Wide Load Research Articles

A Low Power Low Inrush Current LDO with Different Techniques for PSR and Stability Improvement

One of the most popular power management regulators is the low drop-out voltage regulator (LDO). LDOs have different specifications such as the power supply rejection (PSR) over different frequencies, stability over different load ranges, inrush current spike flows through the input supply, and power consumption. In this work, we present a low power low inrush current LDO design with different techniques for PSR and stability improvement across different frequencies. The LDO presented in this work is a low-power and small area LDO but achieves a high PSR over a wide range of frequencies. The LDO is designed in 65 nm CMOS technology and achieves a PSR better than 80 dB up to 30 MHz for an output load current of 25 mA using an output load capacitor of 4 µF. The design can be used in capless/capped LDOs with wide load current ranges as high as 200 mA and load capacitor range from 1 nF to 12 µF with inrush current improvement by more than 2×. The presented LDO consumes a zero-load quiescent current of 10 µA and its area of 180 µm × 180 µm.

Heritability of Immunity Traits and Resistance of Atlantic Salmon against the Sea Louse Caligus rogercresseyi.

The immune response of Atlantic salmon to sea lice has been extensively studied, but we still do not know the mechanisms by which some fish become resistant and others do not. In this study, we estimated the heritabilities of three key proteins associated with the innate immunity and resistance of Salmo salar against the sea louse Caligus rogercresseyi. In particular, we quantified the abundance of 2 pro-inflammatory cytokines, Tnfα and Il-8, and an antioxidant enzyme, Nkef, in Atlantic salmon skin and gill tissue from 21 families and 268 individuals by indirect ELISA. This covers a wide parasite load range from low or resistant (mean sea lice ± SE = 8.7 ± 0.9) to high or susceptible (mean sea lice ± SE = 43.3 ± 2.0). Our results showed that susceptible fish had higher levels of Nkef and Tnfα than resistant fish in their gills and skin, although gill Il-8 was higher in resistant fish, while no significant differences were found in the skin. Furthermore, moderate to very high heritable genetic variation was estimated for Nkef (h2 skin: 0.96 ± 0.14 and gills: 0.97 ± 0.11) and Tnfα (h2 skin: 0.53 ± 0.17 and gills: 0.32 ± 0.14), but not for Il-8 (h2 skin: 0.22 ± 0.12 ns and gills: 0.09 ± 0.08 ns). This work provides evidence that Nkef and Tnfα protein expressions are highly heritable and related to resistance against sea lice in Atlantic salmon.

Balanced Dual-Side LCC Compensation in IPT Systems Implementing Unity Power Factor for Wide Load Range and Misalignment Tolerance

Misalignment tolerance and wide load range capability are necessary for a practical inductive power transfer (IPT) system. In pursuit of high-performance, input unity power factor and high efficiency are expected. In this paper, a balanced design method of dual-side LCC compensation is proposed to achieve input unity power factor over wide misalignment and load ranges. With the proposed method, dual-side LCC compensation is in a balanced state where zero phase angle frequencies coincide with designed voltage gain frequencies under coupling and load variations. Unity power factor can be implemented while maintaining voltage gain with frequency control. Possible output power versus frequency characteristics of this balanced dual-side LCC compensation are categorized and fully analyzed. One of them, with strong power regulation capability and high misalignment adaptability, is selected as the design target. Coil currents are optimized using a surplus degree of design freedom while selecting parameters. Unity power factor and coil current optimization ensure low losses in devices and coils, which benefits system efficiency. Thus, a wide load range, high misalignment tolerance, nearly zero reactive power, and high efficiency can be simultaneously implemented. The proposed method is verified on a 2.1kW prototype. The coil size of both primary and secondary sides is 600mm <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">×</i> 600mm, and the air gap is 150mm. Load power varies from 10% to 100% within the coupling range from 0.15 to 0.35. Nearly unity power factor is realized under various working conditions. The maximum dc-dc efficiency reaches 96.4%.

Mega-Hertz High-Voltage EMAT Pulser Based on LCC Resonant Inverter Using SiC MOSFETs

Pulse power supply is an important field of high-frequency power electronics. In advanced applications, such as ultrasonic sensors, Lidar waves and laser generators, the voltage supply with high amplitude and high frequency is required to achieve sufficient technical performance. Meanwhile, the high power quality is pursued in some sensor applications to obtain better performance. This paper develops a ±1000 V/1.5 MHz LCC resonant pulse inverter for Electro-Magnetic Acoustic Transducer. First, the LCC filter is optimized to achieve the goals of low THD, small gain variation and ZVS soft-switching in a wide load range. The design guideline of LCC filter for non-resistive load conditions is proposed, and the design considerations for burst mode converters are summarized. Second, the start-up and ending transients occur repetitively, which is a common problem for burst mode converters. The proposed pre-charging and damping strategy solves this transient problem. Moreover, by analyzing the circuit state equations, this strategy provides a general method for eliminating transients of resonant converters. Next, the signal receiving circuit uses depletion mode MOSFETs to attenuate the high transmitting load voltage while amplifying microvolt receiving signals. Finally, the experimental results under four worst-case conditions validate the LCC filter design. A control experiment with or without the proposed transient mitigation method has been conducted to verify the effectiveness of the proposed strategy.

100 MHz Symmetric Current-Mode Class D Wireless Power Transfer

Power conversion for wireless power transfer (WPT) at 100MHz is important for miniaturization and integration, which is critical for charging wearable consumer electronics, and devices for the Internet of Things (IoT). Design and implementation at this frequency are challenging in the selection of components and circuit configurations for operation over a wide load range. The optimization of the tuned compensation networks together with a step-by-step guide for a systematic and rigorous optimal design is derived in this paper from fundamental circuit models for symmetric current-mode class D (CMCD) WPT systems. Symmetric CMCD WPT systems can have inherently constant output current for a wide load range with small current ripple for the optimal design, which is useful in direct battery charging applications. Both uncontrolled and synchronous rectifiers are analyzed, demonstrated, and compared in hardware with the optimal designs. A 100MHz prototype with an output peak power of 6.9W has a power circuit dc–dc efficiency of 81.9% despite only natural convection cooling of miniaturized GaN devices. The prototype maintains nearly constant power circuit efficiency above 80.5% with a peak of 83.2% over a wide power range that spans from 1.7W to 6.9W.

A Three-Level Resonant DAB Converter Featuring Minimized Circulating Losses for EV Battery Charging

A three-level modified series-parallel bidirectional isolated dc <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-$</tex-math></inline-formula> dc resonant converter (TL-MSPBRC) is proposed for EV battery charging. The converter's performance is enhanced for wide load conditions as the modified series-parallel resonant tank is formed by considering the parasitics in the transformer. The first-harmonic approximation (FHA) equivalent circuit model is employed to analyze the converter characteristics for the frequency modulation technique. This converter has high conversion efficiency in charging and discharging operations because of the soft-switching capability of the power switches in the primary and secondary bridges. In addition, low on-state resistance switches in the three-level primary bridge minimize the conduction losses. A 3.3-kW converter prototype with a battery voltage range of 230 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-$</tex-math></inline-formula> 300-V is developed to validate the design method and the simulation results. The proposed converter has minimized circulating losses, good short-circuit protection, and excellent efficiency of 97.7% at the rated power level.

Experimental study on pulverized coal swirl-opposed combustion preheated by a circulating fluidized bed. Part A. Wide-load operation and low-NOx emission characteristics

In this study, the operating characteristics and NOx emission patterns are explored under a wide load range based on a 2MWth pulverized coal preheated combustion test platform. Preheated char with high physical sensible heat and preheated gas with high calorific value greatly improve the ignition and stability of the combustion characteristics of pulverized coal at low loads. Moreover, performing pre-denitrification during the preheating process helps to lower NOx emissions. Stable operation at a wide load range of 26%–106% was achieved, and ultralow loads of 40% and 26% were achieved when the pre-circulating fluidized bed (PCFB) was operated in double-/single-sided operation mode, respectively. Meanwhile, uniform concentration and temperature fields were achieved when both/one side of the PCFB were/was in operation. When operating on the double side of the PCFB, ultralow NOx emissions (@6% O2) of 39.9 mg/m3 and 43.7 mg/m3 were achieved at 40% and 50% loads, respectively. When operating on a single side, the NOx emission amount was 28.3 mg/m3 at 26% load. Furthermore, when the swirling air and the bottom air are equally distributed, the secondary air equivalent ratio is appropriately increased, and the injection position of the burnout air is properly delayed, NOx emissions are reduced.

High-efficiency combustion of gasoline compression ignition (GCI) mode with medium-pressure injection of low-octane gasoline under wide engine load conditions

Gasoline Compression Ignition (GCI) mode with medium injection pressure has the potential to achieve high engine efficiency while keeping costs low. In this study, the combustion and emission characteristics of GCI mode with medium-pressure injection of low-octane gasoline were studied and compared to conventional diesel combustion (CDC) under wide engine loads. The results showed that under low to medium loads, GCI mode had improved particulate emissions and indicated thermal efficiency (ITE) compared to CDC mode. However, at high loads, the PM emissions were much higher than CDC mode, and the ITE decreased for IMEP increasing from 10 to 12 bar due to limited injection pressure. To address this, a dual direct injection GCI mode with medium injection pressure was proposed to improve combustion under high loads. With this strategy, NOx emissions were significantly reduced, and ITE was simultaneously improved for IMEP of 10 and 12 bar. Using low octane gasoline and dual direct injection, the ITE of GCI mode can reach or exceed 50% for IMEP from 4 to 12 bar. Compared to gasoline with a research octane number (RON) of 83, gasoline with an RON of approximately 72 had higher ITE under most tested conditions and is recommended as the fuel for GCI mode.

Experimental study of deep and flexible load adjustment on pulverized coal combustion preheated by a circulating fluidized bed

Peak shaving of coal-fired power plants is a key to promoting renewable energy generation in a grid system. In this study, the deep and flexible load regulation characteristics of pulverized coal preheating combustion are explored. The determination criteria of the variable load related to the preheating temperature, preheated coal gas, combustion temperature and main flue gas (NO, N2O, CO and O2) emission concentrations are established, and the temperature hysteresis coefficient is introduced to characterize the hysteresis of the combustion process. The results show that this system has a deep load regulation capability and can operate stably over a wide load range from 25% to 113%. The chemical reactivity of the pulverized coal is enhanced with thermal modification, which ensures stable combustion in the combustion chamber at ultralow loads. Moreover, the optimal rate of variable load is achieved when the load step is 25%, and the maximum rates of variable load for the preheating process and combustion process are 4.17%/min and 3.13%/min, respectively. Furthermore, an excessively high load step will trigger a large amount of combustion hysteresis, which negatively affects the variable load process.

Asymmetric Trapezoidal Wave Modulation of Modular Multilevel Resonant DC/DC Converter for Current Stress Optimization

A modular multilevel resonant dc/dc converter (MMRDC) possesses high power and high voltage rating, which is adopted for high step-ratio interconnection in dc grid applications. However, the current stress and reactive power of MMRDC are high with the conventional quasi-square-wave modulation scheme when in a wide voltage range and light load conditions. Hence, this article proposes an optimized asymmetric trapezoidal wave (ATW) modulation scheme that reduces current stress over wide load and voltage ranges by separately modulating the duty cycles of string output voltage rising and falling processes. The time-domain mathematical model of MMRDC with the ATW modulation scheme is established. Then, based on the soft switching characteristic and reactive current analysis, the optimized operating point of MMRDC can be derived while considering low current stress and zero voltage switching constraint of low voltage side full-bridge switches. On this basis, the numerical solutions of optimized control variables are obtained, and a control block diagram is presented for the practical implementation of the optimized ATW modulation scheme. Finally, a 4kW MMRDC prototype is constructed, and the experimental results verify the correctness and effectiveness of the analysis and the optimized ATW modulation scheme.

A 180 nA Quiescent Current Digital Control Dual-Mode Buck Converter With a Pulse-Skipping Load Detector for Long-Range Applications

A digitally controlled dual-mode buck converter using low quiescent current is proposed in this work. In particular, the proposed dual pulse-skipping mode adopts a pulse-skipping adaptive on-time (PSAOT) mode for heavy load; and a pulse-skipping asynchronous mode (PSAM) for light and ultra-light loads to achieve a 100,000X wide load range for the Long-range (LoRa) application. Specifically, the pulse-skipping mode selector adopts a digital logic circuit to realize the 180nA low quiescent current. In addition, a low-power dynamic comparator with an adjustable offset is used to accelerate the transient response. The proposed converter is fabricated in a TSMC 350 nm CMOS process and results in an output voltage of 3.3 V from 5V to 4.2 V input voltage range. These results show that the overall system achieves 92.9 % peak eficiency at 8 mA output load and a figure of merit (FoM) of 2.29.

Synchronous rectification of LLC resonant converters based on resonant inductor voltage

Synchronous rectification (SR) technology has been a critical technology for LLC converters to achieve high efficiency and power density. However, conventional SR driving methods face challenges in terms of light-load condition, module size, switching accuracy, and circuit complexity. This paper proposes an SR driving strategy based on resonant inductor voltage (RLV) to address those issues. This RLV-SR driving strategy does not require current sensors and is insensitive to rectifier parasitic parameters. In addition, the RLV-SR driving strategy can be applied in a relatively wide operating frequency range and load conditions. Experimental results based on a 100-W/24-V LLC converter are presented to verify the effectiveness of the proposed RLV-SR driving strategy. Furthermore, the error of turn-on time caused by stray inductance is significantly reduced compared with the conventional VDS-ON sensing method, which improves the power converter’s efficiency.

Oxygen-vacancy-rich tungsten oxide boosted ultrasmall iridium nanoparticles for acidic oxygen evolution

Proton exchange membrane water electrolysis (PEMWE) exhibits the superior benefits including high gas purity, high power density and wide variable loading but is still limited by the prohibitive cost and dearth of iridium (Ir)-based anode catalysts. Herein, we report a low-loading Ir-based catalyst with ultrasmall iridium nanoparticles (1.46 ± 0.01 nm) supported on oxygen-vacancy-rich tungsten oxide nanofibers (WO3-x) through electrospinning combined with surfactant-free microwave-assisted polyol reduction method for active acidic oxygen evolution reaction (OER). According to structural analysis and theoretical calculation, the charge transfer from W to Ir is induced by the strong electronic interaction at the Ir and WO3-x interface, thereby raising the electron density surrounding the Ir sites and favoring to boost OER activity. The resultant Ir@WO3-x exhibits an excellent overpotential of ca. 276 mV@10 mA cm−2 and remarkable durability. This study offers a new path for promoting the activity and durability of electrocatalysts while minimizing the mass loading of Ir towards OER.

The Improved DC Breakdown Strength Induced by Enhanced Interaction between SiO2 Nanoparticles and LLDPE Matrix.

Direct current (DC) power transmission systems have received great attention because it can easily integrate many types of renewable energies and have low energy loss in long-distance and large-capacity power transmission for electricity global sharing. Nanoparticles (NPs) have a positive effect on the insulation properties of polymers, but weak interaction between NPs and polymer matrix greatly decreases the effort of NPs on the enhancement of insulation properties, and thereby limits its engineering application. In this work, grafting strategy was used to link the modified NPs and polymer matrix to improve their interactions. Silica NPs (SiO2-NPs) were modified by 3-(methacrylyloxy) propyl-trimethoxysilane (MPS) to introduce highly active groups on the SiO2-NPs surface, followed by the pre-irradiated linear low-density polyethylene (LLDPE) being easily grafted onto the MPS modified SiO2-NPs (MPS-SiO2-NPs) in the melt blending process to obtain LLDPE-g-MPS-SiO2-NPs nanocomposites. Fourier-transform infrared (FT-IR) spectrum and X-ray photoelectron spectroscopy (XPS) confirm the successful incorporation of MPS into SiO2-NPs. Transmission electron microscopy (TEM) verifies that the modified SiO2-NPs exhibits more uniform distribution. The rheology result shows that the interaction between MPS-SiO2-NPs and LLDPE significantly improves. More importantly, the LLDPE-g-MPS-SiO2-NPs nanocomposites displays superior DC breakdown strength to that fabricated by conventional modification methods. When the addition of MPS-SiO2-NPs is 0.1 wt%, the highest DC breakdown strength values of 525 kV/mm and 372 kV/mm are obtained at 30 °C and 70 °C, respectively, and high DC breakdown strength can be well maintained in a wide loading range of NPs.

Design and Analysis of a High-Efficiency Resonant Converter for EV Battery Charger

The interest in electric vehicle (EVs) components such as battery, battery chargers, and battery management systems is increasing in parallel with the spread of electric vehicles. One of the most critical of these components is battery chargers. Battery chargers are equipped with DC-DC converters with high efficiency, low cost, and wide output voltage range. In order to provide reliable operation of the battery charger, it is of great importance that the DC-DC converters are operated with a robust and stable controller as well as designed optimally. In this paper, a design method for a CLLC resonant converter-based bidirectional dc-dc converter (BiDC) is presented for a battery charger. The resonant converter, whose design details are presented, suggests a resonant system to be used in battery chargers with fewer components than the CLLLC converter, and similar voltage gain characteristics for bidirectional power flow operations compared to the LLC converter. The design procedure highlights performing the soft switching operation and determining the resonant tank parameters. In addition, the forward mode and reverse mode gain equations required for the system to operate in the desired output voltage range have been presented. The design procedures have been validated with a CLLC BiDC model with ratings of 1 kW, 400 V input / 300-450 V output in the PSIM environment. The performance results reveal that the zero voltage switching (ZVS) has been performed for primary-side MOSFETs under a wide load range.

Mechanical behaviors and failure mechanisms of CMDB propellant under wide strain rate tension loading

Composite modified double-base (CMDB) is a sort of mature propellant with a stable structure and high performance. Its tensile mechanical properties should be considered in the structural integrity design of solid propellant charges. The tensile tests were performed on the CMDB by a quasi-static measurement machine. The Hopkinson tension bar (SHTB) under strain rates from 0.0001s−1 to 2500s−1 was modified for structural integrity evaluation, and the stress-strain curves were accurately obtained. After comparing under different strain rates, the results show that the initial modulus of elasticity and stress level are significantly affected by the level of strain rate. Furthermore, the strain hardening becomes more distinct with increasing strain rates. Failure specimens were observed by scanning electron microscopy (SEM). It is indicated that the failure under a low strain rate is mainly debonding of filled particles from the matrix. However, it is mainly caused by their embrittlement under dynamic loading.

A Load Adaptive Digital Gate Driver IC With Integrated 500 ksps ADC for Drive Pattern Selection and Functional Safety Targeting Dependable SiC Application

A fully integrated load adaptive digital gate driver is proposed for high-speed and dependable SiC applications. It breaks the trade-off between surge/ringing and switching loss over a wide load range of 3∼15 A by selecting the gate patterns stored in 8 channel 1.5 kb Look Up Table (LUT). The principle of voltage ringing during turn-off of power devices is analyzed, and a method of temporarily controlling the gate current in the opposite direction is found to be effective. A proposed time resolution expansion technique allows the output of optimal waveforms based on theory without increasing the memory size, achieves the surge/ringing suppression of 51% and reduce the LUT size by 1/12. The integrated 500 ksps Successive Approximation Register (SAR) ADC with steady sampling and automatic VDD selection schemes senses not only the load current, but also the surge and the short circuit for functional safety.

ZVS–ZCS High Step-Up/Step-Down Isolated Bidirectional DC–DC Converter for DC Microgrid

A soft-switched isolated bidirectional dc–dc converter is proposed for distributed generation systems. Dual coupled inductor based flyback energy conversion circuit achieves high voltage step-up/down ratio and high efficiency at lowered duty cycle and, attributes the galvanic isolation. Active switch based capacitor multiplier cell appreciably reduces voltage stresses on low-voltage (LV) and high-voltage (HV) stage MOSFETs, thereby allowing low voltage rating devices(small <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>ds</i>(ON)</sub> ). Active-voltage-clamping type circuit extensively suppresses the voltage spikes across LV-switches caused by leakage inductance. Indeed, this clamp circuitry is formed without any additional switches/diodes, thus reduces clamp device count. By availing of quasi–resonance, thus without needing the HV stage snubber, switching voltage spikes are substantially alleviated. Further, this clamp along with quasi–resonance achieves zero-voltage (ZVS) and zero-current (ZCS) switching, over wide load range, for all switches in both step-up and step-down operations. Reduced voltage stresses, minimized clamp device count, diminished conduction losses and bidirectional soft-switching performance collectively enhances the efficiency. A 600 –W laboratory built set-up working at 75 kHz verifies the viability of the design concept. Measured peak efficiencies in boost and buck stages are 96.65% and 96.58%, respectively.

Multiplexed Active Clamp High-Frequency Link Inverter With De–Re-Coupling Frequency Doubling Modulation

In this paper, a multiplexed active clamp high-frequency link inverter (MACHFLI) with de-re-coupling frequency doubling modulation (DFDM) is proposed. The proposed MACHFLI consists of a primary inverter, high-frequency transformer, multiplexed active clamp (MAC) circuit, and cycloconverter. MAC recycles leakage inductance energy and eliminates voltage spikes caused by leakage inductance. Overlapping commutation is designed in the DFDM to ensure the safe commutation of the output filter inductor current and realize the ZVS of the cycloconverter. The ZVS of the primary inverter can be realized utilizing magnetizing current, and full-range ZVS of MAC can also be realized with turn-on delay. The operating principle and ZVS conditions of the proposed MACHFLI are analyzed, and the design of the transformer and clamp capacitor is discussed in this paper. Finally, a 1kW prototype is made to verify the analysis results. Experimental results show that MACHFLI has Four-quadrant operation capability, good dynamic response, high efficiency over a wide load range, and peak efficiency reaches 95.4&#x0025;.

A 6.78-MHz Wireless Power Transfer System With Inherent Wireless Phase Shift Control Without Feedback Data Sensing Coil

This article presents a 6.78-MHz wireless power transfer (WPT) system with a differential class-D power amplifier (PA) for the transmitter (TX) and a delay-tuned rectifier for the receiver (RX). Besides the RX local voltage regulation, we propose a fully integrated TX global power regulation with wireless phase shift control without any extra off-chip components. Furthermore, the proposed system eliminates the feedback data-sensing coil used in prior arts, thus greatly improving the system integration level and reducing the circuit complexity. On the TX side, the global loop regulates the transmitted power through the duty cycle control of 1X/2X operation modes of the class-D PA to improve the system efficiency over a wide load range. On the RX side, we realize ac–dc power rectification and voltage regulation with a delay-tuned rectifier. The TX and RX chips fabricated in a standard 0.18- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu$</tex-math> </inline-formula> m CMOS process used 3.3-V devices. Measured results show that the circuit can obtain a system efficiency improvement up to 14.2% at light load conditions, with the proposed wireless phase shift control regulating the TX global power. The peak end-to-end system efficiency is 77%, and the maximum output power is 0.9 W with a 3.3-V output voltage.