Board Mountable
DC-DC Converters
IMS 7 Series
Input Transient Voltage Protection
Reverse Polarity Protection at Input
In many applications transient voltages on the input of the
converter are always possible. These may be caused for ex-
ample be short circuits between Vi+ and Vi– where the net-
work inductance may cause high energy pulses.
The suppressor diode on the input also provides for reverse
polarity protection by conducting current in the reverse di-
rection, thus protecting the unit. An external fuse is required
to limit this current:
– For 24 IMS 7 a fast 2 A (F2A) fuse is recommended.
– For 48 IMS 7 a fast 1 A (F1A) fuse is recommended.
In order to protect the converter a large transient voltage
supressor has been fitted to the input of the IMS 7 types.
Specifications as per table below.
Inrush Current
Table 3: Built-in transient voltage suppressor
The inrush current has been kept as low as possible by
choosing a very small input capacitance. A series resistor
may be inserted in the input line to limit this current further.
Type
Breakdown
Voltage
Peak Power
at 1 ms
PP
Peak Pulse
Current
IPP
VBR nom
1 A/Div.
4
24 IMS 7
48 IMS 7
53 V
600 W
600 W
7.7 A
4.1 A
04030
100 V
3
2
If transients generating currents above the peak pulse cur-
rent Ipp are possible then an external limiting network such
as the circuit recommended for IEC 801-5, level 2 compli-
ance is necessary.
1
0
To achieve IEC/EN 61000-4-5, level 2 compliance an addi-
tional inductor and capacitor should be provided externally
as shown in the figure below. The components should have
similar characteristics as listed in table 9.
10 µs/Div.
To withstand the 150 V transient according to 19 Pfl 1, appli-
cable for 48 IMS 7 types, the same external circuitry with
similar components as for IEC/EN 61000-4-5, level 2 com-
pliance can be used.
Fig. 8
Typical inrush current at Ui nom, Po nom versus time
(48 IMS 7) measured according to prETS 300132-2 (Ver-
sion 4.3)
04043
L
V+
Vi+
i
+
Module
C
V–
Vi–
Fig. 6
Example for external circuitry to comply with
IEC/EN 61000-4-5, level 2.
Table 4: Components for external circuitry to comply with
IEC/EN 61000-4-5
Circuit Ref.
24 IMS 7
48 IMS 7
L
330 µH, 0.42 Ω, 0.6 A
330 µH, 0.42 Ω, 0.6 A
TDK TSL1110-331KR55 TDK TSL1110-331KR55
C
68 µ, 63 V, 85°C
68 µF, 100 V, 85°C
04029
10.5
5
0.7
Fig. 7
Dimensions for inductor L
Edition 1/7.2002
5/14