A Digitally Controlled Low-EMI SPWM Generation Method for Inverter Applications

This paper presents a digitally controlled way of generating the sinusoidal signal with less memory consumption. Moreover, this paper also presents a new switching frequency modulation technique. This technique utilizes the concept of spread spectrum frequency modulation that is used to suppress the electromagnetic interference (EMI) caused by high switching frequencies. Measurement results at the output sine pulse-width generation show that when the spread spectrum technique was applied to the conventional triangular wave and the fundamental, second, and third harmonics of switching frequency were reduced, respectively, by 12.8, 11.2, and 16.4 dB trading off with the slight increase in total harmonic distortion (THD) of 0.092% from a THD of 2.34%. While in the inverter output, there was a 14-dB reduction in EMI peak in exchange to 0.12% increase in THD from a THD of 2.57%.