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:
Nov. 05, 1985
Filed:
Sep. 13, 1982
Kazuo Kuroki, Tokyo, JP;
Fuji Electric Company, Ltd., Kawasaki, JP;
Abstract
Disclosed is an isolation circuit for a power transistor that enables a control circuit to turn the power transistor on and off, while insulating the control circuit from DC currents that may flow to or from the power transistor. The isolation circuit includes a first pulse transformer for receiving a pulse string signal corresponding to an ON command signal from the control circuit to alternatingly energize and de-energize the first pulse transformer. In addition, the isolation circuit includes a fast circuit path comprising a pair of serially connected diodes coupled between the secondary winding of the first pulse transformer and the base resistor of the power transistor for rapidly supplying base current drive to the transistor as soon as the first pulse transformer is energized. Also included in the isolation circuit is a base drive maintaining circuit coupled to the fast circuit path and to the base resistor of the power transistor. The maintaining circuit includes a capacitor that charges while the first pulse transformer is energized and discharges to supply base current drive to the power transistor when the first pulse transformer is de-energized. Furthermore, the isolation circuit includes a second pulse transformer for receiving a pulse signal corresponding to an OFF signal from the control circuit. The secondary winding of the second transformer being coupled to the base drive maintaining circuit for discharging the capacitor and terminating the base current drive to power transistor when the pulse signal corresponding to the OFF signal is received.