Wireless power transmitters and associated base stations for transmitting power at extended separation distances

A base station for wireless power transfer at an operating frequency selected from a range of about 87 kilohertz (kHz) to about 205 kHz, the base station comprising:

• a power transmitter that comprises:
• a control and communications unit;
• an inverter circuit configured to receive input power and convert the input power to a power signal;
• a coil structure configured to transmit the power signal to a device having a power receiver, the coil structure comprising at least one layer of Litz wire, wherein the coil structure has a top surface, a bottom surface, and a side surface;
• and
• a shielding structure comprising a ferrite material and having a cavity, the cavity configured such that the ferrite material surrounds at least a portion of the bottom surface of the coil structure and at least a portion of the side surface of the coil structure;
• and
• an interface surface for placement of a device having a power receiver, wherein the interface surface comprises a first plane having a first height relative to the top surface of the coil structure and a second plane having a second height relative to the top surface of the coil structure, wherein the second height is greater than the first height by a gap distance in a range of 8 millimeters (mm) to 10 mm,
• wherein the coil structure is positioned below the first plane of the interface surface, and
• wherein the interface surface is configured such that, when a given device having a given power receiver is placed on the interface surface, (i) the given power receiver is separated from the coil structure by a separation distance that is no less than the gap distance between the second height of the second plane and the first height of the first plane and (ii) the power transmitter is capable of delivering wireless power signals to the given power receiver.

A power transmitter for wireless power transfer at an operating frequency selected from a range of about 87 kilohertz (kHz) to about 205 kHz, the power transmitter comprising:

• a control and communications unit;
• an inverter circuit configured to receive input power and convert the input power to a power signal;
• a coil structure configured to transmit the power signal to a device having a power receiver, the coil structure comprising multiple layers of Litz wire, wherein the multiple layers of Litz wire comprises a first layer and a second layer,
• wherein each of the first layer and the second layer comprises a respective number of turns in a range of about 4 turns to about 5 turns,
• wherein the coil structure has a top surface, a bottom surface, and a side surface, an outer diameter length in a range of about 40 mm to about 50 mm, an inner diameter length a range of about 15 mm to about 25 mm, and a thickness in a range of about 2 mm to about 3 mm;
• and
• an E-Core type shielding structure comprising a ferrite material and having a cavity, the cavity configured in an E-Core configuration such that the ferrite material surrounds at least a portion of the bottom surface of the coil structure and at least a portion of the side surface of the coil structure,
• wherein the power transmitter is contained within a base station that comprises an interface surface for placement of a device having a power receiver, wherein the interface surface comprises a first plane having a first height relative to the top surface of the coil structure and a second plane having a second height relative to the top surface of the coil structure, wherein the second height is greater than the first height by a gap distance in a range of 8 millimeters (mm) to 10 mm,
• wherein the coil structure is positioned below the first plane of the interface surface, and
• wherein the interface surface is configured such that, when a given device having a given power receiver is placed on the interface surface, (i) the given power receiver is separated from the coil structure by a separation distance that is no less than the gap distance between the second height of the second plane and the first height of the first plane and (ii) the power transmitter is capable of delivering wireless power signals to the given power receiver.