Friday, March 21, 2014

Applied Power Electronics Conference and Exposition (APEC) 2014

One way to learn is to hang out with very smart people and try to keep up.

I recently attended the IEEE APEC in Fort Worth, TX. Since I live close to the convention center, I could attend without having to pay for a hotel or airline flight. Since I am currently between contracts, I had the week free to go. I haven't attended this conference before, but it seemed like a great opportunity. I don't attend many conferences. In fact, the last major conference I attended was ISSCC in 2002. These two conferences were very different. 

Some random comments.

  • They tell you the rooms are often cool so you should bring a sweater or jacket. Boy, are they right. Don't bring a pull-over (the mistake I made Monday) because there will be rooms where you don't want to where it. 
  • They feed you! Lunch was available for purchase on-site Sunday and Monday. Lunch was available for free during the industry exposition and during the poster session. This was cheaper, of course, but it was also incredibly convenient. 
  • There were lots of tracks, sometimes as many as twelve. It was sometimes hard to choose which session to attend. 
  • They kept the speakers on the time schedule. Period. That sometimes meant cutting questions short, occasionally meant cutting a speaker short, and once it meant waiting a few minutes before letting the next speaker begin. Keeping to the strict schedule allowed participants to skip between sessions to catch paper presentations in several tracks. 
  • The conference was very well organized. Presentations were pre-loaded before the sessions. Professional AV people were in every room to adjust the audio and solve problems as they occurred.
  • I was handed a USB stick containing all papers at registration. Fantastic.  
  • It was a very international conference. No real surprise there. 

Compared to the ISSCC 2002, I surprised myself by preferring this conference. 

  • The questions were requests for clarifications not attacks on the paper presented. 
  • Speakers were kept strictly to their times. 
  • APEC was more appropriate for the working engineer
    • There were many industry presented papers.
    • Companies were allowed to make product presentation. They were clearly labeled as such and were often interesting. 
    • There was a large (more than 1,000 booths) industry exposition. 
    • I actually heard the question asked after a paper was presented, "What do you see as the application of this circuit?" This particular paper had some odd input and output goals but the presenter did, in fact, have a real-world application in mind. 

Comments based on presentations

Packaging is a big deal for high speed, high power, and high temperature. SiC and GaN transistors intended for large power supplies are all three. Packaging was discussed a lot. 

It sounds like SiC is really coming into its own. My master's thesis way back in 1993 concentrated on characterizing a particular SiC type (6-H p-type substrate) so I glad that 20 years later that industry is getting some traction. 

Intersil discussed an interesting all digital control loop that eliminated the need for compensation. I haven't managed to get my hands the white paper where it is described in more detail. 

V2 control of DC-DC converter loops was mentioned several times. I need to figure out how that works. Maybe I can make it a future topic for this blog. It looks like it has faster transient response but adds more complexity. 

I am excited by the paper "Capacitor-Less Photovoltaic (PV) Cell-Level Power Balancing Using Diffusion Charge Redistribution". It describes a simple way to keep partial shading on a single cell from significantly lowering the yield from the entire string. I think I could make the controller for less than one dollar per cell. I liked the convergence between solar cells and switch capacitor converter. Some smart work. 

I finally really understand Power Factor Correction (PFC). I knew the circuits, of course, but the point of the exercise was lost on me. Dhaval Dalal made the simple statement, "PFC is meant to control input current not regulate output voltage." That was probably obvious to everyone but me. Now I get it too. 

The linear regulator isn't dead yet. There were no papers presented on them but I recall three times when it was mentioned that a linear regulator wouldn't be much less efficient then a presented buck regulator when the output voltage was close to the output voltage. The Power Supply on Chip guys seem to be holding linear regulators as a real competitor in size and power density. 

I will spare you all of my notes from the 55 sessions I attended. 

The APEC 2014 was very much worth attending. I don't know that I'll make it North Carolina next year. Cost and time may become too much of a problem. 

Bruce McLaren

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