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:
Jul. 05, 1983
Filed:
Dec. 02, 1980
Katsuhiko Takigami, Yokohama, JP;
Minami Takeuchi, Tokyo, JP;
Tokyo Shibaura Denki Kabushiki Kaisha, Saiwai, JP;
Abstract
A protecting device includes a discriminating circuit and a protecting circuit. The GTO thyristor is operated in such a manner that a carrier storing is completed from a first time point at which the supply of a negative gate current is started to a second time point, an anode-cathode voltage increases from the second time point to a third time point and decreases from the third time point to a fourth time point, and increases again from the fourth time point. The discriminating circuit includes a circuit for obtaining an amount of change between the anode-cathode voltages at the third and fourth time points, a circuit for obtaining a ratio of the amount of change to the anode-cathode voltage at the third time point, and a comparing circuit for producing a control signal when the ratio is smaller than a given value. The protecting circuit, when receiving the control signal, stops the conduction of the GTO thyristor. It is judged whether or not the GTO thyristor is operated at a critical point to its break-down.