LT1950
17
1950fa
SLOPE
V
REF
R
OSC
BLANK
SYNC
FB
COMP
V
IN
V
IN2
V
SEC
SHDN
GATE
I
SENSE
GND
PGND
LT1950
5
6
3
9
4
2
1
15
11
16
7
12
10
8
13
210k
27k
6.8k
0.1µF
+V
IN
+V
IN
–V
IN
T1
PA0581
+V
OUT
C
IN
2.2µF
100V
X5R
36V
TO 72V
INPUT
10V
BIAS
470k
18k
232k
24.9k
47µF
Si7450
+
–
330R
470pF
18k
1µF
1µF
47k
4
3
5
2
1
8.2V
22k
U2
LT1009
U3
LT1797
FMMT625
OC1
1950 F13
47µH
0.015
MBR20200CT
Figure 13. 36V to 72V Input to 26V at 5A Nonsynchronous Forward Converter
LOAD CURRENT (A)
1
EFFICIENCY (%)
5
1950 F12
2
3
4
94
93
92
91
90
89
88
87
86
85
84
V
IN
= 48V
V
OUT
= 26V
f
OSC
= 235kHz
Figure 12. LT1950-Based Nonsynchronous
Forward Converter Efficiency vs Load
Current (Figure 13 Circuit)
High Efficiency, Isolated 26V 5A Output,
Nonsynchronous Forward Converter
Figure 13 illustrates a nonsynchronous forward converter
based on the LT1950 to provide a highly efficient, 26V 5A
isolated output from 48V input. The LT1950-based con-
verter using a single switch topology and utilizing the
LT1950s adaptive maximum duty cycle clamp is a simple
and highly optimized solution. Peak efficiencies of 92.8%
(Figure 12) are achievable. Transformer and inductor are
standard components. The quarter brick sized DC/DC
converter (2.3" by 1.45") delivers over 125W and is only
0.4" high. The 26V converter can be used as a “front line”
(isolating) converter in telecom systems with multiple
outputs.
APPLICATIO S I FOR ATIO
WUUU
