diode reverse recovery time

[chepot]

reverse recovery time

my diode datasheet (BYT56) state that it's trr=100ns.
the test condition is: IF=0.5A, IR=1A, iR=0.25A.

i'm going to use it on my circuit at IF=3A.
is it's trr still the same (100ns)?
if not, how to calculate it?[/code]

 

[dipnirvana]

diode reverse recovery

with increase in IF , there will be an increase in Trr also. It would not remain same .

 

[chepot]

dipnirvana, do you know what formula to calculate trr as IF increase ?

 

[isurug]

reverse recovery time of diode

it depends on how fast you are switching.. trr means that
in Maxim website:
Definition
When switching from the conducting to the blocking state, a diode or rectifier has stored charge that must first be discharged before the diode blocks reverse current. This discharge takes a finite amount of time known as the Reverse Recovery Time, or trr. During this time, diode current may flow in the reverse direction.

so the charge is constant.. (Qrr)
thus Trr = sqrt(2*Qrr/(di/dt))

=> if you switch higher current for the same dt, Trr infact reduces.

 

[chepot]

qrr diode

hi, isurug
I'm newbie to electronic. i hope you can give me more detailed help.

switching frequency is 25KHz
Tperiode = 40us
Ton = 5us ---> is this dT ?
i don't know about Tdelay, Trise or Tfall (newbie)

how to determine Qrr?

I googled and fine this formula trr = Ts + Tt.
but back again i don't know how to determine Ts & Tt

 

[isurug]

reverse recovery time diode

Hi chepot,

Qrr = Irr X trr approximately. in ur case Qrr= 1A X 100ns which is a rough estimation. di/dt really depend on your current path eg. if theres an inductor di/dt=v/L etc. thus to have a precise value, u need to simulate. but the bottom line is the max trr =100ns and any deviations in the device performance only differ slightly. in ur freq of operation trr deviation is negligilbe. so u can safely assume trr to be constant at worst case to be 100ns. Infact, calculations of electronics always assumes and approximates =) dont bother about these values when ur sure that ur in well in the device operating range

-Isurug

 

[chepot]

trr diode

isurug, sorry if i'm too slow to understand :roll:

the first equation you gave me to calculate trr:

trr = sqrt(2*Qrr/(di/dt))

i can't finish the equation, because i don't know the value of Qrr, di, dt.

then you gave me the equation to calculate Qrr:

Qrr = irr * trr.

in my point of view, it's impossible to finish the equation.
lets say I know the value of irr, then the last thing I need is trr value then Qrr will be known.
but to find trr value I must know the value of Qrr ( first equation).

a loop ????


well since I'm not to bright, i'm also considering you suggestion to use assumes or approximates.
as you said max. trr=100ns

BYT56 diode has Ipeak foward surge current=80A, it's max. trr still 100ns??

 

[isurug]

recovery time diode

hi chepot,

Trr=sqrt(2*Qrr/(di/dt))
I approximated Qrr with the given data, which is a good estimation. now you still cannot get Trr, unless you know di/dt. that is what i was telling. suppose that you know di/dt (which is very hard to get an accurate value due to dependancies) then u can obtain a value to Trr.
what i was tellin was that, even if you found Trr going thru all the trouble, the trr only will differ slightly in your operating freq range.

about the surges. diodes only can last surges momentarily. then for greater di/dt (eg. 80A/1ns) Trr will be low.