GaN Talk Blog

This post was originally published by Dr. John Glaser & Dr. David Reusch on June 13, 2016 on the Power Systems Design web site.

Comparing Dead-time Losses for eGaN FETs and Silicon MOSFETs in Synchronous Rectifiers

There have been several comparisons of eGaN FETs with silicon MOSFETs in a variety of applications, including hard-switched, soft-switched, and high-frequency power conversion. These studies have shown that eGaN FETs have large efficiency and power density advantages over silicon MOSFETs. Here we’ll focus on the use of eGaN FETs in synchronous rectifier (SR) applications and the importance of dead-time management. We show that eGaN FETs can dramatically reduce loss due to dead-time in synchronous rectifiers above and beyond the benefits of low R_DS(on)and charge.

Silicon has been around long enough. It’s time for a younger and far more fit challenger to take over semiconductor material dominance.

When I first started developing power devices 44 years ago, the “king of the hill” was the silicon power bipolar transistor.  In 1978 International Rectifier (IRF) launched power MOSFETs as a faster alternative to the slower and aging bipolar devices.  The early adopters of the power MOSFET were applications where the bipolar just was not fast enough.  The signature example for its adoption was the switching power supply for the desktop computer; first at Apple, and then at IBM. 

Gallium nitride (GaN) power transistors designed for efficient power conversion have been in production for seven years. New markets, such as light detection and ranging, envelope tracking, and wireless charging, have emerged due to the superior switching speed of GaN. These markets have enabled GaN products to achieve significant volumes, low production costs, and an enviable reliability reputation. All of this provides adequate incentive for the more conservative design engineers in applications such as dc–dc converters, ac–dc converters, and automotive to start their evaluation process. So what are the remaining barriers to the conversion of the US$12 billion silicon power metal–oxide–semiconductor field-effect transistor (MOSFET) market? In a word: confidence. Design engineers, manufacturing engineers, purchasing managers, and senior management all need to be confident that GaN will provide benefits that more than offset the risk of adopting a new technology. Let’s look at three key risk factors: supply chain risk, cost risk, and reliability risk.