PE #48: Stabilizing a Closed-loop DC-DC Converter considering EMI Filter Effect

[@MarcosAlonsoElectronics]

All files are available at: github.com/marcosalonsoelectronics/PE48

[@jiangjianhuang5177]

Always Great video course! In addition to add the damping RC, how about adding a damping resistor paralleled with Lf? Which one is better?

[@MarcosAlonsoElectronics]

Thanks for this excellent question. You are right, this is another way of damping the filter. Since the resistor in parallel with the inductor does not bear any DC voltage the losses are also low. The problem is in the deterioration of the filtering effect, which at the end is the main function of the EMI filter. Intuitively, when we place a resistance in parallel with the inductance, we are bypassing the inductor so that we are giving an easy path for the converter harmonics to go into the grid. Quantitatively, if we analyze the response of such a filter, we will find that a zero appears at w=Rf/Lf (Rf being the resistance in parallel with Lf), so that the attenuation at high frequency will have a slope of only -20 dB/dec instead of -40 dB/dec (the zero compensates the effect of one of the two poles). A solution to this is to add another inductor in series with the resistance. I leave this for you to look into. It could be the topic of a future video too. There are many other filter topologies that we can find in the literature, including active filters. Thanks!

[@Eng.A.B]

Hi Mr. Alonso, I am trying to figure out how to solve this event but rather with an offline application of a boost PFC. Working with full load and 230V the circuit and the control is working just fine, noise level are damped and great resuslts are achieved, but as soon as the circumstances get a lttle tight (using minimum voltages whereas there is more stress with the input current), the output voltage doesn't regulate properly at the level it was dimensioned for. The simulation is working around a controller ic. Therefore as you explained very well, there are 2 possibilites to undergo this happening. First would be to execute some changes on the part of the compensator. Second would be an inclusion of a damping network. The 2nd option didn't work. and the first one is so far changeable through the sense resistor linked to input of the pfc but in this case the input current rise quite a much. What do you advertise in this case ? Kind regards Aziz

[@MarcosAlonsoElectronics]

Hello, thanks for watching the channel. You have to carefully study the interaction between the filter and the PFC converter. This video can be helpful in the modelling of the PFC stage: PE#9 kzbin.info/www/bejne/eaHWnWV-o7yIic0

[@isacdaimary9908]

How may I reach you in gmail Sir? I would like to clear few of my doubts

[@MarcosAlonsoElectronics]

My gmail address is [e-mail]. But if possible, make your question on the comments' section of the videos when possible so everybody can benefit from the Q&A. Thanks for watching the channel!

[@biswajit681]

Hi sir any update on your new book?

[@MarcosAlonsoElectronics]

Hi, thanks for asking. I am still working on it. I will need a few more months ...