Soft-start with back bias conditions for PWM buck converter with synchronous rectifier

摘要

A circuit that efficiently prevents the turning on of the synchronous rectifier in a buck converter during a predetermined condition, so as to prevent current reversing through the synchronous rectifier during that time. In one embodiment, the circuit provides control of the synchronous rectifier during the soft-start time for a non-isolated DC-DC buck converter, thereby preventing current reversing (sinking), referred to as the back bias condition, during its soft start process. In another embodiment, a circuit uses a signal indicative of a soft-start condition for a converter to prevent the turning on of the synchronous rectifier during the soft-start time. A corresponding system solves the aforementioned synchronous rectifier back bias problem for converters used in a paralleled converter configuration.