Power Supply Systems. Electrical Energy Conversion and Power Systems . Universidad de Oviedo. Power Electronic Devices. Semester 1 . Lecturer: Javier Sebastián. Outline. Review of the physical principles of operation of semiconductor devices.
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Electrical Energy Conversion and Power Systems
Universidad
de Oviedo
Semester 1
Lecturer: Javier Sebastián
Electrical Energy Conversion and Power Systems
Universidad
de Oviedo
Semester 1  Power Electronics Devices
100
Vext [V]
0
 0.25
0.25
0.5
Vext
i »IS·e
i [nA]
VT
Vext[V]
0
0.5
10
i » IS
(exponential)
(constant)
i
+
vext

According to Shockley equation
i [A]
3
Vext[V]
0
1
4
Actual IV characteristic
According to Shockley equation
Actual IV characteristic
i [A]
Vext[V]
VBR
600
0
i
+
vext

10
i [A]
ideal
0
Vext[V]
rd = 1/tga
V
Actual IV characteristic
Slope = 1/rd
a
V= Knee voltage
rd = Dynamicresistance
V
i
+
vext

i [A]
0
Vext[V]
Whatever the forward current is, the forward voltage drop is always zero.
i
+
Whatever the reverse voltage is, the reverse current is always zero.
vext

Package
(glassor epoxi resin)
Metalsemiconductor contact
P
Semiconductor die
N
Marking stripe on the cathode end
Terminal
Anode
Anode
Cathode
Cathode
(Dual center tap Diodes)
Doubler
(2 diodes in series)
Package
Internal structure of PN power diodes (I)
Aluminum contact
Aluminum contact
Anode
NA = 1019 cm3
P+
10 mm
100 mm
(for VBR=1000V)
N(epitaxial layer)
ND1 = 1014 cm3
N+(substrate)
250 mm
ND2 = 1019 cm3
Cathode
Internal structure of PN power diodes (II)
Depletion region in reverse bias
Anode
P+
High electric field intensity
N
N+
Cathode
Internal structure of PN power diodes (III)
Depletion region in reverse bias
Aluminum contact
Anode
SiO2
Aluminum contact
SiO2
P+
Guard ring
N
N+
Cathode
P
P
Depletion region in reverse bias
Internal structure of PN power diodes (IV)
Anode
High electric field intensity in these regions
P+
N
N+
Cathode
Internal structure of PN power diodes (V)
Depletion region in reverse bias
Anode
SiO2
SiO2
P+
N
N+
Cathode
Internal structure of Schottky power diodes (I)
Aluminum contact
(N+MÞohmic)
Aluminum contact
(NM Þ rectifying)
Depletion region in reverse bias
Anode
SiO2
High electric field intensity
N
N+
Cathode
Depletion region in reverse bias
Internal structure of Schottky power diodes (II)
Aluminum contact
(N+MÞohmic)
Aluminum contact
(NM Þ rectifying)
Anode
SiO2
SiO2
Guard ring
N
N+
Cathode
P
P
Information given by the manufacturers
 Maximum repetitive peak reverse voltage, VRRM.
 Maximum RMS forward current, IF(RMS).
IF(RMS) depends on the package.
ID
Vext
VD
ideal
5 A
rd
V
Forward voltage drop, VF (I).
Operating point
Load line
Operating point
Forward voltage drop, VF (II).
Forward voltage drop, VF (III).
IF(AV) = 5A,
VRRM = 1200V
IF(AV) = 4A, VRRM = 200V
1.25V @ 25A
2.2V @ 25A
Forward voltage drop, VF (IV).
IF(AV) = 25A, VRRM = 200V
IF(AV) = 22A, VRRM = 600V
0.84V @ 20A
1.6V @ 20A
0.5V @ 10A
Forward voltage drop, VF (VI).
0.69V @ 10A
Schottky
PN
Forward voltage drop, VF (VII).
IF(AV) = 4A, VRRM = 200V
IF(AV) = 5A, VRRM = 1200V
Reverse current, IR (I).
IF(AV) = 10A, VRRM = 170V
Reverse current, IR (II).
i
trr
t
ts
tf
v
t
Dynamic characteristic of power diodes (I).
t
td
tr
tfr
v
t
ts = storage time.
td = delay time.
tr =rise time.
tfr = td + tr = forward recovery time.
Dynamic characteristic of power diodes (II).
Switchon
Switchoff
IF(AV) = 2x8A,
VRRM = 200V
Dynamic characteristic of power diodes (III).

+
+



+
+
N

Ntype

Metal
+
+

+
+
·q·ND
Cj= A·
2·(V0+ Vrev)
Dynamic characteristic of power diodes (IV).
ND
Cj
Vrev
0
Dynamic characteristic of power diodes (V).
Example
Ideal
(lossless)
rd
V
Losses in power diodes (I).
Instantaneous value: pD_cond(t) = vD(t)·iD(t) = [V + rd·iD(t)]·iD(t)
iD
+
PD_cond = V·Iavg + rd·IRMS2
Iavg: averagevalue of iD(t)
IRMS: RMSvalue ofiD(t)
vD

iD
+
Power losses in a transistor
Power losses in the diode
vD
iD

10 A
trr = 30ns
t
ts
tf
3 A
VD
0.8 V
t
200 V