Why is it that in a synchronous rectifying DC/DC converter with a high/low-side Nch MOSFET configuration, MaxDuty is limited and cannot be 100%?|FAQ|ROHM Semiconductor

ROHM FAQ

FAQ's

Why is it that in a synchronous rectifying DC/DC converter with a high/low-side Nch MOSFET configuration, MaxDuty is limited and cannot be 100%?
- The high side Nch MOSFET requires a bootstrap circuit for on operation, and in order to charge the step-up capacitor of this circuit with electric charge, the low side MOSFET must always be on with the switching pin in the "L" state. Because this interval (time period) is necessary, a limit on MaxDuty occurs, and it can never be 100%.