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Old 2nd January 2013, 10:45 AM   #21
marce is online now marce  United Kingdom
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Done a lot of mil communications stuff all SMPS, noise is not much different as previously stated. A well designed and layed out SMPS dose not add much if any noise to the envoironment. Power Line Communications, adds noise to the mains, again a adequatly designed SMPS should not add noise to the mains, that is basic EMC design.
SMPS efficient, little waste heat...
As to the most rugged design, I dont think there is anything to choose, though SMPS's tend to win on MTBF figures as they use smaller value capacitors (electrolytics being one of the limiting factors for MTBF calculations.
And as the output is DC (please no one go on about the tiny bit of AC content...) the following logic does not care
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Old 2nd January 2013, 11:02 AM   #22
freax is offline freax  Australia
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And there is the problem, a well designed and built SMPS is expensive. To the point of being rare and out of the range of DIY'ers.

PC power supplies are not well designed, they don't have high quality components, they also do not adhere to EMI interference regulations.

Us diy'ers do not have the time for this, we do not own a test chamber, we do not have the money to debug a highly complex smps psu.

We also do not have the expertiese to even replace switching transistors with a substitute in a smps WHEN it fails.

There is also the issue of the switching transistors, which when blown up usually take out other components along with them, when this happens SMPS is like a rats nest trying to diagnose and repair it, Linear psu's are not.

Wether or not you can safely build a mains connected device such as a SMPS should also not be considered to be a ******* contest, smps has no place at all in a ham radio shack simply because it has been proven time and time again that the Part 5 FCC regulations are inadequate to offer enough protection.
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Last edited by freax; 2nd January 2013 at 11:04 AM.
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Old 2nd January 2013, 11:07 AM   #23
qusp is offline qusp  Australia
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hardly any of your post reflects reality. you can fairly easily get a good SMPS supply these days, for not that much money and they DO have to design for EMI regulations. maybe not for piece of crap PC clones, but for instrumentation or just decent computers they have to. the SMPS will easily outlast the average computer lifetime and your computer is powered by SMPS whether you like it or not.

Last edited by qusp; 2nd January 2013 at 11:13 AM.
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Old 2nd January 2013, 11:22 AM   #24
marce is online now marce  United Kingdom
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Again I have done numerous SMPS's design for military/aerospace and medical use (it is one area of PCB design I specalise in), a whole spectrum of uses and thier requirements for noise etc are a lot more stringent than any Ham radio, so a competantly designed SMPS will not give you any problems, and if you are worried filter the input and output to the SMPS.
There is a forum for power supply designs with plenty of SMPS design on thereand a thread started by yours truly on EMC design in relation to SMPS and Class D design.
Not all PC power supply designs are bad, its like all electronics, you do quite often get what you pay for and sometimes less, but there are supplies out there that are competantly designed, and its not only the SMPS design it is how it isintegratedinto the rest of the system.
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Old 2nd January 2013, 01:16 PM   #25
freax is offline freax  Australia
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Quote:
Originally Posted by qusp View Post
hardly any of your post reflects reality. you can fairly easily get a good SMPS supply these days, for not that much money and they DO have to design for EMI regulations. maybe not for piece of crap PC clones, but for instrumentation or just decent computers they have to. the SMPS will easily outlast the average computer lifetime and your computer is powered by SMPS whether you like it or not.
where from?

I don't see any decent smps power supplies for sale on ebay, and the military standard smps units i've seen are $10-50 grand worth.

And who says that a computer has to last for 2-5 years? I've had 386's that are 30 years old which still work perfectly.

"wether YOU like it or not" your rude you know that.

I'm not even going to fight back with you on the first comment, because thats exactly what you would want, ******* trolls.

Oh btw your back on ignore.
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Last edited by freax; 2nd January 2013 at 01:29 PM.
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Old 2nd January 2013, 01:20 PM   #26
freax is offline freax  Australia
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Quote:
Originally Posted by marce View Post
Again I have done numerous SMPS's design for military/aerospace and medical use (it is one area of PCB design I specalise in), a whole spectrum of uses and thier requirements for noise etc are a lot more stringent than any Ham radio, so a competantly designed SMPS will not give you any problems, and if you are worried filter the input and output to the SMPS.
There is a forum for power supply designs with plenty of SMPS design on thereand a thread started by yours truly on EMC design in relation to SMPS and Class D design.
Not all PC power supply designs are bad, its like all electronics, you do quite often get what you pay for and sometimes less, but there are supplies out there that are competantly designed, and its not only the SMPS design it is how it isintegratedinto the rest of the system.

Thank you! I now know where to go for competently designed smps designs and for properly filtering the input and output of smps power supplies.

This information isn't easy to find if you don't know what to look for.
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Old 2nd January 2013, 05:20 PM   #27
marce is online now marce  United Kingdom
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Heres the link:
Switcher EMC design
The trouble with SMPS's is that they are unforgiving due to the higher frequency and high dI/dt, whereas linear are more benign and will tolerate bad layout etc better (or with less noise).
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Old 2nd January 2013, 11:16 PM   #28
kp93300 is offline kp93300  Malaysia
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Hi freax,
I read the Project 77 and am too lazy to build the circuit and I find Lt 1084 reg has enough current capability for my atom based pc.
I hope you will build it and give us the feedback.
cheers

kp93300
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Old 3rd January 2013, 12:56 AM   #29
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Today you can buy switching regulators that run at 4MHz. At my job we have opamps with 60db of gain running from DC-DC converter bricks. With a bit of filtering they are pretty quiet. Most SMPS today have very little ripple on the output, maybe 50mv p-p at full load. This is not the 1970s anymore.
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Old 3rd January 2013, 04:56 AM   #30
qusp is offline qusp  Australia
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like ebay is the yardstick for quality SMPS...


Quote:
"wether YOU like it or not" your rude you know that.

haha interesting phrase to be offended by (as well as mispell and add your own capitals like I was shouting) quite the complex youve got going on there. 'whether you like it or not' simply referred to the fact that the board is littered with local SMPS, powering it with a linear power supply is a bit redundant. not one iota of personal commentary.

I like it how you state i'm on ignore like its something I should care about...

i'm using a fully regulated 16A +/-55v (2 x 600W) SMPS for the amps i'm building, its from Audiopower, the noise is ridiculously low, as are the emissions.

Quote:
DC: 1mV rms(100Hz-100mA @68V): 47mV rms(100Hz-5Amp @68V) Both polarity.
HF:-84,0dB ( Fo: 150,4 Khz,2x100mA @68V )
it operates at >90% efficiency, with 150nS power response and in the span of up to 500kHz the highest peak is -84dB at 150.4kHz

but I gather they also do work for industry as well as MIL, so even though I havent looked for a low voltage version, i'm sure its available from someone for less than 5-10K... . these are ~$200ea. used to power a class AB poweramp, THD+N is 0.0002% and full power 16A +/-55v pulse performance is not like anything ive ever seen before from a linear supply.

as mentioned, its not the 20th century anymore.
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