many rectifiers-one secondary

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kooma

Well-known member
Joined
Jan 26, 2006
Messages
473
Location
Espoo-Finland
Been building an external transformer case for preamp,
now adding some sort of pilot light got me thinking;
is it ok to add many rectifiers in paraller?
ie. one rectifier for leds etc and still supply ac to main unit?

I've always used leds in units on dc
or neon lamps on 230ac switches.

found some "mains led" circuits that have cap before diodes,
but I guess it's more for filtering possible dc-component from mains..
 
There's no particular issue, as long as you don't overload the secondary; I mean, if you add many rectifiers and smoothing caps, you may have a huge turn-on current.
One thing you should be aware of is that the resulting DC rails will not be independant. In a recent thread, the OP describes an issue where he has created a 0/+24V and a -15/0/+15 rails from a single secondary and the two different "grounds" are conflicting.
 
abbey road d enfer said:
There's no particular issue, as long as you don't overload the secondary; I mean, if you add many rectifiers and smoothing caps, you may have a huge turn-on current.
One thing you should be aware of is that the resulting DC rails will not be independant. In a recent thread, the OP describes an issue where he has created a 0/+24V and a -15/0/+15 rails from a single secondary and the two different "grounds" are conflicting.

Thanks, thought so:)
so with floathing ground everything is ok,
but I'd have to match polarity(within psu and preamp) if I wanted to ground things..

I know this is simple thing, but I never thought about it
or how bridge rectifier is seen on ac side

btw.this attachment started all this
 

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kooma said:
found some "mains led" circuits that have cap before diodes,
but I guess it's more for filtering possible dc-component from mains..
Not really; a capacitor is an elegant way of dropping voltage, since it's zero dissipated power (current in quadrature with voltage). With some thinking, you can drop the voltage from 115/230 to something like 10-12V, which allows the use of low-dissipation resistors.
 
If you have separate rectified supplies, then the DC supplies and their connected circuitry need to be kept isolated from each other to avoid interaction - so you shouldn't connect any part of those two circuits  (unless you know for certain what will happen).

What are you making that needs floating power supplies?
 
trobbins said:
What are you making that needs floating power supplies?

I dont need it, this was more like reference to if I would have a mystery box that needs ac,
then my other grounds should be floating( like in my case leds are..)
 
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