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.
