A switching DC-DC converter with wide conversion range withoutextreme duty ratios

摘要

In DC-DC conversion applications, if a large range of input/outputvoltages ratio is required, the conventional transformerless DC/DCswitching mode power converter (SMPC) topologies most operate at extremeduty ratios. This limits the operation in lower switching frequenciesbecause of the minimum on-time of the switches. To overcome thisproblem, a new class of synthesis converter is proposed which has avoltage conversion ratio according to the quadratic of the duty ratios.This not only overcomes the problem of switching operation at extremeduty ratios, but also brings an extra advantage of a wider conversionrange than a conventional converter with a step-down transformer couldhave. Furthermore, a zero-current-switch (ZCS) quasi-resonant converter(QRC) technique is also applied to the synthesis converter. It improvesthe high loss problem of the conventional pulse width modulation (PWM)converter, decreases the switching loss, and increases switchingfrequencies. Also, a new single cycle resonant converter (SCRC)technique based on ZCS/ZVS mixed switching is proposed to improve thelimited load range of ZCS-QRC. Finally, some real circuits areimplemented to test this new synthesis converter