A Noise-Shaped Buck Converter Using a Noise-Coupled Second Order Delta-Sigma Modulator

This paper proposes a novel approach to address the issue of switching noise in buck converters caused by traditional pulse-width modulator (PWM) controller. The proposed solution uses a noise-coupled second order delta-sigma modulator (DSM) to replace PWM which can eliminate output spikes. This converter is designed for 15 V to 5 V conversion operating at a switching frequency of 50 kHz. A Simulink simulation compares the performance of PWM and the noise-coupled second order DSM. The output waveforms and power spectrum densities (PSD) of DSM and PWM controllers are compared to demonstrate the effectiveness of DSM in reducing noise spikes. The outcome of this simulation shows that although DSM has a higher ripple voltage (19.5 mV) in light load than PWM (11.97 mV) in light load, its ripple voltage (17.0 mV) is lower than PWM (21.2 mV) in heavy load. In addition, the output harmonics are much less in DSM. Therefore, the noise-coupled second order DSM-based controller is more efficient in reducing the switching noise and improving the output quality of the buck converter.