Introduction to Wireless Power Charging Coils

Wireless Power Charging is becoming more and more common in new gadgets like smart phones, tablets and laptops. With this pace of technological growth, one can certainly assume in the future that many domestic electronic devices will be charged or powered wirelessly. The number of manufacturers of wireless charging coils and control circuit chips are also expected to grow to meet increasing consumer demand.

One may ask, why is the consumer market of interest to us? All known technologies have been mostly driven by the consumer electronic market, subsequently the Industrial and other similar sectors have taken advantages of the “went through learning curve” to lower their design time.

The purpose of this blog post is to explain the methodology on how to change wireless power charging coils manufactured by Würth Elektronik eiSos on a Demo Circuit incorporating receiver control chip LTC4120 manufactured by Linear Technology.

Wireless Power Transfer Principle

The wireless power is transferred from transmitter to receiver coil using more than a century old principle called inductive coupling. However, recent developments prove that when two resonant circuits resonating at the same frequency, designed with minimal loss and absorption (High Q) are brought into close proximity (near field area), that due to evanescent wave coupling the energy transferred from transmitter to receiver are at a high efficiency.

In order for a wireless power charging system to work efficiently, the frequency of both transmitter and receiver is required to be tuned to the same frequency. For different inductance value of charging and coupling coil, other associated parts of the circuit are necessary to be changed as well in order to get the same resonant frequency. This document also explains the unique advantage of using Würth Elektronik wireless power charging coils.

Würth Elektronik Wireless Power Charging Coils

Würth Elektronik eiSos is a member of Wireless Power Consortium (WPC) and Alliance for Wireless Power (A4WP) now known as “Rezence” and has been developing various wireless transmitter and receiver coils compliant with Qi standard in proprietary solution.

Transmitter and Receiver Coils

Following are the Würth Elektronik eiSos transmitter and receiver wireless coils considered for evaluation:

Transmitter coils

Receiver coils

To learn more about the Linear Technology LT3748 flyback controller, check back with our blog or check out the WE-FB series available from Wurth Electronics Midcom.

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