Reference design for low-cost off-line isolated supply 3.3V, 3 W, with std transformer

Hi,

Unfortunately custom magnetics are needed most of the time for AC-DC power supplies. Some vendors offer "off the shelf" magnetics but they may not work in your application because of the inductance being different, turns ratio, wire gauges used or even physical size.

PI Expert gives you all the custom transformer documentation necessary to send to a magnetics vendor to get samples and then finalize the order.

Good luck!

Hi, Wesley:

Thanks for replying.

The question is we will start out with small orders and the way to get low cost and short time to market would be to use standard magnetics. Using SMPS would also mean smaller size.

I can imagine I shouldn't depart from an off-the-shelf magnetics component, but, as I can't think of a requiremet more normal than ours (getting 3.3V, low power (about 3VA), from 220 VAC, not necessarily very efficient), I think it would be a good idea that P.I. develop a reference design for it, using some standard magnetic parts, and I find somewhat strange that you haven't already done it. In any case, may I suggest you to do it?

Anyway, or meanwhile, I imagine I could also adapt some low cost reference design that you have available (maybe for other output voltage) to 3.3 V. I could even add an additional low-cost LDO post-regulator.

So, do you know if there is any reference design in your catalog based on standard magnetics that you consider not difficult to adapt to 3.3V?

Many thanks.

Jose.

Hi Jose,

No we do not have any reference designs that are 3.3 V and use off the shelf magnetics. Usually for the large volumes custom magnetics are not a problem since the design is optimized for one specification which can save cost on everything on the board including the transformer.

Good luck to you!

-Wesley