Diode voltage ratings - Page 1
Forum section: electronics / projects

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 21, 2022, 02:45:22 am
content: A Dave tweet caught my eye:https://twitter.com/eevblog/status/1484040136359030786decided to do a little survey of my collection.Code:Avalanche (V) @ 0.1mANew ON Semi 1N400413811480135013651490Diodes 1N4004155016361630MCC 1N4004153115301530Good-Ark 1N4004181016401750Fairchild 1N4007157017601625New Fairchild 1N4007>= 1610 (N=6)Unknown H1B1201460Unknown (negative block around diode symbol logo) 1N40051203General Semi 1N40071540Good-Ark 6A11175TJ4245AKK1536Glass 1N4003 'R'852QNJX5552800mu6 1N40011330ON Semi 1N40011347120716001270Diodes 1N4001363I did not take Vf measurements unfortunately, but we can expect them to correlate with Vbr.I have also measured a variety of FWBs (at 1mA) with similar results: the lowest was a Shindengen D4SBL40 at 545V, with "600V" parts typically passing over 1000, "800V" parts a bit over 1200, and the highest of that sample was a General Instruments GBPC3506W at 1485V.Tim

author: floobydust
author_rank: Super Contributor
timestamp: January 21, 2022, 04:18:12 am
content: We've discussed this before:https://www.eevblog.com/forum/projects/testing-1n4007-with-a-megger/https://www.eevblog.com/forum/beginners/diode-voltage-vs-forward-voltage/https://www.eevblog.com/forum/beginners/1n400x-diodes/How old is this diode anyway? Went on a hunt and it seems to bereleased by Motorolaend of 1963 when the glass passivation surmetic plastic package rolled out.Today, itissilly to have silicon diodes with 50V or 100V differences yet at the same price as the top 1,000 PIV part. I have to wonder what the need is for SO MANY DIFFERENT DIODES. Modern diode die construction seems to be optimized, from the old days, I rarely see Vf and speed ranked differently due to PIV.

author: bob91343
author_rank: Super Contributor
timestamp: January 21, 2022, 04:26:55 am
content: There could be a number of reasons. Perhaps retrofit old parts lists. Or maybe the forward voltage and/or dynamic resistance correlates with breakdown voltage. Or the product review people question the specification of a 1000V diode where a 200V is sufficient. Or allow for a way to sell diodes in case some don't have such a high breakdown.

author: PartialDischarge
author_rank: Super Contributor
timestamp: January 21, 2022, 04:53:52 am
content: Quote from: floobydust on January 21, 2022, 04:18:12 amWell unless you can demonstrate that all specs are the same, I do see a need, a diode is not just a piv.It’s forward recovery, reverse recovery, peak power handling, capacitance, Vf, leakage current, packaging...

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 21, 2022, 05:20:06 am
content: I'm not concerned about reasons; that much is obvious -- laziness, why produce inferior parts when one or two will handily meet all the ancient JEDEC requirements?So, as far as that's concerned, the fault is sticking with an ancient type number.It does look like there may be actual low-voltage parts out there. Compare these for example:https://fscdn.rohm.com/en/products/databook/datasheet/discrete/diode/fast_recovery/rf101lam2s-e.pdfhttps://fscdn.rohm.com/en/products/databook/datasheet/discrete/diode/fast_recovery/rf101lam4s-e.pdfhttps://fscdn.rohm.com/en/products/databook/datasheet/discrete/diode/fast_recovery/rfn1lam6s-e.pdfhttps://fscdn.rohm.com/en/products/databook/datasheet/discrete/diode/fast_recovery/rfn1lam7stf-e.pdfNote these are in pairs; the RF101 series ends at 400V, and the RFN1 series picks up at 600V. The latter is slightly lower current, so they're not exact, but as apple-based comparisons go, it looks more like Mcintosh vs. Fiji, not like Golden Delicious vs. crab apple.Anyway, it would be very difficult for a max 0.87V part to also be a min 0.8V part.These are high-speed diodes, so there is the additional optimization pressure of recovery time. Which probably explains the existence of this series, among others. (Not all do; MUR1x0 for example divide into two ranges, it seems.)I found these parts by searching DK for minimal Vf, excluding schottky (a few SS14, etc. still snuck through -- improperly labeled, I suppose I should hit the "report an error" button but it's fairly minor honestly). No general-purpose parts fell through the filter, so it seems very little optimization is possible with them -- or at least worthwhile. And given the measurements, it seems likely there's another pressure at play, namely that they handle rated AC Vrms, not just PIV; or not just that but surge as well (note that most of these "600V" parts will withstand 2.5kV surge if paired with a MOV of nominal rating!).Other comments; I noticed on several diodes, the breakdown voltage drifted upward noticeably -- and not due to heating, at this low current. Almost like there's defects that can be "reformed" like electrolytics? Weird. Maybe surface states?Also found two Diodes parts that failed when I tested them; I might've left the test voltage too high and they popped at a few mA, or maybe a few A transient (for some ~ns as node capacitances discharge), whoops. Or maybe they were already dead. Observation was a two-way short, in any case.Quote from: MasterTech on January 21, 2022, 04:53:52 amForward recovery too! Rarely listed, fortunately it's usually pretty small, but can be unexpectedly substantial sometimes. Would also be interesting to see a survey of that across parts both current and historic. Another time, perhaps.Oh, another characteristic that varies, as can be seen in the above links: surge rating varies with Vf and die volume. So it makes sense the higher voltage parts handle less peak current.Tim

author: PartialDischarge
author_rank: Super Contributor
timestamp: January 21, 2022, 05:35:58 am
content: Quote from: T3sl4co1l on January 21, 2022, 05:20:06 amI spent some time testing diodes for low forward rec for a specific application. And go figure, the shittiest general purpose rectifier diode from a fairly unknown brand gave the best results, and all the fastest power electronics stuff were bad

author: floobydust
author_rank: Super Contributor
timestamp: January 21, 2022, 06:04:12 am
content: Take an antique diode like 1N400x or 1N540x and semiconductor manufacturers just copy the same datasheet specs from somewhere ancient. They seem scared to add something and be different from other manufacturers and have engineers run away and not specify them lol. You won't find a reverse-recovery spec for example.Diodes Inc. 1N4001-4007shows a difference for 1N4005-4007 half the junction capacitance.I'd swear Vf @ 1A is going up over the years...1N400x obsolete now, replaced by SMA/SMBS1A-S1Mand the same 50/100/200...1,000 PIV variants offered with the same kooky pricing. Let's continue the tradition. The datasheet has trr, and many differencesVishay S1A-S1Mdatasheet at 800V and 1,000PIV, thermal resistance too.Something is different with the higher voltage parts, but we're still carrying old sloppy datasheets or JEDEC is in a time machine. Or everyone actually has a different diode technology and are making it look the same.

author: David Hess
author_rank: Super Contributor
timestamp: January 21, 2022, 10:57:30 pm
content: Conductance is lower and reverse recovery is higher for higher voltage diodes. Higher voltage parts may also use a PIN structure.