which will be smaller: 120V AC or 12V DC to 43V DC?

[uoficowboy]

Hi - I need to put a 43V DC power supply on a board. Output current will be 6.6A.

I can choose from either using wall power (120VAC 60Hz) or DC power (12V DC) to power this power supply. If they both have similar output ripple specs (I would like ripple to be 10mV or less) - which will yield a physically smaller supply? I have never done an AC-DC converter, so I'm at a bit of a loss. My gut instinct says that the AC supply will be larger as it has to store so much energy to handle the zero crossing.

Thanks!

 

[spiralbrain]

my guess is 120v down to 43v will be smaller.

we are talking of 283.8 watts here


getting 12v up to 43v 6.6Amps will require a huge Push Pull design transformer. both primary and secondary will need to be pretty thick copper wires. and then the rectification.

120v to 43v will be pretty much like a computer SMPS a bit smaller.


wait a Boost converter can be smaller and with a single inductor. pretty hard to say in that case.

 

[kabiru]

Hi, stepping down 120v to 43v will be more easy cos you don't need a huge transformer, or you can simply used bulk converter which will be more efficient.

 

[uoficowboy]

my guess is 120v down to 43v will be smaller.

we are talking of 283.8 watts here


getting 12v up to 43v 6.6Amps will require a huge Push Pull design transformer. both primary and secondary will need to be pretty thick copper wires. and then the rectification.

120v to 43v will be pretty much like a computer SMPS a bit smaller.


wait a Boost converter can be smaller and with a single inductor. pretty hard to say in that case.

Is there any reason I would do a push pull design? I should have mentioned that I do not need isolation.

 

[spiralbrain]

i see you don't need it to be isolated, then a boost converter looks like the best option.

 

[uoficowboy]

i see you don't need it to be isolated, then a boost converter looks like the best option.

And that would be smaller than the AC supply, correct?

 

[spiralbrain]

I will change my mind, yes it would become smaller. I will tell you why,

I just ran a simulation on Nationals WebBench, they have three devices capable of 43v 2.5 amps(which is the max the simulation is designed for), the LM3478 - 88 and 81. The inductor they use is just 25mm across.

the inductor used : https://www.bourns.com/data/global/pdfs/PM2110_series.pdf