To provide a DC power supply for cordless power tools, capable of always outputting its maximum capacity irrespective of a preset output voltage value.
An output voltage is selected to matche a cordless power tool to be used, and a maximum output current value is set for the selected output voltage. Maximum capacity of the DC power supply is utilized, by setting the maximum output current value in such a way that, the lower the selected output voltage, the larger the maximum output current value becomes, specifically the product of the maximum output current multiplied by the selected output voltage becomes approximately constant. As long as the output current remains below the maximum output current, the connected cordless power tool is controlled by the constant voltage. If it exceeds the maximum output current, it is switched to the control by a current equal to or lower than a constant current of the maximum output current to protect the DC power supply against overload.
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TAKEDA TAKESHI
TAKANO NOBUHIRO
FUNABASHI KAZUHIKO
Shin Koizumi
Akiko Ichikawa