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

Dâ€™

= T

D

- ( t

3

+ t

4

) + ( t

1

+ t

2

)

T

Dâ€™

) 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

Dâ€™

) of IGBT output terminals (C and E) are expressed by Equation 34:

Equation 34:

T

Dâ€™

= 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

Dâ€™

=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

Dâ€™

= 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