Author Topic: Ideal bridge rectifier  (Read 1001 times)

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Offline lighthunter

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Ideal bridge rectifier
« on: October 08, 2016, 10:04:19 PM »
Anyone tired of loosing 80+ watts in their wind pma rectifier?
Linear technologies has now put a FET driver in a chip that replaces.
the typical diode bridge for extremely high efficiency rectification.

 The LT®4320/LT4320-1 are ideal diode bridge controllers that drive four N- channel MOSFETs,

two versions of it one for 0-60 hz and the other for 60-600hz.
appears to auto-track the frequency, i hope  :).  Ive seen these for
smps applications but are quite complex. This is a standalone version.
that connects to the gates of 4 fets and 2 dc leads and 2 ac leads, thats it!!!
the rest is done for you, ok im a little lazy.
ebay prices are way high though, you can get them right from the manufacturer.
for $6 vs ebay for $20. Might even be time.
to update my battery charger....car alternator, quite a.
few applications for that one!

LH
LH

Offline eraser3000

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Re: Ideal bridge rectifier
« Reply #1 on: October 08, 2016, 11:10:22 PM »
Very cool, do you have any on the bench yet?

Offline lighthunter

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Re: Ideal bridge rectifier
« Reply #2 on: October 09, 2016, 06:07:26 PM »
No I dont! I will order some monday. I am in need of a 48v charger for a large forklift bat.
remote located from my other equipment and since i dont trust pj inverters for charging.
I was looking to build an equivalent circuit for efficiency. Knowing i needed.
a synchronous rectifier to match efficiency i started looking for a.
simple way. I am anxious to see how well it works. I wont be able to throttle.
charge current unless I add some other tricks but i hope i wont need it. I will
post to let you know how it worked out.

LH
LH

Offline MadScientist267

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Re: Ideal bridge rectifier
« Reply #3 on: October 11, 2016, 05:37:54 AM »

Ive seen these for smps applications but are quite complex.

LH

It's funny you mention this, I was just commenting in IRC about the bridge in my new charger design now being the hottest part (it's plenty sunk)...

I know of a simple way that's basically self-excited synchronous rectification... tho I don't know how (presumably) 3 phase might make things all kinds of screwy. The problem with MOSFETs and AC is... well... both LOL

I have a sync rectifier board here tho that really isn't anything more than what I'll call a "pair" of MOSFETs (2 paralleling arrays of them to increase current capability) driven by a pair of totem poles that cross over each other... there's no control chip whatsoever for it, and it connects to a single coil (no CT)... It *is* a little unusual but only in the sense that it's set up to "catch a forwarder", but a pair of Schottkies works the same way, just with the expected losses. There's an auxiliary supply feed but it's only the excitation for the totem poles for driving the gates (Vcc)... I'm sure it could very easily be turned into each half of a bridge with a little thought.

Or was that the part you were avoiding? :P

Guess I should point out that I haven't done it yet with the design I'm working with right now because the bridge I'm referring to is right at the front of the line to feed a PFC boost converter... a little hairier with (relatively speaking) higher voltages... but at low speeds and voltages like that, I can think of a handful of ways to drive the MOSFETs, none of them all that complex... Just wasn't until after I really started throwing the rocks at it that I realized where most of the heat had gone to with mine, and went looking around at various schemes.

That said, the finals way at the other end (low voltage) are still standard Schottky because of the fun in getting sync rectification to work efficiently at the switching speeds that it's running at, combined with non trivial current using what I've got at hand... (the sync board is toast because of way over the top abuse lol)

But just wandering back and forth in 2 or 3, even 4 digit Hz range at lower voltages following a sine? Naaaa...

For what that's worth... ;D

With all that laid down on the table, I'll be curious to see what all you come up with... Likewise I can think of a few places to put them to good use. ;)

Steve
Wanted: Schrödinger's cat, dead and alive.

Offline Solarnewbee

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Re: Ideal bridge rectifier
« Reply #4 on: October 12, 2016, 01:48:11 PM »
mine is a 3-phase pmg generator. anything out there for my situation?

SN
SN

Any day above ground is a day for potential mishaps

Offline lighthunter

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Re: Ideal bridge rectifier
« Reply #5 on: October 12, 2016, 05:32:28 PM »
mine is a 3-phase pmg generator. anything out there for my situation?

SN
Look up DC2465, its a demo circuit that linear technologies put
together to use 3 of their LT4320 ics for 3-phase rectification.
While significantly more complex than the single chip single phase
design, it is still very much DIY possible. I think I will use it as single.
phase for a bit before trying the 3-phase version.

By the way i finally managed to get 3 ordered today from digikey for $8.44 ea.
i offered an ebay guy 8 and he countered at $20 each. I declined of course

Quote "Or was that the part you were avoiding?" Steve.

You nailed it ;D. LMAO.

Im good at repair/trblshooting, not so much with design, i have to edit too many times. ::)

LH

LH

Offline Solarnewbee

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Re: Ideal bridge rectifier
« Reply #6 on: October 15, 2016, 02:37:54 PM »
looked up the LT4320IDD or DC2465A-nd, its a board built for 3-phase input, 5vac-28vac rms 25a load max. Looks like it would be an ideal board since I don't design and build boards but at $126 each and I need 2 for my dual PMG well,,, it'll have to wait. I do appreciate the direction so I can keep it in mind when I do haul the windmill to the Philippines.

Have a great day!

SN
SN

Any day above ground is a day for potential mishaps

Offline oztules

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Re: Ideal bridge rectifier
« Reply #7 on: October 15, 2016, 05:17:59 PM »
Not sure it is worth playing with for wind genny. The 1/2 volt your trying to save is immaterial in the scheme of things, especially considering wild AC and loss of simplicity and robustness to handle it.

I bought a heap of 150amp 1500v diodes for very little, and that will rectify anything I may come up with, with no chance of failure.

If your paying for the losses from a finite source, it's a different risk reward profile.... but a wind genny.... emf is not the problem, and in fact losses may help the air/battery load matching, far more than the 1/2 volt sacrifice. A slight change in wind velocity will have a much greater effect in this case.


.............oztules
Flinders Island...... Australia

Offline MadScientist267

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Re: Ideal bridge rectifier
« Reply #8 on: October 17, 2016, 10:55:38 PM »
I'd have to agree with Oztules, especially given that the one pictured isn't all that much different in appearances from what I've got.

Having a hard time swallowing the idea that there's 3 $ digits worth of magic buried in there somewhere, given that I've vaguely mapped out the discrete component single phase version of it, and understand the principles at work on it. 3 phase tends to mix things up a bit when it comes to conversions, but dunno bout all that LOL

ila_rendered

ila_rendered

That's all there is to this one... no magic tricks, no black box chips... it's asymmetrical because of its intended implement, but that's little more than "details" really. Only thing that makes it even remotely "tricky" is the speed it's designed to run at, requiring everything be super-tight bunched... at the speeds you're looking at using something like this for, there's no real need. Nice thick source/drain paths and a little sinking, pffft no problem.

Side note along those lines regarding this particular board - the supply it comes from is rated 62A on the 12V rail - What you see is nearly what was there... only thing I removed was a little tab with a thermistor attached, to control the fan (externally done); and it only failed because it had months on end of *no* airflow (probably at something averaging half rated load or so). It's intended to sit directly under a fan and uses primarily the rails to wick and spread heat.

That said, I can't say one way or another about suitability for a wind turbine, I'm a solar guy... but put it out there because the premise of the topic is a fit under "ideal bridge".

If anyone is interested, I may sketch it up for my own use anyway at some point... squeaky wheels get the grease. Someone else would have to adapt it for 3 phase, as I have no foreseeable use for such a thing :P

Either way, the entire supply new is 80 bucks... and has at least 2 other "complete salvage" value sections in it... so IMO, 100+ for a dinky little board..? Well that's just gouging :-\

Steve
Wanted: Schrödinger's cat, dead and alive.

Offline oztules

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Re: Ideal bridge rectifier
« Reply #9 on: October 18, 2016, 03:12:36 AM »
For battery charging, the synchronous rectifier can be stupid simple... as you don't care about cross over.... for about 10volts or more on a 12v system to up to 44v for a 48v system.. so really  P channel and N channel fets, a resistor and a zenner should actually do the job just fine.

It can slow turn on from 0-10v as the wave increases, and we loose no power through the linear section, by the time we start to actually charge on the rising wave, we are fully turned on at say 10-11v... and still no current passes until we get up to 12v or more, where we are fully on anyway... and same for going down the back of the wave, we stay turned on until 0v, but pass no power during the 12v down to 0 volts so the losses are not there for either switching or anything else.... should be perfect, same for the p channel side.... so maybe only a handful of parts for a full synchronous rectifier.

Then it is worthwhile doing, say $30 for a 100 amp 12v system..... up to 100v for 4110 fets and P channel equivalents ( more of them for lower RDS on )... switching speed is irrelevant.

In 48v systems, the rds on may be no better than the diode route anyway....... but gee... for wind......seems a waste of time still.



..........oztules
Flinders Island...... Australia

Offline Solarnewbee

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Re: Ideal bridge rectifier
« Reply #10 on: October 18, 2016, 04:09:26 PM »
Oz

Given those stats and considering I'm using a 3000w windmill as only augmenting solar I think I'll take your advice and leave out the extra gadget $$$$ saved

Thanks
SN
SN

Any day above ground is a day for potential mishaps