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:
Jan. 08, 2002
Filed:
Aug. 15, 2000
Shoichi Furuhata, Nagano, JP;
Minoru Nishio, Nagano, JP;
Fuji Electric Co., Ltd., Kawasaki, JP;
Abstract
In an ignition semiconductor device, a self-shut down circuit forcibly turns off an IGBT when an input signal is continuously applied. The self-shut down circuit is formed of a main-current gradual-reduction circuit having a timer circuit, a capacitor, a resistor, and an FET. When the timer circuit, which is actuated when the input signal is input, counts out, the FET is turned on to cause a capacitor, which is connected parallel to a resistor for producing a reference voltage for a current-limiting circuit, to discharge slowly through the resistor, thereby gradually reducing the reference voltage. Correspondingly, the current-limiting circuit reduces the main current to turn off the IGBT. The slow turn-off operation of the IGBT prevents a high voltage from being generated in the ignition coil. Accordingly, an unwanted high voltage is prevented from being generated in the secondary winding of an ignition coil when an output-stage element is forcibly turned off following the continuous application of an input signal.