Foreign object detection in inductive coupled devices
AssigneeRobert Bosch GmbH
InventorsHariharakumaran Dorairaj, Rajeev Kumar, Surabhi Ganguly
Life of this patent
Estimating the term…
Abstract
A primary device for inductive power transfer to a secondary device is disclosed. The primary device includes a primary coil, the primary device being configured to (i) operate in a first mode during which the primary coil transfers power through inductive coupling to the secondary device, and (ii) operate in a second mode during which a foreign object is detected. The primary device further includes a primary controller configured to operate the primary coil (i) using a first frequency during the first mode, and (ii) using a second frequency during the second mode. A method to detect a foreign object which is in proximity of an inductively coupled environment of a primary device is also disclosed.
Claims7
A primary device for inductive power transfer to a secondary device, the primary device comprising:
- a primary coil, the primary device being configured to (i) operate in a first mode during which the primary coil transfers power through inductive coupling to the secondary device and a load is connected to the secondary device, the secondary device being configured to supply the transferred power to the load, and (ii) operate in a second mode during which the load is disconnected from the secondary device and a foreign object is detected;
- and
- a primary controller configured to operate the primary coil (i) using a first frequency during the first mode while the load is connected to the secondary device, and (ii) using a second frequency during the second mode while the load is disconnected from the secondary device;
- wherein the primary device is configured to measure a primary current in the primary device while the primary coil is being operated at the second frequency during the second mode to detect presence or absence of the foreign object, and
- wherein the secondary frequency corresponds to an operating frequency at which the primary current does not vary with respect to an air gap between the primary coil and a secondary coil of the secondary device.
A method to detect a foreign object which is in proximity of an inductively coupled environment of a primary device, comprising:
- connecting a load to a secondary device and operating a primary coil of the primary device using a first frequency during a power transfer mode;
- disconnecting the load from the secondary device;
- after disconnecting the load from the secondary device, operating the primary coil using a second frequency during a measurement mode, the second frequency being the point where a first current curve corresponding to a minimum air gap between the primary device and the secondary device meets a second current curve corresponding to a maximum air gap between the primary device and the secondary device;
- measuring the primary current during the measurement mode while operating the primary coil at the second frequency so as to sense a measured current;
- and
- detecting whether a foreign object is present by comparing the measured current with a set threshold.
Dependencies are inferred from the claim text.