tech.support@psbel.com

belfuse.com/power-solutions

BCD20009-G Rev F, 20-Nov-2020

Page 5 of 16

IMX35 Series

35 Watt Quad-Output DC-DC Converter

© 2020 Bel Power Solutions & Protection

Inrush Current

The inrush current has been made as low as possible by choosing a very small input capacitance. A series resistor may be installed

in the input line to further reduce this current.

t

04022b

0

20

40

60

80

100 µs

4

3

2

1

A

t

04008b

Fig. 2

Typical inrush current at V

Source impedance according to ETS 300132-2 at V

Fig. 3

Converter start-up and rise time (see table 2)

Reverse Polarity Protection

The built-in suppressor diode also provides for reverse polarity protection at the input by conducting current in the reverse

direction. An external fuse is required to limit this current.

Table 3: Recommended external fuses in the non-earthed input line

Model

Fuse type

20IMX35

F 8.0 A

40IMX35

F 4.0 A

70IMX35

F 2.0 A

110IMX35

F 1.5 A

Input Transient Voltage Protection

A built-in suppressor diode provides effective protection against input transients, which may be generated for example by short-

circuits across the input lines, where the network inductance may cause high energy pulses.

Table 4: Built-in transient voltage suppressor

Model

Breakdown voltage

V

Peak power at 1 ms

P

Peak pulse current

I

20IMX35

39

1500

22

40IMX35

100

1500

9.7

70IMX35

151

600

2.9

110IMX35

176

600

2.5

For very high energy transients as for example to achieve IEC/EN 61000-4-5 compliance (as per table Electromagnetic Immunity)

an external inductor and capacitor are required. The components should have similar characteristics as listed in table below.

Table 5:

Components for external circuitry for IEC/EN 61000-4-5, level 2

Model

Inductor (L)

Capacitor (C1 , C2)

Diode (D)

20IMX35 1.45 mH / 5 A

C1, C2: 220 μF / 50 V

1.5 k E47A

40IMX35

4 mH / 3 A

C1, C2: 100 μF / 100 V

---

70IMX35

4 mH / 1.5 A

C1: 120 μF / 160 V

C2: 240 μF / 160 V

---

110IMX35 4.5 mH / 1.5 A

C1: 120 μF / 200 V

C2: 240 μF / 200 V

---

Vi+

Vi–

C

2

L

D

+

C

1

+

IMX35

Fig. 4

Example for external circuitry to comply with IEC/EN 61000-4-5;

the diode D is only necessary for 20IMX35 models.