JP4499966B2 - Secondary battery charging circuit - Google Patents

Secondary battery charging circuit Download PDF

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Publication number
JP4499966B2
JP4499966B2 JP2001279823A JP2001279823A JP4499966B2 JP 4499966 B2 JP4499966 B2 JP 4499966B2 JP 2001279823 A JP2001279823 A JP 2001279823A JP 2001279823 A JP2001279823 A JP 2001279823A JP 4499966 B2 JP4499966 B2 JP 4499966B2
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voltage
constant voltage
charging
secondary battery
circuit
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JP2003087990A (en
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淳二 西田
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Ricoh Co Ltd
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Ricoh Co Ltd
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Priority to JP2001279823A priority Critical patent/JP4499966B2/en
Application filed by Ricoh Co Ltd filed Critical Ricoh Co Ltd
Priority to KR1020057022622A priority patent/KR100611583B1/en
Priority to CN2007101547773A priority patent/CN101123365B/en
Priority to CN200610163194A priority patent/CN100593277C/en
Priority to EP02770193A priority patent/EP1425837B1/en
Priority to PCT/JP2002/009362 priority patent/WO2003026095A1/en
Priority to US10/467,682 priority patent/US7012405B2/en
Priority to KR1020037014514A priority patent/KR100572160B1/en
Priority to CNB028094433A priority patent/CN100350713C/en
Publication of JP2003087990A publication Critical patent/JP2003087990A/en
Priority to US11/259,186 priority patent/US7205748B2/en
Priority to US11/295,450 priority patent/US7274171B2/en
Priority to US11/755,226 priority patent/US20070222420A1/en
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • Charge And Discharge Circuits For Batteries Or The Like (AREA)
  • Secondary Cells (AREA)

Description

【０００１】
【発明の属する技術分野】
本発明は、充電可能な二次電池の充電回路に関し、特に、急速充電が可能で携帯電話等のような使用機器に影響を与える周波数帯域のノイズの発生を防止する二次電池の充電回路に関するものである。
【０００２】
【従来の技術】
リチウムイオン電池の充電方法として、大きく分けて定電流−定電圧充電方法とパルス充電方法がよく用いられる。定電流−定電圧充電方法では、リチウムイオン電池に対する充電電流を大きくしたり、充電時にリチウムイオン電池に印加する定電圧を該電池の満充電電圧よりも少し大きくすることにより充電時間を短くすることができる。しかし、リチウムイオン電池に対して過充電を行うと該電池の性能を低下させる恐れがあった。これに対して、パルス充電方式では、リチウムイオン電池に対する充電の休止期間を取るため電池に損傷を与えることが少ない方式である。
【０００３】
このようなパルス充電方式では、次のような３つの方法があった。
第１の方法として、特開平６−１１３４７４号公報で開示されているように、休止期間の電圧が所定の電圧に達した場合に充電完了とする方法である。
第２の方法として、充電中に第１の電圧に達すると充電を停止し、第２の電圧まで低下すると充電を再開させる等、充電開始と充電停止の条件を定めてその条件の間で充電と充電停止を繰り返し、充電停止期間が所定の時間以上、又は充電期間と充電停止期間の比が所定値を超えたときに充電完了とする方法である。
第３の方法として、特開平７−３３６９０８号公報で開示されているように、高レベルと低レベルの電圧で交互に充電を繰り返し、低レベルでの充電電流が所定の電流値以下になったとき充電完了とする方法である。
【０００４】
【発明が解決しようとする課題】
しかし、前記第１の方法では、定電流−定電圧充電方式と比較して充電時間が長くなるという問題があった。また、前記第２の方法では、定電流−定電圧方式に比べて充電時間はやや短縮されるが、充電期間と充電停止期間の各時間が充電開始から充電終了間際までの間で大きく変化するため、充電期間と充電停止期間の繰り返しの周波数が広い範囲で変化するため、広い周波数帯域に渡ってノイズが発生するという問題があった。
【０００５】
また、前記第３の方法では、低レベルでの充電電流を検出するための電流検出手段が必要になり、該電流検出手段として、充電回路に直列に電流検出素子を挿入するため、電力ロスが発生するという問題があり、更に、充電電流がゼロになったことを検出するために電流検出抵抗の値を大きくする必要があることから電力ロスは更に大きくなると共に、複雑な回路が必要になるという問題があった。
【０００６】
本発明は、上記のような問題を解決するためになされたものであり、簡単な回路で、充電時間を短くすることができると共に、使用機器に影響を与える周波数帯域のノイズの発生を防止することができる二次電池の充電回路を得ることを目的とする。
【０００７】
【課題を解決するための手段】
この発明に係る二次電池の充電回路は、リチウムイオン電池等の二次電池の充電を行う二次電池の充電回路において、入力された制御信号に応じて、あらかじめ設定された複数の定電圧の１つを選択して出力し、前記二次電池に該定電圧を印加して充電を行う定電圧回路部と、前記二次電池の電池電圧を検出して出力する電池電圧検出回路部と、該電池電圧検出回路部からの検出電圧に応じて、前記定電圧回路部から出力される定電圧の切替制御を行う制御回路部とを備え、前記制御回路部は、前記定電圧回路部に対して、二次電池の電池電圧が所定の第１定電圧以下のときは、第１定電圧を二次電池に印加させて充電を行わせ、二次電池の電池電圧が前記第１定電圧を超えると、所定の第２定電圧と該第２定電圧よりも小さい所定の第３定電圧を一定の周期で交互に二次電池に印加させて充電を行わせるものである。
【０００８】
また、前記制御回路部は、定電圧回路部に対して前記第３定電圧を二次電池に印加させている際に、該二次電池の電池電圧が所定の充電完了電圧を超えると二次電池の充電が完了したことを検知し、所定の充電完了動作を行うようにした。
【０００９】
具体的には、前記第２定電圧を、第１定電圧と同じ電圧になるようにした。
【００１０】
また、前記第２定電圧を、第１定電圧よりも大きくなるようにしてもよい。
【００１１】
一方、前記定電圧回路部から出力された定電圧に応じて前記二次電池に並列に負荷を接続する負荷回路部を備え、該負荷回路部は、定電圧回路部から第３定電圧が出力されている間、前記二次電池に並列に負荷を接続するようにした。
【００１２】
具体的には、前記定電圧回路部は、前記第１定電圧、第２定電圧及び第３定電圧をそれぞれ生成して出力する定電圧発生回路と、前記制御回路部からの制御信号に応じて、該定電圧発生回路から出力された第１定電圧、第２定電圧又は第３定電圧のいずれか１つを選択して出力する電圧切替回路と、該電圧切替回路から出力された定電圧と、前記二次電池の電池電圧との電圧比較を行い、該比較結果に応じた信号を出力する電圧比較器と、該電圧比較器からの比較結果に応じた電流を所定の直流電源から前記二次電池に出力する制御用トランジスタと、前記二次電池から該制御用トランジスタを介して直流電源へ流れる電流を阻止するダイオードとを備えるようにした。
【００１３】
【発明の実施の形態】
次に、図面に示す実施の形態に基づいて、本発明を詳細に説明する。
図１は、本発明の第１の実施の形態における二次電池の充電回路の構成例を示した図である。なお、図１では、携帯電話に使用される、リチウムイオン電池の充電回路を例にして示している。
図１において、二次電池の充電回路１は、直流電源をなすＡＣアダプタ１０からの電源電圧が所定値以上になると所定の信号を出力するアダプタ検出回路２と、二次電池をなすリチウムイオン電池１１の正側電圧（以下、これを電池電圧と呼ぶ）Ｖｂを検出して出力する電池電圧検出回路３と、定電圧でリチウムイオン電池１１の充電を行う定電圧回路４とを備えている。
【００１４】
更に、充電回路１は、所定の定電流でリチウムイオン電池１１のプリチャージを行うプリチャージ用定電流回路５と、アダプタ検出回路２からの信号と電池電圧検出回路３からの検出電圧に応じて、定電圧回路４にリチウムイオン電池１１に対するパルス充電方式の充電を行わせると共にプリチャージ用定電流回路５に前記プリチャージを行わせる充電制御回路６と、リチウムイオン電池１１に並列に接続された負荷回路７とを備えている。
【００１５】
また、定電圧回路４は、３つの所定の定電圧Ｅ１〜Ｅ３をそれぞれ生成して出力する定電圧発生回路２１と、充電制御回路６からの制御信号に応じて該定電圧発生回路２１からの定電圧Ｅ１〜Ｅ３のいずれか１つを選択して基準電圧Ｖｒとして出力する電圧切替回路２２と、電圧比較器をなす演算増幅器２３と、リチウムイオン電池１１に対してＡＣアダプタ１０からの充電電流の供給制御を行うＰＭＯＳトランジスタからなる制御用トランジスタ２４と、ダイオード２５と、演算増幅器２３からの出力信号に応じて該制御用トランジスタ２４の動作制御を行うゲート制御回路２６とで構成されている。なお、充電制御回路６は、制御回路部をなし、定電圧Ｅ１が第１定電圧を、定電圧Ｅ２が第２定電圧を、定電圧Ｅ３が第３定電圧をそれぞれなしている。
【００１６】
ＡＣアダプタ１０から電源が供給される電源端子３１と接地との間には、リチウムイオン電池１１に充電電流の供給が行われるように、制御用トランジスタ２４と、ダイオード２５とリチウムイオン電池１１が直列に接続されている。ダイオード２５は、電源端子３１の電圧がリチウムイオン電池１１の電池電圧Ｖｂよりも小さい場合に、リチウムイオン電池１１からＡＣアダプタ１０へ電流が逆流することを阻止するためのものである。
【００１７】
電圧切替回路２２は、充電制御回路６からの電圧切替信号Ｓｓに応じて定電圧Ｅ１〜Ｅ３のいずれか１つを選択して演算増幅器２３の反転入力端に出力する。演算増幅器２３の非反転入力端には、リチウムイオン電池１１の電池電圧Ｖｂが印加され、演算増幅器２３の出力端はゲート制御回路２６を介して制御用トランジスタ２４のゲートに接続されている。また、演算増幅器２３は、充電制御回路６からの制御信号によって駆動制御が行われる。
【００１８】
一方、負荷回路７は、抵抗３５とＮＭＯＳトランジスタ３６との直列回路で形成されており、リチウムイオン電池１１の正側電極と接地との間に抵抗３５及びＮＭＯＳトランジスタ３６が直列に接続されている。ＮＭＯＳトランジスタ３６は、電圧切替回路２２で選択された定電圧に応じて作動し、オンすることによって抵抗３５が定電圧回路４の制御用トランジスタ２４に対する負荷となるようにする。定電圧Ｅ１〜Ｅ３は、Ｅ２≧Ｅ１＞Ｅ３という関係にあり、電圧切替回路２２が、電圧切替信号Ｓｓによって定電圧Ｅ３を基準電圧Ｖｒとして選択すると、ＮＭＯＳトランジスタ３６はオンし、定電圧Ｅ１又はＥ２が基準電圧Ｖｒに選択されるとＮＭＯＳトランジスタ３６はオフして遮断状態になる。
【００１９】
このような構成において、図２は、図１で示した充電回路１の動作例を示したタイミングチャートであり、図２を参照しながら図１の各部の動作例について説明する。
まず、充電制御回路６は、ＡＣアダプタ１０から電源の供給が行われてアダプタ検出回路２から所定の信号が入力されると起動する。電池電圧検出回路３は、リチウムイオン電池１１の電池電圧Ｖｂの検出を行い、該検出した電圧値を充電制御回路６に出力する。
【００２０】
充電制御回路６は、リチウムイオン電池１１の電池電圧Ｖｂが所定値Ｖ１以下である場合、プリチャージ用定電流回路５を起動させて、所定のプリチャージ電流Ｉｐでリチウムイオン電池１１のプリチャージを開始させる。なお、このとき、充電制御回路６は、演算増幅器２３の動作を停止させて、制御用トランジスタ２４を介してリチウムイオン電池１１へ電流が流れないようにしている。
【００２１】
前記所定値Ｖ１は、例えば４.２Ｖのリチウムイオン電池１１の場合、約２．５Ｖに設定するとよい。これは、リチウムイオン電池１１が過放電状態にあるときに、いきなり大電流でリチウムイオン電池１１の充電を行うと不具合が生じるため、充電開始時には充電電流を絞ってリチウムイオン電池１１のプリチャージを行う。プリチャージ電流Ｉｐは、このようにするための電流であり、通常数ｍＡ〜数十ｍＡ程度の電流値にする。
【００２２】
リチウムイオン電池１１の電池電圧Ｖｂが上昇して所定値Ｖ１になると、充電制御回路６は、リチウムイオン電池１１が正常な電池であると判断してプリチャージ用定電流回路５によるプリチャージを終了させ、電圧切替信号Ｓｓを出力して定電圧回路４による、定電圧充電に切り替える。なお、プリチャージ期間中は、定電圧回路４の動作は停止しており、ダイオード２５はこのときにリチウムイオン電池１１からＡＣアダプタ１０へ電流が流れることを防止する。
【００２３】
充電制御回路６は、プリチャージが終了すると、電圧切替信号Ｓｓによって電圧切替回路２２に定電圧Ｅ１を選択させ、選択された定電圧Ｅ１は、基準電圧Ｖｒとして演算増幅器２３の反転入力端に出力される。定電圧回路４は、出力電圧が定電圧Ｅ１となり、該定電圧Ｅ１でリチウムイオン電池１１の充電を行う。定電圧Ｅ１でリチウムイオン電池１１の充電を行っているときの充電電流Ｉｃは図２で示すようになり、ＡＣアダプタ１０の電流容量又は制御用トランジスタ２４の電流容量で制限された一定の電流が充電電流Ｉｃとして定電圧回路４から出力される。
【００２４】
リチウムイオン電池１１の電池電圧Ｖｂが次第に上昇して、定電圧回路４の出力電圧と等しい電圧Ｅ１に達すると、充電制御回路６は、定電圧回路４に対して、リチウムイオン電池１１をパルス充電方式で充電するように動作制御を行う。なお、定電圧Ｅ１は、リチウムイオン電池の場合、満充電電圧である４.２Ｖに設定するとよい。
【００２５】
パルス充電方式は、定電圧回路４の出力電圧が定電圧Ｅ２と定電圧Ｅ３に所定の周期で繰り返し切り替えて、リチウムイオン電池１１の充電を行う方法である。リチウムイオン電池１１の電圧が電圧Ｅ１に達すると、充電制御回路６は、電圧切替回路２２に対して定電圧Ｅ３を選択するように電圧切替信号Ｓｓを出力し、定電圧回路４の出力電圧が定電圧Ｅ３になるように設定する。定電圧Ｅ３は定電圧Ｅ１より低い電圧であるが、パルス充電方式に切り替わった直後に十分な充電電流Ｉｃがリチウムイオン電池１１に出力できるような電圧に設定してある。例えば、定電圧Ｅ３は、４.２Ｖのリチウムイオン電池の場合、４.０Ｖから４.１Ｖになるように設定するとよい。
【００２６】
次に、充電制御回路６は、電圧切替回路２２に対して定電圧Ｅ３を選択するように電圧切替信号Ｓｓを出力してから所定時間Ｔ１が経過した後、電圧切替回路２２に対して定電圧Ｅ２を選択するように電圧切替信号Ｓｓを出力する。電圧切替回路２２は、定電圧Ｅ２を選択して出力し、定電圧回路４の出力電圧が定電圧Ｅ２になるようにする。定電圧Ｅ２は定電圧Ｅ１と同じ電圧に設定してもよいし、定電圧Ｅ１よりもやや大きめ、例えば約０.１Ｖ大きくなるように設定してもよい。なお、図２では、定電圧Ｅ２が定電圧Ｅ１よりも大きい場合を例にして示している。
【００２７】
定電圧Ｅ２を定電圧Ｅ１と同じ電圧に設定した場合、リチウムイオン電池１１に過電圧が印加されることがないため、リチウムイオン電池１１を損傷させる心配がなく、更に、定電圧Ｅ１と共通の電圧にすることから回路が簡単にすることができるが、充電時間が少し長くなるという欠点がある。定電圧Ｅ２を定電圧Ｅ１よりも少し大きめに設定した場合は、充電時間を短縮させることができると共に、パルス充電方式であるためリチウムイオン電池を損傷させる可能性を小さくすることができる。
【００２８】
次に、充電制御回路６は、電圧切替回路２２に対して定電圧Ｅ２を選択するように電圧切替信号Ｓｓを出力してから所定時間Ｔ１が経過した後、電圧切替回路２２に対して再び定電圧Ｅ３を選択するように電圧切替信号Ｓｓを出力する。電圧切替回路２２は、再び定電圧Ｅ３を選択して出力し、定電圧回路４の出力電圧を定電圧Ｅ３になるようにする。このように、充電制御回路６は、リチウムイオン電池１１の充電が完了するまで、定電圧回路４に対して定電圧Ｅ２とＥ３を一定の周期で交互に出力させる。
【００２９】
ここで、図２から分かるように、パルス充電方式に切り替わった直後は、定電圧回路４の出力電圧が定電圧Ｅ３であっても定電圧Ｅ２であっても、充電電流Ｉｃは、ＡＣアダプタ１０の電流容量又は制御用トランジスタ２４の電流容量で制限された電流となることからほぼ一定である。しかし、リチウムイオン電池１１の充電が進んでゆくと、定電圧Ｅ３で充電を行っているときの充電電流Ｉｃが徐々に減少していく。更に、リチウムイオン電池１１の充電が進んで、リチウムイオン電池１１の電池電圧Ｖｂが定電圧Ｅ３以上になると、定電圧Ｅ３で充電を行うときは充電電流Ｉｃが流れなくなる。このような状態は、充電と充電停止を繰り返す一般的なパルス充電方式と同様の充電形態であり、リチウムイオン電池１１の損傷を防いで寿命を伸ばすことができる充電方法となる。
【００３０】
更にリチウムイオン電池１１の充電が進み、定電圧Ｅ３で充電を行っているときのリチウムイオン電池１１の電池電圧Ｖｂが、所定の充電完了電圧Ｖｅを超えると、充電制御回路６は、リチウムイオン電池１１の充電が完了したと判断し、演算増幅器２３の動作を停止させて定電圧回路４の動作を停止させ、リチウムイオン電池１１に対する充電動作を停止する。
【００３１】
ここで、負荷回路７のＮＭＯＳトランジスタ３６は、電圧切替回路２２が定電圧Ｅ３を選択したときにオンし、ＮＭＯＳトランジスタ３６がオンすると、抵抗３５が定電圧回路４の負荷をなすようになる。このようにすることにより、定電圧回路４の出力電圧が定電圧Ｅ２から定電圧Ｅ３に切り替わったときに、リチウムイオン電池１１の電池電圧Ｖｂが安定した電圧に到達する時間を短くすることができ、充電制御回路６で行われる充電完了電圧Ｖｅとの比較に要する時間を短くすることができる。このため、定電圧Ｅ３でリチウムイオン電池１１を充電する時間は短く設定することができ、パルス充電の充電サイクルを使用機器に影響を与えない周波数に設定する自由度を高めることができる。
【００３２】
図３は、充電制御回路６の動作例を示したフローチャートであり、図３を用いて充電制御回路６の動作の流れについて説明する。なお、特に明記しない限り、各フローで行われる処理は充電制御回路６で行われるものである。
図３において、まず最初に、アダプタ検出回路２から入力される信号から、電源端子３１の電圧が所定の電圧以上になったか否かの検出を行い（ステップＳ１）、所定の電圧以上になったことを検出できなかった場合（ＮＯ）は、引き続き電源端子３１の電圧が所定の電圧以上になったか否かの検出を行い、所定の電圧以上になったことを検出した場合（ＹＥＳ）は、電池電圧検出回路３で検出されたリチウムイオン電池１１の電池電圧Ｖｂが所定値Ｖ１を超えているか否かを調べる（ステップＳ２）。
【００３３】
ステップＳ２で、リチウムイオン電池１１の電池電圧Ｖｂが所定値Ｖ１以下の場合（ＮＯ）は、プリチャージ用定電流回路５を作動させてリチウムイオン電池１１に対してプリチャージを行い（ステップＳ３）、ステップＳ２に戻る。これに対して、ステップＳ２で、リチウムイオン電池１１の電池電圧Ｖｂが所定値Ｖ１を超えている場合（ＹＥＳ）は、演算増幅器２３を動作させると共に電圧切替回路２２に定電圧Ｅ１を選択させ、リチウムイオン電池１１に対して定電圧Ｅ１による定電圧充電を行わせる（ステップＳ４）。
【００３４】
この後、リチウムイオン電池１１の電池電圧Ｖｂが定電圧Ｅ１を超えているか否かを調べ（ステップＳ５）、リチウムイオン電池１１の電池電圧Ｖｂが定電圧Ｅ１以下の場合（ＮＯ）は、引き続きリチウムイオン電池１１の電池電圧Ｖｂが定電圧Ｅ１を超えているか否かを調べる。これに対して、ステップＳ５で、リチウムイオン電池１１の電圧が定電圧Ｅ１を超えている場合（ＹＥＳ）は、電圧切替回路２２に定電圧Ｅ３を選択させ、定電圧回路４に対してリチウムイオン電池１１を定電圧Ｅ３で充電させる（ステップＳ６）。
【００３５】
次に、定電圧Ｅ３での充電を開始してから所定の時間Ｔ１が経過したか否かを調べ（ステップＳ７）、所定の時間Ｔ１が経過していない場合（ＮＯ）は、所定の時間Ｔ１が経過するまで定電圧Ｅ３で充電を行う。また、ステップＳ７で、所定の時間Ｔ１が経過した場合（ＹＥＳ）は、電池電圧Ｖｂが所定の充電完了電圧Ｖｅ以上であるか否かを調べ（ステップＳ８）、充電完了電圧Ｖｅ以上である場合（ＹＥＳ）は、リチウムイオン電池１１への充電が完了し本フローは終了する。
【００３６】
また、ステップＳ８で、電池電圧Ｖｂが充電完了電圧Ｖｅ未満である場合（ＮＯ）は、電圧切替回路２２に定電圧Ｅ２を選択させ、定電圧回路４に対してリチウムイオン電池１１を定電圧Ｅ２で充電させる（ステップＳ９）。次に、定電圧Ｅ２での充電を開始してから所定の時間Ｔ１が経過したか否かを調べ（ステップＳ１０）、所定の時間Ｔ１が経過していない場合（ＮＯ）は、所定の時間Ｔ１が経過するまで定電圧Ｅ２で充電を行う。また、ステップＳ１０で、所定の時間Ｔ１が経過した場合（ＹＥＳ）は、ステップＳ６に戻る。
【００３７】
このように、本第１の実施の形態における充電回路は、リチウムイオン電池１１に対して、電池電圧Ｖｂが所定値Ｖ１以下のときは、プリチャージ用定電流回路５からのプリチャージ電流Ｉｐでプリチャージを行い、電池電圧Ｖｂが所定値Ｖ１を超えると、定電圧回路４からの定電圧Ｅ１で定電圧充電を行い、電池電圧Ｖｂが定電圧Ｅ１になると、電圧切替回路２２に対する定電圧切替制御を行って定電圧回路４から一定の周期で定電圧Ｅ２とＥ３が交互に出力されるようにして、パルス充電を行うようにした。このことから、簡単な回路を追加することによって、リチウムイオン電池の充電を行う場合に、充電時間を短くすることができると共に使用機器に影響を与える周波数帯域のノイズの発生を防止することができる。
【００３８】
【発明の効果】
上記の説明から明らかなように、本発明の充電回路によれば、二次電池の電池電圧が所定の第１定電圧以下のときは、該第１定電圧を二次電池に印加させて充電を行わせ、二次電池の電池電圧が前記第１定電圧を超えると、所定の第２定電圧と該第２定電圧よりも小さい所定の第３定電圧を一定の周期で交互に二次電池に印加させて充電を行うようにした。このことから、パルス充電を行う前に定電圧充電を行うことから大電流で充電することができ、パルス充電開始後も高レベルと低レベルの２つの定電圧を一定の周期で切り替えて充電を行うため、充電電流が継続されて充電時間を短縮することができると共に、該切り替え周期を使用機器に悪影響を与えない周波数に設定することができる。
【００３９】
また、第３定電圧を二次電池に印加させている際に、該二次電池の電池電圧が所定の充電完了電圧を超えると二次電池の充電が完了したことを検知し、所定の充電完了動作を行うようにした。このことから、過充電を確実に防止することができる。
【００４０】
具体的には、前記第２定電圧を第１定電圧と同じ電圧になるようにした。このことから、回路の簡素化を図ることができ、二次電池に損傷を与えないように充電を行うことができる。
【００４１】
また、前記第２定電圧を第１定電圧よりも大きくなるようにしてもよく、このようにすることによって、パルス充電中の高レベルの電圧を満充電電圧より少し高くして、二次電池に損傷を与えることなく充電時間の短縮を図ることができる。
【００４２】
一方、定電圧回路部から第３定電圧が出力されている間、前記二次電池に並列に負荷が接続されるようにした。このことから、パルス充電時に第３定電圧で充電が行われている二次電池の電池電圧をすばやく安定させることができるため、充電完了電圧の検出誤差を少なくすることができ、パルス充電の周期の自由度を高めることができるため、該周期を使用機器に悪影響を与えない周波数に設定することができる。
【００４３】
具体的には、前記定電圧回路部は、前記第１定電圧、第２定電圧及び第３定電圧をそれぞれ生成して出力する定電圧発生回路と、前記制御回路部からの制御信号に応じて、該第１定電圧、第２定電圧又は第３定電圧のいずれか１つを選択して出力する電圧切替回路と、該選択された定電圧と二次電池の電池電圧との電圧比較を行う電圧比較器と、該電圧比較器からの比較結果に応じた電流を二次電池に出力する制御用トランジスタと、前記二次電池から該制御用トランジスタを介して直流電源へ流れる電流を阻止するダイオードとを備えるようにした。このことから、簡単な回路構成で、定電圧充電からパルス充電に切り替えて二次電池の充電を行うことができる。
【図面の簡単な説明】
【図１】 本発明の第１の実施の形態における二次電池の充電回路の構成例を示した図である。
【図２】 図１における充電回路１の動作例を示したタイミングチャートである。
【図３】 図１の充電制御回路６の動作例を示したフローチャートである。
【符号の説明】
１ 充電回路
２ アダプタ検出回路
３ 電池電圧検出回路
４ 定電圧回路
５ プリチャージ用定電流回路
６ 充電制御回路
７ 負荷回路
１０ ＡＣアダプタ
１１ リチウムイオン電池
２１ 定電圧発生回路
２２ 電圧切替回路
２３ 演算増幅器
２４ 制御用トランジスタ
２５ ダイオード
２６ ゲート制御回路[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a charging circuit for a rechargeable secondary battery, and more particularly, to a charging circuit for a secondary battery capable of rapid charging and preventing noise in a frequency band that affects devices used such as a mobile phone. Is.
[0002]
[Prior art]
As charging methods for lithium ion batteries, a constant current-constant voltage charging method and a pulse charging method are often used. In the constant current-constant voltage charging method, the charging time is shortened by increasing the charging current for the lithium ion battery or by making the constant voltage applied to the lithium ion battery slightly higher than the full charge voltage of the battery during charging. Can do. However, if the lithium ion battery is overcharged, the performance of the battery may be reduced. On the other hand, the pulse charging method is a method in which the battery is less damaged because the charging pause period for the lithium ion battery is taken.
[0003]
In such a pulse charging method, there are the following three methods.
As a first method, as disclosed in Japanese Patent Application Laid-Open No. 6-113474, the charging is completed when the voltage during the idle period reaches a predetermined voltage.
As a second method, the charging is stopped when the first voltage is reached during charging, and the charging is restarted when the voltage is lowered to the second voltage. Charging is repeated, and charging is completed when the charging stop period is equal to or longer than a predetermined time, or when the ratio of the charging period to the charging stop period exceeds a predetermined value.
As a third method, as disclosed in Japanese Patent Application Laid-Open No. 7-336908, charging is alternately repeated at a high level and a low level voltage, and the charging current at the low level becomes a predetermined current value or less. When charging is complete.
[0004]
[Problems to be solved by the invention]
However, the first method has a problem that the charging time is longer than that in the constant current-constant voltage charging method. In the second method, the charging time is slightly shortened as compared with the constant current-constant voltage method, but each time of the charging period and the charging stop period varies greatly between the start of charging and the end of charging. For this reason, the repetition frequency of the charging period and the charging stop period changes in a wide range, and thus there is a problem that noise occurs over a wide frequency band.
[0005]
Further, in the third method, a current detection means for detecting a charging current at a low level is required. Since the current detection element is inserted in series in the charging circuit as the current detection means, power loss is reduced. In addition, since it is necessary to increase the value of the current detection resistor in order to detect that the charging current has become zero, the power loss is further increased and a complicated circuit is required. There was a problem.
[0006]
The present invention has been made in order to solve the above-described problems. With a simple circuit, the charging time can be shortened, and the occurrence of noise in the frequency band that affects the equipment used can be prevented. An object of the present invention is to obtain a rechargeable battery charging circuit.
[0007]
[Means for Solving the Problems]
A charging circuit for a secondary battery according to the present invention is a charging circuit for a secondary battery that charges a secondary battery such as a lithium ion battery, and has a plurality of constant voltages set in advance according to an input control signal. Selecting and outputting one, applying a constant voltage to the secondary battery for charging, a battery voltage detecting circuit for detecting and outputting the battery voltage of the secondary battery, A control circuit unit that performs switching control of a constant voltage output from the constant voltage circuit unit according to a detection voltage from the battery voltage detection circuit unit, and the control circuit unit controls the constant voltage circuit unit. When the battery voltage of the secondary battery is equal to or lower than a predetermined first constant voltage, charging is performed by applying the first constant voltage to the secondary battery, and the battery voltage of the secondary battery is equal to the first constant voltage. If it exceeds, a predetermined second constant voltage and a predetermined third constant smaller than the second constant voltage. Is intended to perform the charging alternately it is applied to the secondary battery pressure at a constant period.
[0008]
In addition, when the control circuit unit causes the constant voltage circuit unit to apply the third constant voltage to the secondary battery, if the battery voltage of the secondary battery exceeds a predetermined charge completion voltage, It was detected that the charging of the battery was completed, and a predetermined charging completion operation was performed.
[0009]
Specifically, the second constant voltage is set to the same voltage as the first constant voltage.
[0010]
Further, the second constant voltage may be larger than the first constant voltage.
[0011]
On the other hand, a load circuit unit for connecting a load to the secondary battery in parallel according to the constant voltage output from the constant voltage circuit unit is provided, and the load circuit unit outputs a third constant voltage from the constant voltage circuit unit. During this time, a load was connected in parallel to the secondary battery.
[0012]
Specifically, the constant voltage circuit unit generates and outputs the first constant voltage, the second constant voltage, and the third constant voltage, and a control signal from the control circuit unit. A voltage switching circuit that selects and outputs one of the first constant voltage, the second constant voltage, and the third constant voltage output from the constant voltage generation circuit, and a constant output from the voltage switching circuit. Voltage comparison between the voltage and the battery voltage of the secondary battery, and a voltage comparator that outputs a signal according to the comparison result; and a current according to the comparison result from the voltage comparator from a predetermined DC power source A control transistor that outputs to the secondary battery and a diode that blocks a current flowing from the secondary battery to the DC power supply via the control transistor are provided.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Next, the present invention will be described in detail based on the embodiments shown in the drawings.
FIG. 1 is a diagram showing a configuration example of a charging circuit for a secondary battery in the first embodiment of the present invention. In FIG. 1, a charging circuit for a lithium ion battery used for a mobile phone is shown as an example.
In FIG. 1, a charging circuit 1 for a secondary battery includes an adapter detection circuit 2 that outputs a predetermined signal when a power supply voltage from an AC adapter 10 that forms a DC power supply exceeds a predetermined value, and a lithium ion battery that forms a secondary battery. 11 includes a battery voltage detection circuit 3 that detects and outputs a positive voltage 11 (hereinafter referred to as a battery voltage) Vb, and a constant voltage circuit 4 that charges the lithium ion battery 11 with a constant voltage.
[0014]
Further, the charging circuit 1 includes a precharge constant current circuit 5 that precharges the lithium ion battery 11 with a predetermined constant current, a signal from the adapter detection circuit 2, and a detection voltage from the battery voltage detection circuit 3. A charge control circuit 6 for causing the constant voltage circuit 4 to charge the lithium ion battery 11 in a pulse charge system and for the precharge constant current circuit 5 to perform the precharge, and the lithium ion battery 11 are connected in parallel. And a load circuit 7.
[0015]
The constant voltage circuit 4 generates and outputs three predetermined constant voltages E1 to E3, respectively, and the constant voltage generation circuit 21 in response to a control signal from the charge control circuit 6. A voltage switching circuit 22 that selects any one of the constant voltages E1 to E3 and outputs it as a reference voltage Vr, an operational amplifier 23 that forms a voltage comparator, and a charging current from the AC adapter 10 to the lithium ion battery 11 The control transistor 24 is a PMOS transistor that controls the supply of the signal, the diode 25, and the gate control circuit 26 that controls the operation of the control transistor 24 according to the output signal from the operational amplifier 23. The charging control circuit 6 is a control circuit unit, in which the constant voltage E1 is a first constant voltage, the constant voltage E2 is a second constant voltage, and the constant voltage E3 is a third constant voltage.
[0016]
Between the power supply terminal 31 to which power is supplied from the AC adapter 10 and the ground, the control transistor 24, the diode 25, and the lithium ion battery 11 are connected in series so that the charging current is supplied to the lithium ion battery 11. It is connected to the. The diode 25 is for preventing a current from flowing backward from the lithium ion battery 11 to the AC adapter 10 when the voltage at the power supply terminal 31 is smaller than the battery voltage Vb of the lithium ion battery 11.
[0017]
The voltage switching circuit 22 selects any one of the constant voltages E1 to E3 according to the voltage switching signal Ss from the charging control circuit 6 and outputs the selected voltage to the inverting input terminal of the operational amplifier 23. The battery voltage Vb of the lithium ion battery 11 is applied to the non-inverting input terminal of the operational amplifier 23, and the output terminal of the operational amplifier 23 is connected to the gate of the control transistor 24 via the gate control circuit 26. The operational amplifier 23 is driven and controlled by a control signal from the charge control circuit 6.
[0018]
On the other hand, the load circuit 7 is formed by a series circuit of a resistor 35 and an NMOS transistor 36, and the resistor 35 and the NMOS transistor 36 are connected in series between the positive electrode of the lithium ion battery 11 and the ground. . The NMOS transistor 36 operates according to the constant voltage selected by the voltage switching circuit 22 and turns on so that the resistor 35 becomes a load for the control transistor 24 of the constant voltage circuit 4. The constant voltages E1 to E3 have a relationship of E2 ≧ E1> E3. When the voltage switching circuit 22 selects the constant voltage E3 as the reference voltage Vr by the voltage switching signal Ss, the NMOS transistor 36 is turned on, and the constant voltage E1 or When E2 is selected as the reference voltage Vr, the NMOS transistor 36 is turned off and is turned off.
[0019]
In such a configuration, FIG. 2 is a timing chart showing an operation example of the charging circuit 1 shown in FIG. 1, and an operation example of each part of FIG. 1 will be described with reference to FIG.
First, the charging control circuit 6 is activated when power is supplied from the AC adapter 10 and a predetermined signal is input from the adapter detection circuit 2. The battery voltage detection circuit 3 detects the battery voltage Vb of the lithium ion battery 11 and outputs the detected voltage value to the charge control circuit 6.
[0020]
When the battery voltage Vb of the lithium ion battery 11 is equal to or less than the predetermined value V1, the charge control circuit 6 activates the precharge constant current circuit 5 to precharge the lithium ion battery 11 with the predetermined precharge current Ip. Let it begin. At this time, the charging control circuit 6 stops the operation of the operational amplifier 23 so that no current flows to the lithium ion battery 11 via the control transistor 24.
[0021]
The predetermined value V1 may be set to about 2.5V in the case of a 4.2V lithium ion battery 11, for example. This is because when the lithium ion battery 11 is suddenly charged with a large current when the lithium ion battery 11 is in an overdischarged state, a problem occurs. Therefore, at the start of charging, the charging current is reduced to precharge the lithium ion battery 11. Do. The precharge current Ip is a current for this purpose and is usually set to a current value of several mA to several tens mA.
[0022]
When the battery voltage Vb of the lithium ion battery 11 rises to a predetermined value V1, the charge control circuit 6 determines that the lithium ion battery 11 is a normal battery and terminates the precharge by the precharge constant current circuit 5 The voltage switching signal Ss is output to switch to constant voltage charging by the constant voltage circuit 4. During the precharge period, the operation of the constant voltage circuit 4 is stopped, and the diode 25 prevents current from flowing from the lithium ion battery 11 to the AC adapter 10 at this time.
[0023]
When the precharge is completed, the charging control circuit 6 causes the voltage switching circuit 22 to select the constant voltage E1 by the voltage switching signal Ss, and the selected constant voltage E1 is output to the inverting input terminal of the operational amplifier 23 as the reference voltage Vr. Is done. In the constant voltage circuit 4, the output voltage becomes the constant voltage E1, and the lithium ion battery 11 is charged with the constant voltage E1. The charging current Ic when charging the lithium ion battery 11 at the constant voltage E1 is as shown in FIG. 2, and a constant current limited by the current capacity of the AC adapter 10 or the current capacity of the control transistor 24 is The charging current Ic is output from the constant voltage circuit 4.
[0024]
When the battery voltage Vb of the lithium ion battery 11 gradually increases and reaches a voltage E1 equal to the output voltage of the constant voltage circuit 4, the charge control circuit 6 pulse-charges the lithium ion battery 11 to the constant voltage circuit 4. Operation control is performed so that the battery is charged by the method. In addition, in the case of a lithium ion battery, the constant voltage E1 is good to set to 4.2V which is a full charge voltage.
[0025]
The pulse charging method is a method of charging the lithium ion battery 11 by repeatedly switching the output voltage of the constant voltage circuit 4 between the constant voltage E2 and the constant voltage E3 at a predetermined cycle. When the voltage of the lithium ion battery 11 reaches the voltage E1, the charging control circuit 6 outputs a voltage switching signal Ss to the voltage switching circuit 22 so as to select the constant voltage E3, and the output voltage of the constant voltage circuit 4 is Set to constant voltage E3. The constant voltage E3 is lower than the constant voltage E1, but is set to such a voltage that a sufficient charging current Ic can be output to the lithium ion battery 11 immediately after switching to the pulse charging method. For example, the constant voltage E3 may be set to be 4.0V to 4.1V in the case of a 4.2V lithium ion battery.
[0026]
Next, the charging control circuit 6 outputs a constant voltage E3 to the voltage switching circuit 22 after a predetermined time T1 has elapsed since the voltage switching signal Ss is output so as to select the constant voltage E3. The voltage switching signal Ss is output so as to select E2. The voltage switching circuit 22 selects and outputs the constant voltage E2 so that the output voltage of the constant voltage circuit 4 becomes the constant voltage E2. The constant voltage E2 may be set to the same voltage as the constant voltage E1, or may be set to be slightly larger than the constant voltage E1, for example, about 0.1V. FIG. 2 shows an example where the constant voltage E2 is larger than the constant voltage E1.
[0027]
When the constant voltage E2 is set to the same voltage as the constant voltage E1, an overvoltage is not applied to the lithium ion battery 11, so that there is no fear of damaging the lithium ion battery 11, and a voltage common to the constant voltage E1. Therefore, the circuit can be simplified, but there is a disadvantage that the charging time is slightly longer. When the constant voltage E2 is set slightly higher than the constant voltage E1, the charging time can be shortened and the possibility of damaging the lithium ion battery can be reduced because of the pulse charging method.
[0028]
Next, the charging control circuit 6 outputs the voltage switching signal Ss so as to select the constant voltage E2 to the voltage switching circuit 22 and then again determines the voltage switching circuit 22 after the predetermined time T1 has elapsed. The voltage switching signal Ss is output so as to select the voltage E3. The voltage switching circuit 22 selects and outputs the constant voltage E3 again so that the output voltage of the constant voltage circuit 4 becomes the constant voltage E3. In this way, the charging control circuit 6 causes the constant voltage circuit 4 to alternately output the constant voltages E2 and E3 at a constant period until the charging of the lithium ion battery 11 is completed.
[0029]
Here, as can be seen from FIG. 2, immediately after switching to the pulse charging method, the charging current Ic is equal to the AC adapter 10 regardless of whether the output voltage of the constant voltage circuit 4 is the constant voltage E3 or the constant voltage E2. Current capacity or current limited by the current capacity of the control transistor 24 is almost constant. However, as the charging of the lithium ion battery 11 proceeds, the charging current Ic during charging at the constant voltage E3 gradually decreases. Further, when the charging of the lithium ion battery 11 proceeds and the battery voltage Vb of the lithium ion battery 11 becomes equal to or higher than the constant voltage E3, the charging current Ic does not flow when charging is performed at the constant voltage E3. Such a state is a charging method similar to a general pulse charging method in which charging and stopping of charging are repeated, and is a charging method that can prevent damage to the lithium ion battery 11 and extend its life.
[0030]
When the charging of the lithium ion battery 11 further proceeds and the battery voltage Vb of the lithium ion battery 11 when charging at the constant voltage E3 exceeds a predetermined charging completion voltage Ve, the charging control circuit 6 11 is completed, the operation of the operational amplifier 23 is stopped, the operation of the constant voltage circuit 4 is stopped, and the charging operation for the lithium ion battery 11 is stopped.
[0031]
Here, the NMOS transistor 36 of the load circuit 7 is turned on when the voltage switching circuit 22 selects the constant voltage E3. When the NMOS transistor 36 is turned on, the resistor 35 becomes a load of the constant voltage circuit 4. Thus, when the output voltage of the constant voltage circuit 4 is switched from the constant voltage E2 to the constant voltage E3, it is possible to shorten the time for the battery voltage Vb of the lithium ion battery 11 to reach a stable voltage. The time required for the comparison with the charge completion voltage Ve performed by the charge control circuit 6 can be shortened. For this reason, the time for charging the lithium ion battery 11 with the constant voltage E3 can be set short, and the degree of freedom for setting the charging cycle of pulse charging to a frequency that does not affect the equipment used can be increased.
[0032]
FIG. 3 is a flowchart showing an example of the operation of the charge control circuit 6. The operation flow of the charge control circuit 6 will be described with reference to FIG. Unless otherwise specified, the processing performed in each flow is performed by the charging control circuit 6.
In FIG. 3, first, it is detected from the signal input from the adapter detection circuit 2 whether or not the voltage at the power supply terminal 31 has become a predetermined voltage or higher (step S1). If this could not be detected (NO), it continues to detect whether or not the voltage at the power supply terminal 31 has become a predetermined voltage or higher. If it has been detected that the voltage has been higher than the predetermined voltage (YES), It is checked whether or not the battery voltage Vb of the lithium ion battery 11 detected by the battery voltage detection circuit 3 exceeds a predetermined value V1 (step S2).
[0033]
If the battery voltage Vb of the lithium ion battery 11 is equal to or lower than the predetermined value V1 in step S2 (NO), the precharge constant current circuit 5 is operated to precharge the lithium ion battery 11 (step S3). Return to step S2. On the other hand, when the battery voltage Vb of the lithium ion battery 11 exceeds the predetermined value V1 in step S2 (YES), the operational amplifier 23 is operated and the voltage switching circuit 22 is selected to select the constant voltage E1, The lithium ion battery 11 is charged at a constant voltage with a constant voltage E1 (step S4).
[0034]
Thereafter, it is checked whether or not the battery voltage Vb of the lithium ion battery 11 exceeds the constant voltage E1 (step S5). If the battery voltage Vb of the lithium ion battery 11 is equal to or lower than the constant voltage E1 (NO), the lithium voltage continues. It is examined whether or not the battery voltage Vb of the ion battery 11 exceeds the constant voltage E1. On the other hand, when the voltage of the lithium ion battery 11 exceeds the constant voltage E1 in step S5 (YES), the voltage switching circuit 22 is selected to select the constant voltage E3 and The battery 11 is charged with the constant voltage E3 (step S6).
[0035]
Next, it is checked whether or not a predetermined time T1 has elapsed since the start of charging at the constant voltage E3 (step S7). If the predetermined time T1 has not elapsed (NO), the predetermined time T1 is reached. The battery is charged at a constant voltage E3 until elapses. If the predetermined time T1 has elapsed in step S7 (YES), it is checked whether or not the battery voltage Vb is equal to or higher than the predetermined charge completion voltage Ve (step S8), and is equal to or higher than the charge completion voltage Ve. In (YES), the charging of the lithium ion battery 11 is completed, and this flow ends.
[0036]
If the battery voltage Vb is less than the charge completion voltage Ve in step S8 (NO), the voltage switching circuit 22 is made to select the constant voltage E2, and the constant voltage circuit 4 causes the lithium ion battery 11 to be connected to the constant voltage E2. (Step S9). Next, it is checked whether or not a predetermined time T1 has elapsed since the start of charging at the constant voltage E2 (step S10). If the predetermined time T1 has not elapsed (NO), the predetermined time T1 is reached. The battery is charged at a constant voltage E2 until elapses. If the predetermined time T1 has elapsed in step S10 (YES), the process returns to step S6.
[0037]
As described above, the charging circuit according to the first embodiment uses the precharge current Ip from the precharge constant current circuit 5 when the battery voltage Vb is equal to or lower than the predetermined value V1 with respect to the lithium ion battery 11. When precharging is performed and the battery voltage Vb exceeds a predetermined value V1, constant voltage charging is performed with the constant voltage E1 from the constant voltage circuit 4, and when the battery voltage Vb reaches the constant voltage E1, constant voltage switching with respect to the voltage switching circuit 22 is performed. The control is performed so that the constant voltages E2 and E3 are alternately output from the constant voltage circuit 4 at a constant cycle, and pulse charging is performed. Therefore, by adding a simple circuit, when charging a lithium ion battery, it is possible to shorten the charging time and to prevent the generation of noise in the frequency band that affects the device used. .
[0038]
【The invention's effect】
As apparent from the above description, according to the charging circuit of the present invention, when the battery voltage of the secondary battery is equal to or lower than the predetermined first constant voltage, charging is performed by applying the first constant voltage to the secondary battery. When the battery voltage of the secondary battery exceeds the first constant voltage, a predetermined second constant voltage and a predetermined third constant voltage smaller than the second constant voltage are alternately secondary in a constant cycle. It was made to charge by applying to a battery. Therefore, constant voltage charging is performed before pulse charging, so that charging can be performed with a large current. After pulse charging starts, charging is performed by switching between two constant voltages of high level and low level at a constant cycle. Therefore, the charging current can be continued and the charging time can be shortened, and the switching cycle can be set to a frequency that does not adversely affect the equipment used.
[0039]
In addition, when the third constant voltage is applied to the secondary battery, when the battery voltage of the secondary battery exceeds a predetermined charging completion voltage, it is detected that the charging of the secondary battery is completed, and the predetermined charging is performed. Added completion action. For this reason, overcharge can be reliably prevented.
[0040]
Specifically, the second constant voltage is set to the same voltage as the first constant voltage. Thus, the circuit can be simplified and charging can be performed without damaging the secondary battery.
[0041]
Further, the second constant voltage may be larger than the first constant voltage, and in this way, the high level voltage during pulse charging is made slightly higher than the full charge voltage, and the secondary battery The charging time can be shortened without damaging the battery.
[0042]
On the other hand, while the third constant voltage is output from the constant voltage circuit unit, a load is connected in parallel to the secondary battery. This makes it possible to quickly stabilize the battery voltage of the secondary battery that is charged at the third constant voltage during pulse charging, thereby reducing the detection error of the charging completion voltage and the period of pulse charging. Therefore, the period can be set to a frequency that does not adversely affect the equipment used.
[0043]
Specifically, the constant voltage circuit unit generates and outputs the first constant voltage, the second constant voltage, and the third constant voltage, and a control signal from the control circuit unit. A voltage switching circuit that selects and outputs one of the first constant voltage, the second constant voltage, and the third constant voltage, and a voltage comparison between the selected constant voltage and the battery voltage of the secondary battery Comparator, a control transistor for outputting a current according to the comparison result from the voltage comparator to the secondary battery, and a current flowing from the secondary battery to the DC power supply through the control transistor is blocked. And a diode to be provided. Therefore, the secondary battery can be charged by switching from constant voltage charging to pulse charging with a simple circuit configuration.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration example of a charging circuit for a secondary battery according to a first embodiment of the present invention.
FIG. 2 is a timing chart showing an operation example of the charging circuit 1 in FIG.
3 is a flowchart showing an operation example of the charge control circuit 6 of FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Charging circuit 2 Adapter detection circuit 3 Battery voltage detection circuit 4 Constant voltage circuit 5 Precharge constant current circuit 6 Charge control circuit 7 Load circuit 10 AC adapter 11 Lithium ion battery 21 Constant voltage generation circuit 22 Voltage switching circuit 23 Operational amplifier 24 Control transistor 25 Diode 26 Gate control circuit

Claims (6)

リチウムイオン電池等の二次電池の充電を行う二次電池の充電回路において、
入力された制御信号に応じて、あらかじめ設定された複数の定電圧の１つを選択して出力し、前記二次電池に該定電圧を印加して充電を行う定電圧回路部と、
前記二次電池の電池電圧を検出して出力する電池電圧検出回路部と、
該電池電圧検出回路部からの検出電圧に応じて、前記定電圧回路部から出力される定電圧の切替制御を行う制御回路部と、
を備え、
前記制御回路部は、前記定電圧回路部に対して、二次電池の電池電圧が所定の第１定電圧以下のときは、第１定電圧を二次電池に印加させて充電を行わせ、二次電池の電池電圧が前記第１定電圧を超えると、所定の第２定電圧と該第２定電圧よりも小さい所定の第３定電圧を一定の周期で交互に二次電池に印加させて充電を行わせることを特徴とする二次電池の充電回路。In a secondary battery charging circuit that charges a secondary battery such as a lithium ion battery,
A constant voltage circuit unit that selects and outputs one of a plurality of preset constant voltages according to the input control signal, and applies the constant voltage to the secondary battery for charging.
A battery voltage detection circuit for detecting and outputting the battery voltage of the secondary battery;
A control circuit unit that performs switching control of a constant voltage output from the constant voltage circuit unit according to a detection voltage from the battery voltage detection circuit unit;
With
The control circuit unit causes the constant voltage circuit unit to charge the secondary battery by applying the first constant voltage when the battery voltage of the secondary battery is equal to or lower than a predetermined first constant voltage, When the battery voltage of the secondary battery exceeds the first constant voltage, a predetermined second constant voltage and a predetermined third constant voltage smaller than the second constant voltage are alternately applied to the secondary battery at a constant cycle. A charging circuit for a secondary battery, characterized in that charging is performed. 前記制御回路部は、定電圧回路部に対して前記第３定電圧を二次電池に印加させている際に、該二次電池の電池電圧が所定の充電完了電圧を超えると二次電池の充電が完了したことを検知し、所定の充電完了動作を行うことを特徴とする請求項１記載の二次電池の充電回路。The control circuit unit applies the third constant voltage to the secondary battery with respect to the constant voltage circuit unit, and if the battery voltage of the secondary battery exceeds a predetermined charging completion voltage, The charging circuit for a secondary battery according to claim 1, wherein the charging is detected, and a predetermined charging completion operation is performed. 前記第２定電圧は、第１定電圧と同じ電圧であることを特徴とする請求項１又は２記載の二次電池の充電回路。The secondary battery charging circuit according to claim 1, wherein the second constant voltage is the same voltage as the first constant voltage. 前記第２定電圧は、第１定電圧よりも大きいことを特徴とする請求項１又は２記載の二次電池の充電回路。The secondary battery charging circuit according to claim 1, wherein the second constant voltage is larger than the first constant voltage. 前記定電圧回路部から出力された定電圧に応じて前記二次電池に並列に負荷を接続する負荷回路部を備え、該負荷回路部は、定電圧回路部から第３定電圧が出力されている間、前記二次電池に並列に負荷を接続することを特徴とする請求項１、２、３又は４記載の二次電池の充電回路。A load circuit unit connected in parallel to the secondary battery according to the constant voltage output from the constant voltage circuit unit, the load circuit unit outputs a third constant voltage from the constant voltage circuit unit; 5. The secondary battery charging circuit according to claim 1, wherein a load is connected in parallel to the secondary battery. 前記定電圧回路部は、
前記第１定電圧、第２定電圧及び第３定電圧をそれぞれ生成して出力する定電圧発生回路と、
前記制御回路部からの制御信号に応じて、該定電圧発生回路から出力された第１定電圧、第２定電圧又は第３定電圧のいずれか１つを選択して出力する電圧切替回路と、
該電圧切替回路から出力された定電圧と、前記二次電池の電池電圧との電圧比較を行い、該比較結果に応じた信号を出力する電圧比較器と、
該電圧比較器からの比較結果に応じた電流を所定の直流電源から前記二次電池に出力する制御用トランジスタと、
前記二次電池から該制御用トランジスタを介して直流電源へ流れる電流を阻止するダイオードと、
を備えることを特徴とする請求項１、２、３、４又は５記載の二次電池の充電回路。The constant voltage circuit unit is:
A constant voltage generation circuit for generating and outputting the first constant voltage, the second constant voltage, and the third constant voltage, respectively;
A voltage switching circuit that selects and outputs one of the first constant voltage, the second constant voltage, and the third constant voltage output from the constant voltage generation circuit in response to a control signal from the control circuit unit; ,
A voltage comparator that performs a voltage comparison between the constant voltage output from the voltage switching circuit and the battery voltage of the secondary battery, and outputs a signal according to the comparison result;
A control transistor for outputting a current corresponding to a comparison result from the voltage comparator from a predetermined DC power source to the secondary battery;
A diode that blocks a current flowing from the secondary battery to the DC power source via the control transistor;
A charging circuit for a secondary battery according to claim 1, 2, 3, 4 or 5.
JP2001279823A 2001-09-14 2001-09-14 Secondary battery charging circuit Expired - Fee Related JP4499966B2 (en)

Priority Applications (12)

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JP2001279823A JP4499966B2 (en) 2001-09-14 2001-09-14 Secondary battery charging circuit
CNB028094433A CN100350713C (en) 2001-09-14 2002-09-12 Charging circuit for secondary battery
CN200610163194A CN100593277C (en) 2001-09-14 2002-09-12 Charging circuit for secondary battery
EP02770193A EP1425837B1 (en) 2001-09-14 2002-09-12 Charging circuit for secondary battery
PCT/JP2002/009362 WO2003026095A1 (en) 2001-09-14 2002-09-12 Charging circuit for secondary battery
US10/467,682 US7012405B2 (en) 2001-09-14 2002-09-12 Charging circuit for secondary battery
KR1020057022622A KR100611583B1 (en) 2001-09-14 2002-09-12 Charging circuit for secondary battery
CN2007101547773A CN101123365B (en) 2001-09-14 2002-09-12 Charging circuit for secondary battery
KR1020037014514A KR100572160B1 (en) 2001-09-14 2002-09-12 Secondary battery charging circuit
US11/259,186 US7205748B2 (en) 2001-09-14 2005-10-26 Charging circuit for secondary battery
US11/295,450 US7274171B2 (en) 2001-09-14 2005-12-07 Charging circuit for secondary battery
US11/755,226 US20070222420A1 (en) 2001-09-14 2007-05-30 Charging circuit for secondary battery

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CN101123365B (en) 2012-09-26

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