K-Family
DC-DC Converters >100 W
Rugged Environment
8 - 6
Edition 2/96 - Melcher AG
MELCHER
The Power Partners.
8.1
Fig. 2
Block diagram of single output converters AK…LK 1000
Input
filter
Control
circuit
2
P
4
3
Forward
converter
(approx.
120
kHz)
Y
16
18
20
22
12
4
6
8
10
14
Y
Output
filter
1
26
28
30
32
24
5
–
+
Y
Functional Description
The input voltage is fed via an input fuse, an input filter, a
rectifier (LK types) and an inrush current limiter to the input
capacitor. This capacitor sources a single transistor forward
converter. Each output is powered by a separate secondary
winding of the main transformer. The resultant voltages are
rectified and their ripples smoothed by a power choke and
output filter. The control logic senses the main output volt-
age
Uo1 and generates, with respect to the maximum ad-
missible output currents, the control signal for the primary
switching transistor.
The second output of double output units is controlled by
the main output but has independent current limiting. If the
main output is taken into current limitation, the second out-
put voltage will fall as well and vice versa.
Fig. 3
Block diagram of symmetrical double output converters AK...LK 2000
4 Inrush current limiter in C/D/E/LK types (NTC or Opt. E),
-9 versions exclude the NTC
5 Input fuse
1 Transient suppressor (VDR) in C/D/E/F/LK types
2 Transient suppressor (diode) in A/B/C/FK types
3 Bridge rectifier in LK types
Input
filter
Control
circuit
1
2
P
4
3
Forward
converter
(approx.
110
kHz)
16
18
20
22
12
14
4
6
8
10
Output
2
filter
Output
1
filter
26
28
30
32
24
5
–
+
Y