One of the first laws of Physics that we learn during our schooling is that energy can neither be created or destroyed, but can only be changed from one form to another. This naturally remains true for power supplies.
For each conversation stage we will have some inefficiencies, which results in the output power always being less than that of the input power. These inefficiencies will be converted to another form of energy , and in a power supply the only medium available is to convert this to heat. However it is this heat that is the number one item for reducing the reliability of the finished design. So in order to combat this power supply designers must implement a solution to keep the effect of this to a minimum. This paper will look at a number of these methods, along with some key considerations associated with each of these choices.