The rapid development of CubeSat-class missions has markedly increased the demand for high-efficiency and highly reliable power management systems capable of operating in the harsh space environment. In this study, we validated a highly integrated, multi-output power management unit (PMU) designed for a multiple-particles analyzer (MPA) developed under CubeSat-class specifications. The proposed PMU provides both isolated and non-isolated stable output rails from input buses of ±15 and +5 V. The system incorporates inrush-current suppression, electronic fuse (e-Fuse) protection, and real-time voltage, current, and temperature monitoring functions to ensure operational safety and reliability. In both static- and dynamic-load tests, the developed PMU demonstrated excellent steady-state stability, with measured ripple voltages of 63 mVpp (1.05%) for the +6 V rail and 46 mVpp (0.77%) for the −6 V rail, meeting the MPA’s power-quality requirements. During dynamic-load changes from 80 to 10 mA, the +6 V rail exhibited an overshoot of approximately 120 mV that recovered within 2 μs, confirming the effectiveness of the compensation and recovery network. The peak inrush currents for all input rails remained below 420 mA, confirming the stability and robustness of the circuits for controlling the inrush current. The thermal-vacuum simulation tests further confirmed the PMU’s environmental robustness: across a temperature range from −40 to +70 ℃, the unit maintained voltage regulation without observable drift, demonstrating strong thermal stability and suitability for the space environment. The overall experimental results confirm that the proposed PMU achieves both electrical stability and environmental robustness, and therefore represents a lightweight, modular, and highly integrated power solution for the MPA. Moreover, this design provides a foundation for future developments aimed at increased power densities and long-duration mission operations in space applications. Beyond power conversion, the PMU embeds on-board voltage, current, and temperature sensing for real-time health monitoring; this integrated telemetry not only safeguards the particle-sensing MPA payload but also provides a continuous data stream that can underpin Artificial Intelligence of Things (AIoT) and intelligent-sensing functions such as autonomous fault diagnosis and predictive maintenance. The PMU integrates on-board temperature (MCP9700) and voltage/current sensing for real-time health monitoring, and its thermal behavior was further characterized through multi-point temperature sensing during thermal-vacuum testing. As the enabling and protection unit for the MPA—a particle-sensing payload—the PMU, together with the payload, was additionally subjected to proton single-event-effect and 60Co total-ionizing-dose radiation testing to verify its reliability in the space environment.