Description

Over the past 5 years, power topologies have changed fundamentally. Various power supply structures are bulky now, and there is no 50/60-Hz power transformer. more necessary. These traditional transformers account for a major part of the volume and conventional power supplies by weight. today they have been replaced using smaller and lighter planar transformers, Its core material now consists of sintered ferrite instead of iron sheets operating frequency up to 250-kHz. For the same power rating, high operating frequency significantly reduces weight and volume converter. This development is significantly influenced by novelty, Fast switching power transistors, e.g. as MOSFETS or IGBTs, operate at high blocking voltage (V_CES>600-V).However, almost all topologies are equipped with these transistors also require ultra-fast diode response to conduct load current and rectify AC output when DC voltage is required. The switching behavior of these diodes must be tailored to match the switching properties of transistors.
This applies not only to switching power supplies, but also to inverter circuits. For these inverters, the PWM frequency chosen by the manufacturer is around 8-kHz to create a smooth sinusoidal waveform of the output current or use a PWM frequency that operates above the audible level of 20-kHz.
In addition to its characteristics, there are free power transfer switches, pass diodes and freewheeling diodes regarding power loss, efficiency and operational safety of the entire plant. 
They also play a decisive role in improving SMPS efficiency and reducing inverter losses, a clear requirement for ultrafast diodes use.

Ultrafast Diode description All functions are included here modern epitaxial diodes, e.g. soft recovery, have low reverse recovery current IRM and short reverse recovery times.

Technologies

The abbreviation FRED (Fast Recovery Epitaxial Diodes) stands for a series of ultrafast diodes, which have gained wide acceptance during the last few years.

There exist several methods to control the switching characteristics of diodes and each leads to a different interdependency of forward voltage drop V_F, blocking voltage V_RRM and t_rr values. It is these interdependencies (or compromises) that differeniate the ultrafast d odes available on the market today. Fig.1 shows a qualitative relationship of forward voltage V_F and  reverse recovery time t_rr. 

The most  important parameters for the turn-on and turn-off behavior of a diode (Fig. 2) V_FR, V_F, t_fr and I_RM, t_rr will be influenced by different   manufacturing

Futurewafer has developed extreme fast FRED products based on years of epi design experience. Covering low voltage  200-V to high voltage 1200-V, its soft recovery characteristics and high junction temperature of 175-°C will make the circuit more efficient.