A Class E Power Oscillator for 6.78-MHz Wireless Power Transfer System

  • Received : 2017.05.05
  • Accepted : 2017.09.01
  • Published : 2018.01.01


A class E power oscillator is demonstrated for 6.78-MHz wireless power transfer system. The oscillator is designed with a class E power amplifier to use an LC feedback network with a high-Q inductor between the input and the output. Multiple capacitors are used to minimize the variation of the oscillation frequency by capacitance tolerance. The gate and drain bias voltages with opposite characteristics to make the frequency shift of the oscillator are connected in a resistance distribution circuit located at the output of the low drop-out regulator and supplied bias voltages for class E operation. The measured output of the class E power oscillator, realized using the co-simulation, shows 9.2 W transmitted power, 6.98 MHz frequency and 86.5% transmission efficiency at the condition with 20 V $V_{DS}$ and 2.4 V $V_{GS}$.

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Fig. 1. Schematic of the proposed class E power oscillator

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Fig. 2. Transient waveforms in the circuit simulation of theclass E power oscillator

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Fig. 3. Schematic for EM circuit co-simulation of the classE power oscillator considering the effects of thelayout design on PCB

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Fig. 4. Transient waveforms using EM circuit co-simulation in each node of the power oscillator. (a)At the gate node, (b) the drain node of the transistorand (c) the output port connected to the 50-Ωreference impedance

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Fig. 5. Proposed class E power oscillator module. The overall size of the module is 35 mm (W)×65 mm(L)×30 mm (H) including a LDO regulator, a SMPS connector, a metal heat sink, a cooling fan, and interconnections to BLE module, which can be used to control the regulator operation

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Fig. 6. Measured fundamental oscillation frequencies of thepower oscillator depending on the bias voltages,which are the VGS (an opened circle line) and theVDS (a closed box line)

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Fig. 7. Measured power conversion efficiency andtransmitted power of the power oscillator dependingon the VDS at 2.4 V VGS

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Fig. 8. Output power spectrum of the power oscillator with30 dB attenuator

Table 1. Comparison of the capacitances in the feedback loop designed to generate the 6.78-MHz oscillation frequency in both simulations

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Table 2. Design parameters of the power oscillator in Fig. 1

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Table 3. Comparisons of the class E oscillator in the MHz range

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Supported by : Yeungnam University


  1. Ke We, Debabani Choudhury and Hiroshi Matsumoto, "Wireless Power Transmission, Technology, and Applications [Scanning the issue]," in Proc. the IEEE, vol. 101, no. 6, pp. 1271-1275, Jun. 2013.
  2. David W. Baarman and Joshua Schwannecke, "Understanding Wireless Power," White paper of Fulton Innovation, Dec. 2009.
  3. Benjamin L. Cannon, James F. Hoburg, Daniel D. Stancil and Seth Copen Goldstein, "Magnetic Resonant Coupling As a Potential Means for Wireless Power Transfer to Multiple Small Receivers," IEEE Trans. Power Electronics, vol. 24, no. 7, pp. 1819- 1825, Jul. 2009.
  4. Jong-Ryul Yang, Hyeon-Chang Son and Young-Jin Park, "A Class E Power Amplifier with Coupling Coils for a Wireless Power Transfer System," Progress In Electromagn. Research C, vol. 35, pp. 13-22, Jan. 2013.
  5. Jong-Ryul Yang, Jinwook Kim and Young-Jin Park, "Class E Power Amplifiers using High-Q Inductors for Loosely Coupled Wireless Power Transfer System," J. Electr. Eng. Technol., vol. 9, no. 2, pp. 569-575, Mar. 2014.
  6. Anthony N. Laskovski and Mehmet R. Yuce, "Class- E Self-oscillation for the Transmission of Wireless Power to Implants," Sensors and Actuators: A. Physical, vol. 171, no. 2, pp. 391-397, Nov. 2011.
  7. Andrei Grebennikov, RF and Microwave Transistor Oscillator Design, WILEY, pp. 165-169, 2007.
  8. Xuezhe Wei, Zhenshi Wang and Haifeng Dai, "A Critical Review of Wireless Power Transfer via Strongly Coupled Magnetic Resonances," Energies, vol. 7, no. 7, pp. 4316-4341, Jul. 2014.
  9. Thuc Phi Duong and Jong-Wook Lee, "A Dynamically Adaptable Impedance-Matching System for Midrange Wireless Power Transfer with Misalignment," Energies, vol. 8, no. 8, pp. 7593-7617, Jul. 2015.
  10. Jan Ebert and Marian Kazimierczuk, "Class E High- Efficiency Tuned Power Oscillator," IEEE J. Solid- State Circuits, vol. SC-16, no. 2, pp. 62-66, Apr. 1981.
  11. Marian K. Kazimierczuk, Vladimir G. Krizhanovski, Julia V. Rassokhina and Dmitrii V. Chernov, "Class-E MOSFET Tuned Power Oscillator Design Procedure," IEEE Trans. Circuits Syst. - I. Regular Papers, vol. 52, no. 6, pp. 1138-1147, Jun. 2005.
  12. Hiroyuki Hase, Hiroo Sekiya, Jianming Lu and Takashi Yahagi, "Novel Design Procedure for MOSFET Class E Oscillator," Proc. the 47th IEEE Int. Midwest Symp. Circuits Syst., Hiroshima, Japan, pp. 33-36, Jul. 2004.