Wireless charging is a technology of transmitting power through an air gap to electrical devices for the purpose of energy replenishment. The recent progress in wireless charging techniques and development of commercial products have provided a promising alternative way to address the energy bottleneck of conventionally portable battery-powered devices. However, the incorporation of wireless charging into the existing wireless communication systems also brings along a series of challenging issues with regard to implementation, scheduling, and power management. In this paper, we present a comprehensive overview of wireless charging techniques, the developments in technical standards, and their recent advances in network applications. In particular, with regard to network applications, we review the static charger scheduling strategies, mobile charger dispatch strategies and wireless charger deployment strategies. Additionally, we discuss open issues and challenges in implementing wireless charging technologies. Finally, we envision some practical future network applications of wireless charging.

Wireless Charging Technologies: Fundamentals, Standards, and Network Applications

Electrically-small antennas present high-Q impedances characterized by large reactances and small radiation resistances. For such antennas, the effectiveness of passive matching is severely limited by gain-bandwidth theory, which predicts narrow bandwidths and/or poor gain. With receivers, the inability to resolve this impedance mismatch results in poor signal-to-noise (S/N) ratio, as compared to using a full-size antenna. With transmitters, the consequence is poor power efficiency. However, in many applications full-size antennas are impractical, and a means is required to effectively match their electrically-small counterparts. This paper presents the technique of non-Foster impedance matching, which employs active networks of negative inductors and capacitors to bypass the restrictions of gain-bandwidth theory. We first review the origins and development of non-Foster impedance matching, and then present experimental results for the non-Foster impedance matching of electrically-small dipoles and monopoles. For receivers, our best measurements on the antenna range demonstrate up to 20 dB improvement in S/N over 20-120 MHz; for transmitters, we show a power efficiency improvement which exceeds a factor of two over an 5% bandwidth about 20 MHz with an average signal power of 1 W to the radiation resistance.

Non-Foster Impedance Matching of Electrically-Small Antennas

소형 안테나 ( Small Antennas )

Indicia-reading systems include an auxiliary reading apparatus with wireless charging capability. The systems are configured to couple, transfer, and receive energy wirelessly between a base charging station and auxiliary indicia reader via resonating coils that include an impedance matching network. Wireless charging capability can save space at the point-of-sale and add convenience for the operator.

Indicia-reading system

A method and a wireless power transmitter are provided for transmitting wireless power to at least one wireless power receiver. The method includes setting, by the wireless power transmitter, a search channel to be used for communication with the at least one wireless power receiver; detecting at least one of an energy level and a Received Signal Strength Indication (RSSI) value of a signal received on the search channel; and determining whether to designate the search channel as a communication channel based on the detection results.

Apparatus and method for transmitting wireless power

Provided is a method for controlling a wireless power transmitter transmitting wireless power to at least one wireless power receiver. The method for controlling a wireless power transmitter, according to the present invention, can comprise the steps of: receiving information related to a wireless power receiver from at least one of each of the wireless power receivers; and controlling each of a plurality of power transmitting units included in the wireless power transmitter on the basis of the information related to the wireless power receiver.

Wireless power transmitter and method for controlling wireless power transmitter

When the size of an antenna is electrically small, the antenna is neither efficient nor a good radiator because most of the input power is stored in the reactive near-field region and little power is radiated in the far-field region. As demonstrated in [1]- [2], the radiation quality factor of small antennas is definitely high. In other words, the input impedance of small antennas is considerably reactive. To reduce the radiation quality factor in the whole or partial frequency range of interest, it is important to increase the radiation resistance and/or reduce the reactance of the antenna. Hence, it is necessary to modify the antenna to reduce the reactance of the antenna and/or add impedance matching networks (MNs) to maximize the transfer of power from a resistive source to the highly reactive antenna.

Non-Foster impedance matching of electrically small antennas

A wireless power transmission apparatus includes resonators configured to transmit a power wirelessly to another resonator, and a controller configured to control a current magnitude and/or a voltage magnitude of a power to be provided to each of the resonators. The apparatus further includes a feeder configured to provide the power to each of the resonators.

Wireless power transmission apparatus and wireless power transmission method

An apparatus and a method for charge control are provided. The apparatus for charge control may include an integrated direct current-to-direct current (DC/DC) converter configured to step up an output voltage level of a load to be greater than or equal to a supply voltage level set in a power amplifier, and the power amplifier configured to convert a direct current (DC) voltage stepped up by the integrated DC/DC converter into an alternating current (AC) voltage based on a resonant frequency, and to amplify the converted AC voltage. The apparatus for charge control may include a rectification unit configured to convert an AC power received wirelessly into a DC power; and a DC/DC converter configured to step down a voltage level of the DC power to a voltage level required by a load in the receiving mode.

Apparatus and method for charge control in wireless charging system

A wireless power receiver includes a power receiver configured to wirelessly receive power, and including a direct current (DC)-to-DC (DC/DC) converter, and a power detector configured to detect power detection information from a front end of the DC/DC converter.

Keum Su Song

Papers

Wireless power transmitter and method for controlling wireless power transmitter

Non-Foster impedance matching of electrically small antennas

Wireless power transmission apparatus and wireless power transmission method

Apparatus and method for charge control in wireless charging system

Wireless power transmission system with ability to determine charging circumstances