#3 design of switching power-pole
DESCRIPTION
power electronicsTRANSCRIPT
© Copyright Ned Mohan 2010
Design of Switching Power-Poles
• Power Semiconductor Devices– Diodes– Transistors
• Losses in Switching Power-Poles– Switching Losses– Conduction Losses
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© Copyright Ned Mohan 2010
Choice of Diodes
• Line-Frequency Diodes• Fast Recovery Diodes• Schottky Diodes
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(b)
A K
AKi
AKv0
(b)
A K
AKi
AKv0
© Copyright Ned Mohan 2010
Choice of Power Transistors
• MOSFET
• IGBT
• IGCT
• GTO
• Others
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IGBT MOSFETIGCT(a)
101 102 103 104
102
104
106
108
Thyr
isto
r
IGBT
MOSFET
Pow
er (V
A)
Switching Frequency (Hz)
IGCT
IGBT MOSFETIGCT(a)
IGBT MOSFETIGCT(a)
101 102 103 104
102
104
106
108
Thyr
isto
r
IGBT
MOSFET
Pow
er (V
A)
Switching Frequency (Hz)
IGCT
101 102 103 104
102
104
106
108
Thyr
isto
r
IGBT
MOSFET
Pow
er (V
A)
Switching Frequency (Hz)
IGCT
101 102 103 104
102
104
106
108
Thyr
isto
r
IGBT
MOSFET
Pow
er (V
A)
Switching Frequency (Hz)
IGCT
© Copyright Ned Mohan 2010
SELECTION OF POWER TRANSISTORS AND POWER DIODES
• Voltage Ratings
• Current Ratings
• Switching Speeds
• On-State Voltage Drop
4
© Copyright Ned Mohan 2010
MOSFET Characteristics
5
G
D
SGSV
DSV
Di
(a) (c) (b)
GSV 11V
9V7V5V
DSV
Di
0( )GS GS thV V
( ) 1/slopeDS onR
GSV
Di
0
oI
( )GS thV ( )oGS IV
2.5 2.7( )
toDS on DSSR V
© Copyright Ned Mohan 2010
IGBT Characteristics
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C
E
G CEV
GEV
Ci
GEV
CEV
Ci
(a) (b)
C
E
G CEV
GEV
Ci
C
E
G CEV
GEV
Ci
GEV
CEV
Ci
GEV
CEV
Ci
(a) (b)
© Copyright Ned Mohan 2010
Switching in a Power-Pole
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inV
Di
oI
Di
0DSv
off
onoI
GGRGGV DSv
inV
inV
Di
oI
Di
0DSv
off
onoI
GGRGGV DSv
inV
© Copyright Ned Mohan 2010
Turn-on Characteristics
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Di
DSv
oIon
off
A
0
0
0
GSv
t
t
oIDiinV DSv
( )d ont rit fvt
GGv
oI
inV
G
S
DDi
0GGv B
DSv
inV
( )oGS Iv( )GS thv
Di
DSv
oIon
off
A
0
0
0
GSv
t
t
oIDiinV DSv
( )d ont rit fvt
GGv
oI
inV
G
S
DDi
0GGv B
DSv
inV
( )oGS Iv( )GS thv
inV
0
GGV
DiD
0I
DiS
G DSv
diode o D D oi I i i I
© Copyright Ned Mohan 2010 9
Turn-off Characteristic
oI
inV
GS
DDi
0GGv
Di
DSv
oIon
off
D
0
C 0
0
GSv
t
t
oIDi
inV
DSv
( )d offt rvt fit
GGv( )oGS Iv( )GS thv
DSv
inVoI
inV
GS
DDi
0GGv
Di
DSv
oIon
off
D
0
C 0
0
GSv
t
t
oIDi
inV
DSv
( )d offt rvt fit
GGv( )oGS Iv( )GS thv
DSv
inV
© Copyright Ned Mohan 2010 10
Calculating Power Losses Within the MOSFET (assuming an ideal diode)
Switching Losses: , ,1 ( )2sw in o c on c off sP V I t t f
,c on ri fvt t t
,c off rv fit t t
0t
oI DSv
,c ont
rit fvt
0t
Di
inV
,c offtrvt fit
DSvinV
Di
,c ont
,c offt
swp in oV I in oV Iswp
0t
oI DSv
,c ont
rit fvt
0t
Di
inV
,c offtrvt fit
DSvinV
Di
,c ont
,c offt
swp in oV I in oV Iswp
© Copyright Ned Mohan 2010 11
Conduction Loss:
2( )cond DS on oP d R I
© Copyright Ned Mohan 2010
Summary
• Design of a Switching Power-Pole– Power Semiconductor Devices
• Diodes• Transistors
– Losses in Switching Power-Poles• Switching Losses• Conduction Losses
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