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:
Aug. 02, 2005
Filed:
Aug. 06, 2002
Michael J. Dhuey, Cupertino, CA (US);
Michael J. Dhuey, Cupertino, CA (US);
Apple Computer, Inc., Cupertino, CA (US);
Abstract
A novel a circuit for driving a fan includes an output terminal for supplying the fan with drive power, a pulse width modulation driver, and a limiter. A first power terminal of the fan is held at a first voltage (e.g., 0V), and a second power terminal of the fan is coupled to the output terminal of the driver circuit. The PWM driver provides a series of fan drive pulses on the output terminal, and the limiter prevents the voltage on the output terminal from falling below a predetermined voltage. The predetermined voltage is greater than the first voltage at which the fan's first power terminal is held, and is sufficient to keep the fan in motion even when the duty cycle of the PWM signal is 0%. In a particular embodiment the limiter includes a voltage clamp. In a more particular embodiment, the voltage clamp is a diode. In another particular embodiment, the limiter includes a switch for combining a PWM signal with a DC voltage at an output.