An intelligent amplifier has been developed which delivers output power to either a two or four speaker audio system. The amplifier determines the number of speakers present during the start-up sequence and configures itself either as two BTL amplifiers or four single ended amplifiers. The system does not require any wiring modifications to operate in either mode and will reconfigure itself on each start-up cycle allowing system modifications, such as adding speakers, without additional wiring or hardware modifications.
Difficulties arise when determining the presence of speakers in an automotive environment. Extraneous noise sources such as door slams, hatch slams and engine cranking can cause erroneous measurements thus inappropriate configurations. The presented circuit was determined to be immune to these noise sources and is based upon:
Integration of measurements over a fixed period of time
Applying a large voltage to overcome noise sources without creating audible disturbances