| 摘要 |
PURPOSE:To reduce the waste of electric power consumption as well as noise and lengthen the life of internal parts by changing the rotating speed of a fan motor in accordance with the waiting condition or the operating condition of an electronic apparatus. CONSTITUTION:When a disc motor 12 is driven, the level of a signal outputted from a comparator 13 becomes 'Lo'. According to this operation, a conducting condition between the collector and the emitter of a motor controlling transistor 14 becomes OFF. In this case, all of current, outputted from a power source through a resistor R3, is supplied to a fan motor 11, whereby the fan motor 11 is rotated in a high speed. Next, when the disc motor 12 is stopped, the level of the signal outputted from the comparator 13 becomes 'Hi'. According to this operation, the conducting condition between the collector and the emitter of the motor controlling transistor 14 becomes ON. As a result, a voltage across the fan motor 11 is reduced and the rotating speed of the fan motor 11 is reduced. |
