2. Schottky Rectifier
Surface Mount Devices
Introduction to Schottky Rectifier :
Schottky rectifiers have been used for over 25 years in the power supply industry. The primary advantages are very low forward voltage drop and switching speeds that approach zero time making them ideal for output stages of switching power supplies. This latter feature has also stimulated their additional use in very high frequency applications including very low power involving signal and switching diode requirements of less than 100 picoseconds. These require small Schottky devices with low capacitance.
The reverse recovery time of Schottky diodes are extremely fast (but soft) recovery characteristics. What little reverse recovery time they may exhibit is primarily dictated by their capacitance rather than minority carrier recombination as in conventional pn junction rectifiers. This characteristic provides very little reverse current overshoot when switching the Schottky from the forward conducting mode to the reverse blocking state. The combination of very "fast soft switching properties" of a Schottky can also eliminate the need for snubber circuits in many applications that may otherwise be required with fast or ultrafast rectifiers displaying abrupt recovery characteristics. These features make schottky rectifiers a very attractive choice for low parasitic switching losses.
Design considerations with Schottky devices are limited in some applications compared to pn junction rectifiers because their reverse leakage currents are many times higher. Also Schottky rectifiers have maximum rated junction temperature typically in the range of 125 oC to 175 oC, compared to the typical 200 oC for conventional pn junctions which further influences leakage current behavior.
For some applications, Schottky devices are limited in available reverse blocking voltage ratings compared to conventional pn junction rectifiers. Nevertheless with judicious selection, many applications are optimized with Schottky rectifiers and their unique operating characteristics. Schottky rectifiers seldom exceed 100 volts in their working peak reverse voltage (VRRM), since devices moderately above this rating level will result in forward voltages equal to or greater than equivalent pn junction rectifiers.
Copyright 2016 Sunborn Technology Company Limited