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Using Arduino => General Electronics => Topic started by: Unknownsymbols on Dec 23, 2015, 10:37 pm

Title: What is a part called, that rectifies powerful PWM (10 A)?
Post by: Unknownsymbols on Dec 23, 2015, 10:37 pm
Excuse me, people who knowledge the electronics and hardware, can you say a model of such device:
A thing which would allow to pass current from an electricity input (actually it's a computer 12 V unit, it allows anything 0-40A), and would be PWM-(Arduino-)controllable and let pass through itself 10 A. The current needs to be direct (and not waste as much heat as linear FET mode - a "switching" unit, that is). I know a FET in switching mode can be used to produce PWM-modulated voltage, and can be as powerful as 10 A, but the FET makes the voltage also PWM-shaped. I need direct voltage, but through a PWM-controllable device.

Do they exist? I watched about buck converters, rectifiers, operational amplifiers, PWM buck converters, voltage regulators, can't find such a class of devices. Switching power suppliers have a PWM, but that's inside them, to rectify voltage. I don't know how to attach it to the external PWM. In other regulators, there are voltage selecting resistors. But only resistors.
I also know that a "LRC circuit" could rectify a powerful PWM-electricity (FET-generated), but i can't assemble such a thing. I need a module.

For example, the nearest module i got to is: www.robotshop.com/en/10a-dc-motor-driver-arduino-shield.html (http://www.robotshop.com/en/10a-dc-motor-driver-arduino-shield.html)
But i don't know yet about it. Does it produce straight voltage to motors?

To generalize a little, i need either voltage changing, or current changing, that's to control a thermoelectric plate. But still it has to be changable by 5 V PWM).
Title: Re: What is a part called, that rectifies powerful PWM (10 A)?
Post by: Paul__B on Dec 23, 2015, 10:47 pm
You don't "rectify" PWM (the term you are looking for is to "smooth" it) - you just use it to control your heater.

That's the whole idea - the heater doesn't care - being fed with full power for half the time is exactly the same as being fed with half power (which would incidentally, correspond to 1/√2 times the voltage).
Title: Re: What is a part called, that rectifies powerful PWM (10 A)?
Post by: DVDdoug on Dec 23, 2015, 10:53 pm
I'm not sure if you can buy a module like that.   What you're looking for is a "PWM controlled switching voltage regulator".

As Paul says, you don't need a linear voltage for a heater.   You don't need PWM either.   You turn a heater on 'till it hits the target temperature, then you turn it off.  Then on again when i falls below the target.
Title: Re: What is a part called, that rectifies powerful PWM (10 A)?
Post by: dwightthinker on Dec 23, 2015, 10:56 pm
Why do you require a smooth DC current. If you're
just using it to heat a heat plate, a FET power switch
would be fine.
If it is a noise problem issue, you'd need a heavy inductor
in series. The size and current handling would depend on the
parameters you are using. It would average the PWM voltage
for you.
Dwight
Title: Re: What is a part called, that rectifies powerful PWM (10 A)?
Post by: DrAzzy on Dec 23, 2015, 11:35 pm
If you need 10A at a variable voltage, your best hope is probably a digital potentiometer replacing the voltage setting resistors in a buck or boost converter. What voltage do you need? If you need more than 5v, your options for suitable digipots is limited.

I did something like this a while ago, using a digipot to control the output voltage of a buck/boost converter. I don't know if I have the notes anywhere. It wasn't terribly sophisticated.
Title: Re: What is a part called, that rectifies powerful PWM (10 A)?
Post by: MorganS on Dec 23, 2015, 11:55 pm
I think a MOSFET is the correct device for this. A Peltier will work just fine with a PWM waveform. It won't work well with a simple on-off thermostat. That causes thermal stresses in the Peltier.
Title: r: What is a part called, that rectifies powerful PWM (10 A)?
Post by: Unknownsymbols on Dec 24, 2015, 02:11 am
It's not a heater, yes, it's a Peltier-unit (thermoelectric cooler). I know that it can be controlled through just PWM. And i do have such an assembly now - a MOSFET controlled by PWM. But i've read that TEC-s don't like PWM very much - not only slow cycling, but also PWM. That they operate with better efficiency on direct current (and wear out slowlier).
I need to maximize the efficiency. The assembly i have approaches limits otherwise. Hm, it's strange that such a module isn't widely known.
I need either 10 A at a variable voltage, or 12 V at variable current.

Making a digitally controlled resistor - maybe i'll manage to do it. Will look in it. (So the reaction of regulators will be acceptable, they don't expect that resistance to be set only once, at least i know now.) It needs to be 0 to 12 V. But i don't need many steps. 6 or 8 steps would be enough.

Slow cycling (without PWM - turn on, turn off for seconds) - hm, if in some opinions it causes bad effects to the cooler, better not to do it. It seemed bad to me. Maybe because i will have big temperature on the expel side - once off, the temperature will crawl back very quickly, hardly this will be efficient.

PWM controlled switching voltage regulator
will search yet, quickly it now returns the same regulators with PWM inside.

And that motor driver - doesn't it produce smoothened current? (guess no because it doesn't have big coils, and they usually have)
Title: Re: What is a part called, that rectifies powerful PWM (10 A)?
Post by: MarkT on Dec 24, 2015, 03:25 am
Peltiers are more efficient with constant voltage/current drive than PWM: http://www.meerstetter.ch/compendium/pwm-vs-direct-current (http://www.meerstetter.ch/compendium/pwm-vs-direct-current)

The device the OP was flailing for is a _controllable_ DC-DC converter (which could be an LC filter
after a PWM power stage, like class-D amp)
Title: Re: What is a part called, that rectifies powerful PWM (10 A)?
Post by: Paul__B on Dec 24, 2015, 03:35 am
You are of course correct that TECs do not like shock stress, so that "simmerstat (https://en.wikipedia.org/wiki/Energy_regulator)" switching is indeed undesirable and PWM is much better.  The frequency (several hundred Hertz) is such that thermal shock is not a concern.

So what is the problem with PWM?

Well, Peltier devices are essentially semiconductors like LEDs - they have a threshold voltage and are essentially current driven as they tend to maintain that threshold voltage.  In effect, they behave as a voltage "sink" which performs their "work" in series with an internal resistance which is simply a power wastage and of course, interferes with their cooling effect (but of course, benefits somewhat, their heating effect).  This means that feeding more voltage disproportionately increases this energy loss, so driving more current for less of the time, is indeed, less efficient.

What you are looking for is a constant-current driver.  A simple inductor in series with your PWM driving FET, and a flyback diode across the combination, will suffice.  It is not a module as such unless you obtain a complete constant-current driver at your required specification.  Someone else may care to suggest appropriate parts for the inductor and diode. :smiley-lol:

Peltiers are more efficient with constant voltage/current drive than PWM: http://www.meerstetter.ch/compendium/pwm-vs-direct-current (http://www.meerstetter.ch/compendium/pwm-vs-direct-current)

The device the OP was flailing for is a _controllable_ DC-DC converter (which could be an LC filter
after a PWM power stage, like class-D amp)
Oh, so I needn't have bothered writing all this! :smiley-eek:
Title: Re: What is a part called, that rectifies powerful PWM (10 A)?
Post by: dwightthinker on Dec 24, 2015, 07:25 pm
I'd thought he was using it to heat.
He is right that they work more efficiently cooling with a constant
current.
It is because If you turn the voltage off, The difference in temperature
makes the peltier a generator, and a leaky one at that, as some of the
current it generates flows through the device, making it warmer.
It is something like paralleling solar panels without blocking diodes
and having one panel in the dark. The one in the light will waste
power in the one in the dark.
He is, most likely, more worried about ultimate temperature delta
than power source efficiency.
You can add a large inductor in series with your PWM power source to
smooth it out. You might try some secondary winding on some scrap
HiFi equipment.
The primaries may have too much resistance and inductance but
at about 500Hz something like a 24V winding might do a good job
of averaging a PWM signal into a smooth DC. A small amount of ripple
shouldn't be too much of an issue. Anyway, give it a try and see
if it is close.
If your going to make hundreds of these, you can calculate the inductance
and a reasonable IR drop for optimal performance.
The other option is to go with a D/A and a linear power source ( possible
modified old power supply ).
Dwight
Title: Re: What is a part called, that rectifies powerful PWM (10 A)?
Post by: Paul__B on Dec 24, 2015, 10:07 pm
Do remember that a (power) transformer will not work as a DC choke!
Title: Re: What is a part called, that rectifies powerful PWM (10 A)?
Post by: dwightthinker on Dec 25, 2015, 12:40 am
Do remember that a (power) transformer will not work as a DC choke!

WHy?
Dwight
Title: Re: What is a part called, that rectifies powerful PWM (10 A)?
Post by: MorganS on Dec 25, 2015, 01:20 am
I think because if you leave the other winding on the transformer it will act more like a transformer than an inductor.

Losses will be higher because the transformer core won't be efficient at the higher PWM frequency. It is also possible to reach saturation with a high DC current through the transformer. Then the core has no additional benefit.
Title: Re: What is a part called, that rectifies powerful PWM (10 A)?
Post by: Paul__B on Dec 25, 2015, 07:31 am
Just saturation.

DC chokes require an air gap.

(No, the other winding is irrelevant.  If both windings are similar, they can be put in series.)
Title: R: What is a part called, that rectifies powerful PWM (10 A)?
Post by: Unknownsymbols on Dec 26, 2015, 03:53 am
Quote
so I needn't have bothered writing all this
No, it's good to read, because what i've now found from "controllable dc-dc converter"s, like IR3475M or Semtech SC190, is when the chip has some easier scheme than external resistors for voltage setting, they all still require a ton of components as drawn in typical applications. Coils, capacitances, resistances. It's weird why they don't make circuits with all introduced. I think i won't be able to gear such a chip up. Or like in the solution like from this article: arduino-digitally-controlled-step-down-buck-dc-converter on eevbldg (http://www.eevblog.com/forum/beginners/%28how-to%29-arduino-digitally-controlled-step-down-buck-dc-converter/) it's the same too.
That way the digital resistor way also becomes too complicated.

And special Peltier-controllers (i think i also searched for them before, but this page is the most clear), these are too expensive. Like 235 E. So maybe i'll unevitably have to wire up the inductor and a diode. If it's just as much, maybe i won't mess it down. But i'll have to calculate them.


Also i can't fully get this idea: you both, dwightthinker and Paul_B, write that constant current is better. Is it just "than PWM", or "among the constant current and constant voltage" still constant current is better? I know that an inductor will do the constant current way, but if i ever can implement any of'em fully, just what to choose.


Quote
The other option is to go with a D/A and a linear power source ( possible modified old power supply )
Is it possible to use a DAC here? (i don't understand why linear source though) From the parameter searcher i got the feeling they are small power devices.
Title: Re: What is a part called, that rectifies powerful PWM (10 A)?
Post by: dwightthinker on Jan 04, 2016, 08:41 pm
Sorry about misleading you with the AC coil.
I should have known better, having designed switchers in the past.
Still, most of these down switchers shown could be used for
what you have in mind without using a digital resistor.
You can take the PWM output and clean it up through a RC filter
to control the switching regulator control pin.
It can be treated just like a linear regulator.
If you don't mind a big heat sink, a linear regulation setup
would also work fine.
Dwight
Title: Re: What is a part called, that rectifies powerful PWM (10 A)?
Post by: Unknownsymbols on Jan 05, 2016, 01:40 am
Well, you mean the regulator itself will be dissipating much heat, and will need the big heatsink - not the RC-circuit? And the power dissipated will be on orders of the same 100 W? If that, it's not doing to suit. Such a size (10 cm3) for just regulator is too big. And of course the system mustn't lose all power that's not powering it.
And you see, applying the digital resistor is not the hardest - all the harnessing is the hardest. So linear entry to that point i guess isn't simplifying it.

I'm now wondering what must the inductor be, if it's just a flyback. The parameters must be like: diode: >= 10 amperes, and inductor >= 10 amperes, right? But how much henries? Perhaps what formula is used.
I get the notion, eeeeh, like it was about RC here (https://www.youtube.com/watch?v=YaRDbw38x7Q&index=4&list=PLo988HxyJgRGNLqzrah043oo6BJfm_QTY) at 25 minutes; the more L, the more time it'll be settling the curve (at any change of PWM), but the less L, the less the compensation will be. And i mustn't go over some critical scale. But around what. (I can't pretty much try variants, because big inductors are hard to find.)
Title: Re: What is a part called, that rectifies powerful PWM (10 A)?
Post by: dwightthinker on Jan 05, 2016, 02:08 am
I didn't say the linear would be practical for your application.
For the switcher the size of the inductor depends on the frequency
of the switcher and the ripple you are willing to tolerate on the output.
Even though, you don't want a full turn-on/turn-off, I would suspect
for your application a 2% or 3% ripple is well within the range you
can tolerate.
You don't want to run the switcher at the PWM frequency of the
adruino. That would require a really large inductor. You just want
to make a relatively smooth DC to control the switching regulators
input control. Let the switcher go to a higher frequency.
Dwight

Title: Re: What is a part called, that rectifies powerful PWM (10 A)?
Post by: Unknownsymbols on Jan 05, 2016, 12:54 pm
I think i don't intend to control a switcher regulator - but a transistor, and for that need the inductor. If i need to raise the frequency, maybe i could use the driver of the Mosfet. But sure it isn't critical. I could even do without the smoothener, so i guess even 10% ripple will be not so bad, ?

The size of the inductor should be ultimately fittable in the 5'25 computer bay together with the Arduino and all other small parts with it. Also i read there can be several (smaller) coils combined.

So i found this formula - is it it? ind. for bucker (http://electronics.stackexchange.com/questions/49280/how-to-choose-a-inductor-for-a-buck-regulator-circuit/50597#50597)
L = (V0 × dt) / (dI × F) = (V0 × 10) / (I0 × F) for 1/10 ripple dI/dt = I0/10, if i need that oscillation on the current to be 1 10th of the main amplitude. It means L ≈ 12 / 62500 (the max. freq. of Ard.) ≈ 0,0002 H? And for 2% it would be 0,001 henry. These coils don't seem very big, isn't it n't?
Title: Re: What is a part called, that rectifies powerful PWM (10 A)?
Post by: MarkT on Jan 05, 2016, 05:10 pm
200uH is fairly big, 1mH is large.  Remember you need a high efficiency ferrite-cored gapped
inductor for switching usage, and if you look for 1mH 10A rated inductors you'll find they are
not small or cheap.  High current means thick wire means fewer turns means larger core, and
the energy-storage requirement indirectly means larger cores too (even though the energy is
mainly stored in the magnetic field outside the ferrite, its vital the ferrite doesn't saturate, and
ferrite doesn't need much magnetic field before it saturates.

The need for a gapped core is to store energy (a transformer doesn't store energy, so its
usually much smaller for a given inductance).  Highly magnetic materials are less able to store
energy than air/vacuum (it turns out), hence the gap.  The core serves to guide the magnetic
field so that it nearly all passes through all of the coil and delivers the field efficiently to the gap.
This allows much more compact (and thus low-resistance) winding.
Title: Re: What is a part called, that rectifies powerful PWM (10 A)?
Post by: dwightthinker on Jan 05, 2016, 09:06 pm
Where do you get 62500. The PWM is only 490, 980 if using an Uno.
Dwight
Title: Re: What is a part called, that rectifies powerful PWM (10 A)?
Post by: MarkT on Jan 06, 2016, 12:01 am
62.5kHz is 8 bit fast PWM at full-whack, no prescaler division, from 16MHz.  You can go faster, but
you get fewer than 256 levels then.  100 levels only at 160kHz, etc.
Title: Re: What is a part called, that rectifies powerful PWM (10 A)?
Post by: dwightthinker on Jan 06, 2016, 01:11 am
62.5kHz is 8 bit fast PWM at full-whack, no prescaler division, from 16MHz.  You can go faster, but
you get fewer than 256 levels then.  100 levels only at 160kHz, etc.
I see.
Many regulator chips don't go much beyond 100K and that is still a big coil.
Maybe he is looking at adding some large capacitors to reduce the ripple.
Doesn't the prescaler also effect baud rates?
Dwight
Title: Re: What is a part called, that rectifies powerful PWM (10 A)?
Post by: Unknownsymbols on Jan 06, 2016, 10:28 am
Yes. 1 mH is quite big. I thought i found a good example on digikey.com, but i mislooked it. Schurter DFK-40-0005 is 40 ∙ 40 ∙ 30 mm. Hammond 157D is also like a general adapter - that type of big. 300 uH is 30 ∙ 30 cylindric. By the way i couldn't find a way to select if they are air-gapped.... (and also they cost > 20 $, > than a lot of power suppliers themselves)
So i'm looking into raising the frequency. I supposed, but i don't know for real, can a MOSFET-driver increase the frequency?
(i know i could modulate it manually by waiting microseconds in Arduino program, or even completely inline, up to 16 Mhz / step but i'll need that Arduino to do a lot of other things, so that's not good.)
Title: Re: What is a part called, that rectifies powerful PWM (10 A)?
Post by: MarkT on Jan 06, 2016, 01:50 pm
Fixed-value inductors are usually gapped - otherwise the value is very temperature dependent and unstable.
Transformers and chokes are usually ungapped, the inductance value just has to be "large enough"
Title: Re: What is a part called, that rectifies powerful PWM (10 A)?
Post by: dwightthinker on Jan 06, 2016, 10:55 pm
Yes. 1 mH is quite big. I thought i found a good example on digikey.com, but i mislooked it. Schurter DFK-40-0005 is 40 ∙ 40 ∙ 30 mm. Hammond 157D is also like a general adapter - that type of big. 300 uH is 30 ∙ 30 cylindric. By the way i couldn't find a way to select if they are air-gapped.... (and also they cost > 20 $, > than a lot of power suppliers themselves)
So i'm looking into raising the frequency. I supposed, but i don't know for real, can a MOSFET-driver increase the frequency?
(i know i could modulate it manually by waiting microseconds in Arduino program, or even completely inline, up to 16 Mhz / step but i'll need that Arduino to do a lot of other things, so that's not good.)
Use a regulator IC. It has a frequency controlled by a resistor and capacitor.
Just use the normal PWM for the control voltage to the switching regulator.
Why make it complicated trying to push code to do simple hardwares work?
Dwight
Title: Re: What is a part called, that rectifies powerful PWM (10 A)?
Post by: Unknownsymbols on Jan 08, 2016, 10:34 am
Can you say what model of IC are you meaning?
If you mean any regulator, then i don't know where to attach PWM to there.
Title: Re: What is a part called, that rectifies powerful PWM (10 A)?
Post by: dwightthinker on Jan 12, 2016, 01:45 am
Many regulators have an external reference.
That can come from a simple RC filter of the PWM from
the processor.
You wouldn't do this with a fixed regulator ( at least not
easily ).
Dwight
Title: Re: What is a part called, that rectifies powerful PWM (10 A)?
Post by: Unknownsymbols on Jan 23, 2016, 12:59 pm
Well, i guess that's similar to a programmable DC-DC converter. It can be called adjustable, and the Vref pin will be used to set the output voltage. I didn't wrap my mind around it first, though i had seen a "reference pin" on some of them. So i think they differ in just that programmable have sort of higher level interface, like I2C, instead of Vref.
To use a RC circuit to smooth the control signal, i already know how. (The formula F=1/(2piRC)).

Maybe i'll eventually try it, but if i understand correctly, an adjustable converter will still require a lot of parts around it, which aren't easily in the datasheet. Maybe also an operational amplifier to bring the Arduino's 5 V to the needed 12 V.

....
Also difficultating the matter is that i'd need a buck converter as close as possible in output voltage to the input voltage. They seem to return at best 0,9. (Mosfet in this aspect is 0,97. And i can't yet find that high.) Or buck+boost, but they are only resistor-selected.
Title: Re: What is a part called, that rectifies powerful PWM (10 A)?
Post by: dwightthinker on Jan 24, 2016, 05:13 am
Many regulators have a + and - input lead that in the diagrams
look like an op amp.
The - lead is usually a divider from the output and the
+ lead is the VRef.
It doesn't need to be 12 volts for a 12 volt out.
The divider can be 5 volts for 12 volts out.
The arduino can easily supply 0-5 volts.
An old simple linear regulator might be the LM723 ( as I recall ).
There are a number of newer switching regulators that would
work fine as well.
Dwight
Title: Re: What is a part called, that rectifies powerful PWM (10 A)?
Post by: Paul__B on Jan 25, 2016, 03:56 am
Many regulators have a + and - input lead that in the diagrams look like an op amp.
Which will of course be because it is an op-amp.  Just part of the control circuitry.
Title: Re: What is a part called, that rectifies powerful PWM (10 A)?
Post by: Unknownsymbols on Jan 28, 2016, 12:47 am
And what about a thing like these? ZNDIY ZB-8. (http://www.dx.com/p/zndiy-bry-zb-8-dc-dc-8a-adjustable-buck-boost-cc-cv-power-supply-module-blue-silver-358336#.VqlPO2ddKVh) This seems exactly as modular as it can get. The I. C. with everything placed. But they are all mechanic-adjustable. I skipped them first because i didn't even have the idea the potentiometers can be replaced with digital potentiometers. Can it be done there?
(That model also seems lowish, can max voltage be operated for 5 hours?.... This comes to view too: unnamed (http://www.prodctodc.com/12a-adjustable-voltage-regulatoradapter-dc-532v-to-224v-automatic-step-updown-power-supply-module-for-carsolarlaptop-etc-p-548.html#.VqldJmddLn4).)

The FAQ (http://www.ti.com/ww/en/simple_switcher/faq.html) in Texas tools now got me the point - they write different solutions exist, and they can vary from more optimization available, to full "power module" board like those. And in fact maximintegrated.com has that parameter - module, but that only brings it nearer, not completely. And more importantly they don't have 10 A × 12 V.
Title: Re: What is a part called, that rectifies powerful PWM (10 A)?
Post by: dwightthinker on Jan 28, 2016, 04:57 am
Often, a digital potentiometer is not needed. Depending on the
circuit, filtered PWM output can be used as I have suggested.
One would have to see the circuit diagram to tell what
would work but all the pot is doing is providing a voltage.
Dwight
Title: Re: What is a part called, that rectifies powerful PWM (10 A)?
Post by: Unknownsymbols on Jan 28, 2016, 02:02 pm
Oh, O. K. i see. I'll have to try it, this seems the best variant i reached yet.
Title: Re: What is a part called, that rectifies powerful PWM (10 A)?
Post by: dwightthinker on Jan 29, 2016, 11:33 pm
Do show a picture of the schematic.
Some circuits use the pot from the output voltage
while others use it from the reference side.
In either case, how to hook it up is different.
Dwight
Title: Re: What is a part called, that rectifies powerful PWM (10 A)?
Post by: Unknownsymbols on Jan 30, 2016, 06:29 pm
Almost impossible to find these boards' schematics, luckily i stumbled on 1. Link beyondlogic.org / WD2002SJ on LTC3780 (http://wiki.beyondlogic.org/index.php?title=WD2002SJ_LTC3780_Synchronous_Buck_Boost_Converter_Ebay_Automatic_lifting_pressure). Images 2 and 3 have variable resistors, i guess they are them. (http://wiki.beyondlogic.org/i/LTC3780_WD2002SJ_LowVoltageCutout.jpg) (http://wiki.beyondlogic.org/i/LTC3780_WD2002SJ_AdjustableCurrentLimit.jpg)(http://http://wiki.beyondlogic.org/i/LTC3780_WD2002SJ_AdjustableCurrentLimit.jpg)This is a popular series, as far as i understood. How much can this be approximated for other modules? I don't know. Most possibly i'll need another, because it says 10A MAX, 7A long time operation.
The more closest to ≽ 10A is actually this, which is from the previous post (http://www.ebay.com/itm/DC-DC-Converter-LTC3780-High-Power-Automatic-Step-UP-Down-Power-Module-/111580295460?hash=item19fab43124:g:xfQAAOSw8d9UwSMI). It's too on LTC3780.
(Lowest VOUT is 2 V though, quite high.)

Or this, which is like the previous lesser , but 12 A (http://www.ebay.com/itm/DC-DC-CC-CV-Buck-Converter-Step-down-Power-Supply-Module-7-32V-to-0-8-28V-12A-C/381506125967?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D34493%26meid%3Ddadb923a466149f48270620033df4479%26pid%3D100005%26rk%3D1%26rkt%3D6%26sd%3D181901208950). But.... it is only stepdown. Won't reach 12 V from 12 V. (about most of the similar units, they write "differential pressure" no less than 1 V).
Title: Re: What is a part called, that rectifies powerful PWM (10 A)?
Post by: dwightthinker on Feb 01, 2016, 01:07 am
In the second drawing, VR3 is the variable resistor to control the output
voltage. The OP-amp is for current limit.
If you wanted to control the output voltage of this circuit,
You could use a digital resistor in place of VR3 or R9.
Lowering the value of R9 will cause the voltage to VOSense to go down,
causing the regulator to increase the output.
Increasing the resistance will cause the voltage to go down.
One has to look at the reference value VOSense is compared to
and the simple voltage divider caused by VR3 and R9.
You can also create a constant current source by using
the current limit control instead.
You can figure different values of sense resistor R8 as well.
There are ways to do this with the PWM but to keep it
simple, you might want to go with the digital resistor.
It is possible to slave two of these in parallel but that requires
more than I could put in a text message.
Dwight

Title: Re: What is a part called, that rectifies powerful PWM (10 A)?
Post by: Unknownsymbols on Feb 24, 2016, 06:01 pm
To double check, the Analog devices 5262 (http://www.digikey.com/product-detail/en/AD5262BRUZ200/AD5262BRUZ200-ND/750907), would it be fine for the scheme like this? It's 200 K, should be enough to raise the divider's voltage to 12 V which is the max. i need.
It's adjusting against 0,8 reference, Vout = 0,8 ∙ (1 + VR3 / R9) .

There's a thing i don't understand about the specification of potentiometers, like this. It says "voltage supply": 4,5 ~ 16 V, ±5 V. But will there be any problems if the voltage on any of the branches of the pot. goes below 4,5? I think this shouldn't make sense, do they mean it can be powered with anything in 4,5 - 16? But then why saying such thing about supplying and not saying anything particulary about the actual output / passing voltage?

subscription:
Oh, i get it. It just has an additional power line for inner resistors, which must be from 4 to 16 and so on.
Title: Re: What is a part called, that rectifies powerful PWM (10 A)?
Post by: Unknownsymbols on Apr 10, 2017, 03:41 pm
If the current limiting potentiometer is the 1 to be replaced in such a convertor, will the current through it not be too high? They print for example, here (http://www.ebay.com/itm/DC-DC-CC-CV-Buck-Converter-Step-down-Power-Supply-Module-7-32V-to-0-8-28V-12A-M2-/152440182286?var=&hash=item237e24960e:m:mjTgptJpETqxCqBh8wK5llw), something about current through the turn lamp to be 0,1 output (thus 1 ampere). What they mean by turn lamp, maybe this is the pot.?, but that would mean impossible to use digital resistors on current - they are suitable only for some 0,02 A.