Advantages of charge pump over regulator on + gnd. cicuits ?

[frank_p]

I am reading posts on how to make a positive ground power supply and I find two options.  Either use a LM7909 regulator or a LT1059 charge pump to do so.  Is there any advantages (or inconveniences) of one method vs the other one ?  I've searched on the forum why someone would choose one circuit instead of the other and found nothing (maybe not searched an off ?)...  If you were to build a positive ground power supply what alternative would you choose and why?  Are there any issues in regard of when positive grounds boxes are mixed with negative ground ones ?  Is there a noise issue ? Or heat dissipation problem ?  Are both solutions are quite equivalent ?  What are your experiences ?  Why charge pumps for positive grounds circuits have popularity these days ?  I am pretty much undecided on what to use now...

Thanks.

[zyxwyvu]

I am reading posts on how to make a positive ground power supply and I find two options.  Either use a LM7909 regulator or a LT1059 charge pump to do so. 

The charge pumps that are typically used are the ICL7660, MAX1044, or LT1054 (or equivalent chips from other manufacturers). The LT1059 (typo?) is a switched capacitor filter, which is quite different. I don't know of any way you could make a positive ground supply with a 7909 unless you already had an isolated supply. Do you have a link for that?

Is there any advantages (or inconveniences) of one method vs the other one ?  I've searched on the forum why someone would choose one circuit instead of the other and found nothing (maybe not searched an off ?)...  If you were to build a positive ground power supply what alternative would you choose and why?  Are there any issues in regard of when positive grounds boxes are mixed with negative ground ones ?  Is there a noise issue ? Or heat dissipation problem ?  Are both solutions are quite equivalent ?  What are your experiences ?  Why charge pumps for positive grounds circuits have popularity these days ?  I am pretty much undecided on what to use now...

The issue with positive ground circuits is that if you power a positive and negative ground pedal off the same supply without one of these solutions, you will short the outputs of the supply. This means you need to either use an isolated supply, a charge pump, or (though I haven't seen this used) a switching inverting regulator. An isolated supply just means that you only use the power supply for one pedal, and it is completely isolated from other power supplies (different secondary or transformer). Switching regulators are generally more complicated than either option.

My personal choice is to use a charge pump. It just takes a DIP-8 IC and two electrolytic caps to get you a usable -9V. This way, there isn't any issue with powering it along with a negative ground pedal. You can also still use the +9V (it really gives you a bipolar (+9)-0-(-9) supply). Make sure to pay attention to current requirements, though. Higher current gives you higher ripple on the -9V, and the ICL7660/MAX1044 can only do 10mA, while the LT1054 can do 100mA.

[frank_p]

The charge pumps that are typically used are the ICL7660, MAX1044, or LT1054 (or equivalent chips from other manufacturers). The LT1059 (typo?) is a switched capacitor filter, which is quite different.

Yes I confess... My error

I don't know of any way you could make a positive ground supply with a 7909 unless you already had an isolated supply. Do you have a link for that?

Ok. the issue is with daisy chaining from an already regulated power supply ?  So if you want to daisy chain a positive ground on a boss power supply, you could do so with the charge pump.  Right ?

But if you have a 24VAC center tapped wallwart, you can do as in he last picture (from GEO).

If you use a 12VAC with only one pedal connected to it, you can use the 7809 or the 7909 to make both a + or - power supply.

The issue with positive ground circuits is that if you power a positive and negative ground pedal off the same supply without one of these solutions, you will short the outputs of the supply. This means you need to either use an isolated supply, a charge pump, or (though I haven't seen this used) a switching inverting regulator. An isolated supply just means that you only use the power supply for one pedal, and it is completely isolated from other power supplies (different secondary or transformer). Switching regulators are generally more complicated than either option.

Ok.  I think I get it.  The other option is a center tapped transformer with the two regulators.

My personal choice is to use a charge pump. It just takes a DIP-8 IC and two electrolytic caps to get you a usable -9V. This way, there isn't any issue with powering it along with a negative ground pedal. You can also still use the +9V (it really gives you a bipolar (+9)-0-(-9) supply). Make sure to pay attention to current requirements, though. Higher current gives you higher ripple on the -9V, and the ICL7660/MAX1044 can only do 10mA, while the LT1054 can do 100mA.

So there is no big voltage drop with a charge pump when daisy chained on a "Boss" regulated power supply ?

Ok. a big thanks.
I think  I was confused because I toughed that the voltage drop of the charge pump was too big as to use it directly on a +9V supply.  So my view was to make the charge pump circuit around a single 12V (or 10V...) supply.

Thanks again Josh, I think it's more clear.
I should have studied better before...
The helping hand is appreciated.

H.F.P.

[zyxwyvu]

Ok. the issue is with daisy chaining from an already regulated power supply ?  So if you want to daisy chain a positive ground on a boss power supply, you could do so with the charge pump.  Right ?

But if you have a 24VAC center tapped wallwart, you can do as in he last picture (from GEO).

If you use a 12VAC with only one pedal connected to it, you can use the 7809 or the 7909 to make both a + or - power supply.

Yes to all of the above.

So there is no big voltage drop with a charge pump when daisy chained on a "Boss" regulated power supply ?

I checked the LT1054 datasheet, and at 10mA, you'll have almost a .4V drop, so you'll get -8.6V. The drop goes up to about 1V for 100mA.

[frank_p]

I see now that I was completely confused...  I was thingking some people liked charge pumps better than regulators.  I started thinking the wrong way from the beginning until I asked the question.  I was confused because Mouser and Digikey have a weird way of informing what's the maximum and minimum output voltages in their catalog.  In catalogs it's often written that the output for the LT1054 is -5V and the maximum input is 15V.     Not sure about what they mean (I am talking about the catalogs, not the datasheets).

I sould have asked the question before, thanks Josh !