Patent ID: 7596232

Claim:
An apparatus for adjusting sound volume for an audio system, the apparatus comprising: a controller connected to an amplifier of the audio system for controlling amplification of the amplifier, the controller comprising: a microprogrammed control unit (MCU) for controlling a switch to switch an operating mode of the apparatus, wherein the operating mode comprises an attenuation mode; and a first circuit for adjusting the sound volume, the first circuit comprising: an attenuation circuit for attenuating input audio signals, the attenuation circuit comprising; a first resistor, a first end of the first resistor being connected to a tuner of the audio system; a second resistor, a first end of the second resistor being connected to a second end of the first resistor; a first diode, the anode of the first diode being connected to the second end of the first resistor; a second diode, the cathode of the second diode being connected to the cathode of the first diode; a third diode, the cathode of the third diode and the anode of the second diode being connected to a second end of the second resistor in parallel; a fourth diode, the anode of the fourth diode being connected to the anode of the third diode, the cathode of the fourth diode being connected to the second end of the first resistor; a third resistor, a first end of the third resistor being connected to the cathode of the first diode; a fourth resistor, a first end of the fourth resistor being connected to a second end of the third resistor, and a second end of the fourth resistor being connected to the anode of the fourth diode; a transistor, the base of the transistor being connected to the second end of the third resistor, the emitter of the transistor being connected to the first end of the third resistor, and the collector of the transistor being connected to the second end of the fourth resistor; and an integrated operational amplifier, the inverting input end of the integrated operational amplifier being connected to the second end of the first resistor, the non-inverting input end of the integrated operational amplifier being grounded, and the output end of the integrated operational amplifier being connected to the second end of the second resistor; and the switch, an input end of the switch being connected to the tuner of the audio system, the output end of the integrated operational amplifier and the MCU, and an output end of the switch being connected to an audio processor of the audio system; wherein when the apparatus is in the attenuation mode, the MCU controls the switch to switch the first circuit to the attenuation mode and the attenuation circuit attenuates the input audio signal, the attenuation being a first slight attenuation if the input audio signal is relatively “weak ” according to a predefined criterion, the attenuation being a second significant attenuation greater than the first slight attenuation if the input audio signal is relatively “strong ” according to the predefined criterion.