Film capacitor as power-supply filter

The 'need equtions' is the reason you want to measure past the rated voltage; there's not much validity to an equation if there are singularities just outside the measured range (because, for instance, any polynomial fails to handle a singularity).

When you apply the capacitor, it's sensible to stick to the range the manufacturer recommends (that's the way the manufacturer and user can coordinate), but NOT for the purpose of information-gathering.

MOS devices get damaged quickly outside their recommended range, but not usually capacitors. If in doubt, overvoltage some ceramics and test 'em for changes. I've (carefully) overvoltaged electrolytics to bring leakage down after storage; it never failed.

The issue was series strings of electrolytic caps, where the total supply voltage is more than the rated voltage of the caps. Film caps can blow up in that situation. What do lytics do?

Answer: their IV curves make them safely self-equalize.

Post a link of leakage past rated voltage. Real data, not faked cartoons.

You can compare your data

Since you probably don't design electronics, it is meaningless to you.

How would that be different? You'd get the same data points, just slower.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

He argues out of emotion rather than reason. I have several anti-fans here who are dying to show me wrong, and will commit any bogus mental contortion in that cause.

This is amusing, because I'm really interested in how people reason toward truth, and especially how they don't.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

Standard mosfets generally die at gate voltages around 70ish, maybe 5x rated abs max. The self-protecting ones zener at maybe 44 volts on the gate.

Most mosfets will avalanche at high drain voltages, maybe 1.5 or so times abs max, and are then damaged by excess dissipation. Some just die without avalanching.

The EPC GaN fets die without warning at a bit over 2x max drain voltage and have more complex gate voltage behavior.

The Cree SiC fets avalanche at around 1.4x rated drain voltage, and like the mosfets just get hot. You can kill them with a modest gate over-drive, which is unfortunate because they need close to abs max gate drive to switch well.

Ceramics are usually happy at several, sometimes ten or twenty, times rated voltage. But they tend to run out of capacitance.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

--------------------------------------

** You mean, just like you do ?

** I *do* know the feeling ...

Because I go hard against all the fools & trolls on this and other NGs, I get the same malicious treatment.

** Same interest here - the sheer, bloody irrationality of most people is STAGGERING !

The fact was driven home to me forcefully soon as I began posting on usenet, about 20 years ago. People make up their minds about something in a flash, using great gobs of false logic plus "intuition" - then will not back down at any price.

That so many seemingly bright people go right through college and university WITHOUT learning clear thinking or how to spot and avoid logical fallacies is a crime.

I could go on and on ...

.... Phil

Playing with twits doesn't count. That's just sport.

Electronics is pretty check-able, so emotional delusions don't get very far.

Let's be careful here; we are in dire danger of agreeing on something.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

Excel is my least favorite program ever... the graphs are particularly bad.. but the rest too.

Sure but I liked python.. it's interpreted like basic, I really like that when for looking for my mistakes.

George H.

I just want to say, that when people tell me *not* to measure parts above and beyond the specs.. The more I want too. :^)

I've had 36V opamps running up around 48V for a while... many minutes.

How do you test some power supply but to load it and see how it fails*

George H.

*I'm saying a little thank you to all the parts gave up theirs lives so I might know their limits.

--------------------

Some retard posted:

** Test 'em to destruction I say ...

Just kidding, but current limited breakdown testing is simply the only way to do find out the actual limit of many parts. Carried out sensibly, it does no damage.

Anecdote:

I once purchased a quantity of MJ15030/31s from a popular components retailer in Sydney. These are medium power TO220 pak devices rated at 160V for use as output drivers in power amplifiers.

Nearly all of them were *dead short* as purchased !!

I got a very grumpy reaction when I returned them and refused to take more from the same bin. WTF - Motorola do not supply dead BJTs.

I smelt a rat, someone had been at them before me.

Turned out a local amplifier maker ( Chris from PTM Electronics ) "borrowed" hundreds of them from the same store to put through his quality checking process then returned any he did not like.

His "process" involved the use of an old HP Curve Tracer, which is well capable of destroying such devices and had done so to a great many.

Wot an asshole.

..... Phil

As if John Larkin doesn't.

But is unwilling to study his own behaviour in that context.

Any train of thought that suggest that John Larkin is less than perfect gets ruthlessly repressed.

--
Bill Sloman, Sydney

Sadly, the prize example around here got a university education - admittedly at Tulane - and posts denialist propaganda about anthropogenic global warming whenever he posts on the subject.

This displays a massive failure in critical thinking. His vanity prevents him from recognising this, and commits him to total faith in every last silly idea that Anthony Watts puts on his web-site.

--
Bill Sloman, Sydney

Huh, I mostly buy from digikey, (newark/mouser/..) I got some crap 79l12 (to-93 pack) voltage regs from jameco ~20 years ago, and never more.

Good vendors and good customers, both should be cherished.

George h.

---------------------

** This was quite a while ago, about 1985.

Companies like Farnell / Newark etc had not set up business in Australia then and getting trustworthy semis in small quantities was a regular hassle.

Besides the damaged MJs, I got any number of Motorola fakes from well known outlets about that same time - mostly MJ15003/4 types from Dick Smith Electronics, remember the Aussie helicopter aviator ?

I always got my money back and then did my level best to expose the scumbags who were still openly selling them.

I received nasty lawyers letters and criminal threats for doing this on a local electronics forum.

..... Phil

Unless a part is very expensive, may as well test it to destruction.

With some parts, the first indication of impending breakdown is failure.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

-----------------------------------------

** I have a TO3 lateral MOSFET with a neat, round hole in the top of the lid.

Not the only example I have seen.

Just below the hole is the top of the drain pin, somewhat burnt.

..... Phil

Except for its price, no. I use 50uF/900V for the same purpose. But then it pays off to go to a much higher bus voltage with your PFC unit -- stored energy is roportional to V^2. The data sheet says that at 600 its useful life is expected to be 1e6 hours.

Best regards, Piotr

-------------------

** Even that is NOT an issue.

Compared to two, good quality, long life electros.

** $7 versus $36.

.... Phil

Be careful doing that with electrolytics. The process of generating Al2O3 gives off hydrogen gas:

2Al + 3H2O --> Al2O3 + 3H2 (Gas) + 3e

At high rates this can exceed the capacity of the capacitor to reabsorb and the hydrogen is released outside the capacitor. If the cap is in an enclosed space, a dangerous buildup of hydrogen gas can provide the basis for an explosion.

A second problem is high current can cause heating which can boil the water in the electrolyte. The buildup of steam can rupture the case and result in an explosion.

I had the unfortunate experience of an electrolytic explosion once. The cap was failing but I didn't know about it since the unit was in its case. When the cap blew, it left a dent in the 1/16 inch lid that clearly outlined the top of the capacitor. The inside of the unit was a mess of electrolyte and shredded aluminum foil. This was in the old days when the electrolyte was liquid and would slosh around when shaken. But don't underestimate the power of a steam explosion, and beware of caps that start to get hot.

I agree, same conclusion on my end. Other parameters are stellar as well.

Best regards, Piotr