Patent ID: 8582786

Claim:
A method of controlling a signal level associated with an amplifier of an audio system where the amplifier includes a plurality of amplifier units, comprising the following steps of: comparing a signal level associated with a first amplifier unit of the amplifier by a first comparator with first threshold levels; integrating an output signal of the first comparator by a first integrator with a predetermined first time constant; establishing a first predetermined time length for detecting whether the signal level associated with the first amplifier unit is excessive for a time equal to or longer than the first predetermined time length; comparing an output voltage of the first integrator by a second comparator with second threshold levels and producing a comparator output when the output voltage of the first integrator reaches the second threshold level; reducing a gain of the first amplifier unit of the amplifier by a first gain control circuit when the second comparator produces the comparator output at an end timing of the first predetermined time length; integrating an output signal of the second comparator by a second integrator with a second predetermined time constant; establishing a second predetermined time length for detecting whether the output signal of the second comparator is excessive for a time equal to or longer than the second predetermined time length; comparing an output voltage of the second integrator by a third comparator with third threshold levels and producing a comparator output when the output voltage of the second integrator reaches the third threshold level; and reducing a gain of a second amplifier unit of the amplifier by a second gain control circuit when the third comparator produces the comparator output at an end timing of the second predetermined time length.