福衛五號衛星的電源控制與分配單元主要功能為衛星電力系統的控制與分配中心，如同人體之心臟及血液系統，將太陽能板所產生的電能提供成衛星操作所需電力，分配適當電力給使用者。電源控制與分配單元的保護電路主要著眼於電壓與電流兩部分：電壓保護部分主要為主電源通道的電壓過低鎖定偵測電路、衛星電池的過電壓偵測電路、以及 DC-DC 轉換器的過低電壓偵測電路；電流保護方面分別為電源使用者與內部直流轉換電路的過電流保護電路。當異常發生時，保護裝置可即時提供電力使用者與內部電路系統隔離與保護。本文將針對這些保護電路的原理與設計電路作詳細的說明與分析。

The power control and distribution unit (PCDU) in FORMOSAT-5 satellite, acts as the satellite power andallocation center, similar to human heart. The main functions are to condition energy from the solar arrays anddistribute power for all subsystems on the satellite. The PCDU̓s protection circuits provide monitoring and isolationaccording to voltage and current of internal circuit system and external power users. The voltage protection circuitsare undervoltage-lockout (UVLO) detector for the main bus, over voltage (OV) detector for satellite battery, andunder voltage (UV) protector for DC-DC converters. The portion of current protection circuit is over current (OC)protector for external power users and DC-DC converter system. This paper describes protection working methodsand the reliable circuit design implementation.