Questions tagged [emi-filtering]
For questions about the filtering of undesirable electromagnetic interference (EMI). Consider using in conjunction with related tags, as applicable (e.g. use with "switch-mode-power-supply" for questions about the filtering of EMI produced by a switch-mode power supply).
343
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Best placement of bridge rectifier to allow DC/DC convertor to become AC/DC convertor. Does this inhibit surge and EMI performance?
I am trying to use the power supply: CQB50W12-72S12 with AC power without degrading the performance of its recommended filter and surge components. 120VAC peak voltage is 169V and I am worried that ...
- 422
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EN61000-4-5 Surge protection of PCB power supply
I am trying to better understand how EMC testing is simulated and passed. The datasheet of the CQB50W12-72S12 says it pass level 4 line to earth 4kV; and +- line to line 2kV with just a TVS diode (...
- 422
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Do I need an EMI Input Filter if source is within PCB?
Newbie here.
I'm designing a circuit based on PoE (MYBSP0122BABFT). It has a 12VDC output. It will be used on various loads mounted on same PCB.
One of the loads is a 12VDC to 24VDC module (TEL 12-...
- 413
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PCB layout and power planes
Currently I am working on PCB layout of previous question asked on this site.
This board has only 2 layers and will be produced as an home-made prototype.
Voltage: 12V
Current: 1A
This is the ...
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Differential Mode EMI Filter Design for DC Power Input Noises
https://www.murata.com/en-us/products/productdata/8796777775134/ENFH0008.pdf
https://www.digikey.com/en/products/detail/murata-electronics/BNX022-01L/1825573
Hi everyone, I try to understand this ...
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With modern connectors, is the metal shell used as a conductor?
Does the metal shell of a connector, such as USB and HDMI, serve a conducting purpose? The metal shell of my TV's HDMI terminal is corroded. Should I make effort to have it contacting and conducting ...
- 59
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How can I simulate output impedance of EMI filter with LTspice?
I use Wurth EMI line filter spice module, but I can not simulate the same attenuation and frequency wave of specification. And how can I simulate the output impedance of filter?
I update the ...
- 11
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2
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Can COM and earth be connected thorough the PCB ground pin?
I'm using an AC/DC switching supply (Meanwell PD-45) with the following schematics:
The Frame Ground (FG) is connected to the metal chassis of my device with a screw. The output of the switching ...
- 31
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51
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TVS on 5V external input
I am transferring 5V ext. through a robot which is a faraday cage of sorts.
the line will be around 1.2 meters (4 feet).
will the TVS be good for this application? or should I consider a different ...
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73
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Why do my MAX6675 boards keep going crazy?
I have a simple ESP32 dev board based setup connected to two (going to be three soon) MAX6675 breakout boards. The ESP32 is powered by a 12V DC adaptor connected to its extension board.
Two of them ...
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Protection of the power supply input from high voltage pulses
I am assembling a power supply for xenon arc lamps. I use a simple welding inverter as a stable current source. I use the presented scheme.
The ignition circuit generates pulses up to 25-30 kV for a ...
3
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2
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345
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Simple Bootlamp for a EV Bike
We are designing a simple 12V DC bootlamp (lamp to be installed in the boot) for an EV bike project.
(Vin : 12V DC)
Q1) Is the design OK? Any recommendations on it?
Q2) Is EMI/EMC applicable to such ...
- 101
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LTspice MOV tutorial/help
I am looking at the availability of the pictured component on LTspice and cannot find it when I type it in the component library search. Please let me know the component symbol name or if I need to ...
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How power plane acts as a path for the return currents
In some pcb stackup's I can see that the power plane is given as reference to signal layers.
I have some questions regarding this.
May I know in that case how the return current flows.
Assume all my ...
- 1,595
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infrequent USB dropouts on SBC
I have a full speed USB audio device connected to the USB port on a SBC running Ubuntu Linux. I'm acquiring data over this connection and I need 24/7 uninterrupted data acquisition. If the USB ...
- 319
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173
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Estimate susceptibility of circuits to external electrical field strength
I will be soon testing a product to an electric field spectrum requirement (i.e. in the 100's of dBµV/m vs MHz), and it shouldn't be a problem because of how small the values are compared to the ...
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Confining signal using stitching vias on a 2 layer PCB
I have read in some questions (for example: Via Stitching on 2 Layer PCB when top layer is not fully ground pour ), that stitching vias are useless when one's PCB only has 2 layers, however people do ...
- 257
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How to protect signal routed via patch wire against EMI / RFI / other signals?
I have a delicate problem which I'm not sure how to solve properly due to my limited electronics education: I have an old computer system from the 90s which contains an additional module replacing its ...
- 101
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40
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EMI issues with CNC TIG welding machine
We're having some super weird issue with a CNC TIG welder that we're building.
To start the arc (and complete the circuit for DC TIG welding), bursts of high voltage (making a taser-like sound) at a ...
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2
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132
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variable speed drive interfering with distant PHEV charger
I am using a generic variable speed drive for a water pump.
About 5% of the time that I run it, it stops my BMW 530e PHEV from charging. What is the most likely cause? What measurements can I make to ...
- 397
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How to find the cutoff frequency of my EMC filter
I am seeking assistance in understanding the calculation process for EMC filter capacitors and inductance. I comprehend that this filter operates with a cutoff frequency, and based on this cutoff ...
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Equivalent Circuit of CM EMI filter [duplicate]
Actually, someone already asked this question before.
But I have another question here.
This is the diagram of an EMI filter in both CM and DM filters:
This is the equivalent circuit of the CM filter:...
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80
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A6211 LED driver Radio interference
I am working on a small side hobby project where I am using a A6211 LED driver,
But the LED driver is causing quite a lot of interference on a radio, I tried using shielded cables, add ferrite cores, ...
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When connecting digital GND to chassis with a capacitor, what voltage rating should the capacitor have?
From testing the sensitivity of my device (USB communication) to EM noise, I figured out that if I use a capacitor to connect my digital GND to the chassis I can get rid of the noise (I think that's ...
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Power traces for switching regulator on PCB
When designing a PCB that has a switching regulator IC, is it better to have the power traces to the IC wider or narrower?
I read that the general rule of thumb is to keep the traces as short and wide ...
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140
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Equivalent circuit of CM and DM EMI filter
This is the diagram of an EMI filter consisting of both CM and DM filters:
This is the equivalent circuit of the CM filter:
Could someone explain why in the equivalent circuit, it's Lcm and not 2Lcm?...
- 57
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14
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Key input line, picks noise up from 220V lines and automatically triggers
I made an IR repeater board which records an IR command from a remote control and emits it every time an external key is pressed. It is used as an alternate remote control for a projector so the main ...
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How to fix Dirty Electricity on an Inverter
I have been testing my inverter (Victron pure sine wave) as well as a few others with my Trifield EM100 meter. Most that I have tested show extremely high measurements from over 1,000mVp-p to well ...
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My Arduino project only works when the car is off. Why is this the case?
I have been all over the internet and have asked a few people why this is happening. Hopefully I'm at the right place.
My Arduino project consists of reading serial data from my car, which is OBDI-...
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Good book on EMC and EMI [closed]
I'm looking for a good book about EMC and EMI.
There are plenty of books talking about norms and standards, but I'm looking for a book focusing on understanding the logic and physics behind it. And ...
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Finding frequency response of inductive EMI sensor
I'm building an EMI sensor and trying to understand how it's done with the Elektrosluch. Here's the full schematic but this is the part I'm concerned about:
simulate this circuit – Schematic ...
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Trying to pass EMC Pre-Compliance Test without the use of electrolytic capacitor on DC/DC Converter
I’m designing a EMI filter for a DC/DC Converter Circuit and having trouble suppressing noise on 1.5-1.8MHz range. Usually an easy fix would be snap in a 100-220uF Electrolytic cap would do the trick ...
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63
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Picking a pi- or T-filter to suppress radiated interference on supply line
Normally when I design suppression filters I use π-filters for data lines and T-filters for supply lines as supplies generally have a lower output impedance than data pins.
I now have the situation ...
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57
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Transistors falsely latch with EMI
I have a very basic NPN - PNP latching circuit:
[Sorry for the upside down image]
The latch initially is off, and when the op_amp_Signal_and_latch turns on, the ...
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Connecting computer and motor driver grounds
I am designing a robotic system and seem to be having a ground issue whilst working with motor drivers.
To improve system stability and for EMI concerns, I have split the power and signal using an ...
2
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1
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585
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Input filter to reduce conducted emissions caused by DC/DC converter
This material from ROHM explains the input filter design for a DC/DC converter.
The filter circuit is given below.
I understood the design of Lf, Cf2, Cd and Rd.
If you see the 3rd page (design of ...
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Wouldn't placing capacitors between the input and output of an isolated DC-DC converter defeat the purpose?
It is common to recommend the placement of capacitors between the input and output sides of an isolated DC-DC converter, such as in this example layout:
I understand that the purpose of this is to ...
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4
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Can slower switching edges worsen the EMI behavior?
A common method (as stated in many electronic design articles/books) to reduce EMI (radiated emissions) of any fast switching circuit is to slow down it's switching edges (reduce tr/tf). This ...
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Common mode choke impedance selection USB 2.0 Data line [duplicate]
Below schematic shows a USB connection diagram.IN this you can see a common mode choke (DLW21HN900SQ2L)
The common mode choke impedance is given as 90 Ohms @ 100 MHz .The USB is working at 480Mbps.
I ...
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Non-isolated DC/DC converter
I am integrating a non-isolated DC/DC converter from Mornsun in one of our designs.
We are trying to stick to the typical application schematic:
However, two questions dictated by the limited space ...
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Protection for PCB inputs and outputs - ESD, short-circuit, EMI
I have a pretty simple board that wires together an Arduino and a screen. It has 3 terminal blocks - power, optical encoder, and stepper outputs (just signals).
Stepper and encoder signals are in the ...
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5
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Common mode inductance without earth
Here is a schematic from TI:
I also attached a picture of the schematic part concerned:
I do not understand why there is a common mode inductance. (But I know that there is a reason :) I just do not ...
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336
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4 layer PCB stackup for better EMC
I want to design a PCB with few "low dropout linear voltage regulators", which would be used to power some sensors we are building. None of the parts on the PCB is expected to do any high ...
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Does filtering and protecting the ground with an inductor, capacitor, and TVS have a benefit?
Let's assume a situation where you have a symmetrical power supply with the following output (in bracket is the net name, see the picture):
+15V (+15V_DCIN)
-15V (-15V_DCIN)
GND (GND_DCIN)
Earth (GND ...
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Frequency response of LC filter with resistance in parallel with the capacitor
The following is the diagram of interest:
The impedance of the filter is:
$$Z_o=\frac{R_f L_f s}{R_f L_f C_f s^2+L_f s+R_f}$$
and the bode plot with all different components and the total impedance ...
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123
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Different type of capacitors
How can I distinguish between filter capacitors, decoupling capacitors, and bypass capacitors? What is the most basic and important difference in their functionality?
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Ferrite bead in series with buck inductor
Background
When filtering DM noise from SMPS, I have often used LC filters in the past. One thing that happens with regular inductors though, is that very high frequency (>100 MHz) switch noise ...
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Phase response in MATLAB simulation doesn't match the book
I am trying to replicate a result from a textbook that I am using to study input filter design for buck converters.
The parameters for the converter and filter are as follows:
D = 0.5
L = 100 μH
C = ...
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1
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EMI filter SMPS
I was wandering how the main voltage coming from main in SMPS is not attenuated by the EMI filters. This is the input stage of a AC/DC SMPS by TI (https://www.ti.com/tool/PMP11064):
Maybe I'm wrong ...
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Interference from compressor pressure switch
In my CNC machine, I have a small air compressor and a spindle motor VFD connected in same 240 VAC outlet.
Whenever the compressor switches on or off, the VFD reports "OC-o" error. According ...
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