• Title/Summary/Keyword: Freewheeling Diode

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A New Zero-Current-Transition Buck Converter (새로운 영전류 천이형 벅 컨버터)

  • 최현칠
    • The Transactions of the Korean Institute of Power Electronics
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    • v.6 no.6
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    • pp.556-563
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    • 2001
  • In this paper a new zero current transition pulse width modulation (ZCT-PWM) buck converter is proposed to combine the desirable feature of both the conventional buck converter and resonant converters. In this proposed scheme an auxiliary circuit is added to the conventional buck converter and used to achieve soft-switching for both the main switch and the freewheeling diode while not incurring any additional losses due to auxiliary circuit And this converter operates exactly like the conventional PWM converter except for a short particular time interval. The operation of the proposed converter is explained and analyzed. and design guidelines are presented. To validate the feasibility of the proposed converter, a 100KHz 180-W prototype is built and tested.

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Analysis of Switching Clamped Oscillations of SiC MOSFETs

  • Ke, Junji;Zhao, Zhibin;Xie, Zongkui;Wei, Changjun;Cui, Xiang
    • Journal of Power Electronics
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    • v.18 no.3
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    • pp.892-901
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    • 2018
  • SiC MOSFETs have been used to improve system efficiency in high frequency converters due to their extremely high switching speed. However, this can result in undesirable parasitic oscillations in practical systems. In this paper, models of the key components are introduced first. Then, theoretical formulas are derived to calculate the switching oscillation frequencies after full turn-on and turn-off in clamped inductive circuits. Analysis indicates that the turn-on oscillation frequency depends on the power loop parasitic inductance and parasitic capacitances of the freewheeling diode and load inductor. On the other hand, the turn-off oscillation frequency is found to be determined by the output parasitic capacitance of the SiC MOSFET and power loop parasitic inductance. Moreover, the shifting regularity of the turn-off maximum peak voltage with a varying switching speed is investigated on the basis of time domain simulation. The distortion of the turn-on current is theoretically analyzed. Finally, experimental results verifying the above calculations and analyses are presented.

Development of 3.0[kW] class Fuel Cell Power Conversion System(I) (3[kW]급 연료전지용 전력변환장치(I)의 개발)

  • Mun, S.P.;Kwon, S.K.;Suh, K.Y.;Kim, Y.M.;Ryu, J.Y.
    • Proceedings of the KIEE Conference
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    • 2006.07b
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    • pp.1207-1208
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    • 2006
  • Recently, a fuel cell with low voltage and high current output characteristics is remarkable for new generation system. It needs both a DC-DC step-up converter and DC-AC inverter to be used in fuel cell generation system. Therefor, this paper, consists of an isolated DC-DC converter to boost the fuel cell voltage 380[VDC] and a PWM inverter with LC filter to convent the DC voltage to single-phase 220[VAC]. Expressly, a tapped inductor filter with freewheeling diode is newly implemented in the output filter of the proposed high frequency isolated ZVZCS PWM DC-DC converter to suppress circulating current under the wide output voltage regulation range, thus to eliminate the switching and transformer turn-on/off over-short voltage or transient phenomena. Besides the efficiency of 93-97[%] is obtained over the wide output voltage regulation ranges and load variations.

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Zero-Voltage-Transition Buck Converter for High Step-Down DC-DC Conversion with Low EMI

  • Ariyan, Ali;Yazdani, Mohammad Rouhollah
    • Journal of Power Electronics
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    • v.17 no.6
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    • pp.1445-1453
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    • 2017
  • In this study, a new zero-voltage transition (ZVT) buck converter with coupled inductor using a synchronous rectifier and a lossless clamp circuit is proposed. The regular buck converter with tapped inductor has extended duty cycle for high step-down applications. However, the leakage inductance of the coupled inductor produced considerable voltage spikes across the switch. A lossless clamp circuit is used in the proposed converter to overcome this problem. The freewheeling diode was replaced with a synchronous rectifier to reduce conduction losses in the proposed converter. ZVT conditions at turn-on and turn-off instants were provided for the main switch. The synchronous rectifier switch turned on under zero-voltage switching, and the auxiliary switch turn-on and turn-off were under zero-current condition. Experimental results of a 100 W-100 kHz prototype are provided to justify the validity of the theoretical analysis. Moreover, the conducted electromagnetic interference of the proposed converter is measured and compared with its hard-switching counterpart.