Current sense shunt resistor circuit

Abstract

Current through a wire is sensed with a shunt resistor and a sense resistor in a current divider circuit. The values of the shunt resistor and sense resistor are related to provide a specified gain ratio to increase a dynamic range of current measurement. The sense resistor is a trimmable resistor, the configuration of which can be discerned from a look-up table based on a level of precision needed for current measurement. The two resistors can also be related by thermal coefficients to improve linearity of current measurements.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates generally to sensing output current in an electrical circuit. The present invention relates more particularly to a shunt resistor connected to an electrical circuit output to measure the current of the output. [0003] 2. Description of Related Art [0004] A number of electrical applications, in particular power applications, take advantage of output current sensing to provide feedback control for the electrical circuit or system. Typically, the output current is sensed by measuring a voltage drop across a highly precise resistance to thereby determine the current flowing through the resistance related to the measured voltage drop. Because this technique inherently requires a voltage drop, there is often a large amount of power dissipated in the resistance with large current flows. Indeed, because power equals the resistance times the current squared, increasing current determines an incre...

AI Technical Summary

Benefits of technology

[0010] The data from Table 2 indicates that as the application current increases, the dynamic range available through the appropriately sized shunt resistor decrease

Problems solved by technology

Because this technique inherently requires a voltage drop, there is often a large amount of power dissipated in the resistance with large current flows.

With the limited dynamic range resulting from the lowered shunt resistance, the accuracy and precision of voltage measurements is degraded.

For example, the thermal resistance of the shunt is fairly high causing an increase in shunt temperatures due to heat and resistance power dissipation.

Accordingly, in the higher range of measured current there is a loss of precision in reading the voltage drop across the shunt.

The measurable quantities of changing voltage related to current are thus reduced in higher current applications, making accurate current measurement problematic.

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