Jessica Gullbrand

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.

Aero‐acoustic simulations of small scale electronic cooling blowers.

The noise emission of small radial blowers is important for the cooling of notebook systems. It has been demonstrated that airflow simulations for these radial blowers can be performed to predict the blower performance, even in the presence of inlet restrictions. The current paper presents an extension of this work to include predictions of the radiated acoustic noise. The calculated blower flow field is used as an input for a second stage aero‐acoustic prediction. This paper outlines two methods. The first method uses a free field approach based on the Ffowcs‐Williams and Hawkings analogy. The second approach constructs a rotating fan source, the magnitude of which is determined by integrating the pressure across a number of blade segments. The radiated field is then determined in a boundary element calculation, both for a free field and in the presence of the fan enclosure. Results for both methods are presented and compared to experimental data.