초록 ▼

A circuit and method are presented for making differential voltage measurements when one or both measurement points are at voltages that exceed those allowed by a typical differential amplifier, and is particular useful for monitoring the individual cell voltages of a number of series-connected cell

A circuit and method are presented for making differential voltage measurements when one or both measurement points are at voltages that exceed those allowed by a typical differential amplifier, and is particular useful for monitoring the individual cell voltages of a number of series-connected cells that make up a rechargeable battery in which some cell voltages must be measured in the presence of a high common mode voltage. Each measurement point is connected to an input of a respective voltage divider, with all the divider outputs connected to a multiplexer having two outputs. The two multiplexer outputs are connected to a differential amplifier. When the voltage dividers are "closely matched," the output of the differential amplifier is directly proportional to the differential voltage between the pair of points to which the dividers are connected, and the differential voltage between those two points is accurately determined. The voltage dividers divide down the voltage of each measurement point so that each is low enough to be input to a conventional differential amplifier. By selecting the "ratio" of each voltage divider, the circuit can be used to measure differential voltages in the presence of almost any common mode voltage. The invention requires a single differential amplifier powered by a conventional dual power supply.

대표청구항 ▼

[ I claim:] [1.] A battery cell voltage monitor suitable for measuring the voltage of any individual cell of a multi-cell battery, comprising:a plurality of voltage dividers connectable to the anodes of respective battery cells to divide the voltages at said anodes by respective divider ratios to pr

[ I claim:] [1.] A battery cell voltage monitor suitable for measuring the voltage of any individual cell of a multi-cell battery, comprising:a plurality of voltage dividers connectable to the anodes of respective battery cells to divide the voltages at said anodes by respective divider ratios to produce respective voltage divided outputs, each of said voltage dividers being referenced to a common reference potential,a switching network connected to switch two of said voltage divided outputs to respective complementary outputs,a switching control circuit for operating said switching network to present a sequence of voltage divided outputs to said complementary outputs representing the cell voltages of a sequence of said cells, the divider ratios of said voltage dividers being closely matched so that said voltage divided outputs represent their respective anode voltages divided by approximately the same ratio, anda differential amplifier connected to said complementary outputs and arranged to produce an output representing the differential voltage between said complementary outputs, said amplifier output referenced to said reference potential, said differential amplifier rejecting a majority of the common mode voltage presented at its inputs, said voltage dividers arranged such that their respective voltage divided outputs are each within the allowable input voltage and common mode voltage range of said differential amplifier over an expected range of battery voltages.