Module and Capacitance Detecting Method

摘要

A capacitance detecting circuit includes a constant current source supplying a constant current to a voltage detection point, a time measuring unit measuring time of charge until the voltage of the voltage detection point reaches a prescribed voltage, a storage unit and an operation unit. The storage unit stores first data obtained in advance concerning the time of charge of a capacitance element having a known capacitance value, and second data obtained in advance concerning the time of charge of a capacitance component. The operation unit generates third data representing the time of charge of an object of detection from a difference between the first measurement value of the time measuring unit when the capacitance component is connected to the voltage detection point and the second data, and based on the ratio between the third data and the first data and the known capacitance value, calculates the capacitance value of the object of detection.

主权项

1. A module, comprising:
(a) a current path connected to an object of detection and including a capacitance component; and (b) a capacitance detecting circuit supplying a constant current to said object of detection through said current path, for determining a capacitance value of said object of detection, said capacitance value detecting circuit including:
(1) a constant current source supplying said constant current to a voltage detection point;(2) a storage unit storing: (a) first data, obtained in advance of said determination of said capacitance value, concerning a time it takes to charge a capacitance element having a known capacitance value to said prescribed voltage when said constant current is applied to said capacitance element and (b) second data, obtained in advance of said detection of said capacitance value, concerning a time it takes to charge said capacitance component to said prescribed voltage when said constant current is applied to said capacitive component;(3) a charge/discharge circuit connecting said current path to said voltage detection point to charge both said object of detection and said capacitance component, and disconnecting said current path from said voltage detection point to discharge both said object of detection and said capacitance component;(4) a time measuring circuit generating a third data indicative of a time it takes to charge said object of detection and said capacitance component with said constant current to cause said voltage detection point to attain said prescribed voltage; and(5) an operation unit:
(a) generating fourth data representing a time it takes to charge said object of detection from a difference between said third data and said second data; and(b) calculating a capacitance value of said object of detection based on a ratio between said third data and said first data.