The fast recovery rectifier diode is very hot. Even if you replace the fast recovery rectifier diode with a higher power, it is still very hot. In this case, it is recommended that you use the ultrafast recovery rectifier diode, because the current signal frequency is high, and the current is the effective value. There may be high-frequency components in the signal, and the peak current is far more than 2A you measured, which leads to the extremely high peak power of the diode, and the speed of the fast recovery rectifier diode cannot keep up, So the tube of fast recovery rectifier diode will become very hot.