Design of Efficient Sound Systems for Low Voltage Battery Driven Applications

The efficiency of portable battery driven sound systems is crucial as it relates to both the playback time and cost of the system. This paper presents design considerations when designing such systems. This include loudspeaker and amplifier design. Using a low resistance voice coil realized with rectangular wire one can boost the efficiency of the loudspeaker driver and eliminate the need of an additional power supply.

A newly developed switching topology is described which is beneficial to near-idle efficiency (< 2 W), which is crucial for real audio applications in the consumer electronics space. A small sized sound system was implemented using the discussed design considerations. The amplifier efficiency performance was found to be very high with near-idle efficiency reaching a remarkably 88% at 2 W.

The average output SPL was estimated to be up to 90 dB in half spheric anechoic conditions. Measured results are compared with current state-of-art and shows a 14% points efficiency improvement