Abstract: Addressing the issues of high power consumption, bulky size, high cost, and insufficient stability in switching power supplies used in photovoltaic power generation and high-voltage variable frequency systems, this paper proposes a design scheme for an ultra-wide and ultra-high voltage input power supply based on a multi-stage series flyback topology. This scheme, building upon the traditional flyback topology, achieves an ultra-wide input voltage range of DC 200~1200 V through a 4-stage MOSFET series structure, significantly enhancing the adaptability of the module system. To optimize magnetic core losses, an EE20 magnetic core is employed, and a power transformer with a primary-to-secondary coil turn ratio of 5∶1 is designed. Combined with offline PWM control chips and drive transformers for coordinated regulation, the final technical specifications achieved include an output power of 40 W, an output voltage of 24 V, and an efficiency of 89.7%, with a voltage accuracy of 0.025%. Experimental research results show that this design possesses advantages such as simple circuit structure, high reliability, and excellent dynamic voltage sharing performance. Additionally, it features output overcurrent protection, input undervoltage protection, and input reverse polarity protection functions, effectively supporting the efficient operation of photovoltaic inverters and high-voltage variable frequency equipment. This provides new technical support for the field of new energy power electronics.