METHOD AND APPARATUS FOR OBTAINING SOFT SWITCHING IN ALL THE SWITCHING ELEMENTS THROUGH CURRENT SHAPING AND INTELLIGENT CONTROL

摘要

Create soft transition in selected topologies by preserving leakage inductance energy (ELI) during dead time (Td). Using several techniques to supplement energy required to discharge parasitic capacitance (Cp) of primary switchers and obtain zero voltage switching. First technique: Current pulse injection across synchronous rectifiers during and prior to Td turn off. Second technique: Tailoring magnetizing current through frequency modulation to increase ELI and use it to discharge Cp of primary switchers. At lighter load, have magnetizing current exceeding output inductor current at end of Td. Third technique: interleaving two converters, sharing coupled inductance to lower current through each output inductor below magnetizing current level at its lowest amplitude. Fourth technique: controlling turn-off timing of primary switchers and turn-on timing for secondary synchronous rectifier, thereby control ELI during Td to build enough ELI to discharge Cp of primary switchers to zero. Any/all of these techniques can be used for any application.