Parasitic capacitance across switch

Thread Starter

anhnha

Joined Apr 19, 2012
881
Could anybody explain this more?
Why there is a voltage spike during turn-off period?
Also how it decrease the crossover loss?

Parasitic capacitance.PNG
 

RRITESH KAKKAR

Joined Jun 29, 2010
2,829
I think when the switch is in off position suddenly there is increase in resistance than of conductor because the medium is air now.
so, the molecule get energized and leave some spark especially in DC!
 

Jony130

Joined Feb 17, 2009
5,180
If you don't know the answer now. Do not worry, in chapter 5 you will find more about this crossover losses.
As for the spike what about parasitic inductance?
 

Thread Starter

anhnha

Joined Apr 19, 2012
881
I think when the switch is in off position suddenly there is increase in resistance than of conductor because the medium is air now.
so, the molecule get energized and leave some spark especially in DC!
Thanks but actually I need a more detailed answer.

If you don't know the answer now. Do not worry, in chapter 5 you will find more about this crossover losses.
As for the spike what about parasitic inductance?
Thanks Jony. I am waiting for the chapter!
For inductance it is easier to understand. Because VL = L di/dt, so when switch changes from OFF to ON (here di is large while dt is small) VL is large.
 

crutschow

Joined Mar 14, 2008
25,259
Could anybody explain this more?
Why there is a voltage spike during turn-off period?
.............................
Any voltage spikes are generated by the stray circuit inductance. This inductance tries to keep the current flowing, generating a spike when this flow is interrupted by the switch.
 
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