Dissertação de Mestrado
Interface do amplificador classe D com alto-falante: estudo e modelagem. Forma de interação destas unidades para integração em caixas ativas
Fecha
2010-02-09Autor
Claudio Alexandre Pinto Tavares
Institución
Resumen
Most of the sound equipments existent today has for base the transistorized linear amplifiers (class A, B and AB), an established technology that, however, it possesses as characteristic disadvantages the low efficiency in the conversion of the energy, physical size and high costs. The switched amplifiers or class D, that allow the increase of the power density, with great increase in the efficiency, without need of heat transfers and with sensitive reduction of the cost. They approach in sound quality of the linear amplifiers and they overcome them in terms of energy efficiency. The class D amplifiers are still little taken advantage of in the field of the averages power (typically 25W to 250W). In these levels we can use the concept of active loudspeaker, whose power amplifier is placed inside of the acoustic box. Specifically, the use in multichannel systems for Home Theater, car sound, applications for Public Adress, in studios (reference monitors), or small auditoriums and class rooms, where you factor as energy efficiency, reduction of the volume, weight and costs become priority, without damage of the sound quality. On the other hand, the development of the loudspeakers for audio reproduction, stays conditioned to small improvements in the elementary concepts developed at the beginning of last century. The low-pass filter, typically LC, used in the amplifiers to eliminate the carrier of the audio signal, that is usually a PWM (Pulse Width Modulation), it commits the size of the amplifier, your cost and your sound quality directly. This work presents a study of the interface amplifier/loudspeaker, to verify in that conditions are possible the retreat of the filter LC in this scale of power. The operation of the amplifier class D is described, after that we modeled the speaker as a complex load for this amplifier. We accomplished tests with a commercial topology, through the construction of an amplifier prototype and the high several commercial loudsspeakers' use for the study of the interface amplifier/loudspeaker. Being compared the theoretical and practical results for the connection of the amplifier to the loudspeaker with the filter LC and without this, for the several loudspeakers with different characteristics.