Power supply apparatus with chargeable battery and charge/discharge method

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.

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.

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).