Control systems whereby the d.c. output voltage can be controlled between its maximum positive and negative values

Claim 1

A CONTROL SYSTEM THAT CAN PROVIDE DIFFERENT VALUES OF ESSENTIALLY D.C. POSITIVE VOLTAGE, CAN PROVIDE ZERO VOLTAGE AND CAN PROVIDE DIFFERENT VALUES OF ESSENTIALLY D.C. NEGATIVE VOLTAGE FOR A LOAD AND THAT COMPRISES A PLURALITY OF CONTROLLED RECTIFIERS WHICH CAN SELECTIVELY BE RENDERED CONDUCTIVE AND NON-CONDUCTIVE, AT LEAST ONE OF SAID CONTROLLED RECTIFIERS BEING CONNECTED TO SAID LOAD AND BEING ADAPTED TO APPLY A POSITIVE-GOING VOLTAGE TO SAID LOAD, AT LEAST ANOTHER OF SAID CONTROLLED RECTIFIERS BEING CONNECTED TO SAID LOAD AND BEING ADAPTED TO APPLY A NEGATIVE-GOING VOLTAGE TO SAID LOAD, A CAPACITOR WHICH IS CONNECTED TO SAID CONTROLLED RECTIFIERS AND WHICH IS CONNECTED IN PARALLEL WITH SAID LOAD, SAID CAPACITOR STORING ENERGY THEREIN AND BEING POLARIZED IN ONE DIRECTION WHENEVER SAID ONE CONTROLLED RECTIFIER IS CONDUCTING CURRENT AND IS APPLYING SAID POSITIVE-GOING VOLTAGE TO SAID LOAD, AND STORING ENERGY THEREIN AND BEING POLARIZED IN THE OPPOSITE DIRECTION WHENEVER SAID OTHER CONTROLLED RECTIFIER IS CONDUCTING CURRENT AND IS APPLYING SAID NEGATIVE-GOING VOLTAGE TO SAID LOAD, AN INDUCTOR WHICH IS CONNECTED IN SERIES WITH SAID CONTROLLED RECTIFIERS AND THAT STORES ENERGY WHENEVER SAID ONE CONTROLLED RECTIFIER IS CONDUCTING CURRENT AND IS APPLYING SAID POSITIVE-GOING VOLTAGE TO SAID LOAD AND THAT STORES ENERGY WHENEVER SAID OTHER CONTROLLED RECTIFIER IS CONDUCTING CURRENT AND IS APPLYING SAID NEGATIVE-GOING VOLTAGE TO SAID LOAD, A TRANSFORMER THAT HAS THE PRIMARY WINDING THEREOF CONNECTED TO SAID INDUCTOR, A BRIDGE RECTIFIER THAT CONNECTS THE SECONDARY WINDING OF SAID TRANSFORMER TO THE POWER SOURCE FOR SAID CONTROL SYSTEM, A SIGNAL SOURCE THAT IS ADAPTED TO PROVIDE SIGNALS THAT CAN SELECTIVELY RENDER SAID ONE CONTROLLED RECTIFIER CONDUCTIVE AND THAT CAN SELECTIVELY RENDER SAID OTHER CONTROLLED RECTIFIER CONDUCTIVE, AND A "HOLD OUT" CIRCUIT THAT KEEPS THE FIRST SIGNAL FROM SAID SIGNAL SOURCE FROM RENDERING SAID ONE OR SAID OTHER CONTROLLED RECTIFIER CONDUCTIVE, SAID ONE CONTROLLED RECTIFIER RESPONDING TO A SIGNAL FROM SAID SIGNAL SOURCE TO BECOME CONDUCTIVE AND TO APPLY SAID POSITIVE-GOING VOLTAGE TO SAID LOAD AND TO STORE ENERGY IN SAID CAPACITOR AND IN SAID INDUCTOR, SAID OTHER CONTROLLED RECTIFIER SUBSEQUENTLY RESPONDING TO A FURTHER SIGNAL FROM SAID SIGNAL SOURCE TO BECOME CONDUCTIVE AND TO APPLY SAID NEGATIVE-GOING VOLTAGE TO SAID LOAD AND ALSO TO ENABLE SAID CAPACITOR AND SAID INDUCTOR TO RENDER SAID ONE CONTROLLED RECTIFIER NON-CONDUCTIVE, SAID INDUCTOR THEREAFTER CAUSING CURRENT TO FLOW THROUGH SAID PRIMARY WINDING OF SAID TRANSFORMER TO ENABLE SAID TRANSFORMER AND SAID BRIDGE RECTIFIER TO PUMP ENERGY FROM SAID INDUCTOR BACK TO SAID POWER SOURCE, SAID SECOND CONTROLLED RECTIFIER THEREAFTER ENABLING ENERGY TO BE STORED IN SAID CAPACITOR AND IN SAID INDUCTOR, SAID ONE CONTROLLED RECTIFIER, IN TURN, RESPONDING TO A STILL FURTHER SIGNAL FROM SAID SIGNAL SOURCE TO BECOME CONDUCTIVE AND TO APPLY SAID POSITIVE-GOING VOLTAGE TO SAID LOAD AND ALSO TO ENABLE SAID CAPACITOR AND SAID INDUCTOR TO RENDER SAID OTHER CONTROLLED RECTIFIER NON-CONDUCTIVE, SAID INDUCTOR THEREAFTER CAUSING CURRENT TO FLOW THROUGH SAID PRIMARY WINDING OF SAID TRANSFORMER TO ENABLE SAID TRANSFORMER AND SAID BRIDGE RECTIFIER TO PUMP ENERGY FROM SAID INDUCTOR BACK TO SAID POWER SOURCE, SAID "HOLD OUT" CIRCUIT PREVENTING THE SUPPLY OF SIGNALS TO SAID ONE OR SAID OTHER CONTROLLED RECTIFIERS THAT COULD RENDER THEM CONDUCTIVE BUT WOULD NOT CHARGE SAID CAPACITOR SUFFICIENTLY TO ENABLE SAID CAPACITOR TO SUBSEQUENTLY RENDER SAID ONE OR SAID OTHER CONTROLLED RECTIFIER NON-CONDUCTIVE, SAID SIGNAL SOURCE BEING CAPABLE OF MAKING THE DWELL TIMES OF SAID ONE AND SAID OTHER CONTROLLED RECTIFIER RELATIVELY DIFFERENT.