In the case of mains-powered devices such as computer power supplies, it is necessary to regulate the current draw from the supply mains. This is done by means of power factor correction (PFC). The Problem: Significant reactive and distortion power or spurious emissions can occur, which interfere with devices in the vicinity such as radios or routers. Usually these spurious emissions are limited by passive filters and shielding enclosures, but these are expensive and heavy.
A German university developed a method where spurious emissions are selectively reduced by modulated counter-interference signals. A counter-interference synthesizer generates the counter-interference signal from synthesized and modulated sinusoidal signals whose amplitude and phase are calculated using the Fourier transform. The changing duty cycle of the PFC is also taken into account. The counter-interference signal is coupled into the overall system via an injector. Depending on the method and algorithm, a digital signal processing hardware, e.g. an FPGA, DSP, microcontroller or specially designed ASICs, can predict the electromagnetic interference and control the counter-interference synthesizer in an optimized way accordingly.
The German university offers interested companies the opportunity to license and continue to develop this technology with the inventors within a technical cooperatioon agreement. This invention should particularly interest electronics manufacturers of chargers for various devices who coulöd then use the technology in their systems.