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"Current sources"
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A novel programmable wide swing buffer for OLED source driver
This paper presents the design of an output buffer with DAC functionality, which meets the requirements of small size, low power consumption, and high precision for OLED source driver chips. The two-stage DAC has a smaller area compared to traditional resistor string DACs, providing higher precision grayscale voltages that better meet the requirements of display drivers. The buffer utilizes a rail-to-rail input stage and Class AB output stage to achieve a wide input-output voltage range. Cascode Miller compensation is employed to improve stability, and a programmable tail current source with current steering DAC is used to realize 3-bit interpolation, saving overall chip area and power consumption. In the HLMC 55 nm CMOS process, the buffer has a rise time of 0.52 us and a fall time of 0.6 us for input voltages ranging from 0-1.2 V. The buffer occupies an area of 35×30 um 2 .
Journal Article
Imaging of plant current pathways for non-invasive root Phenotyping using a newly developed electrical current source density approach
Aims
The flow of electric current in the root-soil system relates to the pathways of water and solutes, its characterization provides information on the root architecture and functioning. We developed a current source density approach with the goal of non-invasively image the current pathways in the root-soil system.
Methods
A current flow is applied from the plant stem to the soil, the proposed geoelectrical approach images the resulting distribution and intensity of the electric current in the root-soil system. The numerical inversion procedure underlying the approach was tested in numerical simulations and laboratory experiments with artificial metallic roots. We validated the method using rhizotron laboratory experiments on maize and cotton plants.
Results
Results from numerical and laboratory tests showed that our inversion approach was capable of imaging root-like distributions of the current source. In maize and cotton, roots acted as “leaky conductors”, resulting in successful imaging of the root crowns and negligible contribution of distal roots to the current flow. In contrast, the electrical insulating behavior of the cotton stems in dry soil supports the hypothesis that suberin layers can affect the mobility of ions and water.
Conclusions
The proposed approach with rhizotrons studies provides the first direct and concurrent characterization of the root-soil current pathways and their relationship with root functioning and architecture. This approach fills a major gap toward non-destructive imaging of roots in their natural soil environment.
Journal Article
Fixed-time dynamic surface high-order sliding mode control for chaotic oscillation in power system
In this paper, a fixed-time dynamic surface high-order sliding mode control approach is presented for chaos suppression and voltage stabilization in three-bus power system via design of current source converter-based static synchronous compensator controller. The proposed control strategy constructs two high-order sliding mode surfaces to achieve control objective. By combining backstepping idea with dynamic surface control (DSC) technique, high-order sliding mode controller is designed and the inherent problem of “explosion of complexity” in backstepping design is avoided. Further, a new stability concept is introduced into DSC design to achieve semi-global uniform ultimate boundedness of the signals in high-order sliding mode system within finite time independent of initial condition. In addition, stability analysis is provided to show that the proposed control scheme can achieve semi-globally fixed-timely uniformly ultimately bounded stabilization. Finally, simulation results are given to demonstrate the effectiveness of the proposed control scheme and the superior performance over conventional DSC.
Journal Article
An Active Clamp Dual-Inductor Isolated Current Source to Current Source Converter with Wide Output Voltage Range
Human observation of the ocean has gradually evolved from the sea surface to systematic monitoring and sampling through seafloor observation networks, and constant current power supply has become the main power supply method for seafloor observation networks due to its high reliability. There are some studies on current source to voltage source converters, but there are few studies on current source to current source (CS/CS) converters, which affects the expansion of power supply networks for seafloor observation networks. In this paper, by employing input current sharing and output voltage doubling circuits, an active clamp dual-inductor isolated CS/CS converter which uses a single-stage conversion circuit to realize constant current source conversion with a wide output voltage range is proposed. Active clamp technology at the primary side of the proposed circuit is employed to recover energy stored in leakage inductance, suppress voltage spikes of the primary side switches, and achieve zero-voltage switching of the primary side switches. The secondary side’s output voltage doubling circuit resonates with transformer leakage inductance to achieve zero-current switching of the secondary side diodes, which can reduce losses and enhance efficiency. The operating principles of the proposed circuit are analyzed in detail, and the characteristic and parameter design analysis, including current conversion ratio, transformer turn ratio, power inductors, and resonant capacitors and inductor, are presented. Finally, the experimental results based on a 100 W experimental prototype validate the feasibility of the proposed converter.
Journal Article
Portable and inexpensive electrochemical impedance spectroscopy system for characterization of saline solution impedance
The developed portable and inexpensive EIS instruments can measure impedance spectra from 0.01 Hz to 100 kHz . The instruments include a programmable current source from 1 μA to 300 μA for adjusting the range of impedance of the sample, which is possibly from 10 Ω to 1 kΩ , gain phase detector-based data acquisition, and microcontroller-PC-based software for controlling, collecting, and real-time plotting data in Bode and Nyquist diagram. The EIS system was validated by measuring dummy components’ impedance, resulting in less than 2% error. The system can measure the sample’s impedance and investigate the electrode-sample interface’s double-layer phenomenon with the available frequency range. This phenomenon is experienced in every impedance measurement and can affect the interpretation of the measurement spectrum. Furthermore, the instrument is applied to characterize the impedance of two different saline solutions (KCl and MgCl 2 ) and the double-layer phenomena between electrode-electrolytes.
Journal Article
Field-Tunable Spin–Valley Polarized Transport in Zigzag Germanene Nanoribbons
Valleytronics has emerged as a rapidly developing field in recent years. However, transmitting information via valley currents faces significant challenges. In most candidate materials, the lack of intrinsic symmetry protection facilitates intervalley scattering. This mixing of valley currents from the
K
and
K
' valleys disrupts the directional integrity of carrier flow. Indeed, spin-valley polarization can reduce intervalley scattering probability, thereby improving the accuracy and stability of valley-current transport. In this work, we use a local electric field in zigzag germanene nanoribbons (ZGeNR) exhibiting the quantum Hall (QH) effect to achieve the quantum spin-valley Hall (QSVH) effect, generating two counter-propagating spin-valley polarized currents. Subsequently, applying a global electric field separates these two oppositely polarized currents in energy, yielding a singly spin-valley polarized current. This system can be employed to design programmable polarized current sources and shows promise for realizing singly spin-valley polarized Andreev reflection.
Journal Article
Near-Bottom ROV-Borne Self-Potential Exploration of Seafloor Massive Sulfide Deposits on the Southwest Indian Ridge
Seafloor massive sulfide (SMS) deposits formed by hydrothermal circulation generate measurable self-potential (SP) anomalies in seawater, providing an effective geophysical indicator of sulfide mineralization. In this study, a remotely operated vehicle (ROV)-borne SP survey was conducted at the Yuhuang hydrothermal field on the Southwest Indian Ridge to investigate the spatial distribution of SMS mineralization. The survey operated at a near-bottom altitude of approximately 10 m, substantially lower than that typically achieved by autonomous underwater vehicles (AUVs) or towed systems, enabling high-resolution data acquisition with improved signal quality. To efficiently discretize complex seafloor topography under irregular data coverage, an adaptive octree mesh was employed, enabling computationally efficient three-dimensional inversion over a large survey area and recovery of the subsurface source current density distribution. The inversion results resolve a main anomaly zone spatially correlated with known SMS mineralization, as well as an additional anomaly zone that was not resolved by previous surveys and suggests potential mineralization. Anomalies associated with known mineralization show good spatial agreement with independent near-bottom observations and drilling results. The results demonstrate that ROV-borne SP surveying combined with adaptive meshing and three-dimensional inversion provides a reliable approach for imaging SMS mineralization in deep-sea environments.
Journal Article
Programmable Current Source Design for Multi-channel Magnetic Field Generator Programmable current source
The three-dimensional motion of magnetic micro-robots requires the control of multiple magnetic field generators working simultaneously. The current program-controlled current sources in the market are generally expensive and it is difficult to control multiple program-controlled current sources by a single controller to change the output current at the same time. In order to compress the experimental cost, reduce the experimental threshold, realize the simultaneous control of multiple magnetic field generators and make them work stably, this paper proposes a special program-controlled current source design for multiple magnetic field generators, and verifies the feasibility of the design through experimental tests. The results show that the dedicated current source is able to output 0.3∼6.5A under ±12V switching power supply test when each current source is connected to a 1.5 ohm solenoid coil with internal resistance. The system meets the requirements of 3% or less output current error and fast response time while greatly reducing costs and achieving good interactivity.
Journal Article