The backbone of traction drive systems for electrified vehicles is based on the insulated gate bipolar junction transistors (IGBT) created from silicon (Si). Over the last several years, switching devices made from silicon carbide (SiC) and gallium nitride (GaN) have become available. This has resulted in the construction of power electronic systems with greater power densities and better efficiency over similarly rated Si based versions. Yet some hurdles still remain prior to wide spread adoption of these components in automotive power electronics. The following paper reviews the current state-of-art for SiC and GaN based power devices. Challenges in their implementation and barriers to commercialization are presented. This information is supplemented with test results from a thermal investigation. The impact of high speed wide bandgap power devices on the reflected wave phenomenon is also explored.
A heavy low pass filter is usually applied to an on-die temperature sensor's output to filter out the strong noises during switching transients. Aiming at high bandwidth junction temperature sensing, this paper evaluates the electromagnetic noise coupling of an on-die temperature sensing diode in a high power module. Challenges of fast response on-die temperature sensing are reviewed first. Noise coupling mechanisms are analyzed under different grounding configurations and operating conditions. Based on the analysis, a method is proposed to estimate the parasitic capacitance between the sensor and the power device. Special attention has been paid to achieve a high bandwidth and noise immunity test setup. With that, the sensor coupled noises are evaluated in experiments and compared with the model. Noise propagation impedance compensation is applied and verified by experiment. Considerations of sensing circuit design are also discussed. A 100 kHz low pass filter is used to deal with the residual noises during switching transients. With the designed sensing circuitry, short circuit tests are conducted to demonstrate sensor's dynamic response.
This paper provides a comprehensive study on the deployment of the retired Hybrid Electric Vehicle (HEV) battery in residential applications. First, the paper proposes an algorithm for determining the optimal usage profile of the battery pack for a residential house equipped with a roof-top PV system. The proposed algorithm, which is derived from the optimal control theory, minimizes a cost function based on the yearly operation cost of the system. The optimal size of the PV system can also be obtained from this algorithm. Afterward, a flexible experimental platform for the study on the integration of the battery pack in the residential house is configured. The platform utilizes a hybrid Microgrid testbed, which combines Power Hardware-in-the-Loop (PHIL) simulation of electric power network with real hardware. Design considerations are presented, and extensive experiments are conducted to demonstrate the functionality of the platform.
This paper presents an overview of wide bandgap (WBG) power devices. The development and challenges of silicon carbide (SiC) and gallium nitride (GaN) power devices are summerized. A comprehensive evaluation of the performance of different devices is conducted, including static characterization and dynamic switching related tests. The paper also demonstrates the application of WBG devices in power electronic circuits. The testing results are provided to show the performance of WBG devices in different aspects.
This paper presents a single BCD technology platform with high performance power devices at a wide range of operating voltages. The platform offers 6 V to 70 V LDMOS devices. All devices offer best-in-class specific on-resistance of 20 to 40 % lower than that of the state-of-the-art IC-based LDMOS devices and robustness better than the square SOA (safe-operating-area). Fully isolated LDMOS devices, in which independent bias is capable for circuit flexibility, demonstrate superior specific on-resistance (e.g. 11.9 mΩ-mm 2 for breakdown voltage of 39 V). Moreover, the unusual sudden current enhancement appeared in the I D -V D saturation region of most of the high voltage LDMOS devices is significantly suppressed.
Electric vehicle (EV) chargers are traditionally isolated from the grid. Non-isolated chargers have great potential as they enable higher power density at lower cost. Integrated chargers have the potential to utilize existing onboard, high power-rated electronic components for Level 3 charging. Four possible non-isolated integrated charger topologies based on permanent magnet synchronous machine (PMSM) are introduced at the beginning of this paper. Then, the issue of common mode (CM) leakage current through the on-board filters is identified and analyzed. It is found that the leakage current could rise to dangerous levels and cause potential electric shocks to users. The negative influence and safety risks from the leakage current for different grounding systems are also discussed. Experimental results are presented to validate the leakage current analysis. Finally, possible mitigation techniques of the leakage current are discussed.
Intravesical bacillus Calmette-Guerin (BCG) instillation is recommended as an adjuvant therapy for intermediate-risk and high-risk non-muscle invasive bladder cancer (NMIBC) after transurethral resection of bladder tumor (TURBt) with nearly 70% reoccurrence. In the present study, we investigated the dynamics of peripheral purified protein derivative (PPD)-specific immune responses along the treatment. Intravesical BCG instillation caused a significant increase in peripheral PPD-specific IFN-γ release of NMIBC patients, when compared to those receiving chemo-drug instillation. Through a follow-up study, we detected rapid increase in PPD-specific IFN-γ, IL-2, and IL-17A producing CD4 + and CD8 + T cells in the induction phase. Interestingly, the frequencies of PPD-specific IFN-γ and IL-2 producing CD4 + and CD8 + T cells decreased dramatically after induction treatment and were restored after BCG re-instillation, whereas IL-17A-producing T cells remained at the maintenance phase. However, we only observed that the percentages of peripheral CD8 + T cells were significantly higher in BCG responder patients than those in BCG refractory patients at the baseline with the potential of predicting the recurrence. A more dramatic increase in PPD-specific IFN-γ and IL-2 producing CD4 + and CD8 + T cells after one and two dose BCG instillations was observed in refractory NMIBC patients. Therefore, regional BCG instillation induced transient peripheral PPD-specific T cell responses, which could be restored through repetitive BCG instillation. Higher proportions of peripheral CD8 + T cells at baseline were associated with better responses to BCG instillation for the prevention of recurrence of bladder cancer.
This paper presents an overview of the latest Gallium Nitride High Electron Mobility Transistor (GaN HEMT) technology. The latest development and challenges of 30 V to 650 V GaN HEMTs are summarized. The evaluation methodology of the GaN HEMT is presented, including static characterization and dynamic characterization. The paper also demonstrates the application of GaN HEMTs developed by Center for High Performance Power Electronics (CHPPE). Various high efficiency high power density circuit prototypes based on GaN HEMTs are presented.
The Quasi-Switched-Capacitor (QSC) resonant converter has been proposed to serve as the isolated dc/dc stage of ac/dc power adapters for portable electronics. Compared to Flyback and LLC resonant converters, its features include: the voltage stress on the primary-side switches is reduced to 2/3 of the input voltage, which is friendlier to low-voltage switches whose figure of merits is generally better; and the transformer turns ratio is reduced by 2/3, which enables less number of turns, lower winding loss and lower leakage inductance of the transformer. In this paper: Two types of resonance which lead to ZCS and ZVS respectively are identified to achieve the optimal normal-mode operation. The optimal duty ratio and switching frequency are implemented to achieve full soft switching and reduce the switching loss; and burst-mode control is implemented to improve the light-load efficiency. Simulation results and experimental results from a 90-W, 88-V/19-V prototype based on eGaN FETs validate the proposed techniques. The converter achieves a flat efficiency curve with a peak value of 96% at 700 kHz. Compared to earlier results without optimization, the efficiency is improved by 2~20% within the full load range.
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