0-30V Stabilized Power Supply

[redwire]

We seem to have lost the extensive discussion on this power supply topic.    I attached what I believe is the latest version.   I could not find the updated parts lists to attach.    


UPDATE 11/21/12     Updated latest Version  

[PicMaster]

Thanks Red wire, I did look for this the other might and wondered what happened to it,

Does anyboady have the version for the OPA445 op-amp they have come back in stock at RS and ordered 10 of them so that I can continue with my version.

Not sure if the above will work the same ?

Thanks

[audioguru]

Hi PicMaster,
The OPA445 high voltage opamp will not work in the latest modification.
I didn't keep a schematic for the project with the OPA445 opamps because it was nearly the same as the original except for a couple of corrections. Here is the parts list for it:

[redwire]

Audioguru,  do you have a copy of the last parts list using the alternate chips.  I seem to remember some of revisions were in red.

[audioguru]

Hi Redwire,
Here is the latest parts list that uses the new opamps. it is missing the 10v zener diode.

[redwire]

Thanks,  Now we have a sketch and some parts.   We can continue the discussion.

[limbo243]

Hy Guys!

Okay - after 1 damaged Zener and 2 damaged power transistors my power supply is now finished.
My experience:
- I used the MC34072 oamps with max.44V instead of the MC34071. With the MC34072 I was not able to do the offset compensation. So the current limiting became a problem. ( When I turned the current limiting to minimum, it stopped limiting the current and damaged the power transistors with 24A  output ). So I used a 68Ohm resistor for R17 and all worked perfectly.
- I used a 2x30V - 230VA Transformer with 32.47VAC without load. The problem is the voltage without load of about 45.91VDC  -  too much for the oamp. So I decided to use D15 in my shematics.
In practice, the max voltage is about 44.1V so it will also work without D15.

Here are pictures of my working Power Supply, my shematics with the (hopefully...) correctly bill of materials for my shematics.
I decided to give you my bill of materials because there are a view mistakes and missing parts in the existing list.

Sorry for my bad english - hope everyone can understand me  

means Markus

PS: More pictures in my next reply

Update: After a view tests at maximum output (30V 3A) I saw that D15 (10V Zener) in my schematic only allows an max output of about 24V at 3A. Or about 2.7A at 30V...
So I decided to throw D15 away and replaced it with a peace of wire. Now I am able to get 30V with 3A.
If someone has the same problem as I (The rectifier voltage is to high for the oamps with 44V) you can use D15 which should have only as much voltage as you need to get under the 44V. The voltage in my circuit is about 39.6V - 44V and nothing is damaged.

[limbo243]

Here are two more pictures

[limbo243]

And the last picture:

[audioguru]

Hi Limbo,
Your power supply looks good.
I think the tiny 2N2219 Q2 driver transistor will melt if the output is shorted and the gain of the 2N3055 transistors is low. It will try to dissipate more than 3w which it cannot do even with a clip-on heatsink. A BD139 real power transistor should be used with a medium size heatsink.

I do not understand why the current regulation failed when it was turned down.

Since you reduced the unregulated positive supply by 5.6V with a zener diode can your project supply +30V at 3A without ripple?

[limbo243]

Hi audioguru!

Thank you 

The schematic is for simulation only. I added a small statement in the schematic: "For parts value see bill of materials". There you can see that I used a BD139 for Q2. In LTspice IV there is no BD139 in the database 

I also don't know why the current limiting failed by min current. I was not able to find a mistake in my circuit. I decided to say it is because of the oamp offset 

I have no oscilloscope to see if there is a ripple by 30V at 3A. I only have the small multimeter which shows 30V and 3A. But if I get the chance for an oscilloscope I'll post a picture.
Do anyone have a 10Ohm 90W resistor for testing the power supply at maximum? 

by limbo

[bohko]

Hi!

I would like to add to that circuit fine tuning for voltage and current. So i am asking where to put it on that circuit on first post?
My minimum output is 40mV not 0V and i cannot correct it with RV1 it has no effect. 
Did i do something wrong or is it normal to get 40mV?

TNX in advance
Bye

[audioguru]

Hi!

I would like to add to that circuit fine tuning for voltage and current. So i am asking where to put it on that circuit on first post?
My minimum output is 40mV not 0V and i cannot correct it with RV1 it has no effect. 
Did i do something wrong or is it normal to get 40mV?

TNX in advance
Bye

You can add fine-tuning pots in series with the coarse adjustment pots but they will be always set to the wrong position.
If you made the latest circuit with MC34071 or TLE2141 opamps then RV1 adjusts the 0V output to 0V if your voltage adjustment pot can give a 0V output.

The output capacitor C7 makes the output positive without a load if it is an electrolytic type. A film capacitor will not.

[dracu_n_dulap]

hello.
could you please tell me if there are any other equivalents to opamps used in the final version of the schematic? because i could not find tle2141 or mc34071
thanks