United States

Abstract— In this work, the humidity performance of three enhancement mode GaN HEMTs with different chip designs and packages from different manufacturers were investigated by a High Humidity, High Temperature, Reverse Bias (H³TRB) test. The devices were tested until end of life (EoL) with a few devices even surviving the end of the test after passing 6000 test hours. Some of the devices provided a precursor of the catastrophic failure, while others just failed suddenly. There were little changes in the characteristics obtained at intermediate measurements. The Weibull analysis of the failures shows a consistent and clear wear-out behaviour. These results document an excellent humidity capability of the tested GaN devices even outperforming usual silicon devices, although GaN devices exhibit smaller insulation distances and higher electric fields. However, during the initial phase of the test conductive anodic filaments (CAF) formed in the PCB adapters and compromised the leakage current readings such that the adapters had to be removed to be able to continue the test. In other words, the weakest spot is no longer the semiconductor device itself, but has moved to other components in the circuitry.

IEEE WiPDA 2021

Humidity Capability of Enhancement Mode GaN High Electron Mobility Transistors

The IEEE Workshop on Wide Bandgap Power Devices & Applications (WiPDA) provides a forum for device scientists, circuit designers, & application engineers from the Power Electronics & Electron Devices Societies to share technology updates, research findings, experience & potential applications.

**Topics of interest**

* Heteroepitaxial & Bulk Materials Growth
* Gate Dielectrics & Surface Passivation
* Device Structures & Fabrication Techniques
* Device Characterization & Modeling
* Very-High Efficiency or Compact Converters
* Safe Operating Areas of Wide Bandgap Devices, Including Short Circuit, Spike, & Transient Tolerance
* Harsh Environment (High Temperature) Operation & Reliability
* Packaging Power Modules & ICs
* Hard-Switched & Soft-Switched Application Analysis
* Gate Drive & Other Auxiliary Circuits
* High-Performance Passive Components
* Applications in Renewable Energy & Energy Storage, Transportation, Industrial Drives, & Grid Power Systems
* Wide Band Gap System Design Philosophies & Strategies
* Radio Frequency (RF) GaN (New)
* Technology Roadmap of Wide Bandgap Including Devices, Applications and Packaging (New)

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The IEEE Workshop on Wide Bandgap Power Devices & Applications (WiPDA) provides a forum for device scientists, circuit designers, & application engineers from the Power Electronics & Electron Devices Societies to share technology updates, research findings, experience & potential applications.

poster

The fast switching transients of wide-bandgap power semiconductor devices lead to reduced switching losses and thereby enable higher switching frequencies and power densities. However, these fast switching transients increase the stress on
insulation materials and can cause accelerated aging of the insulation system, leading to premature failure. To fully exploit the advantages of wide-bandgap power semiconductor devices, it is crucial to investigate the effects of steep voltage slopes on insulation materials. For this purpose, a dv/dt generator that enables insulation testing with adjustable fast switching transients and generates symmetrical voltage slopes of up to 166 V/ns is introduced in this presentation. Its fast short-circuit protection ensures safe operation even for destructive insulation tests.

SiC-Based dv/dt Generator for Insulation Testing with Fast and Adjustable Switching Transients

As motor drive inverters continue to employ Silicon Carbide (SiC) and Gallium Nitride (GaN) devices for power density improvements, sensorless motor control strategies can be developed with field-programmable gate arrays (FPGA) to take advantage of high inverter switching frequencies. Through the FPGA’s parallel processing capabilities, a high control bandwidth sensorless control algorithm can be employed. Sensorless motor control offers cost reductions through the elimination of mechanical position sensors or more reliable electric drive systems by providing additional position and speed information of the electric motor. Back electromotive force (EMF) estimation or model-based methods used for motor control provide precise sensorless control at high speeds; however, they are unreliable at low speeds. High frequency injection (HFI) sensorless control demonstrates an improvement at low speeds through magnetic saliency tracking. In this work, a sinusoidal and square-wave high frequency injection sensorless control method is utilized to examine the impact an interior permanent magnet synchronous machine’s (IPMSM) fundamental frequency, injection frequency, and switching frequency have on the audible noise spectrum and electrical angle estimation. The audible noise and electrical angle estimation are evaluated at different injection voltages, injection frequencies, switching frequencies, and rotor speeds.

High Frequency Injection Sensorless Control for a Permanent Magnet Synchronous Machine Driven by an FPGA Controlled SiC Inverter

This paper presents the hardware development of a 1-kV, 500-A solid state circuit breaker (SSCB) based on the newly proposed T-type Modular Dc Circuit Breaker (T-Breaker) system. The novel T-Breaker is a paradigm shift from traditional solutions in that it integrates fault current management and transient compensation functions in one system. The demonstrated T-Breaker system has a modular structure with two SiC-based half bridge sub-modules on each arm. The prototype has been tested to be 99.58% efficient at 500 A and breaks up to 5 kA of fault current.

Development of a 1 kV, 500 A, SiC-Based T-Type Modular Dc Circuit Breaker (T-Breaker)

Wide bandgap devices in combination with TCM (for soft switching) are typically applied in inverters to achieve high power density and efficiency. This has the disadvantage of a huge current ripple during sinusoidal peak. DPWM counteracts this problem by avoiding switching actions in this section. Due to the rapidly changing voltage across the output capacitors, oscillations within the filter may occur when entering DPWM interval. This current peak can saturate the inductor and the output voltage is distorted as well. This paper proposes a method to mitigate these oscillations by bringing the capacitor voltages to the required voltage prior DPWM interval. Compared to conventional TCM modulation, lower losses result. By damping the oscillations induced by DPWM it is suitable for grid and motor applications.

Modulation Strategy Comprising TCM with Frequency Limit and DPWM for Fast Switching GaN-Inverters

With the demand for higher power and lighter charger/adapters significantly increasing, the application of GaN solutions in this space is equally growing. One of the GaN solutions is the Integrated Power Stage (IPS) which is based on a System in Package (SiP) concept that includes driver and GaN power switch. In contrast to GaN discrete solutions, GaN IPS is very attractive for ≥ 45W to ≤ 1kW power supply applications as it further reduces the converter size, Bill Of Material (BOM) count, and enables ease-of-use while shortening the time to market. This paper reports the latest improvements achieved on a GaN IPS based 65W charger/adapter application demonstrator.

Design and Performance Analysis of High Density Universal Charger featuring GaN based Integrated Power Stage

A three-level gate driver and a power GaN HEMT were integrated on a monolithic chip by an Enhancement-mode GaN-on-SOI process. The chip realises high speed switching and effective three-level gate driving without any external negative power supply. However it has a problem of low heat dissipaton in continuous operations because of the BOX layer and the deep trenches for isolating power devices. Then, the IC was implemented in a C-QFN package and evaluated the tolerance for continuous operation with measuring the case temperature. The measurement result shows that the GaN IC can safely operate continuously in condition of the storage temperature below 64◦C. We attempted to design a small and high power density converter using the fabrication chip.

An Asynchronous Buck Converter by Using a Monolithic GaN IC Integrated by an Enhancement-Mode GaN-on-SOI Process

As the DC current has no natural zero crossing, the development of the DC breakers are much more challenging compared to the AC breakers. In this paper, a Gallium Nitride (GaN) switch-based Resonance Current Source (RCS) is modeled, designed, built, and tested. The RCS was tested separately and in a hybrid dc breaker system for creating an artificial zero current crossing in a vacuum interrupter of a medium voltage Ultra-fast Resonance Direct Current Breaker (UFRDCB). Finally, the performance of the RCS is verified by experiment and the results are presented.

Modeling, Simulation and Hardware Implementation of the GaN Based Resonance Current Source for the Ultra-Fast MVDC Circuit Breaker

Gallium nitride high-electron mobility transistors (GaN HEMTs) have superior switching performance, when compared to similarly rated silicon switches. High switching frequency operation is enabled by low switching transition times
and switching losses. High switching frequency can be beneficial in an electric drive, as the output filter size can be decreased, and furthermore a sinusoidal inverter output current produces low motor losses and torque ripple. Nevertheless, the performance of GaN HEMTs in high switching frequency three-phase inverters
remains unraveled. In this paper, the design and implementation of a three-level ANPC inverter prototype employing GaN HEMTs and a 1 MHz switching frequency is presented. The measured output voltage and current waveforms are sinusoidal, however, some distortions are visible due to modulator design. Furthermore,
the prototype exhibits a peak efficiency of 96.56% at 2.1 kW output power with an LR load.

Three-phase three-level GaN-ANPC inverter with a 1 MHz switching frequency

We investigate the influence of trap filling conditions on the extraction of the emission time constant (τ) of deep levels associated with Fe doping in AlGaN/GaN HEMTs. To this end, we monitor the drain current transients (DCTs) after a short (1 µs) trap filling pulse and investigate the effect of varying (i) gate voltage (VGS,fill) and (ii) drain voltage (VDS,fill) applied during the filling pulse. We find that the extracted τ weakly depends on VGS,fill and it decreases for VDS,fill below 40 V; instead, for VDS,fill > 40 V τ saturates to a value corresponding to the inverse of the emission rate (1/en) at room temperature. The decrease of τ with decreasing VDS,fill was explained with the aid of numerical simulations, by attributing it to the concurrent effect of both emission and capture processes during DCT. This dependence must be taken into account when using DCT to characterize trap emission dynamics in order to correctly estimate the capture cross-section from Arrhenius plots.

Effect of Trap-Filling Bias on the Extraction of the Time Constant of Drain Current Transients in AlGaN/GaN HEMTs

Low temperature power electronics is beneficialin many different applications. Wide band gap (WBG) devices are becoming increasingly popular due to their high performances over the traditional silicon (Si) technology. Different from the gallium nitride (GaN) enhancement mode (E-mode) device, the cascode GaN is composed of a low voltage Si MOSFET and a depletion mode GaN. The advantages of the cascode GaN over E-mode GaN are: 1) easy of drive; 2) high noise immunity. In this article, the cryogenic evaluation results, including both static and dynamic characterizations, for a state-of-the-art high performance 650 V GaNcascode field-effect transistor (FET) are presented and analyzed. The evaluated 650 V cascode GaN FET has better performance under cryogenic temperatures, like low on-state resistance, large threshold volatge, reduced switching times and switching losses. Comparison resultswith the 650 V E-mode GaN device are made, the results demonstrate that the cascode GaN would be more reliable due to the high threshold voltage.

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SiC-Based dv/dt Generator for Insulation Testing with Fast and Adjustable Switching Transients

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