A 6.7-GHz active gate driver for GaN FETs to combat overshoot, ringing, and EMI

Dymond, Harry C.P. and Wang, Jianjing and Liu, Dawei and Dalton, Jeremy J.O. and McNeill, Neville and Pamunuwa, Dinesh and Hollis, Simon J. and Stark, Bernard H. (2018) A 6.7-GHz active gate driver for GaN FETs to combat overshoot, ringing, and EMI. IEEE Transactions on Power Electronics, 33 (1). pp. 581-594. ISSN 0885-8993

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    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 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 high-frequency spectral content.