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#1
02-23-2018
 Joshua_S micro ATX User Join Date: Feb 2018 Location: Japan Posts: 3 Thanks: 1 Thanked 0 Times in 0 Posts
Help needed with power losses calculation of a MOSFET's diode

Hello everyone, I'm currently trying to find out how much power will be lost during reverse recovery of a MOSFET's diode
( The effect of diode recovery http://www.apogeeweb.net/article/66.html).
I'm using this paper for reference,
https://www.fairchildsemi.com/applic...AN/AN-6005.pdf
the equation they end up with is
P= Qrr*Vin*Freq_sw
the problem is, for my application this gives an enormous number with the MOSFET I'm using.
I have: Qrr = 1.9uC Vin = 380V Freq_sw = 100,000Hz which gives us a total power loss of 72.2W.
My question is, does this seem right?
I can't believe that almost 100 watts will be lost in just the reverse recovery process...
My design output voltage is 300V using PWM. I figured I MIGHT have to multiply by the duty cycle (reverse recovery time * (frequency)) and this gives a much more reasonable answer, but I'm not sure if this is the correct way to go about it.

Any help is greatly appreciated!
#2
02-23-2018
 ashiekh 20W User Join Date: Oct 2017 Location: Grand Junction, CO Posts: 1,331 Thanks: 48 Thanked 95 Times in 87 Posts

Last edited by ashiekh; 02-24-2018 at 06:48 PM.
 The Following User Says Thank You to ashiekh For This Useful Post: Joshua_S (02-25-2018)
#3
02-25-2018
 Joshua_S micro ATX User Join Date: Feb 2018 Location: Japan Posts: 3 Thanks: 1 Thanked 0 Times in 0 Posts

That is very helpful, thanks friend.
#4
02-26-2018
 Username is valid micro ATX User Join Date: May 2017 Location: DE Posts: 10 Thanks: 0 Thanked 3 Times in 2 Posts

This looks right if you use a normal diode.
You must use a FR diode, then your power loss will remain in the acceptable range

 Tags mosfet, power losse

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