Power supply apparatus with chargeable battery and charge/discharge method

• US 6,445,164 B2
• Filed: 01/18/2001
• Issued: 09/03/2002
• Est. Priority Date: 02/20/1998
• Status: Expired due to Fees

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Kitagawa, Seiya
• Primary Examiner(s): TOATLEY, GREGORY J
• Application Number:
  US09/761,754
• Publication Number:
  US 20010007417A1
• Time in Patent Office: 593 Days
• Field of Search: 320/128, 320/134, 320/126, 320/119, 320/162
• US Class Current: 320/134
• CPC Class Codes: H02J 7/0013 acting upon several batteries simultaneously or sequentially H02J7/1423 takes precedence
• CPC Class Codes: H02J 7/0068 Battery or charger load switching, e.g. concurrent charging and load supply H02J7/0013 takes precedence
• CPC Class Codes: H02J 7/34 Parallel operation in networks using both storage and other dc sources, e.g. providing buffering H02J7/14 takes precedence

Abstract

The present invention provides a battery charging/discharging method for effectively using the battery energy of a power supply apparatus with a plurality of chargeable batteries. The power supply apparatus in which batteries are connected in parallel to the node of an external power source and a load comprises a charge/discharge monitor unit for judging whether the external power source is in a state where a load is driven and sufficient voltage to charge the batteries is outputted or in a state where sufficient voltage is not outputted and a discharge current should be supplied from the batteries to the load, switches inserted in series with each of the batteries, and an on/off control unit for controlling the on/off operation of the switches according to the output of the charge/discharge monitor unit and the charging/discharging state of each battery.

Claims

1. A power supply apparatus in which a plurality of chargeable batteries are connected in parallel between the node of an external power source, and a load, and the common ground of the external power source and the load, comprising:

charge/discharge monitoring means for judging whether the external power source is in a charging state when the load is driven and a sufficient voltage for charging the batteries is outputted, or in a discharging state when a sufficient voltage is not outputted and a discharging current should be supplied from the chargeable batteries to the load;

switch means connected in series to each of the plurality of batteries; and

on/off controlling means for controlling the on/off operation of the switches according to the output of the charge/discharge monitoring means and the charging/discharging state of each of the plurality of batteries, further comprising;

current detecting means for detecting the current flow in each of said plurality of batteries;

charge completion detecting means for detecting the charging completion state of each of said plurality of batteries from the output of the current detecting means; and

voltage comparing means for comparing the voltages of said plurality of batteries, and

wherein when said charge/discharge monitoring means judges that said external power source is in a charging state,

said on/off controlling means performs a first control of switching on only said switch corresponding to a battery with a voltage judged to be the lowest by the voltage comparing means, and

then, when the charge completion detecting means detects the charge completion of said battery with the lowest voltage, said on/off controlling means performs a second control of switching off the switched-on switch and a third control of switching on only said switch corresponding to a battery with a voltage judged to be the lowest by the voltage comparing means of the remaining batteries of which the charging completion is not detected out of said plurality of batteries.

2. A power supply apparatus in which a plurality of chargeable batteries are connected in parallel between the node of an external power source and a load, and the common ground of the external power source and the load, comprising:

charge/discharge monitoring means for judging whether the external power source is in a charging state when the load is driven and a sufficient voltage for charging the batteries is outputted, or in a discharging state when a sufficient voltage is not outputted and a discharging current should be supplied from the chargeable batteries to the load;

switch means connected in series to each of the plurality of batteries; and

on/off controlling means for controlling the on/off operation of the switched according to the output of the charge/discharge monitoring means and the charging/discharging state of each of the plurality of batteries, further comprising current detecting means for detecting the current flowing in each of said plurality of batteries,

wherein said switch means is inserted between said plurality of batteries and the current detecting means for detecting the current of said plurality of batteries.

3. A power supply apparatus in which a plurality of chargeable batteries are connected in parallel between the node of an external power source and a load, and the common ground of the external power source and the load, comprising:

charge/discharge monitoring means for judging whether the external power source is in a charging state when the load is driven and a sufficient voltage for charging the batteries is outputted, or in a discharging state when a sufficient voltage is not outputted and a discharging current should be supplied from the chargeable batteries to the load;

switch means connected in series to each of the plurality of batteries; and

on/off controlling means for controlling the on/off operation of the switches according to the output of the charge/discharge monitoring means and the charging/discharging state of each of the plurality of batteries, further comprising a direct current-direct current (DC-DC) converter, provided between the node of said external power source and said load, and the parallel node of said plurality of batteries and controlled by a pulse width modulation (PWM) when charging said plurality of batteries, for composing a direct discharging route from said plurality of batteries to said load when said plurality of batteries discharge current to said load.

4. A method for charging the plurality of batteries in a power supply apparatus with a plurality of chargeable batteries, comprising the steps of:

(a) charging a battery with the lowest voltage among the plurality of batteries;

(b) judging whether or not the charging of the battery during charging is completed;

(c) when the charging of the battery is judged to be completed in step (b), charging a battery with the lowest voltage among the plurality of remaining batteries other than the battery in which the charging is completed; and

(d) repeating steps (b) and (c).