Patent ID: 6937488

Claim:
A power supply unit comprising: a converter including a diode bridge and a switching element for converting an AC power to a DC power, a step-up reactor which comprises, together with the converter, a step-up chopper circuit, and a capacitor for recharging a DC voltage boosted by said step-up chopper circuit, a control circuit for performing on/off control of said switching element, and an inverter for converting a DC power to an AC power, an input current detector circuit for detecting the input current of an AC power supply, an input voltage detector for detecting the input voltage of the AC power supply, and a DC voltage detector circuit for detecting the voltage of said capacitor, wherein said control circuit calculates, through PI control, the amplitude of a current command per half cycle of said AC power supply at a point in time where a sign of the input voltage from said AC power supply changes based on the difference between a reference voltage command and the voltage of said capacitor, calculates a normalized current command by dividing the amplitude of the current command by the peak value of the last input voltage and multiplying the resulting value by the input voltage from said AC power supply, and generates a switching signal for performing on/off control of said switching element by comparing the current command thus calculated with the input current detected by said input current detector circuit.