Method and circuits for inductor current measurement in MOS switching regulators

TLDR: In this article, the first and second transistors are operated so that one is on while the other is off, such that the current through the output terminal represents the current passing through the inductor regardless of which of the transistors supplies the current.

Abstract: An inductor current measurement circuit ( 25 ) accurately measures current supplied to an inductor ( 17 ) by a first transistor ( 2 ) and/or a second transistor ( 3 ). The first transistor ( 2 ) has a drain coupled to an input voltage conductor ( 8 ), a gate coupled to a switching signal ( 4 ), and a source coupled to a the first terminal of an inductor 17 . A first sense transistor ( 7 ) has a gate and a drain connected to the gate and train, respectively, of the first transistor ( 2 ), and a source coupled to a first input of a first amplifier ( 13 ) and a drain of a third transistor ( 12 ) having a source coupled to a second supply voltage conductor ( 9 ), and a gate connected to the gate of a fourth transistor ( 15 ). The source of the fourth transistor ( 15 ) is connected to the second supply voltage conductive ( 9 ) and its drain is connected to an output terminal ( 18 ) and a second terminal coupled to the second supply voltage conductor ( 9 ). The first transistor ( 2 ) and second transistor ( 3 ) are included in a DC-DC converter. A second sense transistor ( 10 ) has a gate connected to the gate of the second transistor ( 3 ) and a drain connected to the drain of the second transistor ( 3 ) and to the first terminal of the inductor ( 17 ). The source all the second sense transistor ( 10 ) is coupled to the output terminal ( 18 ). The first and second transistors are operated so that one is on while the other is off, such that the current through the output terminal represents the current through the inductor regardless of which of the first and second transistors supplies the inductor current.