Speaker excursion protection

Abstract

An audio circuit includes an amplifier, a voltage sensor, a current sensor, and an excursion control circuit. The voltage sensor is coupled to an output of the amplifier. The current sensor is coupled to the output of the amplifier. The excursion control circuit is coupled to the amplifier, the voltage sensor, and the current sensor. The excursion control circuit includes back electro-magnetic force (EMF) measurement, a back-EMF model, and excursion protection. The back-EMF measurement is to measure back electro-magnetic force of a speaker based on voltage measurements received from the voltage sensor and current measurements received from the current sensor. The back-EMF model is updated based on measurements of the back-EMF and is converted to an excursion model. The excursion protection is to limit amplitude of audio signal provided to the amplifier based on the excursion model of the speaker and amplitude of an audio input signal.

What is claimed is: 
     
         1 . An audio circuit, comprising:
 a speaker housing, comprising:
 a speaker; and 
 a passive radiator or a bass reflex port; 
   an amplifier coupled to the speaker;   a voltage sensor coupled to the speaker;   a current sensor coupled to the speaker;   an excursion control circuit coupled to the amplifier, the voltage sensor, and the current sensor, the excursion control circuit comprising:
 back electro-magnetic force (EMF) measurement to measure back electro-magnetic force of the speaker based on voltage measurements received from the voltage sensor and current measurements received from the current sensor; 
 a back-EMF model that is updated based on measurements of the back-EMF and is converted to an excursion model; and 
 excursion protection to limit amplitude of audio signal provided to the amplifier based on the excursion model of the speaker and amplitude of an audio input signal. 
   
     
     
         2 . The audio circuit of  claim 1 , wherein the back-EMF model comprises:
 a second order filter to model back-EMF of the speaker;   a fourth order filter to model back-EMF of the speaker with the passive radiator or the port.   
     
     
         3 . The audio circuit of  claim 2 , wherein the second order filter is updated based on the measurements of the back-EMF; and the fourth order filter is updated based on output of the second order filter. 
     
     
         4 . The audio circuit of  claim 1 , further comprising back-EMF model to excursion model conversion to convert amplitude of the audio input signal to a value of speaker excursion. 
     
     
         5 . The audio circuit of  claim 4 , wherein the excursion protection is to estimate speaker excursion based on the amplitude of the audio input signal provided to the audio circuit and the excursion model provided by the back-EMF model to excursion model conversion. 
     
     
         6 . The audio circuit of  claim 1 , wherein the excursion protection is to apply a gain attenuation to a delayed version of the audio input signal based on the speaker excursion exceeding a predetermined threshold. 
     
     
         7 . An audio circuit, comprising:
 an amplifier;   a voltage sensor coupled to an output of the amplifier;   a current sensor coupled to the output of the amplifier;   an excursion control circuit coupled to the amplifier, the voltage sensor, and the current sensor, the excursion control circuit comprising:
 back electro-magnetic force (EMF) measurement to measure back electro-magnetic force of a speaker based on voltage measurements received from the voltage sensor and current measurements received from the current sensor; 
 a back-EMF model that is updated based on measurements of the back-EMF and is converted to an excursion model; and 
 excursion protection to limit amplitude of audio signal provided to the amplifier based on the excursion model of the speaker and amplitude of an audio input signal. 
   
     
     
         8 . The audio circuit of  claim 7 , wherein the speaker back-EMF model comprises:
 a second order filter to model back-EMF of the speaker;   a fourth order filter to model back-EMF of the speaker with a passive radiator or a bass reflex port.   
     
     
         9 . The audio circuit of  claim 8 , wherein the second order filter is updated based on the measurements of the back-EMF; and the fourth order filter is updated based on output of the second order filter. 
     
     
         10 . The audio circuit of  claim 7 , further comprising back-EMF model to excursion model conversion to convert amplitude of an audio input signal to a value of speaker excursion. 
     
     
         11 . The audio circuit of  claim 10 , wherein the excursion protection is to estimate speaker excursion based on the amplitude of the audio input signal provided to the audio circuit and the excursion model provided by the back-EMF model to excursion model conversion. 
     
     
         12 . An audio circuit, comprising:
 an amplifier;   a voltage sensor coupled to the amplifier;   a current sensor coupled to the amplifier;   an excursion control circuit comprising:
 a back electro-magnetic force (EMF) measurement circuit coupled to the voltage sensor and the current sensor; 
 a second order back EMF filter coupled to the back-EMF measurement circuit; 
 a fourth order back EMF filter coupled to the second order back EMF filter; 
 a port detection circuit coupled to the voltage sensor, the current sensor, and the second order filter; 
 a back-EMF model to excursion model conversion circuit coupled to the second order back EMF filter and the fourth order back EMF filter; and 
 an excursion protection circuit coupled to the back-EMF model to excursion model conversion circuit, an audio input, and the amplifier. 
   
     
     
         13 . The audio circuit of  claim 12 , further comprising a switch coupled to the current sensor, the fourth order back EMF filter, the port detection circuit, and the second order back EMF filter. 
     
     
         14 . The audio circuit of  claim 12 , wherein the excursion protection circuit comprises a switch coupled to the port detection circuit, the back-EMF to excursion conversion circuit, and the audio input. 
     
     
         15 . The audio circuit of  claim 13 , wherein the excursion protection circuit comprises:
 a limiter circuit coupled to the switch and the amplifier; and   a delay circuit coupled to the audio input and the amplifier.