A fully integrated three-level 11.6nC gate driver supporting GaN gate injection transistors.

authored by

Achim Seidel, Bernhard Wicht

Abstract

Due to their superior fast-switching performance, GaN transistors show enormous potential to enable compact power electronics in applications like renewable energy, electrical cars and home appliances by shrinking down the size of passives. However, fast switching poses challenges for the gate driver. Since GaN transistors have a low threshold voltage V

_t of ∼1V, an unintended driver turn-on can occur in case of a unipolar gate control as shown for a typical half-bridge in Fig. 24.2.1 (top left). This is due to coupling via the gate-drain capacitance (Miller coupling), when the low-side driver turns on, causing a peak current into the gate. This is usually tackled by applying a negative gate voltage to enhance the safety margin towards Vt, resulting in a bipolar gate-driving scheme. In many power-electronics applications GaN transistors operate in reverse conduction, carrying the inductor current during the dead time t, when the high-side and low-side switch are off (as illustrated at a high-side switch in Fig. 24.2.1, bottom left). As there is no real body diode as in silicon devices, the GaN transistor turns on in reverse operation with a voltage drop V

_F across the drain-source terminals (quasi-body diode behavior). As a negative gate voltage adds to V

_F, 63% higher reverse-conduction losses were measured for a typical GaN switch in bipolar gate-drive operation. This drawback is addressed by a three-level gate voltage (positive, 0V, negative), which at the same time provides robustness against unintended turn-on similar to the bipolar gate driver, proven in [1] for a discrete driver.

Organisation(s)

Mixed-Signal Circuits Section

Type

Paper

Pages

384-386

No. of pages

3

Publication date

2018

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Electronic, Optical and Magnetic Materials, Electrical and Electronic Engineering

Sustainable Development Goals

SDG 7 - Affordable and Clean Energy

Electronic version(s)

https://doi.org/10.1109/isscc.2018.8310345 (Access: Closed)