![Page 1: EMC: Common mode stromen veroorzaakt door Power Devices ... · Lex de Rijck. Acradac Power Electronics Event 20 juni 2017 ©Acradac EMC training and Consultancy 2 Common mode currents](https://reader033.vdocuments.site/reader033/viewer/2022050115/5f4c63612a9f07434e7ca130/html5/thumbnails/1.jpg)
EMC: Common mode stromen veroorzaakt door Power Devices,
weet jij waar ze lopen?
Lex de Rijck
![Page 2: EMC: Common mode stromen veroorzaakt door Power Devices ... · Lex de Rijck. Acradac Power Electronics Event 20 juni 2017 ©Acradac EMC training and Consultancy 2 Common mode currents](https://reader033.vdocuments.site/reader033/viewer/2022050115/5f4c63612a9f07434e7ca130/html5/thumbnails/2.jpg)
2Acradac Power Electronics Event 20 juni 2017 ©Acradac EMC training and Consultancy
Common mode currents
• Cause EMI emissions (both conducted and radiated)
• Cause self-contamination, which can lead to malfunctions
![Page 3: EMC: Common mode stromen veroorzaakt door Power Devices ... · Lex de Rijck. Acradac Power Electronics Event 20 juni 2017 ©Acradac EMC training and Consultancy 2 Common mode currents](https://reader033.vdocuments.site/reader033/viewer/2022050115/5f4c63612a9f07434e7ca130/html5/thumbnails/3.jpg)
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Current loop in vicinity or an
external field (Wifi, GSM, GPS,
Bluetooth, RF-ID, Radio 3,
home automation, radio-
amateurs, CB, etc…)
Big loops are bad for
EMC and should be as
small as possible
(for both emission and
immunity)
Basic EMI principle
![Page 4: EMC: Common mode stromen veroorzaakt door Power Devices ... · Lex de Rijck. Acradac Power Electronics Event 20 juni 2017 ©Acradac EMC training and Consultancy 2 Common mode currents](https://reader033.vdocuments.site/reader033/viewer/2022050115/5f4c63612a9f07434e7ca130/html5/thumbnails/4.jpg)
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EN class A
EN class B
Conducted emission
Standard issue: capacitive coupling between switching
device and heat sink
- Filters
- Ferrite beads
- Gaskets
- Shielding
![Page 5: EMC: Common mode stromen veroorzaakt door Power Devices ... · Lex de Rijck. Acradac Power Electronics Event 20 juni 2017 ©Acradac EMC training and Consultancy 2 Common mode currents](https://reader033.vdocuments.site/reader033/viewer/2022050115/5f4c63612a9f07434e7ca130/html5/thumbnails/5.jpg)
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- Filters
- Ferrite beads
- Gaskets
- Shielding
Are they necessary?
![Page 6: EMC: Common mode stromen veroorzaakt door Power Devices ... · Lex de Rijck. Acradac Power Electronics Event 20 juni 2017 ©Acradac EMC training and Consultancy 2 Common mode currents](https://reader033.vdocuments.site/reader033/viewer/2022050115/5f4c63612a9f07434e7ca130/html5/thumbnails/6.jpg)
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Example 1: power factor corrector
Generally, the heat sink is connected to the ground.
This is the worst possible scenario
EN class A
EN class B
Return currents
from Cp
![Page 7: EMC: Common mode stromen veroorzaakt door Power Devices ... · Lex de Rijck. Acradac Power Electronics Event 20 juni 2017 ©Acradac EMC training and Consultancy 2 Common mode currents](https://reader033.vdocuments.site/reader033/viewer/2022050115/5f4c63612a9f07434e7ca130/html5/thumbnails/7.jpg)
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Example 1: power factor corrector
Return current from Cp makes a
large loop:
- increases Conducted Emission
- causes self-contamination
Big loops are bad for
EMC and should be as
small as possible
Reduce loop of the
return current
![Page 8: EMC: Common mode stromen veroorzaakt door Power Devices ... · Lex de Rijck. Acradac Power Electronics Event 20 juni 2017 ©Acradac EMC training and Consultancy 2 Common mode currents](https://reader033.vdocuments.site/reader033/viewer/2022050115/5f4c63612a9f07434e7ca130/html5/thumbnails/8.jpg)
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Reduce loop of the
return current
How?
![Page 9: EMC: Common mode stromen veroorzaakt door Power Devices ... · Lex de Rijck. Acradac Power Electronics Event 20 juni 2017 ©Acradac EMC training and Consultancy 2 Common mode currents](https://reader033.vdocuments.site/reader033/viewer/2022050115/5f4c63612a9f07434e7ca130/html5/thumbnails/9.jpg)
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Example 1: power factor corrector
The charge/discharge
current of Cp flows back
to its origin. This loop
should be small.
![Page 10: EMC: Common mode stromen veroorzaakt door Power Devices ... · Lex de Rijck. Acradac Power Electronics Event 20 juni 2017 ©Acradac EMC training and Consultancy 2 Common mode currents](https://reader033.vdocuments.site/reader033/viewer/2022050115/5f4c63612a9f07434e7ca130/html5/thumbnails/10.jpg)
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Example 1: power factor corrector
Connect the heat sink to
the negative voltage (will
have a mechanical
impact)
![Page 11: EMC: Common mode stromen veroorzaakt door Power Devices ... · Lex de Rijck. Acradac Power Electronics Event 20 juni 2017 ©Acradac EMC training and Consultancy 2 Common mode currents](https://reader033.vdocuments.site/reader033/viewer/2022050115/5f4c63612a9f07434e7ca130/html5/thumbnails/11.jpg)
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Conducted EMI-measurement:
EN class A
EN class B
Heat sink to gnd Heat sink to V-
EN class A
EN class B
Example 1: power factor corrector
![Page 12: EMC: Common mode stromen veroorzaakt door Power Devices ... · Lex de Rijck. Acradac Power Electronics Event 20 juni 2017 ©Acradac EMC training and Consultancy 2 Common mode currents](https://reader033.vdocuments.site/reader033/viewer/2022050115/5f4c63612a9f07434e7ca130/html5/thumbnails/12.jpg)
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PCB
Metal housing
connector
Plastic
stand-off
Parasitic capacitor (insulation
between heat sink and housing)
Common
mode
current
Loop area
Loop will radiate and common mode
currents will interfere on PCB
LF CM
currentHF CM
currents
Example 2
![Page 13: EMC: Common mode stromen veroorzaakt door Power Devices ... · Lex de Rijck. Acradac Power Electronics Event 20 juni 2017 ©Acradac EMC training and Consultancy 2 Common mode currents](https://reader033.vdocuments.site/reader033/viewer/2022050115/5f4c63612a9f07434e7ca130/html5/thumbnails/13.jpg)
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PCB
Metal housing
connector
Parasitic capacitor (insulation
between heat sink and housing)
Loop area
conducting stand-off,
connected to the
ground plane
Example 2
![Page 14: EMC: Common mode stromen veroorzaakt door Power Devices ... · Lex de Rijck. Acradac Power Electronics Event 20 juni 2017 ©Acradac EMC training and Consultancy 2 Common mode currents](https://reader033.vdocuments.site/reader033/viewer/2022050115/5f4c63612a9f07434e7ca130/html5/thumbnails/14.jpg)
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PCB
Metal housing
connector
Parasitic capacitor (insulation
between heat sink and housing)
Loop area
A metal clip is even better
Example 2
![Page 15: EMC: Common mode stromen veroorzaakt door Power Devices ... · Lex de Rijck. Acradac Power Electronics Event 20 juni 2017 ©Acradac EMC training and Consultancy 2 Common mode currents](https://reader033.vdocuments.site/reader033/viewer/2022050115/5f4c63612a9f07434e7ca130/html5/thumbnails/15.jpg)
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On a larger scaleParasitic capacitor
between IGBT module
and heat sink
(6 nF!!!)
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The resonance is caused by the parasitic capacitance and the
induction of the return path
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Common mode return currents
The capacitors are Y-Capacitors
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Common mode return currents
Without Y-capacitors With Y-capacitors
![Page 19: EMC: Common mode stromen veroorzaakt door Power Devices ... · Lex de Rijck. Acradac Power Electronics Event 20 juni 2017 ©Acradac EMC training and Consultancy 2 Common mode currents](https://reader033.vdocuments.site/reader033/viewer/2022050115/5f4c63612a9f07434e7ca130/html5/thumbnails/19.jpg)
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Common mode return currents
Without Y-capacitors With Y-capacitors
Results differ, depending on the circuit
2A/div
![Page 20: EMC: Common mode stromen veroorzaakt door Power Devices ... · Lex de Rijck. Acradac Power Electronics Event 20 juni 2017 ©Acradac EMC training and Consultancy 2 Common mode currents](https://reader033.vdocuments.site/reader033/viewer/2022050115/5f4c63612a9f07434e7ca130/html5/thumbnails/20.jpg)
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Difference in measured radiation
Without Y-capacitors With Y-capacitors
(Not related to CM)
![Page 21: EMC: Common mode stromen veroorzaakt door Power Devices ... · Lex de Rijck. Acradac Power Electronics Event 20 juni 2017 ©Acradac EMC training and Consultancy 2 Common mode currents](https://reader033.vdocuments.site/reader033/viewer/2022050115/5f4c63612a9f07434e7ca130/html5/thumbnails/21.jpg)
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Common mode return path
• Visualize the parasitic capacitor between switching component and
cooling surface
• Analize the path of its charge/discharge current
• Reduce its loop
![Page 22: EMC: Common mode stromen veroorzaakt door Power Devices ... · Lex de Rijck. Acradac Power Electronics Event 20 juni 2017 ©Acradac EMC training and Consultancy 2 Common mode currents](https://reader033.vdocuments.site/reader033/viewer/2022050115/5f4c63612a9f07434e7ca130/html5/thumbnails/22.jpg)
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Reducing loops always works
![Page 23: EMC: Common mode stromen veroorzaakt door Power Devices ... · Lex de Rijck. Acradac Power Electronics Event 20 juni 2017 ©Acradac EMC training and Consultancy 2 Common mode currents](https://reader033.vdocuments.site/reader033/viewer/2022050115/5f4c63612a9f07434e7ca130/html5/thumbnails/23.jpg)
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Buck converter on PCB
Manufacturer’s reference design Proper layout with reduced loops
Radiated emission
![Page 24: EMC: Common mode stromen veroorzaakt door Power Devices ... · Lex de Rijck. Acradac Power Electronics Event 20 juni 2017 ©Acradac EMC training and Consultancy 2 Common mode currents](https://reader033.vdocuments.site/reader033/viewer/2022050115/5f4c63612a9f07434e7ca130/html5/thumbnails/24.jpg)
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Analyzing the return currents and
reducing their loops can easiliy decrease
EMI with 20-25 dB without the need for
filters, ferrite beads or shielding
![Page 25: EMC: Common mode stromen veroorzaakt door Power Devices ... · Lex de Rijck. Acradac Power Electronics Event 20 juni 2017 ©Acradac EMC training and Consultancy 2 Common mode currents](https://reader033.vdocuments.site/reader033/viewer/2022050115/5f4c63612a9f07434e7ca130/html5/thumbnails/25.jpg)
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Want to know more?
• Courses are available from:
www.acradac.com
or visit the stand