Asymmetrical PWM Scheme Eliminating Duty Cycle Limitation in Input-Parallel Output-Series DC–DC Converter

Abstract

In this letter, an asymmetrical pulsewidth modulation (PWM) scheme is proposed to solve the output voltage unbalance and voltage gain issues of the input-parallel output-series (IPOS) converter when <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$D &lt; 0.5$</tex-math></inline-formula> . With the proposed scheme, the natural output voltages balancing and high step-up conversion ratio can be extended when <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$D &lt; 0.5$</tex-math></inline-formula> . As a result, combined with the conventional PWM scheme, the duty cycle limitation of the IPOS converter is completely eliminated without any extra components or dedicated control. A 2-kW prototype of the IPOS converter was built and tested to verify the performance of the proposed PWM scheme.