Abstract: A scheme for detecting reduced source of voltage of a controlled switching power supply including a transformer employs the inherent insolation characteristics of the transformer to yield an isolated alarm signal indicative of a failed or inadequate source voltage.

Abstract: A method of adaptively controlling the time of rendering the individual controlled devices of a controllable power conversion bridge includes the sensing of the instant in time at which the current from the bridge to a load becomes discontinuous. From the time of this sensing, the time period to a predetermined time such as a normally calculated time of rendering the controlled devices conductive is derived. This time period is then multiplied by a multiplier and the resultant product is combined with the predetermined time to provide an actual time of rendering the controlled devices conductive.

Abstract: A method and apparatus for use in conjunction with a power conversion system employing a plurality of switching elements for controlling the electrical power supplied to a load from a source includes the sensing of the instantaneous voltage furnished to the load and providing a signal representing the time derivative of the sensed voltage. The derivative signal thus developed is compared with predetermined reference values to develop output signals which are logically combined to provide a final signal representative of the instant in time at which one of the switching elements is commutated (turned off).

Abstract: Overcurrent protection is obtained in a push-pull network by circuitry repeatedly comparing signals indicative of the instantaneous current flow through the push-pull switching elements with a synchronized reference signal whose value is preferably made to decline during the ON periods of the current switches. Thus, the reference signal may initially be set relatively high to accommodate a moderately high in-rush transient and then to decline to lower levels over the remainder of the time the switching elements are on. At any time that the current signals exceed the compared to reference value, the corresponding current switch is deactivated as a protective measure.