Patent ID: 8649504

Claim:
A circuit for matching impedance, comprising a processor which comprises: a peripheral impedance detection module, an analog switch handover module and an impedance matching module connected successively, wherein: the peripheral impedance detection module is configured to detect a user telephone impedance and output information about the user telephone impedance; the analog switch handover module is configured to provide an impedance matching path between the user telephone impedance and the impedance matching module according to the information about the user telephone impedance; and the impedance matching module is configured to provide a corresponding impedance to match the user telephone impedance through the impedance matching path provided by the analog switch handover module; the peripheral impedance detection module further comprises an analog-to-digital conversion (ADC) detection module configured to: according to a resistance value of the user telephone impedance, output the user telephone impedance information in a high level or low level format; and the ADC detection module comprises: a first resistance (R 0 ), a second resistance (R 1 ), a third resistance (R 2 ), a fourth resistance (R 3 ), a first voltage comparator (N 1 ) and a second voltage comparator (N 2 ); and the impedance matching module comprises a fifth resistance (Ry) and a sixth resistance (Rz); wherein: one end of the first resistance (R 0 ) connects a system power (Vcc), another end connects a user telephone impedance (Rx) and negative input ends of the first voltage comparator (N 1 ) and the second voltage comparator (N 2 ); one end of the second resistance (R 1 ) is earthed, another end connects a positive input end of the first voltage comparator (N 1 ) and the third resistance (R 2 ); one end of the third resistance (R 2 ) connects the positive input end of the first voltage comparator (N 1 ) and the second resistance (R 1 ), another end connects a positive input end of the second voltage comparator (N 2 ) and the fourth resistance (R 3 ); one end of the fourth resistance (R 3 ) connects the system power (Vcc), another end connects the positive input end of the second voltage comparator (N 2 ) and the third resistance (R 2 ); the second resistance (R 1 ), the third resistance (R 2 ), and the fourth resistance (R 3 ) are divider resistances, providing reference voltage of the first voltage comparator (N 1 ) and the second voltage comparator (N 2 ); output ends of the first voltage comparator (N 1 ) and the second voltage comparator (N 2 ) connect the analog switch handover module, the first voltage comparator (N 1 ) and the second voltage comparator (N 2 ) output the high level or low level according to a resistance value of the user telephone impedances (Rx).