Wireless Power Transfer: Survey and Roadmap

Wireless power transfer (WPT) technologies have been widely used in many areas, e.g., the charging of electric toothbrush, mobile phones, and electric vehicles. This paper introduces fundamental principles of three WPT technologies, i.e., inductive coupling-based WPT, magnetic resonant coupling-based WPT, and electromagnetic radiation-based WPT, together with discussions of their strengths and weaknesses. Main research themes are then presented, i.e., improving the transmission efficiency and distance, and designing multiple transmitters/receivers. The state-of-the-art techniques are reviewed and categorised. Several WPT applications are described. Open research challenges are then presented with a brief discussion of potential roadmap

A Study of Multi-Layer Spiral Inductors for Remote Powering of Implantable Sensors

An approach based on multi-layer spiral inductors to remotely power implantable sensors is investigated. As compared to single-layer inductors having the same area, multi-layer printed inductors enable a higher efficiency (up to 35% higher) and voltage gain (almost one order of magnitude higher). A system conceived to be embedded into a skin patch is designed to verify the performance. The system is able to transmit up to 15 mW over a distance of 6 mm and up to 1.17 mW where a 17 mm beef sirloin is placed between the inductors. Furthermore, the system performs downlink communication (up to 100 kbps) and uplink communication based on the backscattering technique (up to 66.6 kbps). Long-range communication is achieved by means of a bluetooth module

Evaluation of wireless charging systems from the point of view of energy transfer in electric mobility

openA basic wireless charging system consists of some essential components as shown in Figure 1.1 The AC current power supply coming from the grid is converted by an AC converter into a DC current power supply. At this point the rectified current is converted via an inverter into high frequency AC to drive the transmission coil through a compensation network. The high-frequency current in the transmission coil generates an alternating magnetic field, which induces an alternating voltage on the receiving coil. At the end, the AC power supply is rectified to charge the battery.A basic wireless charging system consists of some essential components as shown in Figure 1.1 The AC current power supply coming from the grid is converted by an AC converter into a DC current power supply. At this point the rectified current is converted via an inverter into high frequency AC to drive the transmission coil through a compensation network. The high-frequency current in the transmission coil generates an alternating magnetic field, which induces an alternating voltage on the receiving coil. At the end, the AC power supply is rectified to charge the battery

Finite Element Modeling and Analysis of High Power, Low-loss Flux-Pipe Resonant Coils for Static Bidirectional Wireless Power Transfer

This paper presents the optimal modeling and finite element analysis of strong-coupled, high-power and low-loss flux-pipe resonant coils for bidirectional wireless power transfer (WPT), applicable to electric vehicles (EVs) using series-series compensation topology. The initial design involves the modeling of strong-coupled flux-pipe coils with a fixed number of wire-turns. The ohmic and core loss reduction for the optimized coil model was implemented by creating two separate coils that are electrically parallel but magnetically coupled in order to achieve maximum flux linkage between the secondary and primary coils. Reduction in the magnitude of eddy current losses was realized by design modification of the ferrite core geometry and optimized selection of shielding material. The ferrite core geometry was modified to create a C-shape that enabled the boosting and linkage of useful magnetic flux. In addition, an alternative copper shielding methodology was selected with the advantage of having fewer eddy current power losses per unit mass when compared with aluminum of the same physical dimension. From the simulation results obtained, the proposed flux-pipe model offers higher coil-to-coil efficiency and a significant increase in power level when compared with equivalent circular, rectangular and traditional flux-pipe models over a range of load resistance. The proposed model design is capable of transferring over 11 kW of power across an airgap of 200 mm with a coil-to-coil efficiency of over 99% at a load resistance of 60 Ω

A wearable all-printed textile-based 6.78 MHz 15 W-output wireless power transfer system and its screen-printed Joule heater application

While research in passive flexible circuits for Wireless Power Transfer (WPT) such as coils and resonators continues to advance, limitations in their power handling and low efficiency have hindered the realization of efficient all-printed high-power wearable WPT receivers. Here, we propose a screen-printed textile-based 6.78 MHz resonant inductive WPT system using planar inductors with concealed metal-insulator-metal (MIM) tuning capacitors. A printed voltage doubler rectifier based on Silicon Carbide (SiC) diodes is designed and integrated with the coils, showing a power conversion efficiency of 80-90% for 2-40 W inputs over a wide load range. Compared to prior wearable WPT receivers, it offers an order of magnitude improvement in power handling along with higher efficiency (approaching 60%), while using all-printed passives and a compact rectifier. The coils exhibit a simulated Specific Absorption Rate (SAR) under 0.4 W/kg for 25 W received power, and under 21∘C increase in the coils' temperature for a 15 W DC output. Additional fabric shielding is investigated, reducing harmonics emissions by up to 17 dB. We finally demonstrate a wirelessly-powered textile-based carbon-silver Joule heater, capable of reaching up to 60∘C at 2 cm separation from the transmitter, as a wearable application which can only be wireless-powered using the proposed system

First self-resonant frequency of power inductors based on approximated corrected stray capacitances

Inductive devices are extensively employed in power electronic systems due to their magnetic energy storage and power transfer capabilities. The current trend is towards increasing the frequency of operation in order to reduce the size of the magnetic components, but the main drawback is that the parasitic capacitance effect can become significant, and degrade the performance of the system. This work analyses the influence of this stray capacitance, and considers how to improve the performance of the device. In general, the impact of the stray capacitance on a magnetic component can be reduced by two methods: reducing the parasitic capacitance between turns of the winding or, alternatively, modifying the arrangement of the connection between turns. To evaluate the last option, an approximated expression of the first self-resonant frequency of the magnetic device is proposed. This gives a rapid assessment of the performance of different devices maintaining the overall equivalent inductance. The proposed expression accounts for the influence of the connection between turns in the bandwidth of the component. Finally, some numerical results are verified with planar coils manufactured on two-layer printed circuit boards

Design of Wireless Power Transfer and Data Telemetry System for Biomedical Applications

With the advancement of biomedical instrumentation technologies sensor based remote healthcare monitoring system is gaining more attention day by day. In this system wearable and implantable sensors are placed outside or inside of the human body. Certain sensors are needed to be placed inside the human body to acquire the information on the vital physiological phenomena such as glucose, lactate, pH, oxygen, etc. These implantable sensors have associated circuits for sensor signal processing and data transmission. Powering the circuit is always a crucial design issue. Batteries cannot be used in implantable sensors which can come in contact with the blood resulting in serious health risks. An alternate approach is to supply power wirelessly for tether-less and battery- less operation of the circuits.Inductive power transfer is the most common method of wireless power transfer to the implantable sensors. For good inductive coupling, the inductors should have high inductance and high quality factor. But the physical dimensions of the implanted inductors cannot be large due to a number of biomedical constraints. Therefore, there is a need for small sized and high inductance, high quality factor inductors for implantable sensor applications. In this work, design of a multi-spiral solenoidal printed circuit board (PCB) inductor for biomedical application is presented. The targeted frequency for power transfer is 13.56 MHz which is within the license-free industrial, scientific and medical (ISM) band. A figure of merit based optimization technique has been utilized to optimize the PCB inductors. Similar principal is applied to design on-chip inductor which could be a potential solution for further miniaturization of the implantable system. For layered human tissue the optimum frequency of power transfer is 1 GHz for smaller coil size. For this reason, design and optimization of multi-spiral solenoidal integrated inductors for 1 GHz frequency is proposed. Finally, it is demonstrated that the proposed inductors exhibit a better overall performance in comparison with the conventional inductors for biomedical applications

Remote Powering and Communication of Implantable Biosensors Through Inductive Link

Nowadays there is an increasing interest in the field of implantable biosensors. The possibility of real-time monitoring of the human body from inside paves the way to a large number of applications and offers wide opportunities for the future. Within this scenario, the i-IronIC project aims to develop an implantable, low cost, health-care device for real-time monitoring of human metabolites. The contribution of this research work to the i-IronIC project consists of the design and realization of a complete platform to provide power, data communication and remote control to the implantable biosensor. High wearability of the transmitting unit, low invasivity of the implanted electronics, integration of the power management module within the sensor, and a reliable communication protocol with portable devices are the key points of this platform. The power is transmitted to the implanted sensor by exploiting an inductive link. Simulations have been performed to check the effects of several variables on the link performance. These simulations have finally confirmed the possibility to operate in the low megahertz range, where tissue absorption is minimum, even if a miniaturized receiving inductor is used. A wearable patch has been designed to transmit power through the body tissues by driving an external inductor. The same inductive link is used to achieve bidirectional data communication with the implanted device. The patch, named IronIC, is powered by lithium-ion polymer batteries and can be remotely controlled by means of a dedicated Android application running on smartphones and tablets. Long-range communication between the patch and portable devices is performed by means of Bluetooth protocol. Different typologies of receiving inductors have been designed to minimize the size of the implantable device and reduce the discomfort of the patience. Multi-layer, printed spiral inductors and microfabricated spiral inductors have been designed, fabricated and tested. Both the approaches involve a sensibly smaller size, as compared to classic “pancake” inductors used for remote powering. Furthermore, the second solution enables the realization of the receiving inductor directly on the silicon substrate hosting the sensor, thus involving a further miniaturization of the implanted device. An integrated power module has been designed and fabricated in 0.18 μm CMOS technology to perform power management and data communication with the external patch. The circuit, to be merged with the sensor readout circuit, consists of an half-wave voltage rectifier, a low-dropout regulator, an amplitude demodulator and a load modulator. The module receives the power from the implanted inductor and provides a stable voltage to the sensor readout circuit. Finally, the amplitude demodulator and the load modulator enable short-range communication with the patch

Applications of Antenna Technology in Sensors

During the past few decades, information technologies have been evolving at a tremendous rate, causing profound changes to our world and to our ways of living. Emerging applications have opened u[ new routes and set new trends for antenna sensors. With the advent of the Internet of Things (IoT), the adaptation of antenna technologies for sensor and sensing applications has become more important. Now, the antennas must be reconfigurable, flexible, low profile, and low-cost, for applications from airborne and vehicles, to machine-to-machine, IoT, 5G, etc. This reprint aims to introduce and treat a series of advanced and emerging topics in the field of antenna sensors

Power Amplifiers for Electronic Bio-Implants

Healthcare systems face continual challenges in meeting their aims to provide quality care to their citizens within tight budgets. Ageing populations in the developed world are perhaps one of the greatest concerns in providing quality healthcare in the future. The median age of citizens in economically developed regions is set to approach 40 years by the year 2050, and reach as high as 55 years in Japan. This trend is likely to lead to strained economies caused by less revenue raised by smaller workforces. Another effect of ageing populations is the need of further care in order to remain healthy. This care varies from frequent check-ups to condition monitoring, compensation for organ malfunction and serious surgical operations. As a result of these trends, healthcare systems will face the task of servicing more people with more serious and expensive health services, all using less available funds. Effort is being focused on running cheaper and more effective healthcare systems and the development of technology to assist in this process is a natural research priority