Design and optimization of the on board DC/DC converters of Swayam satellite

This paper discusses the optimization of the DC-DC Converters of 1-U Pico-satellite "Swayam". Swayam Satellite has two DC-DC Converters on-board. A Boost converter is used to step-up solar panel voltage to regulated 5V and charge the battery pack. A Buck converter is used to power all the active subsystems on the 3.3V bus. Special techniques and trade-offs ensure that both the converters perform optimally in the expected region of operation. Efficient system design has averted the requirement of Maximum Power Point Tracking (MPPT) algorithm and has greatly reduced system complexity. Apart from Space heritage and reliability, converter component selection, setting converter parameters such as switching frequency and printed circuit board (PCB) layout contributes to the overall system performance. Current-mode control in DC/DC Converters faces an inherent stability issue, leading to sub harmonic oscillations. The unstable mode of operation when the duty cycle exceeds 50% has been resolved by loop compensation techniques. When the EPS is powered up, the high current demands of the boost converter damage the module as well as the solar panels. A specially designed soft start technique helps in delaying the start-up of the converter, thus snubbing the current overshoots. A perfect jitter-free gate drive minimizes the switching noise generated by the DC/DC converter. Moreover, component layout and changing loop areas in converters, ground returns, ground bounce and star connections ensure superior performance. The design accounts for system engineering factors like size and mass constraints as well as providing a magnetically clean environment for any sensitive payloads of the satellite. The DC/DC converters of Swayam satellite have been designed to cater to the power demands of a small satellite profile.