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| Film cap across bridge rectifier and new "soft" diodes |
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| T3sl4co1l:
--- Quote from: David Hess on December 10, 2018, 06:27:08 pm ---(4) I see a business opportunity here selling special diodes, capacitors, and inductors for rectifiers used in audio. --- End quote --- Funny you say that... --- Quote from: 001 on December 10, 2018, 06:48:38 pm ---I see some curcumedons in the audio net https://www.diyaudio.com/forums/pass-labs/8826-fast-vs-slow-rectifiers.html What is actual situation now? --- End quote --- ...You'll see a lot of those customers at dA. It's a pretty diverse group, ranging from a few intensely technical folks, to the feng-shui virgin-blessed crystals under the speaker cable types. So, as far as what the diodes actually do, as a reference, I wouldn't read very far into their opinions. :) --- Quote from: coppercone2 on December 10, 2018, 06:34:48 pm ---What are examples of fast and slow diodes? When you say process optimization, does that mean a traditional diode like a 1n4007 used for a rectifier has changed in specification ? --- End quote --- No, the specification hasn't changed, that's fixed by JEDEC. JEDEC specs are notoriously thin, however. Pretty much any diode can be sold as a 1N4007, assuming there's value in doing so. Better diodes cost more, so the answer is usually no, unless, say, they fail one spec but still meet another one, like the 1N4007. That doesn't mean they're worse, but it does mean there's that much more variability between parts, in the parameters that aren't specified. Diodes in general have greatly improved since those early days (when 1N4007 was first written), with soft recovery and some avalanche capability being typical. Sloppy diffusion processes gave way to precise epitaxy, ion implant and such. Impurities and defect levels have continued to improve. --- Quote ---I kinda associate what you guys are talking about with diodes using in switch mode power supplies, but for traditional applications (rectification of mains before the switching) or for rectification after a line frequency transformer, what are we looking at now? --- End quote --- Both, but yes, fast diodes have more options, more improvements. --- Quote ---Also this kind of made me think, if you have 50Hz systems and 400Hz aircraft systems, and you are doing a traditional design, should you maybe pay more attention to the diodes? --- End quote --- You might as well save the Vf (maybe 5-20% improvement) and use a slow type. Tim |
| David Hess:
--- Quote from: coppercone2 on December 10, 2018, 06:34:48 pm ---What are examples of fast and slow diodes? When you say process optimization, does that mean a traditional diode like a 1n4007 used for a rectifier has changed in specification? --- End quote --- It just means that the 1N4007 specifications do not cover its recovery behavior and some standard recovery diodes have snap-off behavior which is a problem in sensitive circuits. An example of a fast replacement for the 1N4001 series is the 1N4933 series which is the slowest of the common fast recovery rectifiers. --- Quote ---if they are changing alot, it sounds like they should have a new part number. It sounds all a bit crazy. --- End quote --- They are just changing in a way not covered by the specifications. If the snap-off behavior is a problem but you want to continue to use these diodes, then qualify them by manufacturer and verify that each lot meets your requirements. If this is a problem, then either use a diode which never displays this behavior or design the circuit to mitigate it. --- Quote ---I kinda associate what you guys are talking about with diodes using in switch mode power supplies, but for traditional applications (rectification of mains before the switching) or for rectification after a line frequency transformer, what are we looking at now? --- End quote --- This is about line frequency rectification. --- Quote ---Also this kind of made me think, if you have 50Hz systems and 400Hz aircraft systems, and you are doing a traditional design, should you maybe pay more attention to the diodes? --- End quote --- Or if it matters, include snubbers across or in series with the diodes to prevent the problem. |
| coppercone2:
is there some manufacturer of diodes that is known to keep a more consistent product out, or does additional documentation? This is kind of a compliance problem if suddenly your product line that was working fine 20 years ago starts doing something funny because a process improved. textbook chapter with some graphs about rectifier snubbing https://www.desmith.net/NMdS/Data/Linear%20Audio%20-%20Rectifier%20snubbing%20-%20background%20and%20Best%20Practices.pdf Also, whats the model of a great/good diode for audio rectifier power supplies, to be used with preamplifiers and a high power variant for power amplifiers? |
| 001:
--- Quote from: coppercone2 on December 10, 2018, 10:39:32 pm --- Also, whats the model of a great/good diode for audio rectifier power supplies, to be used with preamplifiers and a high power variant for power amplifiers? --- End quote --- IMHO Modern fast diodes like HER108 produce swithching noise at common 50Hz rectifier too isnt`it? Is capasitor still eliminate it? The second question is 40 years ago I shunt EVERY diode with cap New diodes own capasitance became low Is it mean that I must increase shunt cap value? :-// |
| chris_leyson:
Some manufacturers give figures for trr for standard recovery diodes, I think Motorola used to do it. It's not too difficult to measure and Tim, T3sl4co1l posted a design for a simple trr tester. The topic also reminded me of one of Mr Carlson's videos. Interesting part starts at 12min. |
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