Now I can see your point, and indeed it is a solution. I thought it was a joke when I read.
But what I want is to control both voltage and current limits using a microcontroller. And being able to change this values during the charge.
Using this method with uC I think would be correct way to properly charge a battery.
I'm getting some results here, but the first problem that I faced when try to control was a noise sound and heating when the wires of the potentiometer that I mentioned were to far (10cm) of the TL494.
I'll continue to do some tests here, probably trying to control the output voltage addind some circuits in the feedback loop where the TL494 read the output voltage. Try to avoid this weard noise region, souns like instability problem.
I'm an electronic engineer, just don't have much experience with smps power supply.
But I work since 2010 with electronic projects.
My idea was to come here and maybe get a discussion with someone who are developing the project too.
The link that you post I already read, and it was very helpful. Mostly because the author already brought the schematic.
Just can't use his method to control the output voltage, because I want to allow a microcontroller to control the power supply.
So the easiest way that I can think is to add a subtrator in the path between V+ and R32//C31. It's difficult to explain, but the idea is: if the output is set to 12VDC in the beginning, when I subtract 2V in the path until the TL494, the TL494 compensates generating 14VDC in the output.
Doing this I can control the output voltage using some DAC (PWM and RC filter with the VCC voltage of the TL494, around 22VDC) from the microcontroller. Thinking in using the 18f4550, for initial tests.
Already did some tests here using an power supply simulating the DAC, and get I good results, without the sound noise that I commented before.
If you see any problems with this method, please comment.
I worked with an digital potentiometer before, controlled over SPI.
Unfortunately,
all the digital potentiometer that I was able to find were limited with a maximum operation voltage around 5.5VDC. Considering the ones that have a DIP or SOIC package.
And this limitation I thought coul be to much risk to use in a first look. Since the output voltage can go until 20VDC.
I didn't know about that.
Just will avoid this solution for now because where I live is kind of difficult to find this non commom devices.
The PWM solution is easier to build, because I already have the components (LM358 and a microcontroller).
But if it didn't give me good results, I'll go search for the digital potentiometers.
