Low-temperature physics experiments represent the core frontier of modern fundamental scientific research, covering superconducting quantum device development, condensed-matter ultra-low-temperature characteristic studies, quantum computing prototype verification, low-temperature magnetic measurements, diluted magnetic semiconductor analysis, neutrino detection, and other advanced research directions. Such experiments are conducted at liquid-nitrogen temperature (77 K), liquid-helium temperature (4.2 K), and even ultra-low temperatures down to the 10 mK range inside dilution refrigerators. High-voltage power supplies are essential supporting equipment for low-temperature experimental systems, providing high-precision, high-stability DC high voltage for low-temperature probe stations, superconducting magnet bias systems, cryogenic particle detectors, electrostatic deflection electrodes, low-temperature scanning tunneling microscopes, and quantum device gate-bias units. Their cold-start capability without preheating under extreme cryogenic conditions, long-term operational stability, output voltage accuracy, and ultra-low noise performance directly determine signal resolution, data repeatability, and overall experimental success. Low-temperature physics experiments impose far stricter requirements than conventional industrial or laboratory power supplies: First, **cold non-preheating startup capability**: power output stages are often integrated directly inside cryostats or dilution refrigerators and must start reliably at 4.2 K or even millikelvin temperatures without preheating. Any heating would compromise the cryogenic environment, induce quantum decoherence, shift superconducting properties, and cause total experimental failure. Conventional power supplies suffer threshold drift in semiconductors, abrupt permeability changes in magnetic components, drastic parameter shifts in passive devices, and oscillator stoppage under extreme cold, making cold startup impossible. Second, **full-temperature-range operational stability**: stable output must be maintained from room temperature (300 K) down to 4.2 K, with voltage stability reaching ±10 ppm. Long-duration experiments lasting days to weeks require zero measurable drift, whereas ordinary power supplies exhibit drift exceeding 1 %, failing precision requirements. Third, **ultra-low noise output**: experiments detect nanovolt to picovolt quantum signals and superconducting currents. Power-supply ripple and noise directly couple into measurement channels, degrading SNR and submerging weak characteristic signals. Required specifications include peak-to-peak ripple ≤ 1 mV and voltage noise density ≤ 10 nV/√Hz@1 kHz. Fourth, **cryogenic insulation and structural reliability**: conventional insulating materials embrittle, crack, and lose dielectric strength under extreme cold. High-vacuum cryogenic environments drastically reduce surface flashover thresholds, increasing partial discharge and insulation breakdown risks. Differential thermal expansion causes solder joint detachment, structural cracking, and contact failure. Fifth, **experimental compatibility**: seamless integration with measurement and control systems, high-resolution programmability, remote synchronization, real-time monitoring, and safety interlocks are mandatory. Designs must comply with GB 4793.1-2007 and GB/T 18268.1-2010 safety and EMC standards. This methodology establishes a comprehensive technical framework covering wide-temperature-range topology design, preheat-free ultra-low-temperature startup optimization, full-temperature stability control, cryogenic insulation reliability engineering, and experimental compatibility. It satisfies high-voltage demands for liquid-nitrogen, liquid-helium, and millikelvin environments, providing standardized design principles for domestically developed low-temperature scientific instrumentation. To address cold startup, full-range stability, and ultra-low-noise challenges, the methodology adopts a **split architecture: room-temperature control & drive unit + cryogenic power conversion unit**, combined with wide-temperature soft-switching topologies, all-fiber isolation communication, and full-range adaptive compensation control. It overcomes traditional limitations in cryogenic compatibility, cold-start failures, large thermal drift, and poor stability, achieving reliable preheat-free operation at 4.2 K and ±10 ppm stability across 300 K–4.2 K. The design follows five core principles: 1. **Split-system topology**: Temperature-sensitive circuits (control, driving, references, communication) remain outside the cryostat at room temperature. Only power conversion, high-voltage rectification, and filtering stages reside inside the cold chamber. All control and feedback signals transmit via high-withstand-voltage optical fibers (≥100 kV isolation), eliminating metallic signal-path drift, attenuation, EMI, and heat leakage into the cryostat. The cold-stage power topology uses a quasi-resonant flyback circuit with minimal components, high boost ratio, and full soft-switching capability stable from 300 K to 4.2 K. It eliminates electrolytic capacitors entirely to prevent freezing failure at low temperatures. Output voltage ranges from 100 V to 10 kV with flexible multiplier configurations. 2. **Wide-temperature component screening**: All cold-stage components undergo full cryogenic characterization. GaN HEMTs are preferred over silicon MOSFETs due to stable two-dimensional electron-gas transport at cryogenic temperatures, minimal threshold drift, and no sharp increase in on-resistance at 4.2 K. SiC Schottky rectifiers deliver near-zero reverse leakage under cold conditions. Capacitors use polystyrene, PTFE, and NP0 ceramic types with minimal capacitance loss and stable ESR at 4.2 K. Precision alloy resistors maintain tight tolerance across temperatures. Magnetic cores adopt nanocrystalline materials with stable saturation flux density and permeability under extreme cold. 3. **Full-temperature adaptive digital control**: An FPGA+MCU main controller at room temperature communicates with cryogenic temperature sensors and high-precision voltage/current samplers via optical fibers. Embedded multi-parameter thermal-drift models dynamically adjust switching frequency, duty cycle, and dead time to compensate component variations across the entire temperature range. High-speed control loops ≥1 MHz ensure rapid precision regulation. 4. **Ultra-low-noise output optimization**: Quasi-resonant soft switching eliminates switching noise at the source. Operating frequencies exceed 100 kHz to avoid overlapping detection bandwidths. A three-stage low-pass filtering architecture suppresses wide-spectrum ripple: film capacitors for low frequencies, active RC filtering for midband noise, and parallel NP0 capacitors plus feedthrough filters for ultra-high frequencies above 10 MHz. Final ripple is controlled ≤ 1 mV with noise density ≤ 10 nV/√Hz@1 kHz. The cold power stage adopts a dual Permalloy–aluminum shield for complete electromagnetic isolation. 5. **Experimental system compatibility**: High-resolution 16-bit programmable voltage adjustment supports remote precision control. Nanosecond synchronization interfaces integrate with probe stations, lock-in amplifiers, spectrum analyzers, and data acquisition systems. Comprehensive real-time monitoring records full operational parameters. Multi-level redundant safety interlocks instantly cut high voltage during faults to protect superconducting quantum devices and cryogenic infrastructure. **Ultra-low-temperature preheat-free startup optimization** is critical: - All components undergo strict 300 K–4.2 K characterization to eliminate cold-sensitive devices. - A self-resonant auxiliary startup circuit using cryo-stable GaN devices enables oscillator-independent cold power-up without preheating. - Adaptive drive voltage boosting compensates threshold shifts in GaN at low temperatures. - Gradual soft-start ramps prevent inrush current and overvoltage during initial cold power application. - Fully optical isolated push-pull driving ensures stable gate control at 4.2 K. - Full-range ZVS soft-switch boundaries are maintained throughout startup via real-time frequency adaptation. **Long-term stability enhancement** ensures multi-week experimental reliability: - Multi-physics thermal-drift models enable real-time compensation of temperature, load, and input variations, achieving stability better than ±10 ppm over 8 hours. - Onboard self-calibration corrects component aging throughout the device lifetime. - Nanocrystalline magnetic cores with conservative flux derating prevent cold saturation. - Optimized winding structures minimize cryogenic losses and maintain stable transformer parameters. - Full-solid mechanical vibration-free design eliminates noise from fans or relays. - Optimized filtering preserves low-noise performance permanently under cold conditions. - Star-point grounding and full cryostat shielding eliminate ground-loop interference. - Adaptive high-dynamic-range PID control maintains stable output during large load impedance variations typical for superconducting devices. **Cryogenic insulation and structural reliability engineering**: - Insulating materials include polyimide, PEEK, and PTFE, maintaining toughness and dielectric strength at 4.2 K. - Cryo-modified epoxy potting eliminates internal air gaps to prevent vacuum partial discharge. - Graded electric-field insulation reduces localized high field stress; surface polishing eliminates flashover-prone micro-defects. - Thermal-expansion-matched material combinations and flexible buffer structures avoid cracking during thermal cycling. - Titanium/aluminum housings enhance mechanical stability across temperature cycles. - Gold-tin or high-lead solders and cryogenic hermetic connectors guarantee long-term electrical contact reliability under repeated thermal shocks. **Full-range safety and EMC compliance**: - Six-level hardware-software protection provides fault response ≤1 μs, including overvoltage, overcurrent, short-circuit, overtemperature, vacuum interlock, and system emergency stop. - Complete interlocking with cryostat vacuum, refrigerator status, and experiment safety loops prevents dangerous high-voltage activation. - Fast high-voltage discharge reduces residual energy within 100 ms during shutdown or faults. - Three-stage EMI filtering and double shielding comply with GB/T 18268.1 EMC requirements, ensuring no interference with ultra-low-level quantum measurement instruments. In conclusion, this integrated methodology resolves critical limitations of conventional power supplies for cryogenic environments, achieving reliable preheat-free startup at 4.2 K, ±10 ppm full-temperature stability, ultra-low ripple below 1 mV, and long-term structural reliability under extreme thermal cycling. It fully satisfies the rigorous demands of superconducting quantum research, condensed-matter physics, low-temperature magnetism, and particle detection, providing core technical support for advanced domestically manufactured low-temperature experimental instrumentation and fundamental scientific research.