Radiation therapy simulators are critical front‑end devices in the full oncology radiotherapy workflow, performing core functions including precise tumor target localization before treatment, radiation field planning, patient positioning verification, and treatment plan simulation. They are essential for ensuring radiotherapy accuracy and preventing unnecessary radiation damage to normal tissues. The high‑voltage power supply serves as the key power component, providing highly stable anode high voltage, cathode filament heating power, and grid bias control for the X‑ray tube. Its long‑term output stability, ripple suppression capability, and dose control accuracy directly determine X‑ray dose consistency, imaging clarity, and target positioning precision. Meanwhile, its safety interlock system guarantees radiation protection for patients and operators as well as long‑term equipment reliability, representing a mandatory compliance item for medical device certification.
Radiation therapy simulators impose far stricter technical requirements than conventional industrial high‑voltage power supplies. First, exceptional long‑term stability is required: under continuous clinical operation, the annual output drift shall not exceed ±0.1%, tube current accuracy ≤ ±2%, and peak‑to‑peak ripple ≤ 0.5%, ensuring consistent X‑ray dose and image quality over time and eliminating positioning deviations caused by parameter drift. Second, absolute medical‑grade safety must be achieved through a fail‑safe interlock architecture that automatically enters a safe state under any hardware or software fault, preventing unintended X‑ray emission, electric shock hazards, and tube damage. Third, wide operational adaptability is necessary to support continuous fluoroscopy, pulsed exposure, and radiographic positioning modes, with continuously adjustable voltage from 40 kV to 150 kV and tube current ranging from 0.5 mA to 500 mA to accommodate imaging requirements for head, chest, abdomen, and pelvic regions. Fourth, full regulatory compliance is mandatory in accordance with GB 9706.1‑2020, GB 9706.208‑2020, YY 0775‑2010, YY 0505‑2012, and relevant NMPA registration standards.
Traditional industrial and conventional diagnostic X‑ray power supplies suffer from severe long‑term drift, insufficient ripple suppression, software‑dependent protection without true fail‑safe design, and incomplete medical safety certification, making them unsuitable for radiotherapy simulation applications. This methodology establishes a comprehensive technical framework covering medical‑grade topology design, full‑lifecycle stability optimization, fail‑safe interlock protection, clinical scenario adaptation, and EMC compliance. It supports both fixed and mobile radiotherapy simulators and delivers standardized design guidelines for domestic equipment development, regulatory approval, and safe clinical deployment.
Addressing core challenges including ultra‑long‑term stability, absolute radiation safety, medical compliance, and wide dynamic operation, the proposed architecture adopts high‑frequency resonant inversion, symmetric positive/negative voltage multiplication, dual closed‑loop precision control, and fully hardware redundant interlocks. Combined with full‑temperature adaptive compensation, multi‑stage low‑ripple optimization, and fail‑safe logic, it achieves annual long‑term stability within ±0.1%, output ripple below 0.5%, and full compliance with mandatory medical safety standards. Five core design principles are defined.
First, medical‑grade topology design integrates front‑end PFC regulation, high‑frequency resonant inversion, symmetric bipolar high‑voltage multiplication, closed‑loop filament control, and grid bias regulation. Active PFC ensures a power factor ≥ 0.99 and THD ≤ 3%, stabilizing the DC bus against grid fluctuations and avoiding interference with other precision medical devices. The full‑bridge LLC resonant inverter operates at 50 kHz–100 kHz with full‑range ZVS and ZCS, minimizing switching losses, EMI, and ripple while improving reliability for continuous long‑term operation. The symmetric voltage multiplier generates balanced ±20 kV to ±75 kV outputs, achieving 40 kV–150 kV across the X‑ray tube, reducing insulation stress, lowering leakage current, improving dose stability, and minimizing high‑voltage interference with imaging. Independent closed‑loop filament power provides 0–5 A continuously adjustable current with ±1% accuracy and response below 100 μA for precise tube current regulation. The grid bias supply delivers adjustable negative voltage from −2000 V to 0 V, enabling fast X‑ray switching with rise/fall times ≤ 10 μs to prevent unintended emission. The entire system implements double insulation with dielectric withstand exceeding twice the rated output plus 1000 V, strictly limiting patient leakage, enclosure leakage, and auxiliary current within GB 9706.1 safety limits.
Second, full‑lifecycle long‑term stability is ensured through optimized component selection, dual closed‑loop digital control, environmental compensation, and aging suppression. All critical components adopt medical‑grade low‑drift specifications: high‑voltage rectifiers with leakage ≤ 1 μA at 150 kV; metalized polypropylene film capacitors with temperature coefficients ≤ ±30 ppm/°C, annual decay ≤ 0.05%, and service life ≥ 100,000 hours; reference sources with drift ≤ 0.5 ppm/°C; precision metal foil sampling resistors with annual stability ≤ ±0.01%; and high‑reliability SiC MOSFETs or IGBTs with long operational lifespan. Dual closed‑loop control consists of an outer high‑voltage loop and an inner tube‑current loop based on medical DSP+FPGA architecture. FPGA handles high‑speed sampling, PWM modulation, and hardware protection with loop update rates ≥ 200 kHz, while DSP executes adaptive PID with feedforward compensation for grid voltage, load variation, and filament current. Synchronized 24‑bit high‑precision ADC sampling at ≥ 100 kHz ensures accurate real‑time regulation, achieving voltage precision ≤ ±0.2% FS, tube current accuracy ≤ ±2% FS, line regulation ≤ ±0.1%, and load regulation ≤ ±0.2%.
Third, a fail‑safe three‑level redundant interlock system follows hardware‑priority, mutually redundant, fail‑closed, and fully traceable principles. All safety loops adopt dual hardwired normally closed channels independent of software; any disconnection or fault immediately cuts high voltage and blocks X‑ray emission. The first level covers fundamental safety interlocks including emergency stop dual redundant circuits with response ≤ 1 ms, key‑switch authorization, radiation door interlocks, high‑voltage cabinet door safety switches, protective earth continuity monitoring, and high‑voltage readiness confirmation. The second level ensures radiation and dose safety through dual independent ionization chamber dose monitoring with hardware over‑dose shutdown within 1 μs, hardware maximum exposure timer, over‑voltage/over‑current hardware comparators, tube temperature and filament protection, normally closed grid bias blocking for instantaneous X‑ray cutoff ≤ 10 μs, and dual‑stage handswitch exposure permission. The third level provides equipment emergency protection including arc discharge detection with 1 μs cutoff, short‑circuit overcurrent protection, multi‑point thermal shutdown, grid anomaly protection, communication fault interlocks, sampling inconsistency protection, and non‑volatile fault logging with tamper‑proof storage. All interlock circuits implement fail‑closed logic to guarantee safe conditions upon any single failure. Full power‑on self‑testing verifies all protection functions before high‑voltage enabling.
Fourth, comprehensive clinical scenario adaptation supports seamless integration with simulator mechanical motion, imaging detectors, treatment planning systems, and hospital information platforms. Preconfigured exposure templates cover head, chest, abdomen, pelvic, and extremity protocols for fluoroscopy, radiography, and simulation. Continuous fluoroscopy, pulsed exposure, and sequential radiography modes are fully supported with adjustable pulse widths from 1 ms to 1000 ms. Hardwired interlocks synchronize X‑ray emission with mechanical positioning; nanosecond triggering ensures precise alignment with flat‑panel detectors or image intensifiers. DICOM compatibility enables automatic parameter import from treatment plans. Built‑in dose calibration and QA functions support routine radiotherapy quality control including stability, linearity, repeatability, and half‑value layer testing. All operational data, exposure records, interlock events, and fault logs are stored for at least five years in non‑modifiable format to meet regulatory traceability requirements. Power‑failure recovery preserves current parameters and resumes safely after power restoration, while low‑dose fluoroscopy modes minimize patient and staff radiation exposure following ALARA principles.
Fifth, full medical compliance and EMC design strictly implement GB 9706.1‑2020, GB 9706.208‑2020, and YY 0505‑2012. Protective earthing resistance ≤ 0.1 Ω with continuous monitoring; clearances, creepage distances, and dielectric strength comply with reinforced insulation requirements; all leakage currents remain within permissible limits under normal and single‑fault conditions with BF‑type patient protection. Full sealed double metal shielding with permalloy and aluminum alloy compartments achieves shielding efficiency ≥ 80 dB to suppress high‑frequency interference with imaging systems. Three‑stage EMI filtering is installed at the input; all control and sampling signals use optical isolation to eliminate common‑mode interference. Multi‑layer PCB layout separates high‑power and low‑signal areas with complete ground planes and shielding barriers. Radiated emission, conducted emission, ESD, EFT, surge, and magnetic field immunity all meet the highest medical grades for stable operation in complex hospital environments without interfering with other critical devices.
Full‑lifecycle stability optimization eliminates drift caused by temperature variation and component aging through multi‑dimensional parameter modeling, adaptive compensation, low‑ripple enhancement, constant temperature thermal management, and aging suppression. Full‑temperature calibration from −10 °C to +50 °C and long‑term aging characterization establish temperature‑time‑deviation mathematical models stored in non‑volatile memory. Real‑time temperature sensing and operational runtime tracking dynamically adjust reference voltage, control parameters, and filament current to maintain annual stability ≤ ±0.1% and tube‑current repeatability ≤ ±1%. Automatic periodic calibration corrects system errors without manual intervention, while dual redundant sampling ensures data reliability and prevents dose deviation from single‑channel faults. Ripple performance is optimized through full‑range ZVS/ZCS resonant operation, adaptive dead‑time control, symmetric voltage cancellation, three‑stage π‑type high‑voltage filtering, and active ripple cancellation, suppressing residual ripple below 0.2% for high‑precision positioning imaging. Zoned thermal management stabilizes critical reference and sampling components within 25 °C ± 0.5 °C using independent thermostatic chambers; power modules adopt liquid cooling to maintain operational temperatures within 45 °C ± 5 °C. Fully encapsulated construction isolates humidity and ambient temperature fluctuations while improving insulation and vibration resistance. Ultra‑derating design reduces component electrical, thermal, and mechanical stress; electrolytic capacitors are eliminated entirely to extend service life beyond 10 years. Soft start/stop minimizes transient stress; operational runtime and exposure counting enable scheduled maintenance reminders; predictive health monitoring evaluates component aging and provides early fault warnings to ensure continuous clinical availability.
The fail‑safe interlock protection system guarantees radiation safety through three‑level hardware‑dominated redundancy with normally closed loops that enforce safe shutdown upon disconnection or failure. Emergency stop, door interlocks, cabinet safety switches, and earth continuity form the fundamental safety barrier. Dose limitation, exposure timing, over‑voltage/over‑current protection, tube protection, and grid bias blocking prevent unintended or excessive radiation. Arc detection, short‑circuit protection, thermal shutdown, and communication fault handling protect equipment integrity while maintaining safe states under all error conditions. Comprehensive self‑diagnosis validates all protection functions during power‑on to avoid unsafe operation.
Clinical adaptation and regulatory compliance ensure full alignment with medical device regulations, ISO 14971 risk management, and YY/T 0664 software lifecycle standards. Complete technical documentation, risk analysis, traceable software version control, and hierarchical user permission management support full NMPA registration. Integrated quality control functions, data traceability, low‑dose operating modes, and recovery mechanisms satisfy daily radiotherapy workflows and radiation protection requirements.
In summary, this methodology delivers a complete technical framework covering medical‑grade topology, full‑lifecycle stability enhancement, fail‑safe interlock architecture, clinical adaptation, and regulatory compliance. It fundamentally resolves traditional limitations such as long‑term drift, excessive ripple, inadequate safety protection, and insufficient medical certification. Adaptive full‑temperature compensation achieves annual stability within ±0.1%; three‑level redundant fail‑safe interlocks ensure absolute radiation and electrical safety; full regulatory compliance supports medical device approval. The solution is widely applicable to radiotherapy simulators, diagnostic X‑ray systems, digital gastrointestinal equipment, and C‑arm devices, providing core technical support for domestic innovation, clinical safety, and regulatory certification of high‑end radiotherapy equipment.