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:
Sep. 09, 2003
Filed:
Oct. 09, 2001
Jeffrey John Boylan, Richardson, TX (US);
Qing Chen, Plano, TX (US);
Jin He, Plano, TX (US);
Del Ray Hilburn, Mesquite, TX (US);
Innoveta Technologies, Plano, TX (US);
Abstract
A control scheme for a synchronous rectifier converter that avoids disabling the synchronous rectifiers entirely. Rather than disable the synchronous rectifier altogether to stop the flow of reverse current in light-load, startup, or shutdown conditions, the duty cycle of the synchronous rectifier is modified such that forward current is always allowed to flow through the synchronous rectifier, but the synchronous rectifier is turned off before the reverse current flow reaches a pre-determined level. This is accomplished by operating the converter in a partially synchronous mode of operation during light-load, startup, or shutdown conditions. Whether the circuit is in a light-load, startup, or shutdown condition is determined by a circuit characteristic of the converter that is sensed by the controller, such as average output current. The desired changeover point from fully-synchronous mode to the partially synchronous mode is set to a predetermined level of output current for the converter. The predetermined level is set based on the particular power system in which the invention is implemented. For example, this level can be based on the amount of reverse current that would disrupt the bus to which the converter output is connected, or it could be based on the heat created by the reverse current flow in the power converter when heat dissipation is a concern. The control scheme of the present invention effectively limits reverse current flow while also improving efficiency by eliminating the need for discrete diodes, yet retaining the benefits of synchronous rectification throughout the operating range of the converter.