Many designers use regular AC-DC power supplies for these outdoor-mounted and robust applications. However, problems often arise for cooling the supplies especially in hot desert areas, such as Phoenix, AZ. These supplies are usually not rated for operation above +70 degrees C and designs often have to be modified to provide extra cooling for the power semiconductors and the capacitors. Most AC-DC power supplies that provide 300 watts and above must have an internal fan. Since fans are the least reliable component in these power supplies, designers are migrating from using conventional AC-DC power “boxes” to new PFE brick power modules.