Ac to dc rectifier circuit with rapid turn-off in case of overcurrent through the load circuit

Claim 1

AC to DC rectifier circuit with rapid turn off to prevent damage in case of excessive current through a load circuit, having a transformer (5) adapted for connection to a source of AC; a plurality of main rectifier elements (8) connected to the secondary (6a, 6b) of the transformer and adapted to be successively conductive and connected to the load circuit; means (19, 19a) sensing overcurrent condition in the load circuit and providing a control output indicative of such overcurrent condition; and a rapid turn-off circuit for the rectifiers comprising a series circuit including a controlled switching element (10) having a control input (10a) connected and responsive to the control output of the sensing means, the controlled switching element being connected to be normally non-conductive; an energy storage device (11) having one terminal connected to the other terminal of the switching element; and a pair of connections (12, 18) from the other terminal of the storage device and forming a pair of other terminals of the series circuit, one terminal of the series circuit being connected to the transformer-rectifier element connections and the sEcond other terminal being connected to the transformer so that, when the overcurrent condition is sensed, the switching element will be rendered conductive and the energy storage device will deliver its stored energy and supply reverse current over said one terminal in counterflow against the normal current flow direction of the rectifier elements to rapidly switch off the rectifier elements and thus remove power from the load circuit, and current from the other terminal will maintain current through the controlled switching element even after turn off of the previously conductive rectifier.