Do you understand the soft recovery characteristics and hard recovery characteristics of diodes?

Do you understand the soft recovery characteristics and hard recovery characteristics of diodes?

The interference generated by the output rectifier diode has a reverse current when the output rectifier diode is cut off, and the time it takes to recover to zero is related to factors such as junction capacitance. The secondary transistor that can quickly recover the reverse current to zero is called a hard recovery characteristic diode. This type of diode will generate strong high-frequency interference under the influence of transformer leakage inductance and other distribution parameters, with a frequency of up to tens of MHz.

The diode with a short reverse recovery process is called a FastRecovery Diode. High frequency power electronic circuits require fast recovery diodes with short reverse recovery time, low reverse recovery charge, and soft recovery characteristics.

All PN junction diodes will store charges in the form of minority carriers when conducting forward current. Minority injection is the mechanism of conductivity modulation, which leads to a decrease in forward voltage drop (VF). In this sense, it is advantageous. However, when reverse voltage is applied to the conducting diode, due to the large number of minority carriers stored in the base region during conduction, it takes some time to completely extract or neutralize these minority carriers at the cut-off point. That is, the recovery of reverse blocking ability takes a period of time, which is the reverse recovery process. The time taken for this process to occur is defined as the reverse recovery time (TRR).