Paths to Improve Conversion Efficiency of AC-DC Power Supplies

1. Core Factors Affecting Conversion Efficiency
AC-DC high-voltage power supplies are key links connecting the power grid to high-voltage electrical equipment. Their conversion efficiency is mainly affected by switching losses, conduction losses, magnetic component losses, and control losses. In traditional AC-DC power supplies, switching losses of switching tubes (e.g., IGBTs) account for 40%-50% of total losses, magnetic component (transformer, inductor) core and copper losses account for 30%-35%, and conduction losses account for 15%-20%. For example, a traditional 10kW/400V output AC-DC high-voltage power supply has a conversion efficiency of approximately 88%-90%. Long-term operation generates significant heat, increasing cooling costs and shortening component lifespan.
2. Key Technical Paths for Efficiency Improvement
(1) Topological Structure Optimization
Interleaved Power Factor Correction (PFC) topology is adopted, with multiple PFC modules operating in an interleaved manner to reduce input current ripple, improve power factor (from 0.92 to over 0.99), reduce current stress on switching tubes, and lower switching losses. At the high-voltage output end, LLC resonant topology replaces traditional hard-switching topology. Utilizing the resonant characteristics of the resonant cavity, it achieves Zero-Voltage Switching (ZVS) and Zero-Current Switching (ZCS) of switching tubes, reducing switching losses by 60%-70%. For example, an AC-DC power supply with 15kW/600V output using "interleaved PFC + LLC resonance" topology achieves a conversion efficiency of 95.5%, a 5-7 percentage point improvement over traditional topologies.
(2) Application of Wide-Bandgap Semiconductor Devices
Wide-bandgap semiconductor devices such as SiC (silicon carbide) and GaN (gallium nitride) have high breakdown voltage, fast switching speed, and low on-resistance, significantly reducing switching and conduction losses. Compared with traditional Si-IGBTs, SiC-MOSFETs reduce switching losses by 80% and on-resistance by 50%; GaN-HEMTs have a switching speed 5 times that of Si-IGBTs and no reverse recovery loss. In a 20kW/800V AC-DC power supply, replacing Si-IGBTs with SiC-MOSFETs increases conversion efficiency to 96.8%, while reducing power supply volume by 40% and cooling requirements by 35%.
(3) Optimization of Magnetic Components
Nanocrystalline alloy cores replace traditional silicon steel sheet cores. Nanocrystalline cores have 5-10 times the permeability of silicon steel sheets and reduce core losses by 40%-50%. In transformer design, planar transformer structures use multi-layer PCB windings instead of traditional enameled wire windings, reducing skin and proximity effects in windings and lowering copper losses by 15%-20%. Additionally, magnetic integration technology integrates PFC inductors and LLC transformers into the same core, reducing the number of magnetic components and further lowering losses. For example, in a 5kW/300V AC-DC power supply, using nanocrystalline planar transformers reduces magnetic component losses from 120W to 55W, increasing efficiency by 2.5 percentage points.
(4) Improvement of Control Strategies
Model Predictive Control (MPC) replaces traditional PID control. MPC optimizes the on-time and frequency of switching tubes in advance based on the power supply's dynamic characteristics and load changes, reducing the number of switching actions and lowering control losses. Meanwhile, an adaptive PFC control algorithm is introduced to adjust the operating mode of PFC modules in real time based on input voltage and load changes, maintaining high power factor and efficiency even under light load conditions (load rate <20%). In a 1kW/200V AC-DC power supply, MPC control increases conversion efficiency under light load from 82% to 89%.
3. Application Scenarios and Future Trends
High-efficiency AC-DC high-voltage power supplies are widely used in new energy vehicle charging piles (120kW charging piles achieve 96% efficiency, reducing energy waste during charging) and high-voltage power supply systems in data centers (efficiency increased to 97%, lowering data center energy consumption). In the future, with the maturity of multi-level topologies (e.g., three-level, five-level) and SiC full-bridge technology, the conversion efficiency of AC-DC power supplies will exceed 98%, while achieving higher voltage (e.g., 10kV) and higher power (e.g., 1MW) output to meet the development needs of new energy and industrial equipment fields.