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:
Feb. 12, 1991
Filed:
Jan. 22, 1988
Shigenori Yakushiji, Yokohama, JP;
Kabushiki Kaisha Toshiba, Kawasaki, JP;
Abstract
A first short-circuiting MOS FET with a break-through preventing function is connected between the gate and the cathode of a high sensitivity thyristor. A second MOS FET is connected between the gate and the source of the first MOS FET. A gate signal turns on the second MOS FET to reduce the gate voltage of the first MOS FET below threshold voltage. In turn, the short-circuit of the gate to the cathode of the thyristor is removed. Specifically, the gate signal is applied to the gate of the thyristor to trigger it. When forward voltage VAK applied between the anode terminal and the cathode terminal of the thyristor element is larger than the threshold voltage of the first MOS FET, the gate of the first MOS FET is biased to a voltage above the threshold voltage so that the first MOS FET is turned on. Therefore, the gate and the cathode of the thyristor element are short-circuited to prevent the break-through of the thyristor due to the an external transient surge voltage. When gate voltage VGK is input between the gate terminal and the cathode terminal of the thyristor element, the second MOS FET is turned on, so that the gate voltage of the first MOS FET is below the threshold voltage. In turn, the first MOS FET is turned off to remove the short-circuit of the gate and the cathode of the thyristor element, so that the thyristor element is turned on. The gate current is supplied to the gate of the thyristor element to turn on the thyristor element.