Crosstalk suppression in a 650-V GaN FET bridgeleg converter using 6.7-GHz active gate driver

Abstract

With switching transients as fast as 100 V/ns and a low threshold voltage of 1-2 V, GaN FETs in bridge-leg topologies are potentially vulnerable to crosstalk and the resultant unwanted partial turn-on, noise interference, and increased losses. Constantstrength gate drivers for GaN FETs limit switching speed to suppress crosstalk. In this work, active gate driving is shown to permit faster switching, whilst still suppressing crosstalk. This is demonstrated in a GaN FET bridge-leg converter. The control device transients are shaped to reduce crosstalk, whilst the synchronous device's gate impedance is actively varied to increase its immunity to crosstalk. This is carried out using two 6.7-GHz active gate drivers that can dynamically vary their output resistance from 0.12 Ω to 64 Ω every 150 ps during the sub-10-ns switching transients. It is demonstrated that unwanted turn-on is suppressed without incurring undershoot and oscillation in the gate, that negative spurious gate voltages can be greatly reduced, and that oscillations in the transient drain current are damped, without incurring additional loss.

A New Design Technique for Sub-Nanosecond Delay and 200 V/ns Power Supply Slew-Tolerant Floating Voltage Level Shifters for GaN SMPS

“…12 remaining almost constant, whereas V D D H increases linearly. The physical measurement of slew rate immunities will require the proposed (0.018 mm 2 ) level shifter to be embedded in a high-speed, dual-channel gate driver (around 10 mm 2 [9]). Here we have determined the slew rate immunity (Section III) using post-layout simulation.…”

“…The intended application of this level shifter is to drive a fast, floating gate driver [9] with 1.8 V input logic, and therefore this negative V S S H is problematic. The Type I level shifter addresses this problem.…”

“…An example of this scenario is a dual-output driver whose low-side clock needs to be level-shifted to the high floating side. This is the case, for example, in digital active gate driving, where the driving impedance is modulated digitally during the slewing period to reduce current overshoot [8] or suppress crosstalk [9]. In this second scenario, the proposed method results in a level shifter that achieves 200 V/ns and -60 V/ns slew-rate immunity.…”

Stretching in Time of GaN Active Gate Driving Profiles to Adapt to Changing Load Current

“…Drivers capable of three or more steps have also been shown to be capable at further reducing EMI and targeting overshoot in switching waveforms [3], [4]. A profiling flexibility with even greater time resolution during the switching transition has been shown to enable the reduction of crosstalk and oscillations [5], in addition to overshoot and EMI [5]- [8]. However, reported drivers with this very high time resolution, are currently open-loop with pre-programmed gate driving profiles.…”

“…it is acting as a conventional driver). Details of the specific driver architecture, support and programming hardware are provided in [5]- [7].…”