磁共振or磁感應（譯自QI）
Architects of wireless power transfer systems face a couple of choices in the configurations of coils and the magnetic transfer technique. The best choice depends on the application:
無線充電系統的設計構造有幾個部分需要作出選擇，即線圈參數設置和磁場轉換技術選擇。但是具體方案還是要根據不同的設備來確定：
選擇1：發射線圈和接收線圈之間是使用松耦合還是緊耦合？
Inductive power transfer works by creating an alternating magnetic field (flux) in a transmitter coil and converting that flux into an electrical current in the receiver coil. Depending on the distance between the transmit and receive coils, only a fraction of the magnetic flux generated by the transmitter coil penetrates the receiver coil and contributes to the power transmission. The more flux reaches the receiver, the better the coils are coupled.
磁感應能量轉換是通過在發射線圈裡創造一個變化的磁場實現的，接收線圈將變化的磁場轉換為電流。由於發射線圈和接收線圈之間的距離不同，只有一部分發射線圈產生的磁場能夠被接收線圈吸收並轉化為電能。在整個過程中，接收線圈收到的磁通量越大，則兩個線圈耦合性越好。
A higher coupling factor improves the transfer efficiency, and reduces losses and heating. Applications with a larger distance between the transmit and receive coils operate, by definition, as a loosely coupled system. In loosely coupled systems, only a fraction of the transmitted flux is captured in the receiver. That means that loosely coupled systems have higher electromagnetic emissions, making them less suitable for applications with tight EMI or EMF requirements.
耦合性越高，線圈之間傳輸能量的效率越高，並且會減少漏磁和線圈的發熱。在應用過程中，若發射線圈與接收線圈相距較遠，則被稱為松耦合系統（loosely coupled system）。在松耦合系統中，只有一小部分變化的磁場能被接收線圈接收，這就意味著松耦合系統會產生更多的電磁泄漏，因此不適用於對EMI和EMF高要求的應用場景。
Loosely coupled systems trade-off larger distance at the cost of lower power transfer efficiency and higher electromagnetic emissions. This may be suitable choice in applications where tightly aligned coils is impractical, but less suitable for applications with tight EMI or EMF of efficiency requirements.
松耦合系統可以調節長距離，低效率和高電磁泄漏三者之間的關係。這使松耦合系統可適用在「緊耦合的線圈陣列」不可行的應用場景，但是對於EMI和EMF要求過高或者對效率要求過高的應用場景，松耦合系統則很不適用。
Tightly coupled systems, because of their higher efficiency, tend to produce less heat which is an advantage is products with tight thermal budgets such as modern smartphones.
緊耦合系統，由於能量傳遞更高效，因此產生熱量較少，適合對發熱控制要求較高的設備，例如我們常用的手機等。
For the definition of coupling factor see:
另外關於耦合相關係數的解釋請參見以下網頁：http://www.wirelesspowerconsortium.com/technology/coupling-factor.html
The transmit and receive coils are tightly coupled when (a) the coils have the same size, and (b) the distance between the coils is much less than the diameter of the coils.
當發射線圈和接收線圈大小相同，並且線圈之間的距離遠遠小於線圈直徑時，就會產生緊耦合。
Loosely coupled coils or operate with significantly different coil sizes, or operate at larger distance.
當發射線圈和接收線圈尺寸有明顯差距或者距離很遠時，會產生松耦合。
Choice 2: Operate the coils at resonance or off-resonance?
選擇2：使線圈處於磁共振狀態，還是非磁共振狀態?
From the beginning of inductive power transmission, resonant circuits have been used to enhance the efficiency of power transmission. As early as 1891, Nicola Tesla used resonance techniques in his first experiments with inductive power transmission. Systems with a low coupling factor generally use a resonant receiver and resonant transmitter to improve power transfer efficiency.
在早期的磁感應能量傳輸系統中，共振電路就被用來提高能量傳輸的效率。早在1891年，尼古拉-特斯拉就將磁共振技術應用在磁感應能量傳輸中。通常在弱耦合系統中，使用共振的接收器和共振的發射裝置以提高傳輸效率。
For technical details see:
技術背景請參考以下網頁：http://www.wirelesspowerconsortium.com/technology/resonant-coupling.html
You might expect that operating tightly coupled coils at resonance offers the best performance. That combination, however, is not used in practice because two tightly coupled coils cannot be both in resonance at the same time. This is one of the counter-intuitive effects that make power electronics such an interesting subject.
你可能十分期待，將緊耦合技術與共振原理相結合以得到最好的能量傳輸效率。但是，緊耦合+磁共振，並沒有在實際中應用，因為緊耦合線圈不能同時產生共振。這是電力電子科學中一個比較有趣的反直覺效應。
Most Qi transmitters use tight coupling between coils. In that configuration, the best results are achieved by operating the transmitter at a frequency that is slightly different from the resonance frequency of the Qi receiver. Off-resonance operation gets you the highest amount of power at the best efficiency.
大多數Qi充電器通過線圈之間產生的緊耦合運轉。在這樣的前提下，最好的結果就是調節發射端的工作頻率，使其與接收端的共振頻率有一點細微的差別。因為無法達到共振頻率，只能無限接近。非共振傳輸會提供最強最高效的表現。
chioce3: Single coil or multi-coil?
選擇3：單線圈還是多線圈？
Tightly coupled coils are sensitive to misalignment. That』s why most Qi transmitters use multiple coils. This increases the complexity of the transmitter design, but improves the horizontal (X, Y) freedom of positioning. Coil arrays can cover large areas. See, for example, ConvenientPower』s WoW5 transmitter.
緊耦合線圈對線圈之間的對準程度要求很高。這就是為什麼大多數Qi充電器使用多線圈的原因。多線圈極大地增加了充電器的設計要求，但是接收端就有了更強的平面自由度，不用太注意線圈之間對準的問題。線圈陣列可以覆蓋很大的面積，比如ConvenientPower公司的WoW5無線充電器。
Another advantage of multi-coil systems is that they help localize the magnetic flux, reducing EM emissions, and make it possible to charge multiple receivers concurrently.
另一個多線圈的優勢在於更好的聚集磁通量，減少電磁場泄露，使多設備同時充電成為可能。
Here are some examples of transmitters that use overlapping coils
下面是一些應用重疊線圈的無線充電器
Coils dont need to overlap either. Solutions with non-overlapping coils can be easier easy to assemble.
當然線圈也並不是必須重疊放置，「無重疊方案」可以更方便無線充電器的組裝。
Multi-coil transmitters can charge several receivers at the same time, simply by powering the coils underneath the receiver.
多線圈充電器只需要給裡面的線圈供電就可以做到同時給多個設備充電。
Multi-coil transmitters also allow the wireless power ecosystem to scale with increasing power levels that devices demand, by powering multiple coils underneath the receiver. The first smart phones needed 3W, todays require over 7.5W and growing. We also now have tablets, ebooks readers, ultrabooks which need from 10-30W. Multi-coil systems transmit the power exactly where it is needed in a safe, efficient and controlled manner guaranteeing scalability as devices get more and more power hungry.
多線圈充電器只需要加強給線圈的能量就可以加大充電的功率，以適應多種設備的功率要求。最早的智能電話需要3瓦來充電，現在需要超過7.5瓦而且還在增長。平板電腦，電子書，超級本會需要10到30瓦的電量。多線圈充電器可以安全有效的控制供電，並且擴展性極強。
A loosely coupled system can achieve multi-device charging with a single transmitter coil, provided it is much larger than the receiver coils and the provided the receivers can tune themselves independently to the frequency of the single transmitter coil.
松耦合系統可以用一個發射線圈達到為多個設備充電的需求，但是要求發射線圈遠遠大於接收線圈，並且要求接收裝置都能夠單獨調節自身的頻率以適應發射線圈的頻率，
The table below provides a summary of the possible transmitter configurations:
下面的表格提供了所有可能的充電形式：
As you can see, there is no optimum design. The choice of architecture will depend on the application requirements. Is efficiency important? Is EMI (electromagnetic interference) a concern? Do you need a large Z distance? Is cost the key issue? Depending on your priorities, the optimum will be different
可以看到，並沒有最完美的設計。工程師會根據不同的應用場景選擇其結構。是效率重要？是考慮EMI？還是需要更大的線圈間距？成本是不是重要的因素？對上述各因素的考慮優先順序不同，最優設計的方案就不同。
Qi gives you the possibility to choose what is best for your application
Qi提供了讓你選擇最適合你的可能性。
All Qi receivers have a well-defined resonance frequency and can operate at resonance. The Qi transmitter products that are in the market today operate off-resonance, with tight coupling, because that combination provides both high power transfer and high efficiency. Most Qi transmitter products use multiple coils because they provide a better user experience.
所有Qi接收器的共振都有明確的共振頻率，並且線圈都是可以被調節在共振的狀態中。如今市場上的Qi充電器選擇緊耦合、非磁共振是因為這樣的結合能提供最大，最高效的能量傳輸。大多數Qi充電產品使用多線圈方案是因為能提供更好的用戶體驗感。
At the Consumer Electronics Show in January, and at Mobile World Congress in February, you could see the first Qi transmitter products that operate at larger distance, loosely coupled, and at resonance. These resonant Qi transmitters are compatible with all Qi phones out there today. Otherwise we would not call it a Qi transmitter: If you see the Qi logo, you can be sure that the product is compatible with all other Qi products.
今年一月份的消費者電子展上，二月的世界手機大會，我們看到第一款可以遠距離供電的松耦合、共振充電設備。這些磁共振Qi充電器可以與如今所有Qi手機匹配。否則的話也不能叫做Qi充電器：如果你看到Qi的標誌，你大可放心，這個產品一定會與你的Qi手機匹配。
A4WP
The Alliance for Wireless Power offers only one choice: 「single coil, loosely coupled, resonant」. That configuration is not optimal for all applications. The WPC believes that product developers need more options to choose from. The solution 「single coil, loosely coupled, resonant」 is just one of the options offered by the Wireless Power Consortium.
A4WP無線充電標準只提供了「單線圈，松耦合，共振」的選擇，但是這樣的設計並不適用於所有的應用場景。WPC相信產品研發者需要更多選擇。然而，單線圈，松耦合，共振的方式只是其中一種。
The solution offered by the A4WP is not compatible with the millions of Qi phones and tablets that are already in the market. The WPC has demonstrated that it is possible to make loosely coupled resonant transmitters that are compatible with all these of Qi phones and tablets. There is no technical justification for incompatibility.
A4WP的解決方案並不適用於如今已在市場上的千千萬萬的Qi手機和手提電腦。如今，WPC已經演示了未來這種松耦合、單線圈、磁共振的解決方案，並且會和你的Qi手機以及平板電腦匹配。
----------------------------------轉載請註明轉自麥極客 麥極客多功能無線充電技術領導者~
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