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LM2956 Buck converter help

Started by mkr5000 February 23, 2019
Pardon my not knowing but I still live in an LM317 world.

On a buck converter like this --

https://www.ebay.com/itm/1-PCS-LM2596-DC-Adjustable-Buck-Converter-Step-Down-Power-Supply-Module-1-23-30V/322365871574?hash=item4b0e80d5d6:g:a-8AAOSwZQRYWiq3:rk:2:pf:1&frcectupt=true

It has an adjustable multi turn pot for the output (which is a plus) and I want to set it to a steady 5v.

The goal is to give it 12 volts input but wondering if a slight fluctuation in input voltage affects the output on these. As in all 12 volt wall warts not being created equal.  -- thanks much

mkr5000 wrote:
> > > Pardon my not knowing but I still live in an LM317 world. > > On a buck converter like this -- > > https://www.ebay.com/itm/1-PCS-LM2596-DC-Adjustable-Buck-Converter-Step-Down-Power-Supply-Module-1-23-30V/322365871574?hash=item4b0e80d5d6:g:a-8AAOSwZQRYWiq3:rk:2:pf:1&frcectupt=true
> > It has an adjustable multi turn pot for the output (which is a plus) > and I want to set it to a steady 5v. > > The goal is to give it 12 volts input but wondering if a slight > fluctuation in input voltage affects the output on these. As in all > 12 volt wall warts not being created equal. > >
** The LM2596 buck converter has good output voltage stability under varying input and load conditions. Not quite as good as a linear reg like the LM317, but within 1% or so. The module you have linked will have some AC ripple on the DC output at 150kHz, maybe a few per cent. What worries me is the use of an 220uF SMD electro as the output filter cap, typically these caps have poor ESR figures and low ripple current ratings. .... Phil
On Saturday, February 23, 2019 at 6:30:07 PM UTC-5, Phil Allison wrote:
> mkr5000 wrote: > > > > > > Pardon my not knowing but I still live in an LM317 world. > > > > On a buck converter like this -- > > > > https://www.ebay.com/itm/1-PCS-LM2596-DC-Adjustable-Buck-Converter-Step-Down-Power-Supply-Module-1-23-30V/322365871574?hash=item4b0e80d5d6:g:a-8AAOSwZQRYWiq3:rk:2:pf:1&frcectupt=true > > > > > It has an adjustable multi turn pot for the output (which is a plus) > > and I want to set it to a steady 5v. > > > > The goal is to give it 12 volts input but wondering if a slight > > fluctuation in input voltage affects the output on these. As in all > > 12 volt wall warts not being created equal. > > > > > > ** The LM2596 buck converter has good output voltage stability under varying input and load conditions. Not quite as good as a linear reg like the LM317, but within 1% or so. > > The module you have linked will have some AC ripple on the DC output at 150kHz, maybe a few per cent. > > What worries me is the use of an 220uF SMD electro as the output filter cap, typically these caps have poor ESR figures and low ripple current ratings. > > > > .... Phil
Thanks a lot Phil. What would you replace that cap with? Just a nice robust axial type? Teach me.
mkr5000 wrote:

> > > > Thanks a lot Phil. What would you replace that cap with? >
** Need to know the load current first.
> Just a nice robust axial type? Teach me.
** Maybe, see above. .... Phil
Phil Allison wrote...
> mkr5000 wrote: >> >> On a buck converter like this -- >> >>https://www.ebay.com/itm/1-PCS-LM2596-DC-Adjustable-Buck-Converter-Step-Down-Power-Supply-Module-1-23-30V/322365871574
> ** The LM2596 buck converter has good output voltage stability under varying > input and load conditions. Not quite as good as a linear reg like the LM317, > but within 1% or so. > > The module you have linked will have some AC ripple on the DC output at > 150kHz, maybe a few per cent. > > What worries me is the use of an 220uF SMD electro as the output filter cap, > Typically these caps have poor ESR figures and low ripple current ratings.
The performance could be about the same as a through-hole of the same size. But who knows! If that's an issue: https://www.ebay.com/itm/LM2596S-DC-DC-3A-Buck-Adjustable-Step-down-Power-Supply-Converter-Module-Arduino/382552225398 -- Thanks, - Win
> > > > What worries me is the use of an 220uF SMD electro as the output filter cap, > > Typically these caps have poor ESR figures and low ripple current ratings. >
they make ceramic caps in this range these days m