Ventilation device

A ventilation device comprising:

• a blade
• a motor that drives the blade;
• an alternating current-direct current conversion circuit that converts an AC voltage supplied externally into a DC voltage to output the DC voltage;
• an inverter circuit that converts the DC voltage output from the AC-DC conversion circuit into an AC voltage through a three-phase pulse width modulation method to apply the AC voltage to the motor;
• a voltage detection unit that detects the DC voltage applied to the inverter circuit;
• a current detection unit that detects a current flowing into the motor;
• a rotation detection unit that computes a rotation speed and a position of the motor, based on the current detected by the current detection unit;
• a target air volume computation unit that outputs a target air volume toward which the motor provides an air volume;
• an air volume computation unit that compares a present output air volume with the target air volume output from the target air volume computation unit to instruct the rotation speed;
• a speed controller that changes a duty for the inverter circuit, based on a result of comparison performed by the air volume computation unit, to control the rotation speed of the motor;
• and
• an AC voltage estimation unit that estimates the AC voltage, based on the DC voltage detected by the voltage detection unit and the current detected by the current detection unit,
• wherein
• the air volume computation unit determines the rotation speed of the motor, based on the AC voltage estimated by the AC voltage estimation unit and the target air volume output from the target air volume computation unit.