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In order to use dc to dc boost converter in combination with a fuel cell, for modern aircraft APU, it is important that the input current ripples to be very small. This paper presents a comparative analysis of a dc to dc boost converter with variable duty cycle and one with constant duty cycle. The Dc to dc boost converter proposed was modeled in Multisim, with a PID controller. After numerical simulations it was found that input current ripples have a maximum output current of approximately 20A. The variation is more flat when operating with constant duty cycle. The use of this controller that changes the duty cycle also leads to a greater variation of ripples in relation with the output current. Thus, to make a comparison with theoretical results, which were achieved in the bibliography, numerical simulations were made with the PWM pulse at a constant value, with 50% duty cycle. Based on simulation results there were plotted the boost converter output characteristics for the two cases. Graphs were performed in Matlab. Besides these output characteristics, there were also plotted the output and input current variation, the current through the transistor, the ripples for the output voltage and for the input current in relation with the output current.Keywords: dc to dc boost converter, constant duty cycle, variable duty cycle, P.I.D. controller, PWM pulses I.

In this paper is optimized by numerical simulations a dc to dc boost converter with two parallel stages using the interleaved command technique. A comparative study between three converter topologies -one stage, two parallel stages and two interleaved stages is presented. First, the interleaved command converter is modeled in MULTISIM and is tested under many output loads. For comparison, simulations with constant and controlled duty cycle of the PWM are performed. The main characteristics of the three topologies are discussed: input current, input current ripple, output voltage ripple, and the MOSFET peak current. Keywords: optimization of a dc to dc boost converter, interleaved command technique, PWM pulsesI.

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