Electrical transmission or interconnection systems – Plural supply circuits or sources – Selective or optional sources
Reexamination Certificate
1998-12-28
2001-07-17
Ballato, Josie (Department: 2836)
Electrical transmission or interconnection systems
Plural supply circuits or sources
Selective or optional sources
C320S122000, C324S434000
Reexamination Certificate
active
06262494
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a battery unit and an information processing apparatus having the battery unit mounted therein. More particularly, this invention is concerned with a battery unit capable of monitoring the state (amount of remaining power or deterioration) of a cell with high precision and an information processing apparatus having the battery unit mounted therein.
2. Description of the Prior Art
Due to the trend toward downsizing information processing apparatuses, there is an increasing demand for portable apparatuses including notebook-type personal computers. In a portable apparatus, a battery is incorporated as a power source. When the portable apparatus is used in an environment in which an ac voltage cannot be obtained from the mains, it can be driven by a battery. More and more portable apparatuses are therefore including a secondary battery that can be used cyclically as a battery. A form of the secondary battery is a battery unit that is a battery pack having a plurality of cells connected in parallel with one another. This form is intended to cope with a large power consumption of an apparatus.
For detecting an amount of remaining power in such a battery unit, normally, the battery unit is connected to a main unit of an information processing apparatus. The battery unit supplies power to a load in the main unit. In other words, a no-load voltage provided by the battery unit is estimated based on a discharge current flowing into the load or a voltage produced by a cell. According to this technique for detecting an amount of remaining power, there is a problem that it is hard to detect an amount of remaining power accurately because a voltage varies depending on a change in current flowing through a load.
Moreover, since a plurality of cells is packed in the form of a battery unit, it is impossible to detect the state of the battery unit in units of a cell. If an amount of remaining power is unequal among the cells, part of a current to be supplied to a load may flow into a cell having a small amount of remaining power. This invites deterioration of a driving ability. Moreover, when the battery unit is charged, a phenomenon that a cell having a large amount of remaining power discharges towards a cell having a small amount of remaining power may take place. This poses a problem that an excess current may flow into the cell having a small amount of remaining power to eventually break down the cell.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a battery unit making it possible to check the state thereof accurately even when power is supplied to a load, and to monitor the state thereof even in units of a cell, and an information processing apparatus employing the battery unit.
For accomplishing the object, a battery unit in accordance with the first aspect of the present invention includes a plurality of cells connected in parallel with one another, and a switch connected to at least one of the cells. In this unit, a specific cell can be disconnected from a load by controlling the switch. By detecting the state of the specific cell in this state, the state of the cell can be detected correctly.
The battery unit may be provided with a control circuit for controlling the on or off state of the switch. Operating the switch can thus be automated.
The battery unit may be provided with a voltage detection terminal at which a voltage across the terminals of a specific cell is developed. The state of the specific cell can thus be checked based on the voltage output through the voltage detection terminal.
The voltage detection terminal can be connected between the switch and cells. By turning on or off the switch, discharge from a cell connected to the switch to the load is discontinued. This enables detection of a voltage released from the cell.
Furthermore, a plurality of switches may be included to be associated with the plurality of cells. In this case, the control circuit turns of any of the switches in response to an external control signal. Consequently, any one cell can be disconnected from the load, and a no-load voltage provided by the cell can be detected in units of a cell.
Furthermore, a selecting circuit may be interposed between one voltage detection terminal and the cells to be connected to the voltage detection terminal. The number of cells to be connected to the voltage detection terminal can be limited. Thus, a cell that is an object of inspection can be located.
Furthermore, the control circuit may be designed to control the selecting circuit in response to an external control signal. Thus, selection of cells to be connected to the voltage detection terminal is executed automatically.
Furthermore, the control circuit may control the selecting circuit so that a cell connected to a switch that is off will be selected. Consequently, the cell from which no power is supplied to the load is connected to the voltage detection terminal.
Furthermore, the switches may be designed to connect the cells to either the load or voltage detection terminal. Consequently, the switches for turning on or off the connections between the cells and load also serve as the switches for turning on or off the connections between the cells and voltage detection terminal. Thus, the number of switches can be decreased.
Furthermore, the control circuit may be designed to control the switches in response to an external control signal and connect any of the switches to the voltage detection terminal. Consequently, a no-load voltage provided by a cell can be detected in units of a cell.
A battery unit in accordance with the second aspect of the present invention includes a plurality of cells connected in parallel with one another, and a resistor connected in series with at least one of the cells. Consequently, discharge from a cell, to which the resistor is connected, to a load can be suppressed. A voltage produced by the cell can be detected independently of a current flowing through the load.
In the battery unit, the resistor may be a variable resistor. A resistance can be adjusted in order to control a discharge current flowing out of a cell. Thus, a cell for which a voltage across terminals thereof is detected can be selected.
Furthermore, the battery unit may be provided with a control circuit for controlling a resistance offered by the variable resistor. Thus, setting a resistance can be automated.
Furthermore, a voltage detection terminal may be interposed between the resistor and cells. In this case, the resistance to be offered by the resistor is increased in order to suppress a discharge current flowing into the load. A voltage nearly equal to a no-load voltage provided by the cell is developed at the voltage detection terminal. Consequently, a voltage across the terminals of the cell can be measured accurately.
Furthermore, a plurality of resistors may be included to be associated with the plurality of cells. In this case, the control circuit makes a resistance to be offered by any of the resistors larger than that to be offered by the other resistors in response to an external control signal. Thus, discharge from any cell to the load is suppressed. Consequently, the state of each cell in the battery unit can be checked in units of a cell.
Furthermore, the battery unit may be provided with a selecting circuit for selecting a cell to be connected to the voltage detection terminal. Thus, a cell that is an object of inspection can be located.
Furthermore, the control circuit may control the selecting circuit in response to an external control signal. Thus, the selecting circuit can be controlled automatically. Furthermore, the control circuit may be designed to control the selecting circuit so that a cell connected to a resistor that is set to a maximum resistance will be selected. Thus, a cell, having a discharge current which flows into the load limited by the resistor, can be connected to the voltage detection terminal.
According to the third aspect of the present invention, there is p
Ozawa Hidekiyo
Saeki Mitsuo
Takeda Yoshiro
Tsukuni Toshiaki
Armstrong Westerman Hattori McLeland & Naughton LLP
Ballato Josie
DeBeradinis Robert L.
Fujitsu Limited
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