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IllIlIlllIll
EliteData
Premium
join:2003-07-06
Hampton Bays, NY
kudos:7

Difference between transformer & SMPS 12V power supply ?

i have both of these power supplies.
after extensive testing, it seems the SMPS version is better than the XFMR version (aside from the 10 amp difference).
the questions i pose in this topic:
aside from my own extensive testing, what is the big difference here besides the weight, circuitry and price ?
why would someone choose the Astron over the SMPS ?
it seems the SMPS is much more efficient than the Astron to me.
Hams/ham repeater sites still prefer using the Astron though and i dont really get why.
both units can handle extended load times without major issues.
nevermind the fact that the SMPS is classified as a "convertor/charger", it operates perfectly fine as a power supply for radio equipment just as well as the Astron does.
12V 80A SMPS
12V 70A XFMR
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tschmidt
Premium,MVM
join:2000-11-12
Milford, NH
kudos:9
Reviews:
·G4 Communications
·Fairpoint Commun..
·Hollis Hosting

1 recommendation

Linear Supply
50/60 Hz - heavy step down transformer.
Low efficiency - pass element acts as a variable resistor.
Lower noise then switch mode
Very simple circuitry
Tolerant of short term overload due to transformer mass.

Switch mode
Very high efficiency
Light weight small size due to high switching frequency
Higher noise then linear.
Greater complexity now largely hidden due to control chip integration.
Now a days switch mode supplies are much cheaper than comparable linear.

I think I've hit the main points.

/tom


IllIlIlllIll
EliteData
Premium
join:2003-07-06
Hampton Bays, NY
kudos:7
thanks for that !
answers the remaining questions i had.
choosing the power supply is dependent on what it will be used for.
i can see why an Astron would be used now, SMPS would generate switching noise for the receiving front end.
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alphapointe
Don't Touch Me
Premium,MVM
join:2002-02-10
Columbia, MO
kudos:2
Reviews:
·Socket Internet ..
said by IllIlIlllIll:

SMPS would generate switching noise for the receiving front end.

Particularly on the lower HF bands... It's getting better, though, as the radio manufacturers are taking SMPS noise into account when designing RX front-end filters, as more operators are using them. Put a SMPS on my Kenwood TS520 and you can't hear a damn thing, but put a TS2000 on the same power supply, and the noise isn't an issue...
--
"When the hammer drops, the bullshit stops"

lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1
reply to IllIlIlllIll
said by IllIlIlllIll:

it seems the SMPS is much more efficient than the Astron to me.

SMPS designs have a lot more variation in both quality and efficiency. You have to do due diligence.

For example, Zivan makes really efficient switch-mode chargers which are surpisingly compact for even 12V/100A. »www.zivanusa.com/NG3BatteryCharger.htm

TheMG
Premium
join:2007-09-04
Canada
kudos:3
Reviews:
·NorthWest Tel

1 edit
reply to IllIlIlllIll
My guess is most are concerned about RFI.

Audible noise could be another reason, as most SMPS are unfortunately designed with forced air cooling (fans), and finding reasonably priced convection cooled SMPS is difficult.

I think the amount of cheap, poorly designed, garbage SMPS out there has given SMPS technology a bad rep. Reality is that a good quality well designed SMPS generates negligible RF noise.

Most modern commercial radio equipment has switched to SMPS these days. Yes, that even includes HF receivers and transmitters that are used for mission-critical applications.

In my "shack" I use an Astec MP6 SMPS loaded with two paralleled 12V 30A modules. Dead quiet on the HF bands and the output is rock solid. Note that Astec changed names first to Emerson Network Power and is now known as Artesyn. Anyways, I scored it on eBay used for $40. Not a bad find, considering these are ~$800 power supplies when new! If you know what to look for, quality SMPS can be found at bargain prices.


shimonmor
Premium
join:2000-12-30
Sedro Woolley, WA
reply to IllIlIlllIll
I'm not an expert but I do have an Astron VS-35 and it came with a schematic of the unit and taking the cover off...it appears that it can be easily repaired if necessary. It appears to be a high quality item (bought it for $40 on Craigslist).


tempdays

@comcast.net
reply to IllIlIlllIll
two general rules:

things fail based on parts count.
the more parts a circuit has, the more parts the circuit has that can fail.
plus more connections between them.
lower parts count means longer life.

things fail based on temperature.
wasn't the rule that every 18 degree rise in temperature cuts parts life in half?
switch mode supplies have parts, like regulators, that run at high temperatures, requiring heat sinks.
though a proper design uses parts that are big enough to not run hot. those parts are more expensive.
lower temperatures mean longer life.

---
when copper costs are high, and shipping costs for heavy iron transformers are high,
the switching supplies that don't use big heavy 50-60 Hz transformers can be cheaper.

TheMG
Premium
join:2007-09-04
Canada
kudos:3
Reviews:
·NorthWest Tel

2 recommendations

said by tempdays :

things fail based on parts count.
the more parts a circuit has, the more parts the circuit has that can fail.
plus more connections between them.
lower parts count means longer life.

In the field I've seen just as many linear supplies fail as good-quality SMPS. With good design and quality control, an SMPS is just as reliable as a good linear.

There are SMPS out there that have been operating continuously at fairly heavy loads for 30+ years and have never been repaired or replaced.

However, it is true that designing a good SMPS is a lot more difficult and complex. You can do a half-assed job building a linear and it will probably work fine for a fair length of time, but with an SMPS there's a lot more things to go "bang" if the design and construction isn't sound.

said by tempdays :

switch mode supplies have parts, like regulators, that run at high temperatures, requiring heat sinks.

In my experience, linear supplies run far hotter than the average good-quality SMPS due mosly to the fact that linear supplies often employ passive convection cooling.

SMPS actually requires far less heatsinking than a linear due to the significantly improved efficiency.

Honestly I really don't understand why people think SMPS run hot???

Again, I think SMPS tech has gotten a bad rep from all the crappy power supplies that are floating around out there.

TheMG
Premium
join:2007-09-04
Canada
kudos:3
Reviews:
·NorthWest Tel

1 recommendation

reply to shimonmor
said by shimonmor:

I'm not an expert but I do have an Astron VS-35 and it came with a schematic of the unit and taking the cover off...it appears that it can be easily repaired if necessary. It appears to be a high quality item (bought it for $40 on Craigslist).

I've used and repaired many Astron power supplies, and to be honest I wasn't particularly impressed with the quality.

Here is a brief description of just some of the issues I've run into:

-in one unit found incorrect wiring, rendering the internal over-temperature shutdown protection inoperable

-another unit was found to have several components that were not soldered at all (miraculously it worked fine for years in this condition before finally failing)

-yet another unit, tolerances between live 120VAC connections and chassis way too close for comfort (1mm clearance between live 120VAC soldered connection and chassis!)

-ineffective cooling fan placement

I'm also not a big fan of how the only thing supporting the regulator PCB in a lot of their power supplies is the filter capacitor itself.

Unfortunately "Made in USA" does not necessarily mean the quality control is any good. Sad thing is a lot of these issues and design flaws could have been avoided with very little additional cost.


IllIlIlllIll
EliteData
Premium
join:2003-07-06
Hampton Bays, NY
kudos:7
i have actually ran into that with my Astron.
after purchasing it, i opened the unit for inspection and to my surprise, i discovered some wire connections to the regulation pcb so poorly soldered that i wondered how the unit was even operating.
in addition, i discovered the transistors on the heat sink were:
1) not tightened well
2) had a very poor amount of heat sink compound
3) the rectifier block also had little to non existent heat sink compound.
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SmokChsr
Who let the magic smoke out?
Premium
join:2006-03-17
Saint Augustine, FL
reply to IllIlIlllIll
Other than noise, the main reason I would consider a good linear supply (not Astron) over a good SMPS is that the linear units typically have taken surges better in the past, and have history for a longer MTBF. Still quite a bit of that is related to the actual design and tolerances of each. At least in my experience the most likely failure in a SMPS will be a out of tolerance cap causing the circuit to not operate. While the linear will most likely have a regulator or rectifier fail spectacularly.

public

join:2002-01-19
Santa Clara, CA

1 recommendation

reply to tempdays
said by tempdays :

things fail based on parts count.
the more parts a circuit has, the more parts the circuit has that can fail.
plus more connections between them.
lower parts count means longer life.

Which make linear supplies with hot regulators fail.
Shoddy workmanship is more likely in hand soldered linear supplies.

Switching supplies fail due to voltage spikes overstress from poor layout, and excessive ripple current in fake or underspecified capacitors.
There are no hot regulators. Heat is a problem when more lossy parts are substituted by the assembly vendor.

If EMI or surge robustness are a concern, external components can be added.

Linear supplies can also be used as space heaters, or with a piece of rope in marine applications.


IllIlIlllIll
EliteData
Premium
join:2003-07-06
Hampton Bays, NY
kudos:7
said by public:

...Linear supplies can also be used as space heaters, or with a piece of rope in marine applications.

lmao !
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SmokChsr
Who let the magic smoke out?
Premium
join:2006-03-17
Saint Augustine, FL
reply to public
This past week I was in Vegas at a Broadcast trade show looking at new transmitters. One of the things I found interesting is in the high efficiency power supplies they have done away with the rectifiers, replacing them with MOSFETS and switching them on the zero cross so they can eliminate the loss inherent in a diode.

tedmarshall

join:2000-12-02

3 recommendations

said by SmokChsr:

This past week I was in Vegas at a Broadcast trade show looking at new transmitters. One of the things I found interesting is in the high efficiency power supplies they have done away with the rectifiers, replacing them with MOSFETS and switching them on the zero cross so they can eliminate the loss inherent in a diode.

This is the latest thing. Here's a controller to run 4 MOSFETs as a high efficiency full-wave bridge rectifier: »www.linear.com/product/LT4320.

lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1
said by tedmarshall:

said by SmokChsr:

This past week I was in Vegas at a Broadcast trade show looking at new transmitters. One of the things I found interesting is in the high efficiency power supplies they have done away with the rectifiers, replacing them with MOSFETS and switching them on the zero cross so they can eliminate the loss inherent in a diode.

This is the latest thing. Here's a controller to run 4 MOSFETs as a high efficiency full-wave bridge rectifier: »www.linear.com/product/LT4320.

Linear is my favorite company and I like that particular IC very much.

GaN is becoming viable for very high power. This tiny demo unit converts 5KW at 98.5% efficiency with 8ns turn-on and 3ns turn-off time.

You can't use that as a boat anchor but 5000W*0.015=75W of waste heat may warm your heart.