Showing papers on "Current sensor published in 2012"

New Digital-Controlled Technique for Battery Charger With Constant Current and Voltage Control Without Current Feedback

Abstract: The main theme of this paper is to present a new digital-controlled technique for battery charger to achieve constant current and voltage control while not requiring current feedback. The basic idea is to achieve constant current charging control by limiting the duty cycle of charger. Therefore, the current feedback signal is not required and thereby reducing the cost of A/D converter, current sensor, and computation complexity required for current control. Moreover, when the battery voltage is increased to the preset voltage level using constant current charge, the charger changes the control mode to constant voltage charge. A digital-controlled charger is designed and implemented for uninterrupted power supply (UPS) applications. The charger control is based upon the proposed control method in software. As a result, the UPS control, including boost converter, charger, and inverter control can be realized using only one low cost MCU. Experimental results demonstrate that the effectiveness of the design and implementation.

A Three-Phase Current Reconstruction Strategy With Online Current Offset Compensation Using a Single Current Sensor

Abstract: This paper proposes a three-phase current reconstruction technique with an online current offset compensation function for three-phase inverter applications utilizing only a single current sensor. In the proposed current sensing method, a phase current and a branch current are simultaneously measured twice in a switching period by using a single current sensor. After that, the current reconstruction algorithm is applied to obtain the three-phase current information. Compared to previous single current sensor strategies, in the proposed method, the sensor output is regularly sampled, and the dead zone is located near the boundary of the voltage vector space instead of near the origin and the borders of each sector. This boundary-neighbored dead zone makes the proposed method more attractive in extremely low modulation index cases because it avoids periodical dead zones which have been an issue in the existing methods. Moreover, the online compensation method for a current measurement offset makes it possible to achieve purely balanced three-phase current control without an offset component. The effectiveness of the proposed method has been verified through simulations and experiments by measuring and reconstructing three-phase currents under various conditions.

A current sensor based on the giant magnetoresistance effect: design and potential smart grid applications.

Abstract: Advanced sensing and measurement techniques are key technologies to realize a smart grid. The giant magnetoresistance (GMR) effect has revolutionized the fields of data storage and magnetic measurement. In this work, a design of a GMR current sensor based on a commercial analog GMR chip for applications in a smart grid is presented and discussed. Static, dynamic and thermal properties of the sensor were characterized. The characterizations showed that in the operation range from 0 to ±5 A, the sensor had a sensitivity of 28 mV·A−1, linearity of 99.97%, maximum deviation of 2.717%, frequency response of −1.5 dB at 10 kHz current measurement, and maximum change of the amplitude response of 0.0335%·°C−1 with thermal compensation. In the distributed real-time measurement and monitoring of a smart grid system, the GMR current sensor shows excellent performance and is cost effective, making it suitable for applications such as steady-state and transient-state monitoring. With the advantages of having a high sensitivity, high linearity, small volume, low cost, and simple structure, the GMR current sensor is promising for the measurement and monitoring of smart grids.

Novel Self-Configurable Current-Mirror Techniques for Reducing Current Imbalance in Parallel Light-Emitting Diode (LED) Strings

Abstract: Traditional current-mirror methods require one fixed current reference for controlling other current source or sources. In this paper, a new self-configurable current-mirror method that can dynamically determine the best current branch as the current reference in order to ensure good balance of all parallel current sources is proposed. The operating principle involves a dynamic and self-configurable transistor-based current-balancing circuit that can be operated in saturation or linear mode. In either operating mode, good current balance or sharing among all parallel-connected current sources can be guaranteed. The novel current-balancing circuit does not require a separate power supply for powering their control circuits. The proposal is a modular one that can be expanded to any number of parallel current sources. Its principle has been successfully applied to current balancing of parallel LED strings.

Hybrid Optoelectronic Sensor for Current and Temperature Monitoring in Overhead Transmission Lines

Abstract: This letter describes the development of a hybrid optoelectronic current and temperature sensor for evaluating the sag of conductors in high voltage transmission lines. This 4 kg portable current transformer was developed using alternative materials to the heavy items that constitute a conventional transformer: iron core, copper coil and insulating ceramics. The system uses reliably proven electronic technology to measure temperature and current, while using fiber-optic technology to energize the electronic circuitry and transmit the signals back via optical fibers. The data collected, together with the sag information, will provide support for the development of an algorithm for the estimation of conductor-sag values.

A miniature digital current sensor with differential Hall probes using enhanced chopping techniques and mechanical stress compensation

Abstract: A 10kHz bandwidth 50Amax current sensor using a Hall effect gradiometer without magnetic core provides 80kHz update rate with a digital interface. Very low un-calibrated offset of 30mA (1σ) and after calibration typical 10mA over temperature is accomplished by a chopped multi-bit feedback continuous-time 3rd order ΔΣ-ADC. This also realizes low noise of 13mA rms in 1kHz signal bandwidth. The ADC uses enhanced chopping techniques and additional digital feedback loops to avoid chopper ripple. New analog and digital stress-compensation circuits with lateral and vertical n-doped resistors achieve lifetime gain drifts below 1% and temperature compensation. Auto-zeroing ping-pong comparators offer a fast over-current detection of 1…2μs on a dedicated output pin. The monolithic integrated sensor chip and the 4kV galvanic isolated current rail fit into a very small 7×7×1mm3 package.

Controlling a user's tactile perception in a dynamic physical environment

Abstract: To maintain consistency in different environments with different impedances, a high voltage current driver may be used as a signal generator to output a tactile signal with a constant current. The constant current ensures that the voltage between the user's finger and the object's surface or electrode remains the same even if impedances in the electrical path change. Specifically, the current driver includes a current sensing circuit that determines the average current being generated. Using a feedback loop, the measured current is compared to a reference current to determine if the correct tactile sensation is perceived by the user. As the impedance changes, the current driver detects the resulting change in the signal's current and adjusts the voltage amplitude of the generated tactile signal in order to match the measured current to the reference current.

Disk drive comprising extended range head proximity sensor

Abstract: A disk drive is disclosed comprising a head actuated over a disk, and a fly height transducer operable to generate a fly height signal for the head. The disk drive further comprises control circuitry comprising a current sensor operable to detect a current flowing through the fly height transducer. The current sensor comprises a differential amplifier operable to amplify the current flowing through the fly height transducer over a first range using a first gain, and amplify the current flowing through the fly height transducer over a second range using a second gain less than the first gain, wherein at least part of the second range is different than the first range.

Average Inductor Current Sensor for Digitally Controlled Switched-Mode Power Supplies

Abstract: Current-mode control in digitally controlled switched-mode power supplies typically requires analog-to-digital (A/D) conversion of at least two signals, voltage, and current. The complexity of voltage A/D converters can be reduced using window A/D techniques. In conventional current A/D conversion, however, relatively high resolution is required over a wide range of signals, which results in increased complexity, power consumption, and cost of the controller. This paper proposes a very simple feedback sensor capable of high-resolution average inductor current sensing using two analog comparators and an analog low-pass filter. The approach requires very few external components and employs minimal digital hardware resources. A dynamic model and performance of the average inductor current sensor are experimentally verified on a 12-V input, 19-V output, 50-W boost converter prototype. The applicability of the proposed sensor is demonstrated in a digitally controlled 400-W, 400-V output Boost power factor preregulator.

Two-terminal current controller and related led lighting device

Abstract: A two-terminal current controller having a current limiting unit and an adjusting unit regulates a first current flowing through a load according to a load voltage. When the load voltage does not exceed a first voltage, the two-terminal current controller operates in a first mode for conducting a second current associated a rectified AC voltage, thereby limiting the first current to zero and adjusting the second current accordingly. When the load voltage is between the first voltage and a second voltage, the two-terminal current controller operates in a second mode for conducting the second current, thereby limiting the first current to zero and limiting the second current to a constant value larger than zero. When the load voltage exceeds the second voltage, the two-terminal current controller operates in a third mode for turning off the current limiting unit. The adjusting unit can adjust the predetermined value and the second voltage.

Improved performance of TES bolometers using digital feedback

Abstract: Voltage biased, frequency multiplexed TES bolometers have become a widespread tool in mm-wave astrophysics. However, parasitic impedance and dynamic range issues can limit stability, performance, and multiplexing factors. Here, we present novel methods of overcoming these challenges, achieved through digital feedback, implemented on a Field-Programmable Gate Array (FPGA). In the first method, known as Digital Active Nulling (DAN), the current sensor (e.g. SQUID) is nulled in a separate digital feedback loop for each bolometer frequency. This nulling removes the dynamic range limitation on the current sensor, increases its linearity, and reduces its effective input impedance. Additionally, DAN removes constraints on wiring lengths and maximum multiplexing frequency. DAN has been fully implemented and tested. Integration for current experiments, including the South Pole Telescope, will be discussed. We also present a digital mechanism for strongly increasing stability in the presence of large series impedances, known as Digitally Enhanced Voltage Bias (DEVB).

A Current-Mode DC–DC Buck Converter with Efficiency-Optimized Frequency Control and Reconfigurable Compensation

Abstract: Large input voltage range and wide output current range are usually needed for dc-dc converters. For these input and output conditions, the converter's efficiency can be maximized by a proposed method, efficiency-optimized switching-frequency (EOF) control. The optimal switching frequency for maximizing the efficiency is generated by the low-complexity and low-power EOF generator. A reconfigurable compensator is developed for improving the load regulation and the transient response. A piecewise-linear current sensor (PLCS) is employed to reduce controller power loss without sacrificing the sensing accuracy. With the aforementioned three proposed methods, a monolithic current-mode dc-dc buck converter is implemented in a 0.35-μm 3.3-V CMOS process. The measured power-loss reductions and efficiency improvements achieve 16 and 15 mW, and 16% and 1%, both in light and heavy loads, respectively. The load regulation and the transient recovery time are improved by 40 mV and 12 μs, respectively, while the PLCS can reduce 3 mW of power loss. Compared with other published converters in 0.35-μm CMOS process, the implemented converter achieves a higher efficiency of 96.3% and smaller chip area of 0.97 mm.

An Active Current Reconstruction and Balancing Strategy With DC-Link Current Sensing for a Multi-phase Coupled-Inductor Converter

Abstract: This paper proposes an active technique to reconstruct and balance the phase currents in multiphase dc-dc converters implementing both of voltage- and current-mode controls. Only one current sensor at the dc link is required to measure and reconstruct the phase currents. Multiple current samples in the pulsewidth modulation switching period are synchronized with the carrier waveforms to actively reconstruct the phase currents using a simple active balancing algorithm that is implemented in a digital controller. The proposed technique improves system performance, stability, and efficiency, and prevents inductor saturation. A 5-kW four-phase dc-dc converter prototype for battery charging application is built to experimentally verify the proposed algorithm.

High-resolution current sensor utilizing nanocrystalline alloy and magnetoelectric laminate composite.

Abstract: A self-powered currentsensor consisting of the magnetostrictive/piezoelectric laminatecomposite and the high-permeability nanocrystalline alloys is presented. The induced vortexmagnetic flux is concentrated and amplified by using an optimized-shape nanocrystalline alloy of FeCuNbSiB into the magnetoelectric laminatecomposite; this optimization allows improving the sensitivity significantly as well as increasing the saturation of the currentsensor. The main advantages of this currentsensor are its large dynamic range and ability to measurecurrents accurately. An analytical expression for the relationship between current and voltage is derived by using the magnetic circuit principle, which predicts the measured sensitivity well. The experimental results exhibit an approximately linear relationship between the electric current and the induced voltage. The dynamic range of this sensor is from 0.01 A to 150 A, and a small electric current step-change of 0.01 A can be clearly distinguished at the power-line frequency of 50 Hz. We demonstrate that the currentsensor has a flat operational frequency in the range of 1 Hz–20 kHz relative to a conventional induction coil. The currentsensor indicates great potentials for monitoring conditions of electrical facilities in practical applications due to the large dynamic range, linear sensitivity, wide bandwidth frequency response, and good time stability.

High accuracy differential current sensor for applications like ground fault interrupters

Abstract: A sensor with multiple magnetic field sensing elements for use in current sensing and other applications is presented. In one configuration, the sensor can obtain differential and absolute current measurements of current in current-carrying conductors. When employed in a ground fault interrupter (GFI) application, a first magnetic field sensing element can be used to measure the absolute current flowing in the phase conductor (phase current), a second magnetic field sensing element can be used to measure the absolute current flowing in the neutral conductor (neutral current) and a difference between the phase and neutral currents can be measured by a third magnetic field sensing element or determined from measurements of the first and second magnetic field sensing elements. In another configuration, the sensor can obtain a measure of the difference between currents and/or the sum of currents in current-carrying conductors.

Charging system with adaptive power management

Abstract: An embodiment of a charger may include an input, at least one switch having a first node coupled to a reference voltage, a current sensor coupled between the input and a second node of the at least one switch, an output coupled to a third node of the at least one switch, and a charge controller coupled to the input to determine an input voltage, to the current sensor to determine an input current and to control inputs of the at least one switch. The at least one switch may be responsive to control signals supplied by the charge controller to the control inputs thereof to control voltage and current at the output of the charger. The charge controller may be responsive to the input voltage and the input current to produce the control signals in a manner that maximizes electrical power drawn at the input.

High-current-sensitivity all-fiber current sensor based on fiber loop architecture

Abstract: In this paper, we demonstrate a novel all-fiber current sensor using ordinary silica fiber. The sensor employs a fiber solenoid as a current sensor head, which improves the current sensitivity by allowing optical signals to traverse the sensor head repeatedly. Theory and experiment prove that the improvement in sensitivity increases periodically with the number of repetitions of optical signals circulating round the loop.

Current driving circuit and display device using the current driving circuit

Abstract: A current drive circuit which can improve a rate for signal writing and a driving rate of an element even when a signal current is small, and a display device using the current drive circuit are provided The current drive circuit for supplying a signal current to a node of a driven circuit through a signal line includes a precharge function for supplying a precharge voltage to the node through the signal line and the precharge function includes a supply function for supplying the precharge voltage to the node and the signal line prior to supplying the signal current

Flexible current and voltage sensor

Abstract: A flexible current and voltage sensor provides ease of installation of a current sensor, and optionally a voltage sensor in application such as AC branch circuit wire measurements, which may require installation in dense wiring conditions and/or in live panels where insulating gloves must be worn. The sensor includes at least one flexible ferromagnetic strip that is affixed to a current sensing device at a first end. The second end is secured to the other side of the current sensing device or to another flexible ferromagnetic strip extending from the other side of the current sensing device to form a loop providing a closed pathway for magnetic flux. A voltage sensor may be provided by metal foil affixed to the inside of the flexible ferromagnetic strip. A clamp body, which can be a spring loaded handle operated clamp or a locking fastener, can secure the ferromagnetic strip around the wire.

Field programmable gate array-based fault-tolerant hysteresis current control for AC machine drives

Abstract: This study presents a field programmable gate array (FPGA) implementation of a simple fault-tolerant control that ensures continuous operation of hysteresis current controlled AC machine drives under faulty current sensor. The adopted control requires the use of three current sensors and is available for three-phase isolated neutral systems. The third current sensor allows the faulty current sensor detection and isolation based on analytical redundancy that provides residuals with well-defined thresholds. The control is reconfigured in case of faulty current measurement and operation continuity is performed using the remaining two healthy sensors. The main interest of using FPGAs to implement such controllers is the very important reduction of execution time delay in spite of algorithm complexity. As a result, a high sampling frequency can be used and the residual thresholds can be accurately defined even for the experimental set-up. Numerous experimental results are given to illustrate the efficiency of FPGA-based solutions to achieve efficient and reliable fault-tolerant hysteresis current control of AC machine drives.

Current sensor with calibration for a current divider configuration

Abstract: An integrated circuit (IC) current sensor that self-calibrates to adjust its signal gain when employed in a current divider configuration is presented. The current sensor includes an integrated current conductor, a magnetic field transducer, a controllable gain stage and a calibration controller. The integrated current conductor is adapted to receive a portion of a calibration current. The calibration current corresponds to a full scale current. The magnetic field transducer, responsive to the calibration current portion, provides a magnetic field signal having a magnitude proportional to a magnetic field generated by the calibration current portion. The controllable gain stage is configured to amplify the magnetic field signal with an adjustable gain to provide an amplified magnetic field signal. The calibration controller is responsive to a calibration command signal to adjust the adjustable gain of the controllable gain stage to a calibrated gain in order to provide the amplified magnetic field signal at a predetermined voltage level that corresponds to a desired current sensor output signal voltage level if the full scale current were received by the integrated current conductor.

Single-sensor multi-channel maximum power point tracking controller for photovoltaic solar systems

Abstract: This study presents a maximum power point tracking (MPPT) method and controller for a multi-channel ( N -channel) photovoltaic solar system. The N -channel single-sensor MPPT (SS-MPPT) controller is able to track the maximum power point (MPP) of each solar panel using only one output current sensor in the N -channels. Compared with a conventional N -channel MPPT system which requires N voltage sensors, N current sensors, 2 N analogue-to-digital converters (ADCs) (or an ADC with 2 N channels) and N -MPPT controllers along with the associated conditioning circuitries, the proposed method only requires one sensor, one ADC and one MPPT controller. In the proposed N -channel SS-MPPT controller, the MPPT for each channel is achieved by tracking the maxima of the output (load) current (resulting in the maxima of the system output power) using the Perturb and Observe algorithm and the maxima of each channel power via channel output current difference optimisation. Two algorithms which can be used to realise the SS-MPPT controller are discussed and compared. The concept and operation of the SS-MPPT controller is presented, analysed and verified by results obtained from a proof-of-concept experimental prototype.

Multiple channel light source power supply with output protection

Abstract: Multiple output channel light source power supply circuits, and methods for protecting, are provided. A front end circuit receives an input voltage and provides a regulated front end DC voltage (FEDC). Voltage converter circuits (VCCs) receive the FEDC and provide a separate associated DC output for each associated output channel. A protection switch is coupled between. In its conducting state, the FEDC is coupled to the VCCs. In its non-conducting state, the FEDC is decoupled. A current sense circuit of a current sensor in parallel with a bypass switch is coupled to the VCCs to provide a current sense output representing current through at least one VCC. A controller circuit places the protection switch in the non-conducting state in response to the current sense output. The bypass switch may be placed in a conducting state to shunt current around the current sensor during normal operation to reduce or eliminate inefficiency.

A new approach for current sensor fault diagnosis in PMSG drives for wind energy conversion systems

Abstract: Fault diagnosis is a mandatory feature in fault tolerant systems, since it provides the information necessary for the fault isolation and system reconfiguration. Recently, permanent magnet synchronous generator (PMSG) drives have achieved prominence in wind energy conversion systems (WECS), due to their reliability and availability. Therefore, in this paper a new approach is proposed for current sensor fault diagnosis in PMSG drives for WECS. As opposed to the conventional state observer-based methods for current sensor faults, which require a system model and the respective parameters, the proposed diagnostic method uses the measured phase currents only. Thus, its main merits are simplicity and reliability in the diagnosis, making it suitable for real-time implementation and to trigger remedial procedures. Additionally, current sensor and open-circuit faults can be distinguished and the affected phase is effectively identified in both cases. The proposed diagnostic technique is applied to the two power converters of a conventional back-to-back topology, and its performance is analyzed by means of several experimental results.

Current reference generating circuit and a constant current switch mode power supply control circuit and method thereof

Abstract: A current reference generating circuit including a first multiplier module, configured to receive a rectified voltage waveform signal of a switch mode power supply and an output signal generated by an average current loop, and to generate a sinusoidal half-wave signal having the same frequency and phase as the rectified voltage waveform signal, the sinusoidal half-wave signal varies with the output signal generated by the average current loop. A second multiplier module, configured to receive the sinusoidal half-wave signal and a control signal to generate a pulse signal. An average current loop for comparing the average of the pulse signal to a predetermined average current loop reference signal. The circuit can generate a self-adapted reference signal that follows the primary-side current signal of main circuit of the switch mode power supply, which is then supplied to the constant current switch mode power supply control circuit with high power factor.

Sensor Fault detection and fault tolerant control of induction motor drivers for electric vehicles

Abstract: An effective fault detection and fault tolerant control strategy in induction motor is described in this paper. Based on the algorithm of posterior reliability voting, the proposed approach could detect the healthy state of encoder, and adjust the weights between the speed from encoder and estimated speed based on MRAS. When redundant current sensors are installed in the controller, a logic decision scheme could detect and shield the faulty one, and guarantee that the current signals involved in the control are from the two healthy current sensors. Abrupt faults of both encoder and speed sensor are simulated in the induction motor driver individually, and simulation results in terms of speed response indicate the effectiveness of the proposed strategy subject to faulty conditions caused by encoder or current sensor.

Design of a PCB Rogowski Coil based on the PEEC Method

Abstract: In order to measure currents with high di/dt, Rogowski coils are usually used. This work studies the design of a PCB coil by means of electromagnetic field simulation. The PEEC method has been used to extract the parameters of the equivalent circuit of the coil geometry. Different winding arrangements were analyzed with respect to measurement signal strength and noise immunity. The magnetic coupling between the current sensor and the busbar is investigated for the used test setup. Finally, a comparison of the PEEC simulation results with measurements, applying a 400 A current pulse concludes this paper. The results show that the PEEC method allows a simulation of the coil including the setup in which it is used with a reasonable computational effort.

Electrical Characterization of a Magnetic Tunnel Junction Current Sensor for Industrial Applications

Abstract: The objective of the work was the design of a Wheatstone bridge current sensor using MTJ as magnetoresistive elements. Each one of the four resistances of the bridge consists on 360 MTJ single elements connected in series for improved electrical robustness. A printed circuit board (PCB) was designed with a U-shaped copper trace placed under the PCB maintaining a 1.1 mm separation distance between sensor and trace. A 160% of tunnel magnetoresistance effect in the single junction and a 120% in its corresponding series elements connection has been achieved with a sensitivity of 9.2 Ω/Oe in a 65 Oe linear range. The DC sensor sensitivity in response to an external DC current sweeps of ±10, ±20, and ±30 A gave an average of 9.8 mV/A. The measured AC sensor response in all the tested cases corresponded to a - 3 dB frequency close to 200 kHz. The sensor was submitted to a DC current excursion under different temperatures showing a TC(S) sensitivity temperature coefficient of 0.031%/° C rather lower compared with the spin-valve technology. The work shows that MTJ sensor technology provides a promising tool in the R+D areas of power management and energy consumption like electric vehicles or energy metering.

Electricity supply system of wind and light commercial power complementary communication base station

Abstract: The invention discloses an electricity supply system of a wind and light commercial power complementary communication base station, which consists of commercial power an oil engine, alternating-current distribution, a switch power supply, a switch power supply controller, a switch power supply detection current sensor, a wind and light complementary output current sensor, a storage battery, direct-current distribution, an alternating-current load, a communication load, a solar battery, a wind power generator, a wind and light complementary controller, a storage battery current sensor, a storage battery temperature sensor and a load current sensor The invention uses wind energy and solar energy as preferable power supply energy sources, the commercial power is used as the supplementation,the power supply reliability of the system is ensured, and the wind and light commercial power complementary control is in self-adaptive regulation and is in smooth transition