Overvoltage protecting circuit in a steady state
The invention relates to an overvoltage protection circuit comprising an MOV (Metal Oxide Varistor) voltage limiting device ( 3 ) which is disposed in series with a GDT (Gas Discharge Tube) voltage limiting device ( 4 ). The invention is characterized in that a resistor ( 5 ) is disposed in parallel with the aforementioned GDT device ( 4 ), the value of said resistor being such that the voltage supported by the GDT device ( 4 ) is less than the holdover voltage thereof. In another embodiment of the invention, a second resistor ( 6 ) is disposed in parallel with the MOV device ( 3 ) and, together with the above-mentioned resistor ( 5 ), forms a resistive divider such that the voltage applied the GDT device ( 4 ) under steady-state conditions is less than the holdover voltage of the GDT. The invention is suitable for communication systems and, preferably, for applications involving communication via electrical network, since the protection effectiveness is improved owing to the fact that the holdover voltage of the GDT device ( 4 ) must be less than that normally required.
1. A arrestor against voltage surges, that consists of a MOV voltage limiter ( 3 ) (Metal-oxide Varistors) placed in series with a GDT voltage limiter ( 4 ) (Gas Discharge tubes); characterized in that parallel to the GDT voltage limiter device ( 4 ) it comprises a resistor ( 5 ) with a value such that the voltage that the GDT voltage limiter device supports is less than its holdover voltage required to maintain it on.
2. A arrestor against voltage surges, according to claim 1 , characterized in that in parallel to the MOV voltage limiter device ( 3 ) it comprises a resistor ( 6 ) that along with the resistor ( 5 ) placed in parallel with the GDT voltage limiter device ( 4 ) forms a resistive divider so that the voltage that the GDT device ( 4 ) is submitted to in steady state conditions is less that the holdover voltage required to maintain the GDT on ( 4 ).