PURPOSE: To make the constituent component of a fan-motor drive circuit small- sized and to reduce a circuit-mounting scale.
CONSTITUTION: A converter circuit 6 and a step-down chopper circuit 5 produce the driving voltage of a fan motor 1. On the other hand, a control power supply which is supplied to a control part 12 is constituted of a high-frequency transformer 7 connected to the converter circuit, of a switching circuit 8 connected to the high-frequency transformer, of a first rectifying and smoothing circuit 9 which is connected to any one secondary winding out of a plurality of secondary windings for the high-frequency transformer and which supplies a rectified and smoothed output to an inverter 2 and the step-down chopper circuit and of a second rectifying and smoothing circuit 10 which is connected to another secondary winding and which supplies a rectified and smoothed output to the control part. In addition, a switching converter which changes an output voltage into 1/(n) [where (n) represents a number of 1 or higher] can be used as the converter circuit.
KAWAGUCHI YUJI
ISHII MAKOTO
IIZUKA SHINICHI
