How much frequency are used to fast recovery diodes?

Whereas rectifier diodes are used in sub-500 Hz applications, FRDs are used in several kHz to 100 kHz switching.

Fast Recovery Diodes (FRDs) have the same withstand voltage as rectifier diodes, short reverse recovery time (trr), and low reverse recovery current. Loss due to recovery current is called switching loss. Since this recovery current and reverse recovery time are almost constant, the higher the frequency, the higher the ratio of switching loss to the total loss.
It is used in applications from several kHz to 100 kHz at voltages at which Si Schottky barrier diodes (Si-SBDs) cannot be used (reverse bias applied to the diode is several tens of V or more).
It is suitable for use in switching power supplies, inverters and DC-DC converters.

Fig. 1 Diode switching waveform and loss, Fig. 2 Comparison of rectifier diode and RFD reverse recovery current (ON ⇒ OFF transition period)

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