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:
Apr. 13, 2004
Filed:
Aug. 13, 2002
Koichi Toyama, Kariya, JP;
Denso Corporation, Kariya, JP;
Abstract
A discharge lamp ballast circuit has a snubber circuit to perform a soft switching when the MOS transistor is turned off. The snubber circuit has, for example, a capacitor that resonates with a reactance of the fly-back transformer and enables a zero voltage switching. Before a breakdown of a discharge lamp, a control circuit drives the MOS transistor in a non-zero voltage switching manner by turning on the MOS transistor just after a peak voltage. The non-zero voltage switching increases an output voltage of the fly-back transformer. After the breakdown of the discharge lamp, the control circuit turns on the MOS transistor in the zero voltage switching manner to perform the soft switching. As a result, it is possible to reduce switching loss during a lighting of the discharge lamp and to supply sufficient voltage in the lighting preparation period.