Method and apparatus for computing metric values for loudspeaker protection
First Claim
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1. A method for computing metrics for loudspeaker protection, comprising the following steps:
- (1) providing a loudspeaker, a voltage and a current meter, a speaker protection monitor comprising computational and filtering means, and a speaker protection device;
(2) measuring speaker input current and voltage;
(3) filtering by band-pass filters speaker input voltage and current values measured wherein the band-pass filtered speaker input voltage and current values measured are described by the equations;
im,bpf(t)=ibpf(t)+ε
i,bpf(t), and
vm,bpf(t)=vbpf(t)+ε
v,bpf(t)wherein im,bpf(t) is the filtered input current, ibpf(t) is the input current measured, ε
i,bpf(t) describe the current error signals, vmmbpf(t) describes is the filtered input voltage, Vbpf(t) is the input voltage measured, and ε
v,bpf(t) describe the voltage error signals;
(4) using cross-correlation and autocorrelations equations based on band-passed measurement results to compute loudspeaker protection metrics including a real part of impedance of a voice coil of the loudspeaker, wherein components of the cross-correlation and autocorrelations equations comprise following equations of instantaneous products required for computations of correlations;
ii(t)=im,bpf(t)·
im,bpf(t),
iv(t)=im,bpf(t)·
vm,bpf(t), and
vv(t)=vm,bpf(t)·
vm,bpf(t);
(5) activating speaker protection device if the real part of the loudspeaker impedance exceeds a threshold; and
(6) going back to step (2) if input signals of speaker are active.
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Abstract
Systems and methods thereof for obtaining metrics and an accurate threshold to prevent loudspeaker overheating, based on autocorrelation and cross-correlation of band-pass filtered current and voltage measurements are disclosed. The methods invented are based on instantaneous voltage and current measurements. The invention does not require a DC or pilot signal to be added to the audio signal in order to do perform the measurement, and it is not disturbed by capacitive or inductive components in the complex impedance of the voice coil.
24 Citations
33 Claims
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1. A method for computing metrics for loudspeaker protection, comprising the following steps:
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(1) providing a loudspeaker, a voltage and a current meter, a speaker protection monitor comprising computational and filtering means, and a speaker protection device; (2) measuring speaker input current and voltage; (3) filtering by band-pass filters speaker input voltage and current values measured wherein the band-pass filtered speaker input voltage and current values measured are described by the equations;
im,bpf(t)=ibpf(t)+ε
i,bpf(t), and
vm,bpf(t)=vbpf(t)+ε
v,bpf(t)wherein im,bpf(t) is the filtered input current, ibpf(t) is the input current measured, ε
i,bpf(t) describe the current error signals, vmmbpf(t) describes is the filtered input voltage, Vbpf(t) is the input voltage measured, and ε
v,bpf(t) describe the voltage error signals;(4) using cross-correlation and autocorrelations equations based on band-passed measurement results to compute loudspeaker protection metrics including a real part of impedance of a voice coil of the loudspeaker, wherein components of the cross-correlation and autocorrelations equations comprise following equations of instantaneous products required for computations of correlations;
ii(t)=im,bpf(t)·
im,bpf(t),
iv(t)=im,bpf(t)·
vm,bpf(t), and
vv(t)=vm,bpf(t)·
vm,bpf(t);(5) activating speaker protection device if the real part of the loudspeaker impedance exceeds a threshold; and (6) going back to step (2) if input signals of speaker are active. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
wherein, if threshold(t) is positive, a maximum allowable resistance of the voice coil is exceeded and the speaker protection device is activated.
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11. The method of claim 1 wherein the speaker protection device, if activated, is lowering a temperature of the voice coil.
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12. The method of claim 11 wherein the speaker protection device, if activated, is improving a cooling of the voice coil.
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13. The method of claim 11 wherein the speaker protection device, if activated, is lowering the temperature of the voice coil by reducing an average power that is dissipated as heat at the voice coil.
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14. A system for preventing any damage of a loudspeaker because of over-heating of a voice coil comprising:
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a voltage meter capable of measuring a signal input voltage of the loudspeaker and transmitting voltage measurement results to a speaker protection monitor and a current meter measuring a signal input current of the loudspeaker and transmitting current measurement results to a speaker protection monitor; the speaker protection monitor configured to using cross-correlation and autocorrelations equations based on band-passed measurement results of loudspeaker voltage and loudspeaker current and to compute loudspeaker protection metrics, wherein the speaker protection monitor comprises a band-pass filter configured to filtering speaker input voltage and current values measured wherein the band-pass filtered speaker input voltage and current values measured are described by the equations;
im,bpf(t)=ibpf(t)+ε
i,bpf(t), and
vm,bpf(t)=vbpf(t)+ε
v,bpf(t)wherein im,bpf(t) is the filtered input current, ibpf(t) is the input current measured, ε
i,bpf(t) describe the current error signals, vm,bpf(t) describes is the filtered input voltage, vbpf(t) is the input voltage measured, and ε
v,bpf(t) describe the voltage error signals; anda speaker protection device capable of lowering a temperature of the voice coil, if activated by the speaker protection monitor. - View Dependent Claims (15, 16, 17, 18, 19)
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20. A system for preventing any damage of a loudspeaker because of over-heating of a voice coil comprising:
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a loudspeaker comprising at least one voice coil and two signal input ports; a voltage meter configured to measuring a signal input voltage of the loudspeaker and transmitting voltage measurement results to a speaker protection monitor; a current meter configured to measuring a signal input current of the loudspeaker and transmitting current measurement results to a speaker protection monitor; said speaker protection monitor comprising; one or more band-pass filters configured to filtering speaker input voltage and current values measured wherein the band-pass filtered speaker input voltage and current values measured are described by the equations;
im,bpf(t)=ibpf(t)+ε
i,bpf(t), and
vm,bpf(t)=vbpf(t)+ε
v,bpf(t)wherein im,bpf(t) is the filtered input current, ibpf(t) is the input current measured, ε
i,bpf(t) describe the current error signals, vm,bpf(t) describes is the filtered input voltage, vbpf(t) is the input voltage measured, and ε
v,bpf t describe the voltage error signals;one or more averaging filters; an output port capable of to transmit a signal to a speaker protection device in order to activate the speaker protection device if required; and means to compute cross correlation and autocorrelation calculations comprising computing the loudspeaker threshold; and said speaker protection device capable of lowering, if activated, a temperature of the voice coil. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
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Specification