Abstract: A commutation sensor circuit for a DC-to-DC silicon controlled rectifier (SCR) chopper circuit to protect against commutation failure by determining the commutation capability of the chopper. This determination is made by testing two conditions, first, the applied voltage is measured and used to predict the commutation voltage available after a main SCR has been gated on and a commutating capacitor charged, and second, the available commutation voltage is measured after the main SCR has been gated on and the commutating capacitor charged. The first test allows the chopper to turn on if the predicted voltage when compared to the current flowing is sufficient to commutate the chopper. The second test initiates a commutation if the current flowing in the chopper reaches the maximum commutating ability of the chopper.

Abstract: A DC-to-DC chopper circuit has a first switch that is selectively actuated to supply load current to a regulated bus and bus voltage to a resonating circuit which increases the applied voltage to approximately twice the value of the bus voltage, and a second switch selectively actuated so that the current on the bus flows through the resonating circuit discharging the increased voltage stored therein to zero whereupon a freewheeling circuit permits the established current to freewheel until the next chopper cycle.