Electric vehicle (EV) chargers—from onboard chargers (OBC) to DC fast chargers—rely heavily on magnetic components. The power density, efficiency and reliability of every charger depends on the inductors, transformers and filters inside.
This guide covers the key magnetic components in EV chargers and their design requirements.
Shaanxi SiRui Technology Co., Ltd. manufactures PFC inductors, LLC transformers, common mode chokes and current sensors for EV charger applications. Contact: sales@sirui-tech.com | Web: www.sirui-tech.com
1. EV Charger Types
- Onboard Charger (OBC): 3.3–22 kW, converts AC grid to battery DC (200–800 V)
- DC Fast Charger: 50–350 kW+, 3-phase AC to DC, stationary
- Wireless Charger: large air-gap transformer (coupled inductors)
2. Key Magnetic Components in OBC
PFC Inductor
High current (10–50 A). Powder core (Sendust, MPP, High Flux) for stable DC bias. Low DCR for efficiency.
LLC Resonant Transformer
Isolation between grid and battery (safety critical). High frequency (100–500 kHz). Ferrite core with litz wire winding. ZVS for 97%+ efficiency.
Common Mode Choke
Reduces conducted EMI to meet CISPR 25 / CISPR 32. Nanocrystalline core preferred for high attenuation in small size.
3. DC Fast Charger Magnetics
Essentially large power supplies: 3-phase PFC inductors (100+ A), multiple LLC modules in parallel, output filter inductors, and multi-stage EMI filters.
4. Design Challenges
- High efficiency: 96–97% target; every 0.1% affects EV range
- High power density: OBC space is limited; planar transformers increasingly used
- Wide battery voltage: 200–800 V platforms require LLC regulation across range
- Automotive reliability: AEC-Q200, -40 to +125°C, vibration
- Safety: 4 kV+ isolation, reinforced insulation between grid and battery
5. Magnetics Selection
| Component | Core Material | Typical |
|---|---|---|
| PFC inductor | Powder core (Sendust) | 100–500 μH, 10–50 A |
| LLC transformer | Ferrite (PC95) | 100–500 kHz, litz wire |
| CMC | Nanocrystalline | 1–50 mH, high attenuation |
| Output filter | Powder core / iron | 100–500 μH, high current |
6. Sirui-Tech EV Products
- PFC inductors: powder core, 10–50 A, custom values
- LLC resonant transformers: ferrite + litz wire, high frequency
- Common mode chokes: nanocrystalline, automotive grade
- Output filter inductors: high-current powder core
Conclusion
EV chargers demand the highest efficiency and power density in power magnetics. The PFC inductor and LLC isolation transformer are the largest and most critical components. Automotive qualification and safety isolation are non-negotiable.
Need EV charger magnetics? Contact Sirui-Tech at sales@sirui-tech.com with your charger power and battery voltage range.