Fast FPGA prototyping to explore and compare new SPWM strategies

Abstract

This study presents a Flexible Test Bench (FTB) implemented with FPGA that synthesises of a large number of strategies that apply “Spread Spectrum” to reduce the energy of the fundamental harmonics present in a conventional Pulse Width Modulation (PWM). The FTB not only incorporates most of the known spread spectrum techniques but also allows to combine them and even to easily create new ones, thus providing a highly flexible test bench. The FTB has been described in standard VHDL, so it can be synthesised using any synthesis tool, and the number of logical resources used by each of them can be determined according to the spread spectrum strategy configured in its registers. Therefore, a tool is available to choose, according to the spectral response and the consumption of logic resources, the most suitable PWM spread spectrum strategy for each application. The particularity of the proposal is to have a unique hardware platform that allows the comparison of different techniques under the same physical implementation conditions since geometry and physical location are important when evaluating the conducted and radiated emission of the circuits. Another objective of our FTB is to solve in a unified way all the numerical aspects present in the FPGA-based implementation so that the numerical ranges and roundings used affect all the implemented techniques equally.