Datasheet

LT4430
13
4430fc
For more information www.linear.com/LT4430
applicaTions inForMaTion
•
•
V
IN
4430 F03a
T1
1:N
V
OUT
C
OUT
CG
*OPTIONAL SEE TEXT
L1
Q2
FGQ1
LT4430
V
BIAS
C1
R1*
D1
4430 F03b
•
•
T1
N1
N2
1:N
N = N1 + N2
V
OUT
C
OUT
CG
*OPTIONAL SEE TEXT
L1
Q2
LT4430
V
BIAS
C1
R1*
D1
••
V
IN
FGQ1
•
•
V
IN
4430 F03c
T1
1:N
V
OUT
LT4430
V
BIAS
C
OUT
C1
R1*
D1
C2
CG
*OPTIONAL SEE TEXT
L1
Q2
FGQ1
R3*
R2
QBS
Z1
Figure 3a. Typical Single-Switch Synchronous Forward
Converter with Bias Generator
Figure 3b. Single-Switch Synchronous Forward Converter
with Tapped Secondary Bias Generator
Figure 3c. Single-Switch Synchronous Forward Converter
with Preregulator Bias Generator
Generate a bias supply for a forward converter using similar
techniques to that of the flyback converter. Figure 3a to 3c
detail the three common bias circuits for the synchronous
single-switch forward converter. In the flyback converter
of Figure 1d, the bias supply is proportional to V
IN
and
V
OUT
. However, in the forward converter, L1’s presence
decouples the bias supply from V
OUT
. In Figure 3a, the
bias supply equals (V
IN
• N – V
F
). In Figure 3b, the bias
supply equals (V
IN
• N1/N – V
F
). In Figure 3c, the bias
supply equals (V
Z1
– V
F
).