To provide an inverter circuit which prevents an increase in an operation sound caused by switching to a carrier frequency which is lower unnecessarily.
When a temperature detected by a temperature detecting means 107 exceeds a threshold temperature, the inverter circuit switches to the lower carrier frequency. A difference becomes larger between a temperature of a power portion 105 and the temperature by the temperature detecting means 107 during a predetermined time from an initial time of putting power supply to work, when a DC brushless motor 104 is continuously operated for a predetermined time or more from the initial time. In such case, the threshold temperature is made lower than usual. When the difference is larger between the temperature of the power portion 105 and the temperature by the temperature detecting means 107, the threshold temperature is set lower by which the carrier frequency can be switched at more appropriate threshold temperature.
NOMURA SHINICHIRO
OGAWARA HIDEJI
ENDO KATSUMI
| JP2002272126A | 2002-09-20 | |||
| JP2005020919A | 2005-01-20 | |||
| JPH11252976A | 1999-09-17 |
Hiroki Naito
Daisuke Nagano
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