Electricity: battery or capacitor charging or discharging – Battery or cell discharging – Regulated discharging
Reexamination Certificate
2001-08-14
2003-02-11
Toatley, Jr., Gregory J. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Battery or cell discharging
Regulated discharging
C324S433000
Reexamination Certificate
active
06518730
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to secondary batteries (e.g. nickel-hydrogen and nickel-cadmium) that exhibit a memory effect and more particularly to a power supply unit for detecting a memory effect in such batteries.
BACKGROUND OF THE INVENTION
For various types of electrical apparatus such as notebook-type personal computers (notebook-type PC), Minidisks (MD), and video cameras, there is an ongoing requirement to provide an increase in battery capacity as well as providing a decrease in thickness and weight. These types of electrical apparatus use a secondary battery that can be recharged many times. Nickel-hydrogen (NiMH) or nickel-cadmium (NiCd) batteries are widely used as the secondary battery providing relatively large capacity at a relatively inexpensive price.
When the nickel-hydrogen battery or nickel-cadmium battery is incompletely charged or is discharged before the battery is completely discharged, an apparent charge capacity is decreased and a “memory effect” occurs in which the continuously operating time is decreased. It is known that the capacity of a battery exhibiting the memory effect is almost returned to the original state by repeating complete charge and discharge. Thus, even if a memory effect occurs, it is possible to recover a battery by performing complete charge and discharge. However, it is necessary to detect a memory effect before performing complete charge and discharge.
As used for BQ2060 of Texas Instruments Inc. (former Benchmark Inc.), a currently-known memory-effect detection method counts the number of times a shallow discharge is performed and when shallow discharge is detected 20 times, indicates that a memory effect has occurred. This method is the main stream at present.
Another detection method is disclosed in Japanese Published Unexamined Patent Application No. 7-14613. Specifically, a complete charge of a secondary battery such as a nickel-cadmium battery is performed and then a large-current discharge is performed only for a predetermined short time to measure the then battery voltage (V). Then, the difference (RV−V) between the measured battery voltage (V) and a previously-stored refreshed voltage (RV) of a battery is compared with a predetermined voltage and when the difference is equal to or higher than the predetermined voltage, it is determined that a memory effect has occurred.
However, because the above method which is the main stream at present counts the number of incomplete discharges, a problem occurs that it is assumed that a memory effect occurs even if the memory effect does not actually occur or a memory effect cannot be detected though the memory effect occurs. Moreover, even if a memory effect occurs, when the battery is perfectly discharged, data for the total capacity of the battery is learned (updated). Therefore, a difference is produced between capacity data and actual capacity and this causes a capacity-data error.
Furthermore, the art disclosed in Japanese Published Unexamined Patent Application No. 7-14613 detects a memory effect by performing large-current discharge. In general, however, at a portion having a large capacity, a clear difference does not appear between initial characteristic and a characteristic when falling into a memory effect. Therefore, erroneous detection may occur. Moreover, to circulate a large current, it is necessary to use an exclusive circuit. When setting the exclusive circuit for an information terminal unit such as a notebook-type personal computer or a general electrical apparatus, the cost for setting the exclusive circuit becomes extremely high and therefore, it is not realistic to use this art.
The present invention seeks to solve the above problems and to more accurately detect occurrence of a memory effect while performing normal operation. The result can be communicated to a user, and the memory effect removed in accordance with a user request.
SUMMARY OF THE INVENTION
The present invention determines that a memory effect occurs when it is detected that a measured battery voltage is lower than an expected voltage value for a particular measured discharged current value. That is, a power supply unit to which the present invention is applied includes: a secondary battery for supplying power to the body circuit; a current measurement circuit for measuring a currently-discharged current value; a voltage measurement circuit for measuring a currently-discharged voltage value; and determination means for determining whether the currently-discharged voltage value measured for the currently-discharged current value measured when a detected battery capacity is equal to or less than a predetermined value is lower than a predetermined value. In this case, because the determination means compares whether a detected battery capacity is lower than a predetermined value with table information stored in a memory in accordance with a voltage value to a current value when the capacity of a secondary battery is equal to or lower than a predetermined value when the capacity of the secondary battery is not sufficient and determines that a memory effect occurs when the detected battery capacity is lower than the predetermined value, the determination means is preferable from the viewpoint that it is possible to more accurately determine whether a memory effect occurs.
Moreover, notification means notifies a user that a memory effect occurs when it is determined that the memory effect occurs. As a result, when the user requests removal of the memory effect, discharge from a secondary battery is continued.
Furthermore, an AC adapter for charging a secondary battery and supplying power to the body circuit is used. Therefore, when removing a memory effect, the supply of power from the AC adapter to the body circuit is stopped and discharge from the secondary battery is performed. When it is not desired to remove the memory effect, power is supplied from the AC adapter to the body circuit. According to these aspects of the present invention, a user can detect that a memory effect occurs. Therefore, it is possible to bring performance of a battery to its maximum through conditioning.
From another viewpoint, a power supply unit to which the present invention is applied includes: an AC adapter for supplying power to the body circuit from the AC adapter; a secondary battery which is charged by an output from the AC adapter and supplies power to the body circuit; memory-effect determination means for determining whether a memory effect occurs in accordance with a current value measured by a current measurement circuit and a voltage value measured by a voltage measurement circuit; and a stop circuit for the power to be supplied from the AC adapter to the body circuit when it is determined by the memory-effect determination means that a memory effect occurs and the memory effect is removed in accordance with the designation of a user.
In this case, the memory-effect determination means has storage means for storing a predetermined value at which it is determined that a memory effect occurs in accordance with the relation between current and voltage values, compares current and voltage values to be measured with the predetermined value stored in the storage means and determines whether a memory effect occurs. Moreover, the storage means stores different predetermined values according to a temperature condition in accordance with the relation between current and voltage values. Therefore, the storage means is preferable because the means can properly obtain and determine a memory-effect occurrence state depending on a temperature condition. For example, the storage means stores a specific voltage value to a range of discharged current values divided and classified in a predetermined range while a battery capacity ranges between 70% and 10% as table information.
Moreover, the present invention uses a secondary battery such as a nickel-hydrogen battery or nickel-cadmium battery for supplying power to an electrical apparatus by repeating charge and discharge, which includes: volta
Nakagawa Hiroshi
Nishio Tomonori
Odaohhara Shigefumi
Tsurukawa Noboru
International Business Machines - Corporation
Munoz-Bustamante Carlos
Toatley , Jr. Gregory J.
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