Mr RB
Well-Known Member
Hi, this project has been on my to-do list for a while (for when I finally get some free time haha).
I have a nice 300W 24v toroidal transformer and a 20 amp analog panel meter, and would like to make a good high current lab PSU that goes down to zero volts. There are quite a lot of times I have needed to test high currents at low voltages, ie testing shunt resistors, wiring, DC motor stall characteristics etc.
Ideally these are the features I would like;
20v max, at up to 15A
20A from 0v to 15v
good voltage regulation right down to zero volts
analog ammeter placed before the voltage regulation
current limiting placed before the voltage regulation
I doubt if doing it directly with a switchmode circuit would work as the zero volts output (or very close to 0v) becomes a very short duty cycle and very high peak current.
So initial thoughts are to use a switchmode circuit as the main PSU followed by a very low voltage drop linear circuit dropping maybe 2v. The idea is that it's fairly easy to build a switchmode supply at 2v 20A using a conventional design.
It might be feasible to do it with just a switchmode voltage regulator, and a 30amp bridge rectifier on the output wired to act as a 3v 60Amp diode, with the voltage feedback taken AFTER the diode so the whole PSU can go down to zero volts.
I welcome any suggestions including op-amp or comparator type which are good down to 0v, of suggestions involving using a negative rail just for the regulator if that will be needed.
I have a nice 300W 24v toroidal transformer and a 20 amp analog panel meter, and would like to make a good high current lab PSU that goes down to zero volts. There are quite a lot of times I have needed to test high currents at low voltages, ie testing shunt resistors, wiring, DC motor stall characteristics etc.
Ideally these are the features I would like;
20v max, at up to 15A
20A from 0v to 15v
good voltage regulation right down to zero volts
analog ammeter placed before the voltage regulation
current limiting placed before the voltage regulation
I doubt if doing it directly with a switchmode circuit would work as the zero volts output (or very close to 0v) becomes a very short duty cycle and very high peak current.
So initial thoughts are to use a switchmode circuit as the main PSU followed by a very low voltage drop linear circuit dropping maybe 2v. The idea is that it's fairly easy to build a switchmode supply at 2v 20A using a conventional design.
It might be feasible to do it with just a switchmode voltage regulator, and a 30amp bridge rectifier on the output wired to act as a 3v 60Amp diode, with the voltage feedback taken AFTER the diode so the whole PSU can go down to zero volts.
I welcome any suggestions including op-amp or comparator type which are good down to 0v, of suggestions involving using a negative rail just for the regulator if that will be needed.