| 摘要 |
PURPOSE:To prevent the generation of electrical noises, and to inhibit audible sounds generated by a cooling fan to an irreducible minimum of a demand, by controlling a motor for driving the cooling fan by means of a full-wave rectifier and a transistor. CONSTITUTION:An AC motor M1 for driving a cooling fan is connected to an AC power S1 through a diode full-wave rectifier (r) and a transistor Q1. A series circuit composed of a temperature response impedance T1 such as a thermistor and a resistor R1 is connected in order to change currents in a winding W1 in response to a temperature change at a specified point in a device. An interface J1 between the resistor R1 and the impedance T1 is connected to a base for a transistor Q2, output power from the transistor Q1 is varied, and currents flowing through the winding W1 are altered. |
