Closed-Loop Automatic Frequency Control of Wireless Power Transfer


Electronics - Sensors & Instrumentation
Electronics - Power Management


This technology has been developed in response to the state-of-the-art wireless power transfer systems, especially, in response to a need that has not been fully solved by current wireless power transfer systems. Magnetic resonance coupling is used to extend the effective charging range of inductive coupling from only a few millimeters to several centimeters, or even several feet. However, the sensitivity to operating frequency becomes highly pronounced with resonant coupling, and a theoretical optimum efficiency can only be achieved at one fixed antenna distance called critical coupling. At closer spacings, the efficiency will drop significantly due to a shift in the resonance frequency from over-coupling. Foreign conductive object proximity will also shift the resonance frequency and lower the efficiency. Accordingly, this technology was developed to track the resonance frequency and maintain high overall efficiency in the event of any shift in resonance frequency.


The frequency of operation for maximum power transfer efficiency can be tracked by this technology under different conditions, without using any communication systems or control algorithms. The technology implements a frequency tracking feedback loop entirely in analog electronics, and is robust over the entire range of antenna couplings from over-coupled to under-coupled conditions. For example, changes in antenna distance, antenna misalignment, use of different-sized antennas, conductive object proximity, and transmission media with variable dielectric properties could all shift the resonance frequency and be mitigated by this technology.


Any wirelessly-powered application where battery life or overall efficiency must be maximized could benefit, for example: biomedical implants, electric toothbrushes, TV, lighting, wall switches, heating systems, laptops, tablets, cell phones, sensors, wearable devices, RFID, off-shore energy harvesting, electric bikes, robot manipulation, induction motors, high speed trains, and electric vehicles.

Market Trends & Opportunities

Wireless Charging Market Report, published by Allied Market Research, forecasts that the global market is expected to reach $37.2 billion by 2022, growing at a CAGR of 44.7% during the period 2016-2022. The main driving factors are: rising demand for smartphones & other wireless computing devices, necessity of a common charging platform, increased demand for Electric Vehicles, and booming Internet of Things (IoT) & semiconductor market. This invention is validated with a working prototype supplying 15-20dBm over 5-90mm using 40mm diameter antennas, but can be easily adapted and scaled to different applications.

Unique Value Proposition

Maximum power transfer efficiency can be tracked even when subject to variations of charging distance, misalignment of coupled antennas or conductive object proximity. This technology achieves automatic resonance frequency tuning without sophisticated software control algorithms or communication systems, which can be expensive to implement in power, materials, and complexity.

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