New-Tech Europe Magazine | July 2016 | Digital edition

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ALL MODELS AVAILABLE WITH
EXPANDED OPERATING TEMPERATURES
SELECTED MILITARY SCREENING
CUSTOM DESIGNS
DC-DC
CONVERTERS
NEW!!
HIGH INPUT VOLTAGES
UP TO 900 VDC.
For full characteristics of these and the entire PICO product
line, see PICO’s Full line catalog at
DC-1 Series
• 120-370 VDC input voltage range
• 5-300 VDC regulated isolated outputs
• Up to 300 watts output power
• 4.5” X 2.5” X 0.50” encapsulated package
DC-3 Series
• 300-900 VDC input voltage range
• 3.3 -300 VDC regulated isolated outputs
• Up to 50 watts, single and dual outputs
• Thru hole and terminal strip models
HiQP Series
• 125-475 VDC input voltage range
• 24-200 VDC regulated isolated outputs
• Up to 50 watts output power
• 2.50” X 1.55” X 0.50” encapsulated package
HiQP Series
DC-3 Series
•
•
DC-1 Series
Pico Representatives
Germany
ELBV/Electronische Bauelemente Vertrieb
E-mail:
Phone: 0049 89 4602852
Fax:0049 89 46205442
England
Ginsbury Electronics Ltd.
E-mail:
Phone:0044 1634 298900
Fax:0044 1634 290904
PICO ELECTRONICS, Inc.
A46E_6cmx23cm_A45.qxd 7/14/16 1:31 PM Page 1
currents are effectively suppressed
by connecting bypass capacitors
between each power line of the
switching power supply and ground.
These power lines may be at the input
and/or output of the switching power
supply.
Further suppression of common mode
currents can be achieved by adding
a pair of coupled choke inductors in
series with each main power feed.
The high impedance of the coupled
choke inductors forces common
mode currents through the bypass
capacitors.
Radiated EMI
Radiated EMI can be suppressed by
reducing RF impedance and reducing
the antenna loop area. This is
achieved by minimizing the enclosed
loop area formed by the power line
and its return path.
The inductance of a printed circuit
board track can be minimized by
making it as wide as possible and
routing it parallel to its return path.
Similarly, because the impedance of a
wire loop is proportional to its area,
reducing the area between the power
line and its return path will further
reduce its impedance. Within printed
circuit boards this area can be best
reduced by placing the power line and
return path one above the other on
adjacent printed circuit board layers.
Reducing the loop area between a
power line and its return path not
only reduces the RF impedance, but
it also limits the effectiveness of the
antenna because the smaller loop area
produces a reduced electromagnetic
field.
Furthermore, a ground plane located
on the outer surfaces of the printed
circuit board significantly suppresses
radiated EMI, particularly if located
directly below the noise-generating
source.
And to further reduce radiated noise,
metal shielding can be utilized, placing
the noise-generating source within
a grounded conductive housing,
and interfacing to the clean outside
environment is via in-line filters.
Common mode bypass capacitors
would also need to be returned to
ground on the conductive housing.
System-Level EMI
Mitigation Techniques
Although most switching supplies
are designed to meet applicable EMI
standards as stand-alone modules,
the system itself needs be designed
to generate a minimum EMI profile to
meet regulatory standards. Specific
areas in the system design that
are candidates for EMI mitigation
practices include the signal lines,
printed circuit boards (PCB), and solid
state components.
Summary
Switching power supplies generate
EMI because of their inherent design.
Domestic and international regulatory
bodies regulate these emissions
through promulgation of rules and
standards such as the FCC Part 15
rules and the CISPR 22 standard.
Power modules are one of many
components within a system and
EMI requirements, both radiated
and conductive, apply to an overall
electronic system. Since the EMI
requirements apply to the overall
system, significant effort must be
expended on system design to limit
noise.
Further information on EMI mitigation
in power modules, including an
application note, is available from
the ac-dc power supplies and dc-dc
converters pages of the CUI website.
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