Method and apparatus including a current detector and a power source control circuit for charging a number of batteries

• US 5,557,189 A
• Filed: 12/09/1994
• Issued: 09/17/1996
• Est. Priority Date: 12/24/1993
• Status: Expired due to Term

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Suzuki, Mamoru, Iijima, Minoru, Fujiwara, Nobuhiro, Ishihama, Yasuyuki
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): Law, Patrick B.
• Application Number:
  US08/352,618
• Time in Patent Office: 648 Days
• Field of Search: 320/6, 320/15, 320/17, 320/18, 320/22, 320/23, 320/24
• US Class Current: 320/119
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y10S 320/22 Line impedance, e.g. resistor

Abstract

A battery charging apparatus for charging the electricity from a current source to a cell includes a variable resistor in parallel with the cell, a cell voltage detection unit for detecting the current voltage value of the cell and a comparator for comparing the current voltage value to a pre-set voltage value. The resistance value of the variable resistor is controlled responsive to the results of comparison so that the current from the current source is caused to flow through both the cell and the variable resistor with progress in the charging of the cell. The current is prevented from flowing through the cell when the cell is fully charged, so that overcharging is eliminated. If plural cells are charged in series, the control operation of not causing the current to flow through the fully charged cell can be carried out for each of the cells, so that integrated charging may be continued until all of the cells are fully charged thus shortening the cell charging time.

Claims

1. A battery charging apparatus for charging a plurality of cells comprising:

a plurality of charging units each connected to a respective one of a plurality of cells, each charging unit having current changing means connected in parallel with a respective cell for changing the current supplied to the cell, cell voltage detection means for detecting a voltage of the cell, pre-set voltage outputting means for outputting a pre-set voltage indicating a pre-set voltage value of the cell, and comparator-control means for comparing the voltage of the cell detected by said cell voltage detection means to the pre-set voltage from said pre-set voltage outputting means for detecting a present voltage of the cell with respect to said pre-set voltage, said comparator-control means controlling said current changing means so that the current flowing through the current changing means is increased as the present voltage value of the cell approaches the pre-set voltage, wherein said plurality of charging units are connected in series with one another;

a power source circuit having a variable output current connected to the plurality of charging units;

a plurality of first current detection means each associated with the current changing means of each charging unit for detecting the current value flowing through each current changing means;

second current detection means for detecting the output current value of said power source circuit; and

power source circuit control means for detecting a minimum current value among current values of said current changing means based upon the detection output of each first current detection means and for controlling said power source circuit so that an output current value of the power source circuit becomes a current value equal to the output current value from the power source circuit less the minimum current value.

2. A battery charging apparatus for charging a plurality of cells comprising:

a plurality of charging units each connected to a respective one of a plurality of cells, each charging unit having current changing means connected in parallel with a respective cell for changing the current supplied to the cell, cell voltage detection means for detecting a voltage of the cell, pre-set voltage outputting means for outputting a pre-set voltage indicating a pre-set voltage value of the cell, and comparator-control means for comparing the voltage of the cell detected by said cell voltage detection means to the pre-set voltage from said pre-set voltage outputting means for detecting a present voltage of the cell with respect to said pre-set voltage, said comparator-control means controlling said current changing means so that the current flowing through the current changing means is increased as the present voltage value of the cell approaches the pre-set voltage, wherein said plurality of charging units are connected in series with one another;

a power source circuit having a variable output current connected to the plurality of charging units;

a plurality of first current detection means each associated with the current changing means of each charging unit for detecting the current value flowing through each variable current means;

second current detection means for detecting the output current value of said power source circuit; and

power source circuit control means for detecting the maximum current value among current values of said current changing means based upon each detection output of each first current detection means and for generating a first subtraction current value by subtracting a pre-set maximum load value indicating a maximum current value capable of flowing through said variable current means from said maximum current, said power source circuit control means detecting a polarity of the first subtraction current value and generating a second subtraction current value by subtracting said first substraction current value from an output current value of the power source circuit as detected by said second current detection means, said power source control means also controlling said power source circuit so that an output current value of the power source circuit becomes equal to said second subtraction current value only when the first subtraction current value is of a positive polarity.

3. A method for charging a plurality of cells using a power source circuit comprising the steps of:

controlling a plurality of variable current means connected in parallel to said plurality of cells for varying a current supplied to said cells so that the current flowing through said variable current means is gradually increased as a present voltage value approaches a pre-set voltage value;

detecting the current values of said variable current means and detecting a minimum current value from among said current values and an output current value of said power source circuit;

generating a subtraction current value by subtracting the minimum current value of said variable current means from the output current value of the power source circuit; and

controlling said power source circuit so that the output current value of said power source circuit becomes equal to said subtraction current value.