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15 articles
Electronics
Optocouplers are widely used in isolated power supplies to transfer feedback information across an isolation barrier. In schematics, they appear as a clean and robust solution: no galvanic connection, clear separation between primary and secondary, and good noise immunity. In practice, optocouplers
Francesco Poderico · · 3 min read
Electronics
Introduction Varistors (typically MOVs) are widely used on mains lines for surge / transient protection. Under normal conditions they are passive, but when high‐voltage transients (switching surges, lightning induced, line overvoltage) occur, the varistor conducts, clamps the voltage and absorb
Francesco Poderico · · 2 min read
Electronics
In one of my previous blogs, I discussed the importance of adding common mode filtering to power cables. Nevertheless, even the best filtering may not be enough to pass CE. When this occurs, most EMC testing houses recommend using "low frequency" ferrites, like Fair-Rite's excellent Material 31, whi
Francesco Poderico · · 3 min read
Electronics
There is a feeling in me that sometimes the old books are better than the new ones. As an example, a book by Hnatek called Design of Solid State Power Supplies might be one of those gems that shouldn't be missed in your library if you are interested in solid-state power supplies. This old book s
Francesco Poderico · · 3 min read
Electronics
PDN design is not an easy task, and it can be challenging. One of the most common mistakes is to follow so-called "rules of thumb" that work 90% of the time, but not 100%, so it is your responsibility to determine when these rules are valid or not. Adding a 100 nF capacitor to each power pin in para
Francesco Poderico · · 2 min read
Electronics
In a previous article, I discussed the common mode coupling on the PoE (Power Over Ethernet) DCDC converter that I discussed a few months back. It is a similar mechanism that happens when we design our own AC/DC converters. Based on some of the comments that I have received, it seems clear that for
Francesco Poderico · · 2 min read
Electronics
EMC is considered by many to be a "black magic" for a number of reasons. In some cases, it may be the case that you obtain unexpected emissions from components you were not expecting to have. Oftentimes, the problem lies in the fact that we tend to ignore what we call "parasitic components" such as
Francesco Poderico · · 2 min read
Electronics
I visited Scotland on holiday, a beautiful country! There is so much history in Edinburgh, and I also enjoyed visiting Glasgow. It is difficult for a consultant engineer to stop working entirely, as you can imagine. I received a call from an IT company that already has a product on the market, and
Francesco Poderico · · 2 min read
Electronics
A few years ago, I worked on digital radio for a customer. It was a very complex design, but the reward for an electronic engineer such as me was enormous. It was a pleasure to work on every single part of the design. As I recall, I bought a few books to ensure that I was doing a good job, and the
Francesco Poderico · · 3 min read
Electronics
Those of you who are reading my post know that there is not much 'black magic' behind EMC and that there is always an explanation for why we fail during the EMC testing process. As a result of having a strong understanding of EMC, it is extremely satisfying to be able to pass the EMC testing for bo
Francesco Poderico · · 3 min read
Electronics
As we have seen in parts 1, 2, and 3, the input current loop of a DCDC converter affects both conductive and radiated emissions. Furthermore, the output current loop primarily affects radiated emissions.We then learned how an R/C snubber works and how antiparallel output capacitors can reduce radiat
Francesco Poderico · · 2 min read
Electronics
In the process of creating a new product from scratch, I always add components that I may not need in production when I am designing it. As an example, it does not cost anything to add an 0-ohm link or a "does not fit" capacitor in a critical spot where we think we might need them in the future (in
Francesco Poderico · · 3 min read
Electronics
I had the pleasure of working with a customer a few years ago, who was ready to launch his product on the market. My suggestion was to go for full CE compliance before the test and to contact me only if there were any problems that occurred during the test. As the EMC house was just 15 minutes away
Francesco Poderico · · 3 min read
Electronics
When we design electronics, there are a few things we shouldn't skip. Often, CEOs and CTOs pressure us to design things quickly. But what is the cheapest option? Should we spend one or two extra days analyzing the board or should we run it a second time? My goal today is to discuss some design analy
Francesco Poderico · · 2 min read
Electronics
I spent several stimulating days last week performing EMC testing on one of my most challenging designs in the past two years. This is the first time EMC compliance has been achieved in a topology of medical products. For this particular design, the EMC house was my most critical testing location; I
Francesco Poderico · · 2 min read
