| Method and apparatus for battery charging with constant current, constant voltage, and pulsed charging -> Monitor Keywords |
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Method and apparatus for battery charging with constant current, constant voltage, and pulsed chargingMethod and apparatus for battery charging with constant current, constant voltage, and pulsed charging description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060192531, Method and apparatus for battery charging with constant current, constant voltage, and pulsed charging. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This patent application is a continuation application of U.S. patent application Ser. No. 10/626,732, filed on Jul. 25, 2003, which claims priority from Japanese patent application; No. JPAP2002-221390, filed on Jul. 30, 2002 in the Japanese Patent Office, the entire disclosure of both of which are herein incorporated by reference. FIELD OF THE INVENTION [0002] The present invention relates to a method and apparatus for battery charging, and more particularly to a method and apparatus for battery charging to a nonaqueous second battery efficiently using constant current charging, constant voltage charging, and pulse charging in combination. BACKGROUND OF THE INVENTION [0003] Conventionally, continuous charging and pulse charging are common methods for charging a nonaqueous second battery such as a lithium ion battery, an Ni-MH battery, etc. Continuous charging may be grouped into CC (constant current) charging, CV (constant voltage) charging, and CCCV (constant-current constant-voltage) charging, which combines the CC charging and the CV charging. In the charging of a nonaqueous second battery, it is necessary to exercise due care to avoid an excess charging voltage exceeding a predetermined voltage since such an excessive charging voltage considerably deteriorates the battery performance. [0004] Thus, in order to avoid excessive charging voltage, the CCCV charging is generally used as the continuous charging method. In the CCCV charging method, charging with a constant current is performed at an early stage of the charging to the second battery and charging with a constant voltage is subsequently performed after a battery voltage of the second battery reaches a predetermined voltage. When the charging current (also referred to herein as "charge current" and "battery current") is reduced to a predetermined value, the second battery is in a fully-charged state and the charging is completed. One advantage of this method is the possibility of rapid charging by setting the charging current used in the constant current charging during the early stage of the charging to a relatively large value. Another advantage is the prevention of deterioration of the second battery due to application of excessive voltage since the charging mode is shifted from CC charging to CV charging when the battery voltage of the second battery reaches a predetermined voltage. [0005] However, when the constant current used in the initial charging stage is set to an excessively large value, a heat production by the second battery becomes large, which causes several problems: a reduction of charging efficiency, an acceleration of deterioration with respect to the second battery, etc. On the other hand, pulse charging has an advantage of less deterioration to the second battery because pulse charging is provided with pause times at certain intervals during the charging period, which increases efficiency of electrochemical changes. Additionally, pulse charging allows a relatively large charging current and therefore, is suitable for rapid charging as well. [0006] For example, Japanese Laid-Open Patent Application Publication No. 2001-169471 describes a second battery charging apparatus that features advantages of both continuous charging and pulse charging. This apparatus attempts to avoid over-charging while suppressing heat production of the second battery. That is, the continuous charging is performed during the initial charging and the charging mode is switched to the pulse charging when the battery voltage in the charging exceeds a predetermined voltage V1 depending on battery temperature. When the battery voltage with an open circuit in pulse charging exceeds a predetermined voltage V3, the mode is switched from the pulse charging to the continuous charging. Then, the charging is stopped when the battery voltage in the second battery reaches a predetermined voltage V2. [0007] For such a charging apparatus, miniaturization has increasingly been an issue recently, as mobile equipment such as cellular phones and the like using a second battery becomes widespread. In particular, charging apparatus for cellular phones are often carried along with a cellular phone. Such mobility requires a relatively short charging time to make the cellular phone operable and also requires a compact and light body producing less heat. The charge required to make the cellular phone operable may not be a full charge. The charge time to reach less than fully-charged state may be correspondingly less than the time to fully charge the second battery. [0008] However, conventional charging apparatus have been designed with a view mainly to reducing a charging time to the full-charge state and/or suppressing a temperature rise of the battery. To reduce the charging time, it is necessary to charge with a relatively large current. As a result, the charging apparatus produces a relatively large amount of heat and accordingly the size of the charging apparatus may become large. Since the temperature of the second battery rises, a temperature detection mechanism is additionally needed, resulting in an increase of the size and complexity of the apparatus itself. In addition, charging with such large current often accelerates deterioration of ionization with respect to the second battery. BRIEF SUMMARY OF THE INVENTION [0009] The present invention provides battery charging techniques capable of performing a quick charge to a second battery while suppressing heat production and deterioration of the second battery. [0010] In one example, a novel second battery charging apparatus includes a voltage detecting circuit, a current detecting circuit, a charging circuit, and a charge control circuit. The voltage detecting circuit detects a battery voltage of the second battery and outputs a signal in response to the battery voltage detected. The current detecting circuit detects a battery current supplied to the second battery and outputs a signal in response to the battery current detected. The charging circuit controls a current supply to the second battery to perform the charging of the second battery until the battery voltage detected by the voltage detecting circuit becomes substantially equal to a battery voltage predetermined in response to a first input control signal applied thereto also such that the charging current detected by the current detecting circuit becomes substantially equal to a charging current predetermined in response to a second input control signal applied thereto. The charge control circuit instructs the charging circuit by sending the input control signals to set the battery voltage and the charge current in response to a voltage indicated by the signal output from the voltage detecting circuit. [0011] The charge control circuit may instruct the charging circuit to perform a constant current charging in which a charging is performed flowing a first constant current to the second battery and subsequently another charging is performed flowing a second constant current greater than the first current to the second battery when the battery voltage of the second battery is smaller than a second pre-set voltage. Further, the charge control circuit may instruct the charging circuit to alternately flow a second constant current to the second battery and pause the flow of the second constant current to the second battery, for a pre-set time. Pausing the second constant current flow stops the charging current to the second battery. [0012] The charge control circuit may instruct the charging circuit to control the charging current flowing to the second battery such that the battery voltage becomes substantially equal to a third constant voltage during the constant current charging during the pulse charging cycle and also such that the battery voltage becomes substantially equal to the first constant voltage smaller than a third constant voltage during the pause during the pulse charging cycle. [0013] The charge control circuit may instruct the charging circuit to perform the constant current charging to supply the second constant current to the second battery when the battery voltage becomes substantially equal to a third pre-set voltage greater than the second pre-set voltage and also to perform the constant voltage charging to control the charging current such that the battery voltage becomes substantially equal to the third constant voltage when the battery voltage becomes substantially equal to a fourth pre-set voltage greater than the third pre-set voltage. [0014] The charge control circuit may instruct the charging circuit to control the charging current flowing through the second battery such that the battery voltage becomes substantially equal to the third constant voltage during the constant current charging before pulse charging is performed. [0015] The charge control circuit may instruct the charging circuit to control the charging current flowing through the second battery such that the battery voltage becomes substantially equal to the first constant voltage when the battery voltage is smaller than the first pre-set voltage which is smaller than the second pre-set voltage. The charge control circuit may further instruct the charging circuit to control the charging current flowing through the second battery such that the battery voltage becomes substantially equal to the second constant voltage, which is smaller than the third constant voltage and greater than the first constant voltage, during constant current charging before pulse charging is performed. [0016] The charging circuit may include a constant voltage generating circuit, a signal switching circuit, a voltage switching circuit, a control transistor, and a control circuit. The constant voltage generating circuit generates first, second, and third constant voltages. The voltage switching circuit selects and outputs one of the first and third constant voltages output from the constant voltage generating circuit in response to the control signals from the charge control circuit. The control transistor outputs a current to the second battery in response to an input control signal applied thereto. The control circuit controls the control transistor such that the battery voltage represented by a signal output from the voltage detecting circuit becomes substantially equal to a voltage represented by a signal output from the voltage switching circuit and such that the charging current represented by a signal output from the current detecting circuit becomes substantially equal to a constant current represented by a signal output from the signal switching circuit. [0017] The above-mentioned charging apparatus may further include a charge-end detecting circuit that determines an event that charging is completed relative to the second battery and outputs a predetermined signal when the charging current detected by the current detecting circuit becomes lower than the first constant current. In this case, the charge control circuit causes the charging circuit to stop charging upon receiving the signal indicative of a charge-end output from the charge-end detecting circuit. [0018] The first constant voltage may be a voltage greater than an over discharge voltage of the second battery and the third constant voltage may be a voltage substantially equal to a full charge voltage of the second battery. [0019] The current detecting circuit may include a resistor and a current detector. The resistor passes the charging current to be supplied to the second battery. The current detector detects the charging current based on a voltage across the resistor and outputs a signal in response to the detected charging current. In this case, the voltage detecting circuit, the current detector of the current detecting circuit, the charge control circuit, the charge-end detecting circuit, and several components of the charging circuit including the constant voltage generating circuit, the voltage switching circuit, the constant current reference signal generating circuit, the signal switching circuit, and the voltage switching circuit are integrated into a single integrated circuit chip. [0020] The current detecting circuit may include a resistor and a current detector. The resistor passes the charging current to be supplied to the second battery. The current detector detects the charging current based on a voltage across the resistor and outputs a signal in response to the detected charging current. In this case, the voltage detecting circuit, the current detector of the current detecting circuit, the charge control circuit, the charge-end detecting circuit, the and several components of the charging circuit including the constant voltage generating circuit, the voltage switching circuit, the constant current reference signal generating circuit, the signal switching circuit, and the voltage switching circuit are integrated into a single integrated circuit chip. Continue reading about Method and apparatus for battery charging with constant current, constant voltage, and pulsed charging... 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