の出力が存在するスイッチング電源にお
いて、一次側コイルの過電流検出回路では検出が困難な
負荷が軽い二次側出力巻線に生じるレアショートを確実
に検出し、トランスが異常過熱温度に至る前に確実に安
定して保護動作に至る保護回路を得ることができる。According to the protection circuit for a switching power supply provided by the present invention, in a switching power supply having a plurality of outputs, a secondary output winding having a light load which is difficult to detect by an overcurrent detection circuit of a primary coil is provided. It is possible to reliably detect a generated rare short circuit and obtain a protection circuit that reliably and stably reaches the protection operation before the transformer reaches an abnormal overheating temperature.
【図１】 本発明の実施の形態におけるスイッチング電
源の保護回路の構成を示す図である。FIG. 1 is a diagram showing a configuration of a protection circuit for a switching power supply according to an embodiment of the present invention.
【図２】 本発明の実施の形態におけるスイッチング電
源の保護回路の構成を示す図である。FIG. 2 is a diagram illustrating a configuration of a protection circuit for a switching power supply according to an embodiment of the present invention.
【図３】 従来の過負荷時の保護回路を示す図である。FIG. 3 is a diagram illustrating a conventional overload protection circuit.
１ トランス、１４，１５ スイッチング素子、１６
過電流検出回路、１７ スイッチング素子駆動回路、１
９ 電圧検出回路、＋Ｂ１，＋Ｂ２，−Ｂ２ トランス
二次側出力、Ｄ１，Ｄ２ 整流用ダイオード、Ｃ１，Ｃ
２ 平滑用コンデンサ、Ｒ１，Ｒ２ 抵抗。1 transformer, 14, 15 switching element, 16
Overcurrent detection circuit, 17 switching element drive circuit, 1
9 Voltage detection circuit, + B1, + B2, -B2 Transformer secondary output, D1, D2 Rectifying diode, C1, C
2 Smoothing capacitor, R1, R2 resistors.
Claims (1)
次側コイルと複数の出力端子を有する二次側コイルとか
ら構成されたトランスを備え、前記トランスの二次側コ
イルの出力のうち負荷が最小の電圧を検出し、前記電圧
が所定値以下となった場合に前記スイッチング素子の駆
動を停止することを特徴とするスイッチング電源の保護
回路。1. A transformer comprising a primary coil energized through a switching element and a secondary coil having a plurality of output terminals, wherein a load of the secondary coil of the transformer is minimized. A protection circuit for a switching power supply, wherein the voltage of the switching power supply is detected and the driving of the switching element is stopped when the voltage falls below a predetermined value.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP29334099A JP3790392B2 (en) | 1999-10-15 | 1999-10-15 | Switching power supply protection circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP29334099A JP3790392B2 (en) | 1999-10-15 | 1999-10-15 | Switching power supply protection circuit |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| JP2001119932A true JP2001119932A (en) | 2001-04-27 |
| JP2001119932A5 JP2001119932A5 (en) | 2005-06-09 |
| JP3790392B2 JP3790392B2 (en) | 2006-06-28 |
Family
ID=17793547
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP29334099A Expired - Fee Related JP3790392B2 (en) | 1999-10-15 | 1999-10-15 | Switching power supply protection circuit |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3790392B2 (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2006288192A (en) * | 2005-04-01 | 2006-10-19 | Harmer + Simmons (France) Sas | Converter having plural channels |
| JP2009268226A (en) * | 2008-04-24 | 2009-11-12 | Yokogawa Electric Corp | Switching power supply |
| EP2164160A2 (en) | 2008-09-11 | 2010-03-17 | Funai Electric Co., Ltd. | Voltage reduction detection circuit and switching power supply system |
| JP2013042607A (en) * | 2011-08-18 | 2013-02-28 | Murata Mfg Co Ltd | Power reception device and power transmission system |
-
1999
- 1999-10-15 JP JP29334099A patent/JP3790392B2/en not_active Expired - Fee Related
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2006288192A (en) * | 2005-04-01 | 2006-10-19 | Harmer + Simmons (France) Sas | Converter having plural channels |
| JP2009268226A (en) * | 2008-04-24 | 2009-11-12 | Yokogawa Electric Corp | Switching power supply |
| EP2164160A2 (en) | 2008-09-11 | 2010-03-17 | Funai Electric Co., Ltd. | Voltage reduction detection circuit and switching power supply system |
| JP2010068631A (en) * | 2008-09-11 | 2010-03-25 | Funai Electric Co Ltd | Reduced-voltage detecting circuit and switching power-supply system |
| JP4678429B2 (en) * | 2008-09-11 | 2011-04-27 | 船井電機株式会社 | Switching power supply system |
| US8289740B2 (en) | 2008-09-11 | 2012-10-16 | Funai Electric Co., Ltd. | Voltage reduction detection circuit and switching power supply system |
| JP2013042607A (en) * | 2011-08-18 | 2013-02-28 | Murata Mfg Co Ltd | Power reception device and power transmission system |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3790392B2 (en) | 2006-06-28 |
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