Project Background
The customer, a manufacturer of charging station modules, faced issues with their 30kW DC fast charging module where the transformer's temperature rise was excessive at full power, leading to increased fan speed and noise, while efficiency metrics struggled to meet next-generation energy efficiency requirements.
Technical Challenges
- At a switching frequency of 100kHz, both core loss and copper loss needed to be reduced simultaneously;
- Limited internal space in the module meant the transformer footprint could not be enlarged;
- Required to pass 100% high-voltage insulation testing and extended full-load burn-in;
- High annual volume demand required consistent quality and reliable delivery capability.
Our Solution
Adopted a design approach using low-loss power ferrite cores and litz wire windings:
- Core material reselected based on actual operating flux density and frequency, cutting core loss by approximately 20%;
- Primary and secondary windings use litz wire to reduce copper loss caused by high-frequency skin effect;
- Sandwich winding structure lowers leakage inductance, mitigating voltage spikes across switching devices;
- Bobbin designed with increased creepage distance and potted with high-thermal-conductivity epoxy to improve heat dissipation paths.
Delivered Results
- Full-load efficiency improved from 96.2% to 98.0%, meeting the customer's energy efficiency targets;
- Transformer hotspot temperature rise dropped by 11°C, significantly reducing overall system noise after fan speed adjustment;
- All units passed 100% high-voltage insulation and full-load burn-in testing, with annual deliveries exceeding 200,000 units after mass production;
- The solution has been extended to the customer's 60kW platform.