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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Power Supply Systems
Electrical Energy Conversion and Power Systems
Universidad
de Oviedo
Power Electronic Devices
Semester 1
Lecturer: Javier Sebastián
Electrical Energy Conversion and Power Systems
Universidad
de Oviedo
Lesson 3  Power diodes.
Semester 1  Power Electronics Devices
i [mA]
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
Model
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

Ideal diode
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

Terminal
Package
(glassor epoxi resin)
Metalsemiconductor contact
P
Semiconductor die
N
Marking stripe on the cathode end
Terminal
Anode
Anode
Cathode
Cathode
DO 35
DO 41
DO 15
DO 201
DO 5
B 44
Common cathode
(Dual center tap Diodes)
Doubler
(2 diodes in series)
Name
Package
Dual in line
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 peak reverse voltage.
 Maximum repetitive peak reverse voltage, VRRM.
Maximum forward current.
 Maximum RMS forward current, IF(RMS).
IF(RMS) depends on the package.
i
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
Forward voltage drop, VF (V).
0.5V @ 10A
Forward voltage drop, VF (VI).
0.69V @ 10A
Schottky
Schottky
PN
Forward voltage drop, VF (VII).
IF(AV) = 8A, VRRM = 200V
IF(AV) = 4A, VRRM = 200V
IF(AV) = 5A, VRRM = 1200V
Reverse current, IR (I).
IF(AV) = 10A, VRRM = 40V
IF(AV) = 10A, VRRM = 170V
Reverse current, IR (II).
i
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).
iD
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

Losses in power diodes (II).
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
Losses in power diodes (III).
Losses in power diodes (IV).
Losses in power diodes (IV).