The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Nov. 25, 2008
Filed:
Feb. 01, 2007
Atsushi Kanamori, Nukata-gun, JP;
Atsushi Kanamori, Nukata-gun, JP;
DENSO CORPORATION, Kariya, JP;
Abstract
A fan motor is driven under a pulse width modulation (PWM) control. PWM signals to be supplied to a circuit for driving the fan motor are formed from carrier waves having a specified frequency and a duty ratio of the PWM control. Rotational speed of the fan motor is increased by increasing the duty ratio. In a low speed region, the fan motor is driven with a high carrier frequency to suppress driving noises of the fan motor, while it is driven with a low carrier frequency in a high speed region to reduce switching losses in semiconductor elements. The carrier frequency may be continuously decreased when the fan motor speed reaches the high speed region, or it may be stepwise decreased. The low carrier frequency used in the high speed region is set to such a frequency that guarantees a sufficient number of switching times at a maximum speed of the fan motor.