RECHARGEABLE DC POWER SUPPLY

PROBLEM TO BE SOLVED: To realize long time driving of a load by eliminating useless power consumption of a charging current detecting resistor in discharging in an arrangement wherein the charging current detecting resistor detects and controls the charging current in charging. SOLUTION: A charge control circuit 13, a charging switch 14, a charging current detecting resistor 12 and a charging battery 11 are connected in series and a discharging switch 16 is inserted between the positive electrode terminal A of the charging battery 11 and a load circuit 18. A switch control circuit 17 closes the charging switch 14 and opens the discharging switch 16 in charging operation, and opens the charging switch 14 and closes the discharging switch 16 discharging operation. The charge control circuit 13 controls the charging current by detecting the charging current iCH flowing through the charging current detecting resistor 12. A series circuit of the charging current detecting resistor 12 and the charging switch 14 is inserted between the charge control circuit 13 and the joint P of the charging battery 11 and the discharging switch 16.