Layout study of contactless magnetoresistor current sensor for high frequency converters

The magnetic object localization is widely utilized in sea mine detection, identification of vehicles and unexploded ordnance. And the Anisotropic Magneto-resistive (AMR) sensor is applied in compassing, navigation systems, and magnetometer. Thus, a novel magnetic object localization method based on AMR sensor is presented in this paper. Firstly magnetic object localization theoretical model is established, and magnetic field and magnetic gradient need to be measured for localization. And then detection and localization hardware construction is designed and realized. The weak magnetic field detection method and measurement modules are discussed. At last, the lab test based on AMR sensor is carried out. The results show that it is an effective method for magnetic object localization and when the magnet of surface magnetic field is 0.9T, the location error is not more than 10% from 50cm to 140cm. AMR sensor is a valuable choice for magnetic object localization measurement.

As wide bandgap (WBG) semiconductors are gradually adopted for high switching frequency high power-density power converter, new challenges arise from control to hardware design. In this paper, an improved input current sampling method is proposed for three-phase rectifiers to avoid sampling noises when rectifiers are operated at high speed and high switching frequency. Experimental results obtained from a 450-kHz enhancement-mode Gallium Nitride (GaN) high-electron-mobility transistor (HEMT) based three-phase three-level Vienna-type rectifier demonstrate the good performance of the sampling method.

A conventional unregulated fuel cell system requires a multi-stage operation in order to get three phase AC power supply for integration with load or grid. The output of fuel cell which is DC has to be converted into high frequency AC which has low efficiency due to high switching losses. In this paper high frequency power is regulated with the help of cascade connection of the series resonant converter and single phase to three phase cycloconverter. A series resonant converter decreases the switching loss because of zero current switching whereas a single phase to three phase cycloconverter converts the single phase high frequency output into low frequency three phase output required by grid. The proposed high frequency converter has high conversion efficiency and low cost. It is compact due to reduction of number of stages and eliminates intermediate filter. Analysis and simulation are presented for complete converter system using Matlab software and it has been demonstrated that the system is highly efficient with simple controller and higher power density.

Ta/MgO/NiFe/MgO/Ta anisotropic magnetoresistive thin film sensors, which can be used for magnetic scales, were prepared. To improve the magnetoresistance ratio of the sensors, these sensors were vacuum-annealed with the magnetic field applied, and then, both the static and dynamic magnetoresistive responses of the sensors were obtained. The experimental results have shown that the instability of magnetic anisotropy occurs in the sensors after vacuum-annealing, leading to the significant hysteresis and abnormal output voltage peaks. To investigate the underlying physics, the distribution of the non-uniform demagnetizing field along the width of an anisotropic magnetoresistive (AMR) strip is considered, and both the static and dynamic responses of the AMR elements have been calculated on the basis of the Stoner–Wohlfarth model. The results have shown that the calculated results are in good agreement with the experimental data. The calculated results have revealed that the angles between the anisotropic field and the external magnetic field are different during the field cyclings of Hmax (maximum magnetic field) to −Hmax and −Hmax to Hmax. The angle difference is up to 6°, leading to different magnetoresistive responses. This paper is helpful for the understanding about the magnetization rotations in magnetic sensors and the manufacturing of sensors.

We report the detection of nuclear magnetic resonance (NMR) using an anisotropic magnetoresistive (AMR) sensor. A "remote-detection" arrangement was used in which protons in flowing water were prepolarized in the field of a superconducting NMR magnet, adiabatically inverted, and subsequently detected with an AMR sensor situated downstream from the magnet and the adiabatic inverter. AMR sensing is well suited for NMR detection in microfluidic "lab-on-a-chip" applications because the sensors are small, typically on the order of 10 mum. An estimate of the sensitivity for an optimized system indicates that approximately 6 x 10(13) protons in a volume of 1,000 mum(3), prepolarized in a 10-kG magnetic field, can be detected with a signal-to-noise ratio of 3 in a 1-Hz bandwidth. This level of sensitivity is competitive with that demonstrated by microcoils in superconducting magnets and with the projected sensitivity of microfabricated atomic magnetometers.

A magnetoelectrical resistivity measurement system is proposed, which combines measurement of the electric potential and the magnetic field due to a current injection into a sample. Measurement of the electric potential, as well as the injected current, is similar to traditional electrical resistivity tomography (ERT) data acquisition. For the magnetic field measurements, 24 sensor modules have been developed using three component anisotropic magnetoresistive (AMR) sensors, mounted on a vertically moving scanning torus. The system is designed to operate in a typical laboratory magnetic noise environment without extensive shielding. To compensate for the effects of the Earth's magnetic field, the AMR sensors are operated with a field feedback circuit. Optimal noise reduction is provided by the use of a lock-in frequency of 25 Hz, with sine wave modulation and measurement cycles of 10 s. The resolution of the system is better then 50 pT and the aimed accuracy is 0.1%. The system provides a data set of magnetic fields complimentary to traditional ERT to determine the internal conductivity distribution of cylindrical samples with the dimension of 0.1-m radius and 0.5-m height.

The higher switching frequency in combination with di/dt loops and dv/dt nodes in the power stages of high frequency power converters generates higher order harmonics which cause Electro Magnetic Interference (EMI). It is commonly perceived that high frequency converters are more vulnerable to radiated EMI, thus, it is very important to analyze the radiated emission of these converters. According to the author's knowledge, the analysis of the radiated emission of power converters switching in the MHz frequency region has not been presented until now. Therefore, in this paper, the measurements, and analysis of the near field radiated emissions of these emerging power converters is presented. These measurements are beneficial in the early design stage of power converters. Both E-field and H-field and captured and analyzed for a half bridge converter switching at 3 MHz and at the output power level of 25 W. The effects of the magnetic and electric field emissions with the addition of a Y-capacitor and secondary side common mode choke are analyzed.

Development, fabrication, and test of a modular eddy current micro sensor on a flexible polymer foil

This paper discusses optimal configuring and commissioning of laboratory system that consists of FC-302 high performance frequency converter and induction motor. In the beginning frequency converter control of induction motor is explained. Furthermore, the measurements of slip compensation parameter change influence on motor speed and motor load dependence are performed, as well as measurements of power factor correction attained by frequency converter. It is possible to compensate slip completely, so that motor speed is constant, regardless of motor load, which provides optimal control. Frequency converter partially compensates power factor of converter - motor system with capacitors of passive filter.

A new construction of magnetometer with commercially available AMR (anisotropic magnetoresistive) sensors intended for vehicle detection experiments is presented. Initial experiments with simple AMR gradiometer indicated viability of the approach in a real- world setup. For further experiments and acquisition of representative data, a new design of precise multi-channel magnetometer was developed. The design supports two models of commercial AMR sensors: the proven and reliable, but obsolete Honeywell HMC1021-series sensors and newly available Sensitec AFF755B sensors. In the comparison the two types are similar in most achieved parameters, except offset stability in flipped operation regime. Unfortunately, the new AFF755B sensors seem to have perhaps inferior coupling of the flipping (set/reset) coil to the ferromagnetic core that causes insufficient saturation of the AMR material. The issue is being solved by Sensitec, current deliverables of the AFF755B have “product sample” status (September 2015).

In the last decade, wireless sensor networks (WSN) have gained considerable importance and momentum. They are used with a growing diversity of sensors in a plethora of applications, e.g., from Ambient Intelligence (AmI), Assisted Living (AAL) to agriculture. WSN based measurement and instrumentation systems commonly have to operate under tight power consumption constraints. In particular, WSN benefiting from micro-electro-mechanical-system (MEMS) miniaturization have a very limited power budget due to poor energy density of storage elements. While highly optimized microcontrollers are available by now, today's sensors and sensor electronics are the predominant cause of power consumption in WSN. The standard approach tries to minimize standby currents by low-power sensor, bridge, and amplifier design. In contrast, this paper investigates an approach of duty-cycled, reconfigurable sensor electronics for resistive bridge sensors, that seamlessly integrates into microcontroller' sleep modes. The circuit is optimized for the particular case of anisotropic magneto-resistive (AMR) sensor based localization in autonomous WSN. In a systematic analysis amplifier currents, slew-rate, and read-out or on-time T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> are optimized for minimum power consumption of a tri-axial AMR sensor. At the required read-out rates, e.g., one measurement per minute, energy consumption can be reduced to a factor 1.5·10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> of the continuous operation. A reconfigurable chip in a standard 0.35 μm bulk CMOS technology is under preparation adding flexibility for different sensor types and calibration needs.

Reciprocating compressor is the most important gas transportation equipment and the most important energy consumption equipment in the CBM gathering and transportation system. The existing variable clearance volume energy saving adjustment method of reciprocating compressor has the characteristics of complex operation and poor timeliness in operation. By carrying out risk identification, developing test scheme and determining control parameters, we successfully completed power frequency high speed reciprocating compressor variable frequency test. The theoretical analysis and practical operation results show that the application of high voltage frequency converter in speed control of reciprocating compressor with high frequency is feasible. The actual controllable frequency modulation range of the reciprocating compressor motor with high frequency and high speed is 34Hz to 55Hz, the resonant frequency of compressor and main motor is 51.5Hz, and the effective energy-saving frequency regulation range is 34Hz to 45Hz. The low frequency operation has better energy saving effect, the unit consumption of gas transportation is reduced by about 3%. It can effectively improve the operation efficiency of the compressor and reduce the unit consumption of gas transportation by reasonably controlling the power frequency motor of the reciprocating compressor by the frequency converter.

Press-pack power module gradually replaces traditional power module in high power applications such as High Voltage Direct Current and Flexible AC Transmission Systems. There are many semiconductor chips connected in parallel inside press-pack power module. The uneven distribution of clamping force and temperature will cause the imbalance current distribution of semiconductor chips, which may lead to the overcurrent of some chips. Since press-pack power module is usually used in high power converters, online current monitoring should be applied to provide fault diagnosis. However, the accurate chip-level current sensing inside press-pack power module is difficult due to the size and bandwidth of sensors. To solve this problem, a compact hybrid current sensor for chip-level online sensing, which consists of anisotropic magnetoresistance (AMR) and compact planar Rogowski coil is proposed in this paper. AMR sensor is used to sense low-frequency and DC current, and the high-frequency part is measured by Rogowski coil. The parameters of current signal processing circuit are designed by calculation and simulation. The hybrid sensor senses the current of a single-chip press-pack IGBT in buck converter and verified by a commercial current probe.

This paper describes a Very High Frequency (VHF) converter made with three Class-E inverters and a single Class-DE rectifier. The converter is designed for the US mains (120 V, 60 Hz) and can deliver 9 W to a 60 V LED. The converter has a switching frequency of 37 MHz and achieves an efficiency of 89.4%. With VHF converters the power density can be improved and the converter described in this paper has a power density of 2.14 W/cm3. The power factor (PF) requrements of mains connected equepment is fulfilled with a power factor of 0.96.

This paper focuses on the electromagnetic compatibility (EMC) performance of a Very High Frequency (VHF) converter and how to lower the emissions. To test the EMC performance a VHF converter is implemented with a Class-E inverter and a Class-DE rectifier. The converter is designed to deliver 3 W to a 60 V LED, it has a switching frequency of 37 MHz and achieves an efficiency of 80%. For an LED driver to be used on the consumer market it has to fulfil the standard regarding EMC emissions. The conducted emission is often used as a reason to increase the switching frequency to the VHF range to avoid the regulations. This converter shows to be well below the levels for conducted emission even without filtering. For the radiated emissions the converter is above the limits without input and output filters. Several designs with different ways to lower the emissions are implemented and the different layouts and filtering are compared and discussed.