Capacitance voltage conversion circuit, input apparatus using the same, electronic instrument, and capacitance voltage conversion method

摘要

A capacitance voltage conversion circuit, which converts respective capacitances of a plurality of sensor capacitors into voltages, includes: a plurality of capacitance current conversion circuits disposed in respective correspondence with the sensor capacitors, each capacitance current conversion circuit configured to generate a detection current corresponding to a capacitance of a corresponding sensor capacitor; a current average circuit configured to average a plurality of detection currents, which are respectively generated by the capacitance current conversion circuits, to generate an average current; and a plurality of current voltage conversion circuits disposed in respective correspondence with the sensor capacitors, each current voltage conversion circuit configured to convert a difference current between a corresponding detection current and the average current into a voltage.

主权项

1. A capacitance voltage conversion circuit which converts a capacitance of each of a plurality of sensor capacitors into a voltage, the capacitance voltage conversion circuit comprising:
a plurality of capacitance current conversion circuits disposed in respective correspondence with the sensor capacitors, each of the capacitance current conversion circuit configured to generate a detection current corresponding to a capacitance of a corresponding sensor capacitor; a current average circuit configured to average the detection currents, which are generated by the capacitance current conversion circuits, to generate an average current; and a plurality of current voltage conversion circuits disposed in respective correspondence with the sensor capacitors, each of the current voltage conversion circuit configured to convert a difference current between a corresponding detection current and the average current into a voltage, wherein each current average circuit comprises: a plurality of third transistors disposed on a path of the corresponding detection current, in respective correspondence to the sensor capacitors, respective control terminals of the third transistors being connected to each other in common; and a plurality of fourth transistors disposed in respective correspondence with the sensor capacitors, each fourth transistor connected to a corresponding third transistor to form a current mirror circuit therewith, wherein the current average circuit outputs a current, flowing in each of the fourth transistors, as the average current.