Hi there,
could anyone explain me what the avalanche current of a Mosfet is?
How come some mosfets have 50A nominal and 50A Avalanche current,
others 50A nominal and only 25A avalanche c.?
all i could think of is pulse peak current, but that's given separately and beyond 100A.
or Is it the current the diode between S and D can stand?
tanks you.
could anyone explain me what the avalanche current of a Mosfet is?
How come some mosfets have 50A nominal and 50A Avalanche current,
others 50A nominal and only 25A avalanche c.?
all i could think of is pulse peak current, but that's given separately and beyond 100A.
or Is it the current the diode between S and D can stand?
tanks you.
The avalanche effect appears in a (heavilly) reverse biased PN junction, like the zener effect of you want
here's some info
http://www.tpub.com/neets/book7/26.htm
here's some info
http://www.tpub.com/neets/book7/26.htm
sorry, thats too difficult english for me.
All i need to know is: Can i replace a smps mosfet that had 50A avalanche current in the datasheet with one that has only 25A?
All other data of the devices is nearly the same.
All i need to know is: Can i replace a smps mosfet that had 50A avalanche current in the datasheet with one that has only 25A?
All other data of the devices is nearly the same.
I would say it depends on if it uses it or not... I doubt it does so it's probably okay. If it isn't, then it doesn't have a good snubber (if any at all). 😀
Tim
Tim
I don't know much about smps power supplies, but I don't think it uses the fet's avalanche current.
andey, I'm not totally sure but picture this:
The mosfet has a built-in zener across drain and source. This zener can take shortly 50 A. Of cource this zener isn't a zener, it's when the mosfet can't take any higher voltage and lte current through.
This parameter is not important in linear applications such as a normal power amp or a linear power supply.
Did you get any wiser?
The mosfet has a built-in zener across drain and source. This zener can take shortly 50 A. Of cource this zener isn't a zener, it's when the mosfet can't take any higher voltage and lte current through.
This parameter is not important in linear applications such as a normal power amp or a linear power supply.
Did you get any wiser?
I don't know what I told about smps. 😕
If it's for a linear power supply pass element, go for the 25A one
If it's for a linear power supply pass element, go for the 25A one
Back to the 50A/25A question, it was mentioned that it is ok to use the 25A unit in normal power amp. What about used in power supply of digital amp? Does it matter?
andey:
You have to understand first what happens when inductive loads are switched on and off. Then, understanding avalanche ratings will be very easy.
Anyway, the replacement will probably be fine as most SMPS circuits either doesn't create avalanche conditions at all, or produce relatively small avalanche energies in comparison with device ratings.
You should check other important data like gate capacitance and on resistance in order to ensure a good replacement, though.
You have to understand first what happens when inductive loads are switched on and off. Then, understanding avalanche ratings will be very easy.
Anyway, the replacement will probably be fine as most SMPS circuits either doesn't create avalanche conditions at all, or produce relatively small avalanche energies in comparison with device ratings.
You should check other important data like gate capacitance and on resistance in order to ensure a good replacement, though.
ok,that draw my attention,the input capacitance on the replacement is 1000pf as compare to 2440pf and On resistance on the replacement is 0.35 0hm as compare to 0.5 ohm.What's the significance here?
The replacement may switch faster depending on the gate driver circuitry becuase less charge (coulombs) is required. The lower value of Rds-on is a good thing.
😉
😉
Hey Guys,
the thread is over one year old. In other words - my amp works fine with the 25A av.curr. mosfets for over one year 😀
I know what happens when an Inductive Load is switched off, but i really didn't want to shoulder all the circumstances to measure out how much inductive-switch-off current may appear in my SMPS... if i would have gotten measuring done at all...
thanks anyway for all help i got here!
the thread is over one year old. In other words - my amp works fine with the 25A av.curr. mosfets for over one year 😀
I know what happens when an Inductive Load is switched off, but i really didn't want to shoulder all the circumstances to measure out how much inductive-switch-off current may appear in my SMPS... if i would have gotten measuring done at all...
thanks anyway for all help i got here!
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