Patent ID: 7362588

Claim:
A flying capacitor type battery voltage detector, comprising: a circuit substrate having a front surface and a back surface opposite to the front surface in a thickness direction of the circuit substrate; a plurality of potential detecting substrate surface lines which are each disposed on the front or back surface of the circuit substrate, the potential detecting substrate surface lines being connected with a plurality of terminals of cells or groups of cells of a battery pack, respectively; a first floating line disposed on the front or back surface of the circuit substrate; a second floating line disposed on the front or back surface of the circuit substrate; a multiplexer including a first portion disposed on the front surface of the circuit substrate and a second portion disposed on the back surface of the circuit substrate such that the second portion substantially lies over the first portion through the circuit substrate in the thickness direction of the circuit substrate, the multiplexer sequentially connecting pairs of the potential detecting substrate surface lines, being connected with the terminals of each cell or each group of cells, with the first and second floating lines, respectively; a flying capacitor, connected with the first and second floating lines, which holds an electric energy transmitted from each cell or each group of cells through the pairs of the potential detecting substrate surface lines connected with the terminals of each cell or each group of cells and the first and second floating lines; and an analog switch which is maintained in an off state when the pairs of the potential detecting substrate surface lines connected with the terminals of each cell of each group of cells are, respectively, connected with the first and second floating lines by the multiplexer, and which is turned on when the pairs of the potential detecting substrate surface lines are disconnected from the first and second floating lines, the electric energy of the flying capacitor being outputted through the analog switch when turned on in a form of a signal as a function of an output voltage appearing between the terminals of each cell or each group of cells.