Adopting Supercapacitors in a Single-Stage Marx-Type Multilevel Supply Modulator

Multilevel supply modulation has gained interest in recent years because of the prospect of high power-efficiency. Such modulators generate several discrete voltage levels instead of a continuous output voltage. Switched capacitor converters offer multilevel operation while being supplied by a single voltage source. However, the stability of the output voltage depends on the used capacitor values. This paper is, to the authors' best knowledge, the first to report on the use of supercapacitors (SCs) in a multilevel supply modulator circuit. The large capacitance of the SCs enabled a wide output voltage bandwidth ranging from several kilohertz to several megahertz in a simple and efficient Marx-type switched-capacitor converter. A single-stage Marx-type modulator was designed on an FR-4 board and its output voltage and power-efficiency were measured. We demonstrate that the use of the SCs increased the converter efficiency. With this approach, we measured a power-efficiency above 94 % at two megahertz switching-frequency and a significantly improved output voltage stability.