Power supply apparatus with chargeable battery and charge/discharge method

• US 6,707,271 B2
• Filed: 07/11/2002
• Issued: 03/16/2004
• 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:
  US10/192,542
• Publication Number:
  US 20020171399A1
• Time in Patent Office: 614 Days
• Field of Search: 320/124, 320/118, 320/127, 320/135, 320/136
• 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 monitor which judges 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 connected in series to each of the plurality of batteries; and

on/off controller which controls the on/off operation of the switches according to the output of the charge/discharge monitor and the charging/discharging state of each of the plurality of batteries, further comprising;

voltage equivalence detector which detects the equivalence of the voltages between said plurality of batteries;

current detector which detects a current flowing in each of said plurality of batteries; and

battery current direction judging unit which judges from the output of the current detector whether a current flowing in each of said plurality of batteries is in a charging direction or in a discharging direction,

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

said on/off controller which performs a control of switching off said switches corresponding to the batteries of which the current flows in a discharging direction and charging only the batteries of which the current flows in a charging direction, and

then, every time a voltage equivalence is detected between batteries corresponding to the switched-off switches and the batteries during charging by the voltage equivalence detector, said on/off controller performs a control of switching on the switched-off switches corresponding to the batteries of which the voltage equivalence is detected by the voltage equivalence detector.

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 monitor which judges 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 connected in series to each of the plurality of batteries; and

on/off controller which controls the on/off operation of the switches according to the output of the charge/discharge monitor and the charging/discharging state of each of the plurality of batteries, further comprising;

current detector which detects a current flowing in each of said plurality of batteries; and

battery current direction judging unit which judges from the output of the current detector whether the current flowing in each of said plurality of batteries is in a charging direction or in a discharging direction,

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

said on/off controller which performs a first control of switching off said switches corresponding to the batteries in which the current is judged to flow in a discharging direction at that moment by the battery current direction judging unit and charging only the batteries in which the current is judged to flow in a charging direction, and

then, every time a predetermined charge time of the batteries elapses, said on/off controller repeats the first control process.

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 monitor which judges 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 controller which controlls the on/off operation of the switches according to the output of the charge/discharge monitor 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 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;

constant voltage/constant current judging unit which judges whether the DC—

DC converter is constant-voltage-controlled so that the output voltage may become constant, or constant-current-controlled so that the output current may become constant;

voltage comparator which compares the voltages of said plurality of batteries;

voltage equivalence detectir which detects the equivalence of the voltages between said plurality of batteries;

current detector which detects the current flowing in each of said plurality of batteries; and

battery current direction judging unit which judges from the output of the current detector whether the current flowing in each of said plurality of batteries is in a charging direction or in a discharging direction,

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

if the constant voltage/constant current judging unit judges that the DC—

DC converter is constant-voltage-controlled,

said on/off controllor performs a control of switching off said switches corresponding to the batteries in which the current is judged to flow in a discharging direction by the battery current direction judging unit and charging only the batteries in which the current is judged to flow in a charging direction, and

then, every time a voltage equivalence is detected between the batteries corresponding to the switched-off switches and the batteries during charging by the voltage equivalence detector, said on/off controller performs a control of switching on the switched-off switches corresponding to the batteries of which the voltage equivalence is detected by the voltage equivalence detector, and

if the constant voltage/constant current judging means judges that the DC—

DC converter is constant-current-controlled,

said on/off controllor performs a control of switching on only said switches corresponding to the batteries with voltages judged to be the lowest by the voltage comparator, and

then, every time a voltage equivalence is detected between the batteries during charge and the other batteries by the voltage equivalence detector, said on/off controller performs a control of switching on the switched-off switches corresponding to the batteries of which the voltage equivalence is detected by the voltage equivalence detector.

4. 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 monitor which judges 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 connected in series to each of the plurality of batteries; and

on/off controller which controlls the on/off operation of the switches according to the output of the charge/discharge monitor 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 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;

constant voltage/constant current judging unit which judges whether the DC—

DC converter is constant-voltage-controlled so that the output voltage may become constant, or constant-current-controlled so that the output current may become constant;

voltage comparator which compares the voltages of said plurality of batteries;

voltage equivalence detector which detects the equivalence of the voltages between said plurality of batteries;

current detector which detects the current flowing in each of said plurality of batteries; and

battery current direction judging unit judging from the output of the current detector whether the current flowing in each of said plurality of batteries is in a charging direction or in a discharging direction,

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

if the constant voltage/constant current judging unit judges that the DC—

DC converter is constant-voltage-controlled,

said on/off controllor performs a control of switching off said switches corresponding to the batteries in which the current is judged to flow in a discharging direction by the battery current direction judging unit and charging only the batteries in which the current is judged to flow in a charging direction, and

then, every time a voltage equivalence is detected between the batteries corresponding to the switched-off switches and the batteries during charging by the voltage equivalence detector, said on/off controller performs a control of switching on the switched-off switches corresponding to the batteries of which the voltage equivalence is detected by the voltage equivalence detector, and

if the constant voltage/constant current judging unit judges that the DC—

DC converter is constant-current-controlled, said on/off controller means performs a control of switching on only said switches corresponding to the batteries with voltages judged to be the lowest by the voltage comparator, and

then, every time a voltage equivalence is detected between the batteries during charge and the other batteries by the voltage equivalence detector, said on/off controller performs a control of switching on the switched-off switches corresponding to the batteries of which the voltage equivalence is detected by the voltage equivalence detector, wherein said DC—

DC converter comprises;

a voltage error amplifier which outputs a signal to constant-voltage-control said DC—

DC converter;

a current error amplifier which outputs a signal to constant-current-control said DC—

DC converter,

wherein said constant voltage/constant current judging unit comprises comparator which compares the output of the voltage error amplifier and the output of the current error amplifier.

5. 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 monitor which judges 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 connected in series to each of the plurality of batteries; and

on/off controller which controlls the on/off operation of the switches according to the output of the charge/discharge monitor 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 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;

constant voltage/constant current judging unit which judges whether the DC—

DC converter is constant-voltage-controlled so that the output voltage may become constant, or constant-current-controlled so that the output current may become constant;

voltage comparator which compares the voltages of said plurality of batteries;

voltage equivalence detector which detects the equivalence of the voltages between said plurality of batteries;

current detector which detects the current flowing in each of said plurality of batteries; and

battery current direction judging unit which judges from the output of the current detector whether the current flowing in each of said plurality of batteries is in a charging direction or in a discharging direction,

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

if the constant voltage/constant current judging unit judges that the DC—

DC converter is constant-voltage-controlled,

said on/off controller performs a control of switching off said switches corresponding to the batteries in which the current is judged to flow in a discharging direction by the battery current direction judging unit and charging only the batteries in which the current is judged to flow in a charging direction, and

then, every time a voltage equivalence is detected between the batteries corresponding to the switched-off switches and the batteries during charging by the voltage equivalence detector, said on/off controller performs a control of switching on the switched-off switches corresponding to the batteries of which the voltage equivalence is detected by the voltage equivalence detector, and

if the constant voltage/constant current judging means judges that the DC—

DC converter is constant-current-controlled,

said on/off controller performs a control of switching on only said switches corresponding to the batteries with voltages judged to be the lowest by the voltage comparator, and

then, every time a voltage equivalence is detected between the batteries during charge and the other batteries by the voltage equivalence detector, said on/off controller performs a control of switching on the switched-off switches corresponding to the batteries of which the voltage equivalence is detected by the voltage equivalence detector, wherein

said constant voltage/constant current judging unit comprises voltage comparator which compares the output voltage of said DC—

DC converter and a predetermined reference voltage.

6. 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 monitor which judges 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 connected in series to each of the plurality of batteries; and

on/off controller which controls the on/off operation of the switches according to the output of the charge/discharge monitor and the charging/discharging state of each of the plurality of batteries, further comprising discharge completion detector which dectects a state where each of said plurality of batteries completes discharging, wherein when said charge/discharge monitor judges that said external power source is in a discharging state,

said on/off controller performs a first control of switching on only said switch corresponding to one battery out of said plurality of batteries,

then, when the discharge completion detector detects the discharge of one battery, said on/off controller performs a second control of switching off the switched-on switch and a third control of switching on only said switch corresponding to one battery out of the remaining batteries in which the discharging completion is not detected by the discharge completion detector, and then, every time the discharging completion of one battery is detected by the discharge completion detector, said on/off controller repeats the second and third control process.

7. 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 monitor which judges 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 connected in series to each of the plurality of batteries; and

on/off controller which controls the on/off operation of the switches according to the output of the charge/discharge monitor and the charging/discharging state of each of the plurality of batteries, further comprising discharge completion detector which detects a state where each of said plurality of batteries completes discharging, wherein when said charge/discharge monitor detects that a status of said external power source charges from a charging state to a discharging state,

said on/off controller maintains the on/off operation of said switch in the charging state,

then, every time the discharging completion detector detects the discharging completion of any of the batteries in which the corresponding switch is switched on, said on/off controller performs a control of switching off switches corresponding to the batteries in which discharging completion is detected by the discharge completion detector,

then, when the discharging completion of batteries corresponding to all the switches switched on in the charge state is detected by the discharge completion detector, said on/off controller performs a control of switching on the switches switched off in the charging state.

8. 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 monitor which judges 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 connected in series to each of the plurality of batteries; and

on/off controller which controls the on/off operation of the switches according to the output of the charge/discharge monitor and the charging/discharging state of each of the plurality of batteries, further comprising;

discharge completion detector which detects a state where each of said plurality of batteries completes discharging;

current detector which detects the current flowing in each of said plurality of batteries; and

battery current direction judging unit which judges from the output of the current detector whether the current flowing in each of said plurality of batteries is in a charging direction or in a discharging direction,

wherein when said charge/discharge monitor detects that a status of said external power source charges from a charging state to a discharging state,

said on/off controller performs a first control of switching off said switches corresponding to the batteries in which the current is judged to flow in a charging direction at that moment by the battery current direction judging unit and discharging only the batteries in which the current is judged to flow in a discharging direction, and

then, every time the predetermined discharge times of the batteries elapse, said on/off controller repeats the first control process.

9. 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 monitor which judges 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 connected in series to each of the plurality of batteries; and

on/off controller which controls the on/off operation of the switches according to the output of the charge/discharge monitor and the charging/discharging state of each of the plurality of batteries, further comprising;

current detector which detects the current flowing in each of said plurality of batteries;

battery current direction judging unit which judges from the output of the current detector whether the current flowing in each of said plurality of batteries is in a charging direction or in a discharging direction, and

voltage equivalence detector which detects the equivalence of the voltages between said plurality of batteries,

wherein when said charge/discharge monitor judges that a status of said external power source charges from a charging state to a discharging state,

said on/off controller performs a control of switching off said switches corresponding to the batteries in which the current is judged to flow in a charging direction at that moment by the battery current direction judging unit and discharging only the batteries in which the current is judged to flow in a discharging direction, and

then, every time a voltage equivalence is detected between the batteries corresponding to the switched-off switches and the batteries during discharge by the voltage equivalence detector, said on/off controller performs a control of switching on the switched-off switches corresponding to the batteries of which the voltage equivalence is detected by the voltage equivalence detector.

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

(a) charging only the batteries out of the plurality of batteries in which the respective current flows in a charge direction when the status of said power supply apparatus indicates a charging state;

(b) detecting batteries of which the voltages become equal to the voltages of the batteries during charging from the plurality of batteries, except for those during charging;

(c) charging the batteries detected in step (b); and

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

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

(a) charging only the batteries out of the plurality of batteries in which the respective current flows in a charging direction when the status of said power supply apparatus indicates a charging state;

(b) when the predetermined charging times of the batteries during charging elapse, detecting the direction of the current flowing in each of the plurality of batteries which have not charged;

(c) charging only the batteries in which the respective current detected in step (b) flows in a charging direction; and

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

12. A method for charging a plurality of batteries in a power supply apparatus comprising a plurality of chargeable batteries and a direct current-direct current (DC—

DC) converter, provided between the node of an external power source and a load, and the parallel mode of the plurality of batteries and controlled by a pulse width modulation (PWM) when charging the plurality of batteries, for composing a direct discharging route from the plurality of batteries to the load when the plurality of batteries discharge current to the load, comprising the steps of;

(a) when charging said plurality of batteries, the DC—

DC converter judges whether the converter is constant-voltage-controlled so that the output voltage may become constant, or constant-current controlled so that the output current may become constant;

(b) if is judged in step (a) that the DC—

DC converter is constant-voltage-controlled, executing the following steps;

(c) charging only the batteries out the plurality of batteries in which the respective current flows in a charge direction when the status of said power supply apparatus indicates a charging state;

(d) detecting batteries of which the voltages become equal to the voltages of the batteries during charging from the plurality of batteries except for those during charging;

(e) charging the batteries detected in step (d); and

(f) repeating steps (d) and (e), and

(g) if it judged in step (a) that the DC—

DC converter is constant-current-controlled, executing the following steps;

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

(i) detecting batteries of which the voltages become equal to the voltages of the batteries during charging from the plurality of batteries, except for those during charging;

(j) charging the batteries detected in step (i); and

(k) repeating steps (i) and (j).