JP2011103706A - Battery pack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery pack that prevents terminal metal from being exhausted in a short period of time, even if the battery pack is immersed in sea water or fresh water with a body of an electronic apparatus and terminals are short-circuited. <P>SOLUTION: The battery pack 1a includes a secondary battery cell 2, a battery protection circuit 3, a switch circuit 4, and a variable resistor circuit 7. In the variable resistor circuit 7, when the battery pack 1a is separated from a charger, a resistance value between a voltage detection terminal 15 and the secondary battery cell 2 rises. Consequently, even if the voltage detection terminal 15 and a charging terminal 12 are short-circuited, the terminal metal is not exhausted in the short period of time because a current that flows becomes extremely less compared with a case where no variable resistance circuit 7 is provided. Alternatively, when the battery pack 1a is charged, the resistance value between the secondary battery cell 2 and the voltage detection terminal 15 becomes small, a voltage drop at FET 71 is suppressed minimally, so that a voltage of the secondary battery cell 2 can be detected accurately. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a battery pack used as a power source for portable electronic devices.

  Generally, portable electronic devices such as transceivers and mobile phones are equipped with a battery pack so that they can operate even in places where there is no power supply (see Non-Patent Document 1, for example). In many cases, the battery pack employs a secondary battery that can be charged and discharged in consideration of economic aspects. Typical secondary batteries include nickel-cadmium batteries, nickel-hydrogen batteries, lithium ion batteries, and the like.

  A conventional battery pack described in Non-Patent Document 1 will be described with reference to the circuit diagram of FIG. The battery pack 1b basically includes a secondary battery cell 2, a battery protection circuit 3, and a switch circuit 4.

  At the time of charging, the secondary battery cell 2 is connected to a charger (not shown) via two charging terminals 11 and 12 on the plus side / minus side. On the other hand, at the time of discharging, that is, when power is supplied to the electronic device, the secondary battery cell 3 is connected to a portable electronic device (not shown) via the two discharge terminals 13 and 14 on the plus side / minus side. .

  In addition to the charging terminals 11 and 12 and the discharging terminals 13 and 14 described above, a voltage detection terminal 15 for detecting the voltage of the secondary battery cell 2 is provided. By connecting the voltage detection terminal 15 to the voltage detection circuit of the charger, voltage control during charging is performed.

  The battery protection circuit 3 is a switch circuit when an excessive current flows due to a short circuit between the terminals of the secondary battery cell 2 for some reason, or when the secondary battery cell 2 is overcharged or overdischarged. The energization is cut off by 4 to protect the secondary battery. The battery pack 1b is provided with a backflow preventing diode 5 and a voltage detecting resistor 6.

  3 is a view of the battery pack 1b incorporating the circuit of FIG. 2 as viewed from the back, and FIG. 4 is a view showing a state in which the battery pack 1b is attached to a transceiver 20 which is a kind of portable electronic device. .

  Since the transceiver 20 may be soaked in seawater or fresh water during use, not only the transceiver body 21 but also the battery pack 1b attached to it adopts a waterproof structure.

  As shown in FIG. 3, the surface of the battery pack 1b is covered with a case 16 having a rectangular parallelepiped shape. The lowermost part of the battery pack 1b is wider than the upper part, and this part is exposed to the outside when the battery pack 1b is attached to the transceiver body 21, so that it has a waterproof structure. A ring-shaped packing 17 is disposed at the boundary. The discharge terminals 13 and 14 are exposed on the upper surface of the case 16, and the charging terminals 11 and 12 and the voltage detection terminal 15 are exposed on the lowermost part of the back surface.

  As shown in FIG. 4, a battery pack housing hole 22 is formed in the lower part of the back side of the main body 21 of the transceiver 20. The battery pack 1b is accommodated in the hole 22 by inserting the tip of the battery pack 1b into the hole 22 and moving it in the direction indicated by the arrow.

  A pair of terminals (not shown) for receiving power is provided on the upper portion of the hole 22 of the transceiver body 21. Power is supplied to the transceiver 20 by bringing the discharge terminals 13 and 14 exposed on the upper surface of the battery pack 1b into contact with these terminals.

  As shown in FIG. 4, when the screw 23 is rotated with the packing 17 pressed against the tip of the hole 22, a locking piece (not shown) provided at the tip of the screw 23 is engaged with the hole of the transceiver body 21. The battery pack 1b is attached to the transceiver 20. The opening of the hole 22 is waterproofed by the packing 17.

  The transceiver 20 can be charged with the battery pack 1b attached. Specifically, the transceiver 20 to which the battery pack 1b is mounted is placed on the charger, the charging terminals 11 and 12 of the battery pack 1b are brought into contact with a pair of charging terminals (not shown) of the charger, The voltage detection terminal 15 is brought into contact with the voltage detection terminal of the charger. Charging is performed in this state.

Transceiver (Product Number: IC-M36) Service Manual P2-P3, P23-P24

  Among the plurality of terminals of the battery pack 1b, the discharge terminals 13 and 14 provided on the upper portion of the case 16 are in the hole 22 of the transceiver main body 21 sealed by the packing 17, so that the transceiver 20 is immersed in seawater or fresh water. Even if it happens, there is no short circuit. On the other hand, the charging terminals 11 and 12 and the voltage detection terminal 15 provided at the lowermost part of the case 16 are exposed to the outside so as to be in contact with terminals on the charger side. Therefore, when the transceiver 20 is immersed in seawater or fresh water, the voltage detection terminal 15 exposed from the case 16 of the battery pack 1b and the negative charging terminal 12 are short-circuited, and the secondary battery cell 2 is discharged.

  In such a case, if the connection between the secondary battery cell 2 and the terminals 12 and 15 is cut off using a mechanical switch or an electronic switch circuit, the discharge of the secondary battery cell 2 can be prevented, but the circuit configuration is complicated. This leads to an increase in the cost of the battery pack. Therefore, the conventional battery pack 1b uses a high-resistance resistor of about 10 KΩ as the voltage detection resistor 6 so that the secondary battery cell 2 is not discharged in a short time even in such a case. (See FIG. 2).

  However, when the state immersed in seawater or fresh water lasts for a long time, the current flows between the voltage detection terminal 15 and the charging terminal 12 through the water. In this case, the terminal disappears and charging becomes impossible.

  The present invention has been made in view of such problems, and even when the battery pack is immersed in seawater or fresh water together with the electronic device body and the terminals are short-circuited, the terminal metal is not consumed in a short time. The purpose is to provide.

In order to achieve the above object, a battery pack according to the present invention has a built-in secondary battery cell including at least one secondary battery, a pair of positive / negative charging terminals connected to a charger, and A battery pack comprising a voltage detection terminal and a pair of positive / negative discharge terminals connected to an electronic device,
A variable resistance circuit is connected between the voltage detection terminal and the secondary battery cell,
The variable resistance circuit has a low resistance value when the pair of charging terminals and the voltage detection terminal are connected to the charger and charging is performed, and the pair of charging terminals and the voltage detection terminal are charged. The resistance value is increased when separated from the vessel.

Here, the variable resistance circuit is:
FET (Field Effect Transistor) connected between the secondary battery cell and the voltage detection terminal,
A resistor connected in parallel with the FET;
Preferably, the input side is connected to the positive charging terminal, the output side is connected to the gate of the FET, and the ground side is composed of a transistor connected to the negative charging terminal.

  Further, it is preferable to use a FET having an on-state internal resistance of 10Ω or less as the FET.

  In the present invention, a variable resistance circuit having a simple configuration is arranged between the voltage detection terminal and the secondary battery cell, and even when a short circuit occurs between the voltage detection terminal and the charging terminal, the flowing current is Therefore, the terminal metal is not consumed in a short time.

  Further, the variable resistance circuit of the present invention can be realized only by slightly changing the wiring pattern of the circuit board of the conventional battery pack, and thus has an advantage of suppressing the cost increase of the battery pack.

It is a circuit diagram of the battery pack concerning an embodiment of the invention. It is a circuit diagram of the conventional battery pack. It is the figure which looked at the conventional battery pack from the back side. It is a perspective view which shows the state which mounts | wears a transceiver with a battery pack.

  Hereinafter, a battery pack according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 shows a circuit configuration of a battery pack 1a according to the present embodiment. The battery pack 1a includes a secondary battery cell 2, a battery protection circuit 3, a switch circuit 4, and a variable resistance circuit 7.

  That is, the battery pack 1a is obtained by connecting the variable resistance circuit 7 between the secondary battery cell 2 and the voltage detection terminal 15 of the conventional battery pack 1b shown in FIG. In the figure, components having the same functions as those in FIG.

  The secondary battery cell 2 includes at least one secondary battery such as a lithium ion battery, and is usually configured by connecting a plurality of secondary batteries in series and / or in parallel (in the figure, lithium ion batteries). An example is shown in which two batteries are connected in series).

  The battery protection circuit 3 is used when the discharge terminals 13 and 14 of the secondary battery cell 2 are short-circuited for some reason and an excessive current flows, or when the secondary battery cell 2 is overcharged or overdischarged. The switch circuit 4 cuts off the energization to protect the secondary battery.

  The secondary battery cell 2 is connected to a charger through two charging terminals 11 and 12 on the plus side / minus side, and charging is performed. Further, the secondary battery cell 2 is connected to the portable electronic device via the two discharge terminals 13 and 14 on the plus side / minus side, and necessary power is supplied to the portable electronic device.

  The voltage detection terminal 15 is a terminal for detecting the voltage of the secondary battery cell 2. By connecting this terminal 15 to the voltage detection circuit of the charger, voltage control at the time of charging is performed. The purpose of providing the dedicated terminal 15 for detecting the voltage of the secondary battery cell 2 is to accurately detect the voltage of the secondary battery cell 2 without being affected by the voltage drop caused by the diode 5.

  The diode 5 is used to prevent the current from the secondary battery cell 2 from flowing back through the charging terminal 11. The resistor 6 is used to accurately measure the voltage between the terminals of the secondary battery cell 2, and is used in a form that divides the voltage together with the resistor provided in the charger or alone. The resistor 6 also exhibits a function of making it difficult for current to flow when a short circuit occurs between the voltage detection terminal 15 and the charging terminal 12.

  Next, the configuration and operation of the variable resistance circuit 7 will be described. The variable resistance circuit 7 basically includes an FET 71, a resistor 72, and a transistor 73.

  The FET 71 is connected between the positive side of the secondary battery cell 2 and the resistor 6. The resistor 72 is connected in parallel with the FET 71. The transistor 73 has an input side connected to the charging terminal 11, an output side connected to the gate of the FET 71, and a ground side connected to the negative charging terminal 12. The transistor 73 has a built-in bias resistor. Resistors 74 and 75 are resistors for voltage adjustment.

  The variable resistance circuit 7 has a low resistance value when the charging terminals 11 and 12 and the voltage detection terminal 15 are connected to a charger (not shown) and charging is performed, and these terminals are separated from the charger. The resistance value is sometimes increased.

  First, the operation of the variable resistance circuit 7 during charging will be described. When the battery pack 1a is connected to a charger and a voltage is applied to the charging terminal 11 on the plus side, a current flows through the transistor 73, and the current of the gate of the FET 71 connected to the output side of the transistor 73 is drawn. Turns on.

  At this time, the current from the secondary battery cell 2 flows to the voltage detection terminal 15 via the low resistance FET 71. As will be described later, since the voltage drop in the FET 71 is orders of magnitude smaller than the voltage drop in the resistor 6, it hardly affects the voltage of the secondary battery cell 2.

  Next, an operation when the charger is separated from the battery pack 1a and no voltage is applied to the charging terminal 11 will be described. Since no current flows through the transistor 73, no current is drawn into the gate of the FET 71, and the FET 71 is turned off. Therefore, when the battery pack 1 a is immersed in seawater or fresh water and the voltage detection terminal 15 and the charging terminal 12 are short-circuited, the current from the secondary battery cell 2 is a voltage via the high-resistance resistor 72 and the resistor 6. It flows to the detection terminal 15. As a result, the current flowing between the voltage detection terminal 15 and the charging terminal 12 is reduced, and the terminal metal can be prevented from being consumed in a short time due to corrosion.

  In the present embodiment, an FET whose on-state internal resistance is 10Ω or less is used as the FET 71, the resistance value of the resistor 72 is 470 KΩ, the resistance value of the resistor 6 is 10 KΩ, and the resistance values of the resistors 74 and 75 are 47 KΩ. It was.

  When charging the battery pack 1 a, the voltage of the secondary battery cell 2 is detected as a voltage between the voltage detection terminal 15 and the charging terminal 12. When the FET 71 having an on-state internal resistance of 10Ω or less is used, the resistance value of the FET 71 in the on-state is smaller by three digits or more than the resistance value 10 KΩ of the resistor 6. Therefore, when the voltage of the secondary battery cell 2 is measured, the voltage drop generated in the FET 71 can be almost ignored, so that accurate voltage measurement can be performed.

  On the other hand, in the state where the battery pack 1a is separated from the charger, the FET 71 is in an off state, so that the current from the secondary battery cell 2 flows to the voltage detection terminal 15 via the resistor 72 and the resistor 6. At this time, the resistance value between the secondary battery cell 2 and the voltage detection terminal 15 is 480 KΩ. On the other hand, in the case of the conventional battery pack 1b without the variable resistance circuit 7, the resistance value between the secondary battery cell 2 and the voltage detection terminal 15 is 10 KΩ.

  That is, by providing the variable resistance circuit 7, the resistance value between the secondary battery cell 2 and the voltage detection terminal 15 becomes 48 times. As a result, the current that flows when the voltage detection element 15 and the charging terminal 12 are short-circuited is reduced to about 1/50 compared to the conventional battery pack 1b.

  In the variable resistance circuit 7, when the transistor 73 is omitted and the charging terminal 11 is directly connected to the gate of the FET 71, if the leakage current from the diode 5 is large, the FET 71 may be turned on and malfunction. Therefore, it is necessary to use an element with a small leakage current as the diode 5. In this case, an Nch type FET 71 must be used.

  On the other hand, by guiding the current of the charging terminal 11 to the FET 71 via the transistor 73, the FET 71 is prevented from being turned on by the leakage current from the diode 5 even when no voltage is applied to the charging terminal 11. it can.

  The resistance value of the resistor 72 is preferably set to 10 to 100 times as compared with the resistance value of the resistor 6. The larger the resistance value of the resistor 6, the smaller the current that flows in the case of a short circuit, but on the contrary, the on-resistance when used for voltage detection during charging increases.

  As described above, the variable resistance circuit 7 has a high resistance value between the voltage detection terminal 15 and the secondary battery cell 2 when the battery pack 1a is separated from the charger. As a result, even when the voltage detection terminal 15 and the charging terminal 12 are short-circuited, the value of the flowing current is extremely small compared to the case without the variable resistance circuit 7, so that the terminal metal is not consumed in a short time.

  On the other hand, when the battery pack 1a is charged, the resistance value between the secondary battery cell 2 and the voltage detection terminal 15 is small, so that the voltage drop at the FET 71 is suppressed as much as possible, and the voltage of the secondary battery cell 2 is accurately determined. Can be detected.

  Further, the variable resistance circuit 7 is composed of a small number of parts and can be realized by slightly changing the wiring pattern of the circuit board of the conventional battery pack 1b, so that the cost increase of the battery pack 1a can be minimized.

  In the present embodiment, the variable resistance circuit 7 is configured using one FET and one transistor, but the present invention is not limited to this. As long as a similar function can be exhibited, another semiconductor element may be used, or a plurality of FETs and transistors may be combined.

  The battery pack according to the present invention is suitable as a power source for portable electronic devices that may be immersed in seawater or fresh water, and can also be used as a power source for electronic devices installed outdoors.

DESCRIPTION OF SYMBOLS 1a Battery pack 2 Secondary battery cell 3 Battery protection circuit 4 Switch circuit 5 Diode 6, 72, 74, 75 Resistor 7 Variable resistance circuit 11, 12 Charge terminal 13, 14 Discharge terminal 15 Voltage detection terminal 16 Case 17 Packing 20 Transceiver 21 Transceiver body 22 Battery pack accommodation hole

Claims (3)

Built-in secondary battery cell containing at least one secondary battery, plus / minus pair of plus / minus charging terminals connected to charger and voltage detection terminal, plus / minus connected to electronic device A battery pack comprising a pair of discharge terminals on the side,
A variable resistance circuit is connected between the voltage detection terminal and the secondary battery cell,
The variable resistance circuit has a low resistance value when the pair of charging terminals and the voltage detection terminal are connected to the charger and charging is performed, and the pair of charging terminals and the voltage detection terminal are charged. A battery pack, wherein the battery pack is configured to have a high resistance value when separated from the container. The variable resistance circuit is:
FET connected between the secondary battery cell and the voltage detection terminal,
A resistor connected in parallel with the FET;
2. The transistor having an input side connected to the positive charging terminal, an output side connected to the gate of the FET, and a ground side connected to the negative charging terminal. The battery pack described in 1.   The battery pack according to claim 1, wherein an FET having an on-state internal resistance of 10Ω or less is used as the FET.

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