Semiconductors In The Efficiency Era Sponsored by Cree and Efficient Power Conversion
●Although, for the last few years, there has been a lot of talk about gallium nitride (GaN) based power transistors displacing the entrenched silicon MOSFETs, it might take sometime before the emerging gallium nitride on silicon (GaN-on-Si) based power FETs enter the mainstream power conversion space. However, in the meantime, a handful of emerging applications are poised to tap the benefits of this promising power technology. Besides commercial availability with high reliability, there are a number of unique GaN characteristics that are fostering these new applications.
●Some of these emerging applications exploiting the attributes of GaN technology include wireless power transmission, RF envelope tracking, rad hard satellite and avionics power supplies, and light detection and ranging (LIDAR) among others. In addition, high-stepdown-ratio buck converters that must be operated in the megahertz range without compromising efficiency are also taking advantage of the technology.
●Wireless power transmission and RF envelope tracking systems, for instance, are utilizing a distinctive blend of high-frequency operation with high-power and high-voltage capabilities. While power systems for satellite and avionics applications are making the most of GaN transistors' rad hard qualities, precision current sources are using GaN devices to generate high-current millisecond pulses to drive pulsed laser diodes. And, for mobile applications that require ultra-high power density and efficiency simultaneously, traditional dc-dc converters are incorporating GaN FETs operating at several megahertz in resonant mode.
●While the concept has been around, the rapid adoption of wireless energy transfer in commodity products such as mobile phone chargers is relatively new. In such wireless charging applications, highly resonant converters operating in the lower ISM band at 6.78 MHz are used to power the magnetic coils on the transmitting side. The 6.78 MHz for wireless charging systems was recently standardized by the Consumer Electronics Association and Alliance for Wireless Power (A4WP). At such high frequencies, traditional MOSFET technology is approaching its limits. But, this high-frequency operation is ideal for enhancement-mode GaN (eGaN) FETs, according to Efficient Power Conversion (EPC) CEO Alex Lidow, the co-inventor of the HEXFET power MOSFET.
●In fact, using WiTricity's magnetic coils, EPC has demonstrated an experimental high-efficiency resonant wireless power transfer system using eGaN FETs. The power converter implemented in this system is a class-D power amplifier operating at 6.78 MHz (Fig.1). It is believed that next year wireless charging systems utilizing eGaN-powered WiTricity technology will begin to enter the market.
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Technical Documentation |
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Please see the document for details |
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English Chinese Chinese and English Japanese |
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December 2012 |
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