Ac-dc converter

An AC-DC converter that converts an AC power supply voltage to a DC output voltage of a prescribed magnitude with power factor regulation, comprising:

• a rectifying circuit that rectifies the AC power supply voltage to output a rectified voltage;
• a reactor that receives the rectified voltage;
• a semiconductor switching device connected in series to the reactor;
• a voltage regulation unit that receives a detected value of the DC output voltage and a command value and that outputs an amplitude command for the rectified current that represents a difference between the detected value of the DC output voltage and the command value;
• an instantaneous value command calculator that receives the amplitude command from the voltage regulation unit and an estimated value of the rectified voltage that is obtained without actually detecting the rectified voltage and that calculates an instantaneous value command for the rectified current from the amplitude command and the estimated value of the rectified voltage;
• a current regulation unit that receives the instantaneous value command from the instantaneous value command calculator and a detected value of a rectified current flowing through the reactor and that outputs a signal representing a difference between the instantaneous value command and the detected value of the rectified current;
• an output voltage command calculator that receives the signal outputted from the current regulation unit and the estimated value of the rectified voltage and that calculates an output voltage command for the semiconductor switching device from the signal outputted from the current regulation unit and the estimated value of the rectified voltage;
• a drive signal generator that receives the output voltage command from the output voltage command calculator and a carrier signal and that generates a drive signal for the semiconductor switching device from the output voltage command and the carrier signal, the driving signal being provided to the semiconductor switching device so as to switch the semiconductor switching device ON and OFF;
• and
• a rectified voltage estimation unit that receives the output voltage command from the output voltage command calculator and that derives the estimated value of the rectified voltage from the output voltage command without actually detecting the rectified voltage, for providing to the instantaneous value command calculator and the output voltage command calculator.