How hot is too hot? Ask sherlock

The most temperature sensitive components in power supply design is discussed. The component technology of greatest concern in regards to temperature and reliability in power supply design are magnetics, optocouplers, capacitors, integrated circuits, and solder joints. There are three issues of concern for determining how hot is too hot for magnetics. First, the saturation current in ferrite material has a soft saturation curve which can tend to obscure when a material starts to saturate. Second, designers are sometimes under the mistaken impression that maximum temperature rating is equal to the Curie temperature, and third, thermal aging. To solve this problem, the device could utilize a low loss core material. If there is any component designers should be aware of in regards to temperature, it would be electrolytic capacitors. Most companies extrapolate manufacturer's ratings to actual use environment using a classical Arrhenius equation to develop a conservative prediction of lifetime of electrolytic capacitors.