Ultra fast rectifier
Ultra fast rectifier
(OP)
Hi all.
Is it possible for something to cause a ultra fast semiconductor rectifier diode to a temporarily act as a short and allow reverse current flow? Temperature, Voltage transient, etc.?
I have some diodes that were claimed to be allowing reverse voltage for an extended period of time (1-5 seconds minimum). Short of sending the diodes out for an optical analysis, I do not see anything wrong. I have little to zero knowledge of the application or environment this happened in.
I understand this is a broad question. I am just looking for a place to start.
Thank you All.
Is it possible for something to cause a ultra fast semiconductor rectifier diode to a temporarily act as a short and allow reverse current flow? Temperature, Voltage transient, etc.?
I have some diodes that were claimed to be allowing reverse voltage for an extended period of time (1-5 seconds minimum). Short of sending the diodes out for an optical analysis, I do not see anything wrong. I have little to zero knowledge of the application or environment this happened in.
I understand this is a broad question. I am just looking for a place to start.
Thank you All.
RE: Ultra fast rectifier
RE: Ultra fast rectifier
Thank you.
Checking it with a MM shows good, both as an ohm meter and using the diode check setting. It is also acting as it should in the circuit. What ever happened, (if something happened) was temporary. So I am asking more on a theoretical level is there something that could cause reverse current flow (full short), cause no damage to the diode, and revert back to acting as it should?
Low impedance circuit, relatively small semiconductor, roughly 5mA leakage Max. Wouldn't cause what was claimed to have seen.
RE: Ultra fast rectifier
RE: Ultra fast rectifier
es3d
http://www.vishay.com/docs/88589/es3.pdf
RE: Ultra fast rectifier
It like all others will Zener breakdown and flow backwards if the reverse voltage gets high enough.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Ultra fast rectifier
For it to act how it was described to me. It would have to be leaking at least 500mA for an extended period of time, and then act normal again. As I said I do not see a problem with it, so I am asking on a theoretical level, is this something that is possible? If it is operating in the breakdown region, especially for an extended period of time, its my understanding that the diode will be damaged and not recover.
RE: Ultra fast rectifier
Dan - Owner
http://www.Hi-TecDesigns.com
RE: Ultra fast rectifier
The Germans have a wonderful word for it: "Trägerstaueffekt"
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Ultra fast rectifier
MacGyverS2000
Haha I would love to tell them that... but I also would like them to keep buying the product.
Skogsgurra
Thank you
Like I said I see nothing wrong with the diode, nor do I have an understanding on how this could happen. The product, as returned, was completely functional. I just wanted to throw the question out there to some Electrical Engineers in case I was missing something. It is more probable than not that the customer misdiagnosed the issue.
RE: Ultra fast rectifier
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RE: Ultra fast rectifier
Forward current draws roughly 700mA MAX, typically 350mA where the rectifier is rated for 3A.
The reverse bias is 24 VDC.
RE: Ultra fast rectifier
if the voltage is high enough the TVS will conduct for as long as the voltage is high.
5 seconds is NOT reverse recovery
RE: Ultra fast rectifier
Chuck
RE: Ultra fast rectifier
The current is still no more than 1mA, which is typically where most diode reverse breakdown specs occur, so there is no reason or need for a higher voltage. Moreover, a 30kV potential, particularly applied as a pulse is tantamount to an ESD zap, especially with the ability to dump milliamp level currents. Such conditions can damage some diodes.
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RE: Ultra fast rectifier
Chuck
RE: Ultra fast rectifier
Chuck
RE: Ultra fast rectifier
RE: Ultra fast rectifier
That depends on the diode. Some devices are damaged immediately, but the consequences are not revealed for some number of power cycles. TTL emitter diodes are like that; they can get damaged, but it takes some time before they completely go bad, as each iteration of junction current further drives that aluminum spike into the junction, until it's eventually shorted out for good, or bad...
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RE: Ultra fast rectifier
RE: Ultra fast rectifier
there is no such thing in this diode that with 24V you can get 5 seconds of reverse current.
what happens after 5 seconds? The data you are giving us is faulty or the diode is broken and should be replaced with another of the same part number.
I have used these diodes in several switching power supplies. if you have 5 seconds of reverse current in a rectifier circuit the transformer will burn up because you are making a short across the winding.