Hi frequency = radical voltage fluctuations?

[gonzo0815]

Re: Hi frequency = radical voltage fluctuations?

I would cetainely. . Can`t help me, but FSP has always delivered a very decent psu to me, and that no only at the high price tag.
As long as no OEM will konvince them, they don`t use to crapy shit. At least all my units are very decent. And IMHO all units can emit the stated o/p without exploding.
May be if i have the time i will lock on those paper may be i figure it out, what this secret is. Any way, there is mutch more than only some komponents on a PCB in those PSu desings. And i am shure, that we will not to fast be seeing a >70khz PSu around.
And may be they have had some problems with some psu's, may be a component misplaced or wrong value. As long it won`t make troubles, i think any mfk would have them sold.
But any way. eithe it is the APFC controler ripple, line riple or the regulation point of the forwardconverter and any spike is an phase wich will power the o/p caps.

[Super Nade]

Re: Hi frequency = radical voltage fluctuations?

Gonzo, that was very informative. I'm sorry to bother you earlier, but I couldn't understand certain things you wrote. I realize you are from Germany, so communication may be a bit hard. Atleast your English is better than my Deutsch.

Anyway, back on topic. You are saying the PFC regulation system is dumping noise into the output ? Any idea what kind of IC's are used there?

[jonnyGURU]

Re: Hi frequency = radical voltage fluctuations?

According to Oleg in the review, most PSU's are below 30kHz... that's why I was thinking the sampling frequency on the scope may be perhaps too low for this particular PSU. Then again PeteS knows a lot more about the engineering side of these than I do.

Here's the quote from Xbit:



http://www.xbitlabs.com/articles/oth...roundup_7.html

I think below 50kHz would be unorthodox and certainly wouldn't explain the smaller components. To my knowledge, most are at or around 50kHz.

Undersized filtering caps would cause explain the o-scope, but I just can't believe that with an FSP.

A side effect of the APFC? Ok. I'll bite. I just don't know how that works.

EDIT: For the record; the O-scope is not working off of probes. There are BNC outputs on the load tester. The O-scope is really just working as a data logger. The load tester is feeding it actual voltage readings at very finite increments. By changing the time delay on the O-scope, I'm only smoothing out the line so it's easy to see. It shouldn't be picking up any more than that... but of course, anything is possible.

[Oklahoma Wolf]

Re: Hi frequency = radical voltage fluctuations?

Undersized filtering caps would cause explain the o-scope, but I just can't believe that with an FSP.

I felt a bit let down seeing the size of those caps after the monster 6800uf caps in the 530W. They must have had a good reason though... about all I can suggest now is to try and get a hold of one of FSP's engineers somehow and ask them what's up.

[larrymoencurly]

Re: Hi frequency = radical voltage fluctuations?

. I can see using a higher frequency in an effort to use smaller components, but if the frequency is the same as any other PSU on the market, and the components are smaller, and the heatsinks are smaller... then I'm not in the mood to conclude this is a decent power supply. Would you?

Delta and maybe Newton use higher frequencies, around 100 KHz, but don't seem to have problem with them. Also their transformers and capacitors are no smaller than than those found in PSUs with similar power and current ratings but that run at 60 KHz or less. The transformers are actually slightly larger, except compared to those in the older Fortrons that run at 40 KHz.

[PeteS in CA]

Re: Hi frequency = radical voltage fluctuations?

Pete, how would fan noise couple back into the system? As I understand it, there are seperate analog and digital ground's which are tied together. So there should be no ground loops per se. However, RF pickup can occour via any pointy surface, so at times the clips themselves may be the noise source.

My understanding is that johnny is speaking of noise on the P/S rails. If this is the case, and if current from a 12V fan (internal or external) O/P is returned in such a way as to affect the +5V O/P voltage sensed by the regulator, noise due to the fan current will appear on the +5V O/P.

The ~340VDC produced by active PFC is regulated, but the regulator has a very slow control loop, so there is substantial AC-line frequency-related ripple on the ~340VDC. The main O/P regulator is supposed to take care of the 100Hz/120Hz ripple, but if its amplitude is high enough or the main loop is slow enough, you'll still see the AC-line frequency-related ripple. The w/fs in johnny's post of "Yesterday, 03:20 PM" look like there is a noise component with a period on the order of 8.0-8.5 mS; 1 / 120Hz = 8.33 mS. Hence my question about sync'ing using "Line" as the trigger source.

[jonnyGURU]

Re: Hi frequency = radical voltage fluctuations?

Hence my question about sync'ing using "Line" as the trigger source.

Line is the trigger source. Same thing.

The voltages are literally bouncing up and down at a fascinatingly fast rate. 11.9 12.0 12.1 12.2 12.1 12.0 11.9 12.0 12.1 12.2 12.1 12.0 11.9...... every .2ms or so.

[Oklahoma Wolf]

Re: Hi frequency = radical voltage fluctuations?

Another suggestion - since there's a chance fan noise could be an issue, maybe run one of these with the lid off and the fan unplugged during test 1 or some other low load level and see what the scope says.

[Super Nade]

Re: Hi frequency = radical voltage fluctuations?

My understanding is that johnny is speaking of noise on the P/S rails. If this is the case, and if current from a 12V fan (internal or external) O/P is returned in such a way as to affect the +5V O/P voltage sensed by the regulator, noise due to the fan current will appear on the +5V O/P.

The ~340VDC produced by active PFC is regulated, but the regulator has a very slow control loop, so there is substantial AC-line frequency-related ripple on the ~340VDC. The main O/P regulator is supposed to take care of the 100Hz/120Hz ripple, but if its amplitude is high enough or the main loop is slow enough, you'll still see the AC-line frequency-related ripple. The w/fs in johnny's post of "Yesterday, 03:20 PM" look like there is a noise component with a period on the order of 8.0-8.5 mS; 1 / 120Hz = 8.33 mS. Hence my question about sync'ing using "Line" as the trigger source.

Thanks for the input Pete. So you are essentially saying what he is seeing is a higher order harmonic of 60Hz? So why is he seeing the same effects on the 5V line, if its a 12V fan issue?

[PeteS in CA]

Re: Hi frequency = radical voltage fluctuations?

I was tossing out multiple ideas, kind of a usual suspects list; maybe some cookies got tossed, too. With a 60Hz line and full-wave rectification, the ripple frequency is 120Hz (50Hz and 100Hz in Europe).