Help for power supply.

[moutoulos]

I have this power supply (0-30VDC  20A) and I would like someone to tell me If I can convert it to 0-20A.  And how ???  :-[  please.
I test sometimes small pcb, and if they are wrong... it burned (pcb)  >

View attachment 37715

 

[audioguru2]

Hi Moutoulos,
That circuit would make a lot of smoke if you tried a 2V load at 20A. Each output transistor would try to dissipate 190W and would melt.

If you want current adjustment and regulation for it then you must add an adjustable current regulator circuit to it.

 

[ante1]

Hi moutoulos,

Before this circuit was changed (from the original by WA0AUQ), it had a 18Volt transformer and it was intended for a fixed 13.8V output. It would work fine this way!
This is the original:

View attachment 37716

 

[moutoulos]

  I dont understant ... the circuit work very well ... (with fans).

you must add an adjustable current regulator circuit to it.

Yes but , I don't know the circuit.  Can you help me ?.

Hi moutoulos,

Before this circuit was changed (from the original by WA0AUQ), it had a 18Volt transformer and it was intended for a fixed 13.8V output. It would work fine this way!
This is the original:

So .... I agree with you, (edit from me),  but you don't answer in my questions,  and this is the point. :-\
I don't have any problem with power supply ... it work two hours every day (test car amplifiers...13V) the last two years.
Well  :'( 0-20A??

 

[ante1]

Hi,

I was worried about the (0 – 30Volts) not the 20A if the circuit stays as the original at 13.8V I can see no big problems with it supplying 20A (with an 18Volts transformer). If I understand you correctly; what you like to have here is an adjustable current regulation 0 to 20A.  If you look at the datasheet for the LM723 you see the pins CL and CS (2 and 3). These are the current limit and the current sense inputs; the formula for the “shunt” resistor are included and is pretty strait forward.
You can forget about the 0 – 30 Volts @ 20A for this circuit (as Audioguru already told you)!

 

[moutoulos]

Hi again

You can forget about the 0 – 30 Volts @ 20A for this circuit (as Audioguru already told you)!

Ok but where is the wrong into the circuit ?  I don't understant the fault :-\

 

[ante1]

The problem is; there is too much power to “burn away” for the circuit to survive! Simply put; (20A times 40 Volts = (800W / by 4 transistors)) = melt down!

 

[audioguru2]

Hi again



Ok but where is the wrong into the circuit ?