A MHz <i>LCLCL</i> Resonant Converter Based Single-Stage Soft-Switching Isolated Inverter With Variable Frequency Modulation
Hao Wen, Dong Jiao, Jih‐Sheng Lai, Johan Strydom, Bing Lu
Abstract
Compared to the typical two-stage isolated inverter, which includes an isolated dc–dc and a pulsewidth modulated dc–ac, the single-stage approach features lower component counts, less control complexity, better efficiency, and power density with an isolated dc-rectified sine stage and a line frequency unfolder. In the literature, SRC and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> are mostly utilized for the isolated dc-rectified sine stage, which is the key part of an efficient single-stage inverter design. This article introduces a novel MHz <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCLCL</i> converter based single-stage, soft-switching isolated inverter with variable frequency modulation. The paralleled <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> within the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCLCL</i> resonant tank can naturally create a zero voltage gain at their resonant frequency, which shows superior characteristics for rectified sine wave generation. With the proposed <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCLCL</i> resonant tank design method, simpler control and better output ac voltage waveform quality for different load conditions can be obtained. To verify the proposed resonant tank design method and the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCLCL</i> converter based single-stage isolated inverter topology, a GaN based 380 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dc</sub> –600 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ac</sub> , 1.2 kW prototype is built and tested. Under different load conditions, the measured total harmonic distortion of the output voltage can always keep around 2% with 97.0% peak efficiency for the overall inverter.