| 摘要 |
PROBLEM TO BE SOLVED: To provide a motor fan a radiation fan having a variable revolution which can avoid a sudden acceleration or deceleration of the radiation fan and can extend the operation life time of the radiation fan by a method wherein the revolution of the radiation fan is linearly and gently accelerated or decelerated. SOLUTION: After a rectifying circuit rectifies a revolution signal for detecting a radiation fan 90, the rectifying circuit outputs the rectified signal to a negative terminal of a differential amplifier 70. The positive terminal of the differential amplifier 70 is connected to a temperature detection circuit 80 connected in series to a power supply Vcc. The resistance value of the thermosensor 81 of the temperature detection circuit 80 is changed by temperature. Since the drive voltage Vf of the output terminal of the differential amplifier 70 is elevated, when the temperature is increased, the revolution of the radiation fan 90 is increased. As the drive voltage Vf is lowered, when the temperature falls, the revolution of the radiation fan is reduced. With the use of such a constitution, the radiation fan can be controlled by the temperature, so as to gently linearly and change the revolution. |
