Hitachi IGBT Module Application Manual
5.7.3 Parametric Effects on Switching Delay Time
5.7.3.1
Examining Influential Parameters
module operating conditions:
Equation 33:
T
D’
= T
D
- ( t
3
+ t
4
) + ( t
1
+ t
2
)
T
D’
) relative to a dead time (
T
D
)
setting, and this equation allows for finite driver output delays (
t
1
and
t
3
). Often, these particular delay
times are judged to be negligible and are set to zero. Realistically, however, all driver delay times must be
checked.
The dead times (
T
D’
) of IGBT output terminals (C and E) are expressed by Equation 34:
Equation 34:
T
D’
= T
D
+ t
2
- t
4
Here,
T
D
represents a theoretical setting and times
t
2
and
t
4
are turn-ON and turn-OFF delay times,
respectively, which can be determined using Equation 35 and Equation 36.
Equation 35:
Equation 36:
t
d
(on)=-(R
G
+ Z
on
)
!
C
ies
!
ln{(V
GP
- V
th
(on))/(V
GP
+ V
GN
)
t
d
(off)= -(R
G
+ Z
off
)
!
3 C
ies
!
ln{(V
GN
+ V
th
(on))/(V
GP
+ V
GN
)} + Q
GC
/ I
Gres
(off)
Substituting these for Equation 34, you will get
Equation 37:
T
D’
=T
D
[-{(R
G
+ Z
on
)
!
C
ies
!
ln((V
GP
- V
th
(on))/
(V
GP
+ V
GN
)}]
-[-{(R
G
+ Z
off
)
!
3 C
ies
!
ln{(V
GN
+ V
th
(off))/(V
GP
+ V
GN
)}}
+ Q
GC
/ (I
G
res
(off)]
where OFF-gate current I
G
res
(off) can be determined with Equation 38:
Equation 38:
I
G res
(off)=( V
GP
+ V
th
(off)) / (R
G
+ Z
off
)
Substituting this expression into Equation 37 results in Equation 39:
Equation 39:
T
D’
= T
D
+[-{( R
G
+ Z
on
)
!
C
ies
!
ln((V
GP
- V
th
(on))/(V
GP
+ V
GN
)}]
-[-{(R
G
+ Z
off
)
!
3 C
ies
!
ln{(V
GN
+ V
th
(off))/(V
GP
+ V
GN
)}}
+ Q
GC
(R
G
+ Z
off
) / (V
GN
+ V
th
(off)]
5.7.3.2
Effect on Gate Voltages
In Equation 39, collector current I
C
and junction temperature T
j
affect two gate voltages: V
th
(on) and
V
th
(off) which have a relationship as shown in Figure 45 with collector current.
Figure 45. Gate Voltage - Collector Current Characteristics
41