Electromagnetic flow sensor interface including sensor drive circuit
First Claim
1. An apparatus for providing an excitation current to an electromagnetic flow sensor having an excitation coil and first and second sensing electrodes, the apparatus comprising:
- an H-Bridge control circuit configured to deliver control signals to respective inputs of a plurality of transistors of an H-Bridge to control delivery of a current to the excitation coil by the H-Bridge, the H-Bridge control circuit including;
a first integrated isolation circuit including an inductive transformer to electrically isolate and inductively couple at least one of the control signals delivered to the respective input of at least one of the plurality of transistors of the H-Bridge; and
a current control circuit coupled to a switched mode power supply to adjust a reference voltage, used to generate the current delivered to the excitation coil, during a specified portion of a switching cycle of the H-Bridge to compensate for inductance emf of the excitation coil.
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Accused Products
Abstract
An interface circuit to an electromagnetic flow sensor is described. In an example, it can provide a DC coupled signal path from the electromagnetic flow sensor to an analog-to-digital converter (ADC) circuit. Examples with differential and pseudo-differential signal paths are described. Examples providing DC offset or low frequency noise compensation or cancellation are described. High input impedance examples are described. Coil excitation circuits are described, such as can provide on-chip inductive isolation between signal inputs and signal outputs. A switched mode power supply can be used to actively manage a bias voltage of an H-Bridge, such as to boost the current provided by the H-Bridge to the sensor coil during select time periods, such as during phase shift time periods of the coil, which can help reduce or minimize transient noise during such time periods.
24 Citations
20 Claims
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1. An apparatus for providing an excitation current to an electromagnetic flow sensor having an excitation coil and first and second sensing electrodes, the apparatus comprising:
an H-Bridge control circuit configured to deliver control signals to respective inputs of a plurality of transistors of an H-Bridge to control delivery of a current to the excitation coil by the H-Bridge, the H-Bridge control circuit including; a first integrated isolation circuit including an inductive transformer to electrically isolate and inductively couple at least one of the control signals delivered to the respective input of at least one of the plurality of transistors of the H-Bridge; and a current control circuit coupled to a switched mode power supply to adjust a reference voltage, used to generate the current delivered to the excitation coil, during a specified portion of a switching cycle of the H-Bridge to compensate for inductance emf of the excitation coil. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of providing an electromagnetic flow sensor excitation signal, the method comprising:
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delivering control signals to respective inputs of a plurality of transistors of an H-Bridge to control delivery of a current to an excitation coil of an electromagnetic flow sensor by the H-Bridge; electrically isolating and inductively coupling, using an inductive transformer, at least one of the control signals delivered to the respective input of at least one of the plurality of transistors of the H-Bridge; and adjusting a reference voltage, used to provide the current delivered to the excitation coil by the H-Bridge, during a specified portion of a switching cycle of the H-Bridge to compensate for inductance emf of the excitation coil. - View Dependent Claims (12, 13, 14, 15)
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16. An apparatus for providing an electromagnetic flow sensor excitation signal, the apparatus comprising:
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means for delivering control signals to respective inputs of a plurality of transistors of an H-Bridge to control delivery of a current to an excitation coil of an electromagnetic flow sensor by the H-Bridge; means for electrically isolating and inductively coupling, using an inductive transformer, at least one of the control signals delivered to the respective input of at least one of the plurality of transistors of the H-Bridge; and means for adjusting a reference voltage, used to provide the-current delivered to the excitation coil by the H-Bridge, during a specified portion of a switching cycle of the H-Bridge to compensate for inductance emf of the excitation coil. - View Dependent Claims (17, 18, 19, 20)
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Specification