Current sourceinverters (CSIs) require power switches with first quadrant current conduction and gate-controlled output characteristics as well as reverse blocking capability. Experimental ...demonstration of a SiC monolithic reverse blocking transistor (MRBT) suitable for CSI applications is described in this letter. The proposed device is based on the integration of a SiC JBS diode with a SiC power mosfet on the same chip. The cathode of the SiC JBS diode is connected to the drain of the SiC power mosfet by their common N + substrate. The proposed device structure creates a novel SiC-based unipolar single-chip three-terminal transistor with reverse blocking capability. The measured characteristics of a 1.2 kV 4H-SiC MRBT, fabricated in a commercial six-inch wafer foundry, are reported in this letter. The devices show a diode-like on -state characteristic with a low knee voltage of 1.3 V and an on -state voltage drop of 2.8 V at 5 A. The measured reverse transfer capacitance and output capacitance for the MRBT at a drain bias of 2 and 1000 V are a factor of ∼3x and ∼1.6x smaller than the measured values for the internal mosfet device. Switching measurements show a 12% reduction in the gate-drain charge for the MRBT compared with the internal mosfet which is favorable for reducing switching losses.
The high-frequency capacitive and switching response of ferroelectric Hf0.5Zr0.5O2 (HZO) is investigated on scaled ferroelectric metal-oxide-semiconductor III-V capacitors. Spanning over six orders ...of magnitude, the measured frequency response allows for accurate modeling of the capacitance-frequency dispersion. The steady-state ferroelectric behavior is retained even in the mm-wave frequency range and provides a 25% capacitive tunability, demonstrating its applicability as a non-volatile reconfigurable varactor. The measured film reconfigurability is in the nanosecond time-regime, mainly limited by the measurement setup.
Capacitors are one type of reliability-critical components in power electronic systems. In the last two decades, many efforts in academic research have been devoted to the condition monitoring of ...capacitors to estimate their health status. Industry applications are demanding more reliable power electronics products with preventive maintenance. Nevertheless, most of the developed capacitor condition monitoring technologies are rarely adopted by industry due to the complexity, increased cost, and other relevant issues. An overview of the prior-art research in this area is therefore needed to justify the required resources and the corresponding performance of each key method. It serves to provide a guideline for industry to evaluate the available solutions by technology benchmarking, as well as to advance the academic research by discussing the history development and the future opportunities. Therefore, this paper first classifies the capacitor condition monitoring methods into three categories, then the respective technology evolution in the last two decades is summarized. Finally, the state-of-the-art research and the future opportunities targeting for industry applications are given.
•We studied the effect of time on the characteristics of passive film formed on 316SS.•Both the film thickness and film resistance increase with time.•The increase of film thickness and resistance ...follows the direct logarithmic law.•The carriers’ density of the inner and outer layer of film both increase with time.•The increase of carriers’ density is related to the distribution of FeOOH.
By potentiostatic polarisation for different time, passive films were formed on AISI 316SS. Characteristics of these films were studied using electrochemical measurement and surface analysis method. The results show the film thickness, film resistance and carriers’ density in the film all increase with time, and the increase of the film thickness and resistance both follows the direct logarithmic law. As time prolongs, FeOOH penetrates deep into the film, and its concentration in the film also increases, while the distribution of the other components of the film changes a little. The changing mechanisms of passive film characteristics with time were analysed.
Detecting the power-device state-of-health (SOH) during converter operation can enhance the overall system reliability by predicting imminent failure scenarios. While various aging indicators for ...gallium nitride (GaN) devices have been demonstrated in the literature, few are practically measurable in an active converter. This article demonstrates that the large-signal device output capacitance (<inline-formula><tex-math notation="LaTeX">C_{\text{oss}}</tex-math></inline-formula>) is a reliable indicator of short-circuit (SC) aging, and proposes an in situ measurement technique to capture its value by leveraging the operational waveforms of soft-switching converters. The method relies only on the converter operating condition along with the switching modulation and does not require direct measurement of the inductor current. Experimental results for three different GaN devices show a 5%-10% decrease in the large-signal <inline-formula><tex-math notation="LaTeX">C_{\text{oss}}</tex-math></inline-formula> after 5000 SC cycles, proving the usefulness of this parameter as an SOH indicator. The in situ measurement technique is demonstrated in a synchronous buck converter operating in discontinuous conduction mode, successfully capturing the SC-aging-induced change in <inline-formula><tex-math notation="LaTeX">C_{\text{oss}}</tex-math></inline-formula>. The presented results and proposed measurement technique pave the way for system-level monitoring of power-device SOH and self-calibrating operation.
Condition-monitoring systems are used to determine the best timing for predictive maintenance of power electronics converters. These monitoring systems can significantly reduce the converter repair ...time and increase system availability. In this article, an investigation has been conducted on the possibility of using the dissipation factor as a lifetime indicator of electrolytic capacitors. A criterion is also proposed based on the dissipation factor to detect electrolytic capacitors' end of useful life. A method has been presented for measuring the dc-link capacitor dissipation factor in a back-to-back converter. Using this technique, it is possible to estimate the switching component of the capacitor current by measuring the output currents of the converter without a need to measure the capacitor current directly. The proposed method is simulated, and the impact of various factors, such as switching frequency, capacitor series inductor, and the network filter on the accuracy of the dissipation factor measurement, is discussed. Experimental results are also provided to validate the acceptable accuracy of the proposed method.
Capacitance detection is a universal transduction mechanism used in a wide variety of sensors and applications. It requires an electronic front-end converting the capacitance variation into another ...more convenient physical variable, ultimately determining the performance of the whole sensor. In this paper we present a comprehensive review of the different signal conditioning front-end topologies targeted in particular at sub-femtofarad resolution. Main design equations and analysis of the limits due to noise are reported in order to provide the designer with guidelines for choosing the most suitable topology according to the main design specifications, namely energy consumption, area occupation, measuring time and resolution. A data-driven comparison of the different solutions in literature is also carried out revealing that resolution, measuring time, area occupation and energy/conversion lower than 100 aF, 1 ms 0.1 mm2, and 100 pJ/conv. can be obtained by capacitance to digital topologies, which therefore allow to get the best compromise among all design specifications.
Even though the sense of touch is crucial for humans, most humanoid robots lack tactile sensing. While a large number of sensing technologies exist, it is not trivial to incorporate them into a ...robot. We have developed a compliant "skin" for humanoids that integrates a distributed pressure sensor based on capacitive technology. The skin is modular and can be deployed on nonflat surfaces. Each module scans locally a limited number of tactile-sensing elements and sends the data through a serial bus. This is a critical advantage as it reduces the number of wires. The resulting system is compact and has been successfully integrated into three different humanoid robots. We have performed tests that show that the sensor has favorable characteristics and implemented algorithms to compensate the hysteresis and drift of the sensor. Experiments with the humanoid robot iCub prove that the sensors can be used to grasp unmodeled, fragile objects.
Abstract
A new type of capacitance measuring instrument includes a microprocessor, a capacitance sensing sensor, a LC oscillation circuit, a computer, a display and a buzzer. The LC oscillation ...circuit is connected with the measured capacitance CS to generate an oscillation frequency, and the oscillation frequency is sent to the capacitance sensing sensor. After being processed by the capacitance sensing sensor, it is converted into a 28 bit binary number and sent to the said controller through the IIC interface When a successful measurement is completed, the microprocessor controls the buzzer to sound once and sends the measurement results to the display or computer, which has the advantages of high precision, short measurement time, etc.
Compared with positive pressure measurement, which is widely used in many fields, negative pressure measurement is often ignored. However, realizing full pressure measurement, that is, positive and ...negative pressure measurement, with high sensitivity and wide measurement range, is one of the most urgent development directions and key challenges faced by flexible pressure sensors. To overcome this challenging problem, a highly sensitive full-pressure capacitive sensor with surface microstructure and hydrogels is introduced in this paper. The sensing mechanism of the sensor is implemented by detecting the capacitance change caused by the change in the contact area between the hydrogel and the electrode due to the internal and external pressure difference. The PVA/KOH basic gel material is used to resist shear deformation, and the uniform microstructure on the gel surface is achieved by the template method. How to maximize the sensitivity of positive and negative pressure measurements is discussed by carefully evaluating the design parameters of the sensor. The fabricated sensor has a wide measurement range (-100–250 kPa) with high sensitivity (S = 15.6 nF/kPa) in the negative pressure region and (S = 5.2 nF/kPa) in the positive pressure region. In addition, the sensor exhibits fast response, cycle stability, and low measurement limit, which further enhances its performance advantages. In order to validate the application potential of the sensor, the paper conducts experimental verification using the relationship between wind pressure measurement results and the angle of contact with the sensor, as well as the relationship between vehicle speed and wind pressure magnitude. The results show that the designed sensor has potential application prospects in full pressure measurement.
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•Sensing relies on capacitance changes from hydrogel-electrode contact, detecting internal/external pressure differences. Measures both positive and negative pressure.•PVA/KOH alkaline gel resists shear, maintaining uniform surface microstructure. Sensor shows high sensitivity, wide range, and consistency.•Careful evaluation of sensor design parameters focuses on maximizing sensitivity for positive and negative pressure measurements.
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