GE Industrial Solutions FLT007A0-SRZ - Manual (Page 5)

Data Sheet
July 14, 2010
FLT007A0Z/FLT007A0-SRZ Input Filter Modules
75Vdc Input Voltage Maximum, 7A Output Current Maximum
LINEAGE POWER 5
Application Guidelines
Conducted noise on the input power lines can occur
as either differential-mode or common-mode noise
currents. Differential-mode noise is measured
between the two input lines, and is found mostly at
the low frequency end of the spectrum. This noise
shows up as noise at the fundamental switching
frequency and its harmonics. Common-mode noise is
measured between the input lines and ground and is
mostly broadband noise above 10 MHz. The high-
frequency nature of common-mode noise is mostly
due to the high-speed switching transitions of power
train components. Either or both types of noise may
be covered in a specification, as well as a
combination of the two.
Differential-mode noise is best attenuated using a
filter composed of line-to-line capacitors (X caps) and
series inductance, provided by either a discrete
inductor or the leakage inductance of a common-
mode choke. In addition to the differential filtering
provided by the filter module, it is recommended that
an electrolytic capacitor be located at the converter
side of the filter to provide additional attenuation of
low-frequency differential noise and to provide a low
source impedance for the converter, preventing input
filter oscillations and load transient induced input
voltage dips.
Open-frame DC/DC converter modules and the older
metal-cased DC/DC converter modules require
slightly different filtering arrangements. The
FLT007A0Z series of modules are optimized for the
newer open-frame series of modules, but can also be
used with older metal-case modules. The main
differences in filtering recommendations between the
two types of modules are in common-mode filtering,
as explained below.
Filtering Open-Frame DC/DC
Converter Modules
For filtering open-frame DC/DC converter modules,
the recommended circuit is shown in Fig. 5. In
addition to the input electrolytic filter capacitor C1
(recommended value is a minimum of 100uF and
approximately 1uF/W at power levels above 100W),
common-mode filtering capacitors C2 and C3 should
be connected between the input and outputs as
shown. Suitable values for common-mode capacitors
C2 and C3 are in the range between 1000pF to 0.1
µF
are usually indicated in the DC/DC converter data
sheet. These capacitors need to be rated for the
isolation voltage desired
between the input and output
sides of the DC/DC converter module. The
recommended power layout of the modules
showing
where the two common-mode capacitors are to be
placed is shown in Fig. 6.
DC/DC
CONVERTER
MODULE
VI(-)
VI(+)
VO(-)
VO(+)
C1
C2
C3
CHASSIS GROUND
FILTER
MODULE
VI(+)
VI(-)
Figure 5. Schematic diagram showing
recommended connection of the FLT007A0Z
filter module with open-frame DC/DC converter
modules.
C
2
Load
FLT007A0
MODULE
DC/DC
CONVERTER
V
O
+ PLANE
V
O
− PLANE
C
3
C
1
V
I
+ V
O
+
V
O
− V I
−
V IN
− V
O
−
V
IN
+
GND
V
IN
+
V
IN
−
CHASSIS
GROUND
Input
V
O
+
Figure 6. Diagram showing recommended
layout of the FLT007A0Z filter module with
open-frame DC/DC converter modules.
Filtering Metal-Case DC/DC Converter
Modules
For metal-case DC/DC converter modules with a case
pin, a different filtering arrangement and layout is
recommended. Figure 7 shows the schematic
diagram of the recommended circuit. The main
difference with open-frame module is the use of an
isolated shield plane located underneath the module
which is connected through capacitors C2 through C5
to the input and output connections of the module.
The shield plane along with the case of the module
serves as a Faraday shield helping reduce EMI. The
corresponding layout for metal-case modules is
shown in Fig. 8.