Distortion improvement in the current coil of loudspeakers

International audienceThis paper deals with the comparison of voltage and current driving units in an active audio system. The effect of the audio amplifier control on the current coil of an electrodynamic loudspeaker is presented. In voltage control topology, the electromagnetic force linked to coil current is controlled through the load impedance. Thus, the electromechanical conversion linearity is decreased by the impedance variation, which implies a reduction of the overall audio quality. A current driving method could reduce the effect of the non-linear impedance by controlling the coil current directly, thereby the acceleration. Large signal impedance modeling is given in this paper to underline the non-linear effects of electrodynamic loudspeaker parameters on the coupling. As a result, the practical comparison of voltage and current driven methods proves that the current control reduces the voice coil current distortions in the three different loudspeakers under test

Behavioral model of gallium nitride normally ON power HEMT dedicated to inverter simulation and test of driving strategies

International audienceIn this paper, the authors present a behavioral model of a GaN normally ON HEMT. Forward and reverse conductions are modelized. The modelling of both conduction modes is required to provide accurate diode-less synchronous switching-cell simulation. A dedicated transistor capacitance extraction procedure based on an analysis of turn-on and turn-off waveforms is also proposed and experimented