Patent ID: 8704586

Claim:
A capacitance detecting apparatus, coupled to a capacitor to be measured, the apparatus comprising: a first capacitor and a second capacitor, coupled to the capacitor to be measured via an input node; a control module, for providing a first voltage-drop variation to the first capacitor and a second voltage-drop variation to the capacitor to be measured to introduce a third voltage-drop variation to the second capacitor; wherein the first voltage-drop variation and the second voltage-drop variation cause charge flowing from the first capacitor to the input node to have a same sign with charge flowing from the input node to the capacitor to be measured; and a judging module, for determining capacitance of the capacitor to be measured according to capacitance of the first capacitor, capacitance of the second capacitor, the first voltage-drop variation, the second voltage-drop variation and the third voltage-drop variation, wherein the capacitor to be measured is connected to the capacitance detecting apparatus via a connecting wire formed on a circuit board, the circuit board has a shielding layer, and the first capacitor comprises parasitic capacitance between the connecting wire and the shielding layer, and the control module controls the shielding layer to provide the first voltage-drop variation of the first capacitor.