Electricity: battery or capacitor charging or discharging – Battery or cell charging – With detection of current or voltage amplitude
Reexamination Certificate
1999-11-29
2001-05-29
Tso, Edward H. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Battery or cell charging
With detection of current or voltage amplitude
Reexamination Certificate
active
06239581
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a battery device (hereinafter referred to as “battery pack”) including a circuit for which the monitoring of a battery state such as a voltage across a secondary battery or a charging or discharging current is required, a battery state monitoring circuit, an external connection terminal to the exterior of the battery device, a switching element, the secondary battery and a sense resistor.
Also, the present invention relates to a battery state monitoring circuit and a battery device which have a high accuracy in detecting an over-current and controls which the discharge current by detection of a voltage between both ends of the sense resistor.
2. Description of the Related Art
As a conventional battery state monitoring circuit, there has been known a device shown in a circuit block diagram of FIG.
2
. The structure of this type is disclosed, for example, in Japanese Patent Unexamined Publication No Hei 9-312172, “A battery pack, a charger and a charging system as well as a charging method”. This publication relates to a battery pack which is called a “smart battery system” or the like. In other words, this is a battery pack having a function of monitoring a voltage across a secondary battery or a charging or discharging current by use of a microcomputer and which conducts communication with a load such as the charger or the computer.
The use of the battery pack thus structured makes it possible to recognize the battery state through communication with a charger, a microcomputer within a personal computer, a load or the like. By use of this information, the display of a remaining capacity of the battery, the termination of charging and discharging and so on are accurately conducted.
FIG. 2
shows a conventional battery state monitoring circuit
18
A and a conventional battery device which is made up of at least an external terminal made up of a plus terminal
1
A and a minus terminal
2
A which connect the battery state monitoring circuit
18
A, a charger and so on, and a switching element
11
A that controls a discharge current. In the conventional battery state monitoring circuit
18
A and the conventional battery device, a voltage Vd between both ends of the switching element
11
A (for example, MOS-FET) is detected by a microcomputer to turn off the switching element
11
A so that charging batteries
6
A to
8
A are prevented from allowing an excessive current to flow. Reference
3
A denotes an operational amplifier;
5
A, a microcomputer for calculating the remaining capacity of the charging batteries
6
A to
8
A through communication with the battery state monitoring circuit
18
A;
16
A, a load connected to the battery device;
17
A, a charger connected to the battery device;
19
A, a cut-out circuit for cutting out charging/discharging current paths of the charging batteries
6
A to
8
A by the battery state monitoring circuit
18
A; and
20
A, a selecting circuit for determining which battery is selected among the charging batteries
6
A to
8
A.
The conventional battery state monitoring circuit
18
A and the conventional battery device suffer from a problem in that accuracy of over-current detection is low because the on-resistance (a resistor during energization) of the switching element
11
A (for example, a MOS-FET) has a fluctuation in manufacture, and a (gate) voltage dependency, a temperature characteristic and so on are low.
According to the present invention, there is provided a battery state monitoring circuit and a battery device for detecting an over-current by detecting a voltage between both ends of a sense resistor. Further, provision of means for holding an over-current detection signal allows prevention of the oscillation of a switching element.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above, and therefore an object of the present invention is to detect an over-current by using a sense resistor and detecting a voltage between both ends of the sense resistor.
REFERENCES:
patent: 5469071 (1995-11-01), Obata
Adams & Wilks
Seiko Instruments Inc.
Tso Edward H.
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