VENTILATION DEVICE

PROBLEM TO BE SOLVED: To provide a ventilation device preventing a state exceeding withstanding pressure of an electronic component even if electric power generation voltage of a D.C. motor is instantaneously superposed on D.C. power supply voltage obtained by rectifying and smoothing commercial power supply voltage and applied to the D.C. motor, when a fan is operated in the state where the D.C. motor is reversely rotated and generates electric power due to an external factor such as against wind from an outdoor space. SOLUTION: The ventilation device includes: the fan 2 for discharging indoor air to the outdoor space; the D.C. motor 3 for rotating the fan 2; a drive means 7 for outputting a drive signal to a switching element for driving the D.C. motor 3; and a control means 4 having a rotational frequency detection means 8 for detecting predetermined rotational frequency of the D.C. motor 3 and a voltage lowering means 9 for lowering the D.C. power supply voltage. In accordance with the rotational frequency detected by the rotational frequency detection means 8, the drive means 7 and the voltage lowering means 9 are controlled. COPYRIGHT: (C)2011,JPO&INPIT