Patent ID: 10742129

Abstract:
In this invention we introduce the concept of a soft switching half bridge switching cell wherein the soft switching is guaranteed by the magnetizing current. Further this soft switching half bridge cell contains at least two synchronous rectifiers in the secondary which are conducting together during the dead time of the primary switchers creating a short circuit across the secondary windings, trapping the magnetizing current and release the magnetizing current to discharge the parasitic capacitances across the primary switchers when the synchronous rectifiers turn off. The secondary windings are connected to a synchronized and controlled current source. The current demanded by the current source is shaped in such way that the current becomes zero before the synchronized rectifiers turn off, allowing the magnetizing current to discharge the parasitic capacitances of the primary switching elements in a monotonic way and create zero voltage switching conditions for the primary switchers and further charge in a monotonic way the parasitic capacitances of the secondary synchronous rectifiers without ringing and spikes. By shaping the current of the synchronized current source to reach zero before the secondary synchronous rectifiers turn off, soft switching is maintained in the half bridge cell under all line and load conditions.In one of the key embodiments the current of the synchronized current source will reach zero before the primary switchers turn off. In such configuration the dead time between the conduction of the primary switchers can be reduced to the transition time.This invention is proposing different ways to shape the current of the current source, some of the configuration being forward derived and some of them boost derived. These technologies are suitable also for bidirectional power transfer and for multiple independent outputsThe family of converters derived from the soft switching half bridge cell can be applied in many power conversion applications especially at high frequency due to guaranteed soft switching in all the line and load conditions.The methodologies of shaping the current of the syncroniosed current source do apply also to other topologies such as single ended forward converters.