High‑frequency electrosurgical units (ESUs) are essential core devices in surgical operations. Featuring fast cutting, reliable hemostasis, flexible operation, and compatibility with both open and laparoscopic procedures, they are widely used in general surgery, orthopedics, obstetrics and gynecology, cardiothoracic surgery, urology, endoscopic centers, and nearly all clinical surgical settings. The high‑frequency high‑voltage power supply serves as the key power component of ESUs, generating high‑frequency high‑voltage sine or pulse waves ranging from 200 kHz to 5 MHz to cut and coagulate biological tissues. Its diversity of output modes, power regulation accuracy, high‑frequency isolation performance, and leakage current suppression directly determine cutting and coagulation effects, surgical safety, and the degree of thermal damage to normal tissues. Current mainstream ESUs require power supplies to support pure cutting, blended cutting, coagulation, spray coagulation, and bipolar coagulation, with peak output voltage continuously adjustable from 0 to 6 kV, power accuracy better than ±5%, and high‑frequency leakage current lower than 10 μA while meeting CF‑level patient isolation requirements. Poor performance leads to ineffective cutting or hemostasis, and excessive high‑frequency leakage current may cause severe medical accidents such as ventricular fibrillation, skin burns, and nerve injury. Traditional ESU high‑voltage power supplies suffer from limited output modes, low precision, inadequate isolation, and large leakage current, failing to meet modern demands for precision and safety. All designs must comply strictly with IEC 60601‑1, IEC 60601‑2‑2, GB 9706.4, and relevant Class III medical device registration specifications issued by the NMPA. Addressing core clinical requirements and technical challenges, this methodology establishes a full‑process framework covering multi‑mode topology design, precise power control, high‑frequency safety isolation, leakage current suppression, and comprehensive protection. It supports high‑voltage power needs for electrosurgical generators, argon plasma devices, and resectoscopes, providing standardized guidelines for domestic replacement and performance upgrading. Focusing on multi‑mode output, high safety isolation, and ultra‑low leakage current, the methodology adopts an architecture of full‑bridge high‑frequency inversion plus tunable resonant matching plus CF‑level isolated output, combined with fully digital FPGA‑based multi‑mode control. This overcomes traditional limitations and realizes versatile high‑frequency output, accurate power regulation, and maximum patient protection. Five core principles are implemented. First, the full‑bridge inverter topology delivers high power with wide adjustable range and flexible waveform control by tuning frequency, duty cycle, and phase. Si MOSFET or GaN HEMT devices support 200 kHz to 5 MHz operation with soft switching to reduce losses and EMI. Second, a tunable LC resonant matching network between the inverter and high‑voltage transformer adapts to varying tissue impedance across surgical modes, maintaining resonance for maximum efficiency, low harmonic distortion, and minimal extra thermal injury and leakage current. Third, CF‑level isolated output adopts a medical high‑frequency high‑voltage isolation transformer with double insulation for maximum patient safety compliant with IEC 60601 CF requirements. A pot‑type ferrite core, separated primary/secondary windings, double Faraday shielding with grounded copper foil, and vacuum epoxy potting reduce inter‑winding capacitance below 10 pF and achieve insulation withstand above 4 kVAC. Fourth, dual FPGA plus ARM control enables real‑time high‑frequency waveform generation, fast mode switching, closed‑loop power regulation, human–machine interaction, parameter storage, and fault diagnosis. Fully digital control supports pure cutting, three blended levels, coagulation, spray coagulation, and bipolar modes with dynamic power adaptation to tissue changes. Fifth, an independent bipolar output channel provides lower voltage, finer power tuning, and ultra‑low leakage current for precise minimally invasive endoscopic coagulation. Multi‑mode output and precise power control form the core of this methodology. Optimized waveforms match each clinical requirement: pure cutting uses continuous 300–500 kHz sine waves at 0–6 kV and 0–400 W for sharp incisions with minimal thermal spread; three blended modes combine continuous and pulsed outputs to balance cutting and coagulation for low, medium, and highly vascular tissues; monopolar coagulation adopts low‑frequency pulsed waves at 100–300 kHz for rapid hemostasis; spray coagulation delivers high‑amplitude microsecond pulses for non‑contact bleeding control; bipolar mode provides low‑voltage high‑precision output within 0–1 kV and 0–100 W with 1 W resolution for delicate microsurgery. Adaptive power control maintains stable output across tissue impedance ranging from tens to thousands of ohms. High‑speed 10 MHz sampling captures real‑time voltage, current, impedance, and power, enabling microsecond adjustments of frequency, duty cycle, and phase to keep power deviation within ±5% with overcurrent limiting to prevent carbonization and burns. Intelligent tissue recognition detects normal, cutting, coagulating, and carbonized states to auto‑adjust waveforms and prevent sticking and overheating. Bipolar automatic termination stops output once coagulation impedance thresholds are reached. High‑frequency safety isolation and leakage current suppression ensure maximum patient protection. Dual isolation separates the mains from the DC stage and the high‑frequency output from low‑voltage circuits. Double Faraday shielding minimizes capacitive coupling and restricts high‑frequency leakage current. Floating output eliminates ground loops, while common‑mode filtering reduces parasitic high‑frequency noise. Optimized driving circuits with isolated power supplies and drivers prevent noise coupling. Neutral electrode monitoring continuously checks skin contact impedance and cuts power if detachment occurs to avoid localized burns. Comprehensive multi‑layer protection includes hardware and software dual power limiting, ultra‑fast 1 μs overvoltage/overcurrent/short‑circuit shutdown, redundant neutral plate detection, thermal protection, power‑on self‑diagnosis, and interlock safety via hand or foot switches to prevent accidental activation. Reliability and EMC design ensure stable operation in complex operating room environments. All key components follow medical‑grade derating with strict voltage, current, and temperature margins. Optimized air cooling maintains safe temperatures. Full validation including thermal cycling, aging, and vibration achieves an MTBF above 20,000 hours for continuous clinical use. Full sealing, multi‑stage EMI filtering, and soft‑switching reduction of dv/dt and di/dt ensure compliance with GB/T 18268.1, achieving Grade 4 immunity and avoiding interference with monitors and anesthetic equipment. In summary, this methodology delivers a complete technical system covering multi‑mode topology, precise power regulation, CF‑level isolation, leakage current suppression, and full safety protection. It fundamentally solves traditional problems such as limited modes, low accuracy, poor isolation, and high leakage current. Fully digital multi‑mode control covers all surgical procedures; adaptive closed‑loop power accuracy reaches ±5%; and CF‑level double isolation with Faraday shielding restricts cardiac leakage current below 10 μA, fully satisfying the highest IEC 60601‑2‑2 safety standards. Widely applicable to high‑frequency electrosurgical generators, argon knives, and plasma resection devices, it provides core technical support for independent innovation and domestic upgrading of high‑end surgical equipment.