The idea of this thread is to compare linear and switching PS through some adequate parameters measures
. TELL ME IF IT IS STUPID AND WHY
!
I don't have the necessary means (and know-how!) to do this but:
can anyone get some measures at oscilloscope from a SMPS (e.g. the famous Meanwell's) and a linear PSU (of course the last one after rectifier and big good capacitors)?
It would be interesting to know the amount of remaining switching/source frequencies (25kHz/50-60Hz) and (probably more interesting) ability to supply instantaneous peak of power(how is it possible to do this?Signal alterning full power pink noise?).
Let's make a list of measured PS...
Can anyone begin, specifying PS model, features and price, possibly the best known?
. TELL ME IF IT IS STUPID AND WHY!I don't have the necessary means (and know-how!
) to do this but:can anyone get some measures at oscilloscope from a SMPS (e.g. the famous Meanwell's) and a linear PSU (of course the last one after rectifier and big good capacitors)?
It would be interesting to know the amount of remaining switching/source frequencies (25kHz/50-60Hz) and (probably more interesting) ability to supply instantaneous peak of power(how is it possible to do this?Signal alterning full power pink noise?).
Let's make a list of measured PS...
Can anyone begin, specifying PS model, features and price, possibly the best known?
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Because there are literally thousands of different design solutions out there, and they all perform differently, and it's unrealistic to even attempt to make a comparison between even a small percentage of the designs out there.
Because testing procedures and equipment should be highly standardized in order for any comparison to be useful.
Because there are too many parameters to test for, and I don't see many people here spending hours and hours testing power supplies in order to fill a database.
I firmly believe that power supplies can and should always be engineered (or bought) starting from the (technical, commercial and organizational) requirements the project poses on them, and then working towards the optimal solution. In my opinion, it's not feasible to list all of the possibly relevant parameters of PSU's and comparing them willy-nilly.
You are right of course, and I didn't explain very well....I don't mean e real comparison, and probably we have to make a selection of parameters (only the most important one) and to point out a standard procedure (hope someone can help!). The object of the measures could be only famous kits (for example Sure tk2050 or Hifimediy or snubberized gainclone or other...IMVHO if we gather a lot of data we can understand better the interaction between amplifier and the supplied current in relation with sound quality). The main purpose is to see if differences in sound quality between PSs result from used technology or in project quality (ok, both, but which is the most important?). Let's reshape the purpose and procedure to make it realizable, if it can be useful as I tried to explain...
I don't know much about the width of cats, but the length of a cat seems to be proportional to temperature. At least until the length of the cat reaches saturation. However, if the cat is operated within its saturation limits, the temperature may be approximated by, temp = tan^-1(length).
On a more serious note, I think the idea of comparing power supplies has some merit. However, aside from measurements of ripple, noise, line rejection, etc. I doubt any useful comparison can be made from spec sheets. One really has to evaluate the supply in its intended application under realistic load conditions to compare supply A vs supply B.
~Tom
On a more serious note, I think the idea of comparing power supplies has some merit. However, aside from measurements of ripple, noise, line rejection, etc. I doubt any useful comparison can be made from spec sheets. One really has to evaluate the supply in its intended application under realistic load conditions to compare supply A vs supply B.
~Tom
It might help to make the comparison a lot more general and perhaps anecdotal with the required caveats. You can discuss trade offs very generically IMHO..
Cost, weight, thermal considerations, regulation, noise spectrum, topologies, etc can all be generalized. Obviously this would be of more use to the newbie and less so for a seasoned design engineer.
Cost, weight, thermal considerations, regulation, noise spectrum, topologies, etc can all be generalized. Obviously this would be of more use to the newbie and less so for a seasoned design engineer.
Operation of the cat in parametric modes outside of the recommended saturation limits should be avoided particularly after refueling.. This mode of operation is not recommended and may potentially void the warranty on surrounding objects.
See I disagree that it is impossible to test the power supplies independent of the system. This was a commonly held belief amongst computer enthusiast until about 4-5 years ago. The only way they would test a PSU is load up a system. Then along came the website JonnyGuru and eventually HardOCP followed (jonnyguru was a mod there). They showed you can actually get better information by loading the system, checking ripple, checking the waveforms, varying the load amounts, testing instantaneous performance (by switching in a 10A load) and checking the waveform deviations. It turns out all of these things correlate very well with system stability and overclockability. As a part of this, they found out a lot of PSUs were heavily over rating their output (it could put out 500W but the ripple rose to around 300mV on the 12V rail).
as above, one power supply may perform admirably with a particular dynamic load and very poorly with another. without specifying a particular load requirement, measurements are pretty useless and if you do, you have limited the usefulness of such a database to the users of that particular design. i just dont think you have thought this through
So couldn't be this a useful information for kit assemblers or designers?
What I'm trying to explain
is that measures are only to get a sense of different PSs under different loads, to allow diy guys to better match electronic equipment with PS, on the base of some measures and objective facts; I don't know how can be done these, but Pedro gave an example that the problem is "only" to find the right way......On one hand I'm very sorry but probably it's a bit too complicated idea to express for my poor english! On the other I'm wondering if it's more probable that you understood and I don't understand your replies and give up my quite crazy idea!
There are certain generic statements which can be made about SMPS vs linear (vs unregulated) PSUs. These are generally well known already. Beyond that you are talking about a specific design used in a specific context.
To measure a piece of string you have to specify how much you are going to stretch it, and to what extent you are interested in individual fibres extending beyond the bulk string. These are context issues. Measuring string (or cats) is much easier than measuring power supples.
To measure a piece of string you have to specify how much you are going to stretch it, and to what extent you are interested in individual fibres extending beyond the bulk string. These are context issues. Measuring string (or cats) is much easier than measuring power supples.
I was hoping this thread would evolve a bit further...
I have a turntable project on the burner and need a power supply for the platter motor. I want to keep it simple (low cost) while still offering reliable performance.
I know switching supplies are out, due to their noisy nature (and what they do to the power line they draw from) but the ability to use 100-240VAC input without changing anything is certainly attractive...
So, if I want a low-cost, high-stability and low-noise power supply (that is ideally off the shelf), does this exist? Do I have to build it to meet my goals? If so, could someone point me to a kit (preferably) or schematic to (try and) work from?
I have a 'custom' schematic but it seems a bit beyond me and I am not comfortable (potentially) offering up something like that for sale that I made myself. I just don't have the experience of (most of) the forum here, with an accompanying lack of confidence in my skill set in this area.
Thanks in advance.
I have a turntable project on the burner and need a power supply for the platter motor. I want to keep it simple (low cost) while still offering reliable performance.
I know switching supplies are out, due to their noisy nature (and what they do to the power line they draw from) but the ability to use 100-240VAC input without changing anything is certainly attractive...
So, if I want a low-cost, high-stability and low-noise power supply (that is ideally off the shelf), does this exist? Do I have to build it to meet my goals? If so, could someone point me to a kit (preferably) or schematic to (try and) work from?
I have a 'custom' schematic but it seems a bit beyond me and I am not comfortable (potentially) offering up something like that for sale that I made myself. I just don't have the experience of (most of) the forum here, with an accompanying lack of confidence in my skill set in this area.
Thanks in advance.
Obviously I fully agree with you, but if we make such an analysis specifying all the context issues IMHO -of course- there can be two utilities: who's building the same project will fully benefit from measures of a specific PS (this could be the case of famous kits-e.g audiosector gainclone or sure tk2050 or some tube preamp such as aikido...don't know!But there's a finite number of these!) ; who's building a different project with comparable load specifics will benefit only partially, understanding the direction he has to move to...
This might be a crazy idea, but I'm throwing it out there for comment.
Perhaps you could construct (for lack of a better term) a pseudo-load that in essence is a power amplifier but not intended to actually "be" an amplifier for audio. This PsL could be demanding in it's requirement for voltage at the rails or current (say, up to 80V without the amplifier itself clipping) and have suitably adequate dummy loads (perhaps 4ohm) as the output.
An input of suitable level could then be applied that should draw a known amount of power from the PS. Measurement of the output vs input and display of the waveform would give you a value representing the PS's ability to provide the power at instantaneous and continuous loads. I would expect the instantaneous load testing to be most useful since continuous load testing is relatively straightforward on the bench, but having both from the same PsL might be illuminating when comparing results.
The PsL could be a standard schematic and bill of materials (BoM) that others could build. Actual sound quality would not necessarily be important, so parts quality could be reasonably modest (although adequately high bandwidth might be useful).
A CD could be made with the test tones at various levels; you could then adjust output to equal 2.0V @ 0dB FS and others could download the disk image or FLAC files. Standardizing the tones and the PsL would make relative comparisons useful so people could post results to an online database (similar to, say, computer benchmarks).
In essence, the idea is by limiting the variables to the PS alone it reduces the inherent complexity of the problem.
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Programmable loads are available which will do this, the frequency response doesn't need to be stellar because the amplifier decoupling capacitors will remove the the high frequency components of an amplifier load.
The chief differences between SMPS's and conventional PSU's that I can think of are:
Weight, SMPS's are lighter than conventional PSU's
Volume, in small sizes SMPS's are smaller than conventional PSU's
as power increases the difference diminishes.
Failure, SMPS's fail more frequently than conventional PSU's, this situation is improving but an SMPS has more components to fail.
Service, SMPS's are more difficult to service, especially if a circuit diagram is not available, think about that if the design life is more than a few years or the PSU is being used in a remote location.
SMPS's can change output voltage or current faster than conventional PSU's but not as fast as linear regulated PSU's
The other differences are largely design parameters which can change according to the application.
Feel free to add more, this is a general list for any type of PSU application not just consumer electronics.
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