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

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 D < 0.5. With the proposed scheme, the natural output voltages balancing and high step-up conversion ratio can be extended when D < 0.5. 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.