Does this schematic make sense?

[Carbox312]

Hi,

I have a few power supplies/transformers with voltages around 17-20V, I decided to turn them into bench power supplies.

The schematic is based on the diagram from this discussion:

https://forum.contextualelectronics.com/t/alexs-linear-power-supply-build-log/1235

I also added a preregulator from this topic:

https://hackaday.io/project/4407-elbsupply-simple-linear-bench-supply

and removed the two operational amplifiers that doubled the ADC voltage. Instead of that, I plan to directly supply a 0-2.5V signal from the DAC.

I'd also like to add an indicator for when the CC (constant current) mode is active. Would simply adding an NPN transistor controlled by the output of the U4 amplifier do the job? Additionally, while browsing for lab power supplies schematics online, I noticed that a few stability components might be missing (eg. antiparallel diodes at opamp inputs). Does this power supply have a reasonable chance of working properly?

Thank you for all your answers!

[MrAl]

Hi,

I have a few power supplies/transformers with voltages around 17-20V, I decided to turn them into bench power supplies.

The schematic is based on the diagram from this discussion:

https://forum.contextualelectronics.com/t/alexs-linear-power-supply-build-log/1235

I also added a preregulator from this topic:

https://hackaday.io/project/4407-elbsupply-simple-linear-bench-supply

and removed the two operational amplifiers that doubled the ADC voltage. Instead of that, I plan to directly supply a 0-2.5V signal from the DAC.

I'd also like to add an indicator for when the CC (constant current) mode is active. Would simply adding an NPN transistor controlled by the output of the U4 amplifier do the job? Additionally, while browsing for lab power supplies schematics online, I noticed that a few stability components might be missing (eg. antiparallel diodes at opamp inputs). Does this power supply have a reasonable chance of working properly?

Thank you for all your answers!

(Attachment Link)

Hello,

Taking a brief look it does look like it's got all the necessary parts for a linear supply with a switching power supply front end.
It's got:
1.  Voltage feedback.
2.  Current feedback.
3.  Tracking regulator.
4.  Even has a constant current dummy load.

You would have to test all those components to make sure they work as intended.  That means making sure the individual sections work ok, and that also means making sure the transistors get the required gate drive when needed.
I would assume you would do a simulation next anyway, and then also test the response speed.  The response to an overcurrent would be an important thing to test.  I mention this because I see U2 gate being driven with a 1k resistor, and Q3 gate being driven with a 10k resistor.  Those two may need to be lowered quite a bit, but you could check that in a simulation before you bench test it.  Bench testing is a must BTW as well as life testing under conditions of full load.
You should also test to see that the tracking regulator keeps the output of the switcher at a reasonable voltage level for all outputs, and of course never goes too low.