What's Happening at APEC 2013

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Analysis of announcements to be made at the Applied Power Electronics Conference and Exposition, particularly new wide-bandgap switching technologies

APEC, the annual Applied Power Electronics Conference and Exposition, kicks off this Sunday, in Long Beach, California.  I’ll be there, along with Power Electronics’ Sam Davis, and Engineering TV producer Curtis Ellzey, to cover the conference for the Penton Design Engineering and Sourcing Group.  The Conference Schedule is here.

I’m expecting that, once again, GaN and SiC power device announcements will attract attention. In fact, there will be new announcements about SiC bipolar (as opposed to field-effect, devices.)

To clarify exactly what the SiC bipolar excitement is about, there will be announcements by GeneSiC and Fairchild. GeneSic has been present at APEC for at least two years, but hasn’t exhibited.  Fairchild’s entry into SiC comes from the acquisition of TRANSiC, a Swedish company.)

I asked Transphorm’s Carl Blake to spell out the differences for me.  Transphorm is a provider of GaN devices, but I’ve know Carl for a good deal longer than the new company has been in existence, and he’s always good, for a clear, concise explanation.

He first pointed out that SiC bipolars, the new kids on the block, being current-driven devices, have relatively high gate losses, but their low collector-emitter saturation voltage (Vce) yields lower IR drop and greater efficiency under high current (full load) conditions.  On the other hand, below approximately the 50% load point, their losses are higher than field effect devices.  Paralleling bipolars distributes the heat but does not reduce the losses.

On the other hand, FET devices are voltage driven, Gate losses are low, simply what is needed to charge a capacitance.  But their output losses being resistance-based, are proportional to the current through the device.  Thus, in contrast to the bipolars, their losses are lower at low power and increase at higher power levels. Their saving grace, compared to bipolars, though is that they can be paralleled to reduce the losses (by lowering the current per device). 

In practical terms, in power supplies, paralleled FET type devices are used to provide the highest efficiency.  In motor drives, bipolars (Historically IGBTs) have used to reduce full load losses.

(I actually knew that with respect to MOSFETs and IGBTs, from my time doing Harris Semi PR, but I’d failed to apply it to the bipolar SiC devices.)

Bipolar and FET SiC aside, there is still enough skepticism about GaN and Sic that Transphorm, among others, will kick things off at the Plenary with a talk by the company’s CEO and co-founder, Dr. Umesh Mishra, called Compound Semiconductors: GaN and SiC, Separating Fact from Fiction in Both Research and Business. (On the show floor, Transphorm will announce more 600V products, and will display the world’s first GaN-based high-power converter, a joint effort with Yaskawa Electric.)

There will also be a more informal rap session, Wide band-gap semiconductors - Prime time or promises?: Tuesday at 5:00 p.m. Announced panelists include Dr. Dan Kinzer, Fairchild’s CTO, and Efficient Power Conversion (EPC) founder Alex Lidow.

More conventionally, Disti Richardson RFPD will feature a selection of Silicon Carbide discrete devices and modules, including Schottky diodes and MOSFETS, as well as SiC and hybrid modules from Cree, Microsemi, Powerex and Vincotech

Meanwhile, power companies have been filling my email box with descriptions of the things they will be talking about or showing at APEC 2013.  Here’s a short list:

At its booth, Fairchild’s FAEs are preparing to discuss a number of topics beyond SiC, including lighting, dc-dc conversion, industrial power, and motion control.

With respect to motor control, Fairchild says that designers are moving away from the traditional universal, or ac motor design, to brushless dc and permanent magnet/permanent magnet synchronous motor or permanent magnet synchronous motor design. In support, the company has introduced a new analog/digital motor controller with user guides, reference designs, and evaluation boards.

Other promised booth features that caught my eye were: high-efficiency building blocks for smart meters, inverters and converters in energy harvesting and industrial designs, new automotive devices for higher current and power density, reducing power dissipation and enabling smaller package footprints, and new PoE products that reduce conduction losses and increase the efficiency of the conventional diode bridge, providing 10X improvement in power dissipation.

Fairchild FAEs will also present on applied energy saving solutions with MOSFETs, LED controllers, IGBTs, Power Factor Correction and other topics. 

Earlier this Spring, International Rectifier announced new features for its IGBT selection tool. Now, the tool evaluates application bus voltage, load current, switching frequency, short-circuit requirements, package and thermal system and produces customizable thermal constraint settings and current/frequency output charts that make it easy to compare devices. It then returns a shortlist of products that meet or exceed the user’s application requirements, ranking them by performance and listing losses and junction temperatures.

Also earlier in the month, IXYS announced new 650-V trench IGBTs with current ratings from 30 to 200 A at 110° C, with on-stage voltages down to 1.7 V and switching speeds up to 60 kHz. They can be co-packed with IXYS ultra-fast Sonic-FRDTM diodes.

Texas Instruments will show off new 650, 300, and 100-mA, 48-V combined “Fly-Buck” converters with a constant on-time (COT) control architecture that reduces board space by up to 40 % compared with traditional designs that require multiple dc-dc converters. Each can be configured to provide positive and negative voltage rails, or isolated multiple outputs with excellent cross-regulation.

Update (3/12.13)  TI also says it will show a 15-A “smart” bypass diode.  (Demo Video).  The “smart” designation requires a little explanation.

The issue it addresses is dealing with cells in series strings in photovoltaic panels that exhibit a high resistance when they’re in the shade. Voltage drops across the shaded cells reduce the output voltage of the string.

The usual solution is to parallel each cell with a Schottky.  The TI “smart” diode parallels each diode with a MOSFET, which is powered by a charge pump driven by the actual diode in the package.  When the diode starts carrying the current from the rest of the cells in the PV string, the MOSFET is turned on.  (The TI video link above clarifies that two-sentence summary.)

Linear Technology introduced new chips for electric-vehicle battery management that I wrote about in considerable detail in the March issue of Electronic Design.

Vicor will show a new, VI-chip based, conduction-cooled version of its high-efficiency Westcor MicroPAC power-factor corrected ac-dc power system, which can do without fan and forced-air cooling. With it, designers can create distributed power systems up to 1300-W, continuous, at up to 92% efficiency and 25 W/in3 power density in a 4 x 1.72 x 7.45 inch footprint.

And Green Plug says it will announce a GUI-based development platform for rapid prototyping and tuning for its high-performance, mixed-signal programmable controllers.  Essentially, they have a common controller that can be adapted easily to different topologies, power ranges and designs, using the platform. The company says that now, power supply designers will be able to collaborate with their power- driver chip suppliers to optimize integrated power devices for their applications.

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Don Tuite covers Analog and Power issues for Electronic Design’s magazine and website. He has a BSEE and an M.S in Technical Communication, and has worked for companies in aerospace,...
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