Forums

charge pump/boost converter

Started by bitrex July 18, 2015
For a hobby project, I'd like to be able to generate +48 volts or so 
from +5 volt USB.  Current requirements are small, maybe 15 mA or so? 
I'd like uh, low noise (I don't have an exact spec so this is just kind 
of existential at this point), so maybe a charge pump would be in order 
rather than a boost switcher?

Does anyone make a charge pump IC that I could feed an external clock 
to, with outputs suitable for running something like a Dickson pump? 
Maybe that would be too many stages to go from +5 to +48...
On 7/18/2015 8:39 AM, bitrex wrote:
> > For a hobby project, I'd like to be able to generate +48 volts or so > from +5 volt USB. Current requirements are small, maybe 15 mA or so? > I'd like uh, low noise (I don't have an exact spec so this is just kind > of existential at this point), so maybe a charge pump would be in order > rather than a boost switcher? > > Does anyone make a charge pump IC that I could feed an external clock > to, with outputs suitable for running something like a Dickson pump? > Maybe that would be too many stages to go from +5 to +48...
My guess is that it would take 11 stages, possibly more.
On 2015-07-18 6:39 AM, bitrex wrote:
> > For a hobby project, I'd like to be able to generate +48 volts or so > from +5 volt USB. Current requirements are small, maybe 15 mA or so? > I'd like uh, low noise (I don't have an exact spec so this is just kind > of existential at this point), so maybe a charge pump would be in order > rather than a boost switcher? > > Does anyone make a charge pump IC that I could feed an external clock > to, with outputs suitable for running something like a Dickson pump? > Maybe that would be too many stages to go from +5 to +48...
Too much hassle, too many stages. I'd use one of the flyback transformers they sell for power over Ethernet (PoE) and use it in reverse. At this roughly 10:1 ratio a boost converter will also work and they are often less noisy. If you can cloc-drive it from or synchronize it to an ADC clock or something. -- Regards, Joerg http://www.analogconsultants.com/
On 07/18/2015 10:25 AM, John S wrote:
> On 7/18/2015 8:39 AM, bitrex wrote: >> >> For a hobby project, I'd like to be able to generate +48 volts or so >> from +5 volt USB. Current requirements are small, maybe 15 mA or so? >> I'd like uh, low noise (I don't have an exact spec so this is just kind >> of existential at this point), so maybe a charge pump would be in order >> rather than a boost switcher? >> >> Does anyone make a charge pump IC that I could feed an external clock >> to, with outputs suitable for running something like a Dickson pump? >> Maybe that would be too many stages to go from +5 to +48... > > My guess is that it would take 11 stages, possibly more.
You can get modules that do most of that for a buck and a half on eBay. http://tinyurl.com/q2qkn2u will do 5->24V, and then a homemade single-stage charge pump will get you 48V. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
On Sat, 18 Jul 2015 09:39:34 -0400, bitrex
<bitrex@de.lete.earthlink.net> wrote:

> >For a hobby project, I'd like to be able to generate +48 volts or so >from +5 volt USB. Current requirements are small, maybe 15 mA or so? >I'd like uh, low noise (I don't have an exact spec so this is just kind >of existential at this point), so maybe a charge pump would be in order >rather than a boost switcher? > >Does anyone make a charge pump IC that I could feed an external clock >to, with outputs suitable for running something like a Dickson pump? >Maybe that would be too many stages to go from +5 to +48...
Two of these http://www.digikey.com/product-detail/en/PDS1-S5-S24-M-TR/102-2973-2-ND/4006941 with the outputs in series would work. They are fairly quiet, and you could add a little filtering to help. At light loads, their output tends to be a few per cent high. But then, 5 volts from USB may not really be 5 volts. For really quiet, consider some sort of sinewave drive step-up transformer. A diode-based charge pump would make less than 4 volts per stage, so that would take a lot of parts. -- John Larkin Highland Technology, Inc picosecond timing laser drivers and controllers jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
On 7/18/2015 8:39 AM, bitrex wrote:
> > For a hobby project, I'd like to be able to generate +48 volts or so > from +5 volt USB. Current requirements are small, maybe 15 mA or so? > I'd like uh, low noise (I don't have an exact spec so this is just kind > of existential at this point), so maybe a charge pump would be in order > rather than a boost switcher? > > Does anyone make a charge pump IC that I could feed an external clock > to, with outputs suitable for running something like a Dickson pump? > Maybe that would be too many stages to go from +5 to +48...
Interesting! Anyone know how quiet is the power coming out of a USB port (vs load)?
On 7/18/2015 12:38 PM, John S wrote:
> On 7/18/2015 8:39 AM, bitrex wrote: >> >> For a hobby project, I'd like to be able to generate +48 volts or so >> from +5 volt USB. Current requirements are small, maybe 15 mA or so? >> I'd like uh, low noise (I don't have an exact spec so this is just kind >> of existential at this point), so maybe a charge pump would be in order >> rather than a boost switcher? >> >> Does anyone make a charge pump IC that I could feed an external clock >> to, with outputs suitable for running something like a Dickson pump? >> Maybe that would be too many stages to go from +5 to +48... > > > Interesting! Anyone know how quiet is the power coming out of a USB port > (vs load)?
I don't think there is any spec on that other than the voltage tolerance of 4.75 to 5.25 volts. -- Rick
On Sat, 18 Jul 2015 09:39:34 -0400, bitrex wrote:

> For a hobby project, I'd like to be able to generate +48 volts or so > from +5 volt USB. Current requirements are small, maybe 15 mA or so? > I'd like uh, low noise (I don't have an exact spec so this is just kind > of existential at this point), so maybe a charge pump would be in order > rather than a boost switcher? > > Does anyone make a charge pump IC that I could feed an external clock > to, with outputs suitable for running something like a Dickson pump? > Maybe that would be too many stages to go from +5 to +48...
Boost or flyback, and if noise is an issue then make 50V and follow it with a linear regulator. -- www.wescottdesign.com
On Saturday, July 18, 2015 at 5:50:11 PM UTC+2, John Larkin wrote:
> On Sat, 18 Jul 2015 09:39:34 -0400, bitrex > <bitrex@de.lete.earthlink.net> wrote: > > > > >For a hobby project, I'd like to be able to generate +48 volts or so > >from +5 volt USB. Current requirements are small, maybe 15 mA or so? > >I'd like uh, low noise (I don't have an exact spec so this is just kind > >of existential at this point), so maybe a charge pump would be in order > >rather than a boost switcher? > > > >Does anyone make a charge pump IC that I could feed an external clock > >to, with outputs suitable for running something like a Dickson pump? > >Maybe that would be too many stages to go from +5 to +48... > > Two of these > > http://www.digikey.com/product-detail/en/PDS1-S5-S24-M-TR/102-2973-2-ND/4006941 > > with the outputs in series would work. They are fairly quiet, and you > could add a little filtering to help. At light loads, their output > tends to be a few per cent high. But then, 5 volts from USB may not > really be 5 volts. > > For really quiet, consider some sort of sinewave drive step-up > transformer.
A Baxandall Class-D oscillator - one step-up transformer and one inductor - would work well. MOS-FET transistors do a bit better than bipolar transistors, but Baxandall's paper rather pre-dates them. http://sophia-elektronica.com/0344_001_Baxandal.pdf http://sophia-elektronica.com/Baxandall_parallel-resonant_Class-D_oscillator1.htm -- Bill Sloman, Sydney
On 7/18/2015 10:51 AM, Phil Hobbs wrote:
> On 07/18/2015 10:25 AM, John S wrote: >> On 7/18/2015 8:39 AM, bitrex wrote: >>> >>> For a hobby project, I'd like to be able to generate +48 volts or so >>> from +5 volt USB. Current requirements are small, maybe 15 mA or so? >>> I'd like uh, low noise (I don't have an exact spec so this is just kind >>> of existential at this point), so maybe a charge pump would be in order >>> rather than a boost switcher? >>> >>> Does anyone make a charge pump IC that I could feed an external clock >>> to, with outputs suitable for running something like a Dickson pump? >>> Maybe that would be too many stages to go from +5 to +48... >> >> My guess is that it would take 11 stages, possibly more. > > You can get modules that do most of that for a buck and a half on eBay. > http://tinyurl.com/q2qkn2u will do 5->24V, and then a homemade > single-stage charge pump will get you 48V. > > Cheers > > Phil Hobbs >
Oh wow, those are great. They're cheap enough that I could just slap them into a "finished" product...