Appartus and method for protecting signal and communication lines from very high voltage and transient pulses

A method for protecting a signal line bus driver comprising the steps of:

• monitoring a time variable bus driver output voltage;
• establishing a reference voltage with a magnitude that has a predetermined threshold value greater than the magnitude of the bus driver output voltage;
• dynamically varying the reference voltage so that a magnitude of the reference voltage continuously maintains a voltage magnitude with the predetermined threshold value greater than the magnitude of the bus driver output voltage;
• monitoring voltage on a signal line to determine presence of fault-induced voltage in excess of the reference voltage;
• and
• opening at least one solid-state switch in the signal line responsively to presence of fault-induced voltage in excess of the reference voltage.

A method for protecting a bus driver of a signal line comprising the steps of:

• positioning a solid-state switch in the signal line between a bus driver and an output end of the signal line;
• providing a positive or a negative voltage across the solid-state switch when open;
• connecting a first comparator to the signal line to compare a signal line voltage of the signal line with a positive reference voltage;
• connecting a second comparator to the signal line to compare the signal line voltage with a negative reference voltage;
• monitoring the signal line voltage on both sides of the switch;
• activating the switch responsively to detection of a differential voltage magnitude across the switch that exceeds a predetermined threshold magnitude;
• protecting a comparator circuit that includes the first and second comparators by monitoring the signal line for a positive or a negative voltage at the output end of the signal line with a clamping circuit;
• and
• blocking current in the signal line from being fed to the solid-state switch.