In this study, the performances and features of a two-phase converter with low switch voltage stress and its derivative converters are investigated thoroughly. As compared with the traditional boost converter, the voltage stresses of switches and diodes of the two-phase converter are much lower; thus, the switches and diodes with lowvoltage ratings can be used, which reduces the conduction losses. Moreover, the switches are not floating, and the input and output terminals have common ground; hence, no isolated driver is required. In addition, by utilising the ampere-second balance principle, the proposed converter can achieve current sharing without any extra control circuit, leading to simple circuit structure. In the two-phase converter, the capacitors are used not only to realise automatic current sharing but also to further improve the voltage gain. In addition, because of the advantages of the two-phase converter, many types of converters are derived from the two-phase converter. Eventually, the operating principles, mathematical deductions and experimental results for the two-phase converter are given to provide its effectiveness.

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In this paper, an ultra high step-down converter is presented, which combines one coupled inductor and one energytransferring capacitor. The corresponding voltage conversion ratio is much lower than that of the traditional synchronouslyrectified (SR) buck converter, and the proposed converter can achieve extremely low output voltage with an appropriate duty ratio. Moreover, there are three major merits in the proposed converter. One merit is that the voltage conversion ratio of the proposed converter is linear, thereby making control quite easy. Another merit is that if one of the switches fails or is abnormally controlled, a high voltage does not appear in the output terminal, so the output load can be protected. The other merit is that the proposed converter can be driven using the existing SR buck PWM control integrated circuit (IC). In this study, brief theoretical deductions and some experimental results are given to verify the feasibility and effectiveness of the proposed converter.

DC-DC converters using coupled inductors have been developed for many years. However, to prevent the high voltage spikes across main switches and diodes, the leakage inductance energy recycling will be an important issue. Consequently, a high-step-up single-switch DC-DC converter with low voltage stress is presented herein. The proposed converter integrates a coupled inductor and switched capacitors not only to realise a high voltage gain but also to recycle the leakage inductance energy. Accordingly, the voltage spikes on the switch and diodes can be clamped at some values as low as possible. Moreover, similar to the traditional boost converter, the source terminal of the MOSFET is connected to the ground. Therefore, no isolated driver is required. Eventually, the detailed analysis of the proposed converter and an experimental prototype with 12 V input voltage, 200 V output voltage and 100 W output power are provided to verify the effectiveness of the proposed converter.

In this study, a single switch isolated step-up converter is presented, which is derived from the traditional flyback converter and charge pump concept. The proposed converter possesses an output inductor, so the output current is nonpulsating. Moreover, there are several advantages of the proposed converter over the traditional flyback converter, such as higher voltage conversion ratio with only additional four passive elements, and smaller voltage and current ripples, except the same switch voltage stress. In this study, some experimental results are provided to verify the effectiveness of the proposed converter.