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

Determine current for a bjt, Q. For a BJT with vBE = 0.7V, I CBO = 4 nA, ...

Q. For a BJT with vBE = 0.7V, I CBO = 4 nA, i E = 1 mA, and i C = 0.9 mA, evaluate α, iB,iSE, and β.

Calculate the iron loss, Q. The efficiency of a 400-kVA, single-phase, 60-H...

Q. The efficiency of a 400-kVA, single-phase, 60-Hz transformer is 98.77% when delivering full-load current at 0.8 power factor, and 99.13%with half rated current at unity power fa

Calculate the total power supplied to the divider circuit, There is often a...

There is often a need to produce more than one voltage from a single supply using a voltage divider. For example, the memory components of many personal computers require voltages

Duty cycle of the system, The report should contain all of the information ...

The report should contain all of the information detailed below together with your analysis of the circuit and any conclusions. The report should contain the code for your simulati

The resistance of a 7 m length of the similar cable, The resistance of a 2 ...

The resistance of a 2 m length of cable is 2.5?. Verify (a) the resistance of a 7 m length of the similar cable and (b) the length of the same wire when the resistance is 6.2

Explain about common control, Q. Explain about Common Control? Common C...

Q. Explain about Common Control? Common Control: Those systems in which the control subsystem is outside the switching network are known as common control switching system. Str

Analog signal processing, Derive Equation 13-20 pertaining to the convers...

Derive Equation 13-20 pertaining to the conversion algorithm based on redefined unit capacitor

Determine the line current-total apparent power, A balanced three phase, fo...

A balanced three phase, four wire, WYE connect load consisting of per phase resistenance of A ohms and inductive reactance of D ohms/phase is connected to a B000 V three phase sour

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