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0-30 Vdc Stabilized Power Supply


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The original design when properly built will work without any problems.
I favor the latter supply over my BK supplies along with an Hp supply.
Although, the BK & Hp can provide much more current, the simplicity of the 0-30V bench supply is far more useful for my purpose.
Added note: as i stated in a prior post/thread it can be a teaser since it has a few very unique features.

The ripple at 30V is very respectful, well within the aspect of the circuit design.
I have yet to notice any problems under full load at higher voltages.

Additionally, when building the supply make sure to board space any component that will generate heat; power resistors, diodes, zener's etc...

The 2N2219 along with the output transistor require the proper heat sink.
Obviously, with any power supply that will be used to maintain high current over an extended period of time should be carefully thermally sized.

Adequate clearance must be provided for the PT, use a high quality military grade or similar; do not purchase an inexpensive one from a surplus house...
Search the internet for a quality transformer, expect to pay around $45.00 - $60.00 (USA currency)

Furthermore, if the output drive transistor is mounted within the case a ventilated design along with a quality DC fan should be used.
Remember, fan noise can be reduced considerable by lowering the fan voltage, a small/simple DC fan control circuit consisting of a voltage divider network along with a transistor is sufficient.
One could also use a darlington (TIP120) if fan current is above average.

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The 24VAC transformer has a peak of 34V which is dropped to 32VDC by the rectifier bridge. The tiny 3300uF main filter capacitor will create a peak ripple voltage of 2V so the lowest part of the unregulated supply is 30VDC when the load current is 3A.

The opamp U2 has a max output voltage of 28.8V and R15 has a voltage drop typically of 1.3V so the max voltage at the base of the 2N2219 is 27.5V. The typical Vbe of the 2N2219 is 1.0V and the typical Vbe of the 2N3055 is 1.1V so the typical max output is only 25.4VDC, not 30V.

If the transistors have low gain but are still within spec then the max output voltage is only about 22VDC.
That is why I recommend using a 30VAC transformer and a huge main filter capacitor for this project.


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0-30VDC Stabilized pictures.

The supply was completed around 6 months ago, what an excellent project; a true performer!
Hopefully, i can post some pictures showing the enclosure and digital display module; magnificent original design!
In the past i really enjoyed taking digital pictures, anymore i lost my interest for digital photography.

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I remember at PENN a variety of students that always wanted me to provide an outline concerning a completed project; always looking for the answers without making any attempt on their own.   :'(

I would kindly state the below in a very respectful manner:

The only way you will learn the questions you are asking is to pull the legs one by one from the centipede.
When you have completed the above you will gain a much better understanding.  :)


I've been designing power supplies for a living for past 15 years. I am VERY familiar with parameters I asked about. I was just curious as to the knowledge level a one semester class in "Advanced Power supply design and circuit application" gets you. It would be QUITE unusual for the average hobbyist, student or even engineer to have access to some of the instruments needed to obtain some of those parameters. This isn't a learning exercise for me, so I'll ask again if you care to share some of the results of your "complete testing"?
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Are you familiar with the curriculum requirement concerning Electrical Engineering?

In order to take an Advanced class study at Penn it is usually administered on a Graduate level.
A variety of courses are necessary before the latter course is even available.

My home laboratory could never duplicate the available test instruments at any University where most of the more elaborate stress testing was performed.
A basic Astro-Med Dash10 that most Universities have in multitudes is outside of my home lab affordability.
One has to take advantage of other resources when available, i believe you get the idea...

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Hi Omni,
It is easy to make basic measurements of the power supply:

Voltage Test:
1) Set the current pot to max and set the voltage pot for 30.0VDC at the output without a load.
2) Then connect a 10 ohms 100W resistor to the output.
3) Measure the output DC voltage and the output AC voltage.
The output voltage should be very close to 30.0VDC and the AC voltage should be less than 5mV.

Power test:
1) Connect a 1 ohm 10W resistor to the output.
2) Turn the voltage pot to 3.0V and the current pot to max.
Watch the original project smoke.
It should not get hot enough to make smoke. It should survive but it probably won't.

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Load Transient Recovery time
Load Effect
Current Limit Characterization
Efficiency & Power Factor
Start-up response
Turn-off response
Temperature variation

The above is an abridged Agilent power supply test method that is used within the engineering community.
Additionally, i am not sure as to the level of control your concept will provide.

Truthfully, it would be best to use an electronic DC Load that is much more controlled.
I mean no disrespect concerning your method but would rather use a more defined approach.
Maintaining a controlled temperature variation while testing is difficult to achieve on a normal test bench using large power resistors.
Furthermore, charting the test using a recorder has many advantages, one could easily view an outside parameter that placed the UUT in a non-linear (abnormal) condition.
The latter failure may not have been the UUT but rather the uncontrolled method of test.

However, what i may consider notable you may believe otherwise.

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Fear does not resolve into any formal test, maintaining a controlled method is an engineering approach/method that deserve's merit both from a logical standpoint along with a more calculated technique!

Furthermore, i stress a prior post notation:

The above is an abridged Agilent power supply test method that is used within the engineering community.
Additionally, i am not sure as to the level of control your concept will provide.

Please, understand i did not make-up the procedure.
The above outline is a proven method used throughout the industry both in Government and Commercial sectors.

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Yes, I did "my time" at Northeastern University some 30 years ago (loved that co-op thing... paid for school).

I hate to disappoint you, but the

Agilent power supply test method...

IS NOT an industry standard for testing power supplies, it is Agilent's!! While its possible that some schools/courses may have chosen "their" test methodology to use in the classroom, it should NOT be presented as something thats
...a proven method used throughout the industry both in Government and Commercial sectors
it IS NOT! Yes, there is a certain core parameter set that everyone tests, but by no means is it patterned after something Agilent does.

While I'm not familiar with the Astro-Med Dash10...  after a google search, that does not appear to be a very good instrument to do power supply testing (I understand having to use what you got, but...). A sample rate of 250K/sec and a bandwidth of 25kHz just won't get you there.  It might be acceptable for some basic tests on a linear, but forget ANY off-line switchers or DC-DC's. I don't see any gain/phase modules under conditioners and accessories. Using that instrument, how exactly were you able to generate Bode Plots to determine stability? Did you generate them over temperature? With and without capacitive loading? Where was your "injection point"?

Transient testing with a active load unfortunately SUCKS, but everyone sorta does it. I have yet to see an active load, whether running in current mode or resistive mode, that didn't have overshoot... you see the problem with that, right?

So one more time, would you care to share your test result's?
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You don't need to blow it up by seeing that it doesn't make 3V at 3A without overheating.
You don't need to see that it doesn't make 30V at 3A.
You don't need to see a very high amount of ripple on its output at any output higher than 25V and at 3A.

Just pretend that it works very well.

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Wow...let's just gang up on the guy.  ::)
I think if he is happy with the power supply that he built, he doesn't owe anyone test results. Just a note to the community that he is satisfied with the project.
Admin of this site also built the original and it did not cause such problems as burning up.
I see 90 some pages of discussions based on theory suggestions. Where are the test results for all of these? Why does someone have to provide test results because he does not agree with another 's theory? Let's request the theory guy provide the test results on both designs since he has implemented the discussion of change.
(In other words) You have made your opinion. Let it go.


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The Astro-Med dash10 is a high end multi channel chart recorder used to chart a multitude of variables in graph form.
The results while testing will show conclusive if an outside problem has occured.

Additionally, how you can criticize Agilent is totally beyond my understanding, the latter manufacturer has some of the most intelligent/professional engineering based throughout the World.
I have been employed as a Govt electrical engineer for a long time, during the latter time we cater to Agilent for their superb support.
The Agilent method of testing a power supply is essentially the same concept used by a variety of high end resource facilities.

I agree with MP, the aspect of going into a deep discussion would be pointless...
However, i will provide a hint concerning how to perform temperature stability.
Hopefully, it will provide some useful insight.


Thermal plate, NI multipoint thermometer using specific locations on the plate (multiple thermocouplers), 2 - Neslab chillers (hot - cold), hot supply tank, cold supply tank along with programming in visual basic or C+ in reference to transistion/cycle time connected via the RS-232 port.


This subject is becoming rather tiring, i would think with a so-called University degree you would have an idea as to how the above is performed?
Take the time and keep yourself up to date regarding new concepts, the latter will prove to be very helpful.


You appear to enjoy continuing a losing argument, your method of testing is very subjective.
After reading other threads/posts it is obvious you cannot accept a failure, the latter is the only way you will step beyond your superficial ego; learning is a virtue!


"(In other words) You have made your opinion. Let it go."  DITTO!

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The owner of this site, Mixos, reported, "... that's what we are trying to do with this power supply right now, to make it reliably live up to its specs !!"

Mixos reported that, "Trying to get more then about 25 V at 2.1 Amps show increasing ripple in the output, and trying to get higher voltages than that was not possible."

As Mixos reported to Staigen in a personal message, his project broke down and needed repairs.
Staigen wrote, "The reason for the delay is that the PSU Mixos have and do some testing on, brooke down. He has now repaired it, and hopefully he can do further tests this week."

Others have also reported that the project cannot make 30V at 3A and parts get extremely hot. Theory proves it and shows why.

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The original expensive transformer doesn't have enough voltage and current for the improved version. It would be a waste to throw it away. I don't know how long it will last when it will be overloaded sometimes.

I don't know how long the frying time will be before the overheated transistors, rectifier diodes and resistors fail. Maybe you can add a high velocity fan.

The ICs have a supply voltage that is higher than their max allowed voltage. I don't know how long they will last.

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The schematic is the same except there are two output transistors to share the heat. The output transistors have emitter resistors to equalize their gain.

The improved parts list has an upgraded transformer, upgraded rectifier, upgraded main filter capacitor, high voltage ICs, transistors that are rated for more heat and resistors with a higher power rating. The main zener voltage reference diode is selected with a part number and its supply resistor has its value selected for best performance.
Here is the improved parts list: 


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This subject is becoming rather tiring, i would think with a so-called University degree you would have an idea as to how the above is performed?
Take the time and keep yourself and keep yourself up to date regarding new concepts, the latter will prove to be very helpful.

Yes tiring if you don't have the answer. Let me reiterate... maybe you didn't read the previous posts carefully enough and missed it before, for the last 15 years of my working career I've been employed as a power supply design engineer, guess what I do... design power supplies!! I am VERY familiar with those tests and many more. I know exactly how to perform them and what the proper equipment is to do it!! I NEVER said I didn't know how to do the test. It is presumptuous of you to assume that just because someone asks a question, that they don
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