Electrical transmission or interconnection systems – Personnel safety or limit control features – Interlock
Patent
1981-08-06
1983-10-18
Miller, Stanley D.
Electrical transmission or interconnection systems
Personnel safety or limit control features
Interlock
307254, 307280, 307311, H03K 3335, H03K 333
Patent
active
044108109
ABSTRACT:
A transistor switching circuit for switching a power transistor (28) from an on state to an off state at high speeds with minimal dissipation of power and without encountering secondary breakdown in the power transistor. The transistor switching circuit includes a transformer (36) having a secondary winding (35) connected to the base (30) of the power transistor (28) and a primary winding (49) connected to switching logic (38), the transformer (36) providing galvanic isolation between the power transistor (28) and the switching logic (38). The switching logic (38) includes a first switch (50) and a second switch (52). With the first switch (50) on and the second switch (52) off, the secondary winding (35) of the transformer (36) develops a positive base current applied to the power transistor (28) turning the transistor on. To initiate switching of the transistor (28) off, the first and second switches (50,52) are both on, causing the secondary winding (35) to cease conducting current to allow collector charge carriers of the transistor (28) to recombine. After the collector charge carriers have sufficiently recombined, as sensed by a saturation sensing circuit (62), the first switch (50) is turned off, the second switch (52) remaining on so that the secondary winding (35) develops a negative current applied to the base of the power transistor (28), turning the transistor (28) off rapidly. The transistor switching circuit further includes means to limit the maximum base-emitter voltage of the transistor and means to reset the transformer core rapidly.
REFERENCES:
patent: 3852620 (1974-12-01), Milberger et al.
patent: 4239989 (1980-12-01), Brajder
patent: 4287436 (1981-09-01), Tezuka et al.
patent: 4293812 (1981-10-01), Kubach et al.
patent: 4318011 (1982-03-01), Zeis
patent: 4322785 (1982-03-01), Walker
patent: 4348598 (1982-09-01), Smith
Davis B. P.
Gould Inc.
Miller Stanley D.
Pierce Kay H.
Sachs Edward E.
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