PLC internal power supply


Thread Starter

Suttipan Limanond


I'm designing a PLC and wondering what kind
of internal power supply (i.e., linear or
switching) that various PLC manufacturer normally
uses. Any pro and con of these two types,
as far as the PLC is concerned?

Thank you very much,

Suttipan Limanond.
The excellent value for money S7-200's have the option of a 220V to 24V SMPS in tbier allready little case.

Other modern products are similarly equipped. This supply is sufficient for supply a small amount of external periphery (24V relays, sensors

Swithcers are much smaller, and produce less heat. They are also noisier (emc requirements) and require input filtering to meet input harmonic
requirements. In Europe at least, you would also need to satisfy various safety requirements if you are tacking 220V into the box.

It requires a lot of skill and experience to make an off-line SMPS, let alone meet all the certification requirements. I would suggest you
design the case such that it can incorporate a ready made unit from a specialist manufacturer. With the exception of high volume producers,
most people rely on OEM PSU modules.