AC/DC power supplies are straightforward - connect the input to an AC power source, which can be high voltage mains or a wall outlet. The power supply then converts the AC power into DC power. When selecting an AC to DC power supply, it’s important to determine the output power and voltage required for the system so the correct power supply can be used.
Efficiency is key when selecting an AC to DC power supply. These power supplies take a high-voltage AC voltage and usually step it down to a much lower voltage. Of course the simplest way to do this is with a set of resistors, transformers, and capacitors, but the result would be an adapter that give off waste energy in the form of enough heat to melt an iceberg.
The best AC to DC power supplies have the highest efficiency. A switched-mode configuration increases efficiency, which lowers heat while saving energy. Efficiency is given as a percentage and can be as low as 60% to as high as 94%.
Linear regulated AC/DC power supplies offer an output voltage that is cleaner, more stable, and much more precise compared to Switched Mode Power Supplies (SMPS). Because of this output stability they are ideal for sensitive electronics equipment. However, linear power supplies are inefficient and so can generate quite a lot of heat and can get large and heavy.
Linear AC/DC power supplies have a simple topology. AC power is first fed to a step down transformer, and then to a bridge rectifier. A three-terminal voltage regulator smooths the signal into a nice, stable DC output. In linear regulated power supplies almost all the excess power is dissipated as waste heat. This heat must be taken into account in the design of the power supply and can require air vents in the power supply housings, and sometimes a fan. With very low ripple and high reliability, linear regulated power supplies are optimal for sensitive low power electronic equipment.
Many DIN Rail power supplies, which are mounted on a DIN rail, are AC/DC power supplies. DIN rails are made to standard sizes and are used to mount different industrial power devices including circuit breakers, signal conditioners, switchers, timers, and sophisticated programmable logic controllers. All this equipment must be powered, hence a DIN-rail mountable power supply is used.
These power supplies are very rugged and are built to work under very harsh industrial conditions. Multiple safety features are built in including short circuit protection, overvoltage protection, overtemperature protection, and overload protection.