Circuit-oriented modeling of nonlinear device capacitances in switched mode power converters

The existence of parasitic capacitances surrounding switching devices has been well established in the field. These capacitances are capable of having significant impact on the analysis, design, and performance of switched mode power supplies through increased switching loss or altered converter dynamics in the soft-switched case. As power converters continue to move to higher frequency, these effects become more pronounced and must be taken into account in converter design and analysis. This paper examines the nonlinear voltage-dependence of switching device capacitances and proposes a circuit-oriented analysis technique that allows the parasitic capacitances to be replaced with linear equivalents. The developed linear equivalents are then used with traditional circuit analysis to experimentally confirm their ability to accurately model converter operation of an example converter which exhibits significant loss and dynamic effects from device capacitances.