Patent ID: 7675196

Claim:
A power supply apparatus comprising: a first power supply that outputs a constant voltage using an externally supplied power as an input source; a second power supply that outputs a constant current using a power charged in a capacitor as an input source; a circuit unit that connects an output from the first power supply and an output from the second power supply in parallel, and simultaneously supplies a power from the first power supply and a power from the second power supply to a load; a current detector that detects a current supplied to the load; a control unit that controls an output current from the first power supply to equal to or lower than an upper-limit value, and controls an output current from the second power supply to a value obtained by subtracting the upper-limit value from the current detected by the current detector; a residual power detector that detects a residual power of the capacitor; and an abnormality detector that estimates the residual power of the capacitor according to an operating state of the power supply apparatus and detects an abnormality in simultaneously supplied power, based on detected residual power and estimated residual power.