DC-DC High Voltage Gain Switched Capacitor Converter With Multilevel Output Voltage and Zero-Voltage Switching

This paper presents the concept and results of a novel resonant DC-DC converter which achieves high voltage gain at a low number of utilized switches, low voltage stress on transistors, ZVS and ZCS operation, high efficiency and variable voltage gain. The converter uses resonant switched-capacitors (SC) circuits with five switches which allows it to reach a six-fold voltage gain. By the application of adequate switching patterns, seven levels of voltage adjustment can be achieved. The basic operation mode of the converter is at zero current switching (ZCS) but a part of the existing transitions can be switched-on at a zero drain-source voltage. Zero voltage switching (ZVS) allows for a reduction of
$C_{\mathrm {oss}}$
losses and a decrease in disturbances of voltages and currents. In the proposed converter, voltage stress on switches are noticeably lower than the output voltage which is beneficial from viewpoint the cost reduction and switching quality improvement. The converter output stage consists of two series connected capacitors which allows for a supply of 3-level NPC inverters. Resonant inductors, used in the proposed topology, store very low amount of energy and their volume is significantly lower than in case of chokes typically used in switch-mode converters. Qualities of the converter such as low switch count, efficiency, ZCS and ZVS operation as well as voltage gain variation are demonstrated in this paper. Furthermore, an impact of MOSFET transistors type on the efficiency of the converter is investigated. The design based on low
$C_{\mathrm {oss}}$
superjunction (SJ) MOSFETs is compared with the implementation where
$R_{\mathrm {ds(on)}}$
of switches is minimized. Due to low voltage stress, application of Schottky rectifiers is also demonstrated in the converter. The concept of the topology and switching patterns is verified by the results of analysis, simulations and experiments.