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How to optimize delayed Turn-off with SRK2000

Question asked by Klammer.Stefan on Mar 22, 2017

Hello everybody,


I'm working on a power supply with a LLC Stage in it. The LLC has following specifications:


Uin: 385V

Uout: 28V

Iout: 5.75A

Switching Frequency: 300kHz


For the secondary side rectification I want to use a SRK2000A but i have the Problem with a delayed Turn-off of the synchronous rectifier MOSFet's. My selected Turn_off_threshold is 25mV. In the attached Picture you can see in yellow the output of the SRK2000A in red the secondary current in blue the Vds over the MOSFET and in green the resonant current. My schematic is like in the Datasheet but with RD=2kohm. At the High output current of 5.5A the time between the SRK2000A turns off the MOSFET and the current in the MOSFET gets negative is only about 40ns. So there is only a little margin to current reversal. Has anybody an idea to get a smaller delay? Or would it be better if i use a SRK2001?


I'm grateful for any help,

Best regards