[번역요약]

 무선 충전을 더욱 효과적으로 진행하려면 무선 충전기와 수신기의 코일이 최대한 가깝게 위치하게 배치해야합니다. 하지만 정확한 위치에 장치를 놓지 못하면 충전 속도가 느려지거나 충전이 전혀 되지 않을 수도 있습니다. 일부 제조업체에서는 이러한 문제를 해결하기 위해 충전기 안에 다중으로 많은 코일을 넣어 어느 지점에 놓더라도 정확한 위치를 찾도록 개선했습니다. 언뜻 보기에 좋은 해결책으로 보일 수 있지만, 다중 코일 배열은 충전 전력을 효율적으로 제공하지 않을 수도 있습니다.

 

무선 충전 및 코일

무선 충전은 두 개의 코일을 가깝게 배치하여 물리적으로 접촉이 아닌 자기 유도 방식으로 전력 전송을 할 수 있습니다. 사용 중인 장치 품질에 따라 두 코일 간의 거리는 작게 몇 밀리미터 정도여야 하는데, 보통 코일은 눈에 보이지 않게 숨겨져 있기 때문에 정확한 위치를 찾기 어려울 수 있으며, 그 결과 종종 충전 속도가 느려지거나 아예 충전이 되지 않을 수도 있습니다.

 

다중 코일로 충전 전력 향상은 불가

 코일이 다중으로 여러 개 있어도, 무선 충전 시 그중 한 번에 하나만 활성화가 되기 때문에 코일이 여러 개가 있더라도 충전 전력이 상승하지 않습니다. 때문에, 다중 코일 배열은 전력 공급보단 주로 편의성 즉, 수신기 장치를 충전 패드 위에 올릴 때 정확한 위치를 찾아 헤매지 않더라도 충전이 가능하게끔 만드는 것에 목적을 두고 있다는 표현이 좀 더 정확합니다.

 

다중 코일의 문제점

 코일을 다중으로 사용하려면, 코일끼리 서로 겹치게 배열하는데, 하단에 설치된 코일은 수신기의 코일에서 더 멀리 떨어져 전력 전송 효율이 떨어지면서 충전 속도가 느려지거나 과도한 전력을 소비하게 됩니다. 또 상단 코일에 부분적으로 방해를 줄 수 있으며, 하단 코일의 거리 증가와 결합하여 동력 전달의 효율성을 더욱 감소시킬 수 있습니다.

 

코일 구성 요소 추가, 품질 저하

 충전 코일은 무선 충전기 내부 부품 중에서 비싼 요소이기 때문에, 다중으로 많은 코일을 배열하면 필연적으로 비용이 비싸지게 됩니다. 일부 제조업체는 이러한 비용 문제를 해결하기 위해 품질이 떨어지는 코일을 사용하기도 하는데, 단지 장치 배치 편의성만을 위해 비싼 비용을 지불하는 것은 고객 입장에선 좋지 못한 방법입니다.

 

단일 코일을 더 좋게 만들기

 다중 코일 구현의 대안으로는 단일 코일을 넓은 면적을 충전할 수 있도록 설계하는 것입니다. 이런 강화된 단일 코일의 경우 충전 유효 면적을 극대화할 수 있을 뿐만 아니라 다중 코일을 사용할 때보다 출력 효율과 냉각을 개선하여 전반적인 충전 성능을 향상할 수 있도록 설계 및 재료에 더 많은 투자가 가능합니다.

 

[칼럼원문] 작성자 : TRENT 출처 : https://www.moshi.com/en/blog/more-coils-doesnt-mean-more-power/

Why more coils does not always mean better charging

One of the key challenges in achieving effective wireless charging is positioning the coils of the charger and receiver close enough to one another that they can transfer power. Incorrect positioning can lead to slow charging or in some cases no charging at all. In order to solve this problem, some manufacturers have attempted to squeeze several coils into a single charging surface with the hope that the user will be able to find the sweet spot on at least one of those coils in order to commence charging. While this appears to be a creative solution, the use of such arrays may not deliver the most efficient charging experience and the use of a single enhanced coil may in fact be a better way to deliver worry-free wireless charging. 

 

Wireless charging and coils

On a very basic level, wireless charging works by positioning two coils close enough to each other (usually one in a charger and another in a receiver such as a smartphone) that they are able to transfer power by magnetic induction without physically touching. Depending on the engineering quality of the devices being used, the separation between the two coils needs to be as little as a couple of millimeters in order to charge. The fact that these coils are usually concealed behind covers or casings can make it very difficult to find the correct positioning, with the result often being slow charging or none at all.

Both the transmitter (charger) and receiver (phone) contain charging coils which must align correctly in order to transfer power.

 

If you're new to the world of wireless power transmission, check out our Ultimate Guide to Wireless Charging to get the low-down on all aspects of this exciting charging technology. 

 

Multiple coils don't increase charging power

 

Probably the most common misconception to address is that even in an array of multiple charging coils, only one of those will be active at any one time. It is not possible to pool the energy of several coils together to deliver an overall higher dose of charging power to the receiver device. The use of coil arrays is primarily in the interests of convenience and efficiency improvement rather than overall power delivery.

Coils are usually layered on top of one another in order to achieve a multi-coil array.

"It is not possible to pool the energy of several coils together to deliver an overall higher dose of charging power"

 

More coils can create more problems

Some manufacturers believe that there's more likelihood of lining up with at least one coil if there are more of them. This is indeed an innovative solution which can increase the chances of correct coil positioning without needing to pay a great deal of attention to where on the charging pad you may be placing your device, but the implementation itself brings about two further issues which can negatively affect charging performance.

Layering of coils increases distance - In order to fit the maximum number of coils under a charging surface, these coils are often layered, partially overlapping each other. Those coils installed on the lower layer(s) of the array will therefore be further away from the receiver device's coil, reducing the efficiency of power transfer and resulting in slower charging or excessive power consumption (or both).

Obstruction of overlapping coils - Another side-effect of layering is that the coils in lower layers can be partially obstructed by those above, which combined with the aforementioned distance increase for bottom-layer coils can further decrease the efficiency of power transfer.

The lower coils in an array are located further from the charging surface, and can be obstructed by other coils.

 

Added components, reduced quality

It goes without saying that adding duplicates of the same component to a product will increase the overall cost of production, and with the charging coil being one of the more advanced components inside the average wireless charger, adding several to a single unit will quickly increase the price paid by the end customer. As multi-coil arrays do not deliver any significant performance improvements in terms of charging output or speed, paying significantly more for just the convenience of device placement may be a hard sell for many customers. In order to keep production costs down, manufacturers may choose to use several lower-spec (and lower-cost) coils instead of a single high-performance one, and as only one coil is ever in use at a time, the overall charging experience may suffer due to the decreased performance of each single coil.

 

Making one coil better

The alternative to implementing large arrays of inferior coils is to engineer a single charging coil which is capable of charging over a larger area, thus reducing the need for pinpoint accuracy when placing a device down on the charging surface. When using only one coil, a greater investment can be made in design and materials to maximize the effective charging area of the coil as well as improve output efficiency and cooling for better overall charging performance. This was the path favored by Moshi when we developed our Q-coil™ module, which you can read more about in our dedicated post.

"When using only one coil, a greater investment can be made in design and materials"

While there are some advantages of utilizing coil arrays to improve wireless charging, the additional challenges which arise in the use of such a design can further affect the user experience. Moshi's preference for premium, single-coil charging solutions has led to the creation of some of the industry's most awarded wireless chargers, with large effective charging areas and enhanced passive cooling delivering improved performance. Learn more about our range of Q Collection wireless chargers at moshi.com.