Study On Input-Parallel Output-Parallel Connected DC/DC Converters With Cross Rectifier

The combined DC/DC converter can meet the high capacity, high power density, high reliability requirement of converter. However, the mismatches in module parameters are unavoidable, and the mismatches will influence the output power of each module, so the study of the voltage/current sharing between modules is of great importance. The methods can be classified into two types:the control voltage/current sharing method and the automatic voltage/current sharing method.There are four basic types combined converter. The relationship between the input voltage/current sharing and the output voltage/current sharing, is generalized. And the relative control strategies of the four basic combined converters are also represented. Automatic voltage/current sharing methods build the characteristic of automatic voltage/current sharing between modules through changing the topology of the module, the combined method, the connection way and the control loop. The latter can improve the reliability of the system as no voltage/current sharing control loop is needed.This paper proposes an input-parallel output-parallel converter with current automatic sharing characteristic. The basic module can be half-bridge converter or full-bridge converter, the secondary sides of the transformers adopt the cross rectified connection. The operation principle of the converter proposed is analyzed, and steady current sharing can be realized, the difference in module parameters has no effect on the steady current sharing. By analyzing the small signal model, it is concluded that the mismatches in the filter inductance and module resistance may influence the dynamic current sharing, the left parameter mismatches has no effect. The simulation and experiment results verify the theoretical analysis. The module can also use full-wave rectifier, then the mismatches in parameters will influence current sharing, but basic equal current sharing can guaranteed with little parameter mismatches.Multiple modules should be combined to expand the power stage of the combined converter, and the recycle cross rectifier connection can be used. The operation principle is introduced. It is concluded that the steady current sharing can be achieved using the average space state model. A prototype included three modules is built up, and modules share the output current.