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In various technical areas, the requirements and the complexity of electrically conductive structures (cables, printed circuit board traces) and their insulating materials are increasing, which leads to higher demands on reliability. Therefore, better diagnosis and control functions are needed. Intelligent fusing strategies with electronic fuses, where the current flow can be switched by semiconductors, can play an important role. One approach is to monitor the insulation temperature in order to detect thermal overloads and switch-off a current branch before the insulation is damaged. As especially in cables, a direct temperature measurement is troublesome, most approaches are based on current measurements. From a measured current, the cable insulator temperature can be derived using an electrothermal model. Those models can be very complex, especially when the transient and axial heat flow in a cable should be considered. The computational efforts for the commonly used numerical solution methods are high. Analytical approaches potentially reduce these efforts significantly. In this contribution, a new analytical approach for the calculation of the transient axial temperature distribution along an insulated single wire cable considering the nonlinear temperature dependency of the cable parameters is presented. It enables a precise and fast calculation of cable temperatures.

In this contribution, similarities and differences between electrical and thermal effects on cables are investigated. In the electrical transmission line theory, a wide variety of methods is known to describe the voltage and current along cables. The potential for the adaption of some of those methods to thermal problems is discussed. Exemplarily, for an unshielded single cable, an analytical solution based on the Laplace transform and an approach based on cascaded equivalent circuits are compared with a numerical reference solution and measurement results.

Boost power factor corrections tend to be considerable sources of electromagnetic disturbances. To ensure the proper functionality of susceptible systems in the vicinity, the emissions must be reduced. Passive filters, as a conventional solution to reduce conducted emissions, usually suffer from their high volume, weight and costs. Active filters can help to mitigate this problem, but the known solutions are systematically limited by inherent time constants and signal propagation delays since they derive the cancellation signal directly from a measured quantity by a feedforward and/or feedback approach. To resolve this issue, each harmonic can be individually suppressed by an artificially synthesized sine wave that is synchronized to the disturbances. By adjusting the amplitudes and phases of the suppressing sine waves, bothersome time constants and delay times can be compensated. In this work, it is shown that the switching harmonics of a power factor correction can be interpreted as modulated sine waves. By modulating the suppressing sine waves simultaneously, a very high performance can be achieved for the active cancellation system. The hardware and the algorithm are described, optimum parameters for the algorithm are identified and an FPGA implementation is applied to a real PFC.

Often, electromagnetic interference (EMI) scanning applications require phase and magnitude information for the creation of equivalent radiation models and far-field predictions. Magnitude information can be obtained using a spectrum analyzer (SA), which is relatively inexpensive compared to phase resolving instruments such as vector network analyzers (VNAs) and oscilloscopes at tens of GHz. This paper introduces and optimizes a cost-effective SA-based phase measurement method and compares the results to a VNA and oscilloscope-based methods for EMI signal sources. The measured-phase distribution obtained from the three different instruments is additionally compared with the simulated phase determined from full-wave simulation. The three measurement methods are compared based on the type of signal spectrum to be measured, such as single or multiple frequencies, signals requiring low-resolution bandwidth measurements, or transient signal events. The SA-based phase measurement technique is designed to operate from 5 to 12 GHz. However, the system frequency bandwidth is limited only by the frequency bandwidth of the individual RF components used in the SA measurement system.

Active cancellation of disturbances of power electronic systems is an aspiring method in EMC to reduce passive filter sizes. Most publications on this topic deal with the cancellation of either common- or differential-mode disturbances at either the input or the output terminals. In most practical systems, all disturbance modes of all terminals must be suppressed simultaneously. This is no trivial task since the different injectors for the cancellation signals can affect each other. Therefore, a cancellation signal for the input terminals can worsen the disturbances at the output terminals, or vice versa. Additionally, due to mode conversion, common- and differential-mode EMI can also interfere. In this work, synthesized cancellation signals are utilized that have already shown a promising performance in the suppression of periodic disturbances since complex transfer functions and delay times can easily be compensated. Here, a multi-port canceller is applied that injects synthesized cancellation signals to reduce the disturbances at multiple terminals simultaneously. The fundamental problem of mutually coupled injectors is discussed and a mathematical description is formulated. From this description, the cancellation signals are calculated and requirements for the system are derived. This method is applied to a GaN-based 48 V/12 V DC-to-DC converter with a switching frequency of 1 MHz in a measurement setup for conducted emissions according to the automotive EMC standard CISPR 25. The coupling and decoupling are practically discussed. The effectivity of the method is shown by measurements at artificial networks. The total power of the generated cancellation signals is estimated.

Active EMI cancellation is an interesting solution to reduce the size of passive filter components. In this work, the already established active EMI filter types are summarized. The systematic limitations are elaborated that result from the feedback or feedforward approach for cancellation signal generation. Afterward, a new method is presented in which the cancellation signal is artificially synthesized and injected into the system. This method is especially well suited for the suppression of periodic EMI since the anti-EMI can conveniently be synthesized from cancelling sine waves. Bothersome effects, like complex frequency characteristics or delays, can be compensated by appropriate amplitudes and phases. By doing so, systematic limitations of active EMI filters can be resolved. In this work, the fundamental concept and possible variants are depicted. Although many limitations of active EMI filters are resolved, also the new method has its limits. These are described and discussed. Furthermore, different methods for determining the cancelling sine waves are summarized. Last, a prototype cancellation system is presented and discussed to suppress the EMI of a GaN-based 48 V/12 V DC-to-DC converter with a switching frequency of 300 kHz. The disturbances are actively suppressed below the strictest limit (class 5) of the automotive standard CISPR 25 in the frequency range from 150 kHz to 30 MHz. The active suppression of the cancellation system and the passive attenuation of the coupling circuits are individually investigated to elaborate the performance of the active cancellation strategy. The power of the generated cancellation signal is estimated.

Active cancellation of disturbing signals is a common method in electromagnetic compatibility (EMC) of power electronic systems. In this paper, a new method of suppressing periodic disturbances is extended and applied. In this method, the disturbing harmonics are suppressed by a synthesized cancellation signal that is synchronized with the converter's operation. Here, the cancellation signal is synthesized from a number of destructive sine waves. The appropriate amplitudes and phases are found via a convenient and robust adaptive approach. As a special feature of this method, many troublesome effects, like delays or complex frequency characteristics, can be compensated easily. Therefore, this method does not suffer from the same limitations as previous active techniques. Until now, the method has only been proven for a small number of harmonics. In this study, it is applied to a wide frequency range of 150 kHz to 30 MHz of a 48-/12-V dc/dc converter, e.g., for automotive applications. An optimization strategy is developed from a causal model of the system. A test setup is realized, and the sensor's and injector's performances are discussed regarding the automotive EMC standard CISPR 25. Measurement results for the artificial network and the antenna are presented. The additional power losses are estimated.

The high-frequency switching of power transistors in electronic systems can be a significant source of electromagnetic emissions (EMI). Simple measures like reducing the high-frequency disturbances by introducing an additional gate resistor lead to an increase of the switching losses. This creates a conflict of interests between the reduction of disturbances and high system efficiency. More complex active gate drivers offers improved compromises between EMI and efficiency. Avoiding steep switching slopes, overshoots or sharp edges are typical measures. The whole spectrum is modified this way and efficiency is still affected. In many cases, only a narrow banded modification of the spectrum might be needed to avoid the excitation of critical system resonances. This can be reached by a target signal-oriented control of the gate of the transistors. In the target signal the critical RF components should be reduced. Maximum control of the target signal is possible with fully synthesized gate signals. The reduction of some harmonics in the switching spectrum may lead to overshoots in time domain due to the Gibbs phenomenon. These overshoots may violate the physical limits of a transistor and cannot be realized. In this work, a method is presented to determine the target signal considering all physical limits. The found approach is applied in simulation to the signal of the drain-source voltage of a boost converter to reduce the harmonics in the FM broadcasting range. The gate control signal is determined for this application.

Communication systems with high data rates like CAN FD and Automotive Ethernet are increasingly used in automobiles. New safety-critical driving assistance functions can be realized with the help of these bus systems, but data transmission has to be very reliable. Road vehicles are a challenging electromagnetic environment because of the high density of electric and electronic devices. Power electronic systems can be very close to communication systems. The typical cable type for automotive communication systems is the unshielded twisted wire pair. Common mode disturbances cannot be reduced by this cable type. Due to unavoidable asymmetry in the communication system electromagnetic coupling can also induce critical differential mode voltages. For this reason, the immunity of communication systems to electromagnetic interferences has to be investigated in detail. In this paper, simulation models are presented and validated by measurements to quantify cable coupling to CAN FD and 100BASE-T1 Automotive Ethernet. Both, common and differential mode voltages caused by cable coupling are investigated. Based on measurements and simulations critical influencing parameters on mode conversion are discussed.

In many modern power electronic systems, fast-switching semiconductor devices are used to reduce switching losses. Due to steep switching waveforms and high switching frequencies, significant electromagnetic disturbances can be emitted. In contrast to conventional passive filter components, active cancellation methods are based on the controlled destructive interference between a noise signal and a corresponding anti-noise signal. Adaptive notch filters revealed themselves as a promising active EMI cancellation concept for periodic noise signals. In this work, adaptive notch filters are regarded in context of slowly time-varying periodic noise signals, e.g. pulse-width modulated signals as common in inverters. The corresponding noise signals consist of switching harmonics and adjacent sideband harmonics. Therefore, the notch filter’s bandwidth comes into focus and an analytical approximation for the ideal adaptive notch filter’s bandwidth is discussed. With help of this approximation, the adaptive notch filter can be parametrized specifically to a given noise spectrum and other requirements. The capability of the parametrization strategy and the adaptive notch filter itself are shown by simulation and measurement.

The evaluation of near-field data can be an effective way to analyze EMI sources. In contrast to antenna measurements, near-field techniques can determine the emitted field without special requirements on the measurement environment. Moreover, critical sources can be found when current distributions can be identified. Therefore, current reconstruction methods for PCB traces were developed. With additional voltage information the termination impedances of the traces can be found. The known phase-less approaches suffers from different limitations, e.g., non-unique reconstruction results. In this paper, the necessary conditions for a unique reconstruction are discussed by investigating simulated phase-less near-field data. Based on these findings, measured near-field data of a PCB trace is evaluated, and the successful retrieval of the phase information is shown. Additionally, reconstructed voltage distributions are presented and compared to measurement data.

Active cancellation of disturbing signals is a common method in EMC. In this paper, a specialized strategy is presented to minimize the disturbing harmonics of stationary clocked systems by injecting an appropriate harmonic cancellation signal with an adjustable signal synthesizer. The optimum cancellation signal is found via a convenient and robust adaptive approach. Each destructive harmonic is generated individually, and the cancelation signal is the superposition of a set of sinusoidal signals. As a special feature of this method, many troublesome effects, like delays or complex frequency characteristics, can be compensated easily. Several implementation variants can be derived from this general approach. Here, the variant, continuously adapted harmonics cancellation (CAHC), is considered. The system's limitations due to the ADC, the DAC, and the synchronization are described. An FPGA-implementation of CAHC is presented and applied to a dc/dc converter in an automotive component measurement setup to demonstrate the effectivity of the method.

This paper deals with the application of spread spectrum techniques on power electronic converters to reduce electromagnetic disturbances. These techniques aim for a spreading of the harmonics in a frequency domain in order to distribute the power over a wider frequency range. By doing so, the levels of the harmonics drop. In this paper, both peak and average detector measurements are considered. It is shown that different parameters are required to minimize either peak or average emissions. The reduction of peak and/or average emissions is mathematically described for a sine wave as a harmonic of pulse width modulation signals. These spread harmonics overlap for high orders and/or high-frequency variations. It is shown that this effect is a limiting factor for spread spectrum in practical applications. The resulting maximum achievable reduction is analyzed. From these results, parametrization strategies are derived to fulfill specific requirements. In test setups, the precision of the proposed parametrization strategies is demonstrated. Additionally, it is shown that the results for peak measurements can also be applied to quasi-peak measurements.

Localization of EMI sources can be a challenging task. The next step is often to identify the parameters of the EMI generating structure and find appropriate suppression. In this work, a method is presented to handle such problems by using only a phase-less scan of the electromagnetic near-field. Here, radiating conductor systems are investigated, like traces on a PCB. Using the electric and/or magnetic near-field distribution, the radiating current distribution can be reconstructed. In this paper an approach based on a known trace geometry and electric as well as magnetic field data is presented. When current distribution is known, critical EMI sources can be found. Furthermore, an approach is presented to design virtually a filter concept for a critical EMI source. For demonstration, based on measurement data, an exemplary conductor structure is investigated. It is pointed out that high currents and high local fields do not necessarily lead to a high far-field. For the exemplary conductor structure, critical sources are identified, and it is shown how the needed filter structures can be found.

Immunity failures of safety-critical automotive sensors can often be linked to strong resonances. In traditional approaches to combat the resonance, it is either shifted to other frequencies or attenuated. In this paper, a third way is shown. Every resonance is associated with an eigenmode of the system. If externally excited, the mode may resonate with a certain amplitude. This amplitude is a function of the projection of the system’s excitation onto the spatial distribution of the mode.With the help of a 3D sensitivity analysis, we identify potential geometric parameters that lead either to a reduced excitation of the eigenmode or that lower the impact of the eigenmodes on the target signal.Applying this method to an automotive pressure sensor a significant reduction of the resonance amplitude by a small modification in the sensor layout is achieved.

The automotive wiring harness poses a challenging electromagnetic environment with its extension and small distances between wires. The introduction of high voltage applications and Wide-Band-Gap (WBG) semiconductors in power electronic systems leads to steeper slopes of control signals, e.g. PWM signals. These signals can cause serious coupling to communication wires and reduce the bitrate. As the safety and reliability of communication are essential requirements of new technologies like autonomous driving, immunity of communication systems has to be investigated. This paper shows a theoretical analysis on the impact of recurring disturbances on communication performance caused by wire coupling. To reduce the impact of disturbance, cooperative operating strategies of the power electronic system and the communication system are proposed to avoid serious delays or bitrate reductions. The presented cooperative operating strategy is an adapted access method based on available time-triggered concepts.

In this paper, model-based approaches to control smart power-switches in vehicles are presented and discussed. The proposed methods use thermal cable models as well as the load characteristics to provide not only a cable protection with different switching strategies but also diagnosis functions such as virtual monitoring of thermal aging and dynamic load limits. Those can be implemented on microcontrollers in different levels of complexity depending on the needed accuracy and calculation speed.

Active cancellation can suppress electromagnetic interference (EMI) of clocked systems like power electronic converters. Considering clocked systems that operate stationary over a sufficient time, there are stable harmonics that can be individually suppressed by destructive sine waves. These sine waves can be superposed to create a synthesized wide bandwidth cancellation signal. Adaptive approaches have proven to be very effective to find the right parameters for each sine wave. Bothersome effects, like complex frequency characteristics or delays, can be compensated by appropriate amplitudes and phases. Therefore, this method does not suffer from the same limitations as active techniques with feedback- or feedforward-topologies. If the disturbances are constant over a sufficient time, the parameters for the cancelling sine waves can be found simultaneously or successively. Until now, only the first option has been shown with an adaptive cancelling FPGA system. Since the cancelling logic needed to be implemented for each cancelling sine wave and the resources of any FPGA are limited, the number of suppressible harmonics was limited as well. In this work, this limitation is resolved by a successive approach that enables the application of the method to a very large number of harmonics. The fundamental theory is discussed, and a robust algorithm is presented. A cancellation system is realized and applied to a 48V/12V DC/DC converter (e.g. for automotive applications) to suppress the frequency range of 150 kHz to 30 MHz in regard to the automotive EMC standard CISPR 25.

Automotive sensors need to fulfill severe electro-magnetic compatibility (EMC) requirements. The space available for EMC solutions based on discrete filter elements is limited. Furthermore, direct voltage or current measurements for analysis purposes are difficult. Innovative simulation methods are therefore needed to further understand and develop non-conventional EMC solutions. In this paper an analysis method to extract the dominant coupling path within sensors and to generate minimized electrical equivalent circuits (EEC) using network based sensitivity analysis is presented. In addition, a computational method that indicates the hotspots causing the EMC immunity failures with high resolution is introduced. Consequently, potential geometric and layout optimizations are derived easily. Failures due to small asymmetries are finally analyzed and optimized using an automotive pressure sensor.