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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.

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.

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.

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.

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.

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.

In many modern power electronic systems, fast periodically switching semiconductors are utilized for system control and minimizing switching losses. The resulting steep switching waveforms may cause electromagnetic interference (EMI) that is mostly reduced with help of heavy passive filter circuits. One basic idea is to optimize EMC behavior and efficiency of power electronic devices by forming the switching waveforms with regard to steepness, overshoots, ringing and high frequency disturbances. Therefore, optimum control signals have to be found and synthesized. To do so, the nonlinear transmission behavior of semiconductor devices has to be considered. To start with, a basic MOSFET test circuit is regarded in this work. With help of an iterative search algorithm, a control signal is found that fits the MOSFET’s output signal to a desired waveform that optimizes EMI and minimizes switching losses. The capability of this method is shown by simulations and measurements.

Active cancellation of disturbances of power electronic systems is a common method in EMC. 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 many systems, all disturbance modes of all terminals must be suppressed simultaneously. This is no trivial task since the different injectors for the anti-noise can affect each other. Therefore, a cancellation signal for the input terminals can worsen the noise at the output terminals, or vice versa. Additionally, due to mode conversion, common and differential mode can also interfere. In this work, synthesized cancellation signals are utilized that have already shown a very good performance in the suppression of periodic disturbances since complex transfer functions and delay times can be compensated. For the first time, a multi-port canceller is applied that injects synthesized cancellation signals to reduce the noise at four terminals simultaneously. The canceller enables a characterization of the system and an identification of the mutual coupling between the injectors. From this knowledge, the cancellation circuits can be designed purposefully. Furthermore, the mutual coupling can be respected in the calculation of the cancellation signals. A fundamental theory is described for DC/DC converters and applied to a 48 V/12 V converter in a measurement setup for conducted emissions according to the automotive EMC standard CISPR 25. The effectivity of the method is shown by measurements at artificial networks. The power losses of the cancellation system are estimated.

Active gate control of MOSFETs is a common strategy to improve efficiency and/or electromagnetic compatibility (EMC) of power electronic systems. Finding an appropriate control method for specific requirements is no trivial task, and often there is a trade-off between efficiency and EMC. In this paper, a novel method is proposed that utilizes synthesized control signals. With signal synthesis methods, that can be realized affordable in future integrated circuits, signal shapes can be adjusted more or less arbitrarily. Various requirements, e.g. switching waveforms, overall system’s EMC or efficiency, can be aimed at this way. Here, a basic MOSFET circuit is investigated which should generate a specific switching waveform. This waveform shall improve the system’s EMC without significantly affecting the efficiency. The system is developed, characterized and a mathematical approximation is derived that respects the important temperature dependency. In this first demonstration, very low switching frequencies are considered that make the reactive elements of the MOSFET negligible. From the requirements and the system model, a suitable control signal can be derived. Measurement and simulation results show the good performance of the proposed method.

Cancellation of disturbing signals is a common strategy in EMC. In this work, a specialized strategy is developed to cancel the disturbing harmonics of stationary clocked systems. This strategy is refined by an adaptive approach to conveniently find the optimum signals for cancellation. As a special feature of this method, all troublesome effects, like delays or attenuations, can easily be compensated. From a basic theory, two implementation variants are derived: 1) Continuously Adapted Harmonics Cancellation (CAHC) and 2) Previously Adapted Harmonics Cancellation (PAHC). CAHC is implemented on an FPGA-system. The hardware, programming and performance of the utilized FPGA and its peripherals are transparently discussed. The effectivity of the method is demonstrated for a power electronic dc-to-dc converter.