Analysis of starting circuits for a class of hard oscillators: two-transistor saturable-core parallel inverters

One of the important practical considerations in using static dc to square-wave inverters such as the circuit shown in Fig. 1 is the reliable starting of oscillations. It is generally known that inverters of this type are not self-starting under relatively heavy load conditions. Starting under load generally is achieved through an externally added starting circuit. A variety of starting circuits have been reported from time to time in the technical literature, e.g., Ref. 1, 2 and 3. Such circuits constitute an important ingredient in many of today's state-of-the-art power processing systems. The present paper analyzes various starting circuits from the point of view of nonlinear circuit theory. The results of this analysis provide guidance in the design and selection of starting circuits and lead to a better understanding of the rather large class of inverters (4) which have circuit configurations similar to that shown in Fig. 1.