Transformer type versus switching type wall plug in power supply reliability

KatyBri

I'm building a STAMP based (actually two STAMPS in it) project which is expected to last 20 years or more.

I'm trying to decide weather to build my own power supply in the project using discrete components (which takes up space) or instead using a wall plug in type power supply.

I've noticed there are the old standard transformer based power supplies and newer switching types (which appear smaller in size than their trnasformer counterpart).

I need long term reliability and was wondering if anyone knows if the switching units are as trouble free and last as long as the transformer units?

Alan Bradford

Hi,

I use the TI switching regulators in my StamPLC boards.
PT5101 series. You can get them from Digikey and many others as well.
I dont know about 20 years, the longest one I have running is about 5 years.
I do have a few boards that use the good old 7805 Linear Regulators.
The oldest is 10 years old.
These boards are in industrial applications with lots of electrical noise.
I mount the transformer/bridge/filters right on the PC board.
Wall Warts are not an option in my applications.

The Switching regulators cost around $12-$13.
They are more efficient and in the long run will be cheaper than a linear (@$2 each).

Good Luck,
Alan Bradford
Plasma Technologies
www.plasmatechnologies.com

RDL2004

I have a couple of those newer switching type AC adapters. They're pretty good. I like the fact that they are regulated and that the small size doesn't block other outlets on power strips. Long term reliability is an unknown, but it will be easier to replace a "wall-wart" than to open a case and repair a built-in power supply.

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- Rick

LoopyByteloose

Our modern dilemma with new products is that long-term reliability is projected by the designer's experience and by mathimatical models.

Nothing really replaces a proven track record. Other than that, switching supplies historically have had two negative attributes when compared to linear regulated.

One is that they needed a minimum load to be stable. And, they may interfer with some devices because they switch at a frequency that can find a harmonic with the microprocessor [noparse][[/noparse]like Analog to Digital measurements].

But, I suspect that at one amp and less, good filtering and low output make both issues not significant. New design may have eliminated the problems.

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···················· Tropical regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan

phil kenny

Personally, I would opt for the old fashioned non-switcher mainly because
highly reliable switching power supplies are very difficult to design unless
you do this for a living.

The single most important design factor in extended life electronic systems
is to adequately derate all components. Don't run them above 20-25 percent
of their rated specs. This is particularly true for any electrolytic capacitor.

If the power supply is likely to be exposed to the weather, you may want to
consider sealing or encapsulation. However, be careful that this doesn't
impact the thermal dissipation too much.

phil

Alan Bradford

Hi,

The TI PT5101 Series can be used in place of a 7805. Just throw a rectifier, coupla' Caps and the TI Regulator and Voila...Instant power supply.

Real easy, and efficient.



Alan Bradford
Plasma Technologies
www.plasmatechnologies.com