Suppression of harmonic spikes in switching converter output using dithered sigma-delta modulation

In this paper, dithered sigma-delta modulation is proposed as an effective modulation scheme for a switching converter, to suppress harmonic spikes. The proposed scheme has a simple configuration, which comprises a first-order sigma-delta modulator and a random dither generator. The first-order sigma-delta, modulator produces a switching pulse waveform that has the same low-frequency component as the reference input. Also, the random dither disperses the switching frequency of output pulse waveform, which results in reduction of harmonic spikes. The relationship between the harmonic spectra and sampling numbers per switching cycle is studied through computer simulations, and performance is confirmed in an experimental setup.