Jung SR schemo/layout

daArry

Member
2004-10-15 11:19 am
Hey,

I'm new to these improved psu designs but would like to try some for +30/-10V operation. Current load shouldnt go over the rated 1.5A max of the LM317 so from the published ckts I assume I don't need to change anything except the feedback resistors around the opamp to set the output voltage...

Here's a schemo I've drawn up of an exsisting schem found on this forum somewhere (of the + supply):

[IMGDEAD]http://notapplicable.co.uk/audiolab/jung+.JPG[/IMGDEAD]

I've layed out a single sided PCB too: (inspired from designs whilst searching this forum):

[IMGDEAD]http://notapplicable.co.uk/audiolab/jung+_pcb.JPG[/IMGDEAD]

We good to roll?

Cheers,
 
daArry said:
Hey,

I'm new to these improved psu designs but would like to try some for +30/-10V operation. Current load shouldnt go over the rated 1.5A max of the LM317 so from the published ckts I assume I don't need to change anything except the feedback resistors around the opamp to set the output voltage...

Here's a schemo I've drawn up of an exsisting schem found on this forum somewhere (of the + supply):

[IMGDEAD]http://notapplicable.co.uk/audiolab/jung+.JPG[/IMGDEAD]

I've layed out a single sided PCB too: (inspired from designs whilst searching this forum):

[IMGDEAD]http://notapplicable.co.uk/audiolab/jung+_pcb.JPG[/IMGDEAD]

We good to roll?

Cheers,

Yeah, looks not bad.
Couple points (in the positive spirit): C2 is a waste. The diode will have a dynamic impedance of say 1 Ohm. Plus the intrinsic emitter resistance that is unbypassed. That 100uF will not measurable change things, let alone audible. It takes up too much PCB space.

The PCB can be improved.
At the left, the area C1, C9, C8 can be MUCH tighter, making for shorter connections. Rotate caps for shortest tracks. On the right side, R7, ZD1, RV2, R5 should be moved directly close to the opamp. C4 can be rotated, all to give a smaller, tighter PCB. Don't make wide tracks for small-signal lines. they take up too much space. Wide tracks here only make sense for the input, output and ground lines. The rest is all small-signal.
But your layout is clean and the grounding looks OK to me.

Jan Didden
 
daArry said:

Thanks for your comments - here's an updated layout:

[IMGDEAD]http://notapplicable.co.uk/audiolab/jung+_pcb_2.JPG[/IMGDEAD]

Much smaller brd size now ;)

The board looks great now.

You could accomodate things a bit more by moving Vout out to the border of the pcb and GNDout to be just below it. As it is now it's difficult to get to.

If you rotate C5 clockwise and move it up a bit you might be able to do that.

On the lower side C6 could be rotated to be 90 degrees to the IC, allowing a bit more space for different types.

Include AD817 as a DIP option to the AD797, which seems to be a "conflictive" option.

If you are considering an only-SOIC part as the AD825 you should put the tracks for it on the pcb, if you are designing it from zero.

One of the good things of the Jung regulator was the "sensing" ground. Aren't you implementing any?


Carlos
 

daArry

Member
2004-10-15 11:19 am
Hey Carlos,

The reason for the placement of the vin/vout, gnd_in/out holes was so I could sit the pcb on vero stripboard and each would have it's own copper line from the off. Then, on one end I'd have the rectifying ckt and the other the regulated outs on screwfix connectors...

Thanks for the heads-up on the opamps - for the smd only parts i was gonna attach the part to a dip ic socket by bending the legs outwards and soldering it underneath...

WRT the sensing ground - from what i've seen it's all joined up somewhere along the way anyway so I was just goin for a quicker solution by attaching all grounds on the brd from the get go...or have i missed something?
 
daArry said:

WRT the sensing ground - from what i've seen it's all joined up somewhere along the way anyway so I was just goin for a quicker solution by attaching all grounds on the brd from the get go...or have i missed something?


Well, you missed why the grounds should be kept separate and only joined at the powering point, close to the device you are going to power.

Perhaps you should read the original Gary Galo article on the matter.

Whether this issue is important and how, it would be nice to hear from others too.

Carlos
 
Looks good but here are a couple of thoughts from me:

C6 is probably to no use at all becasue of the long traces and if you put it nearer the output you would probably get oscillations. I solved this by inserting a small resistor between output and pin 7 of the opamp. By this achieving good decoupling of the opamp and isolate a bit towards the output.

You may move T3 a bit and there draw the trace from the out to the LM317. You need only a small trace like 20-30 mil. By this you will remove a rather long loop. It may not be important.

You can also make some small adjustments in order to get a more compact solution.

T1 up a bit
D1 up and left
T2 left
IC1 left

Out connection up, left

C3 left

and the rest of the package a bit left.

Strive to have a fatter ground trace.

Maybe 100 nF at the input would be appropiate.

I wonder also have much good D3, D4 along with modern opams.

15 V out than a real short circuit.

Pin 7 0 V
Pin 3 +7V
Pin 2 -7 V
Is this enough to damage an opamp?

With diodes:
Pin 7 0 V
Pin 3 around +-1 V
Pin 2 around +- 1 V

and not more than 0.7 volts between the inputs.

If you happen to have more gain than 2 or less then you will get several volts above or below pin 7 at the inputs.

So in real life under normal conditions, how much good do those diodes. They do no harm, I'm sure. Maybe add some capacitance but compared to 500 ohms impedance it's not so much.
 

Greg Erskine

Member
Paid Member
2002-01-05 11:56 pm
Sydney
hi daArry,

Looking good. ;)

After a quick look the only point could make is the size of the pads on a single sided board "may" need to be larger. I find most standard components seem to be designed for double sided PCBs. Just a word of warning: I've never actually made a PCB.
 
carlmart said:
Well, you missed why the grounds should be kept separate and only joined at the powering point, close to the device you are going to power.

Perhaps you should read the original Gary Galo article on the matter. [snip]

Maybe he should read my ;) article on it, #3 in the series (Gary's was #4). Audio Amateur 1995 series. I did concentrate a lot on the virtues of remote sensing.

Jan Didden
 
janneman said:

Maybe he should read my ;) article on it, #3 in the series (Gary's was #4). Audio Amateur 1995 series. I did concentrate a lot on the virtues of remote sensing.

Sorry, Jan. I think you are right. It's been such a long time since reading them that I forgot about what belonged to whom.

What I do remember about your article is the question on what chip to use, considering the advantages vs the disadvantages of using the AD797, which proved quite unstable. Time seemed to have confirmed that "treacherous ground".

You also mentioned how tricky it was doing a good design for this project, if I am not wrong.

BTW: very interesting your comments on another thread on whether a ground plane was essential for this design.


Carlos
 
carlmart said:
What I do remember about your article is the question on what chip to use, considering the advantages vs the disadvantages of using the AD797, which proved quite unstable. B]

I think the main reason for chosing AD797 was the low noise(right? anything else?) . Many years have passed now and there are lot's a good alternatives.

I think performance between OPA134 and THS4601 is the range now and there are many types, altough AD825 seems to be pretty ideal.
 

daArry

Member
2004-10-15 11:19 am
Thanks again guys...

Peranders, I've got the layout more compact from your suggestions :) just a cpl points I need to be clear on...

C6 is probably to no use at all becasue of the long traces and if you put it nearer the output you would probably get oscillations. I solved this by inserting a small resistor between output and pin 7 of the opamp. By this achieving good decoupling of the opamp and isolate a bit towards the output.

So with C6 left in (or even if not stuffed) still add a resistor from the opamp V+ to output? I guess I could add this 'offboard' on top of the opamp...but would the AD need a heatsink - from the little I understand I've only seen this done when biasing opamps into classa...

WRT decoupling the opamp - just a 100n on the pin7 to gnd ye?

You may move T3 a bit and there draw the trace from the out to the LM317. You need only a small trace like 20-30 mil. By this you will remove a rather long loop. It may not be important.

Do you mean joining the the collecter of T3 and output of the LM317 at the back of the board? So end the signal at the LED ye?

I wonder also have much good D3, D4 along with modern opams.

Well for the pos reg I'll be needing 30V so will be going with the AD825 - I guess that means these diodes can go then?

Cheers
 
daArry said:
Thanks again guys...

Peranders, I've got the layout more compact from your suggestions :) just a cpl points I need to be clear on...



So with C6 left in (or even if not stuffed) still add a resistor from the opamp V+ to output? I guess I could add this 'offboard' on top of the opamp...but would the AD need a heatsink - from the little I understand I've only seen this done when biasing opamps into classa...

WRT decoupling the opamp - just a 100n on the pin7 to gnd ye?



Do you mean joining the the collecter of T3 and output of the LM317 at the back of the board? So end the signal at the LED ye?



Well for the pos reg I'll be needing 30V so will be going with the AD825 - I guess that means these diodes can go then?

Cheers

The thing to do is check the data sheet and see what the abs max input voltages are AND the abs max differential input voltages. The last data will probably be the limiting factor. From there you can decide if you need the diodes.

Jan Didden