A niche chip (LT4320) for mains powered AC -> low volt DC "linear" based psu ? - Page 1
Forum section: electronics / beginners

author: BravoV
author_rank: Super Contributor
timestamp: September 24, 2013, 05:35:26 am
content: Not sure if this is old news, just found out that this little gem should be one of the nice component to replace those scorching hot silicon rectifier.For sure if I'm going to build another linear based power supply (one off project), this will be in my shopping list.Also I'm curious, if the input is pure DC, isn't this chip will act like an overkill reverse polarity protection circuit ?Any second thought ?Linear Technology LT4320 ->http://www.linear.com/product/LT4320

author: Bored@Work
author_rank: Super Contributor
timestamp: September 24, 2013, 06:41:43 am
content: Quote from: BravoV on September 24, 2013, 05:35:26 amMains powered? Not directly. Max. input voltage is 72 V.

author: BravoV
author_rank: Super Contributor
timestamp: September 24, 2013, 06:44:45 am
content: Quote from: Bored@Work on September 24, 2013, 06:41:43 amMy mistake, I mean through step down transformer as traditional AC->DC low voltage linear psu.

author: SeanB
author_rank: Super Contributor
timestamp: September 24, 2013, 09:04:00 am
content: Not a bad device, solves the problem in a very elegant way.

author: kizzap
author_rank: Unknown
timestamp: September 24, 2013, 01:40:07 pm
content: I saw this one a few weeks ago and thought it was a brilliant idea. I mean who doesn't like the thought of extremely low losses for rectification?The only thing that made me sad is the fact that you need to use external MOSFETs with it. Give me a drop in replacement option for current SIL bridge rectifiers, and I will LOVE it.-kizzap

author: BravoV
author_rank: Super Contributor
timestamp: September 24, 2013, 03:25:11 pm
content: Quote from: kizzap on September 24, 2013, 01:40:07 pmI'm assuming that your view is from pro or commercial perspective ?As an hobbyist, those 4 mosfets are insignificant factor to me, either in cost, board space or effort in building the circuit.Quote from: mojo-chan on September 24, 2013, 02:51:58 pmLooks like it, especially they emphasizing in the datasheet the importance of placing at the DC output with "minimum" caps 1uF ceramic + 10uF electrolytic type, these must be just for supplying it self right ? cmmiw, ee wannabe here.Besides who the heck will use that total low cap value at the output like that anyway ? Unless they're trying to generate high current and "high ripple" signal.Btw, its very unlikely that its powered from the AC side right ?

author: digsys
author_rank: Unknown
timestamp: September 24, 2013, 03:37:56 pm
content: There's been many iterations of FET bridges to minimise power loss, but usually require a heck of a lot more components.I'll definitely whip a proto pcb for our 20-30A P/S units. Hopefully there are no "limitations" or "side effects".Not having direct on/off control of the FETs may be a dis-advantage, but the IC looks very interesting.Thanks for the heads-up.

author: BravoV
author_rank: Super Contributor
timestamp: September 24, 2013, 03:41:58 pm
content: Quote from: digsys on September 24, 2013, 03:37:56 pmPlease, update us once you used it.Quote from: digsys on September 24, 2013, 03:37:56 pmNoob question, regarding the huge inrush current at power up, especially at the output with the large value capacitor, is this better and/or more reliable compared to plain old silicon diodes ?

author: Bored@Work
author_rank: Super Contributor
timestamp: September 24, 2013, 03:57:24 pm
content: Quote from: digsys on September 24, 2013, 03:37:56 pmThe first trap is in the first picture of the datasheet. Already postd aboveIt says DC to 600Hz, but that requires the LT4320-1, not the LT4320 as shown in the picture.

author: digsys
author_rank: Unknown
timestamp: September 24, 2013, 04:19:11 pm
content: Quote from: BravoVI have a new run of PCBs coming up soon, hopefully have something in 2-3 weeks. We're always looking at new ideasat replacing bridges / rectifiers, so this is timely.Quote from: BravoVAll silicon can withstand quite severe inrush currents. It's the RDSon / pulse-time / energy > heat that kills them.FETs can have extremely low RDSon figures and are "better" by an order of magnitude +

author: BravoV
author_rank: Super Contributor
timestamp: September 24, 2013, 04:19:45 pm
content: Quote from: Bored@Work on September 24, 2013, 03:57:24 pmC'mon, its just a typo.Assuming it will be used on mains stepped down using transformer at 50 or 60Hz as most of the cases, whats wrong with LT4320 even though it is designed for DC up to only at 60Hz ?

author: BravoV
author_rank: Super Contributor
timestamp: September 24, 2013, 04:21:18 pm
content: digsys, eagerly to hear the results from you, thanks !

author: johansen
author_rank: Super Contributor
timestamp: September 24, 2013, 04:31:39 pm
content: a close look at the datasheet suggests that they charge those mosfets up with some kind of onboard silicon capacitive voltage doubler.at a maximum current of 800uA, dropping to 300uA once the fet gets to 5 volts on the gateand discharge of 1.x mAbottom gate pull up is 6mA, pull down is 12you will need a pnp assisted turn off at a minimum.

author: Bored@Work
author_rank: Super Contributor
timestamp: September 24, 2013, 04:33:32 pm
content: Quote from: BravoV on September 24, 2013, 04:19:45 pmNothing, if you only use it up to 60 Hz. But if you happen to e.g. work in a 400 Hz environment it can cause you some grieve.Linear seems to get a bit sloppy with their datasheets.

author: digsys
author_rank: Unknown
timestamp: September 24, 2013, 04:40:42 pm
content: Quote from: johansenAt 50/60Hz (even 600Hz) that's heaps of time ! I'm more interested on how they work out Vin-Vout / current direction sense / control.That's always the "tricky" part !!Quote from: johansennot sure what you mean

author: johansen
author_rank: Super Contributor
timestamp: September 24, 2013, 04:48:39 pm
content: http://i227.photobucket.com/albums/dd168/Toey1/Turnoffsharpener.jpgcurrent gain is subject to hfe

author: digsys
author_rank: Unknown
timestamp: September 24, 2013, 05:12:15 pm
content: Still not sure what you mean?I can't see LT making a custom chip and "forgetting" to have enough drive dynamics to the FETs, after all, most willonly ever operate at 50/60Hz. Plus we have no idea of internal topography and if we are even able to referenceextra drive devices? Did you find more app circuits? Well, I'll find out in a couple weeks or so anyway.

author: johansen
author_rank: Super Contributor
timestamp: September 24, 2013, 05:40:48 pm
content: Quote from: digsys on September 24, 2013, 05:12:15 pmi don't consider 6mA of gate pull down current sufficient for anything.i suppose in theory it works.i mean i've seen 60 volt 60 amp fets driven directly from an LM358 without a gate drive resistor.i've also seen the same fets driven from something 1000 times "stiffer" but then they used a 2.2K ohm gate resistor.both of those examples are from 300-500 watt push-pull APC UPSbut that is still on the order of 10 times as much current as that chip can deliver.

author: johansen
author_rank: Super Contributor
timestamp: September 24, 2013, 10:03:30 pm
content: it seems to me this chip is aimed at very low power consumption devices.and at 4$ per chip in a 10 lead MSop device it seems to be targeted for very small devices as well.1mA of gate drive sounds like its enough but in practice i think we're looking at something that might be able to handle a 10 amp diode bridge but not much more without additional gimmicky to built a more robust gate drive.i think you could make a bootstrap cap, diode, zenar, npn/pnp driver to assist this device that could drive an amp or five through a big Fet from just another mA or three of power dissipation, but my brain is mush right now.assuming reasonable expenditure on diodes, you can get 100mv per 10 volts PIV rating reasonably cheap.so for a 35 volt dc output from 24vac, we need 40 volt mosfets (i would run them that high, but many won't, so they will go for 50 volt fets)at 10 amps dc current we go for 10mOhm fets at 1$ each. plus 4$ for the part and two square inches of board space.that's 8$ to get from 10 watt of loss from standard silicon at 1 volt drop to 2 watts of loss.or i can get some .35 volt drop schottky diodes and let them radiate the 7 watts of heat away at 100C, for 6$.2$ increase to save 5 watts is tempting, but that's 40 cents per watt that could be spent elsewhere.not a bad trade off really, but they could have integrated a bootstrap capacitor and made a larger, higher voltage device.

author: BravoV
author_rank: Super Contributor
timestamp: September 25, 2013, 03:10:38 am
content: Quote from: digsys on September 24, 2013, 05:12:15 pmWhich mosfet do you have in mind ?Questions on the mosfet selection criteria quoting the datasheet :QuoteSay we working at common 50/60Hz, although it stated to use lowest gate charge, but how low is low enough ? <= 1000 pF ? <=2000 pF ? I can't find it in the datasheet.Am I correct at that VGS threshold requirement, basically it rules out those logic level mosfet ?

author: digsys
author_rank: Unknown
timestamp: September 25, 2013, 05:41:25 am
content: Quote from: BravoVParts are ordered from USA. Hopefully 7-10 days max. I have dozens of high power Mosfets in stock.I'll just plug various buggers in and see what happens :-) In one app paper they specify up to 30A parts, so I'm sure prettymuch anything will work. Now to do a PCB bridge replacement.

author: BravoV
author_rank: Super Contributor
timestamp: September 25, 2013, 05:53:29 am
content: Quote from: digsys on September 25, 2013, 05:41:25 am

author: BravoV
author_rank: Super Contributor
timestamp: September 25, 2013, 06:04:55 am
content: Interesting brief insight about this chip found in ->Linear Tech. Press Release : Ideal Diode Bridge Controller Minimizes Rectifier Heat & Voltage Loss (PDF)and this chip is just released recently in June 2013, pretty new.Quoting few interesting topics raised by johansenQuote

author: tszaboo
author_rank: Super Contributor
timestamp: September 26, 2013, 09:15:19 am
content: I wrote about this chip some time ago, also some considerations, etc...http://nandblog.com/chip-review-ltc4320/The bottom line is, if you use some linear regulator on the output, it might be not worth it, since you will dissipate the voltage anyway. Sometimes it is useful.

author: digsys
author_rank: Unknown
timestamp: September 30, 2013, 12:47:58 pm
content: Update: ICs are here, PCB layout done (based on a H-Bridge layout I did in the past, it should handle 30A - bolted to some Al naturally)It will be 2-3 weeks though until I do a PCB run. Itching to see how it performs.

author: tszaboo
author_rank: Super Contributor
timestamp: September 30, 2013, 08:26:48 pm
content: Datasheet sais exposed pad must be connected to OUTN. That pad also needs more copper to cool the device down. I dont see the reason to use bent TO220 if you can just use D2PACK mosfets. and more vias for high current. Just increase the copper size, it doesn't cost anything.

author: BravoV
author_rank: Super Contributor
timestamp: October 01, 2013, 02:52:41 am
content: @digsys, thanks for the update.Btw, are you planning to use gate resistor ? I thought we don't need that according to the datasheet.

author: digsys
author_rank: Unknown
timestamp: October 01, 2013, 04:18:58 am
content: Quote from: BravoVTechnically, this is a "prototype" layout for me, so I leave the capability of monitor points to test stability etcIf everything is fine, I'll probably leave them in anyway, and just use 1R resistors. Checking gate drive capability isimportant to me, as it will hopefully go in a commercial product. Vin-Vop switching characteristics I can do externally.Quote from: NANDBlogThe posted artwork isn't 100%. The PCB is based on an existing 30A H-Bridge that I made years ago, and worksextremely well !! The PCB is 8oz, exposed, with a copper blocks under the TO220s, screwed down hard, which is whyI use them. Artic silver cement thermally bonds the crap out of it all. Thanks for your comments.

author: BravoV
author_rank: Super Contributor
timestamp: October 01, 2013, 04:24:06 am
content: Quote from: digsys on October 01, 2013, 04:18:58 amAhh .. I see, never thought of that, learn something new and good knowledge today, thank you.

author: resistor
author_rank: Regular Contributor
timestamp: November 27, 2013, 11:52:58 pm
content: So... how did the prototype turn out?

author: digsys
author_rank: Unknown
timestamp: November 28, 2013, 12:00:17 am
content: Quote from: resistorFunny you ask .. All PCBs assembled and wired up, was about to Solder in the FETs I chose, but just found out the partsare on hold because the account wasn't paid .. GRRRRRRI'll probably just use the 25mR FETs I have, instead of the 0.9mR - 1.9mR that are on hold, at least just to prove it andget a few readings (with my FlirE48+ :-) ) Hopefully answers in a few hrs

author: BravoV
author_rank: Super Contributor
timestamp: November 28, 2013, 11:50:11 am
content: BTW, just noticed there is an update in the datasheet, and apparently its now available in DIP 8 package, great news for hobbyist who want to build a traditional AC to DC step-down transformer based linear power supply.

author: digsys
author_rank: Unknown
timestamp: November 28, 2013, 02:21:41 pm
content: Quote from: BravoVJust when I perfected my thermal pad artwork and soldering method :-)Preliminary results - as per PCB linked before - Using CSD18502KCS NFET, TO220, RDSon=2.4mR, GateCap=3900pFFETs bolted to a double sided PCB x3oz using Arctic Silver and no other heatsinkRan at 10A continuous for several minutes - 4,700uF and 16,700uF - FETs barely warm.- as above but at 15A continuous - FETs quite warm, but not too hot to touch.The waveforms were the most impressive, absolutely clean with no detectable switching steps, in all conditions.I'll run harder tests tomorrow, along with Flir images. So far - VERY impressed. The test PCB should go to 30A.

author: BravoV
author_rank: Super Contributor
timestamp: November 28, 2013, 03:02:47 pm
content: Quote from: digsys on November 28, 2013, 02:21:41 pmLOL ..., also curious why LT made such package, I thought thru hole is dead ?Anyway, its so new, when I tried the LT's online shop, the DIP version still not available.Quote from: digsys on November 28, 2013, 02:21:41 pmThanks for sharing this.Sounds quite impressive, and 15A for my personal project should be more than enough.Please, if it's not troubling you too much, share few scope's shots the waveforms you mentioned above, also could you please do a startup capture, just curious to how it performs when turned on for the 1st time.Btw, those tests were done at what voltage ? and whats your expectation or target on the current at your circuit ? 30 Amp ?

author: digsys
author_rank: Unknown
timestamp: November 28, 2013, 03:12:59 pm
content: Quote from: BravoVRan them at 5VAC and 25VAC. Next I'll check lowest AC possible and a max of 35VAC (These FETs are only 40V)I need to see that they run perfectly fine at 30A, in our 20A units. Still waiting for other FET types, including the 0.9mR ones.

author: BravoV
author_rank: Super Contributor
timestamp: November 28, 2013, 03:23:23 pm
content: Quote from: digsys on November 28, 2013, 03:12:59 pmGreat, so eager to see if the UVLO kicks in, and how those mosfet drivers perform at quite low voltage. I guess they designed this chip with the target circuit for linear regulator with output minimum at 5V, isn't it ?Quoting the datasheet :"OUTP Undervoltage Lockout (UVLO) Threshold, Conditions : (INn = OUTP, Other IN = 0V) , Min 6.2V, Max at 7.0V"

author: digsys
author_rank: Unknown
timestamp: November 29, 2013, 04:58:00 am
content: Only had time to run a few more tests, some pix later.- With small load, min AC is app 6V. Literally just kicks in / drops out.- Increased Caps to 60,000uF and 18A Load. Ran several mains on/off sequences rapidly - didn't bother it or confuse it. annoyed ...- As above into a dead SHORT for 5 secs. FETs started heating up damn fast, IC still kept trying to run them, and instantly recoveredonce short cct was removed. Transformer was reading AC 83A RMS !!!! at 24VAC ... it's a big transformer :-)So far, failed to blow the sucker up. I'll try huge Inductor loads next week.

author: BravoV
author_rank: Super Contributor
timestamp: November 29, 2013, 09:01:05 am
content: So far it looks pretty good eh ?About the upcoming destructive testswith inductor, do you put any TVS as recommended by the datasheet ?With the inductor kick back voltage, I guess it can easily surpassed the absolute max. rating at 80V for the OUTP pin, so exciting to hear the results of this test.Thanks for keeping us updated.

author: digsys
author_rank: Unknown
timestamp: December 24, 2013, 04:01:14 pm
content: In Version 2 I used - IRFS3004-7P : D2PAK, 0.9mR, 280A, 9200pF, 40V. The LT4320 had no problems at all driving the higher Gate capacitance,BUT once again there was a sudden LARGE temp rise at around 16A. Turns out that the IC will operate at 6VAC, but at ~16A+ you need amin of 12VAC to give the charge pumps sufficient drive. (even though the waveforms looked perfectly OK).With the new layout 3oz both sides, the PCB starts to get warm after 15-20 secs at 21A. Max dropout is ~100mV for a few mS during thecapacitor charge time. Once I upgrade the E-Load (once again) to 30A+, I'll try for a destructive test. All in all - I LOVE ITMore pix at -www.pbase.com/digsys/electronics_stuffz

author: BravoV
author_rank: Super Contributor
timestamp: December 25, 2013, 11:07:07 am
content: Thanks for the update !I guess at 6VAC is barely enough power to feed the gate driver isn't it ?Just curious, at +30A you mentioned that you are going for destructive test, at what voltage ?PS : Seeing your photo gallery there, to be honest, I sort of lost the interest of this chip for a while, too much distractions, there are tons of cool T&M equipments you have there, just wow !!!!!!

author: digsys
author_rank: Unknown
timestamp: December 25, 2013, 12:02:43 pm
content: Up to ~15A, 6VAC is fine, and it also depends on the level of ripple on the DC caps ! If you look at the Gate drive waveform,it is heavily "influenced" by it. I don't have an exact correlation because I'd be guessing on how the charge pumps work.Now that I know there is a 3 way relationship, I'll want to find the min AC at max I (at lowest reasonable ripple for now).That sudden temp rise is most likely a result of "leakage" current, but now I have to set up an accurate current sense andplot all the waveforms. At least I know it's not an issue over 12-15VAC for 20-30A respectively.All that (old) gear is going to be sold, once I find time to work out the heck some of it is ! I'm also getting rid of several boxesof various circuit boards from a 15yr old installation that's just been de-commissioned. So much for holidays :-)

author: BravoV
author_rank: Super Contributor
timestamp: December 25, 2013, 04:00:15 pm
content: Quote from: digsys on December 25, 2013, 12:02:43 pmThat is almost half a kilowatt there.Btw, what is the 3 way relationships you're talking about ?Looking forward to see the result on min AC while at max current, should be interesting and will be useful info.Quote from: digsys on December 25, 2013, 12:02:43 pmThat are butt load of gears you have there, I guess that can not be done in one or two days job.

author: tszaboo
author_rank: Super Contributor
timestamp: December 26, 2013, 04:33:24 pm
content: Quote from: digsys on December 24, 2013, 04:01:14 pmThere are two minor problems I saw with your layout. One is that you put the fuse (in parallel? dont do that) on the output of the bridge, and it should be on the input. If your something fails on the bridge because of the destructive test, nothing is protecting your input. The other problem I see is the lack of high frequency bypassing. Otherwise it is interesting.

author: digsys
author_rank: Unknown
timestamp: December 26, 2013, 10:09:55 pm
content: Quote from: NANDBlogThanks, but they're actually Polyfuses, and they work extremely well in parallel. We even heatshrink them together fortighter thermal "coupling".Quote from: NANDBlogI don't intend to place them there, I just needed a "test point" and that artwork looked sort of relevant to an observer :-)It's a current "pick-off" point and a thermal break (for my FLIR E8+ .. oops I meant E4) to test the 3+3oz Cu temperature.Usually I ALWAYS use 4+4oz, but had a short cut-off time for delivery before xmas. I usually have all protection somewherewhere it's user-serviceable, NEVER on the main PCBs anyway.Quote from: NANDBlogThere's enough HF filtering, just not shown on the pix. All done as per design notes, but I do like to see what goes "wrong"under those circumstances. It's all part of proper design / testing.

author: Phaedrus
author_rank: Frequent Contributor
timestamp: December 26, 2013, 11:20:58 pm
content: What's your efficiency looking like?

author: digsys
author_rank: Unknown
timestamp: December 26, 2013, 11:40:30 pm
content: Quote from: PhaedrusDAMN GOOD, even at 20A! If you check the waveforms, V2 has a drop of ~100mV for 1-2 mS. Even with that small PCB,the FETs didn't get too hot, well under their rating. V1 are good to 15A with very little heat.In V3, I'll go back to 4oz and add small Cu wings, just for extra headroom.

author: Zero999
author_rank: Super Contributor
timestamp: December 27, 2013, 12:16:27 am
content: Just thinking. Another use for this IC could be a brushless motor driver designed to maintain compatibility with a permanent magnet DC motor h-bridge. The driver circuit would always be powered from the same polarity but an input could be connected to the bridge rectifier input to reverse the motor when the input polarity is reversed.

author: BravoV
author_rank: Super Contributor
timestamp: December 27, 2013, 03:41:24 am
content: Just want to thank the "Santa Claus" in this thread here, attached photo below the thing I found under my chimney.

author: Phaedrus
author_rank: Frequent Contributor
timestamp: December 27, 2013, 05:43:05 pm
content: Hm, would be nice if they had a higher-voltage version that can work directly off mains voltage (up to 264VAC). The bridge rectifier is one of the last remaining major loss zones in an ATX PSU. Being able to get rid of those diode losses is a major goal. If a high-voltage version of this chip could be implemented more cheaply than a digital controlled bridgeless PFC, then this could be a great option...

author: tszaboo
author_rank: Super Contributor
timestamp: December 27, 2013, 11:00:45 pm
content: Quote from: AcHmed99 on December 27, 2013, 10:35:38 pmNot to mention, at 6V the diode drop is 10%, at 230 it is only 0,3%. Well, just close numbers.

author: johansen
author_rank: Super Contributor
timestamp: December 28, 2013, 04:09:44 am
content: a zero loss diode bridge would not be very useful for high power high voltage circuitry anyway.. because you would need a high volume inductor after the bridge to keep the power factor within reason.there are a few diode-less pfc topologies available, most produce a lot of common mode noise.there is a topology i like but i haven't developed a controller for: see attachment

author: Phaedrus
author_rank: Frequent Contributor
timestamp: December 28, 2013, 07:58:58 am
content: Well right now the most common topologies in PCs go like this:Common Mode Filter --> Bridge Rectifier --> Interleaved boost converter PFC --> PWM --> Transformer --> SecondaryThe most common PWM topologies are either Double Forward (for 80%-87% efficient PSUs), or LLC Resonant Half or Full Bridge (for 87-92% efficient PSUs). There's also some high-end ZVS Phase-Shift Full Bridge units, and a popular Active Clamp Forward platform.Anyway, efficiency is an important marketing feature, and the big efficiency certification is 80PLUS. Currently the top of the line runs 80PLUS Platinum, which requires 89-92% efficiency at 115VAC at room temperature. There are about a half dozen ODM vendors who can currently reach this and still maintain "enthusiast grade" voltage regulation and ripple.But 80PLUS is working on a new standard, called 80PLUS Titanium. The spec isn't finalized, but word is the efficiency at 50% load will have to be either 94% or 95%. That's 2-3% that we need to gain over current designs, most of which just clear Platinum.We've adopted the DC-DC secondary topology which netted the 1-2% boost needed to hit 80PLUS Gold back in the day. It's hard to improve that much more, considering we're already using synchronous rectification both for the main +12V rail and for the minor rails. Assume we can boost the efficiency of the DC-DC modules, call that a 0.25% gain.The transformer and other magnetics efficiency is improving slowly but surely. We can probably get another 0.5-1% there by end of next year.With improvements to layout, connectors, shortening power traces, using thicker copper, etc, we might get an extra 0.25% there.So we need *at least* 1% more gain. PWM topologies are currently close to maxed out, it's unclear how much more we can gain there. So where do we have obvious losses we could cut? The bridge rectifier and the PFC diodes.Replacing the diodes in a boost converter is a classic power electronics problem that has yet to be solved. I don't think anyone's made one that doesn't nuke itself yet.So that leaves the bridge rectifier. The current trend is to go bridgeless PFC, which replaces the bridge rectifier with active MOSFET rectification. No one has built an adequate analog controller to do this yet (the LT4320 is the closest I've seen), so currently you have to use MCU control. This normally ends up with the entire PSU being MCU controlled, instead of analog, which is a $30-$50 increase to BOM cost.If someone could figure a way to do it analog, without requiring a digital control loop, for $20 BOM or less, that would be a killer advantage in the market. If we could get 0.5% efficiency there that would put us in reach of 80PLUS Titanium certification at a lower cost than the competition.

author: digsys
author_rank: Unknown
timestamp: December 28, 2013, 08:31:07 am
content: Quote from: PhaedrusI find itinterestingthat they can't get better? We've had MPPT chargers (which have a much more difficult task) at app 97-98%for many years. Our current design, by one of our members, runs at 98.5% at 4:1 In/Out range over most the power range.It's a resonant synchronous design. They even have resonant controller chips out now. Mainstream doesn't seem to be interested inefficiency unless they're forced to.

author: Phaedrus
author_rank: Frequent Contributor
timestamp: December 28, 2013, 04:57:59 pm
content: Quote from: AcHmed99 on December 28, 2013, 11:45:06 amActually there's quite a large market for quality power supplies. The gamers, enthusiasts, and Litecoin miners all want quality kit, and will pay for it. The cheap $20 crap may move in volume, but it's not particularly profitable most of the time. The $50 - $150 segment is extremely competitive and usually quite profitable. In the US, 650W, 750W, and 850W power supplies that are 80PLUS Bronze (82-85%) or 80PLUS Gold (87-90%) sell very well; total market size of 25,000-40,000 of those wattages a month. Average price near a hundred bucks.Crack open one of our CoolerMaster V850 power supplies and tell me that's cheap crap. It may not be lab grade, but it's solid engineering and good build quality.

author: M. András
author_rank: Super Contributor
timestamp: December 28, 2013, 05:55:53 pm
content: if the damn psu is as reliable as it can be like those decades old hp lab power supplies then i will gladly pay a fair price for it, not like the cheap 50-100bucks cheap 500+watts shit what cant even deliver its rated power and when i dies kills the attached things too.im wondering if this chip could be used with pretty low rdson fets and its power supplied externally it doesnt need much so a small bridge rectifier from the main ac feed maybe? high power losses would be minimal too

author: tszaboo
author_rank: Super Contributor
timestamp: December 28, 2013, 09:02:40 pm
content: Quote from: Phaedrus on December 28, 2013, 04:57:59 pmwow, they are using double sided PCB, which is not from paper, and there are even smd components on a small board. They are only 20 years behind todays technology, not 25. To be honest, I really think that PC power supplies are lagging behind. A modern design would use planar magnetics, moderate-high switching frequency, multiple phases for DC-DC, SMD mosfets, power blocks like drMOS, and pulse skipping or other intelligent driving to increase efficiency for light loads. Also most PC power supply is standby power hog, because the lack of secondary circuits for that. Well I guess these will be standard in 20 years or so.

author: digsys
author_rank: Unknown
timestamp: December 28, 2013, 10:23:03 pm
content: Quote from: M. AndrásVery unlikely. If you've ever looked at designing a FET bridge, there's a very tight relationship between the AC side and DC side.Supplying a separate low VAC for the charge pumps, even IF you could line up phases etc is unlikely worth it.Basically, the "control chip" watches the VAC level coming in, compares it to the DC level, and once it becomes +ve, switches the FET.On higher currents, it waits until the onboard Shottky conducts before doing so. You can see it in the waveforms.If you don't do this, at the instant of switch-on, depending on cap storage = app INP/OUT impedance, the VAC can suddenly DROPagain, below DCV, in which case you now have current feeding BACK into the Transformer (in this case). It's only a short time, butcan cause huge current spikes / losses. I'm about to make up a bi-dir current sense and really get a better picture.Having made these devices in the past (using optos, external charge pumps and isolated high speed logic control), it's a reallyvery tricky design, which is why I was so impressed with it.ALL it needs is a 0V side referenced shutdown pin (maybe Ver2?) and it'd then truly be AWESOME !! I've tried to email them withsuggestions, but it's impossible to find a tech feedback addy. You would have thought?Why do we need this? O/Temp, O/Current, O/Anything SHUTDOWN ! The perfect oN/oFF control of up to 20-30A with a 10uA 3V signal !!!woohooo heaven.

author: Phaedrus
author_rank: Frequent Contributor
timestamp: December 29, 2013, 12:25:20 am
content: Quote from: NANDBlog on December 28, 2013, 09:02:40 pmIt's a 300KHz LLC resonant full bridge. We use SMD mosfets for secondary rectification for the +12V rail, mounted on the bottom and heatsinked to the housing. We use pulse skipping to improve efficiency at light loads; at 10% load you can expect 85-87% efficiency (depending on if you have the 700W, 850W, or 1000W). Planar magnetics aren't cost-effective for us, and DrMOS has proven unreliable for us with few advantages over discrete components.You could buy something like this twenty years ago--in a bespoke device costing $10k+. Now you can get it in a consumer device for $80 - $150. And still they bitch?The snobbery of some engineers continues to astound.

author: necessaryevil
author_rank: Regular Contributor
timestamp: December 29, 2013, 07:25:43 pm
content: I agree it is indeed amazing what you get for your bucks buying an ATX psu. I guess that making a more efficient ATX supply is not more cost effective (the reduction in electricity costs is not enough to pay back the higher initial costs).But back on topic. Would it be possible to make a batch of those pcb's (which will make it cheaper)?

author: tszaboo
author_rank: Super Contributor
timestamp: December 29, 2013, 10:19:14 pm
content: Quote from: Phaedrus on December 29, 2013, 12:25:20 amIt looks like it has more features than I anticipated. Probably they did not take fully apart because of the SMD on the bottom.May I ask why was DrMOS unreliable? I'm recently looking into the possibility use them in industrial applications. The only downside I see right now, that the internal MOSFET sizes are not optimal for my output voltage (I need about 2-3-4 volt output, not 1.2-1.5V they are designed). Can you share some background information?

author: Phaedrus
author_rank: Frequent Contributor
timestamp: December 30, 2013, 12:45:34 am
content: Quote from: NANDBlog on December 29, 2013, 10:19:14 pmWe haven't used them in our PSU designs, but I worked for a company that used them in motherboard VRMs. The problem is that DrMOS seems to be very sensitive to reverse voltage; just a little bit and it'll let the magic smoke out. You have to be very picky with your inductors, and don't trust the peak current ratings. The motherboards using them had higher than average DOA rates, and very high returns with blown VRMs 6-18 months down the road. Correlating with higher CPU wattage of course, but the combined current of the DrMOS should have been more than adequate.They also aren't good voltage for ATX PSUs.

author: megajocke
author_rank: Regular Contributor
timestamp: December 31, 2013, 02:07:18 am
content: Quote from: digsys on December 28, 2013, 10:23:03 pmBut, you still have the body diodes of the MOSFETs, don't forget those!Removing the gate drive from the FETs would just turn your nice low-loss bridge rectifier into an ordinary high-loss one, and the magic smoke would be released soon if the cooling is designed for the low-loss mode of operation.To get shutdown functionality you need more switches anyways so the functionality could be made completely separate, using just a single FET on the DC side for example.

author: digsys
author_rank: Unknown
timestamp: December 31, 2013, 05:06:28 am
content: Quote from: megajockeDOH !! :-) I wish we could "edit" or "delete" posts :-) ..... lol

author: necessaryevil
author_rank: Regular Contributor
timestamp: December 31, 2013, 04:00:46 pm
content: @NANDblog, Pheadrus,Any recommended docs/books about ac-dc topology for the novice? I'm quite interested.

author: ResR
author_rank: Regular Contributor
timestamp: December 31, 2013, 05:57:17 pm
content: I made the PCB design for that chip also with all through hole components, the pcb is 74x69mm in size.

author: digsys
author_rank: Unknown
timestamp: December 31, 2013, 10:14:15 pm
content: Quote from: ResRGreat. What current are you expecting to run yours at? Have you used it in a project yet?

author: Phaedrus
author_rank: Frequent Contributor
timestamp: December 31, 2013, 11:05:08 pm
content: Quote from: necessaryevil on December 31, 2013, 04:00:46 pmI learned from Wikipedia, Texas Instruments white papers, and talking to engineers. Sorry, can't help with books.

author: BravoV
author_rank: Super Contributor
timestamp: January 01, 2014, 08:27:52 am
content: Quote from: ResR on December 31, 2013, 05:57:17 pmHmmm.. DIP 8 package, where did you buy that chip ? Just checked LT's shop, the LT4320IN8#PBF or LT4320IN8-1#PBF for the dip 8 still not available yet, and FindChips search results too, no luck.Although you already have the big cap on the top at your layout there, read the datasheet at "CLoad Selection" section, its recommended to have small caps to complement that big cap above, that are placed really close to OUTP and OUTN pins, probably at bottom right of your pcb layout there, close to the IC.Edit : Don't forget PCB mounting holes at the four corners.

author: tszaboo
author_rank: Super Contributor
timestamp: January 01, 2014, 10:51:54 am
content: Quote from: necessaryevil on December 31, 2013, 04:00:46 pmI'm really not an expert on that field, sorry.

author: digsys
author_rank: Unknown
timestamp: January 01, 2014, 11:10:31 am
content: Quote from: BravoVOne thing I've definitely proven with this IC is - you can't bust it !! It works perfectly well with no / excess compensation, poor layout,too much / too little filtering etc etc You just can't stop it working ! BUT, keep that extra safety - add noise caps etc etc

author: resistor
author_rank: Regular Contributor
timestamp: January 01, 2014, 10:09:20 pm
content: Could this chip be used for AM demodulation as an envelope detector? Or would the feedback mechanism interfere with the intentional amplitude variations?

author: digsys
author_rank: Unknown
timestamp: January 01, 2014, 10:26:34 pm
content: Quote from: resistorI have very little experience in this area - but note possible limitations : 600Hz max AC (ver2), 6VAC min, 100-220uF sec min.

author: BravoV
author_rank: Super Contributor
timestamp: January 01, 2014, 10:29:29 pm
content: Fyi, this chip max out at only 600 Hz, not even 1 KHz, AM modulation is way-way higher isn't it ?

author: resistor
author_rank: Regular Contributor
timestamp: January 01, 2014, 11:03:45 pm
content: OK, true, the frequency limitation would kill this for actual AM radio. But could it be used as an envelope detector for a frequency that was inside its range?

author: peter.mitchell
author_rank: Super Contributor
timestamp: January 02, 2014, 02:42:18 am
content: Quote from: digsys on January 01, 2014, 10:26:34 pmJust a quick question, have you tried it at over 600hz?Maybe a siggen? or if you need some oomph behind the siggen, feed it through an audio amp first.

author: necessaryevil
author_rank: Regular Contributor
timestamp: January 11, 2014, 12:01:10 pm
content: The LT4320 DIP version is available!I asked them about the DIP-version, it turned out that they simply forgot to set to flag the part as active! It's now on their website and it will be available on digikey soon.I made a 2 layer PCB design with the help of some people on a dutch forum. Should be able to handle 15 amps. I'll order a small batch on itead.

author: digsys
author_rank: Unknown
timestamp: January 11, 2014, 12:13:25 pm
content: Quote from: necessaryevilWell, that'll help with heat dissipation in the IC, and that slightly tricky thermal pad.Quote from: necessaryevilWith the FETs I've tested, max 2.5mR RDSon, 15A is a piece of cake. 16-20A and you start to need to think aboutsomeheatsinking.They should be good to 30A. I've only done short bursts to that, and all looked OK.

author: peter.mitchell
author_rank: Super Contributor
timestamp: January 11, 2014, 01:11:47 pm
content: hey digsys, have you tried it above 600hz?

author: digsys
author_rank: Unknown
timestamp: January 11, 2014, 01:15:38 pm
content: Quote from: peter.mitchellSorry no. I didn't buy the higher freq version, as I mainly work in 50-60Hz. But we do have some systems running 400Hz,so next test run.

author: peter.mitchell
author_rank: Super Contributor
timestamp: January 11, 2014, 01:47:27 pm
content: Quote from: digsys on January 11, 2014, 01:15:38 pmOk, doesn't particularly matter if you buy the high spec or not, I am more interested in this things limits, i already know mosfets are good high current switches.

author: necessaryevil
author_rank: Regular Contributor
timestamp: January 11, 2014, 08:15:11 pm
content: Quote from: digsys on January 11, 2014, 12:13:25 pmWell, I meant the PCBs could handle 15A (calculated, conservative settings)I use similar mosfets in my design. I did some hand written calculations and I came up with the same conclusion about heat sinking. Nice to have this conclusion confirmed.

author: digsys
author_rank: Unknown
timestamp: January 11, 2014, 10:08:13 pm
content: Quote from: necessaryevilDid you use 4oz Copper? Any other "tricks"? Exposed section/over-solder/silver-solder/wire over tracks?

author: digsys
author_rank: Unknown
timestamp: January 11, 2014, 10:16:32 pm
content: Quote from: peter.mitchellOK seems there's a mis-communication here :-). LT4320 is only rated to 60Hz LT4320-1 is rated to 600Hz. I didn't buy the xxx-1From the datasheet - "Higher frequencies of operation are possible depending on MOSFET size and operating load current"From my waveforms, I only saw very little degradation on gate drive when I pushed the FETs to 20A+, so I'd say if you stayunder ~10A, the max freq could be QUITE high.

author: BravoV
author_rank: Super Contributor
timestamp: January 12, 2014, 09:53:56 am
content: Quote from: peter.mitchell on January 11, 2014, 01:11:47 pmJust curious what are you looking for in using this chip way above it's specification ?

author: peter.mitchell
author_rank: Super Contributor
timestamp: January 12, 2014, 02:43:40 pm
content: Quote from: BravoV on January 12, 2014, 09:53:56 amMagic, rainbows, world peace, ect...But seriously, a high current, high speed, low loss rectifier would be amazing for lots of applications.

author: tszaboo
author_rank: Super Contributor
timestamp: January 13, 2014, 12:32:40 pm
content: I'm guessing that gate driving is what is the limit here. There are no external capacitors, so the internal charge pump only can supply so much current into the mosfet gate. So at higher frequency, it cannot close/open fast enough (especially at voltages like 72V) and efficiency drops. Now if only we would use MOSFETs with small gate capacitance and lower voltages...

author: danifel
author_rank: Newbie
timestamp: January 22, 2014, 03:02:42 pm
content: This is a chip built for PoE, to replace the 70V diode bridge present at every PoE Powered Device. But it is really not the best alternative around for this purpose. There is an Ideal Diode Bridge by Microsemi, PD70224, which is a lot more integrated.

author: tszaboo
author_rank: Super Contributor
timestamp: January 22, 2014, 06:46:46 pm
content: Quote from: danifel on January 22, 2014, 03:02:42 pmAnd also a future product. From a company which is not one of the few companies I would buy stuff from.

author: digsys
author_rank: Unknown
timestamp: January 22, 2014, 09:38:56 pm
content: Quote from: danifelI disagree with you here .. I don't see many PoEs needing to supply 20A without needing a heatsink.It's exactly what it says it is - a POWER Supply bridge rectifier replacement, and they are working out perfect in our products.Your PD70244 is NOT in the same ballpark. It's 1A (not 20A+), has 160mR inbuilt FETs (I'm using 0.9mR !!) AND it drives these10,000pF NFETs absolutely fine to 600Hz (and beyond IF I limit the current under 20A !!).. which is ALL I (we) need for DC rectification.I have no idea why you think it's for PoE

author: BravoV
author_rank: Super Contributor
timestamp: January 23, 2014, 02:19:01 am
content: Quote from: danifel on January 22, 2014, 03:02:42 pmCurious why you claim you know better than Linear Technology that designed it ? Reading the wrong datasheet maybe ?Fyi, Linear Technology made a lot of varieties of PoE ics, try visit their website once in a while. Not an expert, but I'm pretty sure they know what they're doing.

author: M. András
author_rank: Super Contributor
timestamp: January 23, 2014, 09:36:28 pm
content: i would love to see carry more then a few amperes by those ethernet cables

author: tszaboo
author_rank: Super Contributor
timestamp: January 23, 2014, 11:21:49 pm
content: Quote from: M. András on January 23, 2014, 09:36:28 pmIt is rated for 0.6AVoltage about 60-70V though.

author: M. András
author_rank: Super Contributor
timestamp: January 23, 2014, 11:28:29 pm
content: Quote from: NANDBlog on January 23, 2014, 11:21:49 pmsorry i meant to be sarcastic. i know their ratings flimsy little signal cables thats what they are for me

author: tszaboo
author_rank: Super Contributor
timestamp: January 23, 2014, 11:32:15 pm
content: Quote from: M. András on January 23, 2014, 11:28:29 pmOK, I should go to sleep. Jóéjt.

author: necessaryevil
author_rank: Regular Contributor
timestamp: February 07, 2014, 12:36:24 pm
content: Quote from: digsys on January 11, 2014, 10:08:13 pmThe only trick is that I use copper planes on both sides of the pcb. For the DC path I use about 2x300mil. The copper layers are only 1oz/ft^2. I'm not really going to use them for 15 amp, just a design goal.I used this calculator:http://circuitcalculator.com/wordpress/2006/01/31/pcb-trace-width-calculator/Some images:I just have sent the second version of my layout to Itead.I've received the v1 pcbs and got them working, but I realized that I made some misstakes. The holes for the input and output wires are too small and I forgot to connect one plane (resulting in current flowing through only one side of the pcb).//editlegenda:Green = bottom layerRed = top layerYellow = both layersthe white squares are for the wires. They have a 3.2 mm hole in them (m3 screw), which is not visible in the pictures.size: 50x50 mm (about 2"x2")

author: PerBuch
author_rank: Newbie
timestamp: February 27, 2019, 12:38:43 pm
content: Is I possible to buy a couple off your V2 boards ?

author: digsys
author_rank: Unknown
timestamp: February 27, 2019, 01:30:08 pm
content: A blast from the past :-) If you don't get any answer from mr evil, I should have heaps of several versions lying around. FOC .. was in the process of throwingout heaps of stuff anyway. Just let me know. Regular postage here is quite cheap.

author: PerBuch
author_rank: Newbie
timestamp: February 27, 2019, 01:57:34 pm
content: Is't it expensive to send from Australia to Denmark ? :-)

author: exe
author_rank: Unknown
timestamp: February 27, 2019, 03:26:51 pm
content: It's probably cheaper to order new boards from China.

author: digsys
author_rank: Unknown
timestamp: February 27, 2019, 09:41:51 pm
content: Quote from: PerBuchIf I can stuff it into a 260 x 360 x 20mm envelope (padded) ~ OZ$8-18 (125-500gmsElse package ~1Kg OZ $30 ishNot sure about your end taxes etc. Gift?