Can an IC chip raise B+ voltage for a preamp?

[smackoj]

I built a one-tube preamp that uses an isolation transformer to produce about 140 vdc output. I was wondering if there is an IC chip or ? that can boost/double the voltage like the mini ones do for the stomp boxes (charge pump ICL7660)?  I don't want to retrofit a differ. PT if possible because I like the smaller size, less bulky and heavy the preamp is now. Just a 'what if' kinda question, the preamp works fine but I have another one that uses a Champ style PT and it boosts the signal much better for the power amp to reproduce.

 

[AZJimC]

Check out voltage doubler circuits.

[DummyLoad]

charge pump ICL7660

http://www.connectable.org.uk/wp2/?page_id=609

uses C-W multiplier controlled by IC.

you don't mention of desired current supply...yes, i gather it's small since it's a preamp, but with C-W multiplier small I load is non-trivial.

personally, i'd use a delon doubler. 

--pete

[kagliostro]

If you don't like to mess with PCB

http://www.tube-town.net/ttstore/Kits/Power-Supply/TT-VPump-Voltage-Converter::6163.html

https://tube-town.net/info/datenblaetter/kits/vpump_layout_v1_5.pdf

However I think that if you have already the PT and it gives a low B+, you can use a simple Voltage Doubler





the excess in voltage can be easily dropped using resistors because preamp current consumption is low

K

[smackoj]

thanks; yes, I already have a simple isolation transformer 1:1 ratio that makes about 140 vdc after the bridge rectifier.  Pete, I don't know the current draw for sure, just a one 12a_7 setup.

 

[kagliostro]

It will be max 5mA

Assuming 110v AC probabily a doubler will give you around 300v DC


if this voltage is too high you can drop it simply using a resistor

K

EDIT: I forgot to remember you that using a doubler the available current will be 1/2 ot the disposable current, so if you have 100mA DC disposable, doubling the voltalge will halve it at 50mA

[smackoj]

I see your point about current cut in half when volts doubled. Question about your two diagrams of voltage doublers. Are these making a plus and a minus voltage?

thanks Kaglio

[kagliostro]

Are these making a plus and a minus voltage?

At the output ? ..... Yes

http://en.wikipedia.org/wiki/Voltage_doubler

K

[2deaf]

Are these making a plus and a minus voltage?

The top circuit is not a voltage doubler.  The bottom circuit is the kind of doubler that DL was talking about.

Both examples can be a +/- supply or a single-ended one, it's just a matter of where you connect ground.

[kagliostro]

The top circuit is not a voltage doubler.

At Wikipedia seems the contrary

http://en.wikipedia.org/wiki/File:Full-wave_voltage_doubler.svg

K

[2deaf]

I don't much care what Wikipedia says.  Show me how smackoj is going to double his voltage using the top circuit and his isolation transformer.

[kagliostro]

This is not from Wikipedia



Source: http://sound.westhost.com/valves/design2.html

or go here and read "Greinacher voltage doubler"

http://www.kronjaeger.com/hv/hv/src/mul/


of course I posted the two circuits because I didn't know if the transformer had or not a CT

K

[2deaf]

Cool.  These are the same two circuits, but this time there are voltages so that you can clearly see that the first one is not a doubler and the second one is.

[kagliostro]

Have you read the explanation on the second link ?


K

[PRR]

> Wikipedia seems the contrary

That's one image on Wiki. The name is *wrong*; this is not a doubler. This fact has not been checked by "everybody"; it was the uploader's choice. This image is NOT used on any Wiki article page (where it would be peer-reviewed and rejected or re-named).

> the explanation on the second link ?

Here the author has mis-written. (a) IS a voltage-doubler. But then for (b) he has put TWO windings-- double the ACV, not double the DC:AC ratio.
_________________________________________

Getting back to the original issue:

> uses an isolation transformer ... if there is an IC chip or ? that can boost/double the voltage

What the chips do is turn DC into AC which can then be stepped-up with various AC techniques. This is necessary in battery or battery-eliminator situations where only DC is available.

If you have an AC transformer and AC, you do not need the chips. They *can* lead to a smaller solution, but not in this case (you already have a transformer and do not have deep knowledge of spike-switching up-converters).

[2deaf]

thanks; yes, I already have a simple isolation transformer 1:1 ratio that makes about 140 vdc after the bridge rectifier.  Pete, I don't know the current draw for sure, just a one 12a_7 setup.

If you post a drawing of your power supply, I can show you how to very easily convert it to a doubler.  I'd be surprised if you found an isolation transformer with a VA rating low enough to make the secondary current an issue.

[kagliostro]

Thanks for the explanation PRR

As you know I've no study on the matter and the only source of info I've is the web and few other

finding more sources that say the same thing I was assuming the thing is to be true

anyway this wasn't true in this case

this is the price that you must pay when you are ignorant 

---

EDIT: Please, on the second link I read

The Greinacher doubler circuit (a) transforms a grounded AC voltage (peak voltage Up) into symmetrical DC voltages of 1x Up each, thus producing 2x Up between outputs. If the input voltage is already symmetrical (e.g. as in an Obit), the Greinacher circuit may be doubled according to (b). This does not change the output voltages but increases the possible output current by a factor of two.

Is right to say that in (b) the current is increased by a factor of two ?

If it is true this will be very interesting (or it is too nice to be real ?)

Thanks

Franco

p.s.: May be this article contents something of interesting about the use of Voltage multipliers

http://tubecad.com/2013/03/blog0258.htm

[sluckey]

Is right to say that in (b) the current is increased by a factor of two ?

Yes. A is two half wave rectifiers. B is two full wave rectifiers.

The half wave is like a one hump camel caravan. The full wave is like a two hump camel caravan.

Oh, and the transformer in B is literally twice the size of the transformer in A.   

[kagliostro]

The half wave is like a one hump camel caravan. The full wave is like a two hump camel caravan.

Are you sure ?

Isn't that you confused with a caravan of dromedaries and a caravan of camels ?

 

Franco

[sluckey]

...dromedaries...

Learned a new word today! 

[smackoj]

ok gents, here is a drawing of what my power supply looks like now. One of the elec. caps will need to be replaced because it is only rated at 160 volts.
jack d

[2deaf]

One possibility.

[kagliostro]

I was thinking to something like this



You surprised me, I've never seen a bridge used that way (there is always something new to learn)

K


p.s.: @ Steve, this is a dromedary 

[jjasilli]

You surprised me, I've never seen a bridge used that way (there is always something new to learn)


Ditto!  I've never seen a voltage doubler drawn as a bridge.  That threw me for a while.


BUT: 


Whatever happened to the original question of using a SS PS for higher B+ voltage?

[smackoj]

"whatever happened to the original question about a SS doubler"?

I think that idea got tossed because simply changing the wiring in a few places and adding a couple capacitors is easy and known to be tested and reliable. Just one man's SWAG (sort of wild *** guess).

gracias amigos. good learnable info.