Power Diodes Flashcards
Where do losses occur in these diodes?
During the change between the on and off state, because there is both voltage and current present this can lead to losses.
What is the Reverse Recovery region?
It is the region where the diode will begin to conduct in the reverse region after it has been turned off because the diode doesn’t stop conducting immediately.
What is Irr?
It is the peak reverse current and is the max value that the current will reach in the reverse region.
What is trr?
It is the time taken from when the forward current falls to zero and then dips to its max Irr and then recovers to 25% of its peak value.
What is the equation for Irr?
Irr = trr * DIr / Dt
What is the snappiness factor and its equation?
It is an indicator of how fast Irr decays back to zero.
S = t2 / t1.
What is t1?
It is the time taken from when the current = 0 to it reaching its peak Irr.
What is t2?
The time taken to go from Irr back to 25% of the peak value.
How can we express t1 as a function of trr and S?
t1 = trr - t2 = trr / (S + 1)
What is the reverse recovery charge equation?
It is approximately the area enclosed by the triangle.
Qrr = trr^2 / 2(S + 1) * DIr / Dt
What does it mean if we have a high snappiness factor?
We will get large oscillations on the recovery.
What is the equation for the reverse recovery losses?
Prr = Vr * Qrr * fs
Vr is the reverse blocking voltage, fs is the switching frequency and Qrr is the reverse recovery charge.
What is the equation for the conduction loss?
Pc = Vf * Id(avg)
For a Buck converter: Pc = (1-D)Vf * IL (avg)
