18v from 9v in a tiny circuit?

[markr04]

Hi all. EMG says, "If you have room for more than one battery, you can go up to 27v (although we recommend no more than 18v). This will give you more headroom... blah-blah..."

I don't have the room for a second battery, but might fit a PCB in there. Does a small (dimension-wise) charge-pump circuit exist?

Thanks!

[Bernardduur]

Yes, but it will drain your 9V battery faster

[KORGULL]

Have you seen this yet?...www.diystompboxes.com/pedals/vdbl.html
...might be what you're looking for.

[nelson]

There is also the charge pump at GGG, uses a MAX1044. connecting pin 1 of the MAX1044 to +9v gets rid of the "whine" in the audio signal, there is also no need for the pnp transistor.

[markr04]

Wonderful! Looks like I have the room for either of those. Thanks a bunch guys!

[amz-fx]

there is also no need for the pnp transistor.

The pnp transistor is for reverse power supply protection.  You can read more about the technique at:

http://www.maxim-ic.com/appnotes.cfm/appnote_number/636

regards, Jack

[R.G.]

Actually no, Jack, it's not.

It's there to keep the pulsed current off the signal ground wire so you can use the stereo jack trick to switch power. Polarity protection is nice, but that's not why it's there.

Neat article though. I wish I'd seen that years ago instead of now.

[markr04]

R.G.,

Since I want to use my guitar output jack as the switch, should I use the circuit Korgull pointed to?

[soundcollage]

Put a stereo jack into your guitar and build a box on your pedalboard to phantom power it. I imagine if you are at this forum you have a few other pedals. As the circuity for the charge pump wont take up that much room you could most likely encorporate it into another pedal, be it whatever is first in your chain or possibly a newly built loop selector pedal etc... As 9v's are about 4-5$ a pop( for a quality one) and an integrated charge pump would double your consumption of batteries --the investment in  a stereo cable, jack, and a hammond box etc. would be offset in battery savings rather quickly. Then you don't have to worry about accidentally leaving your guitar plugged in (or double checking if the drummer was f'ing around after practice with your guitar again) and only getting 20 min of playing time out of that    5$ battery (he says from frustrating exp.).

[aron]

Cool Jack! That's a great article!

ARCHIVE

[amz-fx]

A couple of quick notes on the MAX1044...   it is a cmos chip and not very sturdy.  Be careful about static while handling and soldering. Reverse power supply protection would be recommended, especially if you have an external power jack in addition to the battery.

Also, the MAX1044 has an absolute max supply limit of 10.5 volts.    If you are using an unregulated external 9v power adapter, be aware that it will put out higher than 9v unless loaded close to its max current...  I have measured them at 12v and higher when powering just a single effects circuit...  plug one of these into your voltage doubler and *phzzzztttt* it is dead!   

regards, Jack

[moosapotamus]

I'm assuming the MAX1044 does not supply very much current. But, I can't seem to suss any actual numbers out of the datasheet. How much current is the MAX1044 capable of supplying? What if you feed it regulated 9V @ 1A?

~ Charlie

[R.G.]

But, I can't seem to suss any actual numbers out of the datasheet. How much current is the MAX1044 capable of supplying?

It's there in the datasheet - 30 to 100 ohms, depending on the frequency you drive it at and the bucket capacitors.

[amz-fx]

I'm assuming the MAX1044 does not supply very much current. But, I can't seem to suss any actual numbers out of the datasheet. How much current is the MAX1044 capable of supplying? What if you feed it regulated 9V @ 1A?

Yes, it is best when supplying low current requirements...  10ma or less would be good but it can go to 20ma with about a 10% loss in output.  Ripple increases as current draw increases too.

regards, Jack

[zeta55]

Not shure about this one, but, I'm currently using it in my version of that  cuircit and it works great. Both for the +18VDC and the -7VDChttp://ampage.org/cgi-bin/hammer/index.cgi?cmd=lt&xid=&fid=&ex=&pg=4 check out the "Super Octaver" DC/DC uppverter.  I have no idea wether the current it can deliver.

In time I hope to post my new layout and schematic of that cuircit, when I get it working just right......

[R.G.]

Playing the devil's advocate again, it's pretty easy to get 18 or 27... or 30 or more... volts from a 9V battery. There are numerous step-up switching supply controllers that will do just that. They put everything except the inductor and filter cap and a couple of resistors in an 8 pin DIP. It's a modest design effort, not trivial but not brain taxing either. The output is regulated, and the efficiency is upwards of 90%.

[Paul Perry (Frostwave)]

They put everything except the inductor

Ah yes...... everything but the inductor 
1. don't think you can use just any old inductor there! (as you would know) and
2. don't think you can buy one anyway (at least for what the chip cost!)
Still, I agree this is the way to go, virtually every electronic appliance is like this now.
And, it's a hell of a lot cheaper using a D cell & a switchmode boost instead of a 9v battery!!

[R.G.]

The nice thing is that for small power converters like this, which run at quite high frequencies, the inductor gets tiny and available. I believe - although I have not actually looked yet - that Digikey has suitable inductors.

I guess I'll have to design one of these and put it up on GEO.