| Abstract |
This paper suggests a current-fed double inductor push-pull converter for the use as a preamplifier stageof a constant current charger for HV capacitors. With this converter it is possible to offer a wide inputvoltage range for the use in mobile applications with a 24V or a 48V battery. A novel snubber techniquefor current-fed converters is introduced, so that transistor conduction losses can be reduced significantly.The main part of the snubber is an active transformer short-circuit which eliminates the negative impactof the transformer leakage on the MOSFETs Drain-Source Voltage, by forcing the beginning of the commutationprocess earlier. Due to the reduction over the overvoltages MOSFETs with smaller BreakdownVoltage can be used leading to smaller On-Resistances. In a prototype the conduction losses were reducedto 55 \%. The introduction of the transformer short-circuit can be achieved easily and inexpensiveby replacing two diodes of the output rectifier bridge with MOSFETs.Additionally a small signal model of the current-fed double inductor push-pull converter is derived. TheHV capacitor load profile demands particular requirements to the control, which will be closer observed.It will be shown that the best solution is a feed-forward of the link current to the input stage control.Otherwise a constant control deviation of the link voltage can occur. |
