86% Efficient AC-DC ATX supply

**ColdPhreze** · 11-22-2004, 12:38 PM

Tony, we can't really blame OPUS for most of the problems users are experiencing. I have been keeping up with those threads, and it seems a recurring theme that many having trouble have been overloading their OPUS for some time.

When I first signed up with mp3car and learned of people saying OPUS would handle over 150 watts, I warned them they would have troubles in the long-run when they overload an OPUS, as my friend did. It is why I decided not to use an OPUS with my setup: I didn't want any problems as I was going to draw much more than 150 watts.

As a rule-of-thumb, you will severly shorten the life of a PSU if you draw more than 80-90% of it's stated capacity. Following that rule-of-thumb, you can safely draw 120-135 watts from an OPUS (these a approximate, but are a good practice when designing a PC). Also, remember that you could be pulling more current on one rail than it is designed for, and much less on another, still be within 120-135 watts, but the PSU won't last becuase that one rail being stressed will die.

For now, the *best* solution for a high power pc is either DC-AC-DC, or the Keypower 250W. Please don't flame me. Just because you have been using an OPUS for several years at over stated capacity, doesn't mean it is the norm. We are seeing the norm unfolding on this forum, and anyone who designs power supplies will agree overloading one will cause it to die prematurly.

ColdPhreze

**eCar™** · 11-22-2004, 02:55 PM

I'd expect the efficiencies of the KP and Opus to be closer than what you think.

Opus rates theirs at "optimal load". KP rates theirs at "typical load".

Neither one says what that load is. And you didn't mention what your typical load would be.

I wish someone who had both (if there is someone with both), would do some testing (at various loads).

**eCar™** · 11-22-2004, 03:04 PM

Additionally the Salmex doesn't mention what load that it's 85% efficient at. You woudn't be running it at its full load (wher it is likely to be most efficient), if your other options include Opus.

**Tony S** · 11-22-2004, 07:38 PM

"Just because you have been using an OPUS for several years at over stated capacity, doesn't mean it is the norm." ColdPhreze, I guess you read my old sig line. My system's changed since then but anyway I've not overloaded my Opus. I agree that most users pro'lly are. The average person (are we average here though?

) doesn't know about electronics and electronic components so this doesn't surprise me. Luckily sites like this exist where we can help each other out. Still, short of overloading, I found it odd that now all these problems arise. Coincidence? Maybe. We'll find out as time goes on.

**MrPerfectionest** · 11-22-2004, 09:22 PM

As a rule-of-thumb, you will severly shorten the life of a PSU if you draw more than 80-90% of it's stated capacity. Following that rule-of-thumb, you can safely draw 120-135 watts from an OPUS (these a approximate, but are a good practice when designing a PC). Also, remember that you could be pulling more current on one rail than it is designed for, and much less on another, still be within 120-135 watts, but the PSU won't last becuase that one rail being stressed will die.

Where did you arrive at this 80-90% value from? Is that just from your experience?

In general you can't just go on a blanket statement about total power drawn. You have to look at each rail independent to the total power draw to see if you are violating anywhere.

I haven't looked at the full Opus spec in awhile but if a supplier says that this product will do this kind of current on these lines given a certain input voltage and a certain temperature then I fully expect their product to do that or else they are lying.

As a consumer should you err on the side of caution? Perhaps. But sometimes that isn't always so easy to do.

**ColdPhreze** · 11-23-2004, 01:33 AM

MrPerfectionest, yes, this is from my professional experience working with power supplies over the years. When you push any device that creates heat to the manufacture's stated limits, components break down at a much faster rate than normal. Power production vs. component breakdown is an exponential curve. At 150 watts, an OPUS is being strained, any more and severe strains occur. That 150watts is it's maximum continous power, which is going to generate more heat, and stress certain components to their maximums. This will *always* lead to a decreased lifetime. If you keep below the maximums, you will prolong the lifetimes of any heat-creating product.

Let me put it this way: Consider an automobile which is designed and rated to operate safely at 6000rpm, and red-lines at 6500rpm. This means it is ok to rev to 6000 rpm, and even up to 6500rpm occasionally. However, does it mean it is ok to constantly run it at 6000rpm? NO! You will blow that engine in a short amount ot time, even if you change the oil and other fluids every day.

I stated that blanket rule, then also stated that you have to look at every rail separatly... Thus driving home that one must consider both total power and individual rails.

Opus isn't lying, their product does output a constant 150 watts. The only thing that wasn't considered or told to those purchasing it, is that it's life expectancy is reduced at that wattage.

Consumers should be better informed... but that is kinda the point of this forum

ColdPhreze

**choyak** · 11-23-2004, 01:42 AM

At my work we make AC-DC-AC converter systems rated more than 60 kilowatts and they are near 90% efficient. The AC-DC is a PFC and the DC-AC is an inverter using IGBTs. I see no reason that DC-DC is at least 90%, depending on the topology. The weirdness to circumvent though is it is either dual stage or flyback. This is necessary because the DC-DC needs to both buck and boost.

**MrPerfectionest** · 11-23-2004, 12:22 PM

MrPerfectionest, yes, this is from my professional experience working with power supplies over the years. When you push any device that creates heat to the manufacture's stated limits, components break down at a much faster rate than normal. Power production vs. component breakdown is an exponential curve. At 150 watts, an OPUS is being strained, any more and severe strains occur. That 150watts is it's maximum continous power, which is going to generate more heat, and stress certain components to their maximums. This will *always* lead to a decreased lifetime. If you keep below the maximums, you will prolong the lifetimes of any heat-creating product.

I know what heat does to components.

I am talking about specifications plain and simple.

Opus states that their device will deliver:
+3.3V: 10A max, 13A pk, 50mV p-p max 2%
+5 V: 10 A max, 13A pk 50mV p-p max 2%
+12 V: 5 A max, 6.5 A pk 50mV p-p max 2%
-12 V: 0.5 A max, 1.2 A pk, 150mV p-p max 10%
5 V standby: 1 A max, 1.2 A pk 50mV p-p max 2%

from -20C to 70C with a MTBF of 150,000 hrs. They also provide a limited 3 yr warranty.

This is their specification and I will live by this. If my application stays within those ratings then I fully expect to be able to turn my opus on and have it run for 17 yrs. This may not be realistic (and I would be interested to see how they arrived at that number) but Opus states they will warrany it for 3 years. So at the least I can expect that or else they replace the product, plain and simple. Thats all there is to it.

Let me put it this way: Consider an automobile which is designed and rated to operate safely at 6000rpm, and red-lines at 6500rpm. This means it is ok to rev to 6000 rpm, and even up to 6500rpm occasionally. However, does it mean it is ok to constantly run it at 6000rpm? NO! You will blow that engine in a short amount ot time, even if you change the oil and other fluids every day.

Your analogy doesn't work at all because when a mfg. produces a car the 'specification' (I use the term loosely here) is 'normal' driving conditions. Normal driving conditions aren't 6000rpms 24hrs a day.

**Ricky327** · 11-23-2004, 12:38 PM

What is the "normal" condition for the OPUS?

**rushnrockt** · 11-23-2004, 12:53 PM

Hey there MrPerfectionest,
Although one would think that the numbers given by a PS manufacturer for each rail should add up, it is not quite the case. You probably noticed that for example regular cheapy PSUs out there rated at 380W cannot compete with say an Antec 300W. The reason is that the cheapy PSU's looked at each rail separate and added up the numbers to get their power rating. In reality, with all rails loaded at the same time, power supply is strained to keep them going, hence the '80%-90%' rule mentioned previously. I am an electrical engineer (granted, only beginning) and as far as I can see, any rating that a product has is quite idealized, and since OPUS doesn't say what kind of load they use, its definitely a great idea to be on the safe side.