Replacement for this suppressor diode? - Page 1
Forum section: electronics / repair

author: iXod
author_rank: Frequent Contributor
timestamp: February 04, 2017, 08:07:06 pm
content: BZW06-26 "voltage suppressor diode", 26v. It's now obsolete, "n/a".http://diotec.com/tl_files/diotec/files/pdf/datasheets/bzw065v8It's used in a circuit to protect a PWM switching MOSFET from the 3 SSRs it drives. It's shorted.I just found this P6KE20A "direct replacement" [sic, Mouser] by Fairchild/ON Semi:http://www.mouser.com/ds/2/149/P6KE30A-1011841.pdfLooks good.Since I prefer something available locally, would a general purpose zener work as a replacement? Or...?Thanks.

author: Ian.M
author_rank: Super Contributor
timestamp: February 04, 2017, 08:13:23 pm
content: A Zener is likely to be too slow and wont have the pulse power handling capability. Its a TVS diode - Google: 600W unidirectional TVS diode 26V

author: iXod
author_rank: Frequent Contributor
timestamp: February 04, 2017, 08:25:05 pm
content: OK, no zeners.Looks like Littelfuse makes the SA26A, also an equivalent:http://www.mouser.com/ProductDetail/Littelfuse/SA26A/?qs=sGAEpiMZZMssaSaMl4au6L3OgECLgVJGThanks.

author: Ian.M
author_rank: Super Contributor
timestamp: February 04, 2017, 08:32:29 pm
content: As its for a PWM application, make sure you match the steady state power dissipation. Your candidate is 3W, but the original was 5W.You may have to go up a bit on the peak pulse rating to find more candidates that can do 5W steady state - I'd select 600W - 1200W pulse rating in any distributor's parametric search.

author: iXod
author_rank: Frequent Contributor
timestamp: February 06, 2017, 04:33:34 am
content: Quote from: Ian.M on February 04, 2017, 08:32:29 pmThanks for the warning.Sounds good.This Littlefuse product is 600W rated:http://www.digikey.com/product-detail/en/littelfuse-inc/P6KE30CA/P6KE30CALFCT-ND/285941Both the original and the Littelfuse products are rated 600W but the peak current is 75A for the original and only 14A for the Littelfuse. I don't see how there can be such a wide delta for these similar (in W spec) devices.What am I missing?Cheers.

author: Ian.M
author_rank: Super Contributor
timestamp: February 06, 2017, 05:09:15 am
content: Is it rated over the same pulse duration? (I haven't compared the datasheets)When you get down to it, its all a matter of how much energy the Silicon junction can absorb without either melting, or as the energy pulse dissipates, melting its die attach solder. The energy capacity will be almost directly proportional to the mass of silicon for short pulses. For longer pulses, the leadframe's ability to heatsink the die comes into play. If the Diotec part had a larger die area, but the die was thinner, it could easily have higher peak current handling capability, while still only handling the same pulse energy.Alternatively Diotec may have been better at getting a uniform junction that resists 'hotspotting' which would cause local failure.

author: iXod
author_rank: Frequent Contributor
timestamp: February 06, 2017, 07:10:17 pm
content: Quote from: Ian.M on February 06, 2017, 05:09:15 amThe original datasheet says that the 600W peak pulse power is measured over 10/1000 uS waveform, but the 100A forward surge current is spec'd over 1/2 cycle of a 60 Hz sine:http://diotec.com/tl_files/diotec/files/pdf/datasheets/bzw065v8All replacements I see, the surge current is nowhere near 100A and spec'd at 10/1000 uS waveform.Surely the original isn't all that unique a part...? Anyone see a replacement part?Thanks.

author: Ian.M
author_rank: Super Contributor
timestamp: February 06, 2017, 09:18:32 pm
content: Errr . . . . you are comparing apples to oranges!*BOTH* the original Diotec BZW06-26 and the Littelfuse P6KE30A have a IFSMof 100 A,FORWARDcurrent measured over one half cycle of 60Hz sinewave. Their peak REVERSE surge currents for the 10/1000us waveform are 14.5A @41.5V and 14.7A @41.4V, with the same standoff voltage so it should be a drop-in replacement.N.B you do *NOT* want the bidirectional version you linked to. Try:http://www.digikey.com/product-detail/en/littelfuse-inc/P6KE30A/P6KE30ALFCT-ND/285939