Wireless chargers have become more popular over the years, due to their practicality and versatility especially for mobile devices. In this article, we will give an overview on how wireless chargers are homologated in Brazil and who are the responsible agencies.
Wireless chargers work in a very simple way, creating an electromagnetic field by induction between coils, one in the base station and the other in the mobile device battery. The power transfer always involves a base station and a mobile device, both properly shielded in order to avoid user contact with the field. The system basically works as a coreless resonant transformer. The proximity between the two coils ensures an efficient power transfer. A single base station can charge multiple devices depending on its compatibility and settings, in this case it contains multiple transmitters.
Currently the wireless charger is mostly employed on mobile phones, especially on newer models on brands such as Samsung and Nokia. New applications are being developed to fully take part of the advantages this technology offers. Manufacturers are carrying out research to produce furniture with the wireless power transfer technology built-in, and even to charge electric cars, computers and other handheld devices. In Brazil, the technology is limited to smartphones and smartwatches of specific brands.
Standards Applicable to Wireless Chargers
There are two international standards which are used by manufacturers to develop chargers in general: Qi from Wireless Power Consortium, and Rezence from PWA and A4WP, which merged recently and formed AirFuel. These standards are adopted by the main brands, such as Procter & Gamble, Samsung, Microsoft and Intel. Both standards have small differences between them, therefore it is expected that the companies will join to create a single standard for wireless power transfer.
Qi is currently the technology most employed on devices, transferring around 5W of power, although newer versions of the standard may allow a 15W transfer, similar to cable charging. The equipment using the standard operates in frequencies in the 100 - 205 kHz range. Please note that the frequencies 90KHz to 100KHz are restricted and locked by ANATEL.
The Rezence standard is considered to be the most advanced so far, using near-field magnetic resonance, or NFMR, for power transfer at a fixed frequency of 6.78 MHz. Equipment carrying this technology are able to work in more adverse environments, such as those with barriers and with presence of metals, such as the interior of cars, besides the ability to charge more devices simultaneously.
Certification and Homologation
ANATEL is responsible for the certification and homologation of wireless chargers used in telecom devices, considered as restricted radiation equipment. Restricted radiation equipment is defined as any equipment or device that uses radiofrequency for diverse applications, in which the emission produces an electromagnetic field with intensity within the established limits.
Wireless chargers are included in the Category II for ANATEL homologation which encompasses radioelectric for signal transmission, including antenna, restricted radiation equipment, transceptors and others. Therefore, the wireless power transfer equipment goes through the same process of others in this category.
ANATEL consider the following requirements:
- Emission of electromagnetic disturbances: limits for disturbances emitted by the equipment, either is conducted or radiated
- Emission from power lines (AC/DC)
- Immunity for electromagnetic disturbances: guarantee normal operation when the equipment is submitted to such disturbances with compatible intensity
- Resistance to electromagnetic disturbances
- Surge immunity test
- Operational frequency bandwidth
- Irradiated frequency (E.I.R.P.)
- Field intensity
- Risk of fire, electric shock and excessive heating
For power sources of telecommunication devices, the emission testing must occur in the energy output and input.
The general limits of emission according to ANATEL are specified in the table below.
|Radio Frequency Bandwidth (MHz, when not specified)||Field Intensity (microvolt per meter)||Measurement Distance (meter)|
|9 - 490 kHz||2 400/F(kHz)||300|
|490 - 1705 kHz||24 000/F(kHz)||30|
|1 705 - 30||30||30|
|30 - 88||100||3|
|88 - 216||150||3|
|216 - 960||200||3|
The testing applicable is related to the electromagnetic field compatibility and electrical security, following proper standards of IEC, the International Electrotechnical Commission, ITU-T, the International Telecommunication Union, CISPR and ABNT.
INMETRO is responsible for certificating wireless chargers to be used in products in general, except those with telecommunication purposes. The institute uses the same regulations and directives applied by ANATEL for product certification and homologation.