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:
May. 29, 2001
Filed:
Aug. 21, 2000
Metali Ajro, Waterbury, CT (US);
George H. Harlan, Hanson, MA (US);
Nidec America Corporation, Torrington, CT (US);
Abstract
A control circuit for a pulse width modulation (PWM) driven electric motor is provided for operating a fan or motor at a full duty cycle in the event that the PWM input signal should malfunction or fail. The control circuit includes a pulse width modulation (PWM) source having an output; a switch having a control and being coupled between a voltage source and the motor; a capacitor having an input coupled to the PWM output and an output coupled to the switch control, and a diode coupled between the PWM output and the switch control for maintaining the output of the capacitor at a predetermined minimum voltage level. In response to a substantially direct voltage level at the PWM output indicative of a failure of the PWM source, the capacitor maintains at its output a voltage level sufficient to cause the switch control to connect the voltage source to an input of the electric motor and drive the electric motor at a full duty-cycle. The diode provides d.c. restoration at the output of the capacitor to ensure that when the voltage level of the PWM output is time varying, an input voltage at the input of the motor substantially corresponds to the voltage level of the PWM output.