Sinrace Power Supply Technology (Shenzhen) Co., Ltd.

All power supplies generate waste heat which has to be　dissipated. The heating effect becomes greater as more components are squeezed into smaller spaces. The result of miniaturization is higher levels of heat per cubic volume of space. The heat generated by components not only passes into the air around the components but is absorbed by adjacent parts, by the PCB and by the equipment case. As a result, various parts of the system end up operating at higher temperatures than originally anticipated, which adversely affects the reliability and service life. While predictive techniques such as a fluid dynamic analysis can help anticipate potential problems caused by waste heat, there is no substitute for a combination of experience and practical evaluation to achieve the optimum thermal performance.

The two most common ways of cooling a power supply are convection cooling and forced air cooling .Data sheets for a power supply will specify either convection cooled ratings or forced air cooled ratings, or both. Where the power supply has a convection cooled rating, it is intended for use in an environment where there is free air. You must ensure that there is adequate space around and above the unit for free air convection currents to cool the unit and must also ensure that the ambient temperature local to the power supply is controlled to a level within its maximum ratings.  Power supplies with forced air cooled ratings may incorporate a cooling fan, or the manufacturer may specify the external fan cooling required to operate the unit at maximum load and ambient temperature. You should study power supply data sheets carefully early on in the design to decide if external cooling is needed.

The main difference between convection and force-cooled products is in the power density delivered for a given efficiency. Convection cooled products typically offer a lower power density than force cooled products, meaning that they occupy a larger volume. For example, a power supply on a 3” x 5” industry standard footprint may have a convection rating of 100W while the force cooled version may have a rating as high as 200W. The use of fans is growing, as more applications put increasing emphasis on achieving the best possible power density.