Reverse recovery characteristics, Electrical Engineering

Assignment Help:

Reverse Recovery Characteristics

At the end of forward  conduction in diode  reverse current  flows for  a short  time. The  device  doesn't  attain its full blocking  capability  until  the reverse current  cease. The  reverse current flows  in the interval called  reverse  recovery time. During  this time  charge  carriers stored in the diode at the end of forward  conduction are removed. Actually when a  power diode  has been conduction in the  forward direction sufficiently long to  establish  the steady state there  will be a charge  due to  minority  carriers  present. Before  the device  can  block in the reverse direction  this charge  must be extracted.

This  extraction takes  the from  of a transient reverse current and this  together  with the  reverse bias  voltage results in additional power  dissipation  which reduces the rectification efficiency.  Reverse recovery time is measured  instant the current recovers to 25% of its peak  reverse value. low  reverse state forward  current and low reverse bias  voltage increase recovery time. High  rate of all of anode  current reduces recovery time but  increase stored charge. High  junction temperature is  increase both   recovery time and  stored charge.

There  are two  parts of  reverse recovery  time. One  is the time  between  zero  crossing  of forward current  and peak reverse current. During  this time  period, charges stored  in  depletion  region  is removed.  The other part  of t measured form the instant of peak reverse current to the instant where  25% of peak reverse  current  is reached. During this time period charges from the two  semiconductor layer are removed.

The  shaded  area in figure  represents  the stored  charge  or reverse  recovery charge  which  must be  removed  during  the reverse recovery time. The  ration ½ is known  as softness factor. Voltages  transient occurs during  the time  diode  recovers is measured by the factor.

b.   forward  voltage  drop vf and forward  current  if gives  the power  loss  in a diode.  The total power  loss in  given by  average value of V f i f  during  time t2 major power  loss  occurs  in a diode. As shown in  figure peak reverse current  IFP is given by

 I =  RP = t1 di/ dt

Where Do/ dt  is the  rate of  rise of  reverse  current. If  the reverse  recovery  characteristics  is assumed as a triangle shape  then storage charge  Q can be written as .

Q =  ( ½) (IRP ) (t rr).


Related Discussions:- Reverse recovery characteristics

Show equivalent circuit of a synchronous machine, Equivalent Circuit of a S...

Equivalent Circuit of a Synchronous Machine A review of the material about elementary synchronous machines is very helpful at this stage to recall the principles of operation f

Purpose of control word written to control register in 8255, What is the pu...

What is the purpose of control word written to control register in 8255? The control words written to control register state an I/O function for every I.O port. The bit D7 of t

Emf, what is emf

what is emf

Explain the programming of 8254 microprocesser, Explain the programming of ...

Explain the programming of 8254 microprocesser. 8254 Programming: All counters are individually programmed through writing a control word, followed with the initial count.

Determine the current and voltage in given network, Q. For a part of the ne...

Q. For a part of the network shown in Figure, given that i 1 = 4A; i 3 (t) = 5e -t , and i 4 (t) = 10 cos 2t, find v 1 , v 2 , v 3 , v 4 , i 2 , and i 5 .

Derive the transfer function, A data hold is to be constructed that reconst...

A data hold is to be constructed that reconstructs the sampled signal by the straight-line approximation shown in Figure. Note that this device is a polygonal data hold with a dela

Forth generation, Forth Generation VLSI  technology  of IC made it poss...

Forth Generation VLSI  technology  of IC made it possible  to design the  complete  circuit  of ALU  Arithmetic  logic unit and cu ( Control Unit ) within  single  chip  which

Carrier concentrations, Carrier Concentrations For the calcu...

Carrier Concentrations For the calculation of semiconductor electrical properties and analyzing device behavior, it is necessary to know the number of charge carrier

Semiconductor equations, Semiconductor Equations  The semiconductor e...

Semiconductor Equations  The semiconductor equations that are relating these variables are shown below: Carrier density: n = n i exp (E FN - E i / KT)        (1)

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd