Field regulator
First Claim
1. A field regulator for a resonant circuit, the resonant circuit including an inductor coil around a core, the field regulator including:
- a DC bias circuit configured to apply a DC bias current to the inductor coil for regulating an electromagnetic field generated by the inductor;
a feedback control system in which a level of the applied DC bias current is determined based on a current measured in the resonant circuit;
a current detector for detecting a current flow of the resonant circuit; and
a bias current controller for controlling the DC bias current based on the detected current flow of the resonant circuit.
1 Assignment
0 Petitions
Accused Products
Abstract
The invention generally relates to a field regulator, particularly a field regulator for a resonant circuit, a transmitter including such a field regulator, a proximity detection system including such a transmitter, and a method of regulating a resonant circuit. In one aspect the invention provides a field regulator for a resonant circuit, the resonant circuit including an inductor coil around a core, the field regulator including a DC bias circuit configured to apply a DC bias current to the inductor coil for regulating an electromagnetic field generated by the inductor. The DC bias circuit can be used to selectively change the inductance of the inductor in the resonant circuit so as to maintain a consistent field strength in a changing environment, particularly to take into account the presence of large metal bodies which might otherwise adversely impact on operation. In particular, the DC bias current may be used to selectively change the natural frequency of the resonant circuit so as to shift the resonant circuit towards a desired resonance point.
12 Citations
17 Claims
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1. A field regulator for a resonant circuit, the resonant circuit including an inductor coil around a core, the field regulator including:
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a DC bias circuit configured to apply a DC bias current to the inductor coil for regulating an electromagnetic field generated by the inductor; a feedback control system in which a level of the applied DC bias current is determined based on a current measured in the resonant circuit; a current detector for detecting a current flow of the resonant circuit; and a bias current controller for controlling the DC bias current based on the detected current flow of the resonant circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A transmitter including:
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a resonant circuit including an inductor coil around a core; a field regulator including a DC bias circuit for applying a DC bias current to the inductor coil for regulating an electromagnetic field generated by the inductor; a feedback control system in which a level of the applied DC bias current is determined based on a current measured in the resonant circuit; a current detector for detecting a current flow of the resonant circuit; and a bias current controller for controlling the DC bias current based on the detected current flow of the resonant circuit. - View Dependent Claims (10, 11, 12, 13, 14)
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15. A method of regulating a resonant circuit, the resonant circuit including an inductor coil, the method including the steps of:
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applying a DC bias current to the inductor coil for regulating an electromagnetic field generated by the inductor; setting the DC bias current to a predetermined value; measuring the response of a current flow in the resonant circuit to an incremental change in the DC bias current; determining whether a change to the DC bias current is required to achieve a desired resonance point for the resonant circuit; and in response to determining that the change to the DC bias current is required; adjusting the DC bias current, and applying the adjusted DC bias current to the inductor coil. - View Dependent Claims (16, 17)
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Specification