Power-Supply Volume Reduction via Forced Convection

The continuing miniaturization of telecommunications equipment has been unaccompanied by a decrease in the demand for processed power. The result is a decrease in the system volume allocated for power conversion equipment with no corresponding decrease in processed power requirements. Forced-convection cooling of power supplies has traditionally been disregarded for considerations of reliability, efficiency, and acoustics. In light of continuing miniaturization, however, this tradition must be reassessed and any disadvantages must be weighed against potential volume reduction. This study analyzes the thermal performance of typical classes of power components and circuits in order to identify and quantify the thermal parameters that determine power supply volume. The degree of volume reduction possible is governed by the thermal and volumetric topology of the power supply under consideration. Forced convection is least effective for circuits dominated by magnetic components and filter capacitors, and is most amenable to those dominated by power semiconductors. Forced-air cooling of conductively coupled baseplates may be the most volumetrically effective method for cooling power supplies. Design relationships for this application are defined and presented.