Addendum A
MIL-STD-704E Transient / Overvoltage Protection
The standard (COTS) 24V input 2nd Generation Converter Modules may be used in Military 28 volt applications. The
M-FIAM5 provides compliance to MIL-STD-461E conducted emissions and susceptibility standards. Additional circuitry,
as illustrated in the accompanying schematic (see Fig. 1), provides compliance to the MIL-STD-704E transient
overvoltage specification. The 24V input modules employ undervoltage and overvoltage protection. These converters,
shut down if the input falls below 18V or rises to 36V or above.18V is consistent with the MIL-STD-704E specification,
but the standard also requires uninterrupted performance in the event of an input voltage transient to 50V for a period
of 12.5 millisec. The above referenced circuit clamps the input voltage, in the event that it exceeds 32V, as illustrated in
figure 2. This performance prevents the converter from shutting down, thus meeting the transient overvoltage
specification of MIL- STD-704E.
+28V
Transient Surpressor Circuit
R1
2.0k
R2
2.0k
Vicor FIAM & Mods
Vc
C3
Cbulk
880 Uf d
Vout
Input
R3
64.9k
R4
64.9k
3
2
8
+
R8
U1A
LM258N
615001
1
24.3k
5
6
8
+
U1B
LM258N
7
2
R10
1.0K
1
4
R7
1.0k
Q1
IRFP3710
ND PN
3
–
C1
C2
C3
D1
Q1
R1
R2
R3
R4
R5
R6
R7
R8
R9
R10
U1
U2
4.7uF, 63V
0.1uF
880uF, 100V
1N5245B
IRFP3710ND
2.0K
2.0K
64.5K
64.5K
10K
10K
1K
24.3K
14K
1K
LM258N
LM4040CIZ-5.0
C1
4.7uf, 63v
–
4
R9
14.0k
D1
15v, 1N5245B
R5
10K
4
R6
10K
2
3
C2
.1ufd
+28v
rtn
U2
LM4040CIZ-5.0
Figure 1–
Transient / Overvoltage protection circuit.
Volts
50
28
27
32
Vin
Vout
12.5 Millisec Max
Figure 2–
Overvoltage clamping
Vicor Corp.
Tel: 800-735-6200, 978-470-2900 Fax: 978-475-6715
MFIAM5
Rev. 1.7
Page 4 of 5
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