Voltage Doubler questions

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volki

Well-known member
Joined
Jun 9, 2004
Messages
178
Location
Berlin
hi,
i'm planning to do a multi-supply-psu, and want to use a voltage doubler for 44v and 48v, in conjunction with a 28v ac xformer and a TL 738 or LM317HV as V.reg's. (i had actually started another thread for this, but with much more general questions (and not too many answers really), so this is what it actually comes down to)

the doubling circuit i want to use is an adaption of the quadroupling circuit ("double doubling") used in the gyraf g9 psu section: http://www.gyraf.dk/gy_pd/g9/g9_sch.gif

(sorry, can't find a url of a "single" doubling circuit, but it should become clear what i mean)

now my questions are

1. how big should the caps in the doubling section be for 400 to 500 mA? the larger, the better? or is a large charging cap (the one that sits right at the input of the v.reg) all that matters?
2. is a voltage doubler suitable for that much current at all (in terms of stability, unloading the caps, etc.), or should i rather use a xformer which puts out the appropriate voltage in the first place
3. should i use tl738 (like i read, no cap on the reg. leg) or lm317hv?

thanks a bunch people :thumb:
 
Is this PSU for PM1000 modules? .

I need this power supply for my 4 pm1000's, so I'll keep an eye on this thread.

Cheers,

elco
 
They're not good for power hungry stuff. I always use a power trannie with the appropriate voltage. I can get custom wound power trannies for the same price - sometimes even cheaper - than off the shelf stuff! I'd expect everybody else can too..

I wouldn't use a LM317HV. It's only good for 57V. I don't trust floating Vregs one bit. Try shorting the output and see what happens :shock:

Besides a TL783C is an exellent Vreg, if you don't wanna go discreete :green:

I'm still thinking about that other thread volki :wink:
 
elco, no, it's for a rack of different versions of cadac pre/eq's. the older ones need +44v, the newer ones +/-20v. plus +48v phantom and +24 for lamps&relays... yikes :?

I wouldn't use a LM317HV. It's only good for 57V.
couldn't find a datasheet for the hv - but thats the output voltage, right? the normal 317 can handle a max. in-out difference of 40v, so i figure the hv can do the same, meaning a max. input of 97v? would be really interesting to know.

I don't trust floating Vregs one bit. Try shorting the output and see what happens
you mean, e.g. lm317 on a zener?
prolly your answer will be quicker than me thinking about the problem myself :green: , so what happens in case of short?

the only drawback with the tl783 in comparison with the lm317 seems to be it's max current of 700mA... the to-3 version of the lm317 (and i figure the hv, too) can deliver up to 1,5A (IIRC).
 
elco, no, it's for a rack of different versions of cadac pre/eq's. the older ones need +44v, the newer ones +/-20v. plus +48v phantom and +24 for lamps&relays... yikes

Dude, that's weird :shock: . We're both in the same boat. The two projects I have on my plate right now are re-racking my 4 Yamaha PM1000 modules, which require a +44/+48 PSU and racking two ADM 770 moduels, which require +/-20v +48v and +24v for logic.

Power supplys scare me for the most part. I'll continue to scoure for schematics for these projects of mine.

Cheers,

elco
 
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