ZERO-CURRENT SWITCHING FORWARD POWER CONVERSION WITH CONTROLLABLE ENERGY TRANSFER

摘要

An improved forward converter switching at zero-currentincorporates a mechanism for selectively regulating theamount of forward energy which is delivered to a load during eachconverter operating cycle. Energy is transferred from a voltagesource toward a load in discrete packets via a small effectiveinductance (specifically the small effective leakage inductanceof a transformer) and a capacitor, the combination of which definea characteristic time scale for the rise and fall of current suchthat a switching device connected in series with the voltagesource can be cycled on and off at zero-current. The capacitor isconnected to the load via a second inductor. By incorporating asecond bidirectional switch across the capacitor, and cycling thesecond switch on and off at appropriate times during a converteroperating cycle, the amount of forward energy transferred towardthe load may be regulated without incurring switching losses in thesecond bidirectional switching device, and control may also beasserted over reverse current flow from the load toward the secondswitch subsequent to forward energy transfer. The new topologyallows a single converter to generate a multitude of voltageoutputs, all of which may be maintained in regulation as the loadson the various outputs are varied, with no minimum load beingrequired on any output.