HS gate drive transformer?

Not really, just make sure that the bootstrap voltage remains 10V or so above the source at all times.

Sound about normal.

If you want to go opto you'd probably be better off with John's suggestion. Get a fast but run-of-the-mills weak optocoupler, then follow it with a staunch MIC4421 or some other driver for a little over a buck.

The fancy chips will always be expensive because us guys never use them in product designs. We only would if they'd be cheap and 2nd-sourced, sort of the chicken and egg problem.

Yep they defiantly aren't giving the battery option away.

I haven't given up yet I'll play around with what I have part wise and see if I cant get something reliable.

No not confidential I haven't made up a full schematic yet. :-)

Here's my actual test schematic. I'm not showing Bypass caps and the lm317 for the driver and the 78l05 for the PIC both regulators get their input from the 20 V supply V1.

That is just a test set-up to test the high side drive for a active clamp flyback shown below.

I don't have a schematic for the flyback because I just started considering it yesterday. I'm just working out how to drive the High-side FET.

A two amp driver should take care of that. I've just been using a spreadsheet from On semi for rough estimates for now.

They all do that it seems worse now because of the high 100 plus amps they also quote for the part.

Another old trick is to use a car battery and inverter. Mine just croaked. Couldn't believe it, half a year ago it was showing slight signs of weakness but would still crank a 2.6l gasoline engine alright. So I replaced the one in the car. When I needed it for isolation purposes a month ago ... nada, zip, zilch. It was totally hi-Z, charger went to 17V and shut off, and the battery wouldn't even light a 1W bulb. Puzzling how it could have gone so fast.

Try to find some smaller ones, maybe from EMC filters :-)

Since it can't bang past either rail you cold probably bootstrap that. But transformers are a good option here, just not with 0.1uF in series.

No chance just to do a half-bridge and be done with it? It would also be a bit easier EMI-wise. And no air gap.

Yes, 2A would be plenty.

The topper is what I saw in some discount store aisle. An audio amplifier in a blister pack, very ritzy packaging. It claimed 1000 (!) watts PMPO and the power supply was a wall wart. Yeah, right ...

Yea I'm digging through my parts. I tried a 10 nf and the oscillations weren't as bad but my Vgs decreased by about a volt. I'll try some other values. I don't think I can go below 10nf without adjusting the inductance though.

That's my next PSU project;-). Coil Craft was kind enough to give me some samples of flyback transformers. I used up all the small 10W ones on projects but I still have some of the bigger ones left.

Haven't you heard the Chinese can stick a small reactor in a wall wart enclosure. That's not the really amazing part though ,they can do it for $1.00 or less depending on quantities. ;-)

There's also something like the ADuM6132,- supply,isolation and driver in one.

-Lasse

On a sunny day (Fri, 23 Apr 2010 14:13:56 -0700 (PDT)) it happened " snipped-for-privacy@fonz.dk" wrote in :

That is very nice, and not even expensive.

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Sounds like electrolyte dry out. See if you can find a way to "juice" the cells again.

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Oh yes, I remember Peak Meaningless Pretend Output from the 1960s. A play value created by inventive misapplication of theory that cannot be duplicated in the real world. And look at the thin cord that carries it from the wall wart to the device, better than room temperature superconductors it must be.

Strange thing is, the fluid level inside is ok. It's one of those supposedly maintenance-free ones but one can pry off the lid assembly to peek inside.

Why is it that this brand name battery is dead after 5-6 years, the gel cell in my StatPower emergency kit also died after 5-6 years, while the gel cell in my over 10 year old big $10 Chinese flashlamp is still fine?

They probably rely on the fact that the majority of shoppers does not have an engineering degree :-)

Sulphation, do the plates look white? High impedance batteries due to sulphation can be recovered, hardly worth the effort though as the success rate has been reported as low as 30%. Leave it at 17V for a long time, or get one of those pulse/spike units that are supposed to break down the sulphate.

Car batteries often are used in a chronically undercharged state due to short trips, and if you happen to have a regulator at low end of the loose spec auto range.

Since you took the lid off, try adding some battery restorer? Try some phosphoric acid -- some web searching will hint at the dosage. I've only read about this acid, not tried it.

Poor charging techniques, old fashioned charging regimes that didn't get updated with the newer battery technology?

Grant.

They look the usual dull silvery color. But the battery does slightly bulge at both ends so you may be right, there could be sulphation further down inside of the cells.

I think I'll give it to the recyclers. But it may have to wait until I buy a replacement. Because there is a high tax on batteries in California and you only get it back if you hand over the old one. If you just bring a battery without buying a new one that refund is lost. I made that mistake once.

Has the technology change that much on car batteries?

...

Not a lot, calcium and silver additives? But the car has changed heaps, more standby loads but still the crappy 13.5V to 14.5V or so constant voltage charging regime that usually under or over charges the poor battery. Short trips like the high voltage, long trips the low -- then there's battery temperature compensation done by ambient but rarely at the battery. Sloppy, battery will last the warranty period...

Grant.

Mine's a run-of-the-mills battery, maybe Sam's Club. The car is also a rather mundane SUV. Since I do not trust electronics in cars much I purposely bought a vehicle that has no electric this, that and the other thing. No power windows, not even central-lock.

In reality, a burst controller would be 'bursting' at a minimal duty cycle - not as is programed in your PIC here.

This is more a power-limit/hiccup type of simulation; the symptoms at the gate drive will be similar, but are unlikely to repeat as frequently.

To avoid backswing effects on discontinuous drive trains; C1 must not be large enough to support saturating voltseconds. Reduce C2 to ~ 10xCgs. Reduce Rgs to produce 30% gate voltage droop under full load low line conditions. Tailor D2 characteristics (as ~ back to back zeners) for a few voltes of 'off' bias.

For lowest power loss in bipolar ouput drive circuits, schottkies should be applied from drive output to both rails, to recover mag energy. Rc is probably mislocated here.

RL

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While i am not young i had not yet celebrated my 15th birthday when i recognized that crap (mid 1960s). OTOH i had been building electronic kits for years by then.