Method for measuring an electrical current and apparatus for this purpose

摘要

A method for measuring an electrical current with the aid of a field effect transistor inserted into a current path is disclosed, in which a control voltage is applied between the gate and source of the transistor in such a way that the voltage drop between the drain and source at the transistor in the current path remains within a specifiable range. Further, said voltage drop and the control voltage are determined. With these two values, and with a known relationship between the drain-source current, the drain-source voltage and the gate-source voltage the value of the current of interest can now be determined. Apparatus for implementing the method according to the invention is, furthermore, disclosed.

主权项

1. A method for measuring an electric current via a field effect transistor provided in a current path, the method comprising:
applying a control voltage between a gate and a source of the field effect transistor in such a way that a voltage drop between a drain and the source of the field effect transistor remains within a predetermined range; determining the temperature of the field effect transistor; determining the voltage drop; determining the control voltage; determining a value of the electric current based on the determined voltage drop, the determined control voltage, and the relationship between the drain-source current, the drain-source voltage and the gate-source voltage; and providing a relationship between a drain-source current, a drain-source voltage and a gate-source voltage of a field effect transistor as a channel resistance Rds in a form of a polynomial having coefficients k0 . . . kn, wherein a set of coefficients k0 . . . kn is provided with respect to each of a plurality of control voltages, wherein the polynomial has the form:
Rds=k0+k1·Uds+k2·Uds2+ . . . +kn·Udsn.