Civil security inspection equipment is the core safety protection equipment for public places such as airports, high-speed railway stations, subway stations, customs ports, large venues, government agencies, schools and hospitals. It covers a full range of products including X-ray baggage scanners, security doors, handheld metal detectors, explosive trace detectors, liquid inspectors and under-vehicle inspection systems. Among them, core devices such as X-ray scanners and explosive detectors rely on high-voltage power supplies to provide stable high-voltage bias output for X-ray tubes, photomultiplier tubes and ion mobility spectrometry detectors, realizing key functions such as X-ray emission, ray detection and explosive ion identification. As the critical core component of civil security inspection equipment, the high-voltage power supply undertakes key tasks including ray source power supply, detector bias and signal amplification. Its output stability, long-term operational reliability, environmental adaptability, radiation safety protection capability and electromagnetic compatibility directly determine the detection accuracy, penetration capability, imaging clarity and false alarm rate of security inspection equipment, as well as the overall safety protection capacity of public places. Civil security inspection scenarios impose differentiated technical requirements and core challenges on high-voltage power supplies that are completely different from conventional industrial power supplies and medical X-ray power supplies. First, extreme high output stability and low ripple requirements. The tube voltage and tube current of the X-ray tube in X-ray scanners directly determine the energy, dosage and penetration of X-rays. Fluctuations in tube voltage cause changes in X-ray energy, leading to reduced imaging contrast and uneven penetration; fluctuations in tube current result in unstable X-ray dosage, causing uneven image brightness, increased noise and even missed detections and misjudgments. For explosive detectors, every 1% change in the high-voltage bias of photomultiplier tubes and ion mobility spectrometry detectors leads to more than 10% gain deviation, directly reducing detection accuracy and raising false alarm rates. It is required that the long-term output voltage stability is better than ±0.1%/8h, the short-term stability better than ±0.05%, the peak-to-peak output voltage ripple lower than 0.05%, and the tube current control accuracy higher than ±1%, ensuring stable X-ray emission and high-precision operation of detectors. Second, high reliability and long service life for long-term continuous operation. Civil security inspection equipment usually operates 24/7 without interruption; devices at key hubs such as airports and high-speed railway stations have an annual operating time exceeding 8,000 hours. Installed in public places with long maintenance cycles and difficult upkeep, any failure will close security channels and cause crowd congestion and safety hazards. The power supply is required to achieve MTBF ≥1×10⁵h and design life ≥10 years with an ultra-low failure rate, ensuring stable continuous operation and preventing equipment shutdown caused by power failures. Third, wide-range complex environmental adaptability requirements. Civil security inspection equipment serves extremely diverse scenarios, ranging from outdoor checkpoints in cold northern regions and high-temperature & high-humidity coastal ports in the south, to high-altitude plateau airports and underground low-altitude subway stations. It faces harsh conditions including a wide temperature range of -40℃~+55℃, humidity of 10%~95% RH, high-altitude low air pressure, salt spray corrosion, dust, grid fluctuations and strong electromagnetic interference. The power supply must deliver full-scenario environmental adaptability for normal startup and stable operation under extreme conditions without performance degradation. Fourth, strict radiation safety and electrical safety requirements. The high-voltage power supply of X-ray scanners provides up to 160kV high voltage for X-ray tubes, belonging to dangerous high-voltage equipment. Meanwhile, X-rays are ionizing radiation, and national mandatory regulations govern radiation and electrical safety for civil security devices. The power supply must be equipped with complete non-bypassable multi-level safety interlocks and protection functions to cut off high-voltage output instantly under any abnormal conditions and eliminate accidental radiation exposure. It shall fully comply with GB 15208 for micro-dose X-ray security inspection equipment, GB 4793.1 for electrical safety of measuring & control equipment, and GB 18871 for basic standards on ionizing radiation protection and radiation source safety. Fifth, ultra-low electromagnetic interference and strict EMC requirements. Security inspection equipment integrates high-precision X-ray detectors, image acquisition systems, data processing systems and metal detection sensors which are highly sensitive to electromagnetic interference. Switching noise and electromagnetic radiation from high-voltage power supplies cause distorted detector signals, reduced image signal-to-noise ratio and decreased metal detection sensitivity, resulting in blurry images, missed inspections and false alarms. Meanwhile, security devices installed in public places must not interfere with surrounding mobile phones, communication devices and security monitoring systems. The power supply must meet the highest EMC grades specified in GB/T 17626 and GB/T 9254, while maintaining strong anti-interference capability for stable operation in complex public electromagnetic environments. Sixth, fast dynamic response and wide load adaptation requirements. When detecting baggage with different materials and thicknesses, the load of X-ray tubes changes rapidly and drastically; frequent switching between standby, operating and exposure modes is also required. The power supply needs ultra-fast dynamic response: when the load changes stepwise from no load to full load, the output voltage fluctuation shall be less than ±1% with adjustment time<100μs, stabilizing tube voltage and current quickly to maintain consistent imaging quality under various detection conditions. It shall also support energy-saving standby modes to reduce standby power consumption and radiation risks. Seventh, miniaturized integration and low power consumption requirements. Portable security devices, handheld explosive detectors and under-vehicle inspection systems impose strict limits on power supply size, weight and power consumption. The power supply must feature ultra-high integration and power density with minimized volume and weight, while achieving overall conversion efficiency ≥90% to reduce power consumption and support long battery life for portable battery-powered devices. Eighth, intelligent management and automatic fault diagnosis requirements. Civil security inspection equipment generally needs access to security networking platforms for centralized monitoring and management. The power supply shall be equipped with comprehensive communication interfaces and intelligent control functions, supporting remote adjustment of output parameters, real-time operating status monitoring, fault early warning & reporting, and remote device on/off control. It also integrates advanced automatic fault diagnosis to accurately locate fault types and positions for rapid maintenance. Based on the core operating condition requirements and technical challenges of high-voltage power supplies for civil security inspection equipment, this methodology establishes a full-process universal technical framework covering high-stability topology design, full-scenario environmental adaptability optimization, radiation safety protection, long-term reliability design and intelligent management. It adapts to the high-voltage power demands of X-ray scanners, explosive detectors, liquid inspectors, security doors and other civil security devices, providing standardized design criteria for localization and performance improvement of core components for domestic security inspection equipment. Targeting core design challenges in security scenarios including high stability, full-scenario environmental adaptability, radiation safety and high reliability with long service life, this methodology adopts a universal framework of "dual closed-loop resonant soft-switch topology + full-digital high-precision constant voltage & constant current control architecture + multi-level radiation safety interlock system", combined with full-dimensional environmental adaptability design and intelligent management. It completely breaks traditional bottlenecks such as low stability, poor environmental adaptability, insufficient reliability and incomplete safety protection of conventional security power supplies. The core advantage of the dual closed-loop series resonant soft-switch topology lies in its full-range soft-switch operation under wide input voltage and wide load conditions, featuring ultra-low switching loss and high efficiency while offering inherent constant-current characteristics for precise X-ray tube current control, perfectly matching the constant voltage & constant current output demands of X-ray scanners. Combined with the full-digital dual closed-loop control architecture, it realizes independent high-precision regulation of tube voltage and tube current to ensure ultra-stable X-ray output. The multi-level radiation safety interlock system fully complies with national mandatory radiation safety regulations to protect personnel and equipment. The design follows eight core principles: 1. High-stability constant voltage & constant current topology design Optimizing topology and key parameters to achieve high-precision constant voltage & constant current output under all operating conditions with three core criteria: ① LCC series resonant soft-switch topology optimization: Adopting LCC series resonant topology combining advantages of series and parallel resonance, realizing ZVS for primary switches and ZCS for secondary rectifiers across 85VAC~265VAC full input voltage and 10%~100% full load ranges to eliminate hard-switch loss with peak overall efficiency ≥92%. Its inherent constant-current limiting capability effectively restricts short-circuit current and protects X-ray tubes from damage. ② High-precision dual closed-loop control architecture: Adopting a full-digital dual closed-loop system with outer tube voltage loop and inner tube current loop, collecting real-time tube voltage and current signals via over 18-bit high-precision ADC and implementing full-digital PID control through FPGA+DSP. Tube voltage ranges from 50kV to 160kV with continuous adjustment accuracy better than ±0.05%; tube current ranges from 0.1mA to 5mA with control accuracy better than ±1%. Long-term voltage stability reaches ±0.1%/8h and short-term stability ±0.05%, ensuring highly stable X-ray energy and dosage for enhanced imaging clarity and detection accuracy. ③ High-voltage output and filtering optimization: Adopting symmetric dual-input Cockcroft-Walton (CW) cascaded voltage-multiplying rectifier topology, reducing output ripple by over 50% compared with single-ended circuits while lowering voltage stress on capacitors and rectifiers and simplifying high-voltage insulation design. A multi-stage π-type filtering network with low-ESR low-loss high-voltage polypropylene film capacitors suppresses peak-to-peak ripple within 0.05%. Optimized electric field distribution with voltage equalizing rings and shielding structures prevents corona discharge and noise caused by localized electric field concentration. 2. Full-scenario wide-range environmental adaptability design Building a comprehensive environmental protection system for diverse harsh operating environments with five core criteria: ① Wide temperature adaptability: Adopting industrial-grade wide-temperature components of -40℃~+85℃ to ensure normal startup and stable operation from -40℃ to +55℃ with output fluctuation ≤±0.2%. Embedded temperature sensors enable real-time temperature monitoring and full-range drift compensation algorithms to dynamically adjust control parameters and calibrate outputs against component drift caused by temperature changes. Over-temperature protection triggers derating above 85℃ and safe shutdown above 100℃ to prevent component overheating damage. ② High-altitude low-pressure insulation and corona suppression: Enlarging electrical clearance and creepage distance for altitudes up to 5,000 meters. Optimizing high-voltage electrode structures with large rounded smooth surfaces to avoid electric field concentration, raising corona inception voltage to ensure no corona discharge or insulation breakdown at maximum operating voltage under low air pressure. High-voltage components adopt epoxy resin vacuum potting to eliminate air gaps and prevent gap discharge. ③ High humidity and three-proof protection: Fully sealed metal housing with IP54 or higher protection grade; internal PCB coated with conformal three-proof paint; waterproof dustproof industrial connectors applied throughout. Coastal and high-humidity scenarios adopt IP65 rating with vacuum potting for high-voltage parts to ensure stable long-term operation under 95% RH without insulation degradation or short circuits. Metal structures undergo anodization and anti-corrosion spraying; coastal salt spray environments use 316 stainless steel housings with heavy anti-corrosion coatings. ④ Wide input voltage and grid adaptability: Optimized topology supports stable operation from 85VAC to 265VAC for global grid compatibility, with ride-through capability against voltage surges, sags and short power interruptions up to 200ms to prevent shutdown and unstable X-ray output caused by grid fluctuations. Built-in surge protection withstands ±2kV EFT and ±4kV surges for complex public power environments. ⑤ Vibration and shock resistance: Integrated thickened metal housing optimized via finite element simulation; PCB rigidly connected to housing with multiple metal supports; heavy components potted firmly; connectors anti-loosening and shockproof, enduring 50g impact acceleration and 10g random vibration to maintain structural and electrical stability during transportation, installation and vehicle-mounted operation. 3. Multi-level non-bypassable radiation and electrical safety protection system Adhering strictly to mandatory national standards GB 15208, GB 4793.1 and GB 18871, establishing a four-level non-bypassable safety framework: hardware emergency power cut – device-level safety interlock – system-level radiation protection – operational authority management, ensuring instant high-voltage shutdown under any abnormal conditions to eliminate accidental radiation exposure with six core criteria: ① Hardware emergency power cut: Independent non-bypassable hardware emergency shutdown circuit with normally closed contacts connected in series with all emergency stop buttons and safety interlocks at site, control room and channel entrances. Activation instantly cuts main power and high-voltage output; redundant discharge loops release residual high voltage to safe levels within 100ms. Pure hardware design with highest safety priority and no software bypass allowed. ② Device-level non-bypassable safety interlocks: Interlocks for equipment doors, protective covers, key switches, X-ray shutters and detector status. High voltage and X-ray emission can only be enabled when all interlocks are closed; any open interlock cuts high voltage within 1μs and locks startup until recovery. All interlock circuits adopt dual redundancy to prevent single-point failure. ③ System-level radiation interlock linkage: Linked with infrared human detection at channel entrances, access control, audible & visual alarms and regional radiation monitoring systems. Human intrusion instantly cuts high voltage and stops X-ray emission with alarms triggered; real-time radiation dose monitoring automatically shuts down equipment if exceeding safety thresholds to prevent accidental exposure. ④ Fault safety interlock protection: Overvoltage, overcurrent, short circuit, over-temperature, high-voltage arcing, detector failure, cooling system fault and other abnormalities trigger high-voltage cutoff within 1μs with startup locking, requiring manual reset after troubleshooting. All protections adopt dual hardware & software redundancy with hardware protection having supreme priority. ⑤ Operational authority and interlock management: Three-level access control for operators, maintenance staff and administrators with restricted permissions. Operators cannot modify parameters or bypass safety interlocks; maintenance is only allowed during shutdown; administrators manage configurations. Mandatory pre-start safety self-inspection and audible & visual warnings ensure safe startup. ⑥ Redundant safe energy discharge design: At least two independent high-voltage discharge loops fully release residual charges to safe levels within 100ms during shutdown, emergency stop or fault, eliminating residual high voltage risks for maintenance personnel. 4. Long-term continuous high reliability and long service life design Establishing a four-level reliability system: component derating – circuit redundancy – system fault tolerance – full lifecycle health management with four core criteria: ① Extreme component derating: Strict industrial maximum derating standards applied to all components: power device voltage stress ≤50% rated, current stress ≤40% rated, temperature stress ≤60% rated; high-voltage capacitor voltage stress ≤50% rated; resistor power stress ≤50% rated; magnetic core flux density ≤30% saturation flux density, greatly reducing operational stress and extending service life to ensure MTBF ≥1×10⁵h and design life ≥10 years. ② Full-link redundancy: N+1 modular redundancy for front-end PFC and rear-end resonant units with automatic isolation of faulty modules while remaining modules carry full load without shutdown. Dual redundancy adopted for control power, drive circuits, sampling circuits, references and safety interlocks for seamless switching upon single circuit failure. ③ Long-life optimization: Selecting long-life high-reliability industrial components, eliminating vulnerable electrolytic capacitors and cooling fans; adopting long-life film & ceramic capacitors with natural cooling or liquid cooling. Silicon carbide Schottky rectifiers deliver far longer service life than silicon diodes. All core components undergo accelerated life testing and aging screening to eliminate early failures. ④ Full lifecycle health management and fault early warning: FPGA+DSP based health monitoring collects comprehensive real-time data including input/output voltage/current, tube parameters, component temperatures, operating hours, high-voltage arcing counts and fault logs. Reliability models and machine learning assess health status and remaining service life with early warnings for performance degradation, capacitor aging, insulation deterioration and potential faults. Real-time data uploads to security platforms enable predictive maintenance, reducing maintenance costs and unplanned downtime. 5. Low electromagnetic interference and electromagnetic compatibility design Building a full EMC optimization system: source suppression – conducted filtering – radiation shielding – grounding optimization with four core criteria: ① Source interference reduction: LCC resonant soft-switch topology lowers dv/dt and di/dt during switching to minimize EMI at the source. Optimized laminated busbar layouts shorten power loops and reduce parasitic inductance and radiation; high-voltage transformers adopt shielding windings to suppress common-mode interference. ② Conducted interference suppression: Two-stage EMI filtering at input with common-mode, differential-mode and spike suppression using high-permeability nanocrystalline common-mode inductors for superior high-frequency filtering. High-voltage filtering and RC/RCD snubbers at power and rectifier devices eliminate switching spikes, meeting the highest grades of GB/T 9254 and GB/T 17626. ③ Radiated interference suppression: Fully sealed cold-rolled steel shielding housing with shielding efficiency ≥60dB; conductive gaskets at seams eliminate leakage; honeycomb waveguide vents; shielded power and signal cables with 360° double-end grounding. Independent shielding cavities separate high-voltage and low-voltage control sections to prevent interference coupling into detector signal circuits, ensuring no radiation impact on surrounding electronic devices. ④ Grounding and anti-interference optimization: Star single-point grounding separating power ground, analog ground, digital ground, shielding ground and chassis ground to eliminate ground loop noise. Comprehensive anti-interference protection achieves Grade 4 immunity per GB/T 17626 for ESD, EFT, surges, RF induced conduction, power frequency magnetic fields and pulse magnetic fields, ensuring stable operation in complex public electromagnetic environments without interference from mobile networks and monitoring systems. 6. Fast dynamic response and wide load adaptation design Optimizing control loops and topology for rapid load changes during baggage detection with three core criteria: ① High-speed dual closed-loop control: Enhanced loop bandwidth with tube current inner loop and tube voltage outer loop plus load feedforward prediction to drastically improve dynamic response. Output fluctuation ≤1% with settling time <100μs under no-load to full-load step changes, stabilizing tube voltage/current rapidly for consistent imaging with varying baggage thickness and materials. ② Wide load range compatibility: Stable operation from no load to 120% overload with output stability better than ±0.05%; switchable constant voltage / constant current modes adapting to diverse inspection scenarios and target objects. ③ Energy-saving standby mode: Three operating modes (standby / preheat / working) automatically activated according to baggage presence. Standby power ≤5W reduces energy consumption and radiation risk; fast switching to full output within 1ms ensures continuous detection and stable imaging. 7. Miniaturized integration for portable device adaptation Adopting high-frequency, integrated and modular design for extreme miniaturization, light weight and low power consumption with three core criteria: ① High-frequency design: Switching frequency raised to 100kHz~300kHz drastically reduces size and weight of high-voltage transformers, inductors and capacitors; planar transformers and integrated magnetics further boost power density ≥200W/in³. ② High-density modular integration: Integrated power modules and thick-film hybrid circuits combine switches, drivers and protections into single units to reduce component count and PCB area; multi-layer PCB and double-sided mounting maximize space utilization. Micro multi-channel POL high-voltage modules ≤1cm³ are directly integrated onto detector PCBs for photomultiplier power in handheld explosive detectors. ③ Low power consumption for battery operation: Optimized topology achieves peak efficiency ≥90% and light-load efficiency ≥85%; multi-level low-power management with standby power ≤1mW supports long battery life for portable devices. Wide input compatibility covers 12V~24V lithium battery power supplies. 8. Intelligent management and compliance design Building comprehensive intelligent control and communication frameworks while fully meeting national regulations and global market access requirements with two core criteria: ① Intelligent control and networking: Integrated RS485, Ethernet, WiFi supporting Modbus, ONVIF for seamless connection with security platforms and smart city systems, enabling remote on/off, parameter configuration, status monitoring, fault alarming and firmware upgrades for centralized multi-device management. High-definition touch HMI supports local parameter setting, status viewing and fault log query for convenient on-site operation. ② Full compliance certification: Fully complying with GB 15208, GB 4793.1, GB 18871, GB/T 9254 and GB 17625.1; supporting rapid certification for EU CE, US FCC and UL to meet domestic and global market access standards. This methodology forms a complete technical framework covering high-stability topology, full-scenario environmental optimization, multi-level radiation safety, long-term reliability and intelligent management for civil security inspection high-voltage power supplies, thoroughly solving traditional pain points including low stability, poor environmental adaptability, insufficient reliability and incomplete safety protection. The LCC resonant topology plus full-digital dual closed-loop control achieves ±0.05% voltage stability and ±1% tube current accuracy; full-dimensional environmental design ensures stable operation at -40℃~+55℃, altitudes up to 5,000m and 95% RH humidity; four-level non-bypassable safety systems satisfy mandatory radiation regulations; four-stage reliability design delivers MTBF above 1×10⁵h and service life over 10 years. Widely applicable to X-ray baggage scanners, explosive detectors, liquid inspectors, security doors, under-vehicle inspection systems and other civil security devices, this methodology provides core technical support for localized substitution and high-end performance breakthroughs of key components for domestic security inspection equipment.