Wireless power Rx control IC meets Qi Low Power Ver1.1 with FOD function

February 13, 2014 // By Graham Prophet
This wireless charging receiver chip claims low heat generation together with a misalignment detection function and foreign object detection, to ensure high efficiency operation

A major challenge with 5W-class wireless power transmission for smartphones and other portable equipment is the relatively large amount of heat generated during charging. Rohm says it has addressed this issue with its BD57011GWL, which is compliant with WPC’s (Wireless Power Consortium) latest Qi Low Power Ver1.1 standard for wireless power transmission and features low heat generation in a monolithic design, reducing temperature rise by up to 75% during wireless charging. This provides an ideal balance between mounting area and heat generation. In addition, a misalignment detection function detects incorrect positioning of the target device on the charging pad, which can lead to decreased charging efficiency. Rohm uses a BiC-DMOS processes to achieve the lowest MOSFET ON-resistance possible.

During charging, incorrectly positioning the target device on the charging pad may cause a significant drop in charging efficiency. To prevent this, ROHM has included a misalignment detection function that triggers an alarm, allowing the user to reposition the device to achieve maximum charging efficiency.

Established by WPC in April of 2012, the difference between the latest standard and Low Power Ver1.0, established in 2010, is that Ver1.1 includes the requirement for a built-in FOD (Foreign Object Detection) function to improve safety. FOD is required in the latest Qi standard in order to prevent chassis deformation and/or burns due to excessive heat generation of a foreign metallic object when placed between the transmitter and receiver, dramatically improving safety.

FOD involves calibration of the receiver and transmitter, achieved in this case by combining Rohm’s analogue technology together with (Rohm Group) Lapis Semiconductor’s digital expertise.

Since the power loss is calculated at the receiving end, the different loss error for each receiver can be fine-tuned via external resistor, ensuring flexible, high-precision FOD operation.

The Qi standard is expanding the compatible power range to meet the growing needs of the wireless power transmission market; Rohm is currently developing power receiver control ICs and products designed