Fast Recovery

Basic Concept:

The switched-mode power supply market has shown an interesting trend in recent years, mainly driven by a new demand in PCs and Telecom applications. The implementation of new circuit topologies and a tremendous increase in switching frequency to meet new limits, have been the driving factors in the development of new semiconductor components.

Fast rectifiers are today playing a key role in these new topologies and in the trend of increased frequency of operation. As switching speeds or frequency of operation increase well beyond 400Hz, rectifiers can become inefficient or notably handicapped to a variety of applications unless designed and selected with added performance features. This is most often given in terms of Reverse Recovery Time Trr. Applications may include switched mode power supplies or others requiring high speed rectifier response. In these examples, rectifiers are often expected to respond as ideal switches or "one-way-current-flow valves" to meet functional circuit requirements when subjected to forward and reverse voltage environments. High speed rectifiers best approach this ideal by minimizing switching energy losses and heat that can otherwise be generated in other circuit components and in switching rectifiers themselves.

The industry generally identifies a rectifier as "fast" if it is rated with reverse recovery of 500ns or less (approx. 1/10 that of standard rectifiers). If further improved to 100ns or less, it is often termed "ultrafast" or "superfast". Low current small signal diodes with 10-100 volt VRRM are in the Trr range of 0.75 to 5 ns. Medium to high current ultrafast / superfast rectifiers are available in a range of 15 to 60 ns as voltage rating is increased from 50 to 800 volt VRRM operation.

Surface Mount Devices

Part Number Package VRRM IO Trr
DRS1A~DRS1M SOD-123FL 50V~1000V 1.0A 150ns~500ns
RS1A~RS1M SMA (DO-214AC) 50V~1000V 1.0A 150ns~500ns
RS2AA~RS2MA SMA (DO-214AC) 50V~1000V 2.0A 150ns~500ns
RS2A~RS2M SMB (DO-214AA) 50V~1000V 2.0A 150ns~500ns
RS3AB~RS3MB SMB (DO-214AA) 50V~1000V 3.0A 150ns~500ns
RS3A~RS3M SMC (DO-214AB) 50V~1000V 3.0A 150ns~500ns
RS5AB~RS5MB SMB (DO-214AA) 50V~1000V 5.0A 150ns~500ns
RS5A~RS5M SMC (DO-214AB) 50V~1000V 5.0A 150ns~500ns

Lead Devices

Part Number Package VRRM Io Trr
1N4933~1N4937 DO-41 50V~600V 1.0A 200ns
FR101~FR107 DO-41 50V~1000V 1.0A 150ns~500ns
FR201~FR207 DO-15 50V~1000V 2.0A 150ns~500ns
FR301~FR307 DO-201AD 50V~1000V 3.0A 150ns~500ns
FR601~FR607 R-6 50V~1000V 6.0A 150ns~500ns