Velleman K7200 Gerber file

[Jagi]

Here is a working version of it, The current part does not seem to be able to supply more than 3 amps for some unknown reason in proteus but in real life I get the full 5amps. The voltage side of things work in proteus as real life but may be slight difference  on the R20 readings compared to real life one, But a least I can play with this to get some where close

I did download your project but it seems like you are using an ultra latest version of Proteus and so it fails to open in Proteus 8.9.
Anyway, I did download the K7200 pdf from Vellman's site, and I see they are using a low side current sense. Which is okay, because the control needed is quiet simple. However as Bob noted in his post http://www.sonsivri.to/forum/index.php?topic=68701.msg199357#msg199357, I would concur that using a high side current sense makes more sense for a lab power supply. The difficulty will be finding a current sense amplifier that operates "rail-to-rail" within a moderate DIY budget. LTC makes some pro grade high side current sense amps, which you can check out.

[Sideshow Bob]

I did download your project but it seems like you are using an ultra latest version of Proteus and so it fails to open in Proteus 8.9.
Anyway, I did download the K7200 pdf from Vellman's site, and I see they are using a low side current sense. Which is okay, because the control needed is quiet simple. However as Bob noted in his post http://www.sonsivri.to/forum/index.php?topic=68701.msg199357#msg199357, I would concur that using a high side current sense makes more sense for a lab power supply. The difficulty will be finding a current sense amplifier that operates "rail-to-rail" within a moderate DIY budget. LTC makes some pro grade high side current sense amps, which you can check out.

I think INA 193 can do the job. It is quite cheap and can handle up to 80v. It has a wide supply range independent of the input voltage

[Jagi]

I think INA 193 can do the job. It is quite cheap and can handle up to 80v. It has a wide supply range independent of the input voltage

How about ACS712, we have used it in some of our products. It can sense both AC and DC currents. Comes in SMT 8 pin and it is quiet easy to interface to the micro.
Attached datasheet for ACS712.

[Sideshow Bob]

Ok due to covid I have been tinkering some with a power supply What do you think? I have not built it but dit look viable. It pass funtions test but I just got it working. Not done any ripple testing etc.
EDIT: This meant as a response to Wizpic. The design is very like what a discrete 723 could look like. But the current limit function has a much larger span what you find in bare bones LM723 design. The error function is the green LED. As long as output move from the setpoint. The LED will be on. If current limit kicks in or the regulator goes into drop out the LED will will not light
EDIT 2This is only meant as an conceptual design. Please see it as such, not a verifeid project. If you build it will probably work perhaps. Bot how good i do not know at this point. ALSO remember I skipped many things like decoupling capacitors etc
EDIT 3: I would like to swap out the instrument amplifier (current sense) with a INA193/196. But I did not have any spice modell for it in Proteus. The parts are also select from what I could find in proteus and at the same time kind what you easy can find in stores. And at the same time cheap

[Wizpic]

I’ve down loaded the first version but not tried it, I’ll down load the latest version and should be able to have a play with it the weekend, has the gaffer is off this week and not been able to get I to workshop to play, I keep telling her I wear the trousers in this relationship once she’s chosen the colour 

It will be interesting to have a look and play around with it, proteus is good but sometimes it works slightly different in the real world I find, but most of the time it performs better in the real world than it does in proteus.

I’ll keep you posted might even build it up in real time,

is it still based around this one with the same values and similar wiring .
The only reason I ask I may be able to use the PCB’s I have spare and just hard wire the op-Amps into the Baird as I’ve not opened the file yet to have a look at it

[Sideshow Bob]

I’ve down loaded the first version but not tried it, I’ll down load the latest version and should be able to have a play with it the weekend, has the gaffer is off this week and not been able to get I to workshop to play, I keep telling her I wear the trousers in this relationship once she’s chosen the colour 

It will be interesting to have a look and play around with it, proteus is good but sometimes it works slightly different in the real world I find, but most of the time it performs better in the real world than it does in proteus.

I’ll keep you posted might even build it up in real time,

is it still based around this one with the same values and similar wiring .
The only reason I ask I may be able to use the PCB’s I have spare and just hard wire the op-Amps into the Baird as I’ve not opened the file yet to have a look at it

I have made a new version. Changed a few things to the better. And cleaned up the schematic and also used real life resistor values for the circuit. The design is doable in real life I will think. The LT074 can handle up to 40 volt (absolute max is 42 volt). You may be able to take out the LM723 from your circuit and test I think. But note I use a high side current sense resistor. In proteus I can with out any problem have a current equal to 5A with a single 2N3055. I think you said in your proteus design you could only get about 4 volt with 2 2n3055. It can go down very low in voltage, less than 0.3 volt with some current draw at least.
AGAIN PLEASE NOTE: This is a CONCEPTUAL design. There is lot of details where I live in an ideal circuit world. not a real world

[Wizpic]

Slideshow Bob,
I've not forgot about having a look or play with your new version of the PSU you done, Only been really busy at work (which is good thing under the current circumstances) plus ideally I want to get this version fully up and working. I'm still working on the control software and hardware side of things. Only I've now changed the displays to 3.2" TFT'S screens which is working loads faster than the other screens I was using. Plus much better looking.

I've also added 2 PCF8574's for the buttons and LED indicators to show what's selected and active.

I'm now happy to start the PCB design for the controller, Tidying up the code and adding the rest of the calibration routines can be done at the later stage or while I'm waiting the for the PCB'S to come.