EMC Filter Design Part 3: Input Filter Stability and Middlebrook

The first step in EMC filter design usually is to make sure our filter does not interact with the power supply control loop. In this video we explain Middlebrook's stability criteria in simple terms to help us design our filter. For further information on Biricha's EMC filter design workshop please visit: www.biricha.com/emc

[@thundrwaffle]

I am learning so much more from you than i am in my classes thank you!

[@darrellhambley7245]

One important thing to note is that you must meet the Middlebrook criteria at the worst-case lowest impedance point which is at the maximum load and at minimum Vin.

[@DenkOtomasyon]

Thank you for the information. EMC is a big problem that should be understood by the society. We need to protect our energy as we need to protect the nature. EMC is the reason behind many malfunctions that can not be explained. I wish all success in your work

[@jamescoleman4747]

This is very well delivered .Top notch instructor

[@mikemike7001]

Steve Sandler's book referenced as the source of the formula for estimating Zin is probably his "Switched-Mode Power Supply Simulation with SPICE".

[@tux1968]

Thanks for the good presentation. I looked up and saw that your Bode 100 cost $10,000 USD; more than I can afford :-) But i'm not sure what that yellow device is. It sounded like you were calling it a "Listen"?

[@tux1968]

Found the answer and thought I'd share.. he's actually saying "LISN" which stands for "Line Impedance Stabilization Network". A standard device used when testing devices for EMC/EMI compliance. The Wikipedia page says more: en.wikipedia.org/wiki/Line_Impedance_Stabilization_Network

[@johnkyingilisi4395]

Can you please introduce yourself as Ali. Its a beautiful name. As for getting rid of harmonics in and out of power supplies in particular the getting rid of EMC's induced in conductors by way of common mode chock for me that was a gift. Love and respect.

[@xinpengyang-dz5rt]

It's useful,I want to have more and more vedios explian how to cauculate the devise

[@MrVallagon]

Excellent videos, love it!

[@mikemike7001]

Efficiency in the Zin calculation, represented by the Greek letter nu, is expressed as a fraction. For example, for a 93% efficient power supply, nu = 0.93.

[@MrVallagon]

The efficiency is the Greek letter Etta

[@hoivien3001]

Thank you Sir.

[@qzorn4440]

it would be interesting to see the controlling electron travel path going in the LCR circuit and back out. like mouse in a maze. thanks.

[@vahhabmohammadi8839]

I think in the simulation the the reds are phases and the blues are Gains. So: correct gain: Solid Blue - correct phase: Dashed Red - after adding incorrect impedance which is close to Zin of power supply: Gain: Dashed Blue - Phase Solid Red.

[@CATA20034]

Nope, Gain is with solid RED and BLUE.- Dashed line is the phase.

[@bahadrguven6268]

what is the Zo ? LC filter ouput impedance or Tranmission impedance or Z22 paramters

[@anasahmed9190]

I thik he used the characteristic impedence insted of the circuit imedence, which doesn't make a lot of sense.

[@simonbourguigne9988]

How do you think about Middlebrook criteria when you have 2 PSUPs in parallel after the filter?

[@Duracellmumus]

Can we damp the LC filter resonance with some resistor added paralel to C ?

[@theironwoodtable]

1. What is the injection transformer connected to? 2. What are the probes connected to?

[@Ronyllsky]

What is the purpose of school again?

[@PhillipS85]

What is the source/reference of the PSU input impedance formula Zin = (Vin^2 * efficiency) / Pout?

[@mikemike7001]

Seems to be Steve Sandler's "Power Integrity" book.

[@mikemike7001]

More likely Sandler's "Switched-Mode Power Supply Simulation with SPICE".

[@darrellhambley7245]

Current, Iin = Pin/Vin. Zin = Vin/Iin or, Iin = Zin/Pin. Substitute Iin = Zin/Pin in the first equ and you get Zin = (Vin^2) / Pin. Now substitute Pout = Pin * eff. (Impedance Zin is actually a negative number at the operating point) See? It' simple algebra. Anyone who has taken basic EE101 in college should be able to do this.

[@anunarayanr3993]

how to find the cutoff frequency ?

[@rolandoaguilera3114]

input filter cutoff frequency should be less than power supply output filter cutoff frequency

[@indraverma151]

Please explain easy way. I don't understand what u want to say.