New Primary-Parallel Boost Converter for High-Power High-Gain Applications

A new simple and low cost method for paralleling multiple power stages in high-power high-gain isolated full-bridge boost converters is presented. A small current balancing transformer and serial connection of transformer secondary windings provides ideal current sharing between paralleled power stages. Effective and safe parallel operation of multiple switching stages can thus be performed. By splitting high-current ac-loops into multiple smaller loops of smaller ac-currents, switching losses are reduced. Transformer turns ratio and power level is reduced, simplifying transformer design and manufacturing. Extension of the principle to other isolated boost converter topologies are demonstrated as well as extension to higher numbers of parallel operated power stages. Test results from a 3 kW experimental prototype converter are presented, verifying converter operation and demonstrating current sharing capability. Very high converter efficiency is achieved. Worst case efficiency at minimum input voltage and maximum power is 96.9%. Maximum efficiency is 98%.