FIELD REGULATOR

• US 20170032878A1
• Filed: 04/16/2015
• Published: 02/02/2017
• Est. Priority Date: 04/17/2014
• Status: Active Grant

• Current Assignee: Mine Site Technologies Pty Limited (Komatsu Ltd.)
• Original Assignee: Mine Site Technologies Pty Limited (Komatsu Ltd.)
• Inventors: SWEENEY, Peter John, WILDT, Martin Christopher
• Granted Patent: US 10,304,608 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01D 5/2006 by influencing the self-induction of one or more coils G01D5/22 takes precedence
• CPC Class Codes: H01F 19/04 Transformers or mutual inductances suitable for handling frequencies considerably beyond the audio range resonant circuits H03H
• CPC Class Codes: H01F 21/08 by varying the permeability of the core, e.g. by varying magnetic bias
• CPC Class Codes: H01F 27/24 Magnetic cores
• CPC Class Codes: H01F 27/28 Coils; Windings; Conductive connections
• CPC Class Codes: H02M 7/4818 with means for adaptation of resonance frequency, e.g. by modification of capacitance or inductance of resonance circuits
• CPC Class Codes: H02M 7/5387 in a bridge configuration
• CPC Class Codes: H03K 17/954 controlled by an oscillatory signal
• CPC Class Codes: H03K 3/017 Adjustment of width or dutycycle of pulses pulse width modulation H03K7/08 ; to maintain energy constant H03K3/015
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

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.

Claims

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.

2. The field regulator of claim 1, including a feedback control system in which the level of the applied DC bias current is determined based on a current measured in the resonant circuit.

3. The field regulator of claim 2 including:

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.

4. The field regulator of claim 3, configured to adjust the DC bias current based on a resonant circuit response to an incremental change in the DC bias current.

5. The field regulator of claim 4, wherein the bias current controller is configured to adjust the DC bias current based on a detected change in the current flow of the resonant circuit in response to an incremental change in the DC bias current.

6. The field regulator of claim 3, wherein the current detector includes a current sensing resistor.

7. The field regulator of claim 3, wherein the current detector is configured to sample the current flow of the resonant circuit at regular intervals.

8. The field regulator according to claim 3, wherein the bias current controller is coupled to a resonant circuit controller which controls an alternating power supply to said resonant circuit.

9. The field regulator according to claim 8, wherein the alternating power supply includes a H-bridge controller for controlling a driving frequency for driving the resonant circuit.

10. The field regulator of claim 1, wherein the DC bias current source is decoupled from high voltages of the resonant circuit.

11. A transmitter including:

a resonant circuit including an inductor coil around a core; and

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.

12. The transmitter of claim 11, wherein the resonant circuit includes blocking means to isolate the inductor coil such that the DC bias current only flows through the inductor coil.

13. The transmitter of claim 12, wherein the resonant circuit includes two or more capacitors connected in series to the inductor coil.

14. The transmitter according to claim 13, wherein a current sensing resistor is connected in series with one or more of the capacitors to enable detection of current flow through the inductor.

15. The transmitter according to claim 11, wherein the resonant circuit includes an H-bridge for converting a DC signal from a DC power source to an AC signal for driving the resonant circuit.

16. A proximity detection system including the transmitter of claim 11.

17. A method of regulating a resonant circuit, the resonant circuit including an inductor coil, the method including the steps of:

applying a DC bias current to the inductor coil for regulating an electromagnetic field generated by the inductor.

18. The method of claim 17, including the steps of:

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; and

determining whether a change to the DC bias current is required to achieve a desired resonance point for the resonant circuit.

19. The method of claim 18, including the steps of:

increasing the DC bias current if the current flow of the resonant circuit increases in response to an incremental increase in the DC bias current and/or decreases in response to an incremental decrease in the DC bias current;

or decreasing the DC bias current if the current flow of the resonant circuit increases in response to an incremental decrease in the DC bias current and/or decreases in response to an incremental increase in the DC bias current.

20. The method of claim 18, wherein adjusting the DC bias current involves adjusting a Pulse Width Modulation (PWM) duty cycle of the DC bias current.