Fault-powered low-level voltage clamp circuit

Claim 1

A low-level voltage clamp circuit which provides protective, low-level clamping action across a first and a second terminal of a main DC circuit when the voltage of said DC circuit exceeds a predetermined limit indicating a fault condition, comprising: a reference means operatively connected to said main DC circuit and sensitive to voltages in excess of said predetermined limit, said reference means having a first state when said circuit voltage is below said predetermined limit and a second state when said circuit voltage exceeds said predetermined limit; a comparator means responsive to said reference means and generating a changing output signal when said reference means is in said second state, said changing output signal reflecting the amount of voltage exceeding said predetermined limit; an amplifier means responsive to said comparator means output signal and increasing said comparator output signal by a predetermined amount of gain; and an output stage means responsive to said amplified comparator means output for effecting the clamping of the main circuit voltage to said predetermined level; wherein said low-level voltage clamp utilizes said main DC circuit voltage as a source of control voltage for its components when clamping is being effected and wherein the voltage across said first and second terminals of said main DC circuit remains present throughout the clamping action at a level no greater than said predetermined limit.