Dual interleaved LLC resonant converter with half bridge topology of main circuit characterized by high switching frequency (500 kHz), high power density (60 W/inch3) and high efficiency (above 96 %) over entire operational range (20 %–100 %) is described. Focus was given on the practical design of power converter, which will be able to fulfil requirements on wide load range operation characterized by upcoming normative. Since proposed topology is based on dual interleaved LLC converter, the resonant component´s critical tolerance was also investigated to secure reliable and optimal operational point. Consequently, proposals for elimination of intolerance negative impact are also described. The results of theoretical analysis were verified directly through experimental measurements. Experimental results are finally compared with upcoming industrial standard 80 Plus Titanium.
This paper proposes a grid-connected single-stage micro-inverter with low cost, small size, and high efficiency to drive a 320 W class photovoltaic panel. This micro-inverter has a new and advanced topology that consists of an interleaved boost converter, a full-bridge converter, and a voltage doubler. Variable switching frequency and advanced burst control schemes were devised and implemented. A 320 W prototype micro-inverter was very compact and slim with 60-mm width, 310-mm length, and 30-mm height. In evaluations, the proposed micro-inverter achieved CEC weighted efficiency of 95.55%, MPPT efficiency >95% over the entire load range, and THD 2.65% at the rated power. The proposed micro-inverter is well suited for photovoltaic micro-inverter applications that require low cost, small size, high efficiency, and low noise.
In modern aircraft designs, following the More Electrical Aircraft (MEA) philosophy, there is a growing need for new high-power converters. In this context, innovative solutions to provide high efficiency and power density are required. This paper proposes an unregulated LLC full-bridge operating at resonant frequency to obtain a constant gain at all loads. The first harmonic approximation (FHA) model is not accurate enough to estimate the voltage gain in converters with high parasitic resistance. A modified FHA model is proposed for voltage gain analysis, and time-based models are used to calculate the instantaneous current required for the ZVS transition analysis. A method using charge instead of current is proposed and used for this ZVS analysis. Using this method, an auxiliary circuit is proposed to achieve complete ZVS within the whole load range, avoiding a gapped transformer design and increasing the efficiency and power density. A 28 Vdc output voltage prototype, with 10 kW peak output power, has been developed to validate the theoretical analysis and the proposed auxiliary circuit. The maximum efficiency (96.3%) is achieved at the nominal power of 5 kW.
Dual Interleaved LLC Converter for High Power Applications and Wide Load Range