A 6.7-GHz Active Gate Driver for GaN FETs to Combat Overshoot, Ringing, and EMI

Abstract

Active gate driving has been demonstrated to beneficially shape switching waveforms in Si-and SiC-based power converters. For faster GaN power devices with sub-10-ns switching transients, however, reported variable gate driving has so far been limited to altering a single drive parameter once per switching event, either during or outside of the transient. This paper demonstrates a gate driver with a timing resolution and range of output resistance levels that surpass those of existing gate drivers or arbitrary waveform generators. It is shown to permit active gate driving with a bandwidth that is high enough to shape a GaN switching during the transient. The programmable gate driver has integrated high-speed memory, control logic, and multiple parallel output stages. During switching transients, the gate driver can activate a near-arbitrary sequence of pull-up or pull-down output resistances between 0.12 and 64 Ω. A hybrid of clocked and asynchronous control logic with 150-ps delay elements achieves an effective resistance update rate of 6.7 GHz during switching events. This active gate driver is evaluated in a 1-MHz bridge-leg converter using EPC2015 GaN FETs. The results show that aggressive manipulation of the gate-drive resistance at sub-nanosecond resolutions can profile gate waveforms of the GaN FET, thereby beneficially shaping the switch-node voltage waveform in the power circuit. Examples of open-loop active gate driving are demonstrated that maintain the low switching loss of constant-strength gate driving, while reducing overshoot, oscillation, and EMI-generating highfrequency spectral content.

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

“…A hybrid of clocked and asynchronous control logic with 150-ps delay elements achieves an effective resistance update rate of 6.7 GHz during switching events. Details of the driver architecture are provided in [13]. The output of the driver can be set to a constant gate strength to compare with the results of active gate driving, although the effective gate resistance is then voltage dependent [13].…”

“…The control device is actively controlled to create less crosstalk on both transients, whilst the synchronous device's gate impedance is adjusted to make it more immune to interference. This is done by driving each GaN FET with a 6.7-GHz integrated active gate driver [13], which has been previously demonstrated to allow the shaping of the switching waveforms of 40-V [13]- [14] and 650-V GaN FETs [15] in a bridge-leg converter for overshoot, oscillation and EMI reduction. The driver can be programmed to vary its output resistance from 0.12 Ω to 64 Ω every 150 ps.…”

A DSOGI-FLL-Based Dead-Time Elimination PWM for Three-Phase Power Converters

“…The dead-time effect is especially serious in the low-speed motor drive system [2] and the high-switching frequency converter [3], [4], where large numbers of dead-time voltage errors are included in a fundamental period. Specifically, with nowadays developed wide-bandgap devices, the switching frequency of converters can reach up to 100kHz (with silicon carbide devices [4]), or even several MHz (with gallium nitride devices [5]). The dead-time effect will be further intensified with the ultra-high switching frequency and must be well addressed.…”

Design of an Advanced Programmable Current-Source Gate Driver for Dynamic Control of SiC Device

“…Nowadays, various types of active gate drivers have been investigated to improve the performance of SiC power devices. According to the control strategy, active gate drivers are usually classified into three categories: resistance controlled gate driver [12] [13], voltage controlled gate driver [14] and current controlled gate driver [15]. For the group resistance controlled gate driver the circuit commonly uses a digital interface which is easy for isolation implementation, however, the gate voltage level is fixed and a discrete resistance network has to be employed with a very large number of integrated resistors.…”

“…High bandwidth linear isolation techniques are required to drive SiC devices at high frequency for an acceptable resolution. Gate current control techniques directly control the gate current, which shows the flexibility to adjust gate driving signals with a reduced gate oscillation, however, the existing reported current-source active gate drivers are either designed with limited functions or too complicated for implementation [12][13].…”