Loudspeaker overload protection

Patent metadata

Field	Value
Publication number	US-9729951-B2
Application number	US-201313774529-A
Country	US
Kind code	B2
Filing date	Feb 22, 2013
Priority date	Feb 22, 2012
Publication date	Aug 8, 2017
Grant date	Aug 8, 2017

Abstract

A loudspeaker overload protection circuit and method receives at a compressor a signal representing the estimated loudspeaker power consumption; receives at the compressor a signal representing the nominal power of the loudspeaker; receives at the compressor an input audio signal from the signal source and supplying with the compressor an output audio signal to the loudspeaker; estimates from the output audio signal, (a) signal(s) that represent(s) the voltage and/or current supplied to the loudspeaker and a parameter that represents the ohmic resistance of the loudspeaker the power consumed by the loudspeaker; supplies a signal representing the estimated loudspeaker power consumption to the compressor; and attenuates the input audio signal when the signal representing the estimated loudspeaker power consumption exceeds the signal representing the nominal power of the loudspeaker.

First claim

What is claimed is:

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.

2. The circuit of claim 1 , further comprising a smoothing filter connected between the power estimator and the second input of the compressor.

3. The circuit of claim 1 , where the first adaptive control characteristic is dependent on a signal level of the input audio signal and the fixed control characteristic is independent of the signal level.

4. The circuit of claim 1 , where the second adaptive control characteristic is dependent on a release time parameter in the second mode of operation.

5. The circuit of claim 1 , where the time constant estimator and the timing unit are cooperatively configured to set a release time parameter dependent on a signal level.

6. The circuit of claim 5 , where the first adaptive control characteristic depends on an attack time parameter in the first mode of operation.

7. The circuit of claim 1 , where the time constant estimator is a signal processing unit that processes the signal according to a given function or a table stored in memory.

8. A loudspeaker overload protection method for protecting a loudspeaker that is connected to a signal source, the method comprises:
receiving at a compressor a signal indicative of estimated loudspeaker power consumption;
receiving at the compressor a signal indicative of nominal power of the loudspeaker;
receiving at the compressor an input audio signal from the signal source and applying a gain to the input audio signal and providing an output audio signal indicative therefore to the loudspeaker;
estimating power consumed by the loudspeaker from two of (i) voltage supplied to the loudspeaker and providing a loudspeaker voltage signal indicative thereof, (ii) current supplied to the loudspeaker and providing a loudspeaker current signal indicative thereof (iii) and a parameter representing an ohmic resistance of the loudspeaker and providing an estimated loudspeaker power consumption signal;
attenuating with the compressor the input audio signal when the estimated loudspeaker power consumption signal exceeds the signal representing the nominal power of the loudspeaker;
providing, via a time constant estimator, two compressor time constants;
adjusting an attack time and a release time of the compressor according to the two compressor time constants;
selectively operating in a first mode of operation and a second mode of operation to control the gain of the compressor in response to the output audio 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;
providing the output audio signal representing the input audio signal amplified by an initial gain value;
determining a signal level of the input audio signal or the audio output signal and comparing the signal level with a threshold level;
if the signal level is below the threshold level, updating the initial gain value using the second adaptive control characteristic; and
if the signal level is above the threshold level, updating, dependent on the signal level, the initial gain value using a fixed control characteristic or the first adaptive control characteristic respectively; where:
the first adaptive control characteristic is dependent on the signal level and the fixed control characteristic is independent from the signal level.

9. The method of claim 8 , further comprising smoothing the signal that represents the estimated loudspeaker power consumption.

10. The method of claim 8 , further comprising providing at least one of the two compressor time constants in response to a received frequency signal.

11. The method of claim 10 where the at least one of the two compressor time constants is determined based upon one of a given function or a table stored in memory.

Assignees

• Harman Becker Automotive Systems Gmbh

Inventors

• Wolf Florian
• Perzlmaier Peter
• Scholz Leander
• Christoph Markus
• Spielbauer Georg

Classifications

• H04R3/007 Primary

  Protection circuits for transducers · CPC title

• H04R1/00 Primary

  Details of transducers, {loudspeakers or microphones} · CPC title