Electricity: battery or capacitor charging or discharging – Battery or cell charging – Pulsed
Reexamination Certificate
2000-12-08
2001-10-23
Toatley, Jr., Gregory J (Department: 2838)
Electricity: battery or capacitor charging or discharging
Battery or cell charging
Pulsed
C320S162000
Reexamination Certificate
active
06307353
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a secondary battery apparatus having a secondary battery and a charge controller, and more particularly to a secondary battery apparatus which can reliably charge a secondary battery to a fully charged state for a short time in any environment in which a charge current and an ambient temperature may vary.
2. Background Art
Some electronic devices such as a notebook-size personal computer and so on contain a secondary battery apparatus. This type of secondary battery apparatus includes a secondary battery comprised of a lithium ion battery, a Ni—Cd battery, a Ni—MH battery or the like. The secondary battery functions as a driving power supply when an electronic device is used in an environment in which the electronic device cannot be connected to an external power supply, for example, a commercial power supply. When the battery voltage is reduced as the secondary battery is being used, the secondary battery is charged using a charge power supply (for example, a power supply unit of an electronic device connected to a commercial power supply). The charging of the secondary battery, however, is likely to degrade the battery performance and safety unless the charging is properly carried out.
Thus, the secondary battery apparatus comprises a charge control function for controlling the charging of the secondary battery such that the charging is properly carried out. For example, the charge control function controls the charging such that the secondary battery is charged with a constant current in an initial charge period in which the battery voltage is lower, and is charged with a constant voltage after a predetermined battery voltage has been reached. However, such a constant current/constant voltage charging technique causes a large amount of heat to be generated from a charge power supply, and requires a large charge power supply, thereby causing difficulties in responding to the need for a reduction in size and weight of electronic devices and suppression of the amount of generated heat.
Another charge control technique charges a secondary battery with a constant current while monitoring a battery temperature, taking advantage of the fact that the battery temperature rises as the secondary battery is being charged more. This charge control technique, however, may be affected by an ambient temperature to result in over charging or insufficient charging. In addition, the battery temperature rises due to the heat generated inside the secondary battery, resulting from the continuous charging with a constant current, possibly leading to degraded battery performance.
Also, when a charge power supply for use in charging a secondary battery of a secondary battery apparatus is utilized as a driving power supply for an electronic device, the operation of the electronic device (for example, a hard disk drive built in the electronic device) during a charging process may cause variations in load of the charge power supply to adversely affect the operation of the electronic device as well as the charging of the secondary battery. For example, when the charge power supply has a small size power supply capacity, the operation of the electronic device will become unstable. Also, the charge current may vary with the operation of the electronic device, and a contact resistance at a connector connecting the electronic device with the secondary battery apparatus may vary due to mechanical vibrations caused by the operation of the electronic device. Such variations in the charge current and contact resistance may result in insufficient charging of the secondary battery.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a secondary battery apparatus which is capable of reliably and efficiently charging a secondary battery to a fully charged state in a short time without being affected by variations in a charge current or an ambient temperature.
It is another object of the present invention to provide a secondary battery apparatus which is capable of suppressing the heat generated in a charge power supply for use in charging a secondary battery and of charging the secondary battery with a small size charge power supply.
A secondary battery apparatus according to the present invention comprises a secondary battery, a switch element provided in series in a charge path of the secondary battery, a voltage detector for detecting a terminal voltage of the secondary battery, a full charge detector for detecting the secondary battery having reached a fully charged state, and a charge controller for controlling charging of the secondary battery by conducting or blocking the switch element. The charge controller includes a pulse charging starting unit for starting a conducting/blocking operation of the switch element at predetermined periods to start pulse charging the secondary battery when the terminal voltage exceeds a first set voltage during the charging of the secondary battery, a pulse charging stopping unit for stopping the pulse charging while maintaining the switch element in a conductive state when the terminal voltage has reached a second set voltage during a switch element blocking period of the pulse charging, and a charging stopping unit for blocking the switch element to stop charging subsequent to the pulse charging when the full charge detector detects the fully charged state of the secondary battery during the charging subsequent to the pulse charging.
The secondary battery apparatus according to the present invention switches a charging mode from continuous charging to pulse charging when the terminal voltage (charge voltage) of the secondary battery, which increases as the charging of the secondary battery is advanced, has reached the first set voltage, and then switches the charging mode from the pulse charging to the continuous charging when the charge voltage has reached the second set voltage close to full charge, thereby carrying out the charging while the charge voltage is properly managed from the starting of the charging to the fully charged state. As a result, it is possible to prevent insufficient charging and over charging, and to prevent degraded battery performance and safety due to improper charging.
Also, when a power supply unit of an electronic device is utilized as a charge power supply, the electronic device, if operated during the charging, may cause fluctuations in the charge current or a change in the connecting state between the electronic device and the secondary battery apparatus. The present invention, however, properly manages the charge voltage in step with the advancement of the charging, so that proper charging is done even in such an environments and is less susceptible to the influence of ambient temperature.
Also, according to the present invention, while the secondary battery is being charged, the charging mode is switched from continuous charging to pulse charging or from pulse charging to continuous charging as the charge voltage increases, and in particular, the heat generated inside the secondary battery and the heat generated from the charge power supply are suppressed during the pulse charging. Thus, the secondary battery can be efficiently, safely and reliably charged to the fully charged state in a short time. Also, even when a small charge power supply is used, the secondary battery can be properly charged.
Preferably, the charge controller blocks the switch element when the terminal voltage of the secondary battery has reached an abnormally high third set voltage during the charging of the secondary battery. According to this preferred aspect, when the charge voltage abnormally increases, the charging of the secondary battery is prohibited, thereby protecting the secondary battery from an excessive charge voltage, thus making it possible to prevent degraded battery performance.
Preferably, the full charge detector comprises a temperature sensor for detecting a temperature of the secondary battery (battery temperature), and detects the
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Toatley Jr. Gregory J
Toshiba Battery Co., Ltd.
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