Problem with variable regulated power supply

[Animesh Maurya]

Hi all,

I'm having two, 317 variable regulated power supply like this one:
http://www.uoguelph.ca/~antoon/circ/vps.htm

I thought the supply will simply act like a battery, you put them is
series their voltage will sum up, but to my surprise this is not
happening!

I expected, 15 and 15 will add up to give 30volts, but when I measured
the voltage it first appeared 19volts and then gradually decayed to
2.8volts.

Now what is wrong with his one?

Thanks

Best regards,
AM

 

[burbeck]

Hi all,

I'm having two, 317 variable regulated power supply like this one:
http://www.uoguelph.ca/~antoon/circ/vps.htm

I thought the supply will simply act like a battery, you put them is
series their voltage will sum up, but to my surprise this is not
happening!

I expected, 15 and 15 will add up to give 30volts, but when I measured
the voltage it first appeared 19volts and then gradually decayed to
2.8volts.

Now what is wrong with his one?

hi,
it is possible to have +15 0 -15 in this way but requires separate
transformers or sepparate secondary windings, for each half of the
supply. hope that helps
regards
bob

 

[John Popelish]

Hi all,

I'm having two, 317 variable regulated power supply like this one:
http://www.uoguelph.ca/~antoon/circ/vps.htm

I thought the supply will simply act like a battery, you put them is
series their voltage will sum up, but to my surprise this is not
happening!

I expected, 15 and 15 will add up to give 30volts, but when I measured
the voltage it first appeared 19volts and then gradually decayed to
2.8volts.

Now what is wrong with his one?

Thanks

Best regards,
AM

You have shown the schematic for only one supply. How did you you
construct two supplies. Does each contain everything shown on this
schematic, or did you only duplicate part of it?

 

[Animesh Maurya]

[email protected] (Animesh Maurya) wrote in message
Hi all,

I'm sorry for replying my own post.

I forgot something crucial, both the regulators are sharing a same
transformer, in fact I never bothered about this issue. It was my
foolish assumption.

Thanks for your time.

Best regards,
AM

 

[John Popelish]

[email protected] (Animesh Maurya) wrote in message
Hi all,

I'm sorry for replying my own post.

I forgot something crucial, both the regulators are sharing a same
transformer, in fact I never bothered about this issue. It was my
foolish assumption.

Thanks for your time.

Best regards,
AM

I hope you have figured out how this keeps the two supplies from being
independent from each other, so that they cannot be stacked in
series. Either you need a center tapped secondary, with the center
tap acting as the common between positive and negative supplies (and a
positive and negative regulator chip) or you need two isolated
secondaries (or two transformers) so that there is no internal common
connection, except the one you make o the output of the supplies.