JP3656779B2 - DC-DC converter - Google Patents

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JP3656779B2
JP3656779B2 JP18722196A JP18722196A JP3656779B2 JP 3656779 B2 JP3656779 B2 JP 3656779B2 JP 18722196 A JP18722196 A JP 18722196A JP 18722196 A JP18722196 A JP 18722196A JP 3656779 B2 JP3656779 B2 JP 3656779B2
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政和 鷁頭
一男 黒木
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Fuji Electric Co Ltd
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Fuji Electric Systems Co Ltd
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Description

【０００１】
【発明の属する技術分野】
この発明は、直流電源から絶縁された直流電力を取り出す直流−直流変換装置に関する。
【０００２】
【従来の技術】
図２４に１石フォワード型直流−直流変換装置の従来例を示す。
同図に示すように、直流電源１の正極側端子には変圧器４の一次巻線４１とリセット巻線４２との接続点が、変圧器４の一次巻線４１の他方の端子と直流電源１の負極側端子間には半導体スイッチ素子２Ａが、変圧器４のリセット巻線４２の他方の端子と直流電源１の負極側端子間にはダイオード３Ａが、変圧器４の二次巻線４３には整流回路５が、整流回路５には平滑フィルタ（平滑回路）６がそれぞれ接続されて構成されている。
【０００３】
図２５に図２４の動作波形を示す（図２４のような回路とその動作は、例えば１９８４年誠文堂新光社発行「スイッチングレギュレータの設計方法とパワーデバイスの使いかた」１８〜１９頁，９５〜９９頁の記載等により良く知られている）。
いま、半導体スイッチ素子２Ａがオンの期間▲１▼に変圧器４を正方向に励磁し、整流回路５および平滑フィルタ６を介して負荷に直流電力を供給する。これに対し、半導体スイッチ素子２Ａがオフの期間▲２▼には変圧器４の励磁エネルギーが、リセット巻線４２およびダイオード３Ａを介して直流電源１に回生される。
【０００４】
図２４の回路では、半導体スイッチ素子２Ａのターンオフ時、半導体スイッチ素子２Ａのはね上がり電圧を抑制するとともに、電圧上昇率（ｄｖ／ｄｔ）を小さくしてスイッチング損失を低減するため、半導体スイッチ素子２Ａに対しダイオード７１とコンデンサ７２とを直列接続し、ダイオード７１に並列に放電抵抗７３を接続したスナバ回路７を並列に接続している。これにより、コンデンサ７２が吸収したエネルギーは、次に半導体スイッチ素子２Ａがオンしている期間に、放電抵抗７３へ放出される。
【０００５】
【発明が解決しようとする課題】
図２４の回路においては、スナバコンデンサが吸収したエネルギーは、次に半導体スイッチ素子がオンしたとき、放電抵抗へ放出され損失となる。いま、放電抵抗の損失をＰ、スナバコンデンサの静電容量をＣ、直流電源の電圧をＥ、変圧器のリセット電圧をＶｒ、半導体スイッチ素子のはね上がり電圧をΔＶ、半導体スイッチ素子の動作周波数をｆとすると、
Ｐ＝（１／２）×Ｃ×（Ｅ＋Ｖｒ＋ΔＶ）2 ×ｆ
となる。したがって、直流電源の電圧Ｅ、変圧器のリセット電圧Ｖｒおよび半導体スイッチ素子の動作周波数ｆが高くなると、放電抵抗における発生損失が大きくなるため、大形で高価なスナバ回路が必要となるだけでなく、装置の変換効率が低下するという問題がある。
したがって、この発明の課題はスナバ回路を大形化せず、装置の変換効率を低下させないようにすることにある。
【０００６】
【課題を解決するための手段】
このような課題を解決すべく、請求項１の発明では直流電源と、一次側にリセット巻線を持つ変圧器と、この変圧器の二次側に接続される整流回路と、その整流出力を平滑化する平滑回路とからなり、直流電源から絶縁された直流電力を取り出す直流−直流変換装置において、第１のダイオードの一方の端子と第１の半導体スイッチ素子の一方の端子とを直列接続した第１の直列アームと、第２の半導体スイッチ素子の一方の端子と第２のダイオードの一方の端子とを直列接続した第２の直列アームと、第１のスナバ回路とをそれぞれ並列に接続するとともに、前記変圧器一次巻線のリセット巻線を接続していない側の端子を前記第１の直列アームの接続点に、また、前記変圧器リセット巻線の一次巻線を接続していない側の端子を前記第２の直列アームの接続点に、さらには、前記直流電源を変圧器の一次巻線とリセット巻線の接続点と前記第１の半導体スイッチ素子と前記第２のダイオードの接続点との間に並列に、それぞれ接続する。
【０００７】
請求項１の発明の如くすることにより、第１の半導体スイッチ素子のターンオフ時、第１のスナバ回路を構成するコンデンサは（Ｅ＋Ｖｒ）にクランプされるため、第１のスナバ回路が吸収するエネルギーＰ１は、
Ｐ１＝（１／２）×Ｃ×ΔＶ2 ×ｆ
と、小さくなる。また、第１の半導体スイッチ素子がオンしている期間に第２のスイッチ素子をオンさせることにより、第１のスナバ回路が吸収したエネルギーＰ１を負荷に放出することができる。
【０００８】
請求項２の発明では、請求項１の発明に対し、スナバダイオードとスナバコンデンサとを直列接続した第２のスナバ回路を前記第１の半導体スイッチ素子と並列に、また、補助ダイオードと補助リアクトルとの直列回路に補助コンデンサを直列接続した補助回路を前記スナバダイオードと並列に、さらに、回生用ダイオードを前記直列回路と前記補助コンデンサとの接続点と前記第２の半導体スイッチ素子の並列接続点との間にそれぞれ接続して構成する。
【０００９】
請求項２の発明の如くすることにより、第１の半導体スイッチ素子のターンオフ時、スナバコンデンサによって第１の半導体スイッチ素子の電圧上昇率を抑制し、スイッチング損失を低減する。次に、第１の半導体スイッチ素子がオンの期間に、スナバコンデンサに蓄えられている電荷を補助回路で吸収し、補助コンデンサに移す。さらに、第１の半導体スイッチ素子がオフしている期間に、補助コンデンサに蓄えられている電荷を、回生ダイオードを介して第１のスナバ回路に移す。そして、第１の半導体スイッチ素子がオンしている期間は、第２の半導体スイッチ素子をオンすることで、第１のスナバ回路に吸収したエネルギーを負荷に放出する。
【００１０】
請求項３の発明では、請求項１または２の発明で、第２の半導体スイッチ素子のオン期間を、第１のスナバ回路を構成するコンデンサの静電容量と変圧器の漏れインダクタンスとで決まる共振周波数のほぼ１／２とする。これにより、第２の半導体スイッチ素子には、第１のスナバ回路を構成するコンデンサの静電容量と変圧器の漏れインダクタンスとで決まる周期の正弦波状の電流が流れるが、そのオン期間を共振周期の約１／２とし、ターンオフ時の０Ａ付近で電流を遮断することにより、スイッチング損失を低減する。
【００１１】
請求項４の発明では、第１のダイオードと第１の半導体スイッチ素子とを直列接続した第１の直列アームと、第２の半導体スイッチ素子と第２のダイオードとを直列接続した第２の直列アームと、直流電源とを互いに並列に接続し、変圧器一次巻線を前記第１の直列アームの直列接続点と、前記第２の直列アームの直列接続点との間に接続するとともに、変圧器の二次巻線には整流回路、この整流回路には平滑回路をそれぞれ接続してなる直流−直流変換装置において、
前記第１の半導体スイッチ素子と第２の半導体スイッチ素子のそれぞれに、スナバダイオードとスナバコンデンサとを直列接続したスナバ回路をそれぞれ並列に、また、前記スナバダイオードのそれぞれには補助ダイオードと補助リアクトルとを直列接続した直列回路に補助コンデンサを直列接続した補助回路を並列に、さらに回生ダイオードを前記直列回路と前記補助コンデンサとの接続点と、前記第１，第２の直列アームの並列接続点との間にそれぞれ接続して構成する。
【００１２】
請求項５の発明では、半導体スイッチ素子とダイオードとを逆並列接続した２組のスイッチング素子を直列接続した第１の直列アームと、コンデンサを直列接続した第２の直列アームと、直流電源とを互いに並列に接続し、変圧器一次巻線を前記第１の直列アームの直列接続点と、前記第２の直列アームの直列接続点との間に接続するとともに、変圧器の二次巻線には整流回路、この整流回路には平滑回路をそれぞれ接続してなる直流−直流変換装置において、
前記スイッチング素子のそれぞれには、スナバダイオードとスナバコンデンサとを直列接続したスナバ回路を並列に、また、前記スナバダイオードのそれぞれには、補助ダイオードと補助リアクトルとを直列接続した直列回路に補助コンデンサを直列接続した補助回路を並列に、さらに回生ダイオードを前記直列回路と前記補助コンデンサとの接続点と、前記第１，第２の直列アームの並列接続点との間にそれぞれ接続して構成する。
【００１３】
請求項６の発明では、半導体スイッチ素子とダイオードとを逆並列接続した２組のスイッチング素子を直列接続した第１の直列アームと、コンデンサを直列接続した第２の直列アームと、直流電源とを互いに並列に接続し、変圧器一次巻線を前記第１の直列アームの直列接続点と、前記第２の直列アームの直列接続点との間に接続するとともに、変圧器の二次巻線には整流回路、この整流回路には平滑回路をそれぞれ接続してなる直流−直流変換装置において、
前記スイッチング素子と前記変圧器一次巻線の接続点との間に補助リアクトルをそれぞれ直列に、前記スイッチング素子のそれぞれには、スナバダイオードとスナバコンデンサとを直列接続したスナバ回路を並列に、補助ダイオードと補助コンデンサとを直列接続した補助回路を前記スナバ回路の直列接続点と前記補助リアクトルと前記変圧器一次巻線の接続点との接続点間に、回生ダイオードを前記補助回路の直列接続点と前記第１，第２の直列アームの並列接続点間にそれぞれ接続して構成する。
【００１４】
上記請求項４〜６の発明では、半導体スイッチ素子のターンオフ時には、スナバコンデンサによって上記半導体スイッチ素子の電圧上昇率を抑制し、スイッチング損失を低減させる。次に、半導体スイッチ素子がオンしている期間には、上記スナバコンデンサに蓄えられている電荷を補助回路で吸収し、補助コンデンサに移す。その後、半導体スイッチ素子がオフしている期間に、この補助コンデンサに蓄えられている電荷を、回生ダイオードを介して直流電源に回生することで、スナバ回路での発生損失を低減させる。
【００１５】
請求項７の発明では、第１のダイオードの一方の端子と第１の半導体スイッチ素子の一方の端子とを直列接続した第１の直列アームと、第２の半導体スイッチ素子の一方の端子と第２のダイオードの一方の端子とを直列接続した第２の直列アームと、第１のスナバ回路とをそれぞれ並列に接続するとともに、中間端子を備えた変圧器一次巻線の一方の端子を前記第１の直列アームの直列接続点に、前記変圧器一次巻線の他方の端子を前記第２の直列アームの直列接続点にそれぞれ接続し、また、直流電源を３端子スイッチの第１の端子と前記第１の半導体スイッチ素子と前記第２のダイオードとの並列接続点間に、前記３端子スイッチの第２の端子を前記変圧器の中間端子に、前記３端子スイッチの第３の端子を前記第１のダイオードと前記第２の半導体スイッチ素子との並列接続点間にそれぞれ接続し、さらには、入力電圧検出回路を前記直流電源と並列に、制御回路を前記入力電圧検出回路と前記３端子スイッチとの間に、前記変圧器の二次端子を整流回路に、この整流回路を平滑フィルタにそれぞれ接続している。
【００１６】
請求項８の発明では、第１の半導体スイッチ素子の一方の端子と第２の半導体スイッチ素子の一方の端子とを直列接続した第１の直列アームと、第３の半導体スイッチ素子の一方の端子と第４の半導体スイッチ素子の一方の端子とを直列接続した第２の直列アームと、第１のスナバ回路とをそれぞれ並列に接続するとともに、中間端子を備えた変圧器一次巻線の一方の端子を前記第１の直列アームの直列接続点に、前記変圧器一次巻線の他方の端子を前記第２の直列アームの直列接続点にそれぞれ接続し、また、直流電源を３端子スイッチの第１の端子と前記第１の半導体スイッチ素子と前記第３の半導体スイッチ素子との並列接続点間に、前記３端子スイッチの第２の端子を前記変圧器の中間端子に、前記３端子スイッチの第３の端子を前記第２の半導体スイッチ素子と前記第４の半導体スイッチ素子との並列接続点間にそれぞれ接続し、さらには、入力電圧検出回路を前記直流電源と並列に、制御回路を前記入力電圧検出回路と前記３端子スイッチとの間に、前記変圧器の二次端子を整流回路に、この整流回路を平滑フィルタにそれぞれ接続している。
【００１７】
上記請求項７の発明においては、第１のスナバダイオードと第１のスナバコンデンサとを直列接続した第２のスナバ回路を前記第１の半導体スイッチ素子と並列に、第１の補助ダイオードと第１の補助リアクトルとを直列接続した第１の直列回路と第１の補助コンデンサとを直列接続した第１の補助回路を前記第１のスナバダイオードと並列に、第１の回生ダイオードを前記第１の直列回路と第１の補助コンデンサとの接続点と前記第１のダイオードと前記第２の半導体スイッチ素子との並列接続点間に、第２のスナバダイオードと第２のスナバコンデンサとを直列接続した第３のスナバ回路を前記第２の半導体スイッチ素子と並列に、第２の補助ダイオードと第２の補助リアクトルとを直列接続した第２の直列回路と第２の補助コンデンサとを直列接続した第２の補助回路を前記第２のスナバダイオードと並列に、第２の回生ダイオードを前記第２の直列回路と第２の補助コンデンサとの接続点と前記第２のダイオードと前記第１の半導体スイッチ素子との並列接続点間に、それぞれ接続することができる（請求項９の発明）。
【００１８】
上記請求項８の発明においては、第１のスナバダイオードと第１のスナバコンデンサとを直列接続した第２のスナバ回路を前記第１の半導体スイッチ素子と並列に、第１の補助ダイオードと第１の補助リアクトルとを直列接続した第１の直列回路と第１の補助コンデンサとを直列接続した第１の補助回路を前記第１のスナバダイオードと並列に、第１の回生ダイオードと第１の回生リアクトルとを直列接続した第１の回生回路を前記第１の直列回路と前記第１の補助コンデンサとの接続点と前記第２の半導体スイッチ素子と第４の半導体スイッチ素子との並列接続点間に、第２のスナバダイオードと第２のスナバコンデンサとを直列接続した第３のスナバ回路を前記第２の半導体スイッチ素子と並列に、第２の補助ダイオードと第２の補助リアクトルとを直列接続した第２の直列回路と第２の補助コンデンサとを直列接続した第２の補助回路を前記第２のスナバダイオードと並列に、第２の回生ダイオードと第２の回生リアクトルとを直列接続した第２の回生回路を前記第２の直列回路と前記第２の補助コンデンサとの接続点と前記第１の半導体スイッチ素子と第３の半導体スイッチ素子との並列接続点間に、前記第２の直列アームについても上記と同じく、第４のスナバ回路、第５のスナバ回路、第３の補助回路、第４の補助回路、第３の回生回路および第４の回生回路をそれぞれ接続することができる（請求項１０の発明）。
【００１９】
【発明の実施の形態】
図１はこの発明の第１の実施の形態を示す回路図である。
図２４に示す従来例からスナバ回路７を省き、ダイオード３Ｂの一方の端子を変圧器一次巻線４１と半導体スイッチ素子２Ａとの接続点に、半導体スイッチ素子２Ｂの一方の端子を変圧器リセット巻線４２とダイオード３Ａとの接続点に、ダイオード３Ｂの他方の端子を半導体スイッチ素子２Ｂの他方の端子に、スナバ回路１３をダイオード３Ｂと半導体スイッチ素子２Ｂとの並列接続点と半導体スイッチ素子２Ａとダイオード３Ａの並列接続点との間にそれぞれ接続して構成する。
図３に図１の動作波形を示す。なお、図１の直流出力動作は図２４の場合と同様なので、以下では相違点のみを説明する。
すなわち、半導体スイッチ素子２Ａがターンオフしたとき、スナバ回路１３が変圧器４の漏れインダクタンスおよび配線インダクタンスに蓄えられたエネルギーを、ダイオード３Ｂを介して吸収する。次に、半導体スイッチ素子２Ａと半導体スイッチ素子２Ｂが同時にオンしている期間▲１▼に、スナバ回路１３に蓄えられている電荷を、スナバ回路１３→半導体スイッチ素子２Ｂ→変圧器リセット巻線４２→直流電源１の経路で放電し、スナバ回路１３で吸収したエネルギーを負荷に放出する。つまり、ダイオード３Ｂはスナバダイオードの役目を果たし、半導体スイッチ素子２Ｂは電力回生用として作用する。
図２に図１の変形例を示す。
これは、直流電源１の正極側端子を半導体スイッチ素子２Ａとダイオード３Ａとの接続点に、また、直流電源１の負極側端子を変圧器一次巻線４１と変圧器リセット巻線４２との接続点にそれぞれ接続した点が特徴で、機能的には図１と全く同じなので詳細は省略する。
【００２０】
図４はこの発明の第２の実施の形態を示す回路図、図６はその動作説明図である。
図１との相違点は、スナバダイオード７１とスナバコンデンサ７２を直列接続したスナバ回路７を半導体スイッチ素子２Ａと並列に、また、補助ダイオード８１と補助リアクトル８２を直列接続した直列回路と補助コンデンサ８３とを直列接続した補助回路８をスナバダイオード７１と並列に、さらに、回生ダイオード９を上記直列回路と補助コンデンサ８３の接続点と、ダイオード３Ｂと半導体スイッチ素子２Ｂとの接続点間に接続した点にある。
つまり、図１および図２に示す例では、スナバ回路１３により吸収したエネルギーを負荷に放出するようにしているため、スナバ回路１３では損失は殆ど発生しないが、半導体スイッチ素子２Ａのターンオフ時の電圧上昇率を抑制することができない。図４に示すものは、この問題を解決し得るようにするものである。
【００２１】
図６を参照して、半導体スイッチ素子２Ａに並列接続されたスナバコンデンサ７２の、電荷のエネルギー回生動作につき説明する。
いま、半導体スイッチ素子２Ａがターンオフする時、スナバコンデンサ７２が半導体スイッチ素子２Ａの電圧上昇率を抑制する。次に、半導体スイッチ素子２Ａがオンしている期間▲１▼，▲２▼に、スナバコンデンサ７２に蓄えられた電荷を、スナバコンデンサ７２→補助ダイオード８１→補助リアクトル８２→補助コンデンサ８３→半導体スイッチ素子２Ａの経路で、補助リアクトル８２および補助コンデンサ８３に放電する。
スナバコンデンサ７２が０Ｖまで放電すると、補助リアクトル８２に蓄えられたエネルギーにより、補助リアクトル８２→補助コンデンサ８３→スナバダイオード７１→補助ダイオード８１の経路で電流が流れ、補助コンデンサ８３にエネルギーを移す。さらに、半導体スイッチ素子２Ａがオフの期間▲３▼に、補助コンデンサ８３に蓄えられた電荷を、補助コンデンサ８３→回生ダイオード９→スナバ回路１３→直流電源１→変圧器一次巻線４１の経路でスナバ回路１３へと放出する。
そして、半導体スイッチ素子２Ａと２Ｂが同時にオンしている期間▲１▼に、スナバ回路１３に蓄えられている電荷を、スナバ回路１３→半導体スイッチ素子２Ｂ→変圧器リセット巻線４２→直流電源１の経路で放電し、スナバ回路１３で吸収したエネルギーを負荷に放出する。
図５に図４の変形例を示す。
すなわち、直流電源１の正極側端子を半導体スイッチ２Ａとダイオード３Ａとの接続点に、直流電源１の負極側端子を変圧器一次巻線４１と変圧器リセット巻線４２との接続点にそれぞれ接続する他は図４に示すものと全く同じなので、説明は省略する。
【００２２】
以上、いずれの例においても、半導体スイッチ素子２Ｂのオン期間、半導体スイッチ素子２Ｂには、スナバ回路１３を構成するコンデンサの静電容量と、変圧器４の漏れインダクタンスとによって決まる周期の正弦波状の電流が流れる。そこで、半導体スイッチ素子２Ｂのオン期間を、コンデンサの静電容量と変圧器の漏れインダクタンスで決まる共振周期の約１／２（図６に示す▲１▼期間参照）とし、半導体スイッチ素子２Ｂのターンオフ時、０Ａ付近で電流を遮断する。これにより、半導体スイッチ素子２Ｂのターンオフ時のスイッチング損失を低減することができる。
【００２３】
また、図４，図５はいずれも１石フォワード型コンバータにスナバ回路，補助回路および回生ダイオードを付加したものであるが、２石フォワード型やハーフブリッジ型のコンバータへの適用も考えられる。
図７は２石フォワード型に適用したもので、その基本回路に対して、スナバダイオード７１とスナバコンデンサ７２を直列接続したスナバ回路７を半導体スイッチ素子２Ａと並列に、また、補助ダイオード８１と補助リアクトル８２とを直列接続した第１の直列回路に補助コンデンサ８３を直列接続した補助回路８をスナバダイオード７１と並列に、さらに、回生ダイオード９を上記第１の直列回路と補助コンデンサ８３との接続点と、直流電源１の正極側端子との間にそれぞれ接続して構成される。同様に、スナバダイオード１０１とスナバコンデンサ１０２を直列接続したスナバ回路１０を半導体スイッチ素子２Ｂと並列に、また、補助ダイオード１１１と補助リアクトル１１２とを直列接続した第２の直列回路に補助コンデンサ１１３を直列接続した補助回路１１をスナバダイオード１０１と並列に、さらに、回生ダイオード１２を上記第２の直列回路と補助コンデンサ１１３との接続点と、直流電源１の負極側端子との間にそれぞれ接続して構成される。
【００２４】
図１０に図７の動作波形を示す。
ここでは、半導体スイッチ素子２Ａに付属するスナバコンデンサ７２の電荷エネルギーの回生動作について説明する。半導体スイッチ素子２Ａがターンオフするとき、スナバコンデンサ７２が半導体スイッチ素子２Ａの電圧上昇率を抑制する。次に、半導体スイッチ素子２Ａがオンしている期間▲１▼に、スナバコンデンサ７２に蓄えられている電荷をスナバコンデンサ７２→補助ダイオード８１→補助リアクトル８２→補助コンデンサ８３→半導体スイッチ素子２Ａの経路で、補助リアクトル８２および補助コンデンサ８３に放電する。スナバコンデンサ７２が０Ｖまで放電すると期間▲２▼に移行し、補助リアクトル８２に蓄えられたエネルギーにより、補助リアクトル８２→補助コンデンサ８３→スナバダイオード７１→補助ダイオード８１の経路で電流が流れ、補助コンデンサ８３にエネルギーを移す。次に、半導体スイッチ素子２Ａがオフの期間▲４▼に、補助コンデンサ８３に蓄えられている電荷は、補助コンデンサ８３→回生ダイオード９→直流電源１→回生ダイオード１２→補助コンデンサ１１→変圧器一次巻線４１の経路で放電し、直流電源１にエネルギーを回生する。半導体スイッチ素子２Ｂに付属するスナバ回路１０，補助回路１１および回生ダイオード１２についても、上記と同様に動作する。
【００２５】
図８はハーフブリッジ型に適用したもので、その基本回路に対して、スナバダイオード７１とスナバコンデンサ７２とを直列接続したスナバ回路７を半導体スイッチ素子２Ａと並列に、また、補助ダイオード８１と補助リアクトル８２とを直列接続した第１の直列回路に、補助コンデンサ８３を直列接続した補助回路８をスナバダイオード７１と並列に、さらに、回生ダイオード９を上記第１の直列回路と補助コンデンサ８３との接続点と、直流電源１の正極側端子との間にそれぞれ接続して構成されている。同様に、スナバダイオード１０１とスナバコンデンサ１０２を直列接続したスナバ回路１０を半導体スイッチ素子２Ｂと並列に、また、補助ダイオード１１１と補助リアクトル１１２とを直列接続した第２の直列回路に、補助コンデンサ１１３を直列接続した補助回路１１をスナバダイオード１０１と並列に、さらに、回生ダイオード１２を上記第２の直列回路と補助コンデンサ１１３との接続点と、直流電源１の負極側端子との間にそれぞれ接続して構成される。
【００２６】
図１１に図８の動作波形を示す。
ここでは、半導体スイッチ素子２Ａに付属するスナバコンデンサ７２の電荷エネルギーの回生動作について説明する。半導体スイッチ素子２Ａがターンオフするとき、スナバコンデンサ７２が半導体スイッチ素子２Ａの電圧上昇率を抑制する。次に、半導体スイッチ素子２Ａがオンしている期間▲１▼に、スナバコンデンサ７２に蓄えられている電荷をスナバコンデンサ７２→補助ダイオード８１→補助リアクトル８２→補助コンデンサ８３→半導体スイッチ素子２Ａの経路で、補助リアクトル８２および補助コンデンサ８３に放電する。スナバコンデンサ７２が０Ｖまで放電すると期間▲２▼に移行し、補助リアクトル８２に蓄えられたエネルギーにより、補助リアクトル８２→補助コンデンサ８３→スナバダイオード７１→補助ダイオード８１の経路で電流が流れ、補助コンデンサ８３にエネルギーを移す。次に、半導体スイッチ素子２Ａがオフの期間▲４▼に、補助コンデンサ８３に蓄えられている電荷は、補助コンデンサ８３→回生ダイオード９→直流電源１→コンデンサ３１Ａ→変圧器一次巻線４１の経路で放電し、コンデンサ３１Ａにエネルギーを回生する。コンデンサ３１Ａに蓄えられた電荷は、半導体スイッチ素子２Ｂがオンの期間▲５▼〜▲７▼に変圧器４を介して負荷に放出される。半導体スイッチ素子２Ｂに付属するスナバ回路１０，補助回路１１および回生ダイオード１２についても、上記と同様に動作する。
【００２７】
図９に図８の変形例を示す。
半導体スイッチ素子２Ａと変圧器一次巻線４１の接続点との間に補助リアクトル８２を、スナバダイオード７１とスナバコンデンサ７２とを直列接続したスナバ回路７を半導体スイッチ素子２Ａと並列に、また、補助ダイオード８１と補助コンデンサ８３とを直列接続した第３の直列回路をスナバダイオード７１とスナバコンデンサ７２との接続点と、補助リアクトル８２と変圧器一次巻線４１の接続点との間に、さらに、回生ダイオード９を上記第３の直列回路の接続点と、直流電源１の正極側端子との間にそれぞれ接続して構成される。同様に、半導体スイッチ素子２Ｂと変圧器一次巻線４１の接続点との間に補助リアクトル１１２を、スナバダイオード１０１とスナバコンデンサ１０２とを直列接続したスナバ回路１０を半導体スイッチ素子２Ｂと並列に、また、補助ダイオード１１１と補助コンデンサ１１３とを直列接続した第４の直列回路をスナバダイオード１０１とスナバコンデンサ１０２との接続点と、補助リアクトル１１２と変圧器一次巻線４１の接続点との間に、さらに、回生ダイオード１２を上記第４の直列回路の接続点と、直流電源１の負極側端子との間にそれぞれ接続して構成される。
この例は、図８に示すものでは、例えば無負荷時などでスナバコンデンサ７２に電荷が充分に蓄えられていない状態において半導体スイッチ素子２Ｂがオンすると、スナバコンデンサ７２を充電するため半導体スイッチ素子２Ｂに過大な電流が流れる。この例は、かかる不都合を生じさせないようにするものである。
【００２８】
以上では、直流電源電圧をほぼ一定として扱っているため、電圧の異なるものには適用できなくなるという問題が残されている。この点について、以下に説明する。図２６に従来の２石フォワード型直流−直流変換装置の従来例を示す。
すなわち、直流電源１の正極側端子には半導体スイッチ２Ｂの一方の端子とダイオード３Ｂの一方の端子が、また、直流電源１の負極側端子には半導体スイッチ２Ａの一方の端子とダイオード３Ａの一方の端子が、半導体スイッチ２Ｂの他方の端子には変圧器４の一次巻線４１の一方の端子とダイオード３Ａの他方の端子が、ダイオード３Ｂの他方の端子には半導体スイッチ２Ａの他方の端子と変圧器４の一次巻線４１の他方の端子が、さらに、変圧器４の二次巻線４３には整流回路５が、整流回路５には平滑フィルタ６がそれぞれ接続されている。
図２６の動作波形を図２８に示す。
半導体スイッチ２Ａおよび２Ｂをオンしている期間▲１▼に変圧器４を正方向に励磁し、整流回路５および平滑フィルタ６を介して負荷に電力を供給する。次に、半導体スイッチ２Ａ，２Ｂをオフしている期間▲２▼に、変圧器４の励磁エネルギーが変圧器一次巻線４１およびダイオード３Ａ，３Ｂを介して直流電源１に回生される。
【００２９】
図２７にフルブリッジ型直流−直流変換装置の従来例を示す。
同図において、直流電源１の正極側端子には半導体スイッチ２Ｃ，２Ｄの一方の端子が、直流電源１の負極側端子には半導体スイッチ２Ａ，２Ｂの一方の端子が、半導体スイッチ２Ｄの他方の端子には変圧器４の一次巻線４１の一方の端子と半導体スイッチ２Ｂの他方の端子が、半導体スイッチ２Ｃの他方の端子には半導体スイッチ２Ａの他方の端子と変圧器４の一次巻線４１の他方の端子が、変圧器４の二次巻線４３には整流回路５が、整流回路５には平滑フィルタ６がそれぞれ接続されている。
図２７の動作波形を図２９に示す。
半導体スイッチ２Ａ，２Ｄをオンしている期間▲１▼に変圧器４を正方向に励磁し、整流回路５および平滑フィルタ６を介して負荷に直流電力を供給する。次に、半導体スイッチ２Ｂ，２Ｃをオンしている期間▲３▼に変圧器４を負方向に励磁し、整流回路５および平滑フィルタ６を介して負荷に直流電力を供給する。
【００３０】
図２６の場合、直流電源１の最大電圧をＥｄ１，最小電圧をＥｄ２、電圧がＥｄ１のときの半導体スイッチ２Ａ，２Ｂがオンしている期間をＴＳ１、電圧がＥｄ２のときの半導体スイッチ２Ａ，２Ｂがオンしている期間をＴＳ２、半導体スイッチ２Ａ，２Ｂに流れる電流をｉ、このときの半導体スイッチ２Ａ，２Ｂの電圧降下をＶＳとすると、半導体スイッチ２Ａ，２Ｂがオンしている期間に発生する導通損失ＰＯＮは、
ＰＯＮ＝２×（ＶＳ×ｉ×ＴＯＮ）
となる。また、出力電圧が一定の場合はＴＳ１＜ＴＳ２となり、直流電源電圧がＥｄ２のときは半導体スイッチにおける導通損失が増加する。
また、変圧器の巻数比をｎ１：ｎ２、変圧器の二次巻線４３に発生する電圧をＶＴ２とすると、
ＶＴ２＝Ｅｄ×ｎ２／ｎ１
となる。整流回路を構成するダイオードは直流電源電圧がＥｄ１の場合においても耐圧を越えないように選定されるが、耐圧の高いダイオードは発生損失が大きく高価であるという問題がある。
【００３１】
直流電源を単相交流（ＡＣ）電源１００Ｖまたは２００Ｖから、ダイオード整流器により全波整流して得る例について具体的に説明する。
ＡＣ１００Ｖの場合Ｅｄ２＝９０Ｖ、ＡＣ２００Ｖの場合Ｅｄ１＝１８０Ｖとなる。このとき、ＴＳ２≒２×ＴＳ１となり、ＡＣ２００Ｖの場合と比較してＡＣ１００Ｖの場合の半導体スイッチの導通損失は約２倍となる。また、変圧器の巻数比を１：１とすると、整流器を構成するダイオードは１８０Ｖ以上の耐圧のものを選定するようにする。
この点は図２７の場合も同様で、直流電源電圧が低い場合はそれが高い場合に比べて、半導体スイッチ２Ａ，２Ｂ，２Ｃおよび２Ｄの導通損失が増加し、また、整流回路を構成するダイオードは直流電源電圧が最大の場合でも耐圧を越えないように選定しなければならない。
つまり、従来の直流−直流変換装置では、直流電源電圧の変動によって発生損失が大きくなり、整流回路を構成するダイオードに耐圧が大きく高価なものを要するという問題が残されている。
【００３２】
上記のような問題を回避することが可能な電圧適応型の直流−直流変換装置について、以下に説明する。図１２はかかる実施の形態（第５の実施の形態）を示す回路図である。
図２６との相違点は、変圧器４の一次巻線４１の一方の端子をダイオード３Ｂと半導体スイッチ２Ａとの直列接続点に、変圧器４の一次巻線４２の一方の端子を半導体スイッチ２Ｂとダイオード３Ａとの直列接続点に、スナバ回路１３をダイオード３Ｂと半導体スイッチ２Ｂとの並列接続点と半導体スイッチ２Ａとダイオード３Ａとの並列接続点間に、直流電源１の正極側端子をスイッチ３０の一方の端子に、直流電源１の負極側端子を半導体スイッチ２Ａとダイオード３Ａとの並列接続点に、スイッチ３０の第１の端子３０Ａを変圧器４の中間端子に、スイッチ３０の第２の端子３０Ｂをダイオード３Ｂと半導体スイッチ２Ｂとの並列接続点に、入力電圧検出回路４０を直流電源１と並列に、制御回路５０を入力電圧検出回路４０とスイッチ３０との間に、それぞれ接続して構成した点にある。
【００３３】
図１２の構成において、直流電源１の電圧を入力電圧検出回路４０により検出し、検出値が所定値以上になると制御回路５０により、スイッチ３０を端子３０Ｂ側に接続する。この場合は図２６と同じ２石コンバータ構成となり、図２６と同様の動作が行なわれる。これに対し、上記検出値が所定値以下のときは、スイッチ３０は端子３０Ａ側に接続され、図１と同様の１石コンバータ構成となる。
図２０に図１２でスイッチ３０を３０Ａ側に接続した場合の動作波形を示す。
すなわち、この回路の直流出力動作は、半導体スイッチ２Ａをオンしている期間▲１▼に変圧器４を正方向に励磁し、整流回路５および平滑回路６を介して負荷に直流電力を供給する。次に、半導体スイッチ２Ａをオフしている期間▲２▼に変圧器４の励磁エネルギーが、変圧器一次巻線４２およびダイオード３Ａを介して直流電源１に回生される。なお、巻線４２は１石コンバータの場合はリセット巻線として作用し、２石コンバータの場合は一次巻線として作用することになる。
【００３４】
ここで、第１のスナバ回路１３によるエネルギー回生動作について説明する。
半導体スイッチ２Ａがターンオフしたとき、第１のスナバ回路１３が変圧器４の漏れインダクタンスおよび配線インダクタンスに蓄えられたエネルギーを、ダイオード３Ｂを介して吸収する。次に、半導体スイッチ２Ａおよび２Ｂが同時にオンしている期間▲１▼に、第１のスナバ回路１３に蓄えられている電荷を、第１のスナバ回路１３→半導体スイッチ２Ｂ→変圧器一次巻線４２→直流電源１の経路で放電し、第１のスナバ回路１３で吸収したエネルギーを変圧器４の二次側に放出する。
図１３に図１２の変形例を示す。図１２との相違点は、直流電源１の正極端子を半導体スイッチ２Ａとダイオード３Ａとの並列接続点に、直流電源１の負極端子をスイッチ３０の一方の端子にそれぞれ接続した点にある。ただし、その動作は図１２と全く同様なので、説明は省略する。
【００３５】
図１４に電圧適応型の直流−直流変換装置の第２の実施の形態（第６の実施の形態）を示す。
これは、図２７の従来例に対応するもので、その相違点は、変圧器４の一次巻線４１の一方の端子を半導体スイッチ２Ａと半導体スイッチ２Ｃとの直列接続点に、変圧器４の一次巻線４２の一方の端子を半導体スイッチ２Ｂと半導体スイッチ２Ｄとの直列接続点に、スナバ回路１３を半導体スイッチ２Ｃと半導体スイッチ２Ｄとの並列接続点と半導体スイッチ２Ａと半導体スイッチ２Ｂとの並列接続点間に、直流電源１の正極側端子をスイッチ３０の一方の端子に、直流電源１の負極側端子を半導体スイッチ２Ａと半導体スイッチ２Ｂとの並列接続点に、スイッチ３０の第１の端子３０Ａを変圧器４の中間端子に、スイッチ３０の第２の端子３０Ｂを半導体スイッチ２Ｃと半導体スイッチ２Ｄとの並列接続点に、入力電圧検出回路４０を直流電源１と並列に、制御回路５０を入力電圧検出回路４０とスイッチ３０との間に、それぞれ接続して構成した点にある。
【００３６】
図１４の回路も、直流電源１の電圧を入力電圧検出回路４０により検出し、検出値が所定値以上になると制御回路５０により、スイッチ３０を端子３０Ｂ側に接続する。この場合は図２７と同じフルブリッジ構成となり、図２７と同様の動作が行なわれる。これに対し、上記検出値が所定値以下のときは、スイッチ３０は端子３０Ａ側に接続され、プッシュプル構成となる。
図２１に図１４でスイッチ３０を３０Ａ側に接続した場合の動作波形を示す。
すなわち、この回路の直流出力動作は、半導体スイッチ２Ａをオンしている期間▲１▼に変圧器４を正方向に励磁し、整流回路５および平滑回路６を介して負荷に直流電力を供給する。次に、半導体スイッチ２Ｂをオンしている期間▲３▼に変圧器４を負方向に励磁し、整流回路５および平滑回路６を介して負荷に直流電力を供給する。
【００３７】
ここで、第１のスナバ回路１３によるエネルギー回生動作について説明する。
半導体スイッチ２Ａがターンオフしたとき、第１のスナバ回路１３が変圧器４の漏れインダクタンスおよび配線インダクタンスに蓄えられたエネルギーを、半導体スイッチ２Ｃと逆並列接続されたダイオードを介して吸収する。次に、半導体スイッチ２Ａおよび２Ｄが同時にオンしている期間▲１▼に、第１のスナバ回路１３に蓄えられている電荷を、第１のスナバ回路１３→半導体スイッチ２Ｄ→変圧器一次巻線４２→直流電源１の経路で放電し、第１のスナバ回路１３で吸収したエネルギーを変圧器４の二次側に放出する。また、半導体スイッチ２Ｂのターンオフ時、および半導体スイッチ２Ｂと２Ｃが同時にオンしている期間についても上記と同様の動作が行なわれる。
図１５に図１４の変形例を示す。図１４との相違点は、直流電源１の正極端子を半導体スイッチ２Ａと２Ｂとの並列接続点に、直流電源１の負極端子をスイッチ３０の一方の端子にそれぞれ接続した点にある。ただし、その動作は図１４と全く同様なので、説明は省略する。
【００３８】
図１６は、図１２に示す半導体スイッチのターンオフ時の電圧上昇率を抑制し得る回路例（第７の実施の形態）である。
図１２との相違点は、スナバダイオード１４２とスナバコンデンサ１４１を直列接続した第２のスナバ回路１４を半導体スイッチ素子２Ａと並列に、また、補助ダイオード１５１と補助リアクトル１５２を直列接続した直列回路と補助コンデンサ１５３とを直列接続した補助回路１５をスナバダイオード１４２と並列に、さらに、回生ダイオード１５４を上記直列回路と補助コンデンサ１５３の接続点と、ダイオード３Ｂと半導体スイッチ素子２Ｂとの並列接続点間にそれぞれ接続し、加えて、半導体スイッチ素子２Ｂについても第３のスナバ回路１６，補助回路１７および回生ダイオード１７４を接続した点にある。
【００３９】
図２２に図１６のスイッチ３０を端子３０Ａ側に接続した場合の動作波形を示す。その直流出力動作については図１２と同様なので、ここでは半導体スイッチ素子２Ａに付属するスナバコンデンサ１４１のエネルギー回生動作について説明する。
半導体スイッチ素子２Ａがターンオフしたとき、スナバコンデンサ１４１が半導体スイッチ素子２Ａの電圧上昇率を抑制する。次に、半導体スイッチ素子２Ａがオンしている期間▲１▼〜▲３▼にスナバコンデンサ１４１に蓄えられている電荷を、スナバコンデンサ１４１→補助ダイオード１５１→補助リアクトル１５２→補助コンデンサ１５３→半導体スイッチ素子２Ａの経路で補助リアクトル１５２および補助コンデンサ１５３に放電する。スナバコンデンサ１４１が０Ｖまで放電すると、補助リアクトル１５２に蓄えられたエネルギーにより、補助リアクトル１５２→補助コンデンサ１５３→スナバダイオード１４２→補助ダイオード１５１の経路で電流が流れ、補助コンデンサ１５３にエネルギーを移す。さらに、半導体スイッチ素子２Ａがオフの期間▲４▼に、補助コンデンサ１５３に蓄えられた電荷は、補助コンデンサ１５３→回生ダイオード１５４→第１のスナバ回路１３→回生ダイオード１７４→補助コンデンサ１７３→変圧器一次巻線４２→変圧器一次巻線４１の経路で第１のスナバ回路１３に放出する。そして、半導体スイッチ素子２Ａと２Ｂが同時にオンしている期間▲１▼から▲３▼に、第１のスナバ回路１３に蓄えられている電荷を、第１のスナバ回路１３→半導体スイッチ素子２Ｂ→変圧器一次巻線４２→直流電源１の経路で放電し、第１のスナバ回路１３で吸収したエネルギーを負荷に放出する。なお、以上のような動作は、半導体スイッチ素子２Ｂに付属するスナバコンデンサ１６１のエネルギー回生動作についても同様である。
図１７に図１６の変形例を示す。図１６との相違点は、直流電源１の正極端子を半導体スイッチ素子２Ａとダイオード３Ａとの並列接続点に、直流電源１の負極端子をスイッチ３０の一方の端子にそれぞれ接続した点にある。ただし、その動作は図１６と全く同様なので、説明は省略する。
【００４０】
図１８は、図１４で半導体スイッチのターンオフ時の電圧上昇率を抑制する回路例（この発明の第８の実施の形態）である。
図１４との相違点は、スナバダイオード１４２とスナバコンデンサ１４１を直列接続した第２のスナバ回路１４を半導体スイッチ素子２Ａと並列に、また、補助ダイオード１５１と補助リアクトル１５２を直列接続した直列回路と補助コンデンサ１５３とを直列接続した補助回路１５をスナバダイオード１４２と並列に、さらに、回生ダイオード１８２と回生リアクトル１８１とを直列接続した回生回路１８を上記直列回路と補助コンデンサ１５３との直列接続点と半導体スイッチ２Ｃと２Ｄとの並列接続点間に、半導体スイッチ２Ｂについては、スナバ回路１９，補助回路２０および回生回路２１を、半導体スイッチ２Ｃについては、スナバ回路２２，補助回路２３および回生回路２４を、また、半導体スイッチ２Ｄについては、スナバ回路２５，補助回路２６および回生回路２７を、上記と同様にそれぞれ接続した点にある。
【００４１】
図２３に図１８のスイッチ３０を端子３０Ａ側に接続した場合の動作波形を示す。その直流出力動作については図１４と同様なので、ここでは半導体スイッチ素子２Ａに付属するスナバコンデンサ１４１のエネルギー回生動作について説明する。
半導体スイッチ素子２Ａがターンオフしたとき、スナバコンデンサ１４１が半導体スイッチ素子２Ａの電圧上昇率を抑制する。次に、半導体スイッチ素子２Ａがオンしている期間▲１▼，▲２▼にスナバコンデンサ１４１に蓄えられている電荷を、スナバコンデンサ１４１→補助ダイオード１５１→補助リアクトル１５２→補助コンデンサ１５３→半導体スイッチ素子２Ａの経路で補助リアクトル１５２および補助コンデンサ１５３に放電する。スナバコンデンサ１４１が０Ｖまで放電すると、補助リアクトル１５２に蓄えられたエネルギーにより、補助リアクトル１５２→補助コンデンサ１５３→スナバダイオード１４２→補助ダイオード１５１の経路で電流が流れ、補助コンデンサ１５３にエネルギーを移す。さらに、半導体スイッチ素子２Ｂと２Ｃがオンしている期間▲５▼から▲７▼に、補助コンデンサ１５３に蓄えられた電荷は、補助コンデンサ１５３→回生リアクトル１８１→回生ダイオード１８２→半導体スイッチ素子２Ｃの経路で回生リアクトル１８１に放出する。そして、半導体スイッチ素子２Ｃがオフしている期間▲８▼に、回生リアクトル１８１に蓄えられているエネルギーは、回生リアクトル１８１→回生ダイオード１８２→第１のスナバ回路１３→回生ダイオード２７２→回生リアクトル２７１→補助コンデンサ２６３→変圧器一次巻線４２→変圧器一次巻線４１→補助コンデンサ１５３の経路で電流を流し、第１のスナバ回路１３にエネルギーを放出する。最後に、半導体スイッチ素子２Ａと２Ｄが同時にオンしている期間▲１▼から▲３▼に、第１のスナバ回路１３に蓄えられている電荷を、第１のスナバ回路１３→半導体スイッチ素子２Ｄ→変圧器一次巻線４２→直流電源１の経路で放電し、第１のスナバ回路１３で吸収したエネルギーを負荷に放出する。なお、以上のような動作は、半導体スイッチ素子２Ｂに付属するスナバコンデンサ１９１、半導体スイッチ素子２Ｃに付属するスナバコンデンサ２２１、および半導体スイッチ素子２Ｄに付属するスナバコンデンサ２５１の各エネルギー回生動作についても同様である。
図１９に図１８の変形例を示す。図１８との相違点は、直流電源１の正極側端子を半導体スイッチ素子２Ａと半導体スイッチ素子２Ｂとの並列接続点に、直流電源１の負極側端子をスイッチ３０の一方の端子にそれぞれ接続した点にある。ただし、その動作は図１８と全く同様なので、説明は省略する。
【００４２】
【発明の効果】
請求項１〜３の発明によれば、スナバ回路に蓄えられたエネルギーを直流電源に回生するかまたは負荷に放出するようにしたので、スナバ回路では損失が殆ど発生しないようになる。また、請求項４〜６の発明によれば、半導体スイッチ素子のターンオフ時の電圧上昇率を低減できるので、スイッチング損失および発熱が低減するという利点が得られる。その結果、装置の変換効率が向上し、放熱のための冷却装置を小形にできるという利点がもたらされる。
また、請求項７，８の発明によれば、直流電源の電圧が一定値以下の場合は１石フォワードコンバータまたはプッシュプル型コンバータとして動作し、変圧器の巻線比が（ｎ１１＋ｎ１２）：ｎ２からｎ１１：ｎ２に変わるため、直流電源電圧が低い場合でも半導体スイッチ素子がオンしている期間の変化があまりないことにより、導通損失が低減する。また、直流電源電圧が一定値以上の場合、変圧器二次巻線に発生する電圧は、Ｅｄ×ｎ２／（ｎ１１＋ｎ１２）となるため、整流回路を構成するダイオードは、従来のものに比べて耐圧の低いものを選定することができ、安価となる。
さらに、請求項９，１０の発明のように、請求項７，８の発明に対してスナバ回路，補助回路および回生回路を付加することにより、スナバ回路では損失が殆ど発生しなくなるだけでなく、半導体スイッチ素子のターンオフ時に発生するスイッチング損失および発熱が低減するという利点も得られる。その結果、装置の変換効率が向上し、放熱のための冷却装置を小形化することができる。
【図面の簡単な説明】
【図１】この発明による第１の実施の形態を示す回路図である。
【図２】図１の変形例を示す回路図である。
【図３】図１，図２の動作説明図である。
【図４】この発明による第２の実施の形態を示す回路図である。
【図５】図４の変形例を示す回路図である。
【図６】図４，図５の動作説明図である。
【図７】この発明による第３の実施の形態を示す回路図である。
【図８】この発明による第４の実施の形態を示す回路図である。
【図９】図８の変形例を示す回路図である。
【図１０】図７の動作説明図である。
【図１１】図８，図９の動作説明図である。
【図１２】この発明による第５の実施の形態を示す回路図である。
【図１３】図１２の変形例を示す回路図である。
【図１４】この発明による第６の実施の形態を示す回路図である。
【図１５】図１４の変形例を示す回路図である。
【図１６】この発明による第７の実施の形態を示す回路図である。
【図１７】図１６の変形例を示す回路図である。
【図１８】この発明による第８の実施の形態を示す回路図である。
【図１９】図１８の変形例を示す回路図である。
【図２０】図１２，１３の動作説明図である。
【図２１】図１４，１５の動作説明図である。
【図２２】図１６，１７の動作説明図である。
【図２３】図１８，１９の動作説明図である。
【図２４】第１の従来例を示す回路図である。
【図２５】図２４の動作説明図である。
【図２６】第２の従来例を示す回路図である。
【図２７】第３の従来例を示す回路図である。
【図２８】図２６の動作説明図である。
【図２９】図２７の動作説明図である。
【符号の説明】
１…直流電源、２Ａ，２Ｂ，２Ｃ，２Ｄ…半導体スイッチ素子、３Ａ，３Ｂ…ダイオード、４…変圧器、５…整流回路、６…平滑回路（平滑フィルタ）、７，１０，１３，１４，１６，１９，２２，２５…スナバ回路、８，１１，１５，１７，２０，２３，２６…補助回路、９，１２，１５４，１７４，１８２，２１２，２４２，２７２…回生ダイオード、１８，２１，２４，２７…回生回路、３０…スイッチ、３０Ａ，３０Ｂ…スイッチ３０の端子、３１Ａ，３２Ａ…コンデンサ、４０…入力電圧検出回路、４１…変圧器一次巻線、４２…変圧器リセット巻線、４３…変圧器二次巻線、５０…制御回路、７１，１０１，１４２，１６２，１９２，２２２，２５２…スナバダイオード、７２，１０２，１４１，１６１，１９１，２２１，２５１…スナバコンデンサ、７３…放電抵抗、８１，１１１，１５１，１７１，２０１，２３１，２６１…補助ダイオード、８２，１１２，１５２，１７２，２０２，２３２，２６２…補助リアクトル、１１３，１５３，１７３，２０３，２３３，２６３…補助コンデンサ、１８１，２１１，２４１，２７１…回生リアクトル。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a DC-DC converter that extracts insulated DC power from a DC power supply.
[0002]
[Prior art]
FIG. 24 shows a conventional example of a one-stone forward type DC-DC converter.
As shown in the figure, the positive terminal of the DC power supply 1 has a connection point between the primary winding 41 and the reset winding 42 of the transformer 4, and the other terminal of the primary winding 41 of the transformer 4 and the DC power supply. 1 is connected between the negative terminal of the transformer 1 and the diode 3 A is connected between the other terminal of the reset winding 42 of the transformer 4 and the negative terminal of the DC power source 1. The rectifier circuit 5 is connected to the rectifier circuit 5, and the smoothing filter (smoothing circuit) 6 is connected to the rectifier circuit 5.
[0003]
FIG. 25 shows the operation waveform of FIG. 24 (the circuit and the operation as shown in FIG. 24 are, for example, published by Seikodo Shinko Co., Ltd. in 1984 “Switching Regulator Design Method and Power Device Usage”, pages 18-19. It is well known from the description on pages 95 to 99).
Now, during the period {circle around (1)} when the semiconductor switch element 2A is ON, the transformer 4 is excited in the positive direction, and DC power is supplied to the load via the rectifier circuit 5 and the smoothing filter 6. On the other hand, the excitation energy of the transformer 4 is regenerated to the DC power source 1 through the reset winding 42 and the diode 3A during the period (2) when the semiconductor switch element 2A is OFF.
[0004]
In the circuit of FIG. 24, when the semiconductor switch element 2A is turned off, the jumper voltage of the semiconductor switch element 2A is suppressed and the voltage increase rate (dv / dt) is reduced to reduce the switching loss. On the other hand, a diode 71 and a capacitor 72 are connected in series, and a snubber circuit 7 in which a discharge resistor 73 is connected in parallel to the diode 71 is connected in parallel. Thereby, the energy absorbed by the capacitor 72 is released to the discharge resistor 73 in the next period when the semiconductor switch element 2A is turned on.
[0005]
[Problems to be solved by the invention]
In the circuit of FIG. 24, the energy absorbed by the snubber capacitor is released to the discharge resistor and becomes a loss when the semiconductor switch element is turned on next time. Now, P is the loss of the discharge resistance, C is the capacitance of the snubber capacitor, E is the voltage of the DC power supply, Vr is the reset voltage of the transformer, ΔV is the rising voltage of the semiconductor switch element, and f is the operating frequency of the semiconductor switch element. Then,
P = (1/2) × C × (E + Vr + ΔV) 2 × f
It becomes. Accordingly, when the voltage E of the DC power source, the reset voltage Vr of the transformer, and the operating frequency f of the semiconductor switch element are increased, the generated loss in the discharge resistor is increased, so that not only a large and expensive snubber circuit is required. There is a problem that the conversion efficiency of the apparatus is lowered.
Accordingly, an object of the present invention is not to increase the size of the snubber circuit and to prevent the conversion efficiency of the apparatus from being lowered.
[0006]
[Means for Solving the Problems]
In order to solve such a problem, the invention of claim 1 includes a DC power supply, a transformer having a reset winding on the primary side, a rectifier circuit connected to the secondary side of the transformer, and a rectified output thereof. In a DC-DC converter comprising a smoothing circuit for smoothing and taking out DC power insulated from a DC power supply, one terminal of the first diode and one terminal of the first semiconductor switch element are connected in series. A first series arm, a second series arm in which one terminal of a second semiconductor switch element and one terminal of a second diode are connected in series, and a first snubber circuit are connected in parallel. In addition, the terminal of the transformer primary winding not connected to the reset winding is connected to the connection point of the first series arm, and the transformer winding primary winding is not connected to the primary winding. The terminal of the second Further, the DC power source is connected in parallel between the connection point of the transformer primary winding and the reset winding, and the connection point of the first semiconductor switch element and the second diode. , Connect each.
[0007]
According to the first aspect of the present invention, when the first semiconductor switch element is turned off, the capacitor constituting the first snubber circuit is clamped at (E + Vr), and therefore the energy P1 absorbed by the first snubber circuit. Is
P1 = (1/2) × C × ΔV 2 × f
And it gets smaller. Further, by turning on the second switch element while the first semiconductor switch element is on, the energy P1 absorbed by the first snubber circuit can be released to the load.
[0008]
According to a second aspect of the invention, in contrast to the first aspect of the invention, a second snubber circuit in which a snubber diode and a snubber capacitor are connected in series is provided in parallel with the first semiconductor switch element, and an auxiliary diode, an auxiliary reactor, An auxiliary circuit in which an auxiliary capacitor is connected in series to the series circuit is parallel to the snubber diode, and a regenerative diode is connected to a connection point between the series circuit and the auxiliary capacitor, and a parallel connection point of the second semiconductor switch element. Connected to each other.
[0009]
According to the second aspect of the present invention, when the first semiconductor switch element is turned off, the voltage increase rate of the first semiconductor switch element is suppressed by the snubber capacitor, and the switching loss is reduced. Next, while the first semiconductor switch element is on, the charge stored in the snubber capacitor is absorbed by the auxiliary circuit and transferred to the auxiliary capacitor. Further, the charge stored in the auxiliary capacitor is transferred to the first snubber circuit via the regenerative diode during the period in which the first semiconductor switch element is off. Then, during the period when the first semiconductor switch element is on, the energy absorbed by the first snubber circuit is released to the load by turning on the second semiconductor switch element.
[0010]
According to a third aspect of the present invention, in the first or second aspect of the invention, the ON period of the second semiconductor switch element is a resonance determined by the capacitance of the capacitor constituting the first snubber circuit and the leakage inductance of the transformer. The frequency is approximately ½. As a result, a sine wave current having a cycle determined by the capacitance of the capacitor constituting the first snubber circuit and the leakage inductance of the transformer flows through the second semiconductor switch element. The switching loss is reduced by cutting the current around 0 A at the time of turn-off.
[0011]
In a fourth aspect of the invention, a first series arm in which a first diode and a first semiconductor switch element are connected in series, and a second series in which a second semiconductor switch element and a second diode are connected in series. An arm and a DC power source are connected in parallel to each other, and a transformer primary winding is connected between a series connection point of the first series arm and a series connection point of the second series arm; In the DC-DC converter, the rectifier circuit is connected to the secondary winding of the transformer, and the smoothing circuit is connected to the rectifier circuit.
A snubber circuit in which a snubber diode and a snubber capacitor are connected in series is connected in parallel to each of the first semiconductor switch element and the second semiconductor switch element, and each of the snubber diodes includes an auxiliary diode, an auxiliary reactor, and An auxiliary circuit in which an auxiliary capacitor is connected in series to a series circuit in which an auxiliary capacitor is connected in series; a regenerative diode; a connection point between the series circuit and the auxiliary capacitor; and a parallel connection point between the first and second series arms. Connected to each other.
[0012]
In the invention of claim 5, a first series arm in which two sets of switching elements in which a semiconductor switch element and a diode are connected in antiparallel are connected in series, a second series arm in which capacitors are connected in series, and a DC power source are provided. The transformer primary winding is connected between the series connection point of the first series arm and the series connection point of the second series arm, and is connected to the secondary winding of the transformer. Is a rectifier circuit, and a DC-DC converter comprising a smoothing circuit connected to the rectifier circuit,
Each of the switching elements has a snubber circuit in which a snubber diode and a snubber capacitor are connected in series, and each of the snubber diodes has an auxiliary capacitor in a series circuit in which an auxiliary diode and an auxiliary reactor are connected in series. An auxiliary circuit connected in series is connected in parallel, and a regenerative diode is connected between a connection point between the series circuit and the auxiliary capacitor and a parallel connection point between the first and second series arms.
[0013]
In the invention of claim 6, a first series arm in which two sets of switching elements in which a semiconductor switch element and a diode are connected in antiparallel are connected in series, a second series arm in which capacitors are connected in series, and a direct current power source. The transformer primary winding is connected between the series connection point of the first series arm and the series connection point of the second series arm, and is connected to the secondary winding of the transformer. Is a rectifier circuit, and a DC-DC converter comprising a smoothing circuit connected to the rectifier circuit,
An auxiliary reactor is connected in series between the switching element and the connection point of the transformer primary winding, and a snubber circuit in which a snubber diode and a snubber capacitor are connected in series is connected in parallel to each of the switching elements. And an auxiliary circuit connected in series between a series connection point of the snubber circuit and a connection point between the auxiliary reactor and the connection point of the transformer primary winding, and a regenerative diode connected to the series connection point of the auxiliary circuit. Each of the first and second series arms is connected between parallel connection points.
[0014]
In the inventions of the fourth to sixth aspects, when the semiconductor switch element is turned off, the voltage increase rate of the semiconductor switch element is suppressed by the snubber capacitor, and the switching loss is reduced. Next, during the period when the semiconductor switch element is on, the charge stored in the snubber capacitor is absorbed by the auxiliary circuit and transferred to the auxiliary capacitor. Thereafter, during the period when the semiconductor switch element is off, the charge stored in the auxiliary capacitor is regenerated to the DC power supply via the regenerative diode, thereby reducing the loss generated in the snubber circuit.
[0015]
In the invention of claim 7, the first series arm in which one terminal of the first diode and one terminal of the first semiconductor switch element are connected in series, the one terminal of the second semiconductor switch element and the first terminal A second series arm connected in series with one terminal of the two diodes and a first snubber circuit in parallel, and one terminal of a transformer primary winding having an intermediate terminal connected to the first terminal. The other terminal of the transformer primary winding is connected to the series connection point of the first series arm, and the DC power supply is connected to the first terminal of the three-terminal switch. Between a parallel connection point of the first semiconductor switch element and the second diode, the second terminal of the three-terminal switch is an intermediate terminal of the transformer, and the third terminal of the three-terminal switch is the A first diode and said 2 is connected between the parallel connection points of the two semiconductor switch elements, the input voltage detection circuit is connected in parallel with the DC power supply, and the control circuit is connected between the input voltage detection circuit and the three-terminal switch. The secondary terminal of the transformer is connected to the rectifier circuit, and this rectifier circuit is connected to the smoothing filter.
[0016]
In the invention of claim 8, a first series arm in which one terminal of the first semiconductor switch element and one terminal of the second semiconductor switch element are connected in series, and one terminal of the third semiconductor switch element And a second series arm in which the first terminal of the fourth semiconductor switch element is connected in series and the first snubber circuit are respectively connected in parallel, and one of the transformer primary windings having an intermediate terminal is connected. The terminal is connected to the series connection point of the first series arm, the other terminal of the transformer primary winding is connected to the series connection point of the second series arm, and the DC power supply is connected to the third connection point of the three-terminal switch. A second terminal of the three-terminal switch as an intermediate terminal of the transformer, and a parallel connection point of the first terminal, the first semiconductor switch element, and the third semiconductor switch element; Before the third terminal The second semiconductor switch element and the fourth semiconductor switch element are respectively connected between parallel connection points, and further, an input voltage detection circuit is connected in parallel with the DC power supply, and a control circuit is connected to the input voltage detection circuit and the input voltage detection circuit. Between the three-terminal switch, the secondary terminal of the transformer is connected to a rectifier circuit, and this rectifier circuit is connected to a smoothing filter.
[0017]
According to the seventh aspect of the present invention, a second snubber circuit in which a first snubber diode and a first snubber capacitor are connected in series is provided in parallel with the first semiconductor switch element, and a first auxiliary diode and a first snubber circuit are connected. A first series circuit in which a first auxiliary circuit is connected in series and a first auxiliary circuit in which a first auxiliary capacitor is connected in series are connected in parallel with the first snubber diode, and a first regenerative diode is connected in the first A second snubber diode and a second snubber capacitor are connected in series between a connection point between the series circuit and the first auxiliary capacitor and a parallel connection point between the first diode and the second semiconductor switch element. A second series circuit and a second auxiliary capacitor, in which a third snubber circuit is connected in parallel with the second semiconductor switch element, and a second auxiliary diode and a second auxiliary reactor are connected in series. Is connected in series with the second snubber diode, and a second regenerative diode is connected to the connection point between the second series circuit and the second auxiliary capacitor, the second diode, and the second diode. Connections can be made between the parallel connection points with the first semiconductor switch element (invention of claim 9).
[0018]
In the invention of claim 8, a second snubber circuit in which a first snubber diode and a first snubber capacitor are connected in series is provided in parallel with the first semiconductor switch element, and a first auxiliary diode and a first snubber circuit are connected. The first regenerative diode and the first regenerative diode are connected in parallel with the first snubber diode in a first series circuit in which a first auxiliary circuit in series is connected in series with a first auxiliary capacitor. A first regenerative circuit in which a reactor is connected in series is connected between a connection point between the first series circuit and the first auxiliary capacitor and a parallel connection point between the second semiconductor switch element and the fourth semiconductor switch element. In addition, a third snubber circuit in which a second snubber diode and a second snubber capacitor are connected in series is connected in parallel with the second semiconductor switch element, and a second auxiliary diode and a second auxiliary resistor are connected. A second regenerative diode, a second regenerative reactor, and a second regenerative diode in parallel with the second snubber diode. A second regenerative circuit connected in series between the connection point of the second series circuit and the second auxiliary capacitor and the parallel connection point of the first semiconductor switch element and the third semiconductor switch element. As for the second series arm, the fourth snubber circuit, the fifth snubber circuit, the third auxiliary circuit, the fourth auxiliary circuit, the third regeneration circuit, and the fourth regeneration circuit are connected to each other as described above. (Invention of claim 10).
[0019]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a circuit diagram showing a first embodiment of the present invention.
The snubber circuit 7 is omitted from the conventional example shown in FIG. 24, one terminal of the diode 3B is used as a connection point between the transformer primary winding 41 and the semiconductor switch element 2A, and one terminal of the semiconductor switch element 2B is used as a transformer reset winding. At the connection point between the line 42 and the diode 3A, the other terminal of the diode 3B is connected to the other terminal of the semiconductor switch element 2B, the snubber circuit 13 is connected to the parallel connection point of the diode 3B and the semiconductor switch element 2B, and the semiconductor switch element 2A. Each of the diodes 3A is connected to a parallel connection point.
FIG. 3 shows the operation waveforms of FIG. 1 is the same as that in FIG. 24, only the differences will be described below.
That is, when the semiconductor switch element 2A is turned off, the snubber circuit 13 absorbs the energy stored in the leakage inductance and wiring inductance of the transformer 4 via the diode 3B. Next, in the period {circle around (1)} when the semiconductor switch element 2A and the semiconductor switch element 2B are simultaneously turned on, the electric charge stored in the snubber circuit 13 is converted into the snubber circuit 13 → the semiconductor switch element 2B → the transformer reset winding 42. → The battery is discharged through the route of the DC power source 1 and the energy absorbed by the snubber circuit 13 is released to the load. That is, the diode 3B serves as a snubber diode, and the semiconductor switch element 2B acts for power regeneration.
FIG. 2 shows a modification of FIG.
This is because the positive terminal of the DC power source 1 is connected to the connection point between the semiconductor switch element 2A and the diode 3A, and the negative terminal of the DC power source 1 is connected to the transformer primary winding 41 and the transformer reset winding 42. The point is connected to each point, and the function is exactly the same as in FIG.
[0020]
FIG. 4 is a circuit diagram showing a second embodiment of the present invention, and FIG. 6 is a diagram for explaining the operation thereof.
1 differs from FIG. 1 in that a snubber circuit 7 in which a snubber diode 71 and a snubber capacitor 72 are connected in series is parallel to the semiconductor switch element 2A, and a series circuit in which an auxiliary diode 81 and an auxiliary reactor 82 are connected in series and an auxiliary capacitor 83. Is connected in parallel to the snubber diode 71, and the regenerative diode 9 is connected between the connection point of the series circuit and the auxiliary capacitor 83, and the connection point of the diode 3B and the semiconductor switch element 2B. It is in.
That is, in the example shown in FIGS. 1 and 2, since the energy absorbed by the snubber circuit 13 is released to the load, the snubber circuit 13 generates almost no loss, but the voltage when the semiconductor switch element 2A is turned off. The rate of increase cannot be suppressed. The one shown in FIG. 4 makes it possible to solve this problem.
[0021]
With reference to FIG. 6, the energy recovery operation of the charge of the snubber capacitor 72 connected in parallel to the semiconductor switch element 2 </ b> A will be described.
Now, when the semiconductor switch element 2A is turned off, the snubber capacitor 72 suppresses the voltage increase rate of the semiconductor switch element 2A. Next, during the periods {circle around (1)} and {circle around (2)} in which the semiconductor switch element 2A is on, the electric charge stored in the snubber capacitor 72 is converted into the snubber capacitor 72 → auxiliary diode 81 → auxiliary reactor 82 → auxiliary capacitor 83 → semiconductor switch The auxiliary reactor 82 and the auxiliary capacitor 83 are discharged through the path of the element 2A.
When the snubber capacitor 72 is discharged to 0 V, current flows through the path of the auxiliary reactor 82 → the auxiliary capacitor 83 → the snubber diode 71 → the auxiliary diode 81 due to the energy stored in the auxiliary reactor 82, and the energy is transferred to the auxiliary capacitor 83. Further, during the period (3) when the semiconductor switch element 2A is off, the charge stored in the auxiliary capacitor 83 is transferred along the path of the auxiliary capacitor 83 → the regenerative diode 9 → the snubber circuit 13 → the DC power source 1 → the transformer primary winding 41. Release into the snubber circuit 13.
Then, during the period {circle around (1)} when the semiconductor switch elements 2A and 2B are simultaneously turned on, the electric charge stored in the snubber circuit 13 is converted into the snubber circuit 13 → semiconductor switch element 2B → transformer reset winding 42 → DC power supply 1 To discharge the energy absorbed by the snubber circuit 13 to the load.
FIG. 5 shows a modification of FIG.
That is, the positive terminal of the DC power source 1 is connected to the connection point between the semiconductor switch 2A and the diode 3A, and the negative terminal of the DC power source 1 is connected to the connection point between the transformer primary winding 41 and the transformer reset winding 42. Other than this, it is exactly the same as that shown in FIG.
[0022]
As described above, in any example, during the ON period of the semiconductor switch element 2B, the semiconductor switch element 2B has a sinusoidal wave shape with a period determined by the capacitance of the capacitor constituting the snubber circuit 13 and the leakage inductance of the transformer 4. Current flows. Therefore, the ON period of the semiconductor switch element 2B is set to about 1/2 of the resonance period determined by the capacitance of the capacitor and the leakage inductance of the transformer (see period (1) shown in FIG. 6), and the semiconductor switch element 2B is turned off. The current is cut off at around 0A. Thereby, the switching loss at the time of turn-off of the semiconductor switch element 2B can be reduced.
[0023]
4 and 5 are each a one-stone forward converter with a snubber circuit, an auxiliary circuit and a regenerative diode added thereto, but application to a two-stone forward type or half-bridge type converter is also conceivable.
FIG. 7 shows an application to a two-stone forward type. In the basic circuit, a snubber circuit 7 in which a snubber diode 71 and a snubber capacitor 72 are connected in series is parallel to the semiconductor switch element 2A, and the auxiliary diode 81 is connected to the auxiliary circuit. The auxiliary circuit 8 in which the auxiliary capacitor 83 is connected in series to the first series circuit in which the reactor 82 is connected in series is connected in parallel to the snubber diode 71, and the regenerative diode 9 is connected to the first series circuit and the auxiliary capacitor 83. It connects between a point and the positive electrode side terminal of DC power supply 1, and is comprised. Similarly, the snubber circuit 10 in which the snubber diode 101 and the snubber capacitor 102 are connected in series is connected in parallel with the semiconductor switch element 2B, and the auxiliary capacitor 113 is added in the second series circuit in which the auxiliary diode 111 and the auxiliary reactor 112 are connected in series. The auxiliary circuit 11 connected in series is connected in parallel with the snubber diode 101, and the regenerative diode 12 is connected between the connection point of the second series circuit and the auxiliary capacitor 113 and the negative terminal of the DC power supply 1. Configured.
[0024]
FIG. 10 shows the operation waveform of FIG.
Here, the regeneration operation of the charge energy of the snubber capacitor 72 attached to the semiconductor switch element 2A will be described. When the semiconductor switch element 2A is turned off, the snubber capacitor 72 suppresses the voltage increase rate of the semiconductor switch element 2A. Next, in the period {circle around (1)} in which the semiconductor switch element 2A is ON, the electric charge stored in the snubber capacitor 72 is converted into the path of the snubber capacitor 72 → auxiliary diode 81 → auxiliary reactor 82 → auxiliary capacitor 83 → semiconductor switch element 2A. Thus, the auxiliary reactor 82 and the auxiliary capacitor 83 are discharged. When the snubber capacitor 72 is discharged to 0V, the period {circle over (2)} is reached. Due to the energy stored in the auxiliary reactor 82, a current flows through the path of the auxiliary reactor 82 → the auxiliary capacitor 83 → the snubber diode 71 → the auxiliary diode 81. Transfer energy to 83. Next, during the period (4) when the semiconductor switch element 2A is OFF, the charge stored in the auxiliary capacitor 83 is as follows: auxiliary capacitor 83 → regenerative diode 9 → DC power supply 1 → regenerative diode 12 → auxiliary capacitor 11 → transformer primary. It discharges along the path of the winding 41 and regenerates energy to the DC power source 1. The snubber circuit 10, the auxiliary circuit 11, and the regenerative diode 12 attached to the semiconductor switch element 2B operate in the same manner as described above.
[0025]
FIG. 8 shows an application to a half-bridge type. A snubber circuit 7 in which a snubber diode 71 and a snubber capacitor 72 are connected in series is parallel to the semiconductor switch element 2A, and an auxiliary diode 81 and an auxiliary circuit. A first series circuit in which a reactor 82 is connected in series, an auxiliary circuit 8 in which an auxiliary capacitor 83 is connected in series are connected in parallel with a snubber diode 71, and a regenerative diode 9 is connected between the first series circuit and the auxiliary capacitor 83. They are connected between the connection point and the positive terminal of the DC power source 1. Similarly, the snubber circuit 10 in which the snubber diode 101 and the snubber capacitor 102 are connected in series is connected in parallel with the semiconductor switch element 2B, and the auxiliary capacitor 113 is added in the second series circuit in which the auxiliary diode 111 and the auxiliary reactor 112 are connected in series. Is connected in parallel with the snubber diode 101, and the regenerative diode 12 is connected between the connection point of the second series circuit and the auxiliary capacitor 113 and the negative terminal of the DC power supply 1. Configured.
[0026]
FIG. 11 shows the operation waveforms of FIG.
Here, the regeneration operation of the charge energy of the snubber capacitor 72 attached to the semiconductor switch element 2A will be described. When the semiconductor switch element 2A is turned off, the snubber capacitor 72 suppresses the voltage increase rate of the semiconductor switch element 2A. Next, in the period {circle around (1)} in which the semiconductor switch element 2A is ON, the electric charge stored in the snubber capacitor 72 is converted into the path of the snubber capacitor 72 → auxiliary diode 81 → auxiliary reactor 82 → auxiliary capacitor 83 → semiconductor switch element 2A. Thus, the auxiliary reactor 82 and the auxiliary capacitor 83 are discharged. When the snubber capacitor 72 is discharged to 0V, the period {circle over (2)} is reached. Due to the energy stored in the auxiliary reactor 82, a current flows through the path of the auxiliary reactor 82 → the auxiliary capacitor 83 → the snubber diode 71 → the auxiliary diode 81. Transfer energy to 83. Next, during the period (4) when the semiconductor switch element 2A is OFF, the charge stored in the auxiliary capacitor 83 is the path of the auxiliary capacitor 83 → regenerative diode 9 → DC power supply 1 → capacitor 31A → transformer primary winding 41. To regenerate energy in the capacitor 31A. The electric charge stored in the capacitor 31A is discharged to the load via the transformer 4 during the period (5) to (7) when the semiconductor switch element 2B is on. The snubber circuit 10, the auxiliary circuit 11, and the regenerative diode 12 attached to the semiconductor switch element 2B operate in the same manner as described above.
[0027]
FIG. 9 shows a modification of FIG.
An auxiliary reactor 82 is connected between the semiconductor switch element 2A and the connection point of the transformer primary winding 41, and a snubber circuit 7 in which a snubber diode 71 and a snubber capacitor 72 are connected in series is provided in parallel with the semiconductor switch element 2A. A third series circuit in which the diode 81 and the auxiliary capacitor 83 are connected in series is connected between the connection point of the snubber diode 71 and the snubber capacitor 72, and the connection point of the auxiliary reactor 82 and the transformer primary winding 41. A regenerative diode 9 is connected between the connection point of the third series circuit and the positive terminal of the DC power supply 1. Similarly, the auxiliary reactor 112 is connected between the connection point of the semiconductor switch element 2B and the transformer primary winding 41, and the snubber circuit 10 in which the snubber diode 101 and the snubber capacitor 102 are connected in series with the semiconductor switch element 2B. Further, a fourth series circuit in which the auxiliary diode 111 and the auxiliary capacitor 113 are connected in series is formed between the connection point of the snubber diode 101 and the snubber capacitor 102 and the connection point of the auxiliary reactor 112 and the transformer primary winding 41. Further, the regenerative diode 12 is connected between the connection point of the fourth series circuit and the negative terminal of the DC power supply 1.
In this example shown in FIG. 8, for example, when the semiconductor switch element 2B is turned on in a state in which the electric charge is not sufficiently stored in the snubber capacitor 72 when no load is applied, the semiconductor switch element 2B is charged to charge the snubber capacitor 72. An excessive current flows in In this example, such inconvenience is not caused.
[0028]
In the above, since the DC power supply voltage is handled as being almost constant, there remains a problem that it cannot be applied to one having a different voltage. This point will be described below. FIG. 26 shows a conventional example of a conventional two-stone forward type DC-DC converter.
That is, one terminal of the semiconductor switch 2B and one terminal of the diode 3B are connected to the positive terminal of the DC power supply 1, and one terminal of the semiconductor switch 2A and one of the diode 3A are connected to the negative terminal of the DC power supply 1. The other terminal of the semiconductor switch 2B is one terminal of the primary winding 41 of the transformer 4 and the other terminal of the diode 3A, and the other terminal of the diode 3B is the other terminal of the semiconductor switch 2A. The other terminal of the primary winding 41 of the transformer 4 is connected to the secondary winding 43 of the transformer 4, and the smoothing filter 6 is connected to the rectifying circuit 5.
The operation waveforms of FIG. 26 are shown in FIG.
During the period {circle around (1)} when the semiconductor switches 2A and 2B are turned on, the transformer 4 is excited in the positive direction, and power is supplied to the load via the rectifier circuit 5 and the smoothing filter 6. Next, during the period (2) in which the semiconductor switches 2A and 2B are turned off, the excitation energy of the transformer 4 is regenerated to the DC power source 1 via the transformer primary winding 41 and the diodes 3A and 3B.
[0029]
FIG. 27 shows a conventional example of a full bridge type DC-DC converter.
In the figure, one terminal of the semiconductor switches 2C and 2D is connected to the positive terminal of the DC power source 1, one terminal of the semiconductor switches 2A and 2B is connected to the negative terminal of the DC power source 1, and the other terminal of the semiconductor switch 2D. The terminal includes one terminal of the primary winding 41 of the transformer 4 and the other terminal of the semiconductor switch 2B, and the other terminal of the semiconductor switch 2C includes the other terminal of the semiconductor switch 2A and the primary winding 41 of the transformer 4. The rectifier circuit 5 is connected to the secondary winding 43 of the transformer 4, and the smoothing filter 6 is connected to the rectifier circuit 5.
The operation waveform of FIG. 27 is shown in FIG.
During the period {circle around (1)} when the semiconductor switches 2A and 2D are on, the transformer 4 is excited in the positive direction, and DC power is supplied to the load via the rectifier circuit 5 and the smoothing filter 6. Next, in the period {circle around (3)} when the semiconductor switches 2B and 2C are turned on, the transformer 4 is excited in the negative direction, and DC power is supplied to the load via the rectifier circuit 5 and the smoothing filter 6.
[0030]
In the case of FIG. 26, the maximum voltage of the DC power source 1 is Ed1, the minimum voltage is Ed2, the semiconductor switches 2A and 2B when the voltage is Ed1, the period when the semiconductor switches 2A and 2B are on, and the semiconductor switches 2A and 2B when the voltage is Ed2 Is generated during the period when the semiconductor switches 2A and 2B are ON, where TS2 is the current period flowing through the semiconductor switches 2A and 2B, and i is the voltage drop of the semiconductor switches 2A and 2B. The conduction loss PON is
PON = 2 × (VS × i × TON)
It becomes. When the output voltage is constant, TS1 <TS2, and when the DC power supply voltage is Ed2, the conduction loss in the semiconductor switch increases.
Further, when the transformer turns ratio is n1: n2, and the voltage generated in the secondary winding 43 of the transformer is VT2,
VT2 = Ed × n2 / n1
It becomes. The diode constituting the rectifier circuit is selected so as not to exceed the withstand voltage even when the DC power supply voltage is Ed1, but the diode with a high withstand voltage has a problem that the generated loss is large and expensive.
[0031]
An example in which a DC power source is obtained by full-wave rectification from a single-phase alternating current (AC) power source 100V or 200V using a diode rectifier will be specifically described.
In the case of AC100V, Ed2 = 90V, and in the case of AC200V, Ed1 = 180V. At this time, TS2≈2 × TS1, and the conduction loss of the semiconductor switch in the case of AC100V is about twice that in the case of AC200V. If the transformer turns ratio is 1: 1, the diode constituting the rectifier is selected to have a withstand voltage of 180V or higher.
This also applies to the case of FIG. 27. When the DC power supply voltage is low, the conduction loss of the semiconductor switches 2A, 2B, 2C and 2D increases as compared with the case where the DC power supply voltage is high, and the diode constituting the rectifier circuit Must be selected so that it does not exceed the withstand voltage even when the DC power supply voltage is maximum.
That is, in the conventional DC-DC converter, the generated loss increases due to the fluctuation of the DC power supply voltage, and there remains a problem that a diode that constitutes the rectifier circuit requires a high breakdown voltage and an expensive one.
[0032]
A voltage-adaptive DC-DC converter capable of avoiding the above problems will be described below. FIG. 12 is a circuit diagram showing this embodiment (fifth embodiment).
The difference from FIG. 26 is that one terminal of the primary winding 41 of the transformer 4 is connected to the series connection point of the diode 3B and the semiconductor switch 2A, and one terminal of the primary winding 42 of the transformer 4 is the semiconductor switch 2B. And the diode 3A, the snubber circuit 13 is connected between the parallel connection point of the diode 3B and the semiconductor switch 2B, and the parallel connection point of the semiconductor switch 2A and the diode 3A, and the positive terminal of the DC power supply 1 is switched to the switch 30. The negative terminal of the DC power source 1 is connected to the parallel connection point of the semiconductor switch 2A and the diode 3A, the first terminal 30A of the switch 30 is used as the intermediate terminal of the transformer 4, and the second terminal of the switch 30 is used. The terminal 30B is connected to the parallel connection point of the diode 3B and the semiconductor switch 2B, the input voltage detection circuit 40 is connected to the DC power supply 1, and the control circuit 50 is switched to the input voltage detection circuit 40. Between 30 lies in constituted by connecting, respectively.
[0033]
In the configuration of FIG. 12, the voltage of the DC power supply 1 is detected by the input voltage detection circuit 40, and when the detected value becomes equal to or greater than a predetermined value, the control circuit 50 connects the switch 30 to the terminal 30B side. In this case, the two-stone converter configuration is the same as in FIG. 26, and the same operation as in FIG. 26 is performed. On the other hand, when the detected value is equal to or less than the predetermined value, the switch 30 is connected to the terminal 30A side and has a one-stone converter configuration similar to that shown in FIG.
FIG. 20 shows an operation waveform when the switch 30 is connected to the 30A side in FIG.
That is, the DC output operation of this circuit excites the transformer 4 in the positive direction during the period {circle around (1)} when the semiconductor switch 2A is ON, and supplies DC power to the load via the rectifier circuit 5 and the smoothing circuit 6. . Next, the excitation energy of the transformer 4 is regenerated to the DC power source 1 via the transformer primary winding 42 and the diode 3A during the period (2) when the semiconductor switch 2A is turned off. Note that the winding 42 acts as a reset winding in the case of a single stone converter, and acts as a primary winding in the case of a two stone converter.
[0034]
Here, the energy regeneration operation by the first snubber circuit 13 will be described.
When the semiconductor switch 2A is turned off, the first snubber circuit 13 absorbs the energy stored in the leakage inductance and wiring inductance of the transformer 4 via the diode 3B. Next, in the period {circle around (1)} when the semiconductor switches 2A and 2B are simultaneously turned on, the electric charge stored in the first snubber circuit 13 is changed to the first snubber circuit 13 → semiconductor switch 2B → transformer primary winding. 42 → DC is discharged through the path of the DC power source 1 and the energy absorbed by the first snubber circuit 13 is discharged to the secondary side of the transformer 4.
FIG. 13 shows a modification of FIG. The difference from FIG. 12 is that the positive terminal of the DC power supply 1 is connected to the parallel connection point of the semiconductor switch 2A and the diode 3A, and the negative terminal of the DC power supply 1 is connected to one terminal of the switch 30. However, the operation is exactly the same as in FIG.
[0035]
FIG. 14 shows a second embodiment (sixth embodiment) of a voltage-adaptive DC-DC converter.
This corresponds to the conventional example of FIG. 27, and the difference is that one terminal of the primary winding 41 of the transformer 4 is connected to the series connection point of the semiconductor switch 2A and the semiconductor switch 2C. One terminal of the primary winding 42 is connected to the series connection point of the semiconductor switch 2B and the semiconductor switch 2D, and the snubber circuit 13 is connected to the parallel connection point of the semiconductor switch 2C and the semiconductor switch 2D and the parallel connection of the semiconductor switch 2A and the semiconductor switch 2B. Between the connection points, the positive terminal of the DC power source 1 is one terminal of the switch 30, the negative terminal of the DC power source 1 is the parallel connection point of the semiconductor switch 2A and the semiconductor switch 2B, and the first terminal of the switch 30 is connected. 30A is the intermediate terminal of the transformer 4, the second terminal 30B of the switch 30 is the parallel connection point of the semiconductor switch 2C and the semiconductor switch 2D, and the input voltage detection circuit 40 is DC. Parallel to the source 1, between the input voltage detection circuit 40 and a switch 30 the control circuit 50 resides in that constituted by connecting, respectively.
[0036]
In the circuit of FIG. 14 as well, the voltage of the DC power source 1 is detected by the input voltage detection circuit 40, and when the detected value becomes a predetermined value or more, the control circuit 50 connects the switch 30 to the terminal 30B side. In this case, the full bridge configuration is the same as in FIG. 27, and the same operation as in FIG. 27 is performed. On the other hand, when the detected value is equal to or less than the predetermined value, the switch 30 is connected to the terminal 30A side and has a push-pull configuration.
FIG. 21 shows operation waveforms when the switch 30 is connected to the 30A side in FIG.
That is, the DC output operation of this circuit excites the transformer 4 in the positive direction during the period {circle around (1)} when the semiconductor switch 2A is ON, and supplies DC power to the load via the rectifier circuit 5 and the smoothing circuit 6. . Next, during the period {circle around (3)} in which the semiconductor switch 2B is ON, the transformer 4 is excited in the negative direction, and DC power is supplied to the load via the rectifier circuit 5 and the smoothing circuit 6.
[0037]
Here, the energy regeneration operation by the first snubber circuit 13 will be described.
When the semiconductor switch 2A is turned off, the first snubber circuit 13 absorbs the energy stored in the leakage inductance and the wiring inductance of the transformer 4 through the diode connected in antiparallel with the semiconductor switch 2C. Next, in the period {circle around (1)} in which the semiconductor switches 2A and 2D are simultaneously turned on, the charge stored in the first snubber circuit 13 is changed to the first snubber circuit 13 → semiconductor switch 2D → transformer primary winding. 42 → DC is discharged through the path of the DC power source 1 and the energy absorbed by the first snubber circuit 13 is released to the secondary side of the transformer 4. The same operation as described above is performed when the semiconductor switch 2B is turned off and during the period when the semiconductor switches 2B and 2C are simultaneously turned on.
FIG. 15 shows a modification of FIG. The difference from FIG. 14 is that the positive terminal of the DC power source 1 is connected to the parallel connection point of the semiconductor switches 2A and 2B, and the negative terminal of the DC power source 1 is connected to one terminal of the switch 30. However, the operation is exactly the same as in FIG.
[0038]
FIG. 16 is a circuit example (seventh embodiment) that can suppress the voltage increase rate when the semiconductor switch shown in FIG. 12 is turned off.
The difference from FIG. 12 is that a second snubber circuit 14 in which a snubber diode 142 and a snubber capacitor 141 are connected in series is parallel to the semiconductor switch element 2A, and a series circuit in which an auxiliary diode 151 and an auxiliary reactor 152 are connected in series. The auxiliary circuit 15 in which the auxiliary capacitor 153 is connected in series is connected in parallel with the snubber diode 142, and the regenerative diode 154 is connected between the connection point of the series circuit and the auxiliary capacitor 153, and the parallel connection point of the diode 3B and the semiconductor switch element 2B. In addition, the third snubber circuit 16, the auxiliary circuit 17, and the regenerative diode 174 are also connected to the semiconductor switch element 2B.
[0039]
FIG. 22 shows operation waveforms when the switch 30 of FIG. 16 is connected to the terminal 30A side. Since the DC output operation is the same as that in FIG. 12, the energy regeneration operation of the snubber capacitor 141 attached to the semiconductor switch element 2A will be described here.
When the semiconductor switch element 2A is turned off, the snubber capacitor 141 suppresses the voltage increase rate of the semiconductor switch element 2A. Next, the charge stored in the snubber capacitor 141 during the period {circle around (1)} to {circle around (3)} in which the semiconductor switch element 2A is on is converted into the snubber capacitor 141 → auxiliary diode 151 → auxiliary reactor 152 → auxiliary capacitor 153 → semiconductor switch. The auxiliary reactor 152 and the auxiliary capacitor 153 are discharged through the path of the element 2A. When the snubber capacitor 141 is discharged to 0 V, current flows through the path of the auxiliary reactor 152 → the auxiliary capacitor 153 → the snubber diode 142 → the auxiliary diode 151 by the energy stored in the auxiliary reactor 152, and the energy is transferred to the auxiliary capacitor 153. Further, during the period (4) when the semiconductor switch element 2A is OFF, the charge stored in the auxiliary capacitor 153 is as follows: auxiliary capacitor 153 → regenerative diode 154 → first snubber circuit 13 → regenerative diode 174 → auxiliary capacitor 173 → transformer The first winding 42 is discharged to the first snubber circuit 13 through the path of the transformer primary winding 41. Then, during the period {circle around (1)} to {circle around (3)} in which the semiconductor switch elements 2A and 2B are simultaneously turned on, the electric charge stored in the first snubber circuit 13 is changed to the first snubber circuit 13 → the semiconductor switch element 2B → It discharges in the path | route of the transformer primary winding 42-> DC power supply 1, and discharge | releases the energy absorbed in the 1st snubber circuit 13 to load. The above operation is the same as the energy regeneration operation of the snubber capacitor 161 attached to the semiconductor switch element 2B.
FIG. 17 shows a modification of FIG. The difference from FIG. 16 is that the positive terminal of the DC power supply 1 is connected to the parallel connection point of the semiconductor switch element 2A and the diode 3A, and the negative terminal of the DC power supply 1 is connected to one terminal of the switch 30. However, the operation is exactly the same as in FIG.
[0040]
FIG. 18 is a circuit example (eighth embodiment of the present invention) for suppressing the voltage increase rate when the semiconductor switch is turned off in FIG.
The difference from FIG. 14 is that a second snubber circuit 14 in which a snubber diode 142 and a snubber capacitor 141 are connected in series is parallel to the semiconductor switch element 2A, and a series circuit in which an auxiliary diode 151 and an auxiliary reactor 152 are connected in series. The auxiliary circuit 15 in which the auxiliary capacitor 153 is connected in series is connected in parallel with the snubber diode 142, and the regenerative circuit 18 in which the regenerative diode 182 and the regenerative reactor 181 are connected in series is connected to the series connection point of the series circuit and the auxiliary capacitor 153. Between the parallel connection points of the semiconductor switches 2C and 2D, the snubber circuit 19, the auxiliary circuit 20 and the regenerative circuit 21 are provided for the semiconductor switch 2B, and the snubber circuit 22, the auxiliary circuit 23 and the regenerative circuit 24 are provided for the semiconductor switch 2C. Also, for semiconductor switch 2D, snubber times 25, an auxiliary circuit 26 and the regenerative circuit 27 lies in that connected in the same manner as described above.
[0041]
FIG. 23 shows operation waveforms when the switch 30 of FIG. 18 is connected to the terminal 30A side. Since the DC output operation is the same as that in FIG. 14, the energy regeneration operation of the snubber capacitor 141 attached to the semiconductor switch element 2A will be described here.
When the semiconductor switch element 2A is turned off, the snubber capacitor 141 suppresses the voltage increase rate of the semiconductor switch element 2A. Next, the charge stored in the snubber capacitor 141 during the periods {circle around (1)} and {circle around (2)} in which the semiconductor switch element 2A is on, the snubber capacitor 141 → auxiliary diode 151 → auxiliary reactor 152 → auxiliary capacitor 153 → semiconductor switch The auxiliary reactor 152 and the auxiliary capacitor 153 are discharged through the path of the element 2A. When the snubber capacitor 141 is discharged to 0 V, current flows through the path of the auxiliary reactor 152 → the auxiliary capacitor 153 → the snubber diode 142 → the auxiliary diode 151 by the energy stored in the auxiliary reactor 152, and the energy is transferred to the auxiliary capacitor 153. Further, during the period (5) to (7) during which the semiconductor switch elements 2B and 2C are on, the electric charge stored in the auxiliary capacitor 153 is as follows: auxiliary capacitor 153 → regenerative reactor 181 → regenerative diode 182 → semiconductor switch element 2C. The regenerative reactor 181 is discharged through a route. In the period {circle around (8)} when the semiconductor switch element 2C is off, the energy stored in the regenerative reactor 181 is as follows: the regenerative reactor 181 → the regenerative diode 182 → the first snubber circuit 13 → the regenerative diode 272 → the regenerative reactor 271. The current flows through the path of the auxiliary capacitor 263 → the transformer primary winding 42 → the transformer primary winding 41 → the auxiliary capacitor 153, and energy is released to the first snubber circuit 13. Finally, during the period {circle around (1)} to {circle around (3)} in which the semiconductor switch elements 2A and 2D are simultaneously turned on, the charge stored in the first snubber circuit 13 is changed from the first snubber circuit 13 to the semiconductor switch element 2D. → Transformer primary winding 42 → Discharge through the path of the DC power source 1 and release the energy absorbed by the first snubber circuit 13 to the load. The above operation is the same for each energy regeneration operation of the snubber capacitor 191 attached to the semiconductor switch element 2B, the snubber capacitor 221 attached to the semiconductor switch element 2C, and the snubber capacitor 251 attached to the semiconductor switch element 2D. It is.
FIG. 19 shows a modification of FIG. The difference from FIG. 18 is that the positive terminal of the DC power source 1 is connected to the parallel connection point of the semiconductor switch element 2A and the semiconductor switch element 2B, and the negative terminal of the DC power source 1 is connected to one terminal of the switch 30. In the point. However, the operation is exactly the same as in FIG.
[0042]
【The invention's effect】
According to the first to third aspects of the present invention, the energy stored in the snubber circuit is regenerated to the DC power source or released to the load, so that almost no loss occurs in the snubber circuit. In addition, according to the inventions of claims 4 to 6, since the rate of voltage increase at the time of turn-off of the semiconductor switch element can be reduced, there is an advantage that switching loss and heat generation are reduced. As a result, the conversion efficiency of the device is improved, and the cooling device for heat dissipation can be reduced in size.
According to the seventh and eighth aspects of the present invention, when the voltage of the DC power source is below a certain value, it operates as a one-stone forward converter or a push-pull type converter, and the transformer turns ratio is (n11 + n12): n2 Since it changes to n11: n2, there is not much change in the period during which the semiconductor switch element is turned on even when the DC power supply voltage is low, thereby reducing conduction loss. In addition, when the DC power supply voltage is a certain value or more, the voltage generated in the transformer secondary winding is Ed × n2 / (n11 + n12). Therefore, the diode constituting the rectifier circuit has a higher withstand voltage than the conventional one. Can be selected at low cost.
Further, by adding a snubber circuit, an auxiliary circuit and a regenerative circuit to the inventions of claims 7 and 8 as in the inventions of claims 9 and 10, not only a loss is hardly generated in the snubber circuit, There is also an advantage that the switching loss and the heat generated when the semiconductor switch element is turned off are reduced. As a result, the conversion efficiency of the device is improved, and the cooling device for heat dissipation can be miniaturized.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a first embodiment according to the present invention.
FIG. 2 is a circuit diagram showing a modification of FIG.
FIG. 3 is an operation explanatory diagram of FIGS. 1 and 2;
FIG. 4 is a circuit diagram showing a second embodiment according to the present invention.
FIG. 5 is a circuit diagram showing a modification of FIG. 4;
6 is an operation explanatory diagram of FIGS. 4 and 5. FIG.
FIG. 7 is a circuit diagram showing a third embodiment according to the present invention.
FIG. 8 is a circuit diagram showing a fourth embodiment according to the present invention.
FIG. 9 is a circuit diagram showing a modification of FIG. 8;
10 is an operation explanatory diagram of FIG. 7. FIG.
FIG. 11 is an operation explanatory diagram of FIGS. 8 and 9;
FIG. 12 is a circuit diagram showing a fifth embodiment according to the present invention.
13 is a circuit diagram showing a modification of FIG. 12. FIG.
FIG. 14 is a circuit diagram showing a sixth embodiment according to the present invention.
FIG. 15 is a circuit diagram showing a modification of FIG. 14;
FIG. 16 is a circuit diagram showing a seventh embodiment according to the present invention.
FIG. 17 is a circuit diagram showing a modification of FIG. 16;
FIG. 18 is a circuit diagram showing an eighth embodiment according to the present invention.
FIG. 19 is a circuit diagram showing a modification of FIG. 18;
20 is an operation explanatory diagram of FIGS. 12 and 13. FIG.
FIG. 21 is an operation explanatory diagram of FIGS. 14 and 15;
FIG. 22 is an operation explanatory diagram of FIGS.
FIG. 23 is an operation explanatory diagram of FIGS.
FIG. 24 is a circuit diagram showing a first conventional example.
25 is an operation explanatory diagram of FIG. 24. FIG.
FIG. 26 is a circuit diagram showing a second conventional example.
FIG. 27 is a circuit diagram showing a third conventional example.
FIG. 28 is an operation explanatory diagram of FIG. 26;
29 is an explanatory diagram of the operation of FIG. 27. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... DC power supply, 2A, 2B, 2C, 2D ... Semiconductor switch element, 3A, 3B ... Diode, 4 ... Transformer, 5 ... Rectifier circuit, 6 ... Smoothing circuit (smoothing filter), 7, 10, 13, 14, 16, 19, 22, 25 ... snubber circuit, 8, 11, 15, 17, 20, 23, 26 ... auxiliary circuit, 9, 12, 154, 174, 182, 212, 242, 272 ... regenerative diode, 18, 21 , 24, 27 ... regenerative circuit, 30 ... switch, 30A, 30B ... terminal of switch 30, 31A, 32A ... capacitor, 40 ... input voltage detection circuit, 41 ... transformer primary winding, 42 ... transformer reset winding, 43 ... Transformer secondary winding, 50 ... Control circuit, 71,101,142,162,192,222,252 ... Snubber diode, 72,102,141,161,191,221,25 ... Snubber capacitor, 73 ... Discharge resistance, 81, 111, 151, 171, 201, 231, 261 ... Auxiliary diode, 82, 112, 152, 172, 202, 232, 262 ... Auxiliary reactor, 113, 153, 173, 203 , 233, 263 ... auxiliary capacitors, 181, 211, 241, 271 ... regenerative reactors.

Claims (10)

直流電源と、一次側にリセット巻線を持つ変圧器と、この変圧器の二次側に接続される整流回路と、その整流出力を平滑化する平滑回路とからなり、直流電源から絶縁された直流電力を取り出す直流−直流変換装置において、
第１のダイオードの一方の端子と第１の半導体スイッチ素子の一方の端子とを直列接続した第１の直列アームと、第２の半導体スイッチ素子の一方の端子と第２のダイオードの一方の端子とを直列接続した第２の直列アームと、第１のスナバ回路とをそれぞれ並列に接続するとともに、前記変圧器一次巻線のリセット巻線を接続していない側の端子を前記第１の直列アームの接続点に、また、前記変圧器リセット巻線の一次巻線を接続していない側の端子を前記第２の直列アームの接続点に、さらには、前記直流電源を変圧器の一次巻線とリセット巻線の接続点と前記第１の半導体スイッチ素子と前記第２のダイオードの接続点との間に並列に、それぞれ接続したことを特徴とする直流−直流変換装置。Consists of a DC power supply, a transformer having a reset winding on the primary side, a rectifier circuit connected to the secondary side of the transformer, and a smoothing circuit that smoothes the rectified output, and is insulated from the DC power supply In a DC-DC converter that extracts DC power,
A first series arm in which one terminal of the first diode and one terminal of the first semiconductor switch element are connected in series; one terminal of the second semiconductor switch element; and one terminal of the second diode And a first snubber circuit connected in parallel to each other, and a terminal on the side of the transformer primary winding not connected to the reset winding is connected to the first series arm. The terminal on the side where the primary winding of the transformer reset winding is not connected is connected to the connection point of the arm, and the DC power supply is connected to the primary winding of the transformer. A DC-DC converter characterized by being connected in parallel between a connection point of a line and a reset winding and a connection point of the first semiconductor switch element and the second diode, respectively. スナバダイオードとスナバコンデンサとを直列接続した第２のスナバ回路を前記第１の半導体スイッチ素子と並列に、また、補助ダイオードと補助リアクトルとの直列回路に補助コンデンサを直列接続した補助回路を前記スナバダイオードと並列に、さらに、回生用ダイオードを前記直列回路と前記補助コンデンサとの接続点と前記第２の半導体スイッチ素子の並列接続点との間にそれぞれ接続したことを特徴とする請求項１に記載の直流−直流変換装置。A second snubber circuit in which a snubber diode and a snubber capacitor are connected in series is parallel to the first semiconductor switch element, and an auxiliary circuit in which an auxiliary capacitor is connected in series to a series circuit of an auxiliary diode and an auxiliary reactor is the snubber. 2. The diode according to claim 1, further comprising a regenerative diode connected in parallel with the diode between a connection point of the series circuit and the auxiliary capacitor and a parallel connection point of the second semiconductor switch element. The DC-DC converter as described. 前記第２の半導体スイッチ素子のオン期間を、前記第１のスナバ回路を構成するコンデンサの静電容量と前記変圧器の漏れインダクタンスとで決まる共振周期のほぼ１／２とすることを特徴とする請求項１または２のいずれかに記載の直流−直流変換装置。The ON period of the second semiconductor switch element is set to be approximately ½ of the resonance period determined by the capacitance of the capacitor constituting the first snubber circuit and the leakage inductance of the transformer. The DC-DC converter according to claim 1 or 2. 第１のダイオードと第１の半導体スイッチ素子とを直列接続した第１の直列アームと、第２の半導体スイッチ素子と第２のダイオードとを直列接続した第２の直列アームと、直流電源とを互いに並列に接続し、変圧器一次巻線を前記第１の直列アームの直列接続点と、前記第２の直列アームの直列接続点との間に接続するとともに、変圧器の二次巻線には整流回路、この整流回路には平滑回路をそれぞれ接続してなる直流−直流変換装置において、
前記第１の半導体スイッチ素子と第２の半導体スイッチ素子のそれぞれに、スナバダイオードとスナバコンデンサとを直列接続したスナバ回路をそれぞれ並列に、また、前記スナバダイオードのそれぞれには補助ダイオードと補助リアクトルとを直列接続した直列回路に補助コンデンサを直列接続した補助回路を並列に、さらに回生ダイオードを前記直列回路と前記補助コンデンサとの接続点と、前記第１，第２の直列アームの並列接続点との間にそれぞれ接続したことを特徴とする直流−直流変換装置。A first series arm in which a first diode and a first semiconductor switch element are connected in series, a second series arm in which a second semiconductor switch element and a second diode are connected in series, and a DC power source The transformer primary winding is connected between the series connection point of the first series arm and the series connection point of the second series arm, and is connected to the secondary winding of the transformer. Is a rectifier circuit, and a DC-DC converter comprising a smoothing circuit connected to the rectifier circuit,
A snubber circuit in which a snubber diode and a snubber capacitor are connected in series is connected in parallel to each of the first semiconductor switch element and the second semiconductor switch element, and each of the snubber diodes includes an auxiliary diode, an auxiliary reactor, and An auxiliary circuit in which an auxiliary capacitor is connected in series to a series circuit in which an auxiliary capacitor is connected in series; a regenerative diode; a connection point between the series circuit and the auxiliary capacitor; and a parallel connection point between the first and second series arms. A DC-DC converter characterized by being connected to each other. 半導体スイッチ素子とダイオードとを逆並列接続した２組のスイッチング素子を直列接続した第１の直列アームと、コンデンサを直列接続した第２の直列アームと、直流電源とを互いに並列に接続し、変圧器一次巻線を前記第１の直列アームの直列接続点と、前記第２の直列アームの直列接続点との間に接続するとともに、変圧器の二次巻線には整流回路、この整流回路には平滑回路をそれぞれ接続してなる直流−直流変換装置において、
前記スイッチング素子のそれぞれには、スナバダイオードとスナバコンデンサとを直列接続したスナバ回路を並列に、また、前記スナバダイオードのそれぞれには、補助ダイオードと補助リアクトルとを直列接続した直列回路に補助コンデンサを直列接続した補助回路を並列に、さらに回生ダイオードを前記直列回路と前記補助コンデンサとの接続点と、前記第１，第２の直列アームの並列接続点との間にそれぞれ接続したことを特徴とする直流−直流変換装置。A first series arm in which two sets of switching elements in which a semiconductor switch element and a diode are connected in antiparallel are connected in series, a second series arm in which capacitors are connected in series, and a DC power source are connected in parallel to each other, The primary winding of the transformer is connected between the series connection point of the first series arm and the series connection point of the second series arm, and a rectifier circuit is provided in the secondary winding of the transformer. In a DC-DC converter that is connected to a smoothing circuit,
Each of the switching elements has a snubber circuit connected in series with a snubber diode and a snubber capacitor, and each of the snubber diodes has an auxiliary capacitor in a series circuit where an auxiliary diode and an auxiliary reactor are connected in series. The auxiliary circuit connected in series is connected in parallel, and the regenerative diode is further connected between the connection point of the series circuit and the auxiliary capacitor, and the parallel connection point of the first and second series arms. DC-DC converter. 半導体スイッチ素子とダイオードとを逆並列接続した２組のスイッチング素子を直列接続した第１の直列アームと、コンデンサを直列接続した第２の直列アームと、直流電源とを互いに並列に接続し、変圧器一次巻線を前記第１の直列アームの直列接続点と、前記第２の直列アームの直列接続点との間に接続するとともに、変圧器の二次巻線には整流回路、この整流回路には平滑回路をそれぞれ接続してなる直流−直流変換装置において、
前記スイッチング素子と前記変圧器一次巻線の接続点との間に補助リアクトルをそれぞれ直列に、前記スイッチング素子のそれぞれには、スナバダイオードとスナバコンデンサとを直列接続したスナバ回路を並列に、補助ダイオードと補助コンデンサとを直列接続した補助回路を前記スナバ回路の直列接続点と前記補助リアクトルと前記変圧器一次巻線の接続点との接続点間に、回生ダイオードを前記補助回路の直列接続点と前記第１，第２の直列アームの並列接続点間にそれぞれ接続したことを特徴とする直流−直流変換装置。A first series arm in which two sets of switching elements in which a semiconductor switch element and a diode are connected in antiparallel are connected in series, a second series arm in which capacitors are connected in series, and a DC power source are connected in parallel to each other, The primary winding of the transformer is connected between the series connection point of the first series arm and the series connection point of the second series arm, and a rectifier circuit is provided in the secondary winding of the transformer. In a DC-DC converter that is connected to a smoothing circuit,
An auxiliary reactor is connected in series between the switching element and the connection point of the transformer primary winding, and a snubber circuit in which a snubber diode and a snubber capacitor are connected in series is connected in parallel to each of the switching elements. And an auxiliary circuit connected in series between a series connection point of the snubber circuit and a connection point of the auxiliary reactor and the connection point of the primary winding of the transformer, a regenerative diode and a series connection point of the auxiliary circuit A DC-DC converter device connected between parallel connection points of the first and second series arms. 第１のダイオードの一方の端子と第１の半導体スイッチ素子の一方の端子とを直列接続した第１の直列アームと、第２の半導体スイッチ素子の一方の端子と第２のダイオードの一方の端子とを直列接続した第２の直列アームと、第１のスナバ回路とをそれぞれ並列に接続するとともに、中間端子を備えた変圧器一次巻線の一方の端子を前記第１の直列アームの直列接続点に、前記変圧器一次巻線の他方の端子を前記第２の直列アームの直列接続点にそれぞれ接続し、また、直流電源を３端子スイッチの第１の端子と前記第１の半導体スイッチ素子と前記第２のダイオードとの並列接続点間に、前記３端子スイッチの第２の端子を前記変圧器の中間端子に、前記３端子スイッチの第３の端子を前記第１のダイオードと前記第２の半導体スイッチ素子との並列接続点間にそれぞれ接続し、さらには、入力電圧検出回路を前記直流電源と並列に、制御回路を前記入力電圧検出回路と前記３端子スイッチとの間に、前記変圧器の二次端子を整流回路に、この整流回路を平滑フィルタにそれぞれ接続したことを特徴とする直流−直流変換装置。A first series arm in which one terminal of the first diode and one terminal of the first semiconductor switch element are connected in series; one terminal of the second semiconductor switch element; and one terminal of the second diode Are connected in parallel to each other, and one terminal of a transformer primary winding having an intermediate terminal is connected in series to the first series arm. The other terminal of the transformer primary winding is connected to the series connection point of the second series arm, and the DC power source is connected to the first terminal of the three-terminal switch and the first semiconductor switch element. And the second diode, the second terminal of the three-terminal switch is an intermediate terminal of the transformer, and the third terminal of the three-terminal switch is the first diode and the second diode. 2 semiconductor switch A parallel connection point between the input voltage detection circuit and the DC power supply; a control circuit between the input voltage detection circuit and the three-terminal switch; A DC-DC converter characterized in that the next terminal is connected to a rectifier circuit, and the rectifier circuit is connected to a smoothing filter. 第１の半導体スイッチ素子の一方の端子と第２の半導体スイッチ素子の一方の端子とを直列接続した第１の直列アームと、第３の半導体スイッチ素子の一方の端子と第４の半導体スイッチ素子の一方の端子とを直列接続した第２の直列アームと、第１のスナバ回路とをそれぞれ並列に接続するとともに、中間端子を備えた変圧器一次巻線の一方の端子を前記第１の直列アームの直列接続点に、前記変圧器一次巻線の他方の端子を前記第２の直列アームの直列接続点にそれぞれ接続し、また、直流電源を３端子スイッチの第１の端子と前記第１の半導体スイッチ素子と前記第３の半導体スイッチ素子との並列接続点間に、前記３端子スイッチの第２の端子を前記変圧器の中間端子に、前記３端子スイッチの第３の端子を前記第２の半導体スイッチ素子と前記第４の半導体スイッチ素子との並列接続点間にそれぞれ接続し、さらには、入力電圧検出回路を前記直流電源と並列に、制御回路を前記入力電圧検出回路と前記３端子スイッチとの間に、前記変圧器の二次端子を整流回路に、この整流回路を平滑フィルタにそれぞれ接続したことを特徴とする直流−直流変換装置。A first series arm in which one terminal of the first semiconductor switch element and one terminal of the second semiconductor switch element are connected in series; one terminal of the third semiconductor switch element; and a fourth semiconductor switch element A second series arm connected in series with one of the terminals and a first snubber circuit are connected in parallel, and one terminal of a transformer primary winding having an intermediate terminal is connected to the first series. The other terminal of the transformer primary winding is respectively connected to the series connection point of the arm to the series connection point of the second series arm, and a DC power source is connected to the first terminal of the three-terminal switch and the first terminal. Between the parallel connection points of the semiconductor switch element and the third semiconductor switch element, the second terminal of the three-terminal switch is the intermediate terminal of the transformer, and the third terminal of the three-terminal switch is the first terminal 2 semiconductor switches And an input voltage detection circuit connected in parallel to the DC power source, and a control circuit connected between the input voltage detection circuit and the three-terminal switch. In the meantime, a secondary terminal of the transformer is connected to a rectifier circuit, and the rectifier circuit is connected to a smoothing filter, respectively. 第１のスナバダイオードと第１のスナバコンデンサとを直列接続した第２のスナバ回路を前記第１の半導体スイッチ素子と並列に、第１の補助ダイオードと第１の補助リアクトルとを直列接続した第１の直列回路と第１の補助コンデンサとを直列接続した第１の補助回路を前記第１のスナバダイオードと並列に、第１の回生ダイオードを前記第１の直列回路と第１の補助コンデンサとの接続点と前記第１のダイオードと前記第２の半導体スイッチ素子との並列接続点間に、第２のスナバダイオードと第２のスナバコンデンサとを直列接続した第３のスナバ回路を前記第２の半導体スイッチ素子と並列に、第２の補助ダイオードと第２の補助リアクトルとを直列接続した第２の直列回路と第２の補助コンデンサとを直列接続した第２の補助回路を前記第２のスナバダイオードと並列に、第２の回生ダイオードを前記第２の直列回路と第２の補助コンデンサとの接続点と前記第２のダイオードと前記第１の半導体スイッチ素子との並列接続点間に、それぞれ接続したことを特徴とする請求項７に記載の直流−直流変換装置。A second snubber circuit in which a first snubber diode and a first snubber capacitor are connected in series is connected in parallel with the first semiconductor switch element, and a first auxiliary diode and a first auxiliary reactor are connected in series. A first auxiliary circuit in which a series circuit and a first auxiliary capacitor are connected in series with the first snubber diode, and a first regenerative diode is connected to the first series circuit and the first auxiliary capacitor. A third snubber circuit in which a second snubber diode and a second snubber capacitor are connected in series between a connection point of the second snubber capacitor and a parallel connection point of the first diode and the second semiconductor switch element. A second auxiliary circuit in which a second series circuit in which a second auxiliary diode and a second auxiliary reactor are connected in series and a second auxiliary capacitor are connected in series with the semiconductor switch element of In parallel with the second snubber diode, a second regenerative diode is connected in parallel between the connection point of the second series circuit and the second auxiliary capacitor, and the second diode and the first semiconductor switch element. The DC-DC converter according to claim 7, wherein the DC-DC converter is connected between points. 第１のスナバダイオードと第１のスナバコンデンサとを直列接続した第２のスナバ回路を前記第１の半導体スイッチ素子と並列に、第１の補助ダイオードと第１の補助リアクトルとを直列接続した第１の直列回路と第１の補助コンデンサとを直列接続した第１の補助回路を前記第１のスナバダイオードと並列に、第１の回生ダイオードと第１の回生リアクトルとを直列接続した第１の回生回路を前記第１の直列回路と前記第１の補助コンデンサとの接続点と前記第２の半導体スイッチ素子と第４の半導体スイッチ素子との並列接続点間に、第２のスナバダイオードと第２のスナバコンデンサとを直列接続した第３のスナバ回路を前記第２の半導体スイッチ素子と並列に、第２の補助ダイオードと第２の補助リアクトルとを直列接続した第２の直列回路と第２の補助コンデンサとを直列接続した第２の補助回路を前記第２のスナバダイオードと並列に、第２の回生ダイオードと第２の回生リアクトルとを直列接続した第２の回生回路を前記第２の直列回路と前記第２の補助コンデンサとの接続点と前記第１の半導体スイッチ素子と第３の半導体スイッチ素子との並列接続点間に、前記第２の直列アームについても上記と同じく、第４のスナバ回路、第５のスナバ回路、第３の補助回路、第４の補助回路、第３の回生回路および第４の回生回路をそれぞれ接続したことを特徴とする請求項８に記載の直流−直流変換装置。A second snubber circuit in which a first snubber diode and a first snubber capacitor are connected in series is connected in parallel with the first semiconductor switch element, and a first auxiliary diode and a first auxiliary reactor are connected in series. A first auxiliary circuit in which a first series circuit and a first auxiliary capacitor are connected in series is connected in parallel with the first snubber diode, and a first regeneration diode and a first regeneration reactor are connected in series. A regenerative circuit is connected between the connection point of the first series circuit and the first auxiliary capacitor and the parallel connection point of the second semiconductor switch element and the fourth semiconductor switch element, and the second snubber diode and the second A second snubber circuit in which a second auxiliary diode and a second auxiliary reactor are connected in series in parallel with the second semiconductor switch element. A second regenerative circuit in which a second regenerative diode and a second regenerative reactor are connected in series with a second auxiliary circuit in which a column circuit and a second auxiliary capacitor are connected in series in parallel with the second snubber diode Between the connection point of the second series circuit and the second auxiliary capacitor and the parallel connection point of the first semiconductor switch element and the third semiconductor switch element, the second series arm also The fourth snubber circuit, the fifth snubber circuit, the third auxiliary circuit, the fourth auxiliary circuit, the third regenerative circuit, and the fourth regenerative circuit are respectively connected to each other. The DC-DC converter described in 1.
JP18722196A 1995-10-20 1996-07-17 DC-DC converter Expired - Fee Related JP3656779B2 (en)

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