Common Ground Quasi-Z-Source Series DC–DC Converters Utilizing Negative Output Characteristics

This article presents a general method to obtain the improved common ground quasi-Z-source series dc–dc converters. Utilizing the negative output characteristic of the quasi-Z-source converter (QZSC), the output voltage of the improved converter is the sum of the input voltage and the output voltage of the original QZSC, which means that part of the energy is directly supplied by the input voltage source without passing through QZSC. Therefore, compared with the original QZSC, the proposed improved converter has advantages such as lower voltage stress, lower current stress, higher voltage gain, and higher efficiency. More importantly, all these improvements are obtained with no obvious drawback. No additional component is required, the input and output remain common ground, and if the input current of the original converter and the load current are continuous, the input current of the improved converter is also continuous. In order to prove the feasibility of the proposed method, first, the improved converters of three existing QZSCs are obtained. Then, the operation principle, parameter design, and comparison are introduced in sequence. Finally, the above analyses are verified by simulation and experiment results.