Method and apparatus for near losslessly measuring inductor current
AssigneeKoninklijke Philips Electronics N.V.
InventorJerome E. Liebler
Life of this patent
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Abstract
The present invention provides an improved measuring circuit for measuring a current of an inductor with minimum losses and errors. According to one embodiment of the invention, the measuring circuit comprises an op-amp, a RC network connected in a feedback loop of the op-amp, and a scaling resistor connected in series to one of the input terminals of the op-amp. By setting the RC constant of the RC network to be equal to the ratio of the inductor value over its internal resistance value, the inductor current can be derived independent of the frequencies of AC signals.
Claims14
A measuring circuit for measuring a current of an inductor having an internal resistance, the inductor having a first end and a second end, the circuit comprising:
- an op-amp having first and second input terminals and an output terminal, with the second terminal for connecting the first end of the inductor;
- an RC network connected between the first input terminal and the output terminal of the op-amp;
- and
- a scaling resistor having a first end connected to the first input terminal of the op-amp and a second end for connecting to the second end of the inductor;
- wherein the RC network comprises a resistor and a capacitor connected to each other in parallel;
- and
- wherein a product of the values of the resistor and capacitor of the RC network is equal to a ratio of the inductor value over the internal resistance of the inductor.
A measuring circuit for measuring a current of an inductor having an internal resistance, the inductor having a first end and a second end, the circuit comprising:
- op-amp means having first and second input terminals and an output terminal, with the second terminal for connecting the first end of the inductor;
- RC network means connected between the first input terminal and the output terminal of the op-amp means;
- and
- scaling resistor means having a first end connected to the first input terminal of the op-amp means and a second end for connecting to the second end of the inductor;
- wherein the RC network means comprises a resistor and a capacitor connected to each other in parallel;
- and
- wherein a product of the values of the resistor and capacitor of the RC network means is equal to a ratio of the inductor value over the internal resistance of the inductor.
A converter, comprising:
- an input circuit for receiving input signals;
- an output circuit including an inductor having an internal resistance, the inductor having a first end and a second end;
- a control circuit for controlling the input circuit based on a current of the inductor;
- and
- a measuring circuit for measuring the inductor current, the measuring circuit including:
- an op-amp having first and second input terminals and an output terminal, with the second terminal for connecting the first end of the inductor;
- an RC network connected between the first input terminal and the output terminal of the op-amp;
- and
- a scaling resistor having a first end connected to the first input terminal of the op-amp and a second end for connecting to the second end of the inductor;
- wherein the RC network comprises a resistor and a capacitor connected to each other in parallel;
- and
- wherein a product of the values of the resistor and capacitor of the RC network is equal to a ratio of the inductor value over the internal resistance value of the inductor.
A method for measuring a current of an inductor having an internal resistance, the inductor having a first end and a second end, comprising:
- connecting an RC network between a first input terminal and an output terminal of an op-amp;
- connecting the output terminal of the op-amp to the first end of the inductor;
- and
- connecting a first end of a scaling resistor to the first input terminal of the op-amp and a second end of the scaling resistor to the second end of the inductor;
- wherein the RC network comprises a resistor and a capacitor connected to each other in parallel;
- and
- wherein a product of the values of the resistor and capacitor of the RC network is equal to a ratio of the inductor value over the internal resistance value of the inductor.
Dependencies are inferred from the claim text.