How is the reverse recovery time of a fast recovery diode defined?

How is the reverse recovery time of a fast recovery diode defined?

Definition of reverse recovery time (tr) of fast recovery diode: the time interval during which current transitions from forward to a specified low value through the zero point. It is an important technical indicator to measure the performance of high-frequency freewheeling and rectifying devices.

In the fast recovery diode, IF is the forward current and IRM is the maximum reverse recovery current. Irr is the reverse recovery current, and Irr=0.1IRM is usually specified. When t≤t0, forward current I=IF. When t>t0, the forward current decreases rapidly because the forward voltage on the rectifying device suddenly changes to the reverse voltage. At t=t1, I=0. Then a reverse current IR flows through the rectifying device, and IR gradually increases; the maximum reverse recovery current IRM value is reached at t=t2.

After that, due to the action of the forward voltage, the reverse current gradually decreases and reaches the specified value Irr at t=t3. The reverse recovery process from t2 to t3 is similar to the capacitor discharge process. It can be seen that parameters such as reverse recovery time form a gap between fast recovery diodes and ordinary rectifying diodes.