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. 08, 2001
Filed:
Nov. 12, 1998
Robert W. Jewell, Boise, ID (US);
Hewlett-Packard Company, Palo Alto, CA (US);
Abstract
A fixing device, such as a halogen bulb fuser or an instant on fuser, includes a first heating element supplied with substantially constant average power by a power control circuit in preparation for and during fusing. Additionally, the instant on fuser includes a second heating element supplied by the power control circuit. The power control circuit measures the average voltage across and the average current through the first heating element to detect changes in the thermal load applied to the first heating element. In preparation for fusing, the power control circuit applies sufficient power to the second heating element for fusing the expected average thermal load. If the power control circuit detects a level of thermal loading on the instant on fuser different than the expected average thermal load, the power control circuit adjusts the power supplied to the second heating element to compensate for the level of thermal loading different than the average expected thermal load. The power control circuit includes a pulse width modulator that adjusts the duty cycle of a drive signal applied to the gate terminal of a first triac coupled in series with the first heating element to maintain substantially constant power dissipation in the first heating element. To compensate for thermal loading different than the average expected thermal load, the pulse width modulator adjusts the duty cycle of a drive signal applied to the gate terminal of a second triac coupled in series with the second heating element.