Professor Arthur Witulski of Vanderbilt University delivered this lecture for the Introduction to Radiation Effects Engineering online SCALE course.
Switched‑mode power converters form the backbone of modern satellite power architectures, where the limited energy harvested from photovoltaic arrays must be transformed efficiently to supply delicate onboard electronics. Understanding how DC‑to‑DC conversion operates in the harsh space environment is essential for designing reliable, low‑mass power subsystems that meet stringent mission constraints.
The resource examines the operation of buck converters that step down a high‑voltage solar bus to the few‑volt levels required by micro‑processors and sensors. It derives the fundamental relation Vout=DVin from the inductor voltage‑time balance V=LdI/dt and illustrates the triangular inductor‑current waveform that results from the on‑off switching of a power MOSFET. The lecture contrasts the dissipative resistor‑divider approach with the high‑efficiency switched‑mode topology, quantifies the gate‑drive current needed to achieve fast turn‑on and turn‑off transients, and explains why a floating gate‑drive circuit is required when the MOSFET source is not referenced to ground. Radiation effects on the switching devices are introduced as a prerequisite for robust satellite operation.
Armed with this knowledge, learners can explain how a buck converter reduces voltage, derive the output voltage as a function of duty cycle, and evaluate the efficiency advantage of switching converters over simple resistor dividers. They are also able to calculate the peak gate‑drive currents for power MOSFETs and to design a floating gate‑drive stage that meets the voltage, current, and isolation demands of a satellite power system, thereby enabling practical engineering of space‑qualified DC‑DC converters.