Patent ID: 7380891

Claim:
A power supply apparatus, comprising: a capacitor unit formed of a plurality of capacitors; a microprocessor unit for interrupting charging after a start of charging or interrupting discharging after a start of discharging of the capacitor unit in measuring an internal resistance value of the capacitor unit; and a detection unit for measuring the internal resistance value of the capacitor unit based on at least one of: 1) a current value in the charging; and one of i) a voltage decrease when the charging is interrupted by the microprocessor unit or ii) a voltage increase when the charging is restarted after the interruption of the charging by the microprocessor unit, wherein in measuring the internal resistance value of the capacitor unit, the charging is interrupted when a voltage across the capacitor is increasing over a period of time during charging, or 2) a current value in the discharging; and one of i) a voltage increase when the discharging is interrupted by the microprocessor unit or ii) a voltage decrease when the discharging is restarted after the interruption of the discharging by the microprocessor unit, wherein in measuring the internal resistance value of the capacitor unit, the discharging is interrupted when a voltage across the capacitor is decreasing over a period of time during discharging.