Microphone detection and selection circuit and method

A microphone detection method carried out by a microphone detection circuit for detecting whether an external device includes a microphone, comprising the following steps:

• generating a digital audio signal according to an analog input signal which is a signal from the external device or a preset signal;
• determining whether the digital audio signal satisfies a predetermined threshold to thereby generate an analysis result in which the analysis result indicates that the external device includes the microphone if the digital audio signal satisfies the predetermined threshold;
• and
• executing an operation according to the analysis result,
• wherein when the external device includes the microphone, the analog input signal is the signal generated by the microphone and the digital audio signal generated according to the analog input signal has a value varying by time to reflect human voice or background sound, and then the decision unit determines that the digital audio signal satisfies the predetermined threshold;
• and when the external device includes no microphone, the analog input signal is the preset signal and the digital audio signal generated according to the analog input signal is a constant value, and then the decision unit determines that the digital audio signal fails to satisfy the predetermined threshold.

A microphone selection circuit for choosing one of a plurality of microphones, comprising an audio circuit for receiving a first analog input signal of an external microphone and a second analog input signal of a built-in microphone, the audio circuit including:

• at least one analog-to-digital conversion unit to generate a digital audio signal according to the first or second analog input signal;
• a decision unit to generate an analysis result according to one or more parameters associated with at least one state of a microphone signal process;
• and
• a control unit, coupled to the decision unit and the analog-to-digital conversion unit, to make the analog-to-digital conversion unit generate the digital audio signal by the first or second analog input signal in accordance with the analysis result, and make the audio circuit execute the microphone signal process with the digital audio signal,
• wherein when the one or more parameters indicate that the at least one state conforms to a voice recognition state, the control unit chooses the first analog input signal of the external microphone according to the analysis result to execute a first microphone signal process, when the one or more parameters indicate that the at least one state conforms to a microphone-signal-less state, the control unit makes the audio circuit use the external microphone according to the analysis result to execute the first microphone signal process, and when the one or more parameters indicate that the at least one state conforms to a recording state, the control unit chooses the second analog input signal of the built-in microphone according to the analysis result to execute a second microphone signal process.