TheOne
New Member
I found this PSU **broken link removed**
on one of the links posted by a member on this forum. Being an old PSU designer myself, I took a closer look at it. The first thing I noticed was that it was drawn in a very unconventional (maybe not for the Greek designer) way with the GND at +ve and the input at -ve. Looking at the diagram I was convinced that this design was flawed and could not possibly work. I even tried to read the diagram upside down :? to try and figure out the operation in a conventional way, just incase I missed something.
So I decided that I will plug the circuit into my simulator to prove that the designer/circuit was wrong and myself correct.
Well the first diagram showed the result after just firing up the simulator. (My component numbering order is different that Sam's). I was very surprised :shock: when I adjusted the pot and the output varied between 50 - 60V! (as promised in the article)
I thought, well maybe the designer was more clever than I thought in his own unconventional way. So I decided to evaluate the regulation, response and ripple rejection in some hope to find something wrong to say "Ha!" to. (just to make me feel better)
In the next diagram I switched the load on to draw 2A at 50V. Suddenly the output fell to 0.99V with only 38.5mA flowing in the load. After rechecking my circuit against Sam's for any errors, I decided to place some metering at strategic places to confirm my suspicions. I placed a voltmeter over the 2N3055 (as I was convinced it was reversed biased) and a mA meter in the lines feeding current from Q1/2. Hitting the button on the simulator confirmed my suspicion. The current in the load resistor on the output came from some leakage due to junction breakdown by Q1-Q2 as the sum of the 2 mA meters displayed almost the same reading. The balance came via the 100k and the b-e of Q3 and the zener diodes etc. The 2N3055 was also reversed biased c-e by 76V. Some voltage regulation however was supplied by Q3 under no load.
So I don't know what's up with the Sam circuit and why he never corrected it on the page (It is marked 2/02). Maybe there's another page somewhere with the corrected circuit that I don't know about? There's some polarity errors (swapping c-e Q1/2) in this version. If you happen to know Sam, tell him I say Hi and that he should fix the error (or explain how it works) before more people get frustrated with this design should they try to build it.
on one of the links posted by a member on this forum. Being an old PSU designer myself, I took a closer look at it. The first thing I noticed was that it was drawn in a very unconventional (maybe not for the Greek designer) way with the GND at +ve and the input at -ve. Looking at the diagram I was convinced that this design was flawed and could not possibly work. I even tried to read the diagram upside down :? to try and figure out the operation in a conventional way, just incase I missed something.
So I decided that I will plug the circuit into my simulator to prove that the designer/circuit was wrong and myself correct.
Well the first diagram showed the result after just firing up the simulator. (My component numbering order is different that Sam's). I was very surprised :shock: when I adjusted the pot and the output varied between 50 - 60V! (as promised in the article)
I thought, well maybe the designer was more clever than I thought in his own unconventional way. So I decided to evaluate the regulation, response and ripple rejection in some hope to find something wrong to say "Ha!" to. (just to make me feel better)
In the next diagram I switched the load on to draw 2A at 50V. Suddenly the output fell to 0.99V with only 38.5mA flowing in the load. After rechecking my circuit against Sam's for any errors, I decided to place some metering at strategic places to confirm my suspicions. I placed a voltmeter over the 2N3055 (as I was convinced it was reversed biased) and a mA meter in the lines feeding current from Q1/2. Hitting the button on the simulator confirmed my suspicion. The current in the load resistor on the output came from some leakage due to junction breakdown by Q1-Q2 as the sum of the 2 mA meters displayed almost the same reading. The balance came via the 100k and the b-e of Q3 and the zener diodes etc. The 2N3055 was also reversed biased c-e by 76V. Some voltage regulation however was supplied by Q3 under no load.
So I don't know what's up with the Sam circuit and why he never corrected it on the page (It is marked 2/02). Maybe there's another page somewhere with the corrected circuit that I don't know about? There's some polarity errors (swapping c-e Q1/2) in this version. If you happen to know Sam, tell him I say Hi and that he should fix the error (or explain how it works) before more people get frustrated with this design should they try to build it.
