Low power all digital acoustic noise suppression technique for switching voltage regulators

An all-digital method of pseudo randomly varying switching frequency of a buck VR in non-linear low power modes (hysteretic and pulse frequency modulation) is proposed in order to reduce acoustic noise. The switching frequency is maintained within the audio range, instead of being increased, and hence switching losses do not increase. The random variation in switching frequency in this scheme converts tonal noise to white noise which has lower peak power and is less noticeable to humans.