I have a project that for past versions I have been using a DC power supply. To take it to the next level, I would like to the AC to DC conversion on my PCB. This is my first time ever specking out parts to do this and I am wondering if I have the right process. I will take you through my thoughts.
I currently use a LM2596-ADJ switching voltage regulator with an input voltage of 12.10 VDC I saw on average a 78 mA current from my circuit. The highest peak I saw was a fairly rare 140 mA. So that brings me to a peak power consumption of 1.69 Watts (Atmega328p, SIM800 and some other small stuff).
With that I went to mouser and filtered for any transformer that accepts a 110-120VAC input and has anything between a 2-3.5 Watt rating. The cheapest one was the F36-065-C2 datasheet http://www.mouser.com/ds/2/410/36-065-C2-263502.pdf.
Now for the bride rectifier. I discovered that bridge rectifiers are cheap and can be small with a high amperage. With that I chose a large 1.5 A in a SMT package and chose the cheapest one the ABS15M RGG. datasheet http://www.mouser.com/ds/2/395/ABS15J%20SERIES_A13-335344.pdf
Okay then I drop a 470uF cap on the input line to my voltage regulator and I should be good to go right????
So my questions: Was my thinking correct with the transformer and rectifier? How big of a filter cap should I put on the incoming line? Is there a rule of thumb or calculation? Why is it that my 1 cubic inch tablet charger can put out 5 watts and I spec out a transformer twice that size and it is much lower power? How do they make it so small? In the end I want a cheap AC to DC conversion and not have it be too massive. (I can make the size of what I specked out work if needed)
Thanks for your help!