| 摘要 |
<p>PURPOSE:To achieve low level noise and vibration by providing a circuit that, after a cooling fan has started at a voltage required for its start-up, lowers the voltage to a level required for the normal rotation of the cooling fan. CONSTITUTION:When power is supplied, a voltage is applied to the base of a transistor 202 through a capacitor 209, and the transistor 202 is turned on. When the transistor 202 is turned on, another transistor 201 is turned on as well, and a cooling fan 210 is supplied with power of starting voltage of 5V through the transistor 201. A resistor 204 and the capacitor 209 forms an integrating circuit, and the voltage applied to the base of the transistor 202 is lowered with time until the transistor 202 is turned off. When the transistor 202 is turned off, the transistor 201 is turned off as well, and the voltage is applied to the cooling fan 210 through a resistor 206. This makes it possible to control the speed of cooling fan 210 rotation, and thus reduce noise and vibration to any desired level.</p> |
