Circuit interruption device

A crowbar circuit for an electrical circuit, the crowbar circuit comprising a crowbar switch switchable to selectively allow current to flow through the crowbar switch for bypassing the electrical circuit, wherein the crowbar circuit further includes:

• a secondary switching block including a switching element connected across a control electrode and a cathode of the crowbar switch, the switching element being switchable to selectively allow a non-zero voltage to be applied across the control electrode and cathode in order to either keep the crowbar switch in an off-state or switch the crowbar switch to an on-state,
• wherein the switching element is switched on in order to keep the crowbar switch in the off-state when the switching element receives, in use, a control signal, and the switching element is switched off in order to switch the crowbar switch to the on-state when the switching element does not receive, in use, a control signal,
• wherein the switching element is communicable with the electrical circuit to receive, in use, a control signal generated by the electrical circuit;
• and
• wherein the crowbar switch has a short-circuit failure mode in which, upon failure of the crowbar switch, the failed crowbar switch forms a short circuit that permits current to pass through the crowbar switch.