Understanding power supplies, their theory of operation, voltages including connected diodes and filter capacitors, is easily learned from certified textbooks on electronics and available online. - or for that matter in a classroom
And much simpler to comprehend than having to post numerous questions in a forum with its numerous and sometimes confusing and conflicting replies.
Nothing against this forum, mind you, but pick up a book and read it.
And much simpler to comprehend than having to post numerous questions in a forum with its numerous and sometimes confusing and conflicting replies.
Nothing against this forum, mind you, but pick up a book and read it.
OK, the full wave bridge only requires a single winding, but the drawback is 2 diode drops worth of power dissipation. The full-wave center tap approach gives you only one diode drop's worth of dissipation, but you have the headache of having to deal with twice as many turns to get the center-tapped winding., as well as arranging symmetry between the two winding halves (may be necessary to prevent flux walking in the transformer core for a SMPS - not so important for a line frequency XFMR). Also, the voltage stress on the diodes will be less for the full-wave bridge (by a factor of two) than for the full wave center tapped approach.
that is easy, consider a FWCT case using a 400-0-400vac secondary, now using two diode rectifiers, you will see that current conductions alternates between halves of the secondary every 180 degrees of the ac electrical cycles...so each half of the 360 electrical cycle, the alternate half is boing nothing, did you follow?
now considering the 4 diode case, with just a 400vac secondary, the the whole of the 360 degrees is utilized, no unused time here...no half of the cycle is wasted doing nothing...
then some would argue, but the four diodes have more voltage drops than a two diode fwct case,
what about it? if the B+ is 300vdc, will you be concerned about a 1.5 volt more loss? of course not!
what about it? if the B+ is 300vdc, will you be concerned about a 1.5 volt more loss? of course not!
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Indeed.
My post #24 refers to trivialities like that one.
And even if low-voltage solid state supplies are the case, a tiny drop in comparison to full B+ shouldn't matter either.
Because if it is a worry, then a proper re-design is in order, instead of nitpicking over it.
That is relatively simple, yet seems to generate endless threads of opinions and solutions.
In my case, I use 18VCT to get 11.6VDC@8A using FWCT Using a bridge, I would have a second diode drop and the voltage would be too low.
In the case of the OP, wouldn't it make sense to use the 24V transformers and create a centre tap like this? He want's a biploar 30V supply.
Kodabmx -
Using some appropriate 40V Schottky diodes in the bridge would get you about an extra volt of output, plus lower dissipation in the bridge.
Using some appropriate 40V Schottky diodes in the bridge would get you about an extra volt of output, plus lower dissipation in the bridge.
i will worry about ripple voltage more than just diode drops....
like i said, psu's can be designed to your specs...
anything psu can be engineered to your heart's desire...
like i said, psu's can be designed to your specs...
anything psu can be engineered to your heart's desire...
Well, you can scale the filter caps to your heart's desire for ripple, and the Schottky diodes will still give the advantage for output voltage and power dissipation.
Ripple voltage at 120hz, Vr= I/6.28*120*C; where I is load current, and C is in farads...
my advise, first determine your load, i.e. what amplifier are you looking to build, class A versus class AB have different considerations, it is not wise to choose when you are not sure what you are using those traffos for...never worked that way, at least for me...
like the horse and the carriage, you choose the carriage when you get your horse or horses...
btw, if you need +-30v that means under full load, so expect an open circuit voltage as high a +-35 volts or more with a certain primary line voltage, as the primary line voltage rise and fall, then your dc also follows...
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I'm using a MBR6045 Schottky FW rectifier. I couldn't find anything with a lower Vf. It's about 0.3V @ 10A.
Yeah, I'm UNwatching this now as well.
the nitpicking nerds are picking apart and worrying abou a few tenths of a volt now...
A few tenths of a volt matters on low voltage stuff though. Sure who cares on 300 volts, but in my case it's heaters and it matters. That few tenths of a volt at 10 amperes is a few watts of wasted power along with the few tenths of a volt lower output which will require larger heatsinks and more physical space.
SMPS is now ubiquitous, i use them more now than worry....who wouldn't when they had become dirt cheap....
And as I said before, nitpicking about stuff gives me a headache.
Sorry, I don't obsess over trivialities that are beyond hearing ability, and "what if" reliability issues.
If ya can't design something that can handle reasonable voltage swings, then redesign it.
Because otherwise the thing's too unstable and touchy to even deal with IMO.
even tube filaments are not so picky on voltages as long as it is within reason....why worry?