charge pumpage and eh micro synths

[pinkjimiphoton]

hi guys,

i was given a pair of microsynths yesterday from my late brother jeff's wife..

they need 24v c=+ warts @ 100ma.

and i was thinking... (even tho i just ordered a pair)


"self, why not use a cp to get the voltage up there?"

so i was thinking... is there any way to get a voltage doubler charge pump chip to put out maybe 30vdc, and then regulate it down to 24??

sorry if a dumb question, but i'm a newb that tends to run into the middle of the freeway sometimes...

[Govmnt_Lacky]

PM'd 

[Mark Hammer]

There are a bunch of EHX pedals with the 24VAC/100ma sticker on the side and the mini phone-jack for the adaptor.

Internally, they will generally be regulated to +/-15v or something else that a single 2-conductor DC adaptor won't do.  I guess the question is whether the sticker's 100ma requirement/spec is something that has a lot of leeway, or needs to be obeyed.  If it needs to be obeyed, because the circuit itself needs the current, then a charge pump is unlikely to do the trick.

That said, depending on the pedal you are mulling over, there may be a whole bunch of different adaptors that can do the job besides 24VAC.

For example, if one looks at the reissue Memory Man and Polychorus, both of those take the 24ac input and regulate it to 15VDC.  The regulator they use needs to see at least 2VDC more at its input than it provides at its output.  In theory, a 12.6VAC transformer could provide juuuuussst enough ripply DC (once half-wave rectified) for the regulator to work.

The reissue Microsynth has a more complex regulation and supply-voltage derivation internally than those two pedals, but again, there is nothing I can see in the schematic that suggest a 15VAC (or greater) source would NOT be sufficient for powering the unit.  The nice thing is that since the regulation is done on board, ANY old voltage/current-appropriate adaptor/source will do.

[amptramp]

A charge pump of the 7660 type is suitable for a few milliamps.  More than that and the inefficiencies become dominant.  This type of charge pump operates by charging capacitors in parallel then stacking them in series.  The charging is done through switches that impose resistive losses.  Compare that with a power supply using inductance.  The losses can be made much less because switching can be completed before the inductor permits the current to rise.  The flyback, buck or boost regulator or push-pull design (of which there are many) can be made over 90% efficient with the correct design.

Changing an internal supply from bridge to voltage doubler may accomplish what you want with relatively cheap components and might possibly still fit in the pedal.  A 12 VAC wall wart could then provide all the necessary power, but it would have to be rated at 200 mA to power a doubler that delivers 100 mA.  An AC bridge supply can be run from DC but a doubler cannot.  The DC supply will not be connected to ground because the bridge will maintain it a diode drop away.

[pinkjimiphoton]

cool, thanks for the input guys.

i haven't opened either of them yet, but i did order the proper power supplies today from gc...hopefully that'll be it, so i don't have to try and fix 'em.