The product applications for synchronous rectification controllers include adapters, AC–DC power supplies including power supplies for servers, and a variety of DC/DC converters. Synchronous rectification is used to increase power supply efficiency by reducing the losses associated with output rectification. With SR the device that is being used for the output rectification is a MOSFET. Replacing a Schottky rectifier with a MOSFET results in lower power losses. The MOSFET is used with the SR controller commutating it on when the current would be flowing in the forward direction through the body diode, effectively synchronizing it with this event, hence the name. When the body diode would be reverse biased, the MOSFET is turned off and the reverse biased intrinsic body diode of the MOSFET then blocks reverse current flow. In the case of the non-synchronously rectified power supply, the power loss across the Schottky diode or rectifier is calculated by taking the voltage drop across it times the current (P loss =E (voltage) x I (current)). With the MOSFET, the voltage drop across it is the product of the current (I) times the on-resistance (Rdson), the power lost across it is the I-squared-R power loss of Rdson resistance of the MOSFET, or the MOSFET on-resistance times the current squared (P loss = I2 x R). The reason for using the MOSFET is that the channel on-resistance is quite low when it is fully saturated or fully turned on. This means it is going to provide a much lower power loss because the voltage dropped across the MOSFET will be lower than the forward voltage drop across a Schottky rectifier. That is why synchronous rectification is employed more and more in power supply designs, to significantly reduce the output rectification power losses and greatly improve the overall efficiency of the power supply. What ST has devised is a family of controllers that allow driving the MOSFETs the right way, so that they work as synchronous rectifiers.