| 摘要 |
<p>This application relates to methods and apparatus for determining the temperature of a voice coil of a loudspeaker 204, for instance as part of a system 208 for protecting the loudspeaker from overheating. The method comprises driving the voice coil with signal components at first and second frequencies, wherein the first frequency (fH,) is higher than the second frequency (fL), and determining first and second indications of current ICM and voltage VCM of the voice coil at said first and second frequencies respectively. The method involves determining an estimated ratio value using the first and second indications of current and voltage, wherein said estimated ratio value corresponds to a ratio between a value based on the resistance of the voice coil and a value based on the inductance of the voice coil. The temperature of the voice coil is then determined based on said estimated ratio value and at least one reference value. An impedance extraction module 210 may extract values for the impedance at the first and second frequencies respectively ZH, ZL. In some embodiments a module 212 may determine estimated values of the resistance REM and inductance LEM of the voice coil which are used by temperature estimation block 214 to determine the temperature.</p> |
