• Journal of electromagnetic engineering and science
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• v.15 no.3
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• pp.194-198
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• 2015

Magnetic resonant coupling is more efficient than inductive coupling for transferring power wirelessly over a distance. However, a conventional resonant wireless power transfer (WPT) system requires a transmitter and receiver pair in exactly coaxial positions. We propose a resonator that can serve as an omnidirectional WPT system. A magnetic field will be generated by the current flowed through the transmitter. This magnetic field radiates omnidirectionally in the x-y plane because of the crisscross structure characteristic of the transmitter. The proposed resonator is demonstrated by using a single port. To check the received S21 and transfer efficiency, we moved the receiver around the transmitter at different distances (50-350 mm). As a result, the transmission efficiency is found to be 48%-54% at 200 mm.

• Journal of IKEEE
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• v.22 no.3
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• pp.846-849
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• 2018

Wireless power transfer (WPT) is the technology that enables the power to transmit electromagnetic field to an electrical load without the use of wires. There are two kinds of magnetic resonant coupling and inductive coupling ways transmitting from the source to the output load. Compared with microwave method for energy transfer over a long distance, the magnetic resonance method has the advantages of reducing the barrier of electromagnetic wave and enhancing the efficiency of power transmission. In this paper, the wireless power transfer circuit having a resonant frequency of 13.45 MHz for the low power system is studied, and the hardware implementation is accomplished to measure the power transmission efficiency for the distance between the transmitter and the receiver.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.3
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• pp.349-354
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• 2013

Wireless power transmission introduced by Tesla has instrumented by many scientists of the world. This technique first was utilized as wireless communications such as radio in long range transmission. And contactless transmission using inductive property was used on white goods. In 2007, MIT' lab introduced that new wireless power transmission by magnetic resonance which has about 50% efficiency and 2M transmission distances, it was a chance to refocus a new possibility of wireless power transmission. In this paper, using LC coupling compensate the short distances of contactless transmission, this simple method could transmit about 30cm distances. Using this approach, it can be solved the short transmission distances, a drawback of Electromagnetic inductive coupling method.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.8
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• pp.27-35
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• 1999

A radius of ring resonator is determined by the resonant frequency. Resonant frequencies of resonators with the circumference which is integer times of wave length are not same the expected. In this paper, we suggest the design method of a ring resonator with coupling gap, which has the resonant frequency of desire. The equation which can make reduction of the radius of the resonators depending on the gap space is derived by the method of transmission line analysis. The criterion is suggested to determine the radius of the resonator in accordance with relative permittivity. A ring resonator by the proposed method is as small as one-third of basic ring in size and it has the resonant frequency of desire. T-type coupling line is designed to obtain large attenuation of $S_{11}$ at pass-band. These coupling line capacitances are very lower than the gap capacitances, it does not affect the resonant frequency.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.8
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• pp.1798-1804
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• 2014

A novel inductive resonator for the implementation of wireless power transfer using resonant inductive coupling is presented. The proposed inductive resonator is much smaller than the helix shape resonator suggested by MIT research team but operates the same resonant frequency with comparable wireless power transfer efficiency. The proposed inductive resonator is a spiral shape ($1,696cm^3$), which is 97 % smaller than the helix shape ($59,376cm^3$). The wireless power transfer efficiency is less than 9 % when compared to the helix shape resonator. With the reduce size and comparable efficiency, this novel inductive resonator can be used in practical application of wireless power transfer.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.7
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• pp.343-350
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• 2005

Conventionally, for transferring the primary power to the secondary one, the high frequency series resonant converter has been widely used for the contactless power supply system. However, the high frequency series resonant converter has the disadvantages such as the low efficiency, the high voltage gain characteristics and deviation of the phase angle in the overall load range. To improve this disadvantages, In this paper, the characteristics of the high efficiency and unit voltage gain as well as in-phase are revealed in the proposed three-level LCLC (Inductor-Capacitor- Inductor-Capacitor) resonant converter. The results are verified on the simulation based on the theoretical analysis and the 4kW experimental Prototype.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.3
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• pp.208-216
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• 2018

In this paper, an LLC resonant converter employing two coupled inductors on the secondary side of the converter is proposed. The conventional LLC converter exhibits serious power loss during secondary winding of the transformer because of generation of tremendous output current ripples. To overcome this problem, an LLC resonant converter with a current doubler as a rectifying circuit was recently proposed. However, the current-doubler rectifying circuit requires coupled inductors with a high coupling ratio to retain the designed resonance characteristics. Therefore, an additional hardware filter is required at the output stage to address large output current ripples. Additional design procedures are also necessary because the inductance component of the added filter affects the designed resonant network. To solve this issue, an LLC resonant converter employing two coupled inductors is proposed in this paper. Mathematical analysis shows that the proposed secondary-side current-doubler circuit does not affect the designed resonance characteristics. The operating principles and theoretical analyses are proven through a simulation and experiments with a 54 V/28 A prototype.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.1
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• pp.145-151
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• 2004

This paper proposes the calculation method of magnetic coupling coefficient of contact-less power supply by the 3D finite element method with a variation of the secondary core position. The primary, secondary self and leakage inductances and the capacitances of a resonant circuit are calculated by the finite element analysis results. The magnetic coupling coefficients are obtained also. The power factors are obtained by simulation for the magnetic coupling coefficients and compared.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.2
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• pp.111-116
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• 2016

This paper proposes a high-frequency (MHz) LLC resonant converter for a capacitor coupling wireless power transfer (CCWPT). The CCWPT uses electric field in the coupling capacitor between the transmitter and receiver electrodes with a dielectric layer. Given that capacitance is very small and the impedance is large, transferring power with a simple series resonance is difficult. Therefore, the high frequency (MHz) and high Q factor LLC converter is proposed to reduce the impedance of the coupling capacitance and to obtain a high output voltage. This paper deals with the operation analysis of the proposed LLC converter and a theoretical capacitance estimation. The operation and features of the proposed CCWPT LLC converter is verified with a 4.2 W prototype for charging mobile devices.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.6
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• pp.411-420
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• 2021

In this paper, bidirectional LLC-LC resonant DC-DC converter with notch filters in the primary side of resonant circuits is proposed. Even if resonant capacitors are used on the primary and secondary sides, the proposed converter can operate with the high gain characteristics of the LLC resonant converter without mutual coupling of resonant capacitors, regardless of the direction of power flow. In addition, by applying notch filters, the proposed converter can operate with a wider gain control range and can cope with overload and short circuit. The analysis and operating characteristics of the proposed bidirectional LLC-LC resonant converter are investigated. A 3.3 kW prototyped bidirectional LLC-LC resonant converter connected to 750 V_DC buses is designed and tested to verify the validity and applicability of this proposed converter.