Technical Blogs

Wireless Charging Interoperability Test Results and Analysis
2017 2017-05-04

Foreword

It was said that wireless charging would be introducing into Apple next generation while there was also news that Apple Inc. had just joined Wireless Power Consortium (WPC) as its new member. As Apple has always been one of market leaders in the industry, such news coming one after another seems to indicate of the market booming and technology development rising into its high peak for the wireless charging that has been regarded as emerging technology for a period of time.

According to the research of IHS Markit, the worldwide wireless charging- transmitter (Tx) & receiver (Rx) market in 2017 are expected to be totally over 600 million units of shipments and would be driven even over 3 times more to reach 2.8 billion units in 2025. From Chart I, we learned that in this market the surging shipments of devices featured as receivers for wireless charging, such as smartphones and smartwatches, have become the main force of wireless charging market and has further driven the increases of the transmitter market.

Chart I – Worldwide wireless charging shipments of 2013 to 2025

(2017 to 2025 as forecasts), sourced from IHS

 

There are more and more wireless charging models and brands available on the market, and thus technique issues required to be overcome are arising such as backward compatibility, or interoperability that can be a potential factor to user experiences, or power charging failure etc. In addition to interoperability test, a total solution for verification of wireless charging should also cover standard certification, wireless charging performance, and wireless charging efficiency.

Standard certification aims at verifying whether a product is in compliance with test specifications required by the standard institute(s), also represents the minimum testing criteria for manufacturers in product quality; and Wireless charging performance & efficiency validation is for a purpose of further verifying whether a product can achieve certain performance level and its corresponding satisfaction that are required under various product specifications; and this category includes security mechanism, power charging performance and charging efficiency, which is targeted to enhance market competitiveness of the products through product differentiation

Under our market research, so far there are still limited wireless products that have been certified to be available from well-known global on-line shops while the rest are all uncertified. By comparing with the products in more matured technology development, such as USB and HDMI, there must be quite a progress to achieve on standard certification for wireless charging products.

 

Wireless Charging Test Primary Focus

We could classify the wireless charging environments into three based on the different scenarios of user experiences for general users: public area, automotive and home/office. Since the natural of human activities within the three environments classified are varied from each other, user behaviors should be different accordingly that cause priority changing regarding such tests. Next, we will show you the wireless charging test primary focus for the three.

Diagram I – Wireless charging test primary focus responding to three environment categories

 

 1. Public Area The typical locations in this category include coffee shops and airports where are open to publics. Interoperability should be the primary focus since whether the transmitters (Tx) for charging services could be matched for normal charging should be in top consideration for consumers carrying of most various models, brands, and devices (Rx).

 

 2. Automotive Thermal control mechanism is a particular concern due to temperature rise and air flow issues within vehicles. Also, in general drivers are likely to leave coins on the platform between the driver’s and front passenger’s seats that can be a potential cause to unconsciously drop the coins contacting the transmitters and thus to lead to unexpected overheating of the coins, therefore Foreign Object Detection(FOD)* validation should be also equally important for wireless charging devices within vehicles.

 

 3. Home/Office Home and office are both indoor environments that are almost the same scenarios for user experiences of wireless charging. We have discovered that both are extremely focused on charging efficiency. As the foreseen increasing demands of home appliances in the near feature and the general expectations from office workers for fast charging of their personal mobile devices for them to carry out soon into occasions such as business visits or conference attendance, whether fast charging featured into wireless charging functions could satisfy the needs as above should then be an issue for the manufacturers, and thus charging performance and efficiency validations are particularly emphasized. We also noticed that user experience testing is helpful to simulate the multiple aspects of user’s daily life in home/office of the real world while such testing can lower potential risks with effective improvement based on the analysis of such testing results.

* Foreign Object Detection (FOD) is a mechanism which enables the charging platform to automatically interrupt of its power supply if there is interference caused by foreign object contact.

However, Interoperability is actually a common issue for those three environments though the priorities among them are varied. In the following, Allion will release our wireless charging interoperability test results with analysis based on the evaluation by scoring for the performance and potential risks of each product items to be a reference for both consumers and manufactures to avoid such interoperability risks as possible.

 

Wireless Charging Interoperability Test Results and Analysis

Currently, Wireless Power Consortium (WPC) and AirFuel Alliance in fact dominate standards adopted generally on the wireless charging markets while the former has introduced of magnetic induction and the latter has recommended of magnetic induction and magnetic resonance in parallel. Allion has developed of our own procedures and criteria higher than which of the two as above after we had studied their standards on interoperability of wireless charging, and recently had such a test through cross validation on a small scale sample set . For this testing, we particularly bought at random 10 new mobiles as receiver (Rx) and 8 charging transmitter (Tx) and in purpose we selected partial samples that had not yet been certified. Among those certified samples, most were under Qi specifications of WPC since products certified by AirFuel Alliance were very limited in the market at the time when we purchased.

Regarding Qi specifications, its version has been updated from V1.0 (the earliest), V.1.1 (first introduced of FOD) till the latest of V1.2 (first defined of Baseline Power Profile/BPP for 5W and of Extended Power Profile/EPP for 15W). Though WPC has no more accepted of any of applications for certification of V1.0 and V1.1, we could still see many devices carrying V1.0 and V.1.1 versions in the market.

Furthermore, as the increasing needs for fast charging feature from consumers, we have seen products with related specifications other than which under WPC and AirFuel Alliance, for example, the Samsung Fast Charge Wireless Charging. Therefore, interoperability issues are not only concerned by related manufacturers but also by general consumers.

Diagram II - Progress Timeline of Qi specification

 Our Test Result: 

On the Table I, the column Rank named as 1 to 10 represent 10 Rx samples while the row Rank named as 1 to 8 represent 8 Tx samples; also, colors are used for standard version indications, including red as which uncertified. We could see the testing result from each of values crossing of each of columns and rows after our cross validation test, as the testing results were valued according to 5 levels from 0, 0.5, 0.75, 0.9 to 1**. The interoperability performance of these samples for its Tx or Rx was assessed by an addition of the values under the same column or row. For example: the Tx of U-brand ranked as the best performance was given 10 as its interoperability performance by an addition of values on each of columns under the row Rank named as 1 that also stands for its testing results. The Tx of S-brand ranked as 2 was scored of 9.9. The higher scores by its addition represent higher performance while the lower represents the contrast. 

During such testing, many details are required to be observed, such as whether charging was continuously in progress without any of spontaneous interruption. We were monitoring the wireless charging processes from its beginning to the end for every of the samples completely to make sure all details were being fully observed.

Table I – Wireless Charging Interoperability Testing Results

(Tx as transmitters/charging pad and Rx as receivers/mobile)

** Meanings of Values

1: The Tx functioned well with the Rx without abnormality.

0.9: The Rx was successfully chargeable, after around 3 seconds of activation latency as a minor flaw.

0.75: The Rx was successfully chargeable, after over 3 seconds of activation latency as possible concerns from users.

0.5: The Tx-Rx pair revealed communication errors when tracking log file. It might seriously affect product performance but still acceptable in general.

0: The Rx could not function with Tx and activation of charging mode was totally in failure.

 

On the Table I, the column Rank named as 1 to 10 represent 10 Rx samples while the row Rank named as 1 to 8 represent 8 Tx samples; also, colors are used for standard version indications, including red as which uncertified. We could see the testing result from each of values crossing of each of columns and rows after our cross validation test, as the testing results were valued according to 5 levels from 0, 0.5, 0.75, 0.9 to 1**. The interoperability performance of these samples for its Tx or Rx was assessed by an addition of the values under the same column or row. For example: the Tx of U-brand ranked as the best performance was given 10 as its interoperability performance by an addition of values on each of columns under the row Rank named as 1 that also stands for its testing results. The Tx of S-brand ranked as 2 was scored of 9.9. The higher scores by its addition represent higher performance while the lower represents the contrast. 

During such testing, many details are required to be observed, such as whether charging was continuously in progress without any of spontaneous interruption. We were monitoring the wireless charging processes from its beginning to the end for every of the samples completely to make sure all details were being fully observed.

 

 1. Interoperability issues could occur if a Tx-Rx pair is certified with diffrent standard versions

For the Tx of N-brand (ranked as 6th) and M-brand (ranked as 8th) that both were certified with Qi V1.0 (earliest standard), there were distinct interoperability issues between them and the mobile devices (Rx) certified with QV1.1or QiV1.2 (latest standard until now). Also, charging was not even working between Tx-of-M-brand and the two different models of S-brand mobile (Rx) that both had been certified. From the point of views of mobile(Rx), the two models of M-brand mobile (ranked as 8th and 10th respectively) that both were certified with Qi V1.1 did not work on most of transmitters(Tx) samples due to interoperability issues, including transmitters(Tx) without any of certifications and which on V.10 or V1.1 certified.

From the testing results as above, we discovered that in general the interoperability of V1.0 specifications (earliest one) is comparatively poor since even the products have been certified that means has reached minimum standard requirements, interoperability issues still occurred from a matched pair both Qi-certified but in varied versions. We here propose two solutions: 1) Interoperability performance could be improved by an introduction of latest certification specifications; and 2) In addition to standard certification, a package with total validation solutions to review every aspects of one product is recommended. Wireless charging products on latest standard version also would be a recommended choice for consumers.

 

 2. Interoperability performance could be inconsistent if products are in different components

The two uncertified Tx were on inconsistent performance while Tx-of-M-brand ranked as 4th was given 9 as its total score after cross validation of being matched with the 10 samples(Rx) in turns and Tx-of-A-brand, scored only 7.5 in total, were not even working at all on Rx-M-brand ranked as 10th at charging

In general, product specifications, chips, and coils are the three major factors on quality of wireless charging products. After we disassembled the two uncertified Tx, we discovered that these two as A-brand and M-brand had been installed of chips on the identical model. However, there could be still many possible causes on such inconsistent performance regarding interoperability, including circuit design as well as the corresponding coil selections. Further investigation is required.

Allion currently provides engineering services for such issue probing with solutions by our professional verifications/validations testing. Free consulting services are also available for preliminary detection. Contact Allion

 

 3. Higher standard test specifications could reduce interoperability issues arising from a Tx-Rx pair of the same brand.

Out of our expectation, problems occurred during the charging of the Tx-Rx pair on the same I-brand certified with Qi V1.1. We assumed that the cause could be arising from the suppliers varied. A matched pair on the same brand in general is viewed from the consumers as the easiest way to avoid most interoperability issues. By seeing such testing results, we then suggest that higher standard test specifications, along with well supply chain management, before shipments could be one way to maintain product reliability.

 

Conclusion

As Apple is introducing of wireless charging feature into its products and increasing users are demanding of such feature that have brought to increasing enquiries at purchasing for 15W fast power charging, there are however also increasing issues arising from fast charging that in general is easily to cause overheating due to higher electric current. Until now the market mechanism and related standards are still immature, so there is no doubt of a total solution for verifications/validations of wireless charging products, including interoperability testing, standard certification, power charging performance and charging efficiency.

By comparisons and analysis of product performance and features among different brands, manufacturers can precisely position of their products in the markets and then with good marketing strategies such products would be already reinforced of their competitiveness before shipments that could materially respond to the expectations from consumers for their charging needs.

 

 

 

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