Comparison of Ripple and Stress of a Non-isolated Basic Quasi-Z-Source Converter with a Diode or Inductor as Output Filter

In this study, the electrical characteristics of a non-isolated basic quasi-Z-source converter (qZSC) with an inductor output filter and a non-isolated basic qZSC with a diode output filter are compared. The electrical characteristics of the non-isolated qZSC are the input current and voltage ripple of the qZ-network, the current stress of the output filter, and the efficiency of the converter. The circuit equation of each converter was obtained, and the voltage gain, maximum current, minimum current, and required element ratings were calculated. Under the conditions of input voltage 80 V and output voltage 120 V, the shoot-through duty ratio for the same voltage boost gain was much lower for the diode filter qZSC, and the input current, qZ-network capacitor voltage, and the required minimum element ratings were also more advantageous than the inductor filter qZSC. However, in terms of the output filter, the inductor filter qZSC has a current stress advantage over the diode filter qZSC. A DSP-based experiment was performed to verify the validity of this study. The capacitor voltage and inductor current of the qZ-network and the voltage of each converter and the current of the output filter were compared under the condition of an input voltage of 80 V and an output voltage of 120 V. Finally, as a result of comparing the efficiency of voltage gain change or input voltage change for the same load and the efficiency according to load change at a constant duty ratio, it was found that the diode filter qZSC is advantageous by about 1%.