The Transactions of the Korean Institute of Power Electronics (전력전자학회논문지)

The Korean Institute of Power Electronics (전력전자학회)
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A Common Capacitor Connected LLC Resonant Converter with Auxiliary Switches Operating Over a Wide Output Voltage Control Range

넓은 출력전압 제어범위에서 동작하는 보조스위치 적용 공통커패시터 연결 LLC 공진컨버터

  • Oh, Jae-Sung (Electrical & Electronics Engineering, Jeonju University) ;
  • Kim, Min-Ji (Electrical & Electronics Engineering, Jeonju University) ;
  • Lee, Ji-Cheol (Electrical & Electronics Engineering, Jeonju University) ;
  • Kim, Eun-Soo (Electrical & Electronics Engineering, Jeonju University) ;
  • Jeon, Yong-Seog (Electrical & Electronics Engineering, Jeonju University) ;
  • Kook, Yoon-Sang (PACTECH CO.,LTD)
  • Received : 2018.10.10
  • Accepted : 2019.06.18
  • Published : 2019.08.20
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Abstract

A capacitor common connected LLC resonant converter with auxiliary switches for a wide output voltage control range is presented in this paper. The proposed converter can be controlled in two ways to achieve a wide output voltage control range of Vo-3Vo. The first control method is performed through pulse width modulation of the auxiliary switches and primary switching devices. The second control method is conducted through frequency modulation of the primary switching devices configured to operate in full-bridge switching modes, when the auxiliary switches are turned off. The feasibility of the proposed converter is verified by the experimental results of a 5 kW prototype.

Keywords

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Fig. 3. PM Operating modes of Mode-1, and Its waveforms.

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Fig. 4. (a) FM Operating modes of Mode-2, (b) Its waveforms.

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Fig. 6. Voltage gain characteristics due to load variation in each operating mode (Mode-1. Mode-2).

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Fig. 7. Digital implementation of PM/FM control (a) Block diagram, (b) Key waveforms.

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Fig. 8. Experimental waveforms of voltage (Vab, VS11) /current(IP1, IS1) across the primary and secondary terminals of the converter [Mode-1[PM(Pulse-width Modulation)]. [Ch1:500V/Div, Ch2:5A/Div, Ch3:250V/div, Ch4:5A/Div, Time:1us/Div]

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Fig. 10. Experimental waveforms of the terminal voltages (Vab, VS11)/rectified currents(IS1, IS2) of the converter operating in PM mode(300Vdc). [Ch1:500V/Div, Ch2:5A/Div, Ch3:250V/div, Ch4:5A/Div, Time:1us/Div]

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Fig. 9. Experimental waveforms of voltage (Vab, VS11) /current(IP1, IS1) across the primary and secondary terminals of the converter [Mode-2[FM(Frequency Modulation)]. [Ch1:500V/Div, Ch2:5A/Div, Ch3:250V/div, Ch4:5A/Div, Time:1us/Div]

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Fig. 11. Experimental waveforms of the terminal voltages (Vab, VS11)/rectified currents(IS1, IS2) of the converter operating in FM mode(400Vdc). [Ch1:500V/Div, Ch2:5A/Div, Ch3:250V/div, Ch4:5A/Div, Time:1us/Div]

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Fig. 12. Measured waveforms for output voltage transitions between 240Vdc and 445 Vdc at VIN = 650Vdc and constant output current Io(2A) (Ch 1: 500V/Div, Ch 3: 100V/Div, Time: 2s/Div).

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Fig. 13. 5kW 3-bridge LLC resonant converter.

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Fig. 14. Efficiency characteristics in the PM/FM mode.

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Fig. 1. (a) 3-bridge LLC resonant converter, (b) Its gain characteristics.

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Fig. 2. (a) 3-bridge LLC resonant converter using the primary auxiliary switches, (b) Its gain characteristics.

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Fig. 5. Operation of 3-bridge LLC converter for the theoretic analysis of voltage gain: (a), (b) voltage waveforms across the primary and secondary terminals, (c), (d) Its equivalent circuits.

TABLE I MAJOR RATINGS IN THE PROPOSED CONVERTER

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TABLE II PARAMETERS OF RESONANT CIRCUIT

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References

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