Abstract
Figures-of-Merit (FOMs) are widely-used to compare power semiconductor materials and devices and to motivate research and development of new technology nodes. These material- and device-specific FOMs, however, fail to directly translate into quantifiable performance in a specific power electronics application. Here, we combine device performance with specific bridge-leg topologies to propose the extended FOM, or X-FOM, a Figure-of-Merit that quantifies bridge-leg performance in multi-level (ML) topologies and supports the quantitative comparison and optimization of topologies and power devices. To arrive at the proposed X-FOM, we revisit the fundamental scaling laws of the on-state resistance and output capacitance of power semiconductors to first propose a revised device-level semiconductor Figure-of-Merit (D-FOM). The D-FOM is then generalized to a multi-level topology with an arbitrary number of levels, output power, and input voltage, resulting in the X-FOM that quantitatively compares hard-switched semiconductor stage losses and filter stage requirements across different bridge-leg structures and numbers of levels, identifies the maximum achievable efficiency of the semiconductor stage, and determines the loss-optimal combination of semiconductor die area and switching frequency. To validate the new X-FOM and showcase its utility, we perform a case study on candidate bridge-leg structures for a three-phase 10 kW photovoltaic (PV) inverter, with the X-FOM showing that (a) the minimum hard-switching losses are an accurate approximation to predict the theoretically maximum achievable efficiency and relative performance between bridge-legs and (b) the 3-level bridge-leg outperforms the 2-level configuration, despite utilizing a SiC MOSFET with a lower D-FOM than in the 2-level case.
Highlights
Figures-of-merit (FOMs) are ubiquitous and powerful, and are used widely to compare candidate power semiconductor materials and realized devices
Using the X-FOM, we identified that multi-level topologies can lead to higher performance, both because of the higher device-level semiconductor Figure-of-Merit (D-FOM) of lower voltage devices and the switching frequency multiplication with smaller voltage steps that results from the nature of multi-level structures
While the D-FOM only refers to the performance of an individual semiconductor device, the XFOM quantitatively compares the performance of individual devices of all voltage ratings across a number of topologies, with a particular focus on multi-level structures here
Summary
Abstract—Figures-of-merit (FOMs) are widely-used to compare power semiconductor materials and devices and to motivate research and development of new technology nodes. We combine device performance with specific bridge-leg topologies to propose the extended FOM, or X-FOM, a figure-of-merit that quantifies bridge-leg performance in multi-level (ML) topologies and supports the quantitative comparison and optimization of topologies and power devices. The D-FOM is generalized to a multi-level topology with an arbitrary number of levels, output power, and input voltage, resulting in the XFOM that quantitatively compares hard-switched semiconductor stage losses and filter stage requirements across different bridgeleg structures and numbers of levels, identifies the maximum achievable efficiency of the semiconductor stage, and determines the loss-optimal combination of semiconductor die area and switching frequency. To validate the new X-FOM and showcase its utility, we perform a case study on candidate bridge-leg structures for a three-phase 10 kW photovoltaic (PV) inverter, with the X-FOM showing that (a) the minimum hard-switching losses are an accurate approximation to predict the theoretically maximum achievable efficiency and relative performance between bridge-legs and (b) the 3-level bridge-leg outperforms the 2-level configuration, despite utilizing a SiC MOSFET with a lower D-FOM than in the 2-level case
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