Back to results
US 5,293,051 AGranted
Photoswitching device including a MOSFET for detecting zero voltage crossing
AssigneeSharp Kabushiki Kaisha
InventorsMitsuru Mariyama, Nobuyuki Kato
Life of this patent
Estimating the term…
Abstract
A switching device includes a thyristor and a MOSFET, and a voltage clamp circuit. The voltage clamp circuit includes an N.sup.+ type contact region formed in a surface layer of a N type substrate and electrically connected to a gate electrode of a MOSFET, and a P type guard ring surrounding the contact region.
Claims8
A switching device formed on a main surface of an N-type semiconductor substrate, comprising:
- a first thyristor, and
- a first MOSFET for detecting a zero voltage crossing and providing a first zero crossing signal to said thyristor, said MOSFET including a first gate electrode electrically connected to said N-type substrate, and
- a first voltage clamp circuit for preventing voltage applied to said gate electrode from exceeding a predetermined voltage including:
- a first N.sup.+ -type contact region formed in a surface layer of said N-type substrate and electrically connected to said gate electrode, and
- a first P-type guard ring surrounding said N.sup.+ -type contact region,
- wherein a depletion layer expands throughout an interior region of said first P-type guard ring when the voltage applied to said first gate electrode exceeds said predetermined voltage to electrically isolate said first N.sup.+ -type contact region from said N-type substrate.
3 more elements
Dependencies are inferred from the claim text.