Application Note
12
2011-07-06
Solve the equation and find
Then
eq
R
is 5k
Ω
according to Figure 3. According to the definition of over-current protection,
ocp
eq
R
R
R
FMIN
//
=
,
Then
ocp
R
can be found as 5.6k
Ω
.
2.3.4 Dead
time
The dead time selection should ensure ZVS of two primary-side MOSFET IPA60R199CP at maximum
switching frequency, where the magnetizing current to charge and discharge
ds
C
is the minimum. The
magnetizing current at the end of each switching cycle can be calculated as:
[18]
The required time to charge and discharge the
ds
C
is:
[19]
Then
TD
R
is around 270k
Ω
according to Figure 4.
Figure 4
DEAD
T
Vs
TD
R
kHz
f
ocp
250
=
A
f
L
N
V
V
I
ocp
p
e
ds
O
mag
288
.
0
10
*
250
*
10
*
690
*
4
5
.
16
*
)
1
.
0
12
(
4
*
)
(
3
6
min
=
+
=
+
=
−
ns
I
V
C
I
V
C
T
mag
innom
ds
mag
innom
ds
DEAD
440
288
.
0
400
*
10
*
160
*
2
2
2
12
min
min
=
=
=
=
−