Interpretation of FCC KDB 680106 wireless charging (WPT) update

As early as the 19th century, Nikola Tesla had proposed the concept of wireless charging (WPT), but unfortunately it was not realized at that time. It was not until recent decades that WPT was developed and realized, and developed in the smart phone market, becoming a well-known function. For short-range low-power WPT, FCC issued KDB 680106 D01. The published version of the current official website is v03r01 to provide guidance for such products. The latest draft version of DR04 44611 was released on February 18, 2022. Opinions from all parties will be collected before March 20, 2022 and V04 version will be released after this date.

The following is the interpretation of the latest draft version DR04 44611 of KDB 680106 D01:

Content of Change ->->->->->->->->->->->->->->->->->->->

Update published Attachment 680106 D01 v03r01 to DR04 44611 to clarify compliance limits for devices using low power, closely coupled, inductive power transfer techniques. The updated contents are mainly reflected in Section 5 "EQUIPMENT APPROVAL CONSIDERATIONS":

◆ Section 5.1 is distinguished, that is, section 5 in the original v03r01 version:

　The considerations in section 5.1 apply to Part 18 devices that deliver energy to their design targets through non-conducted electromagnetic coupling (thus radiated and/or inductive EM fields) up to and including one meter distance (measured between the farthest points between the transmitting and receiving structures).

◆ Section 5.2 is added, which is not included in the original v03r01 version:

　Additional requirements for Part 18 devices that deliver energy to their design targets through non-conducted electromagnetic coupling at a distance greater than one meter are provided in section 5.2, below：

　Part 18 devices that would otherwise meet the requirements of Section 5.1 may be permitted to deliver electromagnetic energy to a target located at a distance beyond one meter from the transmitter if the following conditions are satisfied:

　◇ The applicant must demonstrate that the RF field in all locations anywhere at or beyond one meter is at or below the level that would be present within 1 meter when all devices being charged are within 1 meter of the transmitter. In other words, the RF emissions must be unaffected by the placement of the load/target device;

　◇ The devices may only operate indoors (i.e., the interior of a fully enclosed, weatherproof structure);

　◇ The indoor operations must be configured (e.g., through proper positioning of transmitter and/or attenuating material structures) such that when measured outdoors, the maximum fundamental and unwanted radiated emissions of the Part 18 device on any non-ISM frequency meet the limits in Part 15 of the Commission’s rules. The distance specified in Part 15 (§ 15.209(a)) for evaluating field strength is to be measured from the outer surface of the structure delimiting the indoor operations;

　◇ Devices shall professionally installed (i.e., by persons who have the necessary training and qualifications to follow manufacturer-provided guidance and conduct necessary measurements and calculations to verify that conditions (2), (3) and (4), stated above, have been met).

Interpretation of content ->->->->->->->->->->->->->->->->->->->

KDB 680106 D01 DR04 44611, the regulations for short-range low-power wireless inductive coupled charging pads or charging devices:

◆ Scope:

　This document primarily deals with low power, closely coupled, inductive power transfer techniques. Others, such as high power devices, devices designed for power transfer at distance and medical devices, it may be necessary for the responsible party(manufacturer) to seek guidance from the FCC on specific WPT devices by submitting a KDB inquiry, http://www.fcc.gov/labhelp.

　*Note: The inquiry should include the following:

　◇ complete product description, including coil diameters , number of turns and current;

　◇ FCC Rule Part(s) the device will operate under and the basis for selecting the Rule Part(s);

　◇ planned equipment authorization procedure (i.e., SDoC or certification);

　◇ drawings, illustrations; frequency of operation; radiated power; operating configurations; and conditions for human exposure.

◆ FCC Rules:

　A WPT device may operate in two different modes: charging and communications.

　◇ WPT products with charging function only, only need to comply with the Part 18 of the FCC rules;

　◇ WPT products with charging and communications function, need to comply with the Part 18 and Part 15 of the FCC rules.

◆ Operation Frequency:

　All technologies that use frequencies above 9 kHz are subject to FCC rules. And devices authorized under Part 15 may not transmit in the 90-110 kHz band.

◆ RF exposure:

　RF exposure is applicable to WPT equipment. Whether Part 15 or Part 18 of the FCC rules is used, it needs to meet the RF exposure requirements.

KDB Inquiry ->->->->->->->->->->->->->->->->->->->

The scope of KDB 680106 D01 mentioned above. For high power devices, devices designed for power transfer at distance and other WPT equipment, KDB inquiry needs to be submitted. In fact, for low power and closely coupled WPT, if the following conditions are not met, KDB inquiry also needs to be submitted, and even Pre-approval guidance (PAG) needs to be carried out:

(1) The power transfer frequency is below 1 MHz;

(2) The output power from each primary coil is less than or equal to 15 watts;

(3) Each client device is placed directly in contact with the transmitter;

(4) Only mobile exposure conditions apply (portable exposure conditions are not covered by this exclusion);

(5) The aggregate H-field strength anywhere at or beyond 15 cm surrounding the device, and 20 cm away from the surface from all coils that by design can simultaneously transmit, and while those coils are simultaneously energized, are demonstrated to be less than 50% of the applicable MPE limit;

(6) For systems with more than one primary coil, the conditions specified in (5) must be met when the system is fully loaded and all coils are powered at the same time.

*Note: Among the above conditions, (1) ~ (3) need to be announced and confirmed by the manufacturer, and (4) ~ (6) need to be tested and evaluated by the laboratory.

In recent years, with the rapid development of smart phones and more and more rich functional configurations, WPT has also entered the public's vision and has basically become the standard function of smart phones. For this function of WPT, major manufacturers not only launch simple WPT pads products, but also develop a variety of products with WPT function such as table lamp, desktop speaker and even mobile power supply. If a manufacturer wants to apply for FCC KDB 680106 D01 WPT certification at this stage, the draft version of DR04 44611 or the official version of v03r01 can be used. However, whichever version is used must be followed in its entirety, mixing and matching is not permitted.

If you want to know more about WPT certification, you are welcome to contact the BTL team at any time. BTL will share the most professional and comprehensive information with you.