Products > Test Equipment

Power supply for home lab - do I really need a R&S?

<< < (14/22) > >>

KungFuJosh:

--- Quote from: blackdog on October 03, 2024, 09:11:19 pm ---As promised some measurements I made on LAB power supplies I own that have an enable key that are here on the test bench.

--- End quote ---

What probe were you using to do these measurements?

Thanks,
Josh

moerm:

--- Quote from: 2N3055 on October 03, 2024, 05:43:55 pm ---
--- Quote from: rf-messkopf on October 03, 2024, 05:18:53 pm ---
I don't disagree with that statement but this behavior is quite common for a number of supplies from reputable manufacturers.


--- End quote ---

Maybe it is time we start reconsidering difference between good reputation and legends and lore..
And assign brand value according to actual results and not "reputable brand" urban legends...

--- End quote ---

I logged in specifically and just to thank you for that.

But being logged in anyway ...


--- Quote from: Martin72 on October 03, 2024, 10:32:45 pm ---Fast current control is a good thing for sensitive components if you want to connect them directly to the power supply.
However, there are situations where this is rather counterproductive.
Certain DC/DC converter circuits have an inrush current that can easily be many times the normal input current.
If this is not taken into account when switching on, it can, at best, lead to non-functioning without side effects, but in some cases it can lead to permanent current flow, causing the circuit to “hang”.
As always, the dose makes the poison.
However, I also prefer series resistors for LEDs, it's just in my nature... ;)

--- End quote ---

I get it but let me play a bit Cassandra ...

With a *linear* *lab* PSU my main concern is potentially sensible stuff (being powered). You are right, there are exceptions and corner cases in almost everything which leads to a need for deciding for priorities (mine I just told). Besides switchers tend to care little about the quality of input power, many circuits however *do* care.

Some of my - almost all self designed and built - PSUs do have a "don't limit (DUT) inrush current for 3 or 10 ms (selectable) with a 0 ms option (~no tolerance, strictly stick to the set current limit)" feature and most of them have a separate "emergency brake" set to double the set current limit (max the highest output current of that supply). Reason: a supply should be "generous and tolerant" but not to the point of getting damaged itself.

What I've seen here (thanks guys!) would have been, had I known it (I didn't) yet another reason to  design and build my PSUs myself rather than buying "well known brands". I'm not really surprised though that "famous A-tier brands" sell what I call crap; maybe my wording is a bit harsh but "A tier brand" quality certainly is not what I see here (modulo one "B-tier" brand).

Whatever, thanks for all the data (and nice images *g).

ArdWar:

--- Quote from: pdenisowski on October 04, 2024, 01:28:11 am ---One (potentially ignorant) question:  has the behavior of the NGE (or other manufacturers' supplies) been outside of its published specifications? 

--- End quote ---

Personally I'm not exactly sure since it is tricky to figure out which specifications override what, and whether those interrelated specifications should be interpreted strictly ("any" exceed) or loosely ("all" exceed).
For example, if we take my NGP800 load current regulation spec strictly (< 0.01% + 5mA) then my peak result of 160mA inrush at startup is well beyond the allowable spec range of 10mA * 0.01% + 5mA, which basically allows for 15.001mA max inrush.
The inrush duration is also well beyond "Load recovery time" spec of 400µs, so can't use that either to handwave.
NGP800 does not specify CV-to-CC transition time. Is this the "get out of jail free" card? :o

Fuse delay time *may* allow this, but that's protection function while the discussed performance should be regulation function. And sure enough if I set the fuse to protect close to the setpoint (20mA) it did indeed trip on itself during startup. Job well done there.

mhsprang:

--- Quote from: Martin72 on October 03, 2024, 10:32:45 pm ---Fast current control is a good thing for sensitive components if you want to connect them directly to the power supply.
However, there are situations where this is rather counterproductive.
Certain DC/DC converter circuits have an inrush current that can easily be many times the normal input current.
If this is not taken into account when switching on, it can, at best, lead to non-functioning without side effects, but in some cases it can lead to permanent current flow, causing the circuit to “hang”.
As always, the dose makes the poison.
However, I also prefer series resistors for LEDs, it's just in my nature... ;)

--- End quote ---

Agreed on inrush currents, but those will be obvious if you switch on the power.

But that is not the point of all of this. If we set a voltage on our PSU, we expect that PSU to output that voltage, no more. Similarly, if we set a current, we expect that PSU to output that current, no more. If a manufacturer specifies that a set current may be +/-5% + 5 mA, I do not expect the output current to be 14 times higher than that. And if the design shows transients at enabling the output, I want to see that beforehand in the datasheet and not after the purchase on my bench.

mhsprang:

--- Quote from: pdenisowski on October 04, 2024, 01:28:11 am ---Thanks to everyone for all the analysis and comparison.  As I mentioned above, I've already communicated all of this to the power supply team in Munich and we are investigating.  It would also be very helpful if the OP could contact our technical support about this and/or contact their R&S sales representative as well.

One (potentially ignorant) question:  has the behavior of the NGE (or other manufacturers' supplies) been outside of its published specifications? 

I've seen lots of test results for lots of supplies (and again, many thanks for those), but I haven't seen any comparisons of experimental results to published specifications.  That would have been one of the first things I checked - is a given supply "in spec"? 

My apologies if that's a dumb question.

--- End quote ---
Yes, I sent an email to R&S support yesterday about this.

And yes, I feel this is outside the specifications for exactly the reasons ArdWar just stated in his reply #73, just above.

Navigation

[0] Message Index

[#] Next page

[*] Previous page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod