How to Calculate Smoothing Capacitor Size for 120VAC to Multi-Output Linear Supply?

POWER!,


Or the lack of it in this case.   I am designing a power supply form scratch and want to run the mains 120VAC as the source.   
120VAC to step down XFMR ~16VAC, to Full Bridge, then to multiple switch supplies, than smooth it out with some linear regulators.  

First question is for the smoothing capacitors i'm using in the AC-DC part.   I know to get them rated at above the voltage i'm expecting, 170V so with out the step down to play it safe if i get rid of it,  caps but how large of Capacitance do i want to get.  i've popped a couple smaller ones just for fun but kinda dont want to have that happen with the more expensive ones i'm planning on getting.  
Do i need to spend a large amount of time figuring out the resistance of the switching part of the circuit to calc the RC constant of the circuit to have a better judge of the minimum capacitance I require in the circuit, or is more capacitance the better?  
Does the loads through the Linear regulators going to be important to calculate into this consideration as well?


That's a lot but thank you all for the help.

Justin there are others here who can better advise you on the switching regs - as Rick has pointed out to other posters Texas Instruments Webench online SMPS designer can help you here.It sounds like you want a good old hunk of iron transformer to get down to your 16V. But then you mention 170V caps so it seems like you want to go switch mode between 120VAC and 16VDC?  if so then as you say go for overrated caps (capacitance and voltage ratings) , go for 105 °C types not 85° types, and go for the lowest ESR you can.  These caps are one of the common points of failure in most SMPSs (and the reason a lot of LED TVs end up in landfill...).Once you are at 16VDC the rule of thumb is 2000 uF for every Amp you draw from that.  Bear in mind though that if you have a 5V switching reg off that, with good efficiency, it will only draw around 1/3 of the 5v current from the 16V supply (ie 5V 3A would draw ~1A from the 16V supply).I'm hoping someone better than I can advise you further...

Hi Justin-You probably don't need to follow the switching regulators with linear regulators.What are your requirements?  What voltages do you need, and how much current from each output?  Will you be building one of these or millions of them?Off-line open frame switching power supplies are very affordable.  It may be better to just use several of those - unless your goal is to learn more about power supply design..-Rick

Thanks,  I have a xfmr that is a step down from mains to the 16v ac supply than  to dc.  The idea is to supply 4 or 5 switching supplies to provide  multiple set voltage supply’s points with one viarrible voltage source point.  Basically a BACPS. ( big ass custom power supply). For my home bench.  Plus to work at becoming more experienced at design of power supplies.  I am planning on only having two sources out of the 4-5 providing power at a time, each providing a max of an 1 amp.   Ex:  one 5VDC and one 12VDC supplying power to a set up.Or a +-15  for op amps

Thanks,  I have a xfmr that is a step down from mains to the 16v ac supply than  to dc.  The idea is to supply 4 or 5 switching supplies to provide  multiple set voltage supply’s points with one viarrible voltage source point.  Basically a BACPS. ( big ass custom power supply). For my home bench.  Plus to work at becoming more experienced at design of power supplies.  I am planning on only having two sources out of the 4-5 providing power at a time, each providing a max of an 1 amp.   Ex:  one 5VDC and one 12VDC supplying power to a set up.Or a +15v 

Thanks,  I’ll look into the TI site design software.  
I work with a lot of utilities but I like to work on the smaller home per supplies and controls for it.  Thanks for the help.