JP4126167B2

JP4126167B2 - Charge / discharge circuit for series connected battery group

Info

Publication number: JP4126167B2
Application number: JP2001278938A
Authority: JP
Inventors: 敬善田中; 英彦田島; 克明小林; 耕介原田; 俊二谷口; 和之足立; 吾一有吉; 裕之柴田
Original assignee: Kyushu Electric Power Co Inc; Mitsubishi Heavy Industries Ltd
Current assignee: Kyushu Electric Power Co Inc; Mitsubishi Heavy Industries Ltd
Priority date: 2001-09-13
Filing date: 2001-09-13
Publication date: 2008-07-30
Anticipated expiration: 2021-09-13
Also published as: JP2003087987A

Description

【０００１】
【発明の属する技術分野】
本発明は、直列接続の電池群の充放電回路に関し、特に、工場や病院などのバックアップ電源に使用されたり、夜間電力を蓄えて昼間に放出する負荷平準装置に使用されたり、電気自動車に搭載されるリチウム二次電池に適用される。
【０００２】
【従来の技術】
図１４に多数の電池を直列接続してなる電池群を示す。
以下では、その各電池が、リチウム電池である場合を例に挙げて説明する。
【０００３】
現在、開発中のリチウム電池には、単電池で約４Ｖの起電力を有しているものがある。このリチウム電池は、直列接続されて用いられることが多く、例えば、４個乃至４０個のリチウム電池が直列接続されることがある。
【０００４】
リチウム電池が直列接続されて用いられる場合、各リチウム電池の特性の相違が問題となる。すなわち、充放電を繰り返すと、各電池の特性の差により各電池電圧にばらつきが生じる。充放電動作を繰り返すと、充放電の動作時間が同じであっても、各電池の充電電圧や放電電圧に相違が出てくる。リチウム電池の場合、過充電されると、事故につながるおそれがあり、過放電されると、電池の容量がなくなってくる。これらのことから、過充電・過放電に関して厳密な保護・管理が要求される。
【０００５】
単一ラインに直列接続されたリチウム電池の電池電圧に、ばらつきが生じた場合、充電は一番最初に充電終了電圧に達した電池に合わせて終了する必要があることから、その他の電池を完全に充電することができず、放電は一番最初に放電終了電圧に達した電池に合わせて終了する必要があることから、その他の電池を完全に放電することができない。このため、直列接続の電池群全体としての十分な充電や放電ができない。
【０００６】
このばらつきを抑制する手法として、図１５に示すようなツェーナーダイオードを使用した例がある（特開平１１−３３２１１５号公報参照）。この公報記載の技術では、充電電圧が過大にならないようにする点に重点が置かれている。
しかし、ツェーナーダイオードは、大電流に適していない。ツェーナーダイオードは、１〜３Ａ程度で用いられ、４Ａを超えたレベルでは使用不可能である。
【０００７】
直列接続されたリチウム電池は、例えば、夜間電力を蓄えて昼間に放出する電力負荷平準化に用いられる。この種の用途では、１０〜２０Ａの電流を扱えることが前提となる。したがって、ツェーナーダイオード（汎用品）は、上記用途に適していない。
【０００８】
そこで、図１６に示すように、電流をバイパスする回路が検討された。電池Ｂ１に関し、通常時はスイッチＳ１１１をＯＮにし、スイッチＳ１１２をＯＦＦとしておき、バイパス時はスイッチＳ１１１をＯＦＦにし、スイッチＳ１１２をＯＮとする。
【０００９】
この回路構成によれば、スイッチＳ１１１、Ｓ１１２、…Ｓ１ｎ１、Ｓ１ｎ２の容量を大きくすれば、大電流にも適用できる。しかし、スイッチを切り換えるとき、例えば、電池Ｂ１のバイパス時には、スイッチＳ１１１をＯＦＦしてからスイッチＳ１１２をＯＮするというように、両方のスイッチＳ１１１、Ｓ１１２がＯＦＦである期間を持たせる必要があった（両スイッチＳ１１１、Ｓ１１２がＯＮであると、電池Ｂ１が短絡するため）。
【００１０】
ところが、スイッチＳ１１１、Ｓ１１２が共にＯＦＦである期間は、電流が流れるルートが無いため、それまでＯＮであったスイッチＳ１１１をＯＦＦに切り換えた瞬間から、スイッチＳ１１１の部分に過大なサージ電圧が発生するおそれがあった。この場合、状況によっては、電池を痛める要因となっていた。
【００１１】
の防止策としては、充電時に、スイッチＳ１１１、Ｓ１１２が共にＯＦＦである期間（例えば１００μｓｅｃ）に、充電電流の供給を止めることでサージ電圧の発生を未然に防ぐ手法が考えられる。ところが、この充電時と同様にサージ電圧の発生を防ぐべく、放電時において、スイッチＳ１１１、Ｓ１１２が共にＯＦＦである期間は、放電電流を流さないこととすると、その間、電流をとれなくなる。負荷側の条件によっては、常時、電流を取り出すことが必須な場合があり、その場合には、一時的にせよ、電流が出力されなくなる事態は回避されなければならない。
【００１２】
別の防止策としては、サージ吸収回路（例えばスナバ回路）を設けることで、サージ電圧の発生を防止することが考えられる。しかしながら、サージ吸収回路を設けた分だけ、損失（ロス）が大きくなり、充放電時に電池の容量を最大限に生かすことができない。したがって、サージ吸収回路の使用は避けることが望ましい。
【００１３】
非特許文献１は、直列接続システムにおける劣化電池の除去について開示している。この非特許文献１の回路では、バッテリと直列に並列ダイオードを備えたスイッチが接続され、更に、バッテリとスイッチの直列接続と並列に並列スイッチが接続されている。或る負荷に電力を供給するときには、スイッチが閉じてダイオードは短絡される。バッテリが充電されるときは、スイッチが開いてダイオードが導通状態になり、ダイオードを経由して充電電流が供給される。バッテリを劣化電池として除去する場合には、並列スイッチが閉じられる。
【非特許文献１】
K. Harada, S. Taniguchi, K. Adachi, G. Ariyoshi, Y. Kawata, "On the Removing of a Less Quality Battery from a Series-Connected System", 22nd International Telecommunications Energy Conference INTELEC 2000, (2000.09.10), p.761-764
【００１４】
【発明が解決しようとする課題】
本発明の目的は、簡単な構成で充放電動作を中断することなく、劣化電池を除外または電圧を均等化させることができる、直列接続の電池群の充放電回路を提供することにある。
【００１５】
本発明の他の目的は、簡単な構成で充放電動作を中断することなく、劣化電池を除外または電圧を均等化させることができる、直列接続の電池群の充放電回路を提供することにある。
【００１６】
【課題を解決するための手段】
以下に、［発明の実施の形態］で使用する番号・符号を用いて、［課題を解決するための手段］を説明する。これらの番号・符号は、［特許請求の範囲］の記載と［発明の実施の形態］の記載との対応関係を明らかにするために付加されたものであるが、［特許請求の範囲］に記載されている発明の技術的範囲の解釈に用いてはならない。
【００１７】
本発明の直列接続の電池群の充放電回路は、充電電流（Ｉｒ）に対して順方向に配置された第１ダイオード（Ｄｎ１）と前記第１ダイオード（Ｄｎ１）に並列に接続された第１スイッチ（Ｓｎ１）とからなる第１のスイッチング・アセンブリと、電池（Ｂｎ）とを接続して成る直列単体を複数直列に接続した電池群と、前記充電電流（Ｉｒ）に対して逆方向に配置された第２ダイオード（Ｄｎ２）と前記第２ダイオード（Ｄｎ２）に並列に接続された第２スイッチ（Ｓｎ２）とから成り、前記直列単体に並列に接続された第２のスイッチング・アセンブリと、
充電時に第１の前記直列単体の前記電池（Ｂ１）の電池電圧が所定値以上になったときに前記第１の直列単体の前記第１スイッチ（Ｓ１１）をＯＦＦにし、その後、前記第１の直列単体に並列に接続された前記第２のスイッチング・アセンブリの前記第２スイッチ（Ｓ１２）をＯＮにして前記第１の直列単体の前記電池（Ｂ１）をバイパスさせる制御部とを備えている。
【００１８】
本発明の直列接続の電池群の充放電回路において、前記制御部は、放電時に第２の前記直列単体の前記電池（Ｂ１）の電池電圧が所定値以下になったときに前記第２の直列単体の前記第１スイッチ（Ｓ１１）をＯＦＦにし、その後、前記第２の直列単体に並列に接続された前記第２のスイッチング・アセンブリの前記第２スイッチ（Ｓ１２）をＯＮにして前記第２の直列単体の前記電池（Ｂ１）をバイパスさせる。
【００１９】
本発明の直列接続の電池群の充放電回路は、充電電流（Ｉｒ）に対して順方向にその第１のボディダイオードが形成されるように配置された第１のＭＯＳ−ＦＥＴ（Ｓｎ１）と、電池（Ｂｎ）とを接続して成る直列単体を複数直列に接続した電池群と、前記充電電流（Ｉｒ）に対して逆方向にその第２のボディダイオードが形成されるように配置され前記直列単体に並列に接続された第２のＭＯＳ−ＦＥＴ（Ｓｎ２）と、充電時に第１の前記直列単体の前記電池（Ｂ１）の電池電圧が所定値以上になったときに前記第１の直列単体の前記第１のＭＯＳ−ＦＥＴ（Ｓ１１）をＯＦＦにし、その後、前記第１の直列単体に並列に接続された前記第２のＭＯＳ−ＦＥＴ（Ｓ１２）をＯＮにして前記第１の直列単体の前記電池（Ｂ１）をバイパスさせる制御部とを備えている。
【００２０】
本発明の直列接続の電池群の充放電回路において、前記制御部は、放電時に第２の前記直列単体の前記電池（Ｂ１）の電池電圧が所定値以下になったときに前記第２の直列単体の前記第１のＭＯＳ−ＦＥＴ（Ｓ１１）をＯＦＦにし、その後、前記第２の直列単体に並列に接続された前記第２のＭＯＳ−ＦＥＴ（Ｓ１２）をＯＮにして前記第２の直列単体の前記電池（Ｂ１）をバイパスさせる。
【００２１】
本発明の直列接続の電池群の充放電回路において、前記制御部が前記電池（Ｂ１）をバイパスさせるときの動作基準は、前記電池群のそれぞれの前記電池（Ｂｎ）の電池電圧が所定の値に達しているか否かにより決定される。
【００２２】
本発明の直列接続の電池群の充放電回路において、前記制御部が前記電池（Ｂ１）をバイパスさせるときの動作基準は、前記電池群に含まれる二つの前記電池（Ｂｎ）の電圧差により決定される。
【００２３】
【発明の実施の形態】
本発明の一実施形態が説明される。
【００２４】
図１を参照して、本発明の直列接続の電池群の充放電回路の一実施形態として、リチウム二次電池のバイパス回路について説明する。
【００２５】
電力貯蔵、電気自動車用として、電池を使用する場合、電気の貯蔵容量を上げるため複数の電池を直列接続し、組電池として使用する必要がある。しかし実際には、電池を直列に接続した場合、劣化電池の混在や個々の電池のばらつき等により、充放電時において、電池の過充電や過放電が生じる。本発明では、これらの問題を解決するために、以下の方法を採用している。
【００２６】
図１に示すように、各スイッチＳ１１、Ｓ１２、…Ｓｎ１、Ｓｎ２に併設してダイオードＤ１１、Ｄ１２、…Ｄｎ１、Ｄｎ２が設けられている。ダイオードＤ１１、…Ｄｎ１は、充電電流に対して順方向に配置されている。ダイオードＤ１２、…Ｄｎ２は、放電電流に対して順方向に配置されている。
【００２７】
図１において充電電流に対して順方向に配置されたダイオードＤｎ１と、これに並列に接続されたスイッチＳｎ１とから成る第１のスイッチング・アセンブリを介して電池Ｂｎを直列に接続して電池群を構成している。
第２のスイッチング・アセンブリは、第１のスイッチング・アセンブリと電池Ｂｎとを接続して成る直列単体に並列に接続され、充電電流に対して逆方向に配置されたダイオードＤｎ２と、これに並列に接続されたスイッチＳｎ２とから成る。
【００２８】
まず、充電時に電池Ｂ１をバイパスする動作について説明する。
【００２９】
まず、バイパスが行われない通常時は、スイッチＳ１１はＯＮされており、充電電流は、スイッチＳ１１を経由して電池Ｂ１に流れる。
【００３０】
次に、電池Ｂ１の電池電圧が所定の電圧以上になった場合に、スイッチＳ１１をＯＦＦにする。スイッチＳ１１をＯＦＦにすると、充電電流は、ダイオードＤ１１を経由して電池Ｂ１に流れる（このときには、電池Ｂ１への充電は継続している）。
【００３１】
次に、スイッチＳ１２をＯＮにすると、ダイオードＤ１１のターンオン電圧よりもスイッチＳ１２のオン電圧の方が小さいため、充電電流はスイッチＳ１２を経由して流れ、電池Ｂ１はバイパスされる。また、このとき、ダイオードＤ１１は、電池Ｂ１によって逆バイアス状態とされており、ダイオードＤ１１の導通はＯＦＦされる。
【００３２】
次に、放電時に電池Ｂ１をバイパスする動作について説明する。
【００３３】
まず、バイパスが行われない通常時は、スイッチＳ１１はＯＮされており、放電電流は、電池Ｂ１の＋端子側からスイッチＳ１１を経由して外部の負荷（図示せず）に流れる。
【００３４】
次に、電池Ｂ１の電池電圧が所定の電圧以下になった場合に、スイッチＳ１１をＯＦＦにする。スイッチＳ１１をＯＦＦにすると、放電電流は、ダイオードＤ１２を経由して外部の負荷に流れる。これにより、放電時に電池Ｂ１をバイパスさせても、放電電流の電流路が確保される。
【００３５】
ダイオードＤ１２は、ターンオン電圧が高く、ダイオードＤ１２を経由して長時間、放電電流が流れると損失が大きい。放電電流が大電流（例えば、２０Ａ程度）の場合に、問題となる。そこで、スイッチＳ１２をＯＮにして、スイッチＳ１２経由で放電電流を流す。これにより、ダイオードＤ１２を経由したときに比べて、損失が有効に抑えられる。
【００３６】
以上の動作から、充電時および放電時に電池Ｂ１をバイパスする間の電流路が常に確保され、電流の連続性が保たれることになる。よって、サージ吸収回路は不要であり、また、充電電流の供給を停止する必要もない。
【００３７】
図２に具体的な実施例を示す。
図２において、図１と同じ機能をする部材には、同じ符号が付与される。
【００３８】
図２に示すように、スイッチ部はＭＯＳ−ＦＥＴにて構成する。ＭＯＳ−ＦＥＴは、その構造上、ソースからドレインに向けてダイオード部（これをボディダイオードという）が構成されるので、それを利用すると回路構成が簡単になる。ボディダイオードは、ＭＯＳ−ＦＥＴと同じ電流容量を有している。
【００３９】
ＭＯＳ−ＦＥＴＳ１２、Ｓｎ２は、バイパス用スイッチとして機能する。
また、ＭＯＳ−ＦＥＴＳ１１、Ｓ１２、…Ｓｎ１、Ｓｎ２がＯＮされたときには、電流の流れる向きは、ドレインからソースへの向きでも、ソースからドレインへの向きでも構わないため、双方向スイッチとして機能することができる。なお、図２では、ＭＯＳ−ＦＥＴが、１段設けられているが、大電流の場合、ＭＯＳ−ＦＥＴをパラレルに多段に設けることができる。
【００４０】
次に、本実施例の動作について説明する。
【００４１】
まず、充電時に電池Ｂ１をバイパスする動作について説明する。
【００４２】
まず、バイパスが行われない通常時は、ＭＯＳ−ＦＥＴＳ１１のゲートにバイアス電圧を印加して、ＭＯＳ−ＦＥＴＳ１１はＯＮされており、充電電流は、ＭＯＳ−ＦＥＴＳ１１を経由して電池Ｂ１に流れる。
【００４３】
次に、電池Ｂ１の電池電圧が所定の電圧（例えば、４、２Ｖ）以上になった場合に、ＭＯＳ−ＦＥＴＳ１１のゲートに逆バイアス電圧を印加して、ＭＯＳ−ＦＥＴＳ１１をＯＦＦにする。ＭＯＳ−ＦＥＴＳ１１をＯＦＦにすると、充電電流は、ＭＯＳ−ＦＥＴＳ１１のボディダイオードを経由して電池Ｂ１に流れる（このときには、電池Ｂ１への充電は継続している）。
【００４４】
次に、ＭＯＳ−ＦＥＴＳ１２のゲートに所定電圧を印加して、ＭＯＳ−ＦＥＴＳ１２をＯＮにすると、ＭＯＳ−ＦＥＴＳ１１のボディダイオードのターンオン電圧よりもＭＯＳ−ＦＥＴＳ１２のオン電圧の方が小さいため、充電電流はＭＯＳ−ＦＥＴＳ１２を経由して流れ、電池Ｂ１はバイパスされる。
【００４５】
次に、放電時に電池Ｂ１をバイパスする動作について説明する。
【００４６】
まず、バイパスが行われない通常時は、ＭＯＳ−ＦＥＴＳ１１のゲートにバイアス電圧を印加して、ＭＯＳ−ＦＥＴＳ１１はＯＮされており、放電電流は、電池Ｂ１の＋端子側からＭＯＳ−ＦＥＴＳ１１を経由して外部の負荷（図示せず）に流れる。
【００４７】
次に、電池Ｂ１の電池電圧が所定の電圧（例えば、３、３Ｖ）以下になった場合に、ＭＯＳ−ＦＥＴＳ１１のゲートに逆バイアス電圧を印加して、ＭＯＳ−ＦＥＴＳ１１をＯＦＦにする。ＭＯＳ−ＦＥＴＳ１１をＯＦＦにすると、放電電流は、ＭＯＳ−ＦＥＴＳ１２のボディダイオードを経由して外部の負荷に流れる。これにより、放電時に電池Ｂ１をバイパスさせても、放電電流の電流路が確保される。
【００４８】
ＭＯＳ−ＦＥＴＳ１２のボディダイオードは、ターンオン電圧が高く、そのボディダイオードを経由して長時間、放電電流が流れると損失が大きい。そこで、ＭＯＳ−ＦＥＴＳ１２のゲートにバイアス電圧を印加して、ＭＯＳ−ＦＥＴＳ１２をＯＮにして、ＭＯＳ−ＦＥＴＳ１２経由で放電電流を流す。これにより、ＭＯＳ−ＦＥＴＳ１２のボディダイオードを経由したときに比べて、放電電流の損失が有効に抑えられる。
【００４９】
以上の動作から、充電時および放電時に電池Ｂ１をバイパスする間の電流路が常に確保され、電流の連続性が保たれることになる。よって、サージ吸収回路は不要であり、また、充電電流の供給を停止する必要もない。
【００５０】
ＭＯＳ−ＦＥＴのボディダイオードのターンオン電圧は、一般に高いため、そのボディダイオードに所定時間以上、電流が流れることで、発熱等により、そのＭＯＳ−ＦＥＴが損傷するおそれがある。本実施例において、充電電流が、ＭＯＳ−ＦＥＴＳ１１のボディダイオードを流れる時間は、ＭＯＳ−ＦＥＴＳ１１がＯＦＦにされてから、ＭＯＳ−ＦＥＴＳ１２がＯＮになるまでの切り換えに要する僅かな時間のみである（例えば、数百μｓｅｃ）。同様に、放電電流がＭＯＳ−ＦＥＴＳ１２のボディダイオードを流れる時間は、ＭＯＳ−ＦＥＴＳ１１がＯＦＦにされてから、ＭＯＳ−ＦＥＴＳ１２がＯＮになるまでの切り換えに要する僅かな時間のみである（例えば、数百μｓｅｃ）。したがって、本実施例では、ボディダイオードに電流が流れることで、ＭＯＳ−ＦＥＴＳ１１、Ｓ１２が損傷するおそれはない。
【００５１】
このように、本実施例では、ボディダイオードに電流が流れる時間が短時間であり、その使用に伴う不利益が生じないため、ボディダイオード以外のダイオード（個別素子）を用いる必要が無い。
【００５２】
図２では、電池の＋端子側にスイッチ部があるが、図３に示すように電池の−端子側にスイッチ部があっても問題ない。
【００５３】
バイパス動作は、以下のように行うことが可能である。充電時と放電時に分けて説明する。充放電のそれぞれの各時点について（１）、（２）の２つの方法がある。
【００５４】
［１］充電時
（１）各電池電圧を計測し、その電圧が所定の値に達した場合に、その電池をバイパスする。バイパス解除は放電時に行う。
（２）各電池電圧を計測し、二つの電池電圧を比較して、その差が規定の電圧に達した場合に、電圧の高い電池をバイパスする。電池電圧が低かった電池の電池電圧がその差分だけ上昇した際にバイパスした電池のバイパスを解除する。
【００５５】
［２］放電時
（１）各電池電圧を計測し、その電圧が所定の値に達した場合に、その電池をバイパスする。バイパス解除は充電時に行う。
（２）各電池電圧を計測し、二つの電池電圧を比較して、その差が規定の電圧に達した場合に、電圧の低い電池をバイパスする。電池電圧が高かった電池の電池電圧がその差分だけ降下した際に、バイパスした電池のバイパスを解除する。
【００５６】
次に、図４および図５を参照して、上記［１］の（１）について具体的に説明する。ここでは、バイパスすべき電池は、劣化電池として除去するものとして説明する。但し、バイパスすべき電池であっても、劣化電池として除去されずに、そのまま利用される場合があることはいうまでもない。
【００５７】
図４は、仮に電池を４個用いた場合の充電時の動作フロー図であり、図５は、充電時の劣化電池の除去回路構成図である。
【００５８】
図５において、充電時の初期状態は、第１のスイッチング・アセンブリのＭＯＳ−ＦＥＴＳｎ１がＯＮされており、第２のスイッチング・アセンブリのスイッチＳｎ２のＭＯＳ−ＦＥＴＳｎ２がＯＦＦとされている。
【００５９】
充電装置からの充電時に上記の第１のスイッチング・アセンブリのＭＯＳ−ＦＥＴＳｎ１がＯＮされており、ＭＯＳ−ＦＥＴＳｎ１を介して充電電流を流し、それぞれの電池Ｂｎの電圧を監視する（Ｓ１）。その監視の結果、異常な電圧増加を示す劣化電池を検出する（Ｓ２）と、それの第１のスイッチング・アセンブリのＭＯＳ−ＦＥＴＳｎ１をＯＦＦにし、その後、それの第２のスイッチング・アセンブリのスイッチＳｎ２のＭＯＳ−ＦＥＴＳｎ２をＯＮにし（Ｓ３）充電電流を迂回することによりシステムを停止せずに上記の劣化電池を除外し、その後劣化電池を新品電池と交換し全ての電池が同じ電圧になるとそれの第２のスイッチング・アセンブリのＭＯＳ−ＦＥＴＳｎ２をＯＦＦにし、その後、それの第１のスイッチング・アセンブリのＭＯＳ−ＦＥＴＳｎ１をＯＮにして（Ｓ４）正常な状態に復帰させる。
【００６０】
次に、図６および図７を参照して、上記［２］の（１）について具体的に説明する。ここでは、バイパスすべき電池は、劣化電池として除去するものとして説明する。但し、バイパスすべき電池であっても、劣化電池として除去されずに、そのまま利用される場合があることはいうまでもない。
【００６１】
図６は、仮に電池を４個用いた場合の放電時の動作フロー図（除去回路）であり、図７は、放電時の劣化電池の除去回路構成図である。
【００６２】
図７において、放電時の初期状態は、第１のスイッチング・アセンブリのＭＯＳ−ＦＥＴＳｎ１がＯＮされており、第２のスイッチング・アセンブリのスイッチＳｎ２のＭＯＳ−ＦＥＴＳｎ２がＯＦＦとされている。
【００６３】
負荷への放電時には上記の第１のスイッチング・アセンブリのＭＯＳ−ＦＥＴＳｎ１がＯＮされており、ＭＯＳ−ＦＥＴＳｎ１を介して放電電流を流し、それぞれの電池Ｂｎの電圧を監視する（Ｓ５）。その監視の結果、異常な電圧低下を示す劣化電池を検出する（Ｓ６）と、それの第１のスイッチング・アセンブリのＭＯＳ−ＦＥＴＳｎ１をＯＦＦにし、その後、それの第２のスイッチング・アセンブリのスイッチＳｎ２のＭＯＳ−ＦＥＴＳｎ２をＯＮにし（Ｓ７）放電電流を迂回することによりシステムを停止せずに上記の劣化電池を除外し、その後劣化電池を新品電池と交換し全ての電池が同じ電圧になるとそれの第２のスイッチング・アセンブリのＭＯＳ−ＦＥＴＳｎ２をＯＦＦにし、その後、それの第１のスイッチング・アセンブリのＭＯＳ−ＦＥＴＳｎ１をＯＮにして（Ｓ８）正常な状態に復帰させる。
【００６４】
次に、図８から図１０を参照して、上記［１］の（２）について具体的に説明する。
【００６５】
図８は劣化電池の均等化動作について仮に電池を４個用いた場合の充電時における劣化電池をバイパスする電圧均等化回路図であり、図９はそのときの時間と電圧の関係を示すグラフ図であり、図１０はそのときの動作を示すフローチャート図である。
【００６６】
図８において、直列に接続された電池Ｂ１、Ｂ２、Ｂ３およびＢ４のうち電池Ｂ１が他の電池よりも電圧の高い劣化電池であると仮定する（図９参照）。また、この回路の充電電流をＩｒとする。ここで、劣化電池の電圧Ｖ１をその他の電池の電圧と均衡させるため、それの第１のスイッチング・アセンブリのＭＯＳ−ＦＥＴＳｎ１をＯＦＦにし、その後、それの第２のスイッチング・アセンブリのスイッチＳｎ２のＭＯＳ−ＦＥＴＳｎ２をＯＮにする（図１０のＳ９）。その時、電池Ｂ１の電圧Ｖ１は内部抵抗による電圧低下がゼロになるためＶ１’に下がる。ここで、ｔ１での電圧Ｖ１はＶ１’で一定に保たれる。その後、ｔ２の時のＶ２の値とＶ１がｔ１の時のＶ１（ｔ１）と等しくなった時（Ｓ１０）にそれの第２のスイッチング・アセンブリのＭＯＳ−ＦＥＴＳｎ２をＯＦＦにし、その後、それの第１のスイッチング・アセンブリのＭＯＳ−ＦＥＴＳｎ１をＯＮにして（Ｓ１１）、その時、電圧Ｖ１はこの電圧に復旧する。ｔ２の後、Ｖ１はＶ２と同じ電圧で充電されるため、均衡した充電が可能となる。なお、このバイパス動作はｔ２以降に生じる新たな電圧不均衡に対しても、劣化電池のバイパス動作を何度も繰り返し、電圧を均等化する。
【００６７】
なお、図１０のフローチャートでは、最高電圧の電池を除いて平均電圧Ｖａｖを求め、その平均電圧Ｖａｖと最高電圧との比較を行うことで、電圧の均等化を図っているが、この方法に限定されない。例えば、任意の二つの（隣同士の）電池の電圧を比較して、その差が規定の電圧に達した場合に、電圧の高い電池をバイパスする。電池電圧が低かった電池の電池電圧がその差分だけ上昇した際にバイパスした電池のバイパスを解除することができる。
【００６８】
次に、図１１から図１３を参照して、上記［２］の（２）について具体的に説明する。
【００６９】
図１１は、放電時おける劣化電池をバイパスする電圧均等化回路図であり、図１２は、そのときの時間と電圧の関係を示すグラフ図であり、図１３はそのときの動作を示すフローチャート図である。
【００７０】
図１１において、Ｂ１、Ｂ２、Ｂ３およびＢ４は直列に接続された電池であり、電池Ｂ１が他の電池よりも電圧の低い劣化電池であると仮定する（図１２参照）。また、この回路の放電電流をＩｏとする。ここで、劣化電池の電圧Ｖ１をその他の電池の電圧と均衡させるために、ｔ１でそれの第１のスイッチング・アセンブリのＭＯＳ−ＦＥＴＳ１１をＯＦＦにし、その後、それの第２のスイッチング・アセンブリのＭＯＳ−ＦＥＴＳｎ２をＯＮにする（図１３のＳ１２）。その時、電池Ｂ１は開放となるので電圧Ｖ１は、Ｖ１”に上がる。ここで、ｔ１での電圧Ｖ１は、Ｖ１”で一定に保たれる。その後、ｔ２の時のＶ２の値とＶ１がｔ１の時のＶ１（ｔ１）と等しくなった時（Ｓ１３）に、それの第２のスイッチング・アセンブリのＭＯＳ−ＦＥＴＳｎ２をＯＦＦにし、その後、それの第１のスイッチング・アセンブリのＭＯＳ−ＦＥＴＳｎ１をＯＮにし（Ｓ１４）、その時、電圧Ｖ１はこの電圧に復旧する。ｔ２の後、Ｖ１はＶ２と同じ電圧で放電されるため、均衡した放電が可能となる。なお、このバイパス動作は、ｔ２以降に生じる新たな電圧不均衡に対しても、劣化電池のバイパス動作を何度も繰り返し、電圧を均等化する。
【００７１】
なお、図１３のフローチャートでは、最低電圧の電池を除いて平均電圧Ｖａｖを求め、その平均電圧Ｖａｖと最低電圧との比較を行うことで、電圧の均等化を図っているが、この方法に限定されない。例えば、任意の二つの（隣同士の）電池の電圧を比較して、その差が規定の電圧に達した場合に、電圧の低い電池をバイパスする。電池電圧が高かった電池の電池電圧がその差分だけ降下した際にバイパスした電池のバイパスを解除することができる。
【００７２】
ＭＯＳ−ＦＥＴのボディダイオードを用いる代わりに、外付けのダイオードを用いることができる。外付けのダイオードを用いる場合には、スイッチはＭＯＳ−ＦＥＴ以外のスイッチを用いることができる。そのスイッチとしては、ＭＯＳ−ＦＥＴのような半導体素子の他に、リレー（機械的スイッチ）、ＩＧＢＴ、サイリスタ、ＧＴＯ、パワートランジスタなどを用いることが考えられる。
【００７３】
本実施形態によれば、直列接続した電池に関して、均一充電、均一放電が可能であり、電流の連続性が確保されたバイパス回路が提供できる。
【００７４】
【発明の効果】
本発明の直列接続の電池群の充放電回路によれば、簡単な構成で充放電動作を中断することなく、劣化電池を除外または電圧を均等化させることができる。
【図面の簡単な説明】
【図１】図１は、本発明の直列接続の電池群の充放電回路の一実施形態の構成を示す回路図である。
【図２】図２は、本発明の直列接続の電池群の充放電回路の一実施形態の具体例を示す回路図である。
【図３】図３は、本発明の直列接続の電池群の充放電回路の一実施形態の他の具体例を示す回路図である。
【図４】図４は、本発明の直列接続の電池群の充放電回路の一実施形態の具体例における充電時の動作を示すフローチャートである。
【図５】図５は、本発明の直列接続の電池群の充放電回路の一実施形態の具体例における充電時の劣化電池の除去回路構成図である。
【図６】図６は、本発明の直列接続の電池群の充放電回路の一実施形態の具体例における放電時の動作を示すフローチャートである。
【図７】図７は、本発明の直列接続の電池群の充放電回路の一実施形態の具体例における放電時の劣化電池の除去回路構成図である。
【図８】図８は、本発明の直列接続の電池群の充放電回路の一実施形態の具体例における充電時の劣化電池をバイパスする電圧均等化方法を説明するための回路図である。
【図９】図９は、本発明の直列接続の電池群の充放電回路の一実施形態の具体例における充電時の劣化電池をバイパスする電圧均等化方法が行われるときの時間と電池電圧の関係を示したグラフ図である。
【図１０】図１０は、本発明の直列接続の電池群の充放電回路の一実施形態の具体例における充電時の劣化電池をバイパスする電圧均等化方法の動作を示すフローチャートである。
【図１１】図１１は、本発明の直列接続の電池群の充放電回路の一実施形態の具体例における放電時の劣化電池をバイパスする電圧均等化方法を説明するための回路図である。
【図１２】図１２は、本発明の直列接続の電池群の充放電回路の一実施形態の具体例における放電時の劣化電池をバイパスする電圧均等化方法が行われるときの時間と電池電圧の関係を示したグラフ図である。
【図１３】図１３は、本発明の直列接続の電池群の充放電回路の一実施形態の具体例における放電時の劣化電池をバイパスする電圧均等化方法の動作を示すフローチャートである。
【図１４】図１４は、多数の電池が直列接続されている構成を示す回路図である。
【図１５】図１５は、従来技術の構成を示す回路図である。
【図１６】図１６は、他の従来技術の構成を示す回路図である。
【符号の説明】
Ｂ１電池
Ｂ２電池
Ｂ３電池
Ｂ４電池
Ｂｎ電池
Ｄドレイン
Ｇゲート
Ｄ１１ダイオード
Ｄ１２ダイオード
Ｄｎ１ダイオード
Ｄｎ２ダイオード
Ｉｒ充電電流
Ｉｏ放電電流
Ｓソース
Ｓ１１ＭＯＳ−ＦＥＴ（スイッチ）
Ｓ１２ＭＯＳ−ＦＥＴ（スイッチ）
Ｓ２１ＭＯＳ−ＦＥＴ（スイッチ）
Ｓ２２ＭＯＳ−ＦＥＴ（スイッチ）
Ｓ３１ＭＯＳ−ＦＥＴ（スイッチ）
Ｓ３２ＭＯＳ−ＦＥＴ（スイッチ）
Ｓ４１ＭＯＳ−ＦＥＴ（スイッチ）
Ｓ４２ＭＯＳ−ＦＥＴ（スイッチ）
Ｓｎ１ＭＯＳ−ＦＥＴ（スイッチ）
Ｓｎ２ＭＯＳ−ＦＥＴ（スイッチ）
Ｓ１１１スイッチ
Ｓ１１２スイッチ
Ｓ１ｎ１スイッチ
Ｓ１ｎ２スイッチ
Ｖ１電池電圧
Ｖ２電池電圧
Ｖ３電池電圧
Ｖ４電池電圧[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a charge / discharge circuit for a battery group connected in series, and in particular, used for a backup power source in a factory or a hospital, used for a load leveling device for storing nighttime power and releasing it in the daytime, or mounted on an electric vehicle. Applied to lithium secondary battery.
[0002]
[Prior art]
FIG. 14 shows a battery group in which a large number of batteries are connected in series.
Hereinafter, a case where each of the batteries is a lithium battery will be described as an example.
[0003]
Currently, some lithium batteries under development have a single-cell electromotive force of about 4V. This lithium battery is often used by being connected in series. For example, 4 to 40 lithium batteries may be connected in series.
[0004]
When lithium batteries are used connected in series, a difference in characteristics of each lithium battery becomes a problem. That is, when charging and discharging are repeated, the battery voltage varies due to the difference in the characteristics of the batteries. When the charging / discharging operation is repeated, even if the charging / discharging operation time is the same, a difference appears in the charging voltage or discharging voltage of each battery. In the case of a lithium battery, if it is overcharged, it may lead to an accident, and if it is overdischarged, the capacity of the battery will be lost. For these reasons, strict protection and management are required for overcharge and overdischarge.
[0005]
If the battery voltage of a lithium battery connected in series on a single line varies, the charging must be terminated in accordance with the battery that has reached the charge end voltage first, so the other batteries are completely In other words, the other batteries cannot be completely discharged because it is necessary to terminate the discharge in accordance with the battery that reaches the discharge end voltage first. For this reason, sufficient charge and discharge as a whole battery group connected in series cannot be performed.
[0006]
As a technique for suppressing this variation, there is an example in which a Zener diode as shown in FIG. 15 is used (see Japanese Patent Laid-Open No. 11-332115). In the technology described in this publication, an emphasis is placed on preventing the charging voltage from becoming excessive.
However, Zener diodes are not suitable for large currents. The Zener diode is used at about 1 to 3 A, and cannot be used at a level exceeding 4 A.
[0007]
Lithium batteries connected in series are used, for example, for power load leveling for storing nighttime power and releasing it during the daytime. In this type of application, it is assumed that a current of 10 to 20 A can be handled. Therefore, Zener diodes (general-purpose products) are not suitable for the above applications.
[0008]
Therefore, as shown in FIG. 16, a circuit for bypassing the current has been studied. Regarding the battery B1, the switch S111 is turned on and the switch S112 is turned off during normal operation, and the switch S111 is turned off and the switch S112 is turned on during bypass.
[0009]
According to this circuit configuration, if the capacitance of the switches S111, S112,... S1n1, S1n2 is increased, it can be applied to a large current. However, when the switches are switched, for example, when the battery B1 is bypassed, it is necessary to provide a period in which both the switches S111 and S112 are OFF, such as turning off the switch S111 and then turning on the switch S112 ( When both switches S111 and S112 are ON, the battery B1 is short-circuited).
[0010]
However, during the period when both the switches S111 and S112 are OFF, since there is no route for current to flow, an excessive surge voltage is generated at the switch S111 from the moment when the switch S111 that has been ON is switched OFF. There was a fear. In this case, depending on the situation, it is a factor that hurts the battery.
[0011]
  As a preventive measure, a method of preventing the generation of a surge voltage by stopping the supply of the charging current during a period when both the switches S111 and S112 are OFF (for example, 100 μsec) can be considered.However, in order to prevent the generation of a surge voltage as in the case of this charging, if it is assumed that no discharge current flows during a period when both switches S111 and S112 are OFF during discharging, current cannot be taken during that time. Depending on the conditions on the load side, there is a case where it is always necessary to take out the current. In this case, it is necessary to avoid a situation where the current is not output, even temporarily.
[0012]
  As another preventive measure, it is conceivable to prevent a surge voltage from being generated by providing a surge absorbing circuit (for example, a snubber circuit). However, as the surge absorbing circuit is provided, the loss increases, and the capacity of the battery cannot be fully utilized during charging / discharging. Therefore, it is desirable to avoid the use of surge absorbing circuits.
[0013]
  Non-Patent Document 1 discloses removal of a deteriorated battery in a series connection system. In the circuit of Non-Patent Document 1, a switch including a parallel diode is connected in series with a battery, and a parallel switch is further connected in parallel with the series connection of the battery and the switch. When supplying power to a load, the switch is closed and the diode is shorted. When the battery is charged, the switch is opened and the diode becomes conductive, and charging current is supplied through the diode. When the battery is removed as a deteriorated battery, the parallel switch is closed.
[Non-Patent Document 1]
K. Harada, S. Taniguchi, K. Adachi, G. Ariyoshi, Y. Kawata, "On the Removing of a Less Quality Battery from a Series-Connected System", 22nd International Telecommunications Energy Conference INTELEC 2000, (2000.09.10) , p.761-764
[0014]
[Problems to be solved by the invention]
An object of the present invention is to provide a charge / discharge circuit for a series-connected battery group that can eliminate a deteriorated battery or equalize a voltage without interrupting a charge / discharge operation with a simple configuration.
[0015]
Another object of the present invention is to provide a charge / discharge circuit for a series-connected battery group that can eliminate a deteriorated battery or equalize voltage without interrupting the charge / discharge operation with a simple configuration. .
[0016]
[Means for Solving the Problems]
[Means for Solving the Problems] will be described below using the numbers and symbols used in [Embodiments of the Invention]. These numbers and symbols are added to clarify the correspondence between the description of [Claims] and the description of [Mode for carrying out the invention]. It should not be used to interpret the technical scope of the described invention.
[0017]
The charge / discharge circuit of the battery group connected in series according to the present invention includes a first diode (Dn1) arranged in a forward direction with respect to a charging current (Ir) and a first diode connected in parallel to the first diode (Dn1). A battery group in which a plurality of series units each including a first switching assembly including a switch (Sn1) and a battery (Bn) are connected in series, and arranged in a direction opposite to the charging current (Ir) A second switching assembly connected in parallel to the series unit; and a second switch (Sn2) connected in parallel to the second diode (Dn2) and the second diode (Dn2),
When the battery voltage of the first battery in series (B1) becomes equal to or higher than a predetermined value during charging, the first switch (S11) of the first battery in series is turned OFF, and then the first switch And a control unit that turns on the second switch (S12) of the second switching assembly connected in parallel to the single series unit to bypass the battery (B1) of the first single series unit.
[0018]
In the charging / discharging circuit of the battery group connected in series according to the present invention, the control unit is configured to output the second series when the battery voltage of the second battery (B1) in the series alone becomes a predetermined value or less during discharging. The single first switch (S11) is turned off, and then the second switch (S12) of the second switching assembly connected in parallel to the second single series unit is turned on and the second switch is turned on. The battery (B1) in series is bypassed.
[0019]
The charging / discharging circuit of the series-connected battery group of the present invention includes a first MOS-FET (Sn1) arranged so that the first body diode is formed in the forward direction with respect to the charging current (Ir). A battery group in which a plurality of single series connected to the battery (Bn) are connected in series, and the second body diode is formed in the opposite direction with respect to the charging current (Ir). The first series when the battery voltage of the second MOS-FET (Sn2) connected in parallel to the single series and the battery (B1) of the first single series at the time of charging exceeds a predetermined value. The single first MOS-FET (S11) is turned off, and then the second MOS-FET (S12) connected in parallel to the first series single is turned on and the first series single is turned on. To bypass the battery (B1) And a control unit.
[0020]
In the charging / discharging circuit of the battery group connected in series according to the present invention, the control unit is configured to output the second series when the battery voltage of the second battery (B1) in the series alone becomes a predetermined value or less during discharging. The single first MOS-FET (S11) is turned OFF, and then the second MOS-FET (S12) connected in parallel to the second serial single is turned ON to turn the second serial single The battery (B1) is bypassed.
[0021]
In the charging / discharging circuit of the battery group connected in series according to the present invention, the operation reference when the control unit bypasses the battery (B1) is that the battery voltage of each battery (Bn) of the battery group is a predetermined value. It is determined by whether or not it is reached.
[0022]
In the charging / discharging circuit of the battery group connected in series according to the present invention, the operation reference when the control unit bypasses the battery (B1) is determined by the voltage difference between the two batteries (Bn) included in the battery group. Is done.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
One embodiment of the invention is described.
[0024]
With reference to FIG. 1, a bypass circuit of a lithium secondary battery will be described as an embodiment of a charge / discharge circuit of a series-connected battery group of the present invention.
[0025]
When batteries are used for power storage and electric vehicles, it is necessary to connect a plurality of batteries in series and use them as an assembled battery in order to increase electricity storage capacity. However, in actuality, when batteries are connected in series, overcharge or overdischarge of the battery occurs during charging / discharging due to mixing of deteriorated batteries, variations of individual batteries, or the like. In the present invention, in order to solve these problems, the following method is adopted.
[0026]
As shown in FIG. 1, diodes D11, D12,... Dn1, Dn2 are provided in parallel with the switches S11, S12,. The diodes D11,... Dn1 are arranged in the forward direction with respect to the charging current. The diodes D12,... Dn2 are arranged in the forward direction with respect to the discharge current.
[0027]
In FIG. 1, a battery group is formed by connecting batteries Bn in series via a first switching assembly including a diode Dn1 arranged in the forward direction with respect to the charging current and a switch Sn1 connected in parallel thereto. It is composed.
The second switching assembly is connected in parallel to a single unit formed by connecting the first switching assembly and the battery Bn, and in parallel with the diode Dn2 disposed in the opposite direction to the charging current. And a connected switch Sn2.
[0028]
First, an operation for bypassing the battery B1 during charging will be described.
[0029]
First, in normal times when bypass is not performed, the switch S11 is ON, and the charging current flows to the battery B1 via the switch S11.
[0030]
Next, when the battery voltage of the battery B1 becomes equal to or higher than a predetermined voltage, the switch S11 is turned off. When the switch S11 is turned OFF, the charging current flows to the battery B1 via the diode D11 (at this time, the charging to the battery B1 is continued).
[0031]
Next, when the switch S12 is turned on, since the on-voltage of the switch S12 is smaller than the turn-on voltage of the diode D11, the charging current flows through the switch S12, and the battery B1 is bypassed. At this time, the diode D11 is reverse-biased by the battery B1, and the conduction of the diode D11 is turned off.
[0032]
Next, an operation for bypassing the battery B1 during discharging will be described.
[0033]
First, in normal times when bypass is not performed, the switch S11 is ON, and the discharge current flows from the positive terminal side of the battery B1 to an external load (not shown) via the switch S11.
[0034]
Next, when the battery voltage of the battery B1 becomes equal to or lower than a predetermined voltage, the switch S11 is turned off. When the switch S11 is turned OFF, the discharge current flows to the external load via the diode D12. Thereby, even if the battery B1 is bypassed during discharging, a current path for the discharging current is secured.
[0035]
The diode D12 has a high turn-on voltage, and has a large loss when a discharge current flows through the diode D12 for a long time. This becomes a problem when the discharge current is a large current (for example, about 20 A). Therefore, the switch S12 is turned on and a discharge current is passed through the switch S12. As a result, the loss is effectively suppressed as compared with the case of passing through the diode D12.
[0036]
From the above operation, a current path while bypassing the battery B1 during charging and discharging is always ensured, and current continuity is maintained. Therefore, a surge absorption circuit is not necessary, and it is not necessary to stop the supply of charging current.
[0037]
FIG. 2 shows a specific embodiment.
In FIG. 2, members having the same functions as those in FIG.
[0038]
As shown in FIG. 2, the switch unit is composed of a MOS-FET. The MOS-FET has a structure in which a diode portion (this is referred to as a body diode) is formed from the source to the drain, so that the circuit configuration is simplified when it is used. The body diode has the same current capacity as the MOS-FET.
[0039]
The MOS-FETs S12 and Sn2 function as bypass switches.
Further, when the MOS-FETs S11, S12,... Sn1, Sn2 are turned on, the direction of current flow may be from the drain to the source or from the source to the drain, and thus functions as a bidirectional switch. be able to. In FIG. 2, one MOS-FET is provided, but in the case of a large current, the MOS-FET can be provided in multiple stages in parallel.
[0040]
Next, the operation of this embodiment will be described.
[0041]
First, an operation for bypassing the battery B1 during charging will be described.
[0042]
First, in a normal time when bypass is not performed, a bias voltage is applied to the gate of the MOS-FET S11, the MOS-FET S11 is turned on, and the charging current is supplied to the battery B1 via the MOS-FET S11. Flowing.
[0043]
Next, when the battery voltage of the battery B1 becomes equal to or higher than a predetermined voltage (for example, 4, 2V), a reverse bias voltage is applied to the gate of the MOS-FET S11 to turn off the MOS-FET S11. When the MOS-FET S11 is turned off, the charging current flows to the battery B1 via the body diode of the MOS-FET S11 (at this time, the charging to the battery B1 is continued).
[0044]
Next, when a predetermined voltage is applied to the gate of the MOS-FET S12 and the MOS-FET S12 is turned on, the on-voltage of the MOS-FET S12 is smaller than the turn-on voltage of the body diode of the MOS-FET S11. The charging current flows through the MOS-FET S12, and the battery B1 is bypassed.
[0045]
Next, an operation for bypassing the battery B1 during discharging will be described.
[0046]
First, during normal times when bypass is not performed, a bias voltage is applied to the gate of the MOS-FET S11, the MOS-FET S11 is turned on, and the discharge current is supplied from the positive terminal side of the battery B1 to the MOS-FET S11. To an external load (not shown).
[0047]
Next, when the battery voltage of the battery B1 becomes a predetermined voltage (for example, 3, 3V) or less, a reverse bias voltage is applied to the gate of the MOS-FET S11 to turn off the MOS-FET S11. When the MOS-FET S11 is turned off, the discharge current flows to the external load via the body diode of the MOS-FET S12. Thereby, even if the battery B1 is bypassed during discharging, a current path for the discharging current is secured.
[0048]
The body diode of the MOS-FET S12 has a high turn-on voltage, and has a large loss when a discharge current flows through the body diode for a long time. Therefore, a bias voltage is applied to the gate of the MOS-FET S12, the MOS-FET S12 is turned on, and a discharge current flows through the MOS-FET S12. Thereby, the loss of the discharge current is effectively suppressed as compared with the case where the body diode of the MOS-FET S12 is used.
[0049]
From the above operation, a current path while bypassing the battery B1 during charging and discharging is always ensured, and current continuity is maintained. Therefore, a surge absorption circuit is not necessary, and it is not necessary to stop the supply of charging current.
[0050]
Since the turn-on voltage of the body diode of the MOS-FET is generally high, if the current flows through the body diode for a predetermined time or more, the MOS-FET may be damaged due to heat generation or the like. In this embodiment, the charging current flows through the body diode of the MOS-FET S11 is only a short time required for switching from the MOS-FET S11 being turned off until the MOS-FET S12 is turned on. (For example, several hundred μsec). Similarly, the time during which the discharge current flows through the body diode of the MOS-FET S12 is only a short time required for switching from when the MOS-FET S11 is turned off until the MOS-FET S12 is turned on (for example, , Several hundred μsec). Therefore, in this embodiment, there is no possibility that the MOS-FETs S11 and S12 are damaged by the current flowing through the body diode.
[0051]
In this way, in this embodiment, the current flows through the body diode for a short time, and there is no disadvantage associated with its use, so there is no need to use a diode (individual element) other than the body diode.
[0052]
In FIG. 2, the switch portion is on the positive terminal side of the battery, but there is no problem if the switch portion is on the negative terminal side of the battery as shown in FIG.
[0053]
The bypass operation can be performed as follows. A description will be given separately for charging and discharging. There are two methods (1) and (2) for each time point of charge and discharge.
[0054]
[1] When charging
(1) Each battery voltage is measured, and when the voltage reaches a predetermined value, the battery is bypassed. The bypass is released when discharging.
(2) Each battery voltage is measured, two battery voltages are compared, and when the difference reaches a specified voltage, a battery having a high voltage is bypassed. When the battery voltage of the battery having a low battery voltage increases by the difference, the bypass of the bypassed battery is released.
[0055]
[2] During discharge
(1) Each battery voltage is measured, and when the voltage reaches a predetermined value, the battery is bypassed. The bypass is released when charging.
(2) Each battery voltage is measured, two battery voltages are compared, and when the difference reaches a specified voltage, a battery having a low voltage is bypassed. When the battery voltage of the battery having a high battery voltage drops by the difference, the bypass of the bypassed battery is released.
[0056]
Next, (1) of the above [1] will be specifically described with reference to FIG. 4 and FIG. Here, the battery to be bypassed is described as being removed as a deteriorated battery. However, it goes without saying that even a battery that should be bypassed may be used as it is without being removed as a deteriorated battery.
[0057]
FIG. 4 is an operation flow diagram during charging when four batteries are used, and FIG. 5 is a configuration diagram of a circuit for removing a deteriorated battery during charging.
[0058]
In FIG. 5, in the initial state at the time of charging, the MOS-FET Sn1 of the first switching assembly is turned on, and the MOS-FET Sn2 of the switch Sn2 of the second switching assembly is turned off.
[0059]
When charging from the charging device, the MOS-FET Sn1 of the first switching assembly is turned on, a charging current is passed through the MOS-FET Sn1, and the voltage of each battery Bn is monitored (S1). As a result of the monitoring, when a deteriorated battery showing an abnormal voltage increase is detected (S2), the MOS-FET Sn1 of the first switching assembly is turned off, and then the switch of the second switching assembly is turned off. When the MOS-FET Sn2 of Sn2 is turned ON (S3), the above-mentioned deteriorated battery is excluded without stopping the system by bypassing the charging current, and then the deteriorated battery is replaced with a new battery and all the batteries have the same voltage. The MOS-FET Sn2 of the second switching assembly is turned off, and then the MOS-FET Sn1 of the first switching assembly is turned on (S4) to return to the normal state.
[0060]
Next, (1) of the above [2] will be described in detail with reference to FIGS. Here, it is assumed that the battery to be bypassed is removed as a deteriorated battery. However, it goes without saying that even a battery to be bypassed may be used as it is without being removed as a deteriorated battery.
[0061]
FIG. 6 is an operation flow diagram (removal circuit) at the time of discharging when four batteries are used, and FIG. 7 is a configuration diagram of a circuit for removing a deteriorated battery at the time of discharging.
[0062]
In FIG. 7, in the initial state at the time of discharge, the MOS-FET Sn1 of the first switching assembly is turned on, and the MOS-FET Sn2 of the switch Sn2 of the second switching assembly is turned off.
[0063]
At the time of discharging to the load, the MOS-FET Sn1 of the first switching assembly is turned on, a discharge current is passed through the MOS-FET Sn1, and the voltage of each battery Bn is monitored (S5). As a result of the monitoring, when a deteriorated battery showing an abnormal voltage drop is detected (S6), the MOS-FET Sn1 of the first switching assembly is turned off, and then the switch of the second switching assembly is turned off. When the MOS-FET Sn2 of Sn2 is turned on (S7), the above-mentioned deteriorated battery is excluded without stopping the system by bypassing the discharge current, and then the deteriorated battery is replaced with a new battery, and all the batteries have the same voltage. The MOS-FET Sn2 of the second switching assembly is turned off, and then the MOS-FET Sn1 of the first switching assembly is turned on (S8) to return to the normal state.
[0064]
Next, with reference to FIG. 8 to FIG. 10, (2) of the above [1] will be specifically described.
[0065]
FIG. 8 is a voltage equalization circuit diagram for bypassing the deteriorated battery during charging when four batteries are used for the equalization operation of the deteriorated battery, and FIG. 9 is a graph showing the relationship between time and voltage at that time. FIG. 10 is a flowchart showing the operation at that time.
[0066]
In FIG. 8, it is assumed that the battery B1 is a deteriorated battery having a higher voltage than the other batteries among the batteries B1, B2, B3, and B4 connected in series (see FIG. 9). The charging current of this circuit is Ir. Here, in order to balance the voltage V1 of the deteriorated battery with the voltages of the other batteries, the MOS-FET Sn1 of its first switching assembly is turned off and then the switch Sn2 of its second switching assembly is turned off. The MOS-FET Sn2 is turned on (S9 in FIG. 10). At that time, the voltage V1 of the battery B1 drops to V1 'because the voltage drop due to the internal resistance becomes zero. Here, the voltage V1 at t1 is kept constant at V1 '. After that, when the value of V2 at t2 and V1 equal to V1 (t1) at t1 (S10), the MOS-FET Sn2 of its second switching assembly is turned off, and then The MOS-FET Sn1 of the first switching assembly is turned on (S11), and then the voltage V1 is restored to this voltage. After t2, V1 is charged with the same voltage as V2, so that balanced charging is possible. This bypass operation equalizes the voltage by repeating the bypass operation of the deteriorated battery many times even for a new voltage imbalance occurring after t2.
[0067]
In the flowchart of FIG. 10, the average voltage Vav is obtained excluding the battery having the highest voltage, and the average voltage Vav is compared with the highest voltage to equalize the voltage. However, the method is limited to this method. Not. For example, the voltages of two arbitrary (adjacent) batteries are compared, and when the difference reaches a specified voltage, a battery having a high voltage is bypassed. When the battery voltage of the battery having a low battery voltage increases by the difference, the bypass of the battery bypassed can be canceled.
[0068]
Next, with reference to FIG. 11 to FIG. 13, (2) of [2] will be specifically described.
[0069]
FIG. 11 is a voltage equalization circuit diagram for bypassing a deteriorated battery during discharging, FIG. 12 is a graph showing the relationship between time and voltage at that time, and FIG. 13 is a flowchart showing the operation at that time. It is.
[0070]
In FIG. 11, B1, B2, B3, and B4 are batteries connected in series, and it is assumed that the battery B1 is a deteriorated battery having a lower voltage than other batteries (see FIG. 12). The discharge current of this circuit is Io. Here, in order to balance the voltage V1 of the deteriorated battery with the voltages of the other batteries, the MOS-FET S11 of its first switching assembly is turned off at t1, and then the second switching assembly of its second switching assembly. The MOS-FET Sn2 is turned on (S12 in FIG. 13). At that time, since the battery B1 is opened, the voltage V1 rises to V1 ″. Here, the voltage V1 at t1 is kept constant at V1 ″. After that, when the value of V2 at t2 and V1 equal to V1 (t1) at t1 (S13), the MOS-FET Sn2 of its second switching assembly is turned off, and then The MOS-FET Sn1 of the first switching assembly is turned on (S14), and then the voltage V1 is restored to this voltage. After t2, V1 is discharged at the same voltage as V2, so a balanced discharge is possible. This bypass operation equalizes the voltage by repeating the bypass operation of the deteriorated battery many times even for a new voltage imbalance occurring after t2.
[0071]
In the flowchart of FIG. 13, the average voltage Vav is obtained except for the battery having the lowest voltage, and the average voltage Vav is compared with the lowest voltage to equalize the voltage. However, the method is limited to this method. Not. For example, the voltages of any two (adjacent) batteries are compared, and if the difference reaches a specified voltage, the battery with the lower voltage is bypassed. The bypass of the battery bypassed when the battery voltage of the battery having a high battery voltage drops by the difference can be canceled.
[0072]
Instead of using the body diode of the MOS-FET, an external diode can be used. When an external diode is used, a switch other than a MOS-FET can be used as the switch. As the switch, in addition to a semiconductor element such as a MOS-FET, a relay (mechanical switch), IGBT, thyristor, GTO, power transistor, or the like may be used.
[0073]
According to this embodiment, it is possible to provide a bypass circuit in which uniform charging and uniform discharging are possible for batteries connected in series, and current continuity is ensured.
[0074]
【The invention's effect】
According to the charging / discharging circuit of the battery group connected in series according to the present invention, it is possible to exclude the deteriorated battery or equalize the voltage without interrupting the charging / discharging operation with a simple configuration.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a configuration of an embodiment of a charge / discharge circuit of a battery group connected in series according to the present invention.
FIG. 2 is a circuit diagram showing a specific example of an embodiment of a charge / discharge circuit of a series-connected battery group of the present invention.
FIG. 3 is a circuit diagram showing another specific example of the embodiment of the charge / discharge circuit of the battery group connected in series according to the present invention.
FIG. 4 is a flowchart showing an operation at the time of charging in a specific example of the embodiment of the charging / discharging circuit of the battery group connected in series according to the present invention.
FIG. 5 is a circuit diagram of a circuit for removing a deteriorated battery during charging in a specific example of an embodiment of a charging / discharging circuit of a series-connected battery group of the present invention.
FIG. 6 is a flowchart showing an operation at the time of discharging in a specific example of the embodiment of the charging / discharging circuit of the series-connected battery group of the present invention.
FIG. 7 is a circuit diagram of a circuit for removing a deteriorated battery during discharge in a specific example of an embodiment of a charge / discharge circuit of a battery group connected in series according to the present invention.
FIG. 8 is a circuit diagram for explaining a voltage equalization method for bypassing a deteriorated battery during charging in a specific example of an embodiment of a charging / discharging circuit of a series-connected battery group of the present invention.
FIG. 9 is a graph showing time and battery voltage when a voltage equalization method for bypassing a deteriorated battery during charging is performed in a specific example of an embodiment of a charge / discharge circuit of a series-connected battery group of the present invention; It is the graph which showed the relationship.
FIG. 10 is a flowchart showing an operation of a voltage equalization method for bypassing a deteriorated battery during charging in a specific example of an embodiment of a charging / discharging circuit of a series-connected battery group of the present invention.
FIG. 11 is a circuit diagram for explaining a voltage equalization method for bypassing a deteriorated battery at the time of discharge in a specific example of the charge / discharge circuit of the battery group connected in series according to the present invention.
FIG. 12 is a graph showing time and battery voltage when a voltage equalization method for bypassing a deteriorated battery during discharge is performed in a specific example of an embodiment of a charge / discharge circuit of a series-connected battery group of the present invention; It is the graph which showed the relationship.
FIG. 13 is a flowchart showing an operation of a voltage equalization method for bypassing a deteriorated battery at the time of discharge in a specific example of the charge / discharge circuit of the series-connected battery group of the present invention.
FIG. 14 is a circuit diagram showing a configuration in which a large number of batteries are connected in series.
FIG. 15 is a circuit diagram showing a configuration of a prior art.
FIG. 16 is a circuit diagram showing a configuration of another prior art.
[Explanation of symbols]
B1 battery
B2 battery
B3 battery
B4 battery
Bn battery
D drain
G Gate
D11 Diode
D12 Diode
Dn1 diode
Dn2 diode
Ir charging current
Io discharge current
S source
S11 MOS-FET (Switch)
S12 MOS-FET (Switch)
S21 MOS-FET (Switch)
S22 MOS-FET (Switch)
S31 MOS-FET (Switch)
S32 MOS-FET (Switch)
S41 MOS-FET (Switch)
S42 MOS-FET (Switch)
Sn1 MOS-FET (switch)
Sn2 MOS-FET (switch)
S111 switch
S112 switch
S1n1 switch
S1n2 switch
V1 battery voltage
V2 battery voltage
V3 battery voltage
V4 battery voltage

Claims

A plurality of series units each including a first switching assembly including a first diode disposed in a forward direction with respect to a charging current and a first switch connected in parallel to the first diode and a battery. A group of batteries connected in series;
A second switching assembly comprising a second diode disposed in a reverse direction to the charging current and a second switch connected in parallel to the second diode, and connected in parallel to the series unit;
When the battery voltage of the first series single battery is less than a first predetermined value during charging, the first switch of the first single series is turned on and in parallel with the first single series. and said second switch connected to said second switching assembly to OFF, said when the battery voltage of the battery of the first series alone during charge becomes the first predetermined value or more Turn off the first switch of the first series unit, and then turn on the second switch of the second switching assembly connected in parallel to the first series unit. A control unit for bypassing the battery ,
When both the first switch of the first series unit and the second switch of the second switching assembly connected in parallel to the first series unit are turned off, the first series unit Providing a path through which the first diode of the first switching assembly is energized to supply the charging current to the first series of cells;
Thereafter, when the second switch of the second switching assembly is turned ON, the first diode is reverse-biased by the battery in the first series unit, thereby the first unit in the series. A charging / discharging circuit of a series-connected battery group in which conduction of the first diode of the first switching assembly is automatically turned off .

In the charge / discharge circuit of the battery group connected in series according to claim 1,
The control unit turns on the first switch of the second series unit and turns on the second switch when the battery voltage of the second series unit battery exceeds a second predetermined value during discharging. said second switch of the second switching assembly connected in parallel with the series itself is OFF, the second battery voltage of the battery series alone becomes equal to or less than the second predetermined value during discharge said second series single first switch to OFF when subsequently said oN the second switch of the second of the series itself is connected in parallel a second switching assembly first A charge / discharge circuit for a series-connected battery group that bypasses the batteries of two series units.

A battery group in which a plurality of single units formed by connecting a first MOS-FET and a battery are arranged in series so that the first body diode is formed in a forward direction with respect to a charging current;
A second MOS-FET arranged so that the second body diode is formed in the opposite direction to the charging current and connected in parallel to the single unit;
When the battery voltage of the battery in the first series unit is less than a first predetermined value during charging, the first MOS-FET in the first series unit is turned on and the first series unit is turned on. OFF the connected second MOS-FET in parallel with said first series when the battery voltage of the battery of the first series alone during charge becomes the first predetermined value or more The single first MOS-FET is turned off, and then the second MOS-FET connected in parallel to the first series single is turned on to bypass the first series single battery. and a control unit,
When both the first MOS-FET of the first series unit and the second MOS-FET connected in parallel to the first series unit are turned off, the first series unit of the first MOS-FET is turned off. Providing a path through which the first body diode of the first MOS-FET is turned on to supply the charging current to the first battery in series;
Thereafter, when the second MOS-FET is turned on, the on-voltage of the second MOS-FET is smaller than the turn-on voltage of the first body diode, so that the first serial unit first A series-connected battery charging / discharging circuit in which the conduction of the first body diode of the MOS-FET is automatically turned off .

In the charge / discharge circuit of the battery group connected in series according to claim 3 ,
The controller turns on the first MOS-FET of the second series unit when the battery voltage of the second series unit battery exceeds a second predetermined value at the time of discharge, when the battery voltage of said battery of said second series alone becomes equal to or less than the second predetermined value to OFF said second series single said first MOS-FET, then the second A charge / discharge circuit for a series-connected battery group that turns on the second MOS-FET connected in parallel to a single series unit to bypass the second series single unit battery.

A plurality of series units each including a first switching assembly including a first diode disposed in a forward direction with respect to a charging current and a first switch connected in parallel to the first diode and a battery. A group of batteries connected in series;
A second switching assembly comprising a second diode disposed in a reverse direction to the charging current and a second switch connected in parallel to the second diode, and connected in parallel to the series unit;
With control
With
At the time of charging, the control unit defines a difference between the battery voltage of the first series unit battery and the battery voltage of the second series unit battery adjacent to the first series unit. The first switch of the first series unit and the second series unit are turned on and the first series unit and the second series unit are connected in parallel. The second switch of the second switching assembly is turned OFF, and the difference between the battery voltage of the first series unit battery and the battery voltage of the second series unit battery becomes the specified voltage. In the case of reaching, the first switch of one of the first series unit and the second series unit having the higher battery voltage of the battery is turned off, and then the first series unit is parallel to the one series unit. Connected to And ON the second switch of the second switching assembly to bypass the battery series single said one,
When both the first switch of the one series unit and the second switch of the second switching assembly connected in parallel to the one series unit are turned off, the first unit of the one series unit is turned off. Providing a path through which the first diode of one switching assembly conducts to supply the charging current to the one unit battery in series;
Thereafter, when the second switch of the second switching assembly of the one series unit is turned on, the first diode is reverse-biased by the battery of the one series unit, thereby The conduction of the first diode of the first switching assembly in a series unit is automatically turned off.
Charge / discharge circuit for series connected battery group.

A battery group in which a plurality of single units formed by connecting a first MOS-FET and a battery are arranged in series so that the first body diode is formed in a forward direction with respect to a charging current;
  The second body diode is arranged in the opposite direction to the charging current. A second MOS-FET connected in parallel to the series unit;
  With control
With
  At the time of charging, the control unit is configured such that a difference between the battery voltage of the first series unit battery and the battery voltage of the second series unit battery adjacent to the first series unit is When the specified voltage is not reached, the first MOS-FET of the first series unit and the second series unit are turned on and connected in parallel to the first series unit and the second series unit. The second MOS-FET thus turned off is turned OFF, and the difference between the battery voltage of the first series unit battery and the battery voltage of the second series unit battery reaches the specified voltage. In this case, the first MOS-FET of one of the first series unit and the second series unit having the higher battery voltage of the battery is turned off, and then the one series unit is turned off. Connected in parallel to the first And the MOS-FET is turned ON to bypass the battery series single said one,
  When both of the first single MOS-FET in series and the second MOS-FET connected in parallel to the single single series are turned off, the first single single MOSFET is turned off. Providing a path through which the first body diode of the MOS-FET is conducted to supply the charging current to the one battery in series;
  Thereafter, when the second MOS-FET of the one series unit is turned on, the on-voltage of the second MOS-FET is smaller than the turn-on voltage of the first body diode. The conduction of the first body diode of the first MOS-FET in series is automatically turned off.
  Charge / discharge circuit for series connected battery group.

A plurality of series units each including a first switching assembly including a first diode disposed in a forward direction with respect to a charging current and a first switch connected in parallel to the first diode and a battery. A group of batteries connected in series;
A second switching assembly connected in parallel to the series unit, comprising: a second diode disposed in a direction opposite to the charging current; and a second switch connected in parallel to the second diode;
A method for charging a series-connected battery group comprising:
When the battery voltage of the first series unit battery is less than a predetermined value during charging, the first switch of the first series unit is turned on and connected in parallel to the first series unit Turning off the second switch of the second switching assembly
When the battery voltage of the first series unit battery becomes equal to or higher than the predetermined value during charging, the first switch unit of the first series unit is turned off, and then the first series unit unit is turned off. Turning on the second switch of the second switching assembly connected in parallel to bypass the battery in the first series unit;
With
When both the first switch of the first series unit and the second switch of the second switching assembly connected in parallel to the first series unit are turned off, the first series unit Providing a path through which the first diode of the first switching assembly is energized to supply the charging current to the first series of cells;
Thereafter, when the second switch of the second switching assembly is turned ON, the first diode is reverse-biased by the battery in the first series unit, thereby the first unit in the series. The conduction of the first diode of the first switching assembly is automatically turned off.
Charging method.

Arranged so that the first body diode is formed in the forward direction with respect to the charging current A battery group in which a plurality of single series units each formed by connecting a first MOS-FET and a battery are connected in series;
  A second MOS-FET arranged so that the second body diode is formed in the opposite direction to the charging current, and connected in parallel to the single unit;
A method for charging a series-connected battery group comprising:
  When the battery voltage of the first battery in series is less than a first predetermined value during charging, the first MOS-FET in the first series alone is turned on and the first series is turned on. Turning off the second MOS-FET connected in parallel to a single unit;
  When the battery voltage of the first series unit battery becomes equal to or higher than the first predetermined value at the time of charging, the first series unit first MOS-FET is turned off, and then the first series unit unit is turned off. Turning on the second MOS-FET connected in parallel to the series unit and bypassing the battery of the first series unit;
With
  When both the first MOS-FET of the first series unit and the second MOS-FET connected in parallel to the first series unit are turned off, the first series unit of the first series unit is turned off. The first body diode of the first MOS-FET is turned on to provide a path for supplying the charging current to the first battery in series.
  Thereafter, when the second MOS-FET is turned on, the on-voltage of the second MOS-FET is smaller than the turn-on voltage of the first body diode, so that the first serial unit first The first body diode of the MOS-FET is automatically turned off.
  Charging method.

A plurality of series units each including a first switching assembly including a first diode disposed in a forward direction with respect to a charging current and a first switch connected in parallel to the first diode and a battery. A group of batteries connected in series;
A second switching assembly connected in parallel to the series unit, comprising: a second diode disposed in a direction opposite to the charging current; and a second switch connected in parallel to the second diode;
A method for charging a series-connected battery group comprising:
When the difference between the battery voltage of the first battery in series and the battery voltage of the second battery in series adjacent to the first battery does not reach a specified voltage during charging. The first switching unit of the first series unit and the second series unit is turned on, and the second switching assembly is connected in parallel to the first series unit and the second series unit. Turning off the second switch of
When the difference between the battery voltage of the first series unit battery and the battery voltage of the second series unit battery reaches the specified voltage during charging, the first series unit And the second switching assembly connected to the one series unit in parallel after turning off the first switch of the series unit having one of the second series units having the higher battery voltage. Turning on the second switch of the battery and bypassing the one battery in series.
With
When both the first switch of the one series unit and the second switch of the second switching assembly connected in parallel to the one series unit are turned off, the first unit of the one series unit is turned off. Providing a path through which the first diode of one switching assembly is energized to supply the charging current to the one unit battery in series;
Thereafter, when the second switch of the second switching assembly of the one series unit is turned on, the first diode is reverse-biased by the battery of the one series unit, thereby The conduction of the first diode of the first switching assembly in a series unit is automatically turned off.
Charging method .

A battery group in which a plurality of single units formed by connecting a first MOS-FET and a battery are arranged in series so that the first body diode is formed in a forward direction with respect to a charging current;
  A second MOS-FET arranged so that the second body diode is formed in the opposite direction to the charging current, and connected in parallel to the single unit;
A method for charging a series-connected battery group comprising:
  At the time of charging, the difference between the battery voltage of the first battery in series and the battery voltage of the second battery in series adjacent to the first battery reaches a specified voltage. If not, the first MOS-FET of the first series unit and the second series unit are turned on, and the first series unit and the second series unit are connected in parallel. Turning off the second MOS-FET;
  When the difference between the battery voltage of the first series unit battery and the battery voltage of the second series unit battery reaches the specified voltage during charging, the first series unit And turn off the first MOS-FET of the one series unit having the higher battery voltage of the second series unit, and then connect the second unit connected in parallel to the one series unit. Turning on the MOS-FET to bypass the one battery in series
With
  When both of the first single MOS-FET in series and the second MOS-FET connected in parallel to the single single series are turned off, the first single single MOSFET is turned off. Providing a path through which the first body diode of the MOS-FET is conducted to supply the charging current to the one battery in series;
  Thereafter, when the second MOS-FET of the one series unit is turned on, the ON voltage of the second MOS-FET is smaller than the turn-on voltage of the first body diode, so that the one of the series MOS transistors is turned on. The conduction of the first body diode of the single first MOS-FET is automatically turned off.
  Charging method.