5A Constant Voltage/Constant Current Regulator

[reckerd]

The ciruit worked but took about 5 minutes to charge the caps.
Also, I first connected my voltmeter to the load connections to see the range.
My full range was 14vdc-17vdc. I really need the range to be 6vdc-20vdc.
I didnt know what size transistor to use and since I had a 2N4401. I use it.
R22 is a .20 10W heat sinked resistor.
If I understood the circuit better I would try changing some things up.
Hope to hear some more from you.

[MrAl]

Hi again,


Well, the spice simulation shows a 2 farad cap charging from
0 to 20v in 13 seconds, with the pot set at 3.4k ohms.

A quick check shows this to be correct:

dv=i*dt/C
solving for dt
dt=C*dv/i
and with C=2 farad and the cap charging from 0 to 20v with
a current limit of 3 amps we get
dt=2*20/3
so
dt=13.3 seconds
which agrees with the simulation.

This tells me either something is not connected correctly or
else one of the parts blew out.
Can you check the LM317 to make sure it is still working ok?
Also, can you check the transistors to make sure they
work ok too?
Then check the wiring VERY carefully, because one little thing wrong
could kill the whole circuit.