Author Topic: Replacement for this suppressor diode?  (Read 767 times)

0 Members and 1 Guest are viewing this topic.

Offline iXod

  • Regular Contributor
  • *
  • Posts: 223
Replacement for this suppressor diode?
« on: February 04, 2017, 08:07:06 pm »
BZW06-26 "voltage suppressor diode", 26v. It's now obsolete, "n/a".

http://diotec.com/tl_files/diotec/files/pdf/datasheets/bzw065v8

It'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.pdf

Looks good.

Since I prefer something available locally, would a general purpose zener work as a replacement? Or...?

Thanks.
« Last Edit: February 04, 2017, 08:17:04 pm by iXod »
 

Offline Ian.M

  • Super Contributor
  • ***
  • Posts: 7838
Re: Replacement for this suppressor diode?
« Reply #1 on: February 04, 2017, 08:13:23 pm »
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
 

Offline iXod

  • Regular Contributor
  • *
  • Posts: 223
Re: Replacement for this suppressor diode?
« Reply #2 on: February 04, 2017, 08:25:05 pm »
OK, no zeners.

Looks like Littelfuse makes the SA26A, also an equivalent:

http://www.mouser.com/ProductDetail/Littelfuse/SA26A/?qs=sGAEpiMZZMssaSaMl4au6L3OgECLgVJG

Thanks.
 

Offline Ian.M

  • Super Contributor
  • ***
  • Posts: 7838
Re: Replacement for this suppressor diode?
« Reply #3 on: February 04, 2017, 08:32:29 pm »
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.  ;)
« Last Edit: February 04, 2017, 08:35:47 pm by Ian.M »
 

Offline iXod

  • Regular Contributor
  • *
  • Posts: 223
Re: Replacement for this suppressor diode?
« Reply #4 on: February 06, 2017, 04:33:34 am »
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.  ;)

Thanks for the warning. :) Sounds good.

This Littlefuse product is 600W rated:

http://www.digikey.com/product-detail/en/littelfuse-inc/P6KE30CA/P6KE30CALFCT-ND/285941

Both 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.
 

Offline Ian.M

  • Super Contributor
  • ***
  • Posts: 7838
Re: Replacement for this suppressor diode?
« Reply #5 on: February 06, 2017, 05:09:15 am »
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.
« Last Edit: February 06, 2017, 05:12:50 am by Ian.M »
 

Offline iXod

  • Regular Contributor
  • *
  • Posts: 223
Re: Replacement for this suppressor diode?
« Reply #6 on: February 06, 2017, 07:10:17 pm »
Is it rated over the same pulse duration?  (I haven't compared the datasheets)...

The 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/bzw065v8

All 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.
 

Offline Ian.M

  • Super Contributor
  • ***
  • Posts: 7838
Re: Replacement for this suppressor diode?
« Reply #7 on: February 06, 2017, 09:18:32 pm »
Errr . . . . you are comparing apples to oranges! :palm:
*BOTH* the original Diotec BZW06-26 and the  Littelfuse P6KE30A have a IFSM of 100 A, FORWARD current 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
 
The following users thanked this post: iXod


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf