Magnetic Resonance Imaging (MRI) is one of the most advanced diagnostic modalities in modern medical imaging. Featuring non‑ionizing radiation, superior soft‑tissue resolution, and multi‑planar multi‑parameter imaging, it is widely applied in neurological surgery, oncology, orthopedics, cardiology and other clinical disciplines for disease diagnosis and research. The gradient amplifier serves as a core component of the MRI system, supplying high‑precision, high‑current, fast‑response drive current to the gradient coils to generate linearly varying gradient magnetic fields for spatial encoding of MR signals, which fundamentally determines imaging resolution, scanning speed and overall image quality. The high‑voltage power supply is an essential supporting unit for gradient amplifiers, delivering a stable DC high‑voltage bus. Its low noise performance, rapid dynamic response and long‑term stability directly govern the current accuracy, slew rate and linearity of the gradient amplifier, thereby affecting the signal‑to‑noise ratio and clarity of MRI images. Current mainstream 1.5 T / 3.0 T clinical MRI systems require gradient high‑voltage power supplies to achieve an output voltage range of ±200 V~±800 V, output power of 10 kW~100 kW, peak‑to‑peak ripple below 10 mV, line regulation less than 0.05 %, load regulation less than 0.1 %, and dynamic response time faster than 100 μs. Failure to meet these specifications introduces ripple and distortion in gradient current, nonlinear gradient fields, and ultimately causes image artifacts, reduced SNR and degraded resolution, preventing accurate clinical diagnosis. Traditional gradient power supplies adopting mains rectification plus linear regulation suffer from large ripple, sluggish dynamic response, low efficiency and excessive heat generation, failing to satisfy the stringent demands of modern high‑field high‑resolution MRI systems. All designs must comply strictly with IEC 60601‑1 general medical electrical safety standards, IEC 60601‑2‑33 Particular requirements for the basic safety and essential performance of magnetic resonance equipment for medical diagnosis, and GB 9706.15 Medical electrical equipment — Part 2: Particular safety requirements for magnetic resonance equipment. The design shall also conform to technical specifications for Class III medical device registration issued by the NMPA. Addressing the core application requirements and technical challenges of high‑voltage power supplies for MRI gradient amplifiers, this methodology establishes a comprehensive technical framework covering topology design, low‑noise optimization, fast dynamic response enhancement, electromagnetic compatibility and medical safety compliance. It accommodates gradient power demands for medical MRI systems of various field strengths and provides standardized design guidelines to support domestic substitution and performance improvement of local MRI equipment. Focusing on low‑noise output, fast transient response and high stability for MRI gradient applications, this methodology adopts a three‑stage main topology: three‑phase PFC rectification, isolated full‑bridge LLC resonant DC‑DC conversion, secondary synchronous rectification, and post‑stage active low‑dropout linear regulation (LDO), combined with fully digital closed‑loop control. This architecture overcomes the inherent limitations of conventional power supplies such as high ripple, slow dynamics and low efficiency, achieving ultra‑low noise, fast transient performance and high efficiency fully compatible with MRI gradient amplifier requirements. Five core design principles are implemented. First, the front‑end power factor correction adopts a three‑phase Vienna PFC topology, achieving a power factor ≥ 0.99 and total harmonic distortion (THD) ≤ 5 %, suppressing grid harmonic interference effectively. Zero‑voltage switching (ZVS) minimizes switching loss while enabling strong boost capability to maintain a stable 800 V DC bus from a three‑phase 380 VAC input. The topology tolerates ±20 % grid fluctuations, ensuring adaptability to variable hospital power environments. Second, the intermediate DC‑DC stage employs an isolated full‑bridge LLC resonant converter, realizing ZVS on primary switches and zero‑current switching (ZCS) on secondary rectifiers across wide voltage and load ranges. Featuring ultra‑low switching loss, high efficiency and low EMI, it forms the foundation for low‑noise high‑voltage output. Resonant parameters optimized via fundamental harmonic analysis set the operating frequency between 100 kHz and 200 kHz to maintain continuous soft switching from 10 % to 100 % load, raising overall efficiency above 96 %, reducing heat generation and suppressing switching noise. Third, the secondary side utilizes synchronous rectification with low‑on‑resistance SiC MOSFETs to drastically reduce conduction loss compared with conventional fast recovery diodes. Precise digital gating ensures full ZCS operation, eliminating reverse recovery noise and further lowering output ripple. Fourth, the output stage integrates active LDO linear regulation for final ripple suppression and dynamic response acceleration. The high‑voltage DC from the LLC stage undergoes precision linear conditioning to eliminate residual ripple while enabling ultra‑fast voltage adjustment. Parallel high‑power regulation transistors combined with high‑speed op‑amp closed‑loop control ensure high precision and ultra‑low noise, with comprehensive overcurrent, overvoltage and overtemperature protection for reliable operation. Fifth, a fully digital control system based on DSP plus FPGA manages PFC closed‑loop regulation, LLC frequency modulation and soft switching, and high‑precision LDO voltage tuning, while realizing system monitoring, fault protection and calibration. Full digital control enables continuous adjustable output to match gradient amplifiers of different power ratings and magnetic field strengths. Low‑noise output optimization constitutes the core of this methodology. Targeting the extreme noise sensitivity of MRI systems, a full‑chain noise reduction strategy covers source suppression, multi‑stage filtering and linear regulation noise cancellation. At the noise source level, full soft switching in both PFC and LLC stages eliminates voltage spikes, current surges and high‑frequency noise caused by hard switching. Switching frequencies are positioned outside the MRI receive bandwidth and gradient operating spectrum to prevent switching interference from coupling into RF signal channels and generating artifacts. Balanced three‑phase PFC reduces low‑frequency harmonic ripple, while multi‑stage input EMI filtering suppresses conducted interference from the grid. Low‑noise SiC power devices and low‑ESR film capacitors minimize intrinsic component noise. In multi‑stage passive filtering, a three‑tier filtering architecture achieves full‑band ripple attenuation. Front‑end DC bus filtering combines large film capacitors for low‑frequency ripple suppression and high‑frequency ceramic capacitors to clean switching noise. Secondary LLC output adopts second‑order LC low‑pass filtering with high‑quality low‑ESR polypropylene film capacitors to reduce switching ripple below 100 mV. Final output filtering integrates multi‑stage RC and π‑type networks with parallel high‑voltage film capacitors, ceramic capacitors and feedthrough capacitors to eliminate low, medium and high‑frequency noise, supported by high‑frequency ferrite beads for ultra‑high‑frequency suppression, ultimately limiting peak‑to‑peak ripple below 10 mV, far exceeding industry benchmarks. Active linear regulation delivers final residual ripple cancellation with extremely low output impedance and high power supply rejection ratio (PSRR ≥ 80 dB). High‑speed wideband op‑amps provide closed‑loop bandwidth above 1 MHz to attenuate residual ripple from the DC‑DC stage to less than 1 mV. Parallel high‑power MOSFET regulation extends current capability with balanced current sharing to avoid local overheating, while feedforward compensation dynamically corrects input fluctuations to enhance line regulation and transient performance. Fast dynamic response optimization addresses the ultra‑fast load variations of gradient amplifiers, where current swings from zero to hundreds of amperes within microseconds, causing abrupt bus load transitions. The dual‑stage architecture combines high‑efficiency LLC coarse regulation with high‑speed LDO fine tuning. The linear stage delivers microsecond‑level voltage correction to compensate load transients, resolving the slow dynamic limitation of standalone resonant converters. Symmetrical dual output topology ensures matched positive/negative rail response for bipolar gradient power requirements. Advanced digital control adopts feedforward plus closed‑loop composite regulation. The LLC stage uses frequency modulation with load feedforward to pre‑empt voltage drops during step transitions. The LDO stage implements high‑speed PID with current feedforward, ensuring voltage overshoot/undershoot below 0.5 % and recovery time faster than 100 μs under full load steps. FPGA‑accelerated control operates above 1 MHz loop update frequency to guarantee real‑time responsiveness. Output energy storage optimization deploys low‑ESR high‑voltage film capacitor banks near the gradient amplifier to deliver instantaneous surge energy during load jumps, minimizing voltage dips. Distributed capacitor layout shortens power traces and reduces parasitic inductance, while snubber circuits suppress voltage ringing and spikes during fast current transitions. Electromagnetic compatibility and anti‑interference design ensure stable operation within the strong magnetic field and high‑sensitivity RF environment of MRI. A fully sealed double shielding enclosure uses permalloy inner shielding against static and low‑frequency magnetic interference and aluminum outer shielding for high‑frequency electric field suppression, achieving shielding effectiveness above 80 dB. PCB layout strictly separates power, control, high‑voltage and low‑voltage domains, minimizing switching loop area to reduce radiated emission. Local shielding covers all transformers and inductors, while spread‑spectrum modulation disperses switching energy to avoid narrowband interference with MRI resonant frequencies. Multi‑stage input and output EMI filtering eliminates conducted noise coupling through power lines. Star‑type single‑point grounding prevents ground loops and potential differences, while isolated communication interfaces block control‑path interference. Magnetic components adopt amorphous and nanocrystalline core materials resistant to DC bias saturation, with optimized mounting orientation to avoid static magnetic field saturation. High‑current loops are arranged to minimize Lorentz‑force induced vibration, and non‑magnetic components ensure control circuit stability in strong magnetic fields. Medical safety and reliability comply fully with IEC 60601 series standards with reinforced double insulation and dielectric withstand exceeding twice the maximum output voltage. Complete high‑voltage sealing, door interlocks and discharge protection guarantee operator safety. Multi‑level redundant hardware plus software protection covers input over/under voltage, overcurrent, output overvoltage, short‑circuit, overtemperature and power device faults with response faster than 1 μs, enabling instant shutdown and system interlock to prevent image artifacts and equipment damage. All critical components follow medical‑grade derating principles with voltage stress ≤70 %, current stress ≤60 %, temperature stress ≤80 % of rated values. Precision water cooling maintains safe operating temperatures for high‑power devices. Full environmental validation including thermal cycling, aging and vibration ensures an MTBF exceeding 30,000 hours for continuous 24/7 hospital operation. Complete EMC compliance with medical GB/T 18268.1 guarantees stable performance in complex MRI electromagnetic environments. In summary, this methodology forms a full‑process technical framework covering topology innovation, ultra‑low‑noise design, fast dynamic response enhancement and comprehensive EMC optimization for MRI gradient high‑voltage power supplies. It fundamentally solves traditional problems such as large ripple, slow transient response and excessive electromagnetic interference. The three‑stage topology plus multi‑level filtering achieves output ripple below 10 mV. Feedforward closed‑loop control realizes dynamic response within 100 μs. Full shielding and anti‑magnetic design ensure compatibility with high‑field MRI environments. Fully meeting the stringent imaging requirements of modern high‑field MRI systems, this solution provides core technical support for domestic independent development, performance upgrading and large‑scale localization of Chinese MRI equipment.