Nelson Pass said:
Ahhh, here you go! Soft/fast recovery isn't the best, but it's good enough!
Actually, when working with linear power supplies, diodes are probably the least important factor. (That's not to say they should be ignored however)
Schottkys are usually in switching supplies, where you need the fast reverse recovery time with a low foreword drop. Think of a 3.3Volt 60Amp supply switching supply. With a 1 volt diode drop, that's 60W lost in diodes alone! Now, look at a 3.3Amp, 60Volt supply, same diode and only 3.3W lost in the diode. With low voltage output it pays to spend the $$$ on the Schottky... ...At 60Volts is becomes a little questionable.
Again, if you build a million of them, and save 50 cents on each one...
On linear supplies, I use what ever is cheap and big!
-Dan
The measurements were taken from the - & + of the bridge rectifier (without load) and the scope was set to AC coupled. I didn't record down the time base (I'm using the AUTO function of the scope) as I'm not really interested in measuring anything (just wanted to see the difference between standard and schottky rectifier).
AC traces
Even the trace with the Schottkys is a long way from a clean sine wave. How about posting the traces (standard vs. Schottky "downstream" from a pair of fairly conventional filter caps? That's what the amp or opamp will see.
I suspect that even with Schottkys (Freds, etc) that the a good PSRR shouldn't be neglected.
By the way, what is the typical set up to measure PSRR? I understand the idea and what it intends to show but I'm don't know how one goes about measuring it (especially with my meagre means).
Even the trace with the Schottkys is a long way from a clean sine wave. How about posting the traces (standard vs. Schottky "downstream" from a pair of fairly conventional filter caps? That's what the amp or opamp will see.
I suspect that even with Schottkys (Freds, etc) that the a good PSRR shouldn't be neglected.
By the way, what is the typical set up to measure PSRR? I understand the idea and what it intends to show but I'm don't know how one goes about measuring it (especially with my meagre means).
Normal bridge rectifier module (not those fast recovery type).
Actually, I don't have a clue what those measurements mean,
but theoretically schottky should sound better (no reverse recovery). I was also told that the sound quality of your amp depends greatly on your PSU, so I decided to use the schottky rectifiers with Nichicon Gold tune caps (300,000uF).
Actually, I don't have a clue what those measurements mean,
but theoretically schottky should sound better (no reverse recovery). I was also told that the sound quality of your amp depends greatly on your PSU, so I decided to use the schottky rectifiers with Nichicon Gold tune caps (300,000uF).
I don't think half-wave rectifying a signal from a function generator is much of a test. The reverse recovery characteristic depends upon the forward current. In equipment where the conduction angle is small and the current draw is large, like a power amplifier, the diodes have a much more difficult task.
Going crazy!!
Icceman, I apologise for asking questions which you already answered. My Internet is crazy over here. When I 1st asked you about how you tested, the last post was your's from 12-16-2002 06:09 AM. When I went backwards through the post just now, suddenly there are 10 more inbetween. Don't ask me how
Any way, now I got about 5 answers to my questions.
Thanx alot
Icceman, I apologise for asking questions which you already answered. My Internet is crazy over here. When I 1st asked you about how you tested, the last post was your's from 12-16-2002 06:09 AM. When I went backwards through the post just now, suddenly there are 10 more inbetween. Don't ask me how
Any way, now I got about 5 answers to my questions.
Thanx alot
jwb,
Thats absolute right, but it was all i´m able to put together in 5 minutes.
I´m on a better test setup right now.
real (big) transformer, rectifyer is bridge, not half. Please give your comment about should i use a capacitor or not, and how much load(i hope pure resistive)?
For test i have on hand a 400V25A normal bridge rectifier, a hand full of suber fast / soft recovery stealth diodes, and some 10 and 20A 100V schottkys.
Thats absolute right, but it was all i´m able to put together in 5 minutes.
I´m on a better test setup right now.
real (big) transformer, rectifyer is bridge, not half. Please give your comment about should i use a capacitor or not, and how much load(i hope pure resistive)?
For test i have on hand a 400V25A normal bridge rectifier, a hand full of suber fast / soft recovery stealth diodes, and some 10 and 20A 100V schottkys.
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