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Topic: What is a part called, that rectifies powerful PWM (10 A)? (Read 4503 times) previous topic - next topic

Paul__B

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.

Unknownsymbols

#31
Jan 28, 2016, 12:47 am Last Edit: Jan 28, 2016, 01:56 am by Unknownsymbols
And what about a thing like these? ZNDIY ZB-8. 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.)

The FAQ 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.

dwightthinker

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

Unknownsymbols

Oh, O. K. i see. I'll have to try it, this seems the best variant i reached yet.

dwightthinker

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

Unknownsymbols

#35
Jan 30, 2016, 06:29 pm Last Edit: Jan 30, 2016, 10:25 pm by Unknownsymbols
Almost impossible to find these boards' schematics, luckily i stumbled on 1. Link beyondlogic.org / WD2002SJ on LTC3780. Images 2 and 3 have variable resistors, i guess they are them. 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. It's too on LTC3780.
(Lowest VOUT is 2 V though, quite high.)

Or this, which is like the previous lesser , but 12 A. 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).

dwightthinker

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


Unknownsymbols

#37
Feb 24, 2016, 06:01 pm Last Edit: Mar 04, 2016, 04:47 pm by Unknownsymbols
To double check, the Analog devices 5262, 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.

Unknownsymbols

#38
Apr 10, 2017, 03:41 pm Last Edit: Apr 10, 2017, 03:48 pm by Unknownsymbols
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, 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.

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