Abstract: A zero voltage switching DC/DC converter comprises a transformer with two opposed primary windings between which is a center tap and at least one secondary winding connected to a load by a rectifier and capacitor filter circuit. A first terminal of a constant voltage supply is connected to the center tap of the transformer. Two switching units are each connected in series between the second terminal of the voltage supply and a respective primary winding. The switches connect the second terminal of the voltage supply alternately and periodically to one or the other of the primary windings. A control device imposes between opening of one switch and subsequent closing of the other switch a switching time during which both switches are open.

Abstract: A controller apparatus comprising a phase-locked loop circuit which includes a phase comparator and a low-pass filter connected to accept a signal representing the switching frequency of the apparatus and an external frequency signal to produce a control signal for a controllable switch serving to vary the threshold levels of a reference signal, said control signal being a function of the phase difference between the input signals. The hysteresis of the apparatus is thereby changed over a few synchronization cycles in order to pull the controller into synchronization.

Abstract: A current sensing regulator operates in a switching mode of regulation between two sensed current levels in a free-running operation, or between one of the current levels and an intermediate level in a fixed-frequency synchronization operation. The sensed current levels at which switching occurs are set through a command signal, and a comparator controls switching at the set current levels or at the occurrence of synchronization pulses.