Patent ID: 7113603

Claim:
A thermal overload and resonant motion control circuit for an audio speaker having a driver, where the audio speaker is driven by a drive signal from an amplifier, the circuit including: a feedback signal generating (fsg) circuit for generating a feedback signal, said feedback signal being an absolute difference between a proportion of a drive voltage and a proportion of a drive current; and an attenuator operable in response to said feedback signal for controlling said drive signal, wherein said feedback signal is given by f(ai, bv), where i and v are drive current and drive voltage respectively for said drive signal, and where a and b are percentages of i and v respectively utilized by said fsg circuit and wherein said attenuator includes a converter which receives said feedback signal and generates a DC output which is a selected function of the received feedback signal, and a variable attenuator component through which one of the input and output of said amplifier is applied, said DC output being applied to control the level of said variable attenuator component, wherein said drive signal is related to motion of said driver and said drive current, wherein said feedback signal is proportional to the absolute value of K (bv−ai) where K is a gain in said fsg circuit, and wherein a is approximately 0.15% to 0.5% and b is approximately 0.5%.