The book “GaN power devices and applications” is a guide for designers dealing with GaN devices written by Alex Lidow, founder and CEO of EPC. This company manufactures GaN power transistors. The book was written with input from about 30 experts in power conversion applications.
Silicon power MOSFETs have not kept pace with evolutionary changes in the power electronics industry. Factors such as efficiency, power density, and reduced form factors are the main demands of the industrial community. The power electronics industry has seen the theoretical limit of silicon MOSFETs reached and now we must be able to look to new technology. Gallium nitride (GaN) is a wide bandgap semiconductor capable of meeting new emerging applications.
The book is a value-add to the industry and to all designers and effectively addresses all the major aspects of GaN, focusing on the application aspect. After an initial introduction on its importance, electrical characteristics, and state-of-the-art application market, the book focuses on reliability and the factors that make it such an essential component for the future of power electronics.
The performance of power systems has increased thanks to GaN transistors, which, at the same time, allow for lower design costs. With GaN, failures occur in different ways and mechanisms. But how to evaluate its quality and reliability? This is a key question for every industry, and in the book Lidow and his collaborators describe it by analyzing all possible stress tests and models to explain the physics of failures within the GaN transistor. The GaN industry aims to demonstrate that GaN solutions have at least the same life expectancy as silicon MOSFETs and, ideally, a more efficient life.
Reliability of GaN transistors includes:
- In-depth failure mode analysis
- Rigorous design
- A series of qualification and lifetime tests
All this effort enables the industry to offer robust and reliable solutions for automotive, industrial, and aerospace applications.
The author next focuses on the main applications of GaNs, such as DC-DC conversion, lidar, motor control, and space solutions. Multilevel converters are common, and the related challenges of the physical construction of power supplies are examined. GaN power transistors are an ideal choice in support of extreme space missions. The technology provides excellent radiation-dependent performance and SEE (single-event effects) immunity.
In motor control, silicon devices are approaching their theoretical limits and there is an increasing need for higher power density. The fast-switching capability of GaN and the absence of “reverse recovery” currents help to remove the relative dead time and increase the PWM frequency to provide quieter motor behavior but most importantly with higher efficiency. The book considers the two-level inverter and basic concepts about motors. In particular, the limitations of silicon and how GaN can offer design advantages are highlighted.
LiDAR is a technique that is the basis for autonomous driving and allows the distance between objects to be measured, using pulsed lasers, and through the information acquired, a 3D image of the surrounding space can be obtained. LiDAR technology offers high accuracy, wide-range coverage, and comprehensive digital support for data collection. GaN solutions prove suitable as a driver element for laser switching, driving high current and extremely short pulses. Short pulse widths provide higher resolution, and a high current pulse enables LiDAR systems to reach significant distances. When not pulsed, the GaN device in the OFF state is exposed to some drain bias. This condition is particularly significant and important and requires careful analysis. Lidow discusses this very interesting reliability point in Section 3.7.
The list of development solutions at the end of the book makes it comprehensive. In addition to the theory and design aspects, the author provides practical solutions to start having fun with GaN right away.