Questions tagged [common-mode-choke]

A type of choke in which two coils are wound on a single core in order to pass differential currents while blocking common mode currents.

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Paralleling common mode chokes

Regular chokes can certainly be used in parallel so that multiple smaller chokes with a lower current rating can be used. But does this also work for common mode chokes? I would assume that ...
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Common Mode Choke Usage

I am using a ACM70V-701-2PL-TL00 Datasheet to attempt to filter out A/C ripple in an in-vehicle audio device. I've run the input 12v through one channel of the ...
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Common mode choke - Why only impedance?

Why are most common mode chokes only given with a impedance curve, inductance at a specific frequency and current rating (this is clear😅). Wouldn't be S-parameter better? I know it's more work, but ...
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Common mode choke - alternative part

I have sent out a PCB for manufacture and the manufacturer has suggested an alternative part. The application is a mains powered (220V AC 50Hz) device. The common mode choke is being used to filter ...
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Can CM choke windings be used for LC filter at the output of SMPS or DC-DC Converter?

I need to filter out switching noise at the output of SMPS/DC-DC converter with an LC filter. I have a bunch of CM chokes lying around. Can I use a common-mode choke: with both CM windings connected ...
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How to choose a common mode choke for ethernet?

I'm currently working on a design which contains gigabit ethernet. Due to some weird size constraints, I can't use a magjack or one of those transformer ICs, so I'm using discrete magnetics. I've ...
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Use of common choke with more than 2 wires

I've been looking around and I couldn't really get a good answer to this question, not even in Henry Ott's book (so far), so here it goes: What is the best approach when there is the need to place a ...
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Common mode,differential mode choks Selection,Calulation EMI

Im trying to measure an unknown common mode choke with the shape of toroid and color of green. I need to learn its parameters(ferrite core, permeability,inductance and so on). According to the ...
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DC-DC fixed voltage output converter and EMI Design, where to begin and roadmap?

I'm in a group of people tasked to design and implement a DC-DC converter with an output voltage of 24 volts, with an input voltage from 9 to 36V, with an EMI filter, which must comply with the ...
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Common-mode choke on LTSpice

Can someone suggest to me how to select a three-phase common-mode choke with self and mutual inductance in LTSpice?
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Isolated BNC connector in metal chassis, EMC considerations

I consider using an isolated BNC connector for a precision application, in which the BNC Shell will be either grounded via an internal switch or used as a Guard electrode. The motivation behind this ...
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Why are common mode chokes with 90 ohm @ 100 MHz recommended for USB 2.0 Hi-Speed data lines?

When one looks at common mode chokes for USB 2.0 applications choke manufacturers always recommend CMC with a common mode impedance of 90 ohms @ 100 MHz. Example How does this relate to USB 2.0 ...
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How to choose DC resistance parameter of a USB 2.0 common mode choke?

How do i know whether i have to choose a bigger sized common mode choke with lower DC resistance for USB 2.0 D+/D- lines or using a smaller one with higher DC resistance is also just ok? In fact there ...
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Why do common-mode EMI filters lack damping networks?

I've been going through the design of a few different EMI filters, mainly for buck converter inputs. In many cases the leakage inductance of the CM choke can provide enough inductance for the ...
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If a common mode choke (CMC) is added between PWM signal and PWM return without additional chassis return path, will it act as a common mode filter?

In this schematic a common mode choke is added between PWM output and PWM ground (return path.) There is no other return path to load (like through parasitic capacitance to chassis.) In this case, ...
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What Common Mode Choke choose for EMI filtering at 250v

I'm designing a PCB with a microcontroller that have to handle 3 Relays. The main power source is an AC Inlet socket 250v, the maximum current for all the circuit from this source is 15A (I included a ...
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Common mode filtering a shunt: "active" vs. "passive" strategies (diff. amp vs. common mode choke)

If you are trying to observe a relative small voltage across a shunt resistor and you are finding common mode noise interference induced in the signal, in what cases would you choose to use something ...
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Helping identifying a common mode choke

Seeking help to identify the following common mode choke. The best guess is it a part from Sumida Corporation. This part is from a refrigerator. Any of the following information is greatly ...
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Why common mode filters are usually found on AC input stage and not the output stage of an isolated smps?

Title explains the question, I believe.
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Isolated DC-DC common mode choke without shunt?

I was reading a page on the Recom site (https://recom-power.com/en/rec-n-very-low-noise-filter-for-isolated-dc!sdc-converters-46.html?3) where they devised a filter setup to achieve very low noise on ...
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Is my ultrasonic cleaner using a common mode choke as an AC to DC converter?

I am repairing an ultrasonic cleaner with a faulty circuit board. It has a blown out diode and capacitor that needs to be replaced. The board, however, has me curious and confused as to its function. ...
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CAN Physical layer - Choke evaluation

I have my CAN configuration as shown in the below drawing(automotive application), the uC that I’m using has both the CAN controller and the physical layer transceiver built-in so I don’t need a ...
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Purpose/Difficulties of having a common mode choke

This question is related to common mode choke. I know I have asked this question a couple of times in this forum and I have also read related questions and answers. But I am not able to get the total ...
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How is the differential mode noise suppressed by adding a capacitor across the Lines

I was reading about the common mode noise and differential mode noise. I don't understand how a differential mode noise gets coupled and how adding a capacitor across the line will help. I ...
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Are external components required for HLK-PM01?

Apologies in advanced as this is kind of a vague question and due to my lack knowledge in this specific sector. I'm designing a circuit using a HLK-PM01 as the power supply which is a 3W AC-DC ...
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EMI Filter - DC DC Converter No Differential Mode Filter Outlined

I am currently looking at installing a DC-DC Converter. https://www.xppower.com/Portals/0/pdfs/SF_QSB300.pdf The datasheet outlines a recommended EMI filter as so: My question is as the datasheet ...
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EMI Filter design capacitors problem

I'm trying to design an EMI filter for a 3-phase induction motor driver. I've looked at some example filter designs but in one of them I couldn't understand the capacitors and resistors what they are ...
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Common Mode Choke question

I have one question which I encountered during usage of common mode choke. Question : "If a common mode choke is used on the main power / ground input, ensure that no I/O circuits effectively bypass ...
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How to design a CMC (Common Mode Choke) footprint to allow no-pop solution

How would you design in CMC's with a 0504 (1210 metric) 4-lead package to allow for a no populate (do not pop, DNP,DNI) solution? I am thinking 0402 0ohm (zero ohm) resistor but cannot picture the ...
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Low-Speed CANbus Common-Mode Choke Insertion Loss

I'm designing a low-speed CAN transceiver breakout-board (schematic below) and I'm trying to select the proper choke to use to reduce common-mode noise. I've found a few common-mode chokes meant ...
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What is a power factor correction choke (PFC choke) and how does it work?

They Exist This Link at Newark displays "Power Factor Correction Chokes", which I did not know existed. I have a linear motor which I suspect really needs power factor correction. Please tell me ...
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PCB Layout - Common Mode Choke

Why it is recommended to not to add copper planes and to avoid routing of signals under the common mode chokes?
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Common Mode Noise on Differential Lines Driven Against Chassis GND

How is common mode noise filtered on differential lines that have a noise source that is driving them relative to chassis GND? I drew a picture of what I am imagining below. Imagine a PCB with ...
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Common Mode Chokes

Consider the following : If we need to figure out the input impedance seen by the source, it will be equal to --> Zin = jw(30u) -jw(27u)+1k+jw(30u)-jw(27u). The first two terms are due to the drops ...
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Common mode filters effectiveness

As we know, there are many types of common mode filters that can be implemented. One of this type is a single element topology where this element can be a series impedance element (usually R or L or ...
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Common mode choke selection for 5V 1A smps power supply

I am designing a flyback smps power supply circuit and having trouble deciding the exact common mode choke that I should use. My power supply specs are as follows: Input - 80-270 VAC 50/60 Hz Output - ...
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dual rail DC/DC convertor and CMC

I have a DC/DC convertor that tales 5V and makes + 15V and -15V rails My question is how to place common mode chokes to reduce common mode noise. Should I place 3 of them (1 on the negative to Gnd , ...
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Common mode choke parameters CAN circuitry - split termination concept

I am trying to the understand the important parameters of a common mode choke that will be placed at the CANL and CANH lines of a transceiver. First parameter: Impedance as function of frequency - I'...
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Using CM Y capacitors after CM chokes

Below shows the effect of a CM choke on the CM interference: And below is a CM choke with ferrite ring for a USB cable(there is no capacitor installed): In above examples there are no Y caps to ...
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Can a common mode choke be used at the output of an SMPS?

If there is CM EMI on DC power supply lines, can a CM choke be used at the output of SMPS supply? Im asking because all CM examples I saw are for AC power lines.
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Why are there different ways of winding a common mode choke?

Below shows two types of CM choke winding: Is there a difference betwween two in applications? They are both used in literature, yet I havent seen a single sentence abou the digg
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Is this setup proper to observe the attenuation effect of a common mode choke?

I'm trying to prepare a setup to see the effect of this torodial ferrite ring.. Even though I still didn't understand what way to wind wires to obtain a common mode choke(I saw differnt ways of ...
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common mode choke - symbol and orientation

I was wondering why there are different symbols for common mode chokes and if/how they affect the way I have to connect them. (upper image incorrect but left for understanding the comment from @...
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Common mode chokes in series

I am designing an ultralow noise audio board. On the first PSU PCB (just talking after bridge) I have a CMC to remove switching noise on diodes to undetectable levels (with plenty of capacitance for ...
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common mode choke and derating vs current

I have a CMC that has is rated at about 1kR at 100Mhz at 3A However my circuit uses only 1A. Do I need to derate my inductance since there is less current flowing through it ?
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x2y caps and common mode chokes (using both)

I am designing a ultralow noise PCB board. Common mode noise has to be minimized, so I have a question I am planning to use a CMC on power input and to further decrease the common mode noise I also ...
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Choosing toroid for FM dipole choke

After several failed attempts to buy simple rabbit ears for FM tuner I decided to make my own. Now, I have zero knowledge in RF circuits. While finding the formulas for pole length wasn't hard, I ...
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USB chokes for USB power

We are designing a ultra low noise USB 2.0 hub. I am thinking to add a common mode choke to + and - of the USB connector, in addition to the D+ and D- choke to remove the common mode noise. I am ...
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How do I build a three-phase common mode choke in Matlab simulink?

How do I build a three-phase common mode choke in Matlab simulink? Should I use the mutual inductor?
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Does a 3-winding common mode choke work on PE wire

Update It was pointed out the PE wire has to carry large current in fault condition so using a 3-phase CMC is problematic. In IEC62368-1 (2nd edition) chapters 5.6.3 and 5.6.4 it is implied that the ...
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