JP2000295777A - Battery equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the number of components by using a fuse of a second protect circuit in place of a sense resistor which is an external component for monitoring charging and discharging currents. SOLUTION: In a second protect circuit 19, a V/D is disposed for each secondary battery to monitor the secondary battery voltage. The detection voltage of each V/D is set a little higher than that of a battery state monitoring circuit 18 to stop the function of a battery pack to keep it safe when the voltage reaches the detection voltage of the second protect circuit 19, in other words, when the secondary batteries which become uncontrollable by the battery state monitoring circuit 18 are overcharged. An amplifier 3 is for adjusting the voltage drop caused by a sense resistor 10 to the level readable by a microcomputer 5. The sense resistor 10 is a combined resistor of fuses 20, 22. By using the second protect fuses for the sense resistor used as an external component, the number of components can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery device 25A for a secondary battery, a circuit 18A required to monitor a battery condition such as a voltage and a charge / discharge current, and the battery condition monitoring circuit 18A and an external connection outside the battery device. Terminals 13A and 14A, switch elements 11A and 12A, secondary batteries 6A to 9A, sense resistors 10A and 2nd Prote
The present invention relates to a battery device 25A (hereinafter, referred to as a battery pack) including a ct circuit 19A and fuses 20A and 22A.

[0002]

2. Description of the Related Art A conventional battery pack 25 for a secondary battery
As A, an apparatus whose circuit block diagram is shown in FIG. 2 is known. This is a smart battery system (s
The present invention relates to a battery pack called a "mart Battery System" or the like. That is, the battery pack 25A includes a battery state monitoring circuit 18A, switch elements 11A and 12A, a sense resistor 10A, and secondary batteries 6A to 9A.

The battery state monitoring circuit 18A includes a microcomputer 5A, a battery voltage monitoring circuit 4A, and an amplifier 3A, and has a function of monitoring the voltage and charge / discharge current of the secondary battery. Such a battery pack 25A can communicate with the charger 17A or an external device such as the computer 15A or a load. In the second protection circuit 19A, a voltage detector (hereinafter referred to as V / D) is arranged for each secondary battery in order to monitor the secondary battery voltage. Second
The protection circuit including the protection circuit 19A, the fuses 20A and 22A, the resistors 21A and 23A, and the NchTr (N-channel transistor) 24A is hereinafter referred to as a second protection.

The second protect is the second protect as the name implies, and the function of the battery pack is stopped when the secondary battery, which cannot be controlled by the battery state monitoring circuit 18A, which is the first protect, is overcharged. , To ensure the safety of the battery pack. At this time, the overcharge is prevented by cutting the fuse, so that the battery pack cannot be used.

In the battery pack shown in FIG. 2, the sense resistor 10A is arranged between the negative terminal side of the secondary battery 9A and the negative terminal 14A of the battery pack. The sense resistor 10A monitors the voltage drop caused by the flow of the current by the built-in amplifier 3A, and monitors the charging current.

[0006]

In the conventional battery pack, since an external component is used for the sense resistor, there is a problem that the cost of the battery pack increases as the number of components increases.

[0007]

In order to solve the above-mentioned problems, the present invention reduces the number of components by using a second protection fuse instead of using an external component for the sense resistor, thereby reducing the number of components and the battery pack. Reduced costs.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention substitutes a second protected fuse in a battery pack instead of using an external component for a sense resistor for monitoring a charge / discharge current. Generally, the value of the sense resistor is several tens of mΩ, so the fuse of the second protection has a resistance of several tens of mΩ.

FIG. 1 shows a configuration example of a battery state monitoring circuit to which the present invention is applied and a battery pack using the same. An embodiment of the present invention will be described below with reference to FIG. In the battery pack, a plurality of secondary batteries 6 to 9 (for example, cells of a lithium ion battery) are connected in series. Further, the positive electrode of the secondary battery 6 is connected to a switch element 12 composed of an FET or the like. Switch element 11
And the switch element 12 are connected in series, and the switch element 11 is connected in series to the + terminal of the battery pack. The switch elements 11 and 12 are used as switch elements for controlling discharging from the battery pack and charging from the charger. To prohibit charging of the battery pack, the switch element 11 may be turned off. To prohibit discharge from the battery pack, the switch element 12 may be turned off. The switch element may be connected between the negative electrode of the secondary battery 9 and the negative terminal of the battery pack. At this time, it is necessary to appropriately change the type of the FET and the like in accordance with the change.

The secondary battery (6 to 9), the switching element 1
1, 12 and the sense resistor 10 are also connected to the battery state monitoring circuit 18, respectively. The battery state monitoring circuit 18 includes a microcomputer 5, a battery voltage monitoring circuit 4, an amplifier 3, a voltage regulator 1, and a voltage detection circuit 2. The power supplies such as the battery voltage monitor circuit 4, the voltage regulator 1, and the voltage detection circuit 2 are supplied from the voltage regulator 1, and the amplifier 3 calculates a value obtained by summing the battery voltages of the secondary batteries 6 to 9 (hereinafter, this value is referred to as the total battery Voltage).

The second protection circuit 19 has a V / D arranged for each secondary battery in order to monitor the secondary battery voltage. However, by making the detection voltage of V / D slightly higher than the detection voltage of the battery state monitoring circuit 18, when the detection voltage value of the second protection circuit 19 is reached, that is, the battery state monitoring circuit 18 cannot control the voltage. When the secondary battery becomes overcharged, the function of the battery pack is stopped and the safety of the battery pack is maintained. At this time, the NchTr 24 is controlled by the second protection circuit 19, and a large current is caused to flow through the resistors 21 and 23, thereby cutting the fuses 20 and 22 and preventing overcharging, so that the battery pack cannot be used.

The amplifier 3 adjusts the voltage drop generated by the sense resistor 10 to a level that can be read by the microcomputer 5, and the sense resistor 10 is a combined resistor of the fuses 20 and 22. Here, by replacing the sense resistor 10A used as an external component with the second protect fuse, the number of components was reduced and the cost of the battery pack was reduced accordingly.

When the fuse is cut when the secondary battery is overcharged and the fuse is cut, the sense resistance changes simultaneously. However, the function of the battery pack is lost when the fuse is cut. There is no problem even if the value changes. Generally, since the resistance value of the sense resistor 10 is as small as several tens of mΩ, the amplifier 3 amplifies the voltage at the sense resistor end and supplies it to the A / D port of the microcomputer 5.

[0014]

According to the present invention, the number of components and the cost of the battery pack are reduced by substituting the second protection fuse for the sense resistor instead of using an external component as described above.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a battery state monitoring circuit of the present invention and a battery pack using the same.

FIG. 2 is a circuit diagram showing a conventional battery state monitoring circuit and a battery pack using the same.

[Explanation of symbols]

 1 Voltage regulator 2 Voltage detection circuit 3 Amplifier 4 Battery voltage monitoring circuit 5 Microcomputer 6, 7, 8, 9 rechargeable battery 10 sense resistor 11, 12 switch element 16 load 17 charger 18 battery state monitoring circuit 19 secondary protection 20 22 fuse 21 23 resistance 24ch NchTr

Claims (1)

[Claims] 1. A charge / discharge control of a secondary battery connected in series via a switch element to an external terminal consisting of a positive terminal and one terminal of a battery device is performed by turning on and off the switch element, and A battery device using a second protect fuse for preventing overcharge of the secondary battery, wherein the fuse is used as a sense resistor for monitoring a charging current of the secondary battery. .