Capacitors for DC smoothing, Low-ESR or not Low-ESR?

[Pyr0Beast]

Re: Capacitors for DC smoothing, Low-ESR or not Low-ESR?


That's because most people don't know what 'Endurance" aka Endurance Lifetime" aka "Load Life" aka "Lifetime"[in a data sheet] means.

Then state the difference and clear this up once and for all.

There are 8760 hours in one year.
- According to you, 5000 hour rated caps die in 208 days of 24/7 use.

Pretty much. Out of spec = Unreliable application = Faliure


There is a formula to estimate Useful Lifetime from Endurance Life but according to Chemicon [I think it was] that equation only has a 40% Level of Confidence.
Good enough. With some derating you stay on the safe side.

[PCBONEZ]

Re: Capacitors for DC smoothing, Low-ESR or not Low-ESR?

The test for Endurance Lifetime is defined in IEC 60384-4. [An International Standard].
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None of the other Lifetime terms have standardized definitions so basically they can mean whatever the manufacturer wants them to mean and they can 'come up with' equations and tests to fill the numbers their charts any way they want to.
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As with most Standards if you want a copy you have to buy it. I don't have time to find a link to someone that cheated and posted a copy today. But if you can find such a link please pass it on.
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Basically they put the cap at max Ripple [@rated frequency, usually 100kHz], max DC volts and max rated temp for 'x-many' hours then return it to nominal temp and check that all it's specs are in tolerance. They do this for various 'x-many' hours and the longest 'x-many' hours where the cap does not go out of spec becomes the Endurance Lifetime. [That test tells you absolutely nothing about how long the cap will last in a real world application.]
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In case you haven't noticed all the caps in a series have the same number for a given diameter and that number is always a nice round number like 2000 or 4000.
[If it was a spot-on number you'd see numbers like 1967, 3985, 2311, etc...]
There are two reasons.
- They take the worst case and apply it to the whole series.
- The test is inherently inaccurate so they round the result down big time to cover their corporate asses.
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[Pyr0Beast]

Re: Capacitors for DC smoothing, Low-ESR or not Low-ESR?

None of the other Lifetime terms have standardized definitions so basically they can mean whatever the manufacturer wants them to mean and they can 'come up with' equations and tests to fill the numbers their charts any way they want to.
So all is just shit ?
If we can't keep standards same then whole specs are just garbage.

- They take the worst case and apply it to the whole series.
I doubt they do that because then they would be worse than competitors.

I'd go with rounding for the sake of ease, they for the sake of more profit.

[PCBONEZ]

Re: Capacitors for DC smoothing, Low-ESR or not Low-ESR?

There are 8760 hours in one year.
- According to you, 5000 hour rated caps die in 208 days of 24/7 use.

Pretty much. Out of spec = Unreliable application = Faliure.

And therefore according to you Rubycon MBZ and MCZ (both 2000hr caps) are only good for 83 days of 24/7 operation.

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[Pyr0Beast]

Re: Capacitors for DC smoothing, Low-ESR or not Low-ESR?

And therefore according to you Rubycon MBZ and MCZ (both 2000hr caps) are only good for 83 days of 24/7 operation.

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At rated temperature, ripple and voltage, yes. Derate and you get more, cool and it will last longer.

[PCBONEZ]

Re: Capacitors for DC smoothing, Low-ESR or not Low-ESR?

None of the other Lifetime terms have standardized definitions so basically they can mean whatever the manufacturer wants them to mean and they can 'come up with' equations and tests to fill the numbers their charts any way they want to.
So all is just shit ?
If we can't keep standards same then whole specs are just garbage.

EXACTLY! - It's all marketing BS.

The terms 'low ESR', 'very low ESR', 'ultra low ESR' also have no standard definitions.

Don't remember who but I saw an el'cheapo cap brand calling one of their series 'ultra low ESR' but when I looked at the specs the ESR was higher than Panny FC.
It was just -THEIR- lowest ESR cap so they gave it the grandest name.
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[PCBONEZ]

Re: Capacitors for DC smoothing, Low-ESR or not Low-ESR?

At rated temperature, ripple and voltage, yes. Derate and you get more, cool and it will last longer.

But you are derating an -estimated- number by factors that have -estimated- effects.

Estimated numbers all have a +/- range even if they aren't written that way.

When you put a whole bunch of +/- ranges into an equation the end result is a number with a BIG HUGE +/- range.

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[Pyr0Beast]

Re: Capacitors for DC smoothing, Low-ESR or not Low-ESR?

EXACTLY! - It's all marketing BS.

The terms 'low ESR', 'very low ESR', 'ultra low ESR' also have no standard definitions.

Don't remember who but I saw an el'cheapo cap brand calling one of their series 'ultra low ESR' but when I looked at the specs the ESR was higher than Panny FC.
It was just -THEIR- lowest ESR cap so they gave it the grandest name.
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Haha. Well. It is same with transistor power rating. 125°C junction temperature, you got to be joking me.
Couldn't meet the specs even when cooled with liquid nitrogen


The terms 'low ESR', 'very low ESR', 'ultra low ESR' also have no standard definitions.
Well, I have my own to make some sense from all the rubbish. ULESR are usually really good polys or ceramic. Low esr anything that doesn't reach into ohms range.

[Pyr0Beast]

Re: Capacitors for DC smoothing, Low-ESR or not Low-ESR?

But you are derating an -estimated- number by factors that have -estimated- effects.

Estimated numbers all have a +/- range even if they aren't written that way.

When you put a whole bunch of +/- ranges into an equation the end result is a number with a BIG HUGE +/- range.

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Yes. Shitty metology to do so. Garbage in, garbage out.

[Radio Fox]

Re: Capacitors for DC smoothing, Low-ESR or not Low-ESR?

Excuse me, there is a slight error in the calculation. The DC voltage is the peak AC voltage (9V x 1.414) less the voltage drop of two diodes (1.2V) = 11.53 volts. Doing the calculation in reverse order (as you did) results in predicting the output voltage .5 V lower than what it will actually be.

PlainBill

Whops, you're absolutely correct.

[Th3_uN1Qu3]

Re: Capacitors for DC smoothing, Low-ESR or not Low-ESR?

Haha. Well. It is same with transistor power rating. 125°C junction temperature, you got to be joking me.
Couldn't meet the specs even when cooled with liquid nitrogen

Actually transistors do take that temperature. Ever did any thermal calculations that take the junction to case thermal resistance of the transistor into account? You'll quickly see the numbers soar to mind-numbing values. Especially true in power supplies where they use those insulating pads to prevent heatsinks from becoming live - the transistor runs LOTS hotter than the heatsink.

I did a test on some MOSFETs with 175C junction temperature (IRF530) and they were still working at 175C heatsink temperature. The transistors were bolted directly onto the heatsink and thermal paste was used, but there was still the internal junction-to-case resistance so the silicon itself was running at 200-something degrees. Sure, this was a short-term overload test (about 2 minutes) but it definitely shows that they do take the incredibly high temperatures mentioned in the datasheet.

[Pyr0Beast]

Re: Capacitors for DC smoothing, Low-ESR or not Low-ESR?

Mmmm yeah. These things can unsolder themselves from the board and still work.

But I wouldn't rely on that. 100°C Tj is way too much for me.

[PCBONEZ]

Re: Capacitors for DC smoothing, Low-ESR or not Low-ESR?

Actually transistors do take that temperature. Ever did any thermal calculations that take the junction to case thermal resistance of the transistor into account? You'll quickly see the numbers soar to mind-numbing values. Especially true in power supplies where they use those insulating pads to prevent heatsinks from becoming live - the transistor runs LOTS hotter than the heatsink.

I did a test on some MOSFETs with 175C junction temperature (IRF530) and they were still working at 175C heatsink temperature. The transistors were bolted directly onto the heatsink and thermal paste was used, but there was still the internal junction-to-case resistance so the silicon itself was running at 200-something degrees. Sure, this was a short-term overload test (about 2 minutes) but it definitely shows that they do take the incredibly high temperatures mentioned in the datasheet.

[Th3_uN1Qu3]

Re: Capacitors for DC smoothing, Low-ESR or not Low-ESR?

I already had the datasheet, thank you. But my IRF530s aren't made by Fairchild, here you go, and it explicitly says 175C operating temperature there.

[PCBONEZ]

Re: Capacitors for DC smoothing, Low-ESR or not Low-ESR?

And as the graphs clearly show as Tj goes up current goes down so it's debatable that you overloaded them.
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[Agent24]

Re: Capacitors for DC smoothing, Low-ESR or not Low-ESR?

I have sad news. My RTA1320 won't get an internet connection at all now

Worked fine for a few days after recap, but now, I can't get PPP authentication at all.

It powers up fine, gets full speed ADSL sync fine, but the PPP light never comes on and it refuses to get a WAN IP address.

I've tried resetting through the Web interface and also the button, but it just refuses to work. My other router (Thomson ST536v6) works just fine though. I just don't like to use it as I hate the web interface, and it's buggy, won't let me change the DHCP settings, and the Telecom custom firmware locks you out of anything to do with ADSL settings.

Anyone got any ideas or have I screwed something up royally?

[Agent24]

Re: Capacitors for DC smoothing, Low-ESR or not Low-ESR?

Well, this is interesting.

Since I had tried everything else I could, I decided to reflash the firmware on the off-chance that it might help..... and it did!

After a reflash and full reconfiguration it's working again.


Coincidence? Or is something sinister going on here?
(enter into conspiracy theories of badly soldered capacitors causing bad ripple suppression leading to partial EEPROM corruption)

Probably not, right? I'm pretty sure I did a good soldering job, anyway.

[Pyr0Beast]

Re: Capacitors for DC smoothing, Low-ESR or not Low-ESR?

Eeprom corruption is doubtful, I would go with flash corruption rather. But it might be something that was caused by rapid shut-down or poor power supply.

[Agent24]

Re: Capacitors for DC smoothing, Low-ESR or not Low-ESR?

Configuration corruption I thought would be ruled out by the original reset using the button?

As said before, the power adapter is just a 9v AC transformer. Crappy enough?

Wish I had an oscilloscope....

[Pyr0Beast]

Re: Capacitors for DC smoothing, Low-ESR or not Low-ESR?

Nah. Some reset buttons are soft-reset and won't work unless router boots up.

Some other network stuff just uses different combo for reset. It was pain resetting mine. Kind of disabled DHCP and couldn't re-enable it and 192xxx didn't work.
No way of reset work but holding reset on 'warmed up' router, then unplugging from power and holding reset for next 5 minutes.