Patent ID: 8774419

Claim:
A method for protecting a voice coil in an electro dynamic transducer against a thermal overload, comprising: estimating a temperature of a magnet in the electro dynamic transducer; reducing a power applied to the voice coil when a power of an audio signal exceeds a power limit P lim ; wherein the power limit P lim is approximately determined by the temperature of the magnet and a predetermined voice coil temperature limit; wherein the power limit P lim is proportional to: ( T lim −T m )/ R tv wherein T lim is the predetermined voice coil temperature limit; wherein T m is the temperature of the magnet; wherein R tv is the thermal resistance of a path from the voice coil to the magnet; and wherein when the power limit P lim is equal to or less than zero, no power is applied to the voice coil; wherein when the power limit P lim is a positive number, the power applied to the voice coil is dependent on a value of P lim and the power of the audio signal.