无线充电是什么原理？为什么现在手机都开始使用无线充电了？
这几年越来越多的智能手机开始配备无线充电功能，比如iPhone Xs、三星S9、小米MIX 3等等，所以有些小伙伴对这个功能应该不陌生了。
可是无线充电毕竟是一项新技术，相比传统的数据线充电，它还是有点颠覆了我们的看法，大多数人的疑问是：没有数据线，那手机和充电器之间是如何通过电流传输的呢？
目前无线充电方式主要有四种：电磁感应式充电、磁场共振式充电、无线电波式充电、电场耦合式，各种充电方式的技术方案也不一样。
电磁感应无线充电，是利用供电方（无线充电板）和受电方（手机）上的感应磁铁之间产生的感应磁通量，将磁力转换为电力再进行传输。这种充电方式的有点是，设备要求的电路结构相对比较简单，充电设备可以做到小型化、而且造价便宜，充电效率相对来说也会高一点。不过也存在着传输距离短、充电效果容易受到摆放位置偏离的影响。
磁场共振无线充电稍微不同，它利用供电方和受电方两端的谐振器产生磁场共振，同样是将磁力转换为电力，从而进行电力传输。只要两个设备是在一个相同的频率上产生振荡，双方就可以交换能量。其优点是适用于长距离的传输，但存在是低效率的弊端，目前还在研究中，并未投放市场。
无线电波式充电和前面提到的两种充电方式有所不同，它通过在供电方配置无线电波的发射设备，在受电方配置无线电波的接纳设备，以直流电压输出与输入的方式、从而进行电力传输。其优点是传输间隔中等传输速度较快，但缺点是安稳性、安全性都比较低，而且需要一定的成本投入研发。
电场耦合式无线充电，原理是通过沿垂直方向耦合两组非对称偶极子而产生的感应电场来传输电力。适合短距离充电，转换效率也高，位置可以不固定；不过缺点是需要大体积的设备、功率也较小。
因此，目前这四种无线充电方式中，电磁感应式无线充电的方案最为成熟，也是被商用最广泛的，比如我们手机需要用得到的各种无线充电器，就是利用了这种技术方案。不过如前面所述，它也存在着传输距离短、充电效率易受到摆放位置偏离影响的缺陷，因此还被吐槽为“伪无线”充电。
不过不管怎么说，就现在的技术水平来说，电磁感应式无线充电方案是最值得采用的，它也给智能手机的充电方式提供了一个解决方案，依然是利大于弊。而且提高充电便捷化的同时，也在某种程度上统一了各类充电器，减少了资源浪费。在未来，无线充电将成为一种趋势。
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