Shahriar Jalal Nibir

Development of current measurement techniques for high frequency power converters

Current sensing plays dominant role in power converters, where current information can be used for controlling, monitoring and protection. One of the most challenging goals in modern power electronics converters is to increase switching frequency for the purpose of miniaturization, and improve the performance especially for end-users. Therefore, the need for accurate, lossless, and fast response current sensors is more highlighted. This paper presents a comprehensive review of different current sensing schemes for power electronics applications. The Challenges for implementation of conventional methods for high frequency (>1MHz) and high current converters will be addressed. More specifically, technical issue and hardware difficulties for developing Rogowski-based as well as Hall effect current sensors are discussed and finally, a new technique for improving the performance of Anisotropic Magneto-Resistive (AMR) at 1MHz and 30V with a new technique is shown.

Layout study of contactless magnetoresistor current sensor for high frequency converters

In this paper, we present a new technique to unify and intensify the magnetic fields that results in higher performance of Anisotropic Magneto-Resistive (AMR) current sensors and consequently develop a closed loop controller for 100W synchronous GaN buck converter at 1MHz. The closed loop operation of high switching frequency converters at high power has always been a big challenge due to lack of access to current information. The proposed method that also intensifies the magnetic fields through the sensor, significantly improves the bandwidth limits, and reduces electromagnetic interference (EMI) on AMR sensors, making them applicable for high switching frequency and high current power electronics converters. After verifying uniform distribution concept through simulation, we also implemented a prototype of AMR current sensors onto Printed Circuit Board (PCB) for verification of the concept at high frequency converter. We then present the design procedure and associated challenges of an integrated analogue peak current controller for creating the closed loop operation of a GaN buck converter at high switching frequency.

A Technique to Enhance the Frequency Bandwidth of Contactless Magnetoresistive Current Sensors

Isolated wideband current measurement is required in many power electronic converters when the switching frequency is above 1 MHz. Typically current passing through a printed circuit board trace induces a highly nonuniform magnetic field which varies as a function of frequency and position relative to the trace. This paper proposes a technique to increase the frequency bandwidth of anisotropic magnetoresistive (AMR) current sensors and simultaneously to intensify and normalize the field detected by the sensor in the frequency range of interest, i.e., DC-5 MHz. We demonstrate experimentally that the proposed technique yields significant enhancement in detection bandwidth of AMR current sensors.

Hybrid Magnetoresistor-Planar Rogowski Current Sensing Scheme With Folded Trace Magnetic Field Concentration Technique

Wideband and isolated current measurement is required in many applications, including power electronics converters, when the switching frequency is above 1 MHz. This paper proposes a hybrid noncontact isolated current sensing scheme consisting of a magnetoresistor-based sensor and a planar Rogowski coil with complementary characteristics. In the proposed current sensing scheme, the folded trace technique is used to improve the magnetic field homogeneity in a wide frequency range, and hence the bandwidth of the sensing scheme. This paper presents the design procedures for the proposed hybrid sensing scheme. We demonstrate through experimentation that the proposed scheme yields a detection bandwidth of dc-10 MHz for 12-A current.

Performance study of magnetic field concentration techniques on magnetoresistor/rogowski contactless current sensor

Magnetoresistor/Rogowski coil can be utilized as a wideband contactless current sensor in power electronic converters. However, the magnetic Field detected by these sensing devices varies with frequency due to skin effect. This paper presents an investigation on two Magnetic field Concentration (MCON) techniques using conductive plates and power trace. These MCONs result in a more uniform magnetic Field seen by the sensing elements over the frequency range of interest. Simulation and experimental results are presented to demonstrate the efficacy of the proposed MCONs and their impacts on performance of the sensors.

Magnetoresistor with Planar Magnetic Concentrator as Wideband Contactless Current Sensor for Power Electronics Applications

High-frequency power electronic converters require lossless, accurate, and isolated current measurement. High-frequency currents through a printed circuit board (PCB) trace generate nonuniform magnetic field around the trace. The nonuniform magnetic fields can be normalized by means of magnetic field concentrators (MCONs) using conductive materials. In this study, a novel technique for high-frequency contactless current sensing using magnetoresistor (MR) sensors with planar magnetic concentrators (MCON) utilizing conductive materials has been proposed. The effect of different MCONs on the performance of anisotropic MR (AMR) sensors for high-frequency contactless current detection has been investigated. The performance of the AMR sensor equipped with different MCONs is demonstrated experimentally with respect to a fast rise step current. A detailed frequency analysis is performed on the sensor response with different MCONs to determine the effect on the detection bandwidth of the current sensors.

Characterization of magnetoresistors for contactless current sensing in power electronic applications

With the introduction of high frequency semiconductor devices and converters, wideband, lossless and accurate current measurement is the key to achieving highly efficient power conversion. Magnetoresistors (MR) provide an alternative solution to isolated and contactless current monitoring in power converters. However, there is few literature on their application for power electronics converters. In this work, detailed characterizations of two different Magnetoresistive (MR) elements, the Anisotropic Magnetoresistor (AMR) and the Giant Magnetoresistor (GMR) are performed for contactless current sensing. The AMR and GMR sensor test circuits are designed and implemented in Printed Circuit Boards (PCB) and their performances are evaluated under different spatial and input current conditions including implementation of different sides of the board and DC, AC and step currents up to 10A. Detailed analysis is performed to analyze the sensitivity and sensing range of the sensors. Finally, a frequency analysis is performed on the step current response to evaluate the detection bandwidth of the AMR and GMR current sensors.

Effect of conductive magnetic field concentrators on the performance of anisotropic magnetoresistors in high frequency contactless current sensing

High frequency power electronic converters require lossless, accurate and isolated current measurement. High frequency currents through a Printed Circuit Board (PCB) trace generates a non-uniform magnetic field around the trace. The non-uniform magnetic fields can be normalized by means of utilizing Magnetic Field Concentrators (MCON) using conductive materials. In this work, the effect of different magnetic field concentrators (MCONs) on the performance of Anisotropic Magnetoresistor (AMR) sensors for high frequency contactless current detection has been investigated. The performance of the AMR sensor equipped with different MCONs is demonstrated experimentally with respect to a fast rise step current. A detailed frequency analysis is performed on the sensor response with different MCONs to determine the effect on the detection bandwidth of the current sensors.