Patent ID: 7567679

Claim:
A system for controlling sound volume, the system comprising a key input unit, an MCU (Microprogrammed Control Unit), and a volume effect IC (Integrated Circuit), wherein: the key input unit is configured for receiving user operations, generating a corresponding controlling signal according to each operation, and transmitting the controlling signal to the MCU; the MCU is configured for determining a mode of adjusting volume according to the controlling signal and an elapsed time of the user continuously operating the key input unit, the MCU comprising: a timer configured for recording the elapsed time; a memory configured for storing controlling programs; and a CPU (Central Processing Unit) configured for receiving the controlling signal, comparing the elapsed time with a preset time, generating PWM (Pulse-Width Modulation) pulses with a corresponding duty ratio according to the comparison result, and transmitting the PWM pulses to the volume effect IC; the volume effect IC is configured for setting the volume as mute if the elapsed time is greater than the preset time according to the PWM pulses when the system is at a preliminary status or adjusting volume by a first amount if the elapsed time is less than or equal to the preset time, and adjusting volume by a second amount if the elapsed time is greater than the preset time according to the PWM pulses when the system is at a volume adjusting status; and wherein the key input unit comprises a “increase” key and a “decrease” key, the volume effect IC is configured for setting volume as mute if the elapsed time of pressing the “decrease” key is greater tham the preset time, and adjusts volume by the first amount if the elapsed time of pressing the “increase” key or the “decrease” key is less than or equal to the preset time, and adjusts volume by the second amount if the elapsed time of pressing the “increase” key is greater than the preset time when the system at the preliminary status.