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Wireless Power Transfer Resonance Coupling Amplification by Load-Modulation Switching Controller
Dukju Ahn,Songcheol Hong Institute of Electrical and Electronics Engineers 2015 IEEE transactions on industrial electronics Vol. No.
<P>This paper proposes that transmitter-to-receiver resonator efficiency can be enhanced by the novel combination of resonator and switching controller at the receiver side. More specifically, the switching controller modulates the load resistance such that the receiver resonance is amplified. This increases the loaded-Q, reflected resistance, and, subsequently, overall efficiency and distance range. The efficiency and distance range are superior than resonator-only receivers, despite of losses from the switching controller itself. This breaks the common routine that typical switching converters only lower the power flow and efficiency when they are inserted in wireless power chain. Moreover, the scheme solves the common problem of load-variation-induced efficiency degradation. More specifically, if the present load value is deviated from optimal point, the proposed controller adjusts the effective load resistance to amplify the reflected resistance. The loaded-Q amplification is easily controlled simply by changing the duty ratio of switching controller. This is more feasible than traditional impedance transformation network whose control requires large array of capacitor-switch matrix or movement of coil position. The efficiencies with and without the switching-controlled resonance amplification are 60.2% and 51.7%, respectively, for a 20-W loading at 15-cm distance for a 20 cm × 16 cm receiver.</P>
Ahn, Dukju,Kim, Seongmin,Kim, Sang-Won,Moon, Jungick,Cho, Inkui IEEE 2017 IEEE TRANSACTIONS ON POWER ELECTRONICS - Vol.32 No.9
<P>The paper proposes a method to suppress the anticurrent and magnetic canceling in a dual-band transmitter (Tx) and receiver (Rx) for wireless power transfer. The problem of intracoupling between the two coils in a dual-band resonator is analyzed. During 6.78-MHz operation, the intracoupling causes antidirectional current at 200-kHz coil which cancels the magnetic field and degrades efficiency. To solve the problem of antidirectional current, a new resonator design method is proposed. The proposed technique suppresses the 6.78-MHz anticurrent by specially selecting the impedance values and coil-winding direction that manipulate the magnitude and phase of 6.78-MHz voltage, such that total voltage across 200-kHz path is zero. One of the advantages is that the spatial separation between 6.78-MHz coil and 200-kHz coil can be reduced, which allows the maximum diameter for inner coil. Also, smaller discrete inductor can be used. The two coils share an inverter (or a rectifier), thus minimizing the number of inverter and rectifier. The 24-W system with dual-band Tx achieves 70.3% and 70.8% efficiencies at 6.78 MHz and 200 kHz, respectively, whereas the system with dual-band Rx achieves 66.3% and 74.3% at 6.78 MHz and 200 kHz, respectively. The efficiency improvement due to anticurrent suppressing is 4.8 similar to 23.6%.</P>
Wireless Power Transfer With Automatic Feedback Control of Load Resistance Transformation
Ahn, Dukju,Kim, Seongmin,Moon, Jungick,Cho, In-Kui Institute of Electrical and Electronics Engineers 2016 IEEE transactions on power electronics Vol. No.
<P>This paper proposes a wireless power transfer with automatic feedback control of load resistance transformation to maintain high efficiency over wide variations of coupling current and load current. The receiver (Rx) first determines the desired current level of transmitter (Tx) coil such that the receiver-side converter can transform the load resistance into optimum effective resistance, based on load current and Tx-to-Rx distance information. The determined Tx coil current data are sent to the transmitter, which then adjusts the Tx coil current accordingly. In this way, the effective resistance transformed by the receiver-side converter remains optimum under the variations of distance and load current. One of the advantages of the proposed automatic feedback control is faster response and simple hardware because it does not use operating point sweep and observation. The receiver-side switching converter also incorporates the ability to send data from receiver to transmitter by modulating the duty cycle of converter at data frequency, eliminating the need for separate RF communication hardware. This proposed communication does not require shunt current dissipation from dc output to ground, resulting in low loss. Experimental result demonstrates that the system maintains high efficiency under wide variations of coupling and load current.</P>
Dukju Ahn,Songcheol Hong Institute of Electrical and Electronics Engineers 2014 IEEE transactions on industrial electronics Vol. No.
<P>This paper proposes a novel resonator structure for efficiency and transferred power improvements: a transmitter (a receiver) that consists of two strongly coupled resonators. The two strongly coupled resonators are embedded within a transmitter device (a receiver device) and behave as a single resonator with enhanced performances. Unlike the conventional four-coil system, the first and the fourth resonators are also designed to have high loaded-Q and maximum cross couplings. Therefore, the first and the fourth resonators also take part in the coupled resonance with opposite-side resonators. This provides additional energy exchange path. The exact design guidelines are provided for each different resonance topology from analytical derivation. It is analyzed and experimentally demonstrated that the efficiency and the transferred power are increased by the proposed two-resonator technique. For a 30 cm × 25 cm parallel-resonant transmitter and an 18 cm × 16 cm parallel-resonant receiver at 13-cm distance, the efficiency and the transferred power with the proposed technique are 65.2% and 17.2 W, respectively, whereas those values without the proposed technique are only 37.3% and 6.2 W.</P>
A K-Band High-Gain Down-Conversion Mixer in 0.18 <tex> $\mu$</tex>m CMOS Technology
Dukju Ahn,Dong-Wook Kim,Songcheol Hong IEEE 2009 IEEE microwave and wireless components letters Vol.19 No.4
<P>A high gain CMOS down conversion mixer with a gain enhancement technique is presented. This technique includes negative resistance generation, parasitic capacitance cancellation and current-injection. These are implemented with an additional circuitry. This mixer has a conversion gain of 9.12 dB, input 1 dB compression point of -11 dBm at 24 GHz, while consuming 16.2 mW from 1.8 V supply. Between 22 and 26 GHz, the LO-to-RF and RF-to-LO isolations are better than 35 dB and 26 dB, respectively.</P>
Dukju Ahn,Mercier, Patrick P. IEEE 2016 IEEE TRANSACTIONS ON POWER ELECTRONICS - Vol.31 No.7
<P>This paper proposes a wireless power transfer (WPT) transmitter that can concurrently operate at 200 kHz and 6.78 MHz in order to simultaneously power two receivers operating with different frequency standards. Unlike a dual-resonant single-coil design, the use of two separate coils decouples the design for one frequency from the other, enabling independent selection of inductance and Q-factor to simultaneously maximize efficiency at both frequencies. The two coils then support separate coil drivers, enabling concurrent multistandard operation. Dual-band operation is achieved in the same area as an equivalent single-band design by placing a low-frequency coil within the geometry of a high-frequency coil, where the outer diameter of inner coil is sacrificed only by 1.2 cm in a 12.5 × 8.9-cm<SUP>2</SUP> design. Circuit analysis is presented to identify the eddy current between the two Tx coils and its associated loss, after which an eddy-current filter design is proposed. To validate the proposed design, a dual-mode transmitter, along with two receivers designed at 6.78 MHz and 200 kHz, respectively, have been fabricated. At 25-mm separation, the system is able to simultaneously deliver 9 and 7.4 W with efficiencies of 78% and 70.6% at 6.78 MHz and 200 kHz, respectively.</P>