Experimental Evaluation of Switching Losses in IGBT based Resonant Switched Capacitor DC/DC Converters

Abstract:
Maintaining equal voltages during the charging and discharging processes is vital for the series-connected DC-link capacitor banks. Dynamic balancing is essential for such capacitor bank’s reliability, lifespan, and the correct operation of the converter. A Resonant Switched Capacitor Converter (RSCC) can be used to dynamically equalize the voltages between two series connected capacitor banks with theoretically no switching losses due to zero-current switching (ZCS). This paper examines a RSCC, which has the potential to increase the operating frequency in order to reduce passive elements size, weight and cost. However, switching frequency related losses due to the practical limitations of semiconductor devices drastically limit the operating frequency, reducing the potential benefit of such resonant converters. The issues with ZCS using Silicon IGBT implementation have been brought to light, necessitating the right choice of optimum switching devices, specially at quasi-hard switching turn off conditions. This paper presents a comparison of experimental switching frequency related losses between Reverse Conducting (RC) IGBTs and Soft Switching (SS5) IGBTs applied in a RSCC. Experiments are conducted at various switching frequencies, voltages and various current levels which has been presented to emphasize the significance of semiconductor device selection and optimum operating frequency for overall losses.