Patent ID: 7283341

Claim:
A passive and autonomous protection circuit for a two wire system for protecting electric and electronics equipment from both positive and negative over-voltages occurring between both said wires, said protection circuit be connected between first and second said wires and between a power supply and said equipment, the protection circuit comprising: an inductor (Lak) with first and second terminals so that the first terminal of said inductor is connected to said first wire, a power resistor (Rak) with first and second terminals so that the second terminal of said power resistor is connected to said second wire, first and second semiconductors (S 1 ,S 2 ), each semiconductor comprising an anode terminal, a cathode terminal and a gate terminal, the anode terminal of said first semiconductor (S 1 ) and the cathode terminal of said second semiconductor (S 2 ) being connected to the second terminal of said inductor (Lak), and the cathode terminal of said first semiconductor (S 1 ) and the anode terminal of said second semiconductor (S 2 ) being connected to the first terminal of said power resistor (Rak) so as to provide a circuit path for over-voltage induced currents of positive or negative polarity between said first and second wires, and a firing and over-voltage threshold sensing circuit for each said semiconductor (S 1 ,S 2 ).