Part Number: LM74680
Other Parts Discussed in Thread: CSD88537ND
I am using LM74680 in a 50Hz rectifier circuit with an output current of approximately 10A.
When using LM74680 with SQJ422EP or PSMN011-60MSX, I observed an abnormality in the input current waveform of the rectifier circuit.
As shown in the figure below, a significant reverse current appears at the moment when the rectifier circuit should be in the cut-off state, followed by a rapid cut-off with ringing.
This reverse current generates considerable noise in my circuit, and it greatly limited the range of application. I would like to know how to control or avoid this issue.
Here's my circuit using PSMN011-60MSX. Its Ciss and Qg are higher than CSD88537ND. And there's no difference when using SQJ422EP with Ciss and Qg even higher than PSMN011-60MSX.
I think there're some problems in the operation of the Regulated Conduction Mode. It should be able to gradually turn-off the MOSFET to maintain forward voltage drop of 11mV in Regulated Conduction Mode. When OUTP-GND is higher than |IN1-IN2| , the Rds should be already quite high and little reverse current can go through the channel. But the situation is actually not the same as described.
