Synchronous rectifier MOSFETs

Selection of the power switch and synchronous rectifier MOSFETs... 

For those applications where high efficiency is important, synchronous rectification may be used on the higher current (power) outputs. Synchronous rectifier circuits are much more complicated than the passive 2-leaded rectifier circuits. These are power MOSFE B, which are utilized in the reverse conduction direction where the anti-parallel intrinsic diode conducts. The MOSFET is turned on whenever the rectifier is required to conduct, thus reducing the forward voltage drop to less than O.f V. Synchronous rectifiers can be used only when the diode current flows in the forward direction, that is in continuousmode forward converters. 

With the development of digital ICs operating on low voltage (of the order of 3 V) supplies, the use of MOSFETs as synchronous rectifiers with very low voltage drop (= 0.2 V) has become essential (Motorola, 1989) to increase the efficiency of the DC-to-DC converter. 

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