A Design Procedure for Optimizing the LLC Resonant Converter as a Wide Output Range Voltage Source

Abstract

LLC resonant converter is one of the most suitable circuit topologies that have been introduced for designing constant output voltage switched-mode power supplies. In this paper, a design procedure is introduced for using this converter as a wide output range voltage source. Unlike constant output voltage applications which need small converter inductance ratio and narrow switching frequency variations, for wide output range applications, large values of these parameters are needed simultaneously and should be optimized. Instead of minimizing the components stresses, leading to a great value of the inductance ratio, proper choice of the converter parameters resulting in a smaller inductance ratio has been done. Maximum value of the capacitor in parallel with the power MOSFETs drain-sources has been derived to realize the zero voltage switching operation in the converter inductive region. Soft switching is achieved for all power devices under all operating conditions. A prototype of the converter has been tested for different regulated output voltages (35-165 V d c ) under different loads (0-3 A d c ) and input voltages (320-370 V d c ) for using an ion implanter arc power supply, with maximum efficiency value of 94.7%. Experimental results confirm the high performance of the wide output range LLC resonant converter even under the worst case conditions. Index Terms-LLC resonant converter, switched-mode power supply (SMPS), wide output range, zero current switching (ZCS), zero voltage switching (ZVS). NOMENCLATURE a, nConverter inductance ratio and transformer turns ratio. I in N and I in max N Normalized ac input current and its maximum value. I out and I out maxOutput dc current and its maximum value. I DSM 1 and I D MOSFET drain-source and diode currents. k z Converter's input impedance ratio. V in , V in min , DC input voltage and its maximum and minimum values. and V in max V in N , V in min N , Normalized dc input voltage and its maximum and minimum values. and V in max N V out , V out min , DC output voltage and its maximum and minimum values. and V out max V out N , V out min N , Normalized dc output voltage and its maximum and minimum values. and V out max N V outFL and V outNL DC output voltage under the maximum output current and no-load conditions. V C r , V r out Resonant capacitor voltage and output ripple. V C r max , V C r max N Resonant capacitor maximum voltage and its normalized value. V DSM and V CAD Power MOSFET drain-source and power diode cathode-anode voltages. V ARR Output voltage adjustable range ratio. P out and P out max Output power and its maximum value. Q and Q max L Quality factor and its value for maximum output current and voltage. f r , f s , f s min , Resonant frequency, switching frequency, and its minimum and maximum values (in hertz).and f s max f n , f n min , Normalized switching frequency and its minimum and maximum values (dimensionless), respectively. and f n max Z in , Z in 0 , Z in∞ , Input impedance, its values at short-circuit and no-load conditions, and its normalize...

A Study of Two Multi-Element Resonant DC-DC Topologies with Loss Distribution Analyses

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