| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a control circuit 10 for a rotational speed of a fan by which the rotational speed of the fan under an arbitrary voltage can be changed, as required, in an arbitrary input voltage. <P>SOLUTION: A drive circuit 14 for outputting a pulse is provided so that a coil 18 of a fan motor generates a magnetic field. A voltage level distributing circuit 12, which has a first transistor Q1 and a plurality of resistors R1-R4, is connected in between a drive integrated circuit 14 and a voltage source Vcc. A rotational speed regulator 16, which has a second transistor Q2 and a plurality of resistors R5-R7 connected in parallel, is connected in between the voltage level distributing circuit 12 and the drive integrated circuit 14. The control circuit 10 is constituted so as to have a first current path in a first input voltage and a second current path by the change of the continuity state of the transistors Q1, Q2 in a second input voltage larger than the first input voltage. The current is made to pass the resistors R5-R7 connected in parallel in the second current path. A conduction current of the drive integrated circuit 14 is changed, and accordingly, the rotational speed of the fan is adjusted to an initial value. <P>COPYRIGHT: (C)2005,JPO&NCIPI |
