Kaivan Karimi – Dir. of Global Strategy, Microcontroller Group, at Freescale

Weekly PULSE Issue

Kaivan Karimi – Dir. of Global Strategy, Microcontroller Group, at Freescale

Featured Engineer

Interview with Christophe Basso

Christophe Basso

Christophe Basso - Engineering Director at ON Semiconductor (France)

How did you get into electronics/ engineering and when did you start?

I started electronics when I was around 14. At that time, there was a plethora of hobbyist magazines describing how to build light-show stuff (so-called psychedelic modulators), power amplifiers, radio emitters etc. Friends were also bringing me things to repair and that’s how I started to learn electronics. I was also collecting antic radios from which I remember the glowing magic eye tube UM34. Trying to fix them was a funny exercise and I was tripping the breaker several times a week as these radios were poorly isolated. My first soldering iron was an Engel-Loeter, a quick heating type, having a pistol shape. I still have it but could no longer use it to solder SMD types! I bought my single-trace oscilloscope at 15, it was a Hameg HM307 that is still working.

What are your favorite hardware tools that you use?

The are several instruments that I use. The first one is an isolated high-voltage dc supply from Xantrex, a XHR600-1.7. This is really a simple and efficient tool if you are in the offline power conversion business. To test my converters, I team this power source with an electronic load from Agilent, an HP6063B. Unlike other instruments that we have, you don’t need to open the manual every time you need them. I also run a LeCroy Waverunner oscilloscope but I confess that I sometimes miss CRT-based devices for their speed and ease of use : )

What are your favorite software tools that you use?

I extensively use simulation tools such as Intusoft ICAPS but also mathematical tools such as Mathcad. Mathcad may not be the best of the available solvers, but it is easy to use and well spread among the engineers world-wide. At ON Semiconductor, where I work in France, we write a lot of design sheets with this software.

What is the hardest/trickiest bug you have ever fixed?

I remember a converter that was failing in production at power off. Usually, converters fails in specific conditions like start-up sequence, short-circuit or input overvoltage. With this design, the power supply was quietly destroyed when the operator was unplugging it from the test fixture. I received several boards and indeed, I confirmed that unplugging the converter was killing the power supply. Funny enough, all was intact in the converter, only the controller was affected. At a certain moment, I destroyed the main power MOSFET and replaced it to continue the tests. I was surprised to see that the power destruction no longer happened further to that change. What could be the relationship between the controller destruction and the power MOSFET? It took me a while to observe that a strong negative bias was occurring on the high-voltage pin of the controller. How could a negative voltage appear on a highly positive rail? After several days of investigation, I found that the transformer primary inductance was resonating with the bulk capacitor at power off. Depending on the MOSFET RDS value, the quality factor was more or less important, affecting the ringing below ground. By replacing the 20-A power MOSFET by a 10-A type, I simply contributed to damp the whole circuit, reducing the negative swing at turn off. A simple high-voltage diode in series with the pin fixed the problem.

What is on your bookshelf?

I have several technical books that I like to refer to. I often use the Mathematical Handbook of Formulas and Tables from the Schaum’s outlines series. I have several power electronics books like Fundamentals of Power Electronics (Erickson and Maksimovic), Fast Analytical Techniques (Vorpérian) and of course, my last book Switch Mode Power Supplies: SPICE Simulations and Practical Design! Besides these technical books, I also have some dictionaries (French and English) as writing the right way also participates to engineering excellence, especially nowadays with a lot of epistolary exchanges.

What are you currently working on?

I am working on a new series of controllers combining high-efficiency in light load and extremely low no-load consumption.

What direction do you see your business heading in the next few years?

Digital power becomes a reality in high-end dc-dc converters but is not present yet in high-volumes adapters for the consumer market. A while back, good efficiency numbers were only required at nominal power and optimization at a single operating point was doable. With emerging standards asking efficiency numbers at different operating points, e.g. the 80+ standard, digital power has a sense to adjust parameters on-the-fly as the converter encounters different operating conditions. We can already see some controllers integrating digital compensators but I am not sure they are cost-competitive with current analog solutions. Looking at this trend, my fear is that power electronics engineers gets replaced by software engineers that have little or no knowledge of the analog field!

What challenges do you foresee in our industry?

Efficiency and power consumption reduction is on every engineer and consumer lips. With cost pressure pushed to the maximum on some high-volume projects, engineers are asked to provide solutions that cost less and offer better energetic performance than their predecessors. Going from a few watts of standby power to less than hundred milliwatts was a difficult step and it took a few years to make it a reality. The new step is to go from less than hundred milliwatts to less than ten milliwatts, the power converter remaining connected to the mains while unloaded. New all-electronics solutions have to reach what an open switch already does but at a less costly solution. This is a challenge for design engineers as other considerations such as safety recommendations come on top of the efficiency numbers.

Do you consider communicating an engineer’s activity?

I believe that an engineer must be skilled in the art of communicating. First because his job might be to promote the products/projects his works upon. An engineer must be able to really articulate what he implemented or invented so that his fellow workers, his management or his customers can capture the essence of the work or the invention itself. Failure to promote ideas by poor communication is a clear obstacle to career roll-out in the company or in the considered industry. Communication can be made in the form of written reports or live presentations. Both aspects require care in the wording and performance while talking in front of an audience. Despite excellent ideas, I have seen numerous people failing to convince others because the text or presentation were too mediocre.

The second reason is related to transmission knowledge. As an engineer, but it is true for any other function in our industry, I believe in the importance of teaching and transmitting the accumulated knowledge to the new comers in our engineering world. Setting up training sessions or writing reports so that others can learn from you is essential to the function I believe. Teaching in college in another step that I would encourage engineers to take. Writing on a technical subject forces you to formalize the knowledge you have in that particular subject, without simply eluding a difficult question as you would orally do. If at a certain moment, you don’t know what to write or say, digging up the subject further and finding the explanation yourself will help you master the topic and improve your knowledge in that domain. Also, having an audience such as students is an excellent exercise for future professional presentations you will give.

Having the web as a means to publish your ideas or articles is an extraordinary opportunity you cannot afford to miss. I remember publishing my first article at the age of 16 in a French hobbyist magazine. At that time, there was no word processors and Commodore or Sinclair were the only computers brands a student could afford. Illustrations or PCBs were drafted by hand, further revamped by a production team. Corrections were tedious and long! With nowadays tools and engineering websites, there are tons of opportunities that you can grasp.

Previous Next

Previous Spotlights

Featured Products

Click Here