JP2004349195A - Over discharge preventing circuit of lithium-ion secondary battery - Google Patents
Over discharge preventing circuit of lithium-ion secondary battery Download PDFInfo
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- JP2004349195A JP2004349195A JP2003147560A JP2003147560A JP2004349195A JP 2004349195 A JP2004349195 A JP 2004349195A JP 2003147560 A JP2003147560 A JP 2003147560A JP 2003147560 A JP2003147560 A JP 2003147560A JP 2004349195 A JP2004349195 A JP 2004349195A
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- Prior art keywords
- secondary battery
- ion secondary
- voltage
- circuit
- lithium ion
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 32
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 32
- 239000004065 semiconductor Substances 0.000 claims abstract description 22
- 230000007423 decrease Effects 0.000 claims description 12
- 230000002265 prevention Effects 0.000 claims description 10
- 238000007599 discharging Methods 0.000 claims description 7
- 230000005669 field effect Effects 0.000 claims description 3
- 239000003990 capacitor Substances 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000002457 bidirectional effect Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
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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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- Secondary Cells (AREA)
Abstract
Description
【０００１】
【発明の属する技術分野】
本発明は、電圧の低下により放電を停止させるリチウムイオン二次電池の過放電防止回路に関する。
【０００２】
【従来の技術】
リチウムイオン二次電池は、マイコンや各種の小型家電機器の電源として使用されており、その電圧は充電に伴って上昇し、放電に伴って低下する。リチウムイオン二次電池に負荷（機器）を接続して状態において、残容量がなくなってもさらに放電させると、電池の性能が著しく低下する。このような著しい電池の性能の低下を防ぐためには、残容量がなくなった時点で放電電流を遮断することが必要になる。
【０００３】
２つのサーミスタと２つの抵抗の直並列回路の組み合わせによる分圧回路にリチウムイオン二次電池の出力電圧を印加して、分圧回路の出力電圧を設定電圧と比較して放電末期電圧を補正することにより、電池の電圧が同じであっても、温度によって変化するリチウムイオン二次電池の残容量が少なくなったことを正確に検出できるようにした放電末期電圧の補正回路が提案されている（例えば、特許文献参照）。
【０００４】
【特許文献１】
特開２００２−２６０７４４号公報
【０００５】
【発明が解決しようとする課題】
しかし、上記従来の回路は、分圧回路の出力電圧を設定電圧より低下したか否かを比較判定するために比較ＩＣが必要であり、コストがかかると共に配置するためのスペースが必要になる。そのため、低コスト化、小型薄型化への対応が難しいという問題がある。
【０００６】
【課題を解決するための手段】
本発明は、上記課題を解決するものであって、電池電圧の低下による過放電の停止を、少ない素子による簡単な回路構成でコストの低減、小型薄型化を可能にするものである。
【０００７】
そのために本発明は、電圧の低下により放電を停止させるリチウムイオン二次電池の過放電防止回路であって、リチウムイオン二次電池と出力端子との間に接続されて放電電流をスイッチングする半導体制御素子と、出力側電圧によって前記半導体制御素子の動作バイアスを印加する動作バイアス回路とを備え、前記動作バイアス回路に非線形抵抗素子を直列に接続して前記出力側電圧の低下により前記半導体制御素子をオフにして放電を停止させるように構成したことを特徴とするものである。
【０００８】
さらに、前記動作バイアス回路は、複数の抵抗と前記非線形抵抗素子の直列接続回路からなる分圧回路であり、前記非線形抵抗素子は、定電圧ダイオードであり、前記半導体制御素子は、放電電流を流す極性の単方向半導体制御素子であり、逆極性に充電電流を流す単方向整流素子が並列接続され、あるいは電界効果トランジスタからなることを特徴とするものである。
【０００９】
【発明の実施の形態】
以下、本発明の実施の形態を図面を参照しつつ説明する。図１は本発明に係るリチウムイオン二次電池の過放電防止回路の実施の形態を示す図であり、ＢＡＴＴはリチウムイオン二次電池、ＴＲはトランジスタ（ＰＮＰ）、ＺＤは定電圧ダイオード、Ｄはダイオード、Ｃ１〜Ｃ４はコンデンサ、Ｒ１〜Ｒ３は抵抗を示す。
【００１０】
図１において、リチウムイオン二次電池ＢＡＴＴに対し、トランジスタＴＲは、出力端子との間に放電電流を流す極性に直列に接続され電圧の低下に伴い放電停止のスイッチング制御を行うＰＮＰ型の単方向半導体制御素子である。定電圧ダイオードＺＤは、電圧の低下に伴い放電停止のスイッチング制御を行う電圧を越えると定電圧を維持し、その電圧以下でオフになる非線形抵抗素子であり、抵抗Ｒ１、Ｒ２は、この定電圧ダイオードＺＤと出力側で直列接続され、トランジスタＴＲのベースバイアス回路を構成するものである。ダイオードＤは、トランジスタＴＲと逆極性に並列接続され、リチウムイオン二次電池の充電電流を流す単方向整流素子である。
【００１１】
リチウムイオン二次電池ＢＡＴＴは、残容量がなくなってもさらに放電させると、電池の性能が著しく低下する。このような著しい電池の性能の低下を招く電圧に合わせ、定電圧ダイオードＺＤ、抵抗Ｒ１、Ｒ２の値が選定され、その電圧以下で定電圧ダイオードＺＤが高抵抗値になりトランジスタＴＲにベース電流が供給されなくなってトランジスタＴＲは非導通状態となる。
【００１２】
過放電をしないように電池の電圧を比較等でモニタする従来の回路では、放電を停止させていても、モニタ回路にリチウムイオン二次電池ＢＡＴＴからその動作に必要な微小電流が供給されている。そのため、放電を停止した後であっても、結果的に僅かな電流でも放電が続けられることになる。本実施形態は、トランジスタＴＲの特性の飽和領域（最も電流の流れる電圧）を利用して、オン／オフを行うものであり、電圧が低下してオフにスイッチされると電流は流れなくなる。しかも、その動作バイアスを与える回路を出力側に接続することにより、トランジスタＴＲがオフになった状態では、ベースバイアス回路にも電流が流れなくなり、リチウムイオン二次電池ＢＡＴＴからの放電を完全に停止させることができる。しかも、ＩＣを用いることなく、限りなく半導体１個のコストと最小の回路部品搭載数で構成することができる。
【００１３】
なお、本発明は、上記実施の形態に限定されるものではなく、種々の変形が可能である。例えば上記実施の形態では、ＰＮＰトランジスタを用いたが、これらの回路をリチウムイオン二次電池ＢＡＴＴの（−）の給電ラインに設けることによりＮＰＮトランジスタを用いて構成することもでき、また、単方向半導体制御素子であるトランジスタとダイオードとの組み合わせに変えて、双方向半導体制御素子であるＦＥＴ（電界効果トランジスタ）を用いて構成することもできる。
さらに、動作バイアス回路に定電圧ダイオードを接続したが、サーミスタなど定電圧ダイオード以外の非線形抵抗素子を組み合わせて使用してもよい。
【００１４】
【発明の効果】
以上の説明から明らかなように、本発明によれば、電圧の低下により放電を停止させるリチウムイオン二次電池の過放電防止回路であって、リチウムイオン二次電池と出力端子との間に接続されて放電電流をスイッチングする半導体制御素子と、出力側電圧によって半導体制御素子の動作バイアスを印加する動作バイアス回路とを備え、動作バイアス回路に非線形抵抗素子を直列に接続して出力側電圧の低下により半導体制御素子をオフにして放電を停止させるように構成したので、特に低電圧での保護が必要とされ外部からの影響を避ける必要があるリチウムイオン二次電池において、ＩＣなどを用いた放電停止回路を設けなくても、トランジスタの動作可能電圧を利用して、リチウムイオン二次電池の電圧の低下によりそれ以上の放電を切断することができ、所謂負荷開放により、電気的な外部からの影響を遮断することができる。
【００１５】
したがって、リチウムイオン二次電池にとって、有効な保護が可能になり、保護のための回路の簡素化、コンパクト化が可能となる。しかも、従来のＩＣによる構成に比べて実質的に１個のトランジスタによる構成になるので、検出部を削減でき回路消費を最小の状態にし、素子搭載数を削減できるので、小型化、軽量化、コストの低減が可能になる。
【図面の簡単な説明】
【図１】本発明に係るリチウムイオン二次電池の過放電防止回路の実施の形態を示す図である。
【符号の説明】
ＢＡＴＴ…リチウムイオン二次電池、ＴＲ…トランジスタ（ＰＮＰ）、ＺＤ…定電圧ダイオード、Ｄ…ダイオード、Ｃ１〜Ｃ４…コンデンサ、Ｒ１〜Ｒ３…抵抗[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a circuit for preventing overdischarge of a lithium ion secondary battery that stops discharging due to a decrease in voltage.
[0002]
[Prior art]
Lithium-ion secondary batteries are used as power supplies for microcomputers and various small home appliances, and their voltage increases with charging and decreases with discharging. In a state where a load (equipment) is connected to the lithium ion secondary battery, if the battery is further discharged even when the remaining capacity is exhausted, the performance of the battery is significantly reduced. In order to prevent such a remarkable decrease in the performance of the battery, it is necessary to interrupt the discharge current when the remaining capacity is exhausted.
[0003]
The output voltage of the lithium ion secondary battery is applied to a voltage dividing circuit composed of a combination of two thermistors and two resistors in series and parallel, and the output voltage of the voltage dividing circuit is compared with a set voltage to correct the terminal discharge voltage. As a result, a circuit for correcting the terminal discharge voltage that can accurately detect that the remaining capacity of the lithium ion secondary battery that changes with temperature has decreased even when the battery voltage is the same has been proposed ( See, for example, patent literature).
[0004]
[Patent Document 1]
JP, 2002-260744, A
[Problems to be solved by the invention]
However, the above-described conventional circuit requires a comparison IC to compare and determine whether the output voltage of the voltage dividing circuit has dropped below the set voltage, which is costly and requires space for arrangement. Therefore, there is a problem that it is difficult to cope with cost reduction and reduction in size and thickness.
[0006]
[Means for Solving the Problems]
The present invention has been made to solve the above problems, and it is an object of the present invention to stop overdischarge due to a decrease in battery voltage and to reduce the cost and reduce the size and thickness with a simple circuit configuration using a small number of elements.
[0007]
Therefore, the present invention relates to an overdischarge prevention circuit for a lithium ion secondary battery that stops discharging due to a decrease in voltage, and is a semiconductor control that is connected between the lithium ion secondary battery and an output terminal to switch a discharge current. An operating bias circuit for applying an operating bias of the semiconductor control element by an output side voltage, a non-linear resistance element is connected in series to the operating bias circuit, and the semiconductor control element is reduced by a decrease in the output side voltage. It is characterized in that the discharge is turned off to stop the discharge.
[0008]
Further, the operation bias circuit is a voltage dividing circuit including a series connection circuit of a plurality of resistors and the nonlinear resistance element, the nonlinear resistance element is a constant voltage diode, and the semiconductor control element flows a discharge current. A unidirectional semiconductor control element having a polarity, wherein a unidirectional rectifying element for flowing a charging current in the opposite polarity is connected in parallel or is formed of a field effect transistor.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an embodiment of an overdischarge prevention circuit for a lithium ion secondary battery according to the present invention, wherein BATT is a lithium ion secondary battery, TR is a transistor (PNP), ZD is a constant voltage diode, and D is Diodes, C1 to C4 indicate capacitors, and R1 to R3 indicate resistors.
[0010]
In FIG. 1, for a lithium ion secondary battery BATT, a transistor TR is a PNP-type unidirectional transistor that is connected in series with a polarity that allows a discharge current to flow between the output terminal and the output terminal, and that performs switching control to stop discharging as the voltage decreases. It is a semiconductor control element. The constant voltage diode ZD is a non-linear resistance element that maintains a constant voltage when the voltage exceeds the voltage at which the switching control for stopping the discharge is performed with a decrease in the voltage, and turns off when the voltage is lower than the voltage. The diode ZD is connected in series on the output side to form a base bias circuit of the transistor TR. The diode D is a unidirectional rectifier that is connected in parallel with the transistor TR in reverse polarity and flows a charging current of the lithium ion secondary battery.
[0011]
Even if the remaining capacity of the lithium ion secondary battery BATT is exhausted, if the battery is further discharged, the performance of the battery is significantly reduced. The value of the constant voltage diode ZD and the resistances R1 and R2 are selected in accordance with the voltage which causes such a remarkable decrease in the performance of the battery. Below this voltage, the constant voltage diode ZD has a high resistance value, and the base current flows through the transistor TR. No longer supplied, the transistor TR becomes non-conductive.
[0012]
In a conventional circuit that monitors the voltage of a battery by comparison or the like so as not to overdischarge, even if the discharge is stopped, a minute current necessary for the operation is supplied from the lithium-ion secondary battery BATT to the monitor circuit. . Therefore, even after the discharge is stopped, the discharge can be continued even with a small current. In the present embodiment, the transistor TR is turned on / off by using a saturation region (a voltage at which a current flows most) of the characteristic of the transistor TR. When the voltage is reduced and the transistor TR is switched off, no current flows. Moreover, by connecting the circuit for applying the operating bias to the output side, no current flows to the base bias circuit when the transistor TR is turned off, and the discharge from the lithium ion secondary battery BATT is completely stopped. Can be done. In addition, without using an IC, the semiconductor device can be formed with an unlimited number of semiconductors at a low cost and a minimum number of circuit components.
[0013]
Note that the present invention is not limited to the above embodiment, and various modifications are possible. For example, in the above embodiment, a PNP transistor is used. However, by providing these circuits on the (−) power supply line of the lithium ion secondary battery BATT, the circuit can be configured using an NPN transistor. Instead of a combination of a transistor and a diode, which are semiconductor control elements, it is also possible to use an FET (field effect transistor) which is a bidirectional semiconductor control element.
Further, although a constant voltage diode is connected to the operation bias circuit, a non-linear resistance element other than a constant voltage diode such as a thermistor may be used in combination.
[0014]
【The invention's effect】
As is apparent from the above description, according to the present invention, there is provided an overdischarge prevention circuit for a lithium ion secondary battery that stops discharging due to a decrease in voltage, the circuit being connected between the lithium ion secondary battery and an output terminal. A semiconductor control element for switching the discharge current and an operation bias circuit for applying an operation bias of the semiconductor control element by an output side voltage. Is configured to turn off the semiconductor control element to stop the discharge. Therefore, particularly in a lithium ion secondary battery that requires protection at a low voltage and needs to avoid external influences, discharge using an IC or the like is performed. Even without a stop circuit, further discharge can be performed by lowering the voltage of the lithium ion secondary battery using the operable voltage of the transistor. Can cross, can block the effects of the so-called open load, from an electrical external.
[0015]
Therefore, effective protection is possible for the lithium ion secondary battery, and the circuit for protection can be simplified and downsized. In addition, since the configuration is substantially one transistor as compared with the configuration using a conventional IC, the number of detectors can be reduced, the circuit consumption can be minimized, and the number of mounted elements can be reduced. The cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of an overdischarge prevention circuit for a lithium ion secondary battery according to the present invention.
[Explanation of symbols]
BATT: Lithium ion secondary battery, TR: Transistor (PNP), ZD: Constant voltage diode, D: Diode, C1-C4: Capacitor, R1-R3: Resistance
Claims (5)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2003147560A JP4333907B2 (en) | 2003-05-26 | 2003-05-26 | Overdischarge prevention circuit for lithium ion secondary battery |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2003147560A JP4333907B2 (en) | 2003-05-26 | 2003-05-26 | Overdischarge prevention circuit for lithium ion secondary battery |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2004349195A true JP2004349195A (en) | 2004-12-09 |
| JP4333907B2 JP4333907B2 (en) | 2009-09-16 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2003147560A Expired - Fee Related JP4333907B2 (en) | 2003-05-26 | 2003-05-26 | Overdischarge prevention circuit for lithium ion secondary battery |
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| Country | Link |
|---|---|
| JP (1) | JP4333907B2 (en) |
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- 2003-05-26 JP JP2003147560A patent/JP4333907B2/en not_active Expired - Fee Related
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| JP4333907B2 (en) | 2009-09-16 |
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