Systems, methods, and apparatus for detecting ferromagnetic foreign objects in a predetermined space

An apparatus for detecting a presence of an object located in a charging region of a wireless power transmitter having an operating frequency, the apparatus comprising:

• an inductive sense circuit having a sense coil configured to inductively sense the presence of the object based on an electrical characteristic of the sense coil that changes when the object is within a sufficient distance from the sense coil, wherein a coupling between the wireless power transmitter and the sense coil produces noise that interferes with a detection sensitivity of the sense coil;
• and
• a processor configured to:
• apply a sense signal to the inductive sense circuit to inductively sense the presence of the object, and
• adjust at least one of a waveform of the sense signal or the operating frequency of the wireless power transmitter to avoid the noise,
• wherein the electrical characteristic comprises an impulse response of the inductive sense circuit when the waveform of the sense signal is a pulse waveform or a frequency response of the inductive sense circuit when the waveform of the sense signal is suitable to measure the frequency response.

An apparatus for detecting a presence of an object located in a charging region of a wireless power transmitter having an operating frequency, the apparatus comprising:

• an inductive sense circuit having a sense coil configured to inductively sense the presence of the object based on an electrical characteristic of the sense coil that changes when the object is within a sufficient distance from the sense coil, wherein a coupling between the wireless power transmitter and the sense coil produces noise that interferes with a detection sensitivity of the sense coil;
• and
• a processor configured to:
• apply a sense signal to the inductive sense circuit to inductively sense the presence of the object, and
• adjust at least one of a waveform of the sense signal or the operating frequency of the wireless power transmitter to avoid the noise,
• wherein the processor is further configured to actively compensate for a fundamental frequency component of the noise as measured at a measurement location by additionally applying a compensation signal to the inductive sense circuit, and
• wherein the inductive sense circuit comprises a plurality of inductive sense circuits, each including a sense coil;
• and wherein the processor is further configured to multiplex measurements of the electrical characteristic of the plurality of respective sense coils, to detect a change in the measured electrical characteristics, and determine presence of the object based on the detected change.

An apparatus for detecting a presence of an object located in a charging region of a wireless power transmitter having an operating frequency, the apparatus comprising:

• an inductive sense circuit having a sense coil configured to inductively sense the presence of the object based on an electrical characteristic of the sense coil that changes when the object is within a sufficient distance from the sense coil, wherein a coupling between the wireless power transmitter and the sense coil produces noise that interferes with a detection sensitivity of the sense coil;
• and
• a processor configured to:
• apply a sense signal to the inductive sense circuit to inductively sense the presence of the object, and
• adjust at least one of a waveform of the sense signal or the operating frequency of the wireless power transmitter to avoid the noise,
• wherein the processor is configured to apply a periodic pulse signal in synchronism with the operating frequency of the wireless power transmitter and wherein the processor is further configured to improve the detection sensitivity by adjusting a pulse phase to a suitable time instance with respect to switching transients generated by the wireless power transmitter.

A method for detecting a presence of an object located in a charging region of a wireless power transmitter having an operating frequency, comprising:

• inductively sensing, via an inductive sense circuit having a sense coil, the presence of the object based on an electrical characteristic of the sense coil that changes when the object is within a sufficient distance from the sense coil, wherein a coupling between the wireless power transmitter and the sense coil produces a noise that interferes with a detection sensitivity of the sense coil;
• applying a sense signal to the inductive sense circuit to inductively sense the presence of the object;
• and
• adjusting at least one of a waveform of the sense signal or the operating frequency of the wireless power transmitter to avoid the noise,
• wherein the electrical characteristic comprises an impulse response of the inductive sense circuit when the waveform of the sense signal is a pulse waveform or a frequency response of the inductive sense circuit when the waveform of the sense signal is suitable to measure the frequency response.

A method for detecting a presence of an object located in a charging region of a wireless power transmitter having an operating frequency, comprising:

• inductively sensing, via a plurality of inductive sense circuits each having a sense coil, the presence of the object based on an electrical characteristic of a respective one of the sense coils that changes when the object is within a sufficient distance from the respective sense coil, wherein a coupling between the wireless power transmitter and the respective sense coil produces a noise that interferes with a detection sensitivity of the respective sense coil;
• applying a sense signal to each of the plurality of inductive sense circuit to inductively sense the presence of the object via the plurality of inductive sense circuits;
• and
• adjusting at least one of a waveform of the sense signal or the operating frequency of the wireless power transmitter to avoid the noise,
• wherein adjusting the waveform of the sense signal comprises adjusting the waveform of the sense signal applied to each of the plurality of inductive sense circuit, and
• wherein adjusting the frequency of the sense signal comprises adjusting the frequency of the sense signal applied to each of the plurality of inductive sense circuits in a manner such that the noise remains outside of a sensitive frequency range as defined by the filtering of the at least one of a voltage or current signal.

A method for detecting a presence of an object located in a charging region of a wireless power transmitter having an operating frequency, comprising:

• inductively sensing, via an inductive sense circuit having a sense coil, the presence of the object based on an electrical characteristic of the sense coil that changes when the object is within a sufficient distance from the sense coil, wherein a coupling between the wireless power transmitter and the sense coil produces a noise that interferes with a detection sensitivity of the sense coil;
• applying a sense signal to the inductive sense circuit to inductively sense the presence of the object;
• and
• adjusting at least one of a waveform of the sense signal or the operating frequency of the wireless power transmitter to avoid the noise,
• wherein adjusting the waveform of the sense signal comprises adjusting a frequency of the sense signal to improve the detection sensitivity, and
• wherein avoiding the produced noise comprises actively compensating for a fundamental frequency component of the noise as measured at a measurement location by additionally generating and applying a compensation signal to each of the plurality of inductive sense circuits.

A method for detecting a presence of an object located in a charging region of a wireless power transmitter having an operating frequency, comprising:

• inductively sensing, via an inductive sense circuit having a sense coil, the presence of the object based on an electrical characteristic of the sense coil that changes when the object is within a sufficient distance from the sense coil, wherein a coupling between the wireless power transmitter and the sense coil produces a noise that interferes with a detection sensitivity of the sense coil;
• applying a sense signal to the inductive sense circuit to inductively sense the presence of the object;
• and
• adjusting at least one of a waveform of the sense signal or the operating frequency of the wireless power transmitter to avoid the noise,
• wherein applying a sense signal comprises generating and applying a periodic pulse signal in synchronism with the operating frequency of the wireless power transmitter and wherein improving a detection sensitivity comprises adjusting the pulse phase to a suitable time instance with respect to switching transients generated by the wireless power transmitter.

A method for detecting a presence of an object located in a charging region of a wireless power transmitter having an operating frequency, comprising:

• inductively sensing, via a plurality of inductive sense circuits each having a sense coil, the presence of the object based on an electrical characteristic of a respective one of the sense coils that changes when the object is within a sufficient distance from the respective sense coil, wherein a coupling between the wireless power transmitter and the respective sense coil produces a noise that interferes with a detection sensitivity of the respective sense coil;
• applying a sense signal to each of the plurality of inductive sense circuit to inductively sense the presence of the object via the plurality of inductive sense circuits;
• and
• adjusting at least one of a waveform of the sense signal or the operating frequency of the wireless power transmitter to avoid the noise,
• wherein adjusting the waveform of the sense signal comprises adjusting the waveform of the sense signal applied to each of the plurality of inductive sense circuit, and
• wherein each of the plurality of inductive sense circuits is configured as a resonant circuit having a resonant frequency substantially at the frequency of the sense signal applied to each of the inductive sense circuits.

A method for detecting a presence of an object located in a charging region of a wireless power transmitter having an operating frequency, comprising:

• inductively sensing, via an inductive sense circuit having a sense coil, the presence of the object based on an electrical characteristic of the sense coil that changes when the object is within a sufficient distance from the sense coil, wherein a coupling between the wireless power transmitter and the sense coil produces a noise that interferes with a detection sensitivity of the sense coil;
• applying a sense signal to the inductive sense circuit to inductively sense the presence of the object;
• and
• adjusting at least one of a waveform of the sense signal or the operating frequency of the wireless power transmitter to avoid the noise,
• wherein adjusting the waveform of the sense signal comprises adjusting a frequency of the sense signal to improve the detection sensitivity, and
• wherein the inductive sense circuit is configured as a resonant circuit having a resonant frequency substantially at the frequency of the sense signal applied to the inductive sense circuit;
• and further comprising adjusting the frequency of the sense signal to improve the detection sensitivity while remaining substantially at resonance of the inductive sense circuit.