Creative mechanical design minimizes size and improves thermal performance
You can greatly improve the thermal performance of a power supply through creative mechanical design. Avoiding hot spots and ensuring the best possible air-flow around components that are going to get hot are both important. In the power supply described above, XP Power's CCM250 (Figure 5), has input chokes stacked above other components to save board space. Normally this might create hotspots but the low-loss design of the chokes prevents them.
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Figure 5: XP Power's CCM250 power supply uses creative mechanical design to pack a 250 W (300W peak) convection-cooled power supply into a 6 x 4 x 1.5 inch format
All heat-generating components, including the power factor correction choke, are bonded directly to the U-channel chassis, which doubles as an effective heatsink, and control circuits are placed on daughter cards mounted at 90 degrees to the main printed circuit board. In other words, full use is made of all the available space by thinking about the mechanical aspects of the unit in 3D at the outset of the design.
Medical applications are now amongst the most demanding with respect to the size, efficiency, performance and cost of AC/DC power supplies. Combining the best of proven design technologies with creative mechanical design has led recently to the introduction of units that can reach up to 95 percent efficiency, a figure thought impossible only a few years ago. Further incremental improvements are going to be harder to achieve, but the decades of experience that many engineers now have in power supply design, coupled with advances in semiconductor technology, will make them possible.
About the author:
Peter Blyth is the Industry Director - Medical, XP Power.
Peter Blyth has been with XP for more than nine years and has had various roles within the company. Blyth joined in 1997 as an applications engineer, and became the Industry Manager for Medical in 1998. Between 1998 and 2002 he was the Senior Industry Manager - Medical for Europe and in late 2002 moved to the USA to become the Industry Director - Medical for North America. Blyth is currently based in Anaheim, CA in XP's main R & D center, where his responsbilities include management of XP's medical business in North America, marketing, product development (marketing input) and technical support to customers. Prior to working at XP Blyth worked for the UK Ministry of Defence for three years and a small broadcast electronics company in the UK.
