power electronics
DESCRIPTION
بسم الله الرحمن الرحيم. The Islamic University of Gaza Faculty of Engineering Electrical Engineering Department. POWER ELECTRONICS. EELE 5450 — Fall 2009-2010. Instructor: Eng.Moayed N. EL Mobaied. Lecture 3. Chapter Two. Power Semiconductor Diodes. - PowerPoint PPT PresentationTRANSCRIPT
POWER ELECTRONICS
Instructor: Eng.Moayed N. EL Mobaied
The Islamic University of GazaFaculty of EngineeringElectrical Engineering Department
الرحمن الله بسمالرحيم
EELE 5450 — Fall 2009-2010
Lecture 3
Chapter Two
Power Semiconductor Diodes
Power diodes have large power-, voltage-, current-handling capabilities than that of ordinary signal diodes.
Chapter Two
Power Diodes symbol and type of packaging
Chapter Two
Diode Characteristics
Chapter Two
V-I characteristicsForward-biased regionReverse biased region Breakdown region
Chapter Two
N=1,2( Germanium, Silicon) practically 1.1—1.8
)1( TnVdV
eII SD
qKt
TV
Shockley’s equation
VT= Thermal voltage
IS= Saturation current
Cechelectronicofmagnitudetheisq
CintemthekelvinsinetemperaturabsoultetheisT
kjtconssBoltzmanisk
1910*6.1arg
237
/2310*38.1tan'
Chapter Two
Shockley diode equation
Chapter Two
Forward-bias VD>0
Chapter Two
Reverse-bias VD<0
Chapter Two
Reverse Recovery Characteristics
2(2.8)RR
RRrr
QI
t
2(2.10)
/RR
rr
Qt
di dt 2 (2.11)RR RR
diI Q
dt
(2.5)rr a bt t t Tb/Ta is the softness factor (SF)
Chapter Two
Power Diode Types
Ideally, a diode should have no reverse recovery time, However, the manufacturing cost of such diode will increase.
The power diodes can be classified into three categories:
Standard or general-purpose diodes Fast-recovery diodes Schottky diodes
Chapter Two
Standard or general-purpose diodes
Reverse recovery time= 25 us (relatively high).Used in Low-speed applications.Current rating : From less than 1 Ampere to several
thousands of Amperes.Voltage rating 50 v to 5 kV.
Chapter Two
Fast-Recovery Diodes
Reverse recovery time< 5 us ( Low).Used in DC-DC and DC-AC converter circuit (high
speed applications).Current rating : From less than 1 Ampere to several
hundreds of Amperes.Voltage rating 50 v to 3 kV.Platinum or gold.
Chapter Two
Schottky Diodes
No minority carriers .
Recovered charge is much less than P-n junction diodes.
Used in high current and low voltage dc power supplies.
Current rating : From 1 Ampere to 300 Amperes.
Voltage rating <100 V.
Chapter Two
End of Lecture **** Eng.moayed
The reverse recovery time of a diode is trr=3us and the rate of fall of the diode current is di/dt=30 A/usDetermine (a) the storage charge Qrr
(b) Peak reverse current Irr