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On-Chip Drivers Enable High-Current, Normally Off GaN Transistors (Part 1)

by John Roberts and Iain Scott, GaN Systems, Ottawa, Ontario, Canada , How2Power Today, May 15 2014

Focus:
Gallium nitride (GaN) offers speed and density benefits for switching power systems. But driving GaN transistors, especially above 100 A, has proved difficult to achieve reliably as the low-voltage threshold of enhancement-mode GaN power switches leads to unwanted turn-on. GaN Systems is addressing this problem by implementing the gate-drive circuitry on-chip, enabling development of higher-current normally off GaN transistors that are reliable and simple to drive. In this article, the advantages of GaN transistors and their gate-drive requirements are reviewed, leading to a discussion of the on-chip gate driver concept. The structure and operation of a 200-A, 650-V enhancement-mode GaN HEMT power device with on-chip drivers is then explained and its performance is demonstrated with simulated data for the device’s transfer and C-V characteristics and switching losses. For comparison, C-V characteristics and switching losses are also shown for a comparable IGBT and a comparable superjunction MOSFET.

What you’ll learn:

Notes:
A closely related article by John Roberts, “Driving high-power GaN transistors,” appeared in Power Systems Design (4/29/2014), which is available at http://www.powersystemsdesign.com/driving-high-power-gan-transistors . This article discusses thermal issues that arise in driving these large GaN transistors, provides some additional details on device structure, and mentions specific Microchip models used as external pre-drivers for the GaN transistors.

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