JP4318372B2 - Switching power supply - Google Patents
Switching power supply Download PDFInfo
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- JP4318372B2 JP4318372B2 JP2000063799A JP2000063799A JP4318372B2 JP 4318372 B2 JP4318372 B2 JP 4318372B2 JP 2000063799 A JP2000063799 A JP 2000063799A JP 2000063799 A JP2000063799 A JP 2000063799A JP 4318372 B2 JP4318372 B2 JP 4318372B2
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- power supply
- switching power
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Description
【０００１】
【発明の属する技術分野】
本発明は、２次側直流電圧を半導体スイッチによりオン／オフ制御する制御回路を備えるスイッチング電源装置に関するものである。
【０００２】
【従来の技術】
図５は、従来使用されているスイッチング電源であり、制御端子に信号を印加し、オン／オフ制御素子Ｑ３をオン／オフすることにより、最終的に半導体スイッチＱ２をオン／オフし、出力電圧を制御するものである。
【０００３】
【発明が解決しようとする課題】
従来回路の図５では、２次側に過電流が発生すると過電流検出回路Ａで検出され、制御回路にフィードバックされ、２次側の直流電圧が低下すると、半導体スイッチＱ２の飽和状態を維持することができず、半導体スイッチＱ２を流れる電流と直流電圧との積により電力損失が発生し、発熱を引き起こし、信頼性が低下するという問題があった。
【０００４】
【課題を解決するための手段】
本発明は、上記の課題を解決したものであり、２次側に過電流が発生し２次側の直流電圧が低下しても、半導体スイッチＱ２の飽和状態を維持することにより、半導体スイッチＱ２の発熱を抑えようとするものである。
すなわち、出力トランスＴの１次側に、整流回路ＢＤと平滑コンデンサＣ１からなる整流・平滑回路とインバータＱ１とを直列接続し、上記出力トランスＴの２次側に半導体スイッチＱ２を介して接続される出力端子と、該半導体スイッチＱ２にオン／オフ制御素子Ｑ３を介して接続される制御端子とを備えてなるスイッチング電源において、
１次側または２次側に過電流検出回路Ａを設け、上記出力トランスＴの２次巻線Ｎ２の一端とオン／オフ制御素子Ｑ３のエミッタとの間に整流ダイオードＤ２と抵抗Ｒ２とを直列接続し、該抵抗Ｒ２のオン／オフ制御素子Ｑ３側に定電圧ダイオードＺＤ１、整流ダイオードＤ２側にコンデンサＣ３を接続し、該コンデンサＣ３と上記定電圧ダイオードＺＤ１とを上記２次巻線Ｎ２の他端に接続してなる定電圧回路を設けたことを特徴とするスイッチング電源である。
【０００５】
また、上記スイッチング電源において、抵抗Ｒ２に代えて三端子レギュレータＢを、定電圧ダイオードＺＤ１に代えてコンデンサＣ４を設けたことを特徴とするスイッチング電源である。
【０００６】
【発明の実施の形態】
図１に示すスイッチング電源において、２次側に過電流検出回路Ａを設け、出力トランスＴの２次巻線Ｎ２の一端とオン／オフ制御素子Ｑ３のエミッタとの間に整流ダイオードＤ２と抵抗Ｒ２を直列接続し、該抵抗Ｒ２のオン／オフ制御素子Ｑ３側に低電圧ダイオードＺＤ１、整流ダイオードＤ２側にコンデンサＣ３を接続し、該コンデンサＣ３と上記定電圧ダイオードＺＤ１とを上記２次巻線Ｎ２の他端に接続した定電圧回路を設ける。
出力ショート等により２次側に過電流が発生すると、過電流検出回路Ａで電流が検出され、１次側の制御回路にフィードバックされて、過電流保護のため、出力電圧が低下し、半導体スイッチＱ２のエミッタ電位も低下する。
その結果、半導体スイッチＱ２をドライブ（飽和状態を維持）するだけの電圧が発生せず、コレクタ−エミッタ間の電圧と電流の積による電力損失の発生−発熱が生ずるところを、２次側の定電圧回路からの負の電位の発生により、半導体スイッチＱ２の飽和状態が維持され、半導体スイッチＱ２の発熱を抑えることができる。
（このときの条件：最大出力電流ＩＯ（ＭＡＸ）＜ＩＢ・ｈＦＥＩＢ：ベース電流、ｈＦＥ：電流増幅率）
【０００７】
【実施例】
以下、本発明の実施例について図面を参照しながら詳細に説明する。図１に本発明の実施例による自励発振型のスイッチング電源を示す。図１は、過電流検出回路を２次側に設けたものであり、図２は１次側に設けたものである。
図１においては、交流電圧ＡＣを整流回路ＢＤにて整流し、コンデンサＣ１にて平滑することにより得られる直流電圧を出力トランスＴの１次巻線Ｎ１に直列接続したインバータＱ１に印加し、該インバータＱ１のスイッチング動作にて出力トランスＴの２次巻線Ｎ２に現れる電圧を整流ダイオードＤ１により整流し、コンデンサＣ２により平滑し、得られた直流電圧を出力する。
１次側または２次側に過電流を検出する過電流検出回路Ａを設け、定電圧回路を２次巻線Ｎ２の一端およびオン／オフ制御素子Ｑ３のエミッタに接続する。このようにして構成した実施例によるスイッチング電源の出力電流−出力電圧特性を図４に示す。
２次側には直流電圧を半導体スイッチＱ２によりオン／オフする回路があり、制御端子に信号を印加しオン／オフ制御素子Ｑ３をオン／オフすることにより最終的に半導体スイッチＱ２をオン／オフし、出力電圧を制御する。
２次側に過電流が発生し、２次側の直流電圧が低下しても、オン／オフ制御素子Ｑ３のエミッタ端子に負の電位が印加されることにより、半導体スイッチＱ２の飽和状態を維持することが可能となり、半導体スイッチの損失を抑えることができる。このときの半導体スイッチＱ２における出力側インピーダンス−コレクタ・エミッタ間の電圧（ＶＣＥ）特性を図６に示す。図５に示す従来例の回路ではＱ２の飽和状態が維持できないのに対し本発明による実施例ではＱ２の飽和状態が維持されている。ここで、上記の負の電位については、インバータＱ１が発振し、出力トランスＴの２次巻線Ｎ２を一次巻線Ｎ１と同極性で、整流ダイオードＤ２により整流し、コンデンサＣ３で平滑することで負の電位を簡単に発生させることができる。
なお、上記の図１においては、過電流検出回路を２次側に設けたが、図２のように１次側に設けても、同様の効果を得ることができる。また、これらの定電圧回路の代わりに、図３のような定電圧回路を用いても、同様の効果を得ることができる。
【０００８】
【発明の効果】
本発明により、２次側に過電流が発生し、２次側の直流電圧が低下しても半導体スイッチの飽和状態を維持し、電力損失を抑制し、発熱を抑えることができる。
【図面の簡単な説明】
【図１】本発明の実施例によるスイッチング電源の回路図である。
【図２】本発明の他の実施例によるスイッチング電源の回路図である。
【図３】本発明の他の実施例によるスイッチング電源の回路図である。
【図４】本発明の実施例によるスイッチング電源の出力電流−出力電圧特性図である。
【図５】従来例によるスイッチング電源の回路図である。
【図６】半導体スイッチＱ２における出力側インピーダンス−コレクタ・エミッタ間の電圧（ＶＣＥ）特性図である。
【符号の説明】
ＡＣ 交流電源
ＢＤ 整流回路
Ｔ 出力トランス
Ｎ１ １次巻線
Ｎ２ ２次巻線
Ｑ１ インバータ
Ｑ２ 半導体スイッチ
Ｑ３ オン／オフ制御素子
Ｃ１、Ｃ２ 平滑コンデンサ
Ｃ３、Ｃ４ コンデンサ
Ｄ１、Ｄ２ 整流ダイオード
Ｒ１、Ｒ２ 抵抗
ＺＤ１ 定電圧ダイオード
Ａ 過電流検出回路
Ｂ 三端子レギュレータ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a switching power supply device including a control circuit for controlling on / off of a secondary side DC voltage using a semiconductor switch.
[0002]
[Prior art]
FIG. 5 shows a switching power supply that has been conventionally used. By applying a signal to the control terminal and turning on / off the on / off control element Q3, the semiconductor switch Q2 is finally turned on / off, and the output voltage Is to control.
[0003]
[Problems to be solved by the invention]
In FIG. 5 of the conventional circuit, when an overcurrent is generated on the secondary side, it is detected by the overcurrent detection circuit A and fed back to the control circuit. When the DC voltage on the secondary side decreases, the saturation state of the semiconductor switch Q2 is maintained. However, there is a problem in that power loss occurs due to the product of the current flowing through the semiconductor switch Q2 and the DC voltage, heat is generated, and reliability is lowered.
[0004]
[Means for Solving the Problems]
The present invention solves the above-described problem. Even when an overcurrent occurs on the secondary side and the DC voltage on the secondary side decreases, the semiconductor switch Q2 is maintained in a saturated state, whereby the semiconductor switch Q2 is maintained. It is intended to suppress the heat generation.
That is, a rectifying / smoothing circuit composed of a rectifying circuit BD and a smoothing capacitor C1 and an inverter Q1 are connected in series to the primary side of the output transformer T, and connected to the secondary side of the output transformer T via a semiconductor switch Q2. A switching power supply comprising an output terminal connected to the semiconductor switch Q2 via an on / off control element Q3,
An overcurrent detection circuit A is provided on the primary side or the secondary side, and a rectifier diode D2 and a resistor R2 are connected in series between one end of the secondary winding N2 of the output transformer T and the emitter of the on / off control element Q3. The resistor R2 is connected to the constant voltage diode ZD1 on the on / off control element Q3 side, and the capacitor C3 is connected to the rectifier diode D2 side. The capacitor C3 and the constant voltage diode ZD1 are connected to the secondary winding N2. A switching power supply comprising a constant voltage circuit connected to an end.
[0005]
The switching power supply is characterized in that a three-terminal regulator B is provided in place of the resistor R2, and a capacitor C4 is provided in place of the constant voltage diode ZD1.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
In the switching power supply shown in FIG. 1, an overcurrent detection circuit A is provided on the secondary side, and a rectifier diode D2 and a resistor R2 are provided between one end of the secondary winding N2 of the output transformer T and the emitter of the on / off control element Q3. Are connected in series, a low voltage diode ZD1 is connected to the on / off control element Q3 side of the resistor R2, and a capacitor C3 is connected to the rectifier diode D2 side. The capacitor C3 and the constant voltage diode ZD1 are connected to the secondary winding N2. A constant voltage circuit connected to the other end is provided.
If an overcurrent occurs on the secondary side due to an output short, etc., the current is detected by the overcurrent detection circuit A and fed back to the control circuit on the primary side, and the output voltage drops for overcurrent protection. The emitter potential of Q2 also decreases.
As a result, a voltage sufficient for driving the semiconductor switch Q2 (maintaining a saturated state) is not generated, and the generation of power loss due to the product of the voltage between the collector and the emitter and the generation of heat is generated. Due to the generation of the negative potential from the voltage circuit, the saturation state of the semiconductor switch Q2 is maintained, and the heat generation of the semiconductor switch Q2 can be suppressed.
(The conditions in the: maximum output current I O (MAX) <I B · h FE I B: The base current, h FE: current gain)
[0007]
【Example】
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a self-excited oscillation type switching power supply according to an embodiment of the present invention. FIG. 1 shows an overcurrent detection circuit provided on the secondary side, and FIG. 2 shows an overcurrent detection circuit provided on the primary side.
In FIG. 1, a DC voltage obtained by rectifying an AC voltage AC by a rectifier circuit BD and smoothing it by a capacitor C1 is applied to an inverter Q1 connected in series to a primary winding N1 of an output transformer T. The voltage appearing in the secondary winding N2 of the output transformer T by the switching operation of the inverter Q1 is rectified by the rectifier diode D1, smoothed by the capacitor C2, and the obtained DC voltage is output.
An overcurrent detection circuit A for detecting an overcurrent is provided on the primary side or the secondary side, and a constant voltage circuit is connected to one end of the secondary winding N2 and the emitter of the on / off control element Q3. FIG. 4 shows the output current-output voltage characteristics of the switching power supply according to the embodiment configured as described above.
On the secondary side, there is a circuit for turning on / off the DC voltage by the semiconductor switch Q2, and finally the semiconductor switch Q2 is turned on / off by applying a signal to the control terminal and turning on / off the control element Q3. And control the output voltage.
Even if an overcurrent occurs on the secondary side and the DC voltage on the secondary side decreases, a negative potential is applied to the emitter terminal of the on / off control element Q3, thereby maintaining the saturated state of the semiconductor switch Q2. It is possible to suppress the loss of the semiconductor switch. FIG. 6 shows the output side impedance-collector-emitter voltage (V CE ) characteristic in the semiconductor switch Q2 at this time. In the conventional circuit shown in FIG. 5, the saturation state of Q2 cannot be maintained, whereas in the embodiment according to the present invention, the saturation state of Q2 is maintained. Here, with respect to the negative potential, the inverter Q1 oscillates, the secondary winding N2 of the output transformer T has the same polarity as the primary winding N1, is rectified by the rectifier diode D2, and smoothed by the capacitor C3. Negative potential can be easily generated.
Although the overcurrent detection circuit is provided on the secondary side in FIG. 1 described above, the same effect can be obtained by providing it on the primary side as shown in FIG. The same effect can be obtained by using a constant voltage circuit as shown in FIG. 3 instead of these constant voltage circuits.
[0008]
【The invention's effect】
According to the present invention, even if an overcurrent occurs on the secondary side and the DC voltage on the secondary side decreases, the semiconductor switch is maintained in a saturated state, power loss can be suppressed, and heat generation can be suppressed.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of a switching power supply according to an embodiment of the present invention.
FIG. 2 is a circuit diagram of a switching power supply according to another embodiment of the present invention.
FIG. 3 is a circuit diagram of a switching power supply according to another embodiment of the present invention.
FIG. 4 is an output current-output voltage characteristic diagram of a switching power supply according to an embodiment of the present invention.
FIG. 5 is a circuit diagram of a switching power supply according to a conventional example.
6 is an output side impedance-collector-emitter voltage (V CE ) characteristic diagram of the semiconductor switch Q2. FIG.
[Explanation of symbols]
AC AC power supply BD Rectifier circuit T Output transformer N1 Primary winding N2 Secondary winding Q1 Inverter Q2 Semiconductor switch Q3 On / off control element C1, C2 Smoothing capacitor C3, C4 Capacitor D1, D2 Rectifier diode R1, R2 Resistor ZD1 constant Voltage diode A Overcurrent detection circuit B Three-terminal regulator
Claims (2)
１次側または２次側に過電流検出回路を設け、上記出力トランスの２次巻線の一端とオン／オフ制御素子のエミッタとの間に整流ダイオードと抵抗とを直列接続し、該抵抗のオン／オフ制御素子側に定電圧ダイオード、整流ダイオード側にコンデンサを接続し、該コンデンサと上記定電圧ダイオードとを上記２次巻線の他端に接続してなる定電圧回路を設けたことを特徴とするスイッチング電源。A rectifier / smoothing circuit comprising a rectifier circuit and a smoothing capacitor and an inverter are connected in series to the primary side of the output transformer, an output terminal connected to the secondary side of the output transformer via a semiconductor switch, and the semiconductor switch A switching power supply comprising a control terminal connected via an on / off control element to
An overcurrent detection circuit is provided on the primary side or the secondary side, and a rectifier diode and a resistor are connected in series between one end of the secondary winding of the output transformer and the emitter of the on / off control element. A constant voltage circuit is provided in which a constant voltage diode is connected to the on / off control element side, a capacitor is connected to the rectifier diode side, and the capacitor and the constant voltage diode are connected to the other end of the secondary winding. A switching power supply.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2000063799A JP4318372B2 (en) | 2000-03-08 | 2000-03-08 | Switching power supply |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2000063799A JP4318372B2 (en) | 2000-03-08 | 2000-03-08 | Switching power supply |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2001258247A JP2001258247A (en) | 2001-09-21 |
| JP4318372B2 true JP4318372B2 (en) | 2009-08-19 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2000063799A Expired - Fee Related JP4318372B2 (en) | 2000-03-08 | 2000-03-08 | Switching power supply |
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| Country | Link |
|---|---|
| JP (1) | JP4318372B2 (en) |
-
2000
- 2000-03-08 JP JP2000063799A patent/JP4318372B2/en not_active Expired - Fee Related
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| Publication number | Publication date |
|---|---|
| JP2001258247A (en) | 2001-09-21 |
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