Switched-coupled inductor cell for DC-DC converters with very large conversion ratio

By replacing the inductor in basic converters by a coupled-inductor, and adding one diode, new converters with a small count of elements and a high conversion ratio are obtained. The additional diode helps to circulate the leakage inductance energy to the load in a non-oscillatory manner. This diode conducts for a short period of time. The transistor turns on/off with soft-switching. The diodes turn on with zero-voltage switching and turn off with zero-current-switching, their reverse-recovery problem is alleviated. A switching-coupled inductor boost converter is studied in detail, and a family of DC-DC converters (boost, buck-boost, C-uk, Sepic, Zeta) based on the new switching cell is then presented. The dependence of the voltage gain on the magnetic-coupling coefficient and turns ratio of the coupled inductor is studied. The influence of the load value on the voltage conversion ratio is discussed based on an exact analysis, which avoids assumptions of ideal elements. Computer simulation and experimental results confirmed the theoretical expectations.