It’s been at cool but sunny day here at APEC 2013 in Long Beach with good weather. I wish I could get outside more to enjoy it. But duty calls.
There was a bit of heat in the Extreme Devices session this morning during which Y. Wu from Transphorm Inc. defended himself during the Q&A when asked why he presented a power stage that had four parallel GaN FETs. The person asking the question was basically implying that Y. Wu should have done an interleaved system instead of four parallel GaN FETs. Y. Wu could simply have responded that there are not always multiphase controllers available for every application space or, simply, that this is the topic of the paper and then move on. It’s probably best to simply take the paper as a bunch of good hints on layout techniques.
Tuesday morning’s best paper on ZCS fundamentals was from Dan Constinett from the University of Colorado Boulder. It was excellent because many people think it is easy to pick up the efficiency of ZVS (Zero Voltage Switching). But you have to worry about balancing the magnetics, so the currents do not run away and stress devices. Or, they could run with worse efficiency than simpler methods.
Or the devices blow up on you.
I am a bit surprise that there is a new 3/5 material vendor in the fray. Sarda Technologies of North Carolina announced a <20V GaAs (not GaN), low voltage, power FET with a good FOM (Figure of Merit) of 11. That FOM is defined as RDSON in mOhms x total gate charge in nC. Their devices are a bit hard to drive because the gate leakage is 1 mA to 5 mA. But since their 14 mOhms device has a gate charge of 0.76 nC, it can run at 2 MHz. I am sure they will run faster but as there are few high current magnetics, this problem is still limiting to everyone in the GaN/GaAs market.
See you back here tomorrow with whatever interesting tidbits I find in any of the following scheduled Rap Sessions:
- Sustainable Energy versus Sustainable Business: Is there a viable business case of power electronics in Solar?
- Wide band-gap semiconductors - Prime time or promises"
- Status of the Various Electric Vehicles