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. 29, 1987
Filed:
Mar. 12, 1986
Hiroshi Mitsuoka, Itami, JP;
Mitsubishi Denki Kabushiki Kaisha, Tokyo, JP;
Abstract
For suppressing an abnormal rise in the anode-cathode voltage of a gate turnoff thyristor (GTO), a main snubber circuit and a number of sub snubber circuits are disposed across the anode and cathode of the GTO, and selected ones of the sub snubber circuits are selectively activated by a control circuit in accordance with the magnitude of a main current flowing through the GTO in order to minimize the power loss of the entire snubber circuit. The main snubber circuit includes a capacitor of comparatively small capacity corresponding to a comparatively small and steady main current. The control circuit includes a current detector detecting the main current. For a small steady load, only the main snubber circuit is operated, but at higher loads the control circuit selectively activates an increasing number of the sub snubber circuits. For each sub snubber circuit, the control circuit preferably includes a respective comparator for comparing an output of the current detector to a respective predetermined value and a respective turn-on signal generator for selectively activating the sub snubber circuit in response to an output of the respective comparator.