Patent ID: 9729951
Date: 2017-08-08
CPC Classifications: H04R

Claim:
1. A loudspeaker overload protection circuit that protects a loudspeaker connected to a signal source, the circuit comprises: a compressor that is connected between a signal source and the loudspeaker, the compressor having a first input for receiving an input audio signal, a second input that receives a signal representing an estimated loudspeaker power consumption, a third input that receives a signal representing the nominal power of the loudspeaker, and applies a gain to the input audio signal and provides an output audio signal indicative thereof; and a power estimator connected as a feedback network between the output and the second input of the compressor to estimate, from the compressor output audio signal, the power consumed by the loudspeaker, the power estimator receiving a signal that represents voltage and/or current supplied to the loudspeaker and a parameter that represents an ohmic resistance of the loudspeaker; wherein the power estimator is configured to calculate power consumed by the loudspeaker from two of (i) the voltage supplied to the loudspeaker, (ii) the current supplied to the loudspeaker (iii) and a parameter representing the ohmic resistance of the loudspeaker, and to supply a signal representing the estimated loudspeaker power consumption to the compressor; and wherein the compressor attenuates its input audio signal when the signal representing the estimated loudspeaker power consumption exceeds the signal representing the nominal power of the loudspeaker, a time constant estimator that receives the signal representing the voltage and/or current supplied to the loudspeaker and/or a parameter representing the ohmic resistance or the nominal power of the loudspeaker, and a frequency signal value, and provides two compressor time constants; a timing unit that receives the two compressor time constants and adjusts or adapts an attack time and a release time of the compressor according to the two compressor time constants, where the time constant estimator and the timing unit selectively operate in a first mode of operation and a second mode of operation to control gain of the compressor in response to the input signal or the output signal, where a first adaptive control characteristic or a fixed control characteristic is applied in the first mode of operation and a second adaptive control characteristic is applied in the second mode of operation, a first unit that determines an excess value of the signal level of the input audio signal or the output audio signal over a threshold signal level; and a second unit that sets an attack time parameter to a fixed value if the excess value is above a first certain value and that sets the attack time parameter to a value dependent on the excess value, if the excess value is above a second certain value, where the first certain value is different from the second certain value.