Synchronous rectifier MOFSET with controlled channel voltage drop

Abstract

A synchronous rectifier MOSFET control circuit which overcomes many of the shortcomings of the prior art employs MOSFET for supplying voltage to a load when the MOSFET is in the forward biased condition (i.e., when an input voltage level exceeds the threshold voltage level by a pre-determined amount). The MOSFET control circuit is configured to turn off the MOSFET when the input voltage level dips below that pre-determined level required to maintain the MOSFET in the forward biased condition. When the MOSFET is turned off, the diode internal to the MOSFET device prevents current flow in the reverse bias direction (i.e., the internal diode prevents current flow from the output to the input), effectively isolating the load from the input voltage source, thereby allowing the capacitors to discharge their energy to the load to maintain a voltage supply to the load which is at or above the output load threshold voltage level. Thus, although a diode is still employed to prevent current flow in the reverse direction, the diode need not function to supply the current to the load when the MOSFET is in the forward biased direction. Rather, current flows through the MOSFET channel (as opposed to flowing through the diode) when the MOSFET is in the forward biased condition.

Dependencies are inferred from the claim text.