1000 whats!

[goodpsusearch]

Re: 1000 whats!

If you guys REALLY want to have a discussion about skimpy heatsinks, look at some of sirtec/High Power's and FSP's offerings. Even so, most of those units do just fine.

About tiny heatsinks:

650Watt

400Watt

[PCBONEZ]

Re: 1000 whats!

See what I mean...

[Rulycat]

Re: 1000 whats!

I think it's hard to compare an old inefficient design with a more modern design. As it becomes more efficient it's natural they'll give it smaller heatsinks.

[Pyr0Beast]

Re: 1000 whats!

Modern design -> more savings on material )

[370forlife]

Re: 1000 whats!

The ATNG in question shows about the same or better efficiency as the FSP GLN series. Both use two transistor forward.

[goodpsusearch]

Re: 1000 whats!

The DR-8400BTX uses 2x13007 in a half bridge design.

Usually they blow between 250-300Watt.

[Trinite]

Re: 1000 whats!

See what I mean...

I do now haha. When he starts refuting the validity of established mathematical principles, you have to wonder

[Th3_uN1Qu3]

Re: 1000 whats!

I'm sorry but PCBONEZ is right on this one. Half the current = half the voltage drop = half the heating. Period. Both simulations and real-world tests confirm this.

[lifthanger]

Re: 1000 whats!

Hi! This is my first post.
Really love this site and don't want to threadjack.
At the moment I don't fully understand this diode problem, so I'd like to write what I understand so far and maybe I could get some feedback.

Say for a 1n4001 at 25C which starts conducting at about 0.7V.

At 0.4A the drop of the diode would be 0.85V which would give a loss of: 1.4*0.95W= 0.34W

Two in parallel would get 0.2A each at 0.8V which would equal 2*0.2*0.8W = 0.32W.

60% could be possible with a diode with the right characteristics. Is that what this is about, or is my math wrong somewhere?

Thanks.

[PCBONEZ]

Re: 1000 whats!

The curve you are probably looking at is based on a constant Junction Temperature which isn't going to be true in a real circuit.
That curve defines design LIMITS [to prevent overheating the part].
- It is not stating operating CHARACTERISTICS as some are interpreting it.
.
The Junction Temperatures will go down which multiplies the reduction in heat dissipation to the point that two diodes in parallel need much less heat-sink than a single diode.
As I recall [from some thermal design discussion in an application guide or data sheet] they'll need 30-40% less heat-sink.
.
To correctly do the math you would need VxA curves for each Tj and most data sheets don't have that.
.
I did the research before after finding a data sheet with ALL the necessary curves and it's posted in another thread.
I don't currently have time [or the interest] to do it again.
.

[lifthanger]

Re: 1000 whats!

The curve you are probably looking at is based on a constant Junction Temperature which isn't going to be true in a real circuit.
That curve defines design LIMITS [to prevent overheating the part].
- It is not stating operating CHARACTERISTICS as some are interpreting it.
.
The Junction Temperatures will go down which multiplies the reduction in heat dissipation to the point that two diodes in parallel need much less heat-sink than a single diode.
As I recall [from some thermal design discussion in an application guide or data sheet] they'll need 30-40% less heat-sink.
.
To correctly do the math you would need VxA curves for each Tj and most data sheets don't have that.
.
I did the research before after finding a data sheet with ALL the necessary curves and it's posted in another thread.
I don't currently have time [or the interest] to do it again.
.

yeah the curve was for a constant T. Actually this explanation is more than enough, thank you! This explains why I couldn't get much better dissipation with multisim. You can run 40A through a 1N4001 without a sweat in multisim. Obviously temperature is ignored there.

[Th3_uN1Qu3]

Re: 1000 whats!

You can run 40A through a 1N4001 without a sweat in multisim. Obviously temperature is ignored there.

You can do that with any simulation program. It's the designer's job to confirm that the parts he uses are adequate.

[Pyr0Beast]

Re: 1000 whats!

I do now haha. When he starts refuting the validity of established mathematical principles, you have to wonder

I NEVER refuted the validity of any mathematical principles. I merely questioned your methods of calculation and observation.

Yes. You have to wonder, and more importantly, ask yourself, If your methods of observation are correct. They are not, as I have pointed out before.

I'm sorry but PCBONEZ is right on this one. Half the current = half the voltage drop = half the heating. Period. Both simulations and real-world tests confirm this.

You are not sorry and are just as wrong as he is. Period.

Both simulations and real-world ? Are you bullshiting me ?!?
Show me parameters of simulation.
Show me real-world test data!

The curve you are probably looking at is based on a constant Junction Temperature which isn't going to be true in a real circuit.

it is based on constant Junction temperature because that is the only way to compare data on two-dimensional chart.

That curve defines design LIMITS [to prevent overheating the part].

Um what ?

That curve (forward voltage vs. current) does not even touch design limits. You have rectified current vs. ambient temperature derating curve for that.

- It is not stating operating CHARACTERISTICS as some are interpreting it.

No ? Then what it is stating ? Operating characteristics if such conditions are met.

The Junction Temperatures will go down which multiplies the reduction in heat dissipation to the point that two diodes in parallel need much less heat-sink than a single diode.

Nah. Now you are just clutching at last straws and twisting the thread so it suits you better.

I don't currently have time [or the interest] to do it again.

Are you telling me I should find the data to back up YOUR statements ? ....

You can run 40A through a 1N4001 without a sweat in multisim.

Because multisim uses static diode data if you don't state otherwise.

[PCBONEZ]

Re: 1000 whats!

Can one of the mods please check if this guy's IP is the same as i4004 ?
Thanks.

[Pyr0Beast]

Re: 1000 whats!

It is not. I can tell you that already.

[ratdude747]

Re: 1000 whats!

WTF happened to everell's (and in a way, my) thread?

i guess we all know where wwIII is starting... right here!

could you two move the war elsewhere? my rig will not pull even close to 950w... closer to 400w max at current config. for now it is a moot point.

[Pyr0Beast]

Re: 1000 whats!

WTF happened to everell's (and in a way, my) thread?

Hijacked

[PCBONEZ]

Re: 1000 whats!

WTF happened to everell's (and in a way, my) thread?

i guess we all know where wwIII is starting... right here!

could you two move the war elsewhere? my rig will not pull even close to 950w... closer to 400w max at current config. for now it is a moot point.

The discussion is about how it can get away with small heat-sinks.
Whether you like it or not that's on topic.
.

[everell]

Re: 1000 whats!

Where is i4004??? I would like to hear his side of the argument!

Thread hijacked??? I think this is a GREAT discussion on an important subject for high power power supplies.

Is 950 watt power supply too much for a 400 watt computer. Perhaps there are other adverse effects. Heat may or may not be one of them.

[370forlife]

Re: 1000 whats!

Good luck pulling 400W from that computer. It will probably have a hard time hitting 250W.