Transistor inverter optimization employing self-oscillation for low cost and simplicity

It is shown that it is possible to extend the power range of high-frequency transistor inverters into the kilowatt region by introducing: (1) simple but effective relief of bipolar transistor switching stresses; (2) reduction and containment of transistor storage times at turn-off; and (3) effective design of the transformer and effective electromagnetic layout of the inverter. The authors first examine switching stress relief in the transistors of the inverter by previously proposed nondissipative snubbing methods, since this is a prerequisite to increasing inverter power levels. They then propose a novel nondissipative snubbing concept, which is applied to self-oscillating inverters with magnetic feedback and center-tap topology. The combined circuit is then developed further for a converter with saturation of the main transformer or saturation of the base drive transformer. This is also done for these converters in a bidirectional configuration. Enhancement of bipolar transistor turn-off and optimized electromagnetic design of the electromagnetic components and layout of the topology, which completes the development of a simple, low-cost converter configuration, are discussed.<>