Motor drive device

A motor drive device comprising:

• a constant voltage power supply structured to supply a DC voltage to an inverter to drive a motor;
• and
• a motor drive control unit,
• wherein the constant voltage power supply comprises:
• an AC/DC converter structured to convert an AC voltage supplied from an AC voltage source into a DC voltage, and output a first DC voltage, the AC/DC converter having a rectifier circuit to rectify the AC voltage, and a first smoothing capacitor;
• a zero-cross detector structured to detect a zero-cross point of the AC voltage, and output a zero-cross detection signal;
• a switching control unit structured to output a switching control signal that is a PWM signal at a timing based on the zero-cross detection signal;
• and
• a switching regulator structured to receive the first DC voltage, and output, to the inverter, a second DC voltage generated by performing switching on the first DC voltage, the switching regulator having a switching element to perform the switching in accordance with the switching control signal, and
• the motor drive control unit outputs a motor drive signal to the inverter based on an inputted rotation command signal.