Date of Graduation

8-2024

Document Type

Thesis

Degree Name

Master of Science in Electrical Engineering (MSEE)

Degree Level

Graduate

Department

Electrical Engineering

Advisor/Mentor

Song, Xiaoqing

Committee Member

McCann, Roy

Second Committee Member

Saunders, Robert

Keywords

Bidirectional switch; Double pulse test; Gallium Nitride Power Switch

Abstract

Gallium Nitride (GaN) has emerged as one of the leading materials for power devices due to its wide band gap and high electron mobility. The band gap is the minimum energy required to excite an electron up to a state in the conduction band where it can participate in conduction. Because of this, wide band gap (WBG) materials are favorable for various electrical applications. The market for GaN high-electron-mobility transistor (HEMT) is projected to exceed $1.25 billion by 2027. With the increase of market interest, modern technologies emerge that aim to push the boundaries of efficiency for GaN power devices. The use of field effect transistors is common for power switches, and GaN based power switches increase their efficiency and minimize losses compared to silicon-based power switches. In this work, we aim to evaluate the switching effectiveness of two emerging power switches to determine the optimal test conditions and components for peak performance. The first device is the GaN field effect transistor (FET) 650V power switch. A widely accepted testing method, double pulse testing, was used to evaluate the device. A printed circuit board (PCB) was designed with careful consideration, taking into account circuit and device parasitics, parasitic inductance due to magnetism, and component placement priority. Using the test circuit and recommendations from the manufacturer datasheets, results were collected on the on-resistance RON, switching speeds and energy losses for the GaN FET. The results concluded the optimal Ron for the circuit was 70Ω, with a 220Ω ferrite bead @ 100MHz, and -5V turn off voltage VGS. The largest energy loss recorded was 167μJ for turn-off operation at 300V and 50A. The fastest switching speed recorded was 69kV/μs, and the largest voltage overshoot recorded was 31%. While the tests results were favorable, continued work is required to evaluate the device at its maximum rated voltage and current ratings. The low-loss GaN four-quadrant switch (FQS) is another power switching device examined in the current work. The four-quadrant switch is a bidirectional switch capable of blocking and conducting current in both directions irrespective of voltage polarity. The device also may block voltage in either polarity. The low-loss GaN FQS operation was verified using an inductive load and a resistive load. The results verified the operation of the bidirectional switch with current flow, and voltage blocking confirmed. The design for the Low-loss GaN FQS for solid state circuit breaker application is also discussed in this work. Preliminary results indicate the operation of the Low-loss GaN FQS is viable for current and voltage blocking, however the inductive load test recorded an unintended voltage gate signal operation. Possible causes are gate parasitic inductances or being RON not being large enough to block unwanted signals. Further work is to be done to verify the operation of the Low-loss GaN FQS for practical applications.

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