Patent ID: 7616418
Filing Date: 2009-11-10
Classification: H02H

Abstract:
1. A transient blocking unit (TBU) comprising: a first depletion mode transistor having a first gate controlling a first current between a first source and a first drain; a first uni-directional shunt circuit connected to said first source and to said first drain; and a control circuit connected to said first gate and to at least one of said first source and said first drain; wherein said TBU provides an automatic shut-off function of a controllable current passing through said TBU responsive to an over-voltage or over-current condition, and is thereby capable of protecting an electrical load connected in series with said TBU from said over-voltage or over-current condition; wherein, for a first polarity of said controllable current, said control circuit acts primarily to switch off said first depletion mode transistor responsive to an over-voltage or over-current condition, thereby shutting off flow of said first current and of said controllable current; wherein said first uni-directional shunt circuit is disposed to limit a voltage between said first source and said first drain to a value substantially less than a reverse breakdown voltage of said first depletion mode transistor when said controllable current has a second polarity opposite to said first polarity.