Hey!

I need to supply 5v (100-200Milliamp) down stepped from 230v mains AC to my embedded MCU application that would drive some external components (ex. 4x Sugar cube relays).

I don't want to use transformers due to cost and size reasons. So can someone provide me some advice on a AC-DC down-step circuit using semiconductors only.
First I thought a big resistor with rectifiers will do but that may be risky,also I need to keep the ripples to minimum or else it may interfere with the MCU operation.

 

For this amount of current, it is usually cheaper to buy than to make it. Not sure which part of the world you're in. But in my place I can easily buy those USB low voltage charger for handphones for less than 3 US$.

Besides we are not allowed to discuss transformer-less power supply from the AC mains. It is against the ToS of this forum.

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Allen

 

Hello,

You could use something like this:
http://www.digikey.com/product-detail/en/RAC02-05SC/945-1401-5-ND/2652154

Bertus

 

You can get cheap small SMPS plugpacks (wall-warts) that output regulated +5v DC.