A Universal Block of Series-Connected SiC MOSFETs Using Current-Source Gate Driver

IEEE Open J. Power Electron.

et al. 2021

Self Cite

The voltage rating of commercial Gallium Nitride (GaN) power semiconductors is limited to 600/650 V because of the lateral structure. Stacking low-voltage switches is an effective way to block higher dc-link voltage. However, unbalanced voltage sharing can occur even with well-matched gate drivers and semiconductors due to the device-to-ground displacement currents. As a result, the low-voltage switches may suffer from over-voltage breakdown. This study presents a novel closed-loop current source gate driver to address the unbalanced dynamic voltage sharing issue. Additional compensation current is actively injected into the switch gate to counteract the voltage imbalance brought by the device-to-ground displacement currents. Compared with the conventional voltage source gate driver-based active gate control method, the proposed current source gate driver tunes the switch turn-off timing and dv/dt more accurately because the switch gate current is directly regulated. Meanwhile, since both the pulse width and amplitude of the compensation gate current can be adjusted, the proposed active gate control is more flexible for adapting to different operating conditions. Moreover, without employing snubber circuits or extra Miller capacitors, the switching speed and switching energy of the GaN devices are not compromised. By implementing the proposed gate driver and voltage balancing schemes, well-balanced voltage sharing can be obtained for both soft-switching and hardswitching scenarios. A series-connected GaN-based multiple pulse tester (MPT) is built to prove the effectiveness of the proposed approach under different load and different switching speed (dv/dt) conditions.

Section: A Hardware Architecturementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

A Closed-Loop Current Source Gate Driver With Active Gate Current Control for Dynamic Voltage Balancing in Series-Connected GaN HEMTs

Zhang

IEEE Open J. Power Electron.

et al. 2021

Self Cite

“…A prototype of the series connection of eight 1.7 kV SiC MOSFETs is given in [28]. The current source gate driver for the series connection of SiC MOSFETs is reported in [29]. The series connection of the SiC MOSFETs with capacitor snubber under soft-switching conditions has been reported in [30,31], where the device turns off at a relatively low current at 5 kV/400 V DC LLC converter.…”

Section: Introductionmentioning

confidence: 99%

A highly efficient power block with series connection of power SiC MOSFETs‐design, characterization and assessment in MV converters

Zhu

et al. 2022

IET Power Electronics

Implementation of the series connection of the SiC MOSFETs in medium voltage (MV) high power converters faces a series of challenges, including the electrical/thermal stress imbalance, insulation coordination design, high dv/dt elimination and robustness under variable operating conditions. This paper stresses these challenges and proposes a comprehensive design of a 9.6 kV/200 A power block based on the series connection of SiC MOSFETs. The power block has been verified under the continuous operation, which demonstrates the highly efficient and reliable operation under the variable switching current condition. Afterward, performance screening in a 5 kV/1 MW inverter is conducted to assess the efficiency in MV converters. Compared with the advanced high voltage high power devices, the proposed power block demonstrates fast switching speed and low switching loss, which indicates that the series connection of SiC MOSFETs is a promising technique to expand the operation voltage/power of the SiC MOSFETs to the MV megawatt level. The proposed design can be expanded to other specifications as well.

“…Series connection of single devices is an effective way to achieve higher blocking voltage [9], [10]. One of the major challenges of series-connected devices is the unequal drainsource voltage (V ds ) balancing [11], [12].…”

Section: Introductionmentioning

confidence: 99%

A Comprehensive Short-Circuit Protection Scheme for Series-Connected SiC MOSFETs

Zhang

IEEE Open J. Power Electron.

et al. 2022

Self Cite

Series connection of devices is an effective way to achieve higher blocking voltage. SiC MOSFETs exhibit narrow short-circuit withstand time and generally much lower short-circuit robustness than silicon IGBTs. This puts a critical concern on their utilization, further stressing the importance of reliable protection. A complete short-circuit protection should be implemented to improve the reliability. In this article, a systematic short-circuit analysis methodology is proposed. Following this methodology, all the possible fault scenarios can be derived. Besides the traditional short-circuit scenarios, some unique short-circuit faults, such as a single device short-or open-circuit, have been found in series-connected SiC MOSFETs. These unique faults may not cause overcurrent, which means the traditional overcurrent-based protection is not applicable. This article proposes a method combining drain-source voltage logic signal and gate signal to comprehensively detect both classic short-circuit scenarios and unique fault scenarios. Another different point in series-connected devices is that the soft turn-off should be synchronized for each serial device to prevent excessive voltage unbalancing. The proposed short-circuit protection scheme is evaluated under each short-circuit scenario. The experimental results demonstrate that the proposed protection scheme can successfully protect the serial devices from further destruction within 500 ns for all short-circuit scenarios.