QSXPS Rev.1 - How to get 12V and 5 V out

[rclourenco]

Hi Per-Anders,

I will now start to build my Board, I will need +5/0/-5 volts, or +12/0/-12 volts (haven't decided yet), can you tell me what I need to do? What transformer should I use?

Many thanks.

[peranders]

How much current is it about?

Do you need 12 or 5 V? Can you choose this?

For 5 V you need 9 VAC and for 12 V 15 VAC, possibly 12 VAC. This has to do with your transformer, size and type (toroid or EI core).

If you answer my questions I can calculate the necessary changes.

[rclourenco]

Thanks for your repply, still I don´t know if I will use 5 or 12 volts, I will use R-Core transformers, of 9 or 12 (have both, 30VA). If you could be so kind as to make the calculations both for 5 and 12 volts, I would appreciate it.

many thanks and regards,

[peranders]

Dedening of how much current you will need and the available raw voltage you may be forced to adjust R1-R8 and R9-R12 to a lower value.

12 V out
Gain = 2
Vref = 6 V (LM431)

R39 = 6k8
R41 = 10k
R47 = -
R49 = -
P1 = -

5 V out
Gain = 2
Vref = 2.5 V (LM431)

R39 = 0R
R41 = -
R47 = -
R49 = -
P1 = -

-12 V out
Gain = 2
Vref = 6 V (LM431)

R42 = 6k8
R40 = 10k
R48 = -
R50 = -
P2 = -


-5 V out
Gain = 2
Vref = 2.5 V (LM431)

R42 = 0R
R40 = -
R48 = -
R50 = -
P2 = -

[rclourenco]

Just finished my board with some changes as follows:
+5 V out
Gain = 2
Vref = 2.5 V (LM431)

R39 = 0R
R41 = -
R47 = Maintained initial value
R49 = Maintained initial value
P1 = Maintained initial value

-5 V out
Gain = 2
Vref = 2.5 V (LM431)

R42 = 0R
R40 = -
R48 = Maintained initial value
R50 = Maintained initial value
P2 = Maintained initial value

This allows to exact tune +5,00V and -5,00V on P1 and P2
Many thanks and Happy new Year.

[peranders]

Sure you can use a pot but persnally I'll avoid it (due to reliability reasons) unless it's really important to have a very exact output voltage. I know the feeling though to have exact 5.000V or whatever.