Friendly metal loss estimation for wireless power transfer

A method performed by control circuitry of a wireless power transmitter or a wireless power receiver for estimating friendly metal losses associated with wireless power transfer from the wireless power transmitter to a wireless power receiver, the method comprising:

• obtaining an indication of received power including rectifier voltage and rectifier current of the wireless power receiver;
• and
• computing a friendly metal power loss based on the indication of rectifier voltage and rectifier current of the wireless power receiver and one or more coefficients corresponding to a baseline wireless power transmission between the wireless power transmitter and the wireless power receiver;
• and
• regulating wireless power transfer using the friendly metal power loss;
• wherein:
• the rectifier voltage is a rectifier output voltage, and the rectifier current is a rectifier output current;
• and
• computing the friendly metal power loss uses an equation having a form:
• P
• l
• ⁢
• o
• ⁢
• s
• ⁢
• s
• =
• a
• ·
• I
• T
• ⁢
• X
• 2
• +
• b
• ·
• I
• rect
• 2
• +
• c
• ·
• V
• rect
• 2
• where b is a first coefficient relating to the rectifier current, c is a second coefficient relating to the rectifier voltage, a is a coefficient relating to transmitter current, and ITX is the transmitter current.

A wireless power transmitter comprising:

• a wireless power transfer coil configured to magnetically couple to a wireless power transfer coil of a wireless power receiver to wirelessly transfer power to the wireless power receiver;
• an inverter configured to receive input power and generate an output that drives the wireless power transfer coil;
• and
• controller and communication circuitry coupled to the inverter and the wireless power transfer coil that controls the inverter to regulate wireless power transfer to the wireless power receiver, wherein the controller and communication circuitry estimates friendly metal losses associated with wireless power transfer to the wireless power receiver by:
• receiving from the wireless power receiver an indication of received power including rectifier voltage and rectifier current of the wireless power receiver;
• computing a friendly metal power loss based on the rectifier voltage and rectifier current of the wireless power receiver and one or more coefficients corresponding to a baseline wireless power transmission between the wireless power transmitter and the wireless power receiver;
• and
• regulating wireless power transfer to the wireless power receiver using the friendly metal power loss;
• wherein:
• the rectifier voltage is a rectifier output voltage, and the rectifier current is a rectifier output current;
• and
• computing the friendly metal power loss uses an equation having a form:
• P
• l
• ⁢
• o
• ⁢
• s
• ⁢
• s
• =
• a
• ·
• I
• T
• ⁢
• X
• 2
• +
• b
• ·
• I
• rect
• 2
• +
• c
• ·
• V
• rect
• 2
• where b is a first coefficient relating to the rectifier current, c is a second coefficient relating to the rectifier voltage, a is a coefficient relating to transmitter current, and ITX is the transmitter current.