Cascading Charge Punps

[Big Monk]

I'm looking to try and get 36 vDC using a 9 vDC input with the goal being to step down that voltage to 24 vDC and 15 vDC respectively with regulators.

Is this feasible or should I investigate another way of using the 18 vDC output of a si gel charge pump circuit to get to 24 vDC?

[Rob Strand]

The main headache cascading charge pumps is finding charge pump which will handle the voltage of the following stages.   If you do a DIY charge pump it's likely to be inefficient.

Another angle is to use a multiple stage C-ockcroft-Walton multiplier or a Dickson multiplier (funny correlation between names and multiplying).  No doubt you will find some examples of charge-pump ICs combined with these ideas, for example,

https://www.henteko.org/fswiki/wiki.cgi?page=%A5%C1%A5%E3%A1%BC%A5%B8%A5%DD%A5%F3%A5%D7%CA%FD%BC%B0DC-DC%A5%B3%A5%F3%A5%D0%A1%BC%A5%BF%A1%BC%A1%CA3V%A2%AA9V%A1%CB%A4%CE%BC%C2%B8%B3

They tend to work better at low currents both from an efficiency and regulation point of view.  The efficiency can suffer on these to some degree due to the diode drops but also due to higher switch drops at the charge-pump.   Think about 10mA at the output at 36V that's 360mW, which is means 40mA at 9V in even with 100% efficiency (it will be a lot worse than that).

Paul Marossy had a thread going about a year ago using CMOS gates for a Dickson multiplier.  He wasn't happy with the performance with the loads he was using.  CMOS gates are only good for very low currents because the switch resistances are quite high, much higher than charge-pump ICs.

For significant current you have to start thinking of switch-mode power supplies.  Boost converters and the like.

[PRR]

I would start asking if you really NEED 24V. A 9V supply can slap any guitar amp silly.

[Big Monk]

I'll probably just stick with feeding a single charge pump 12 vDC to get around 24 vDC out.

[Big Monk]

I would start asking if you really NEED 24V. A 9V supply can slap any guitar amp silly.

It's for a UniVibe circuit.

[antonis]

18VDC should be more than fine..
(even 16VDC should be acceptable..)

Bear in mind original pedal's 24VAC are half-wave rectified..

[Big Monk]

18VDC should be more than fine..
(even 16VDC should be acceptable..)

Bear in mind original pedal's 24VAC are half-wave rectified..

I've been running my PedalPCB ElectroVibe at 24 vDC via a 12 vDC tap of my Truetone CS-7 and the internal charge pump. It has noticeably more depth at slower speeds over the 18 vDC via the 9 vDC tap.

My goal will probably be just to run a separate adapter for 24 vDC and forego the charge pump in my design for my new Vibe unit. I'll use a 15 vDC regulator downstream for the audio portions. Depending on the rated mA of the adapter, i should be able to get a touch more voltage than 24 vDC that way.

[antonis]

Proceed as you like but ask also your electros for their voltage rating..

[Big Monk]

Proceed as you like but ask also your electros for their voltage rating..

Oh for sure. I have 50 vDC rated units lined up for this project.

[Vivek]

There are many low cost DC to DC boost convertors, boost invertors on Alibaba and ebay, at 4 to 10 USD a pop.

Some can do few amps, are short circuit protected, user selectable output voltage, high conversion efficiency

Example
https://www.alibaba.com/product-detail/1200W-20A-DC-DC-Step-up_62155485615.html

https://www.alibaba.com/product-detail/Okystar-XL6019-DC-DC-Step-Up_1600217060983.html

[Big Monk]

There are many low cost DC to DC boost convertors, boost invertors on Alibaba and ebay, at 4 to 10 USD a pop.

Some can do few amps, are short circuit protected, user selectable output voltage, high conversion efficiency

Example
https://www.alibaba.com/product-detail/1200W-20A-DC-DC-Step-up_62155485615.html

https://www.alibaba.com/product-detail/Okystar-XL6019-DC-DC-Step-Up_1600217060983.html

Those are physically too large for the 125B enclosure but i'll check them out for other projects. Thanks!

[Ripthorn]

You can use a single charge pump IC with subsequent diode/cap stages to continue to boost the output voltage. You lose a little efficiency with each extra stage, but I have successfully gotten ~70V with it. It takes two diodes and two 10 uF caps per stage and each stage adds a little less than the input voltage. Also note that as voltage goes up, current capacity goes down.

[Keppy]

^This. I have an LT1054-based power supply on my bench right now getting +30/-10v from a 9v supply. The current supplied will be low, but these things are flexible. You can even use a trimpot to dial in 24v straight from the charge pump, then you only need a regulator/divider for the 15v.

[Big Monk]

^This. I have an LT1054-based power supply on my bench right now getting +30/-10v from a 9v supply. The current supplied will be low, but these things are flexible. You can even use a trimpot to dial in 24v straight from the charge pump, then you only need a regulator/divider for the 15v.

I was going to take a look tonight at the power supply for my Aion Ares (Clinch FX EP Pre). I know I get close 22 vDC from 9 vDC in that power supply:



Also, the PedalPCB Clandestine (Chase Tone Secret Pre) does something similar:



Thanks for jogging my memory Gents!

[Kevin Mitchell]

Another charge pump thread, huh?

18 volts is fine for the Univibe. The signal path typically runs at that voltage and the lamp (in the neo vibe at least) takes 15 volts from a regulator.
I've powered a few with 9V into an LT1054. Bigger filter caps may be needed.

My layout can be found through the link in my signature.

[Big Monk]

18 volts is fine for the Univibe.

True. Nothing wrong with it at all but running my PedalPCB ElectroVibe at 24 vDC gives more intensity at slow speeds so I am going to try 24-28 vDC on a new project and see how it sounds.

My layout can be found through the link in my signature.

Thank you!

[Big Monk]

So I verified the power supplies from the 2 Echoplex Preamps above and put out around 26 vDC without the Zener with a 9 vDC input.

Looks like I can adapt either into my Vibe project.

Thanks for all the pointers everyone!

[Rob Strand]

So I verified the power supplies from the 2 Echoplex Preamps above and put out around 26 vDC

You will find it drops quite quickly under load.   For light loads diode drops start to kick in then after that increasing the load current causes increasing drops across the charge-pumps internal switches and the output voltage starts to drop.

[antonis]

You will find it drops quite quickly under load.

^ That..!! ^

Charge pumps are very sensitive when they have to handle current and ripple simultaneously..

[Clint Eastwood]

This simple circuit will provide 25 volts, but don't ask for more than a few mA. You can also tap 17 volts between D2 and D3. The schematic says ne555 timer,  but you should use a CMOS version like tlc555. Efficiency is then quite good, about 85%.




You could draw about 10 mA, but then use 10uf capacitors for C2,C3,C4 and C7.