Finding
EV power distribution is moving from passive fuse boxes to smart PDUs with semiconductor switches, driven by zonal architectures and 48-volt systems
The high-voltage PDU, often called the HV junction box or battery disconnect unit (BDU), connects the traction battery to the inverter, charger, DC-DC converter and thermal loads through contactors, a precharge circuit and fuses. A pyrofuse fires in a crash or severe short to open the circuit in milliseconds. On the low-voltage side, smart PDUs replace fuses and relays with MOSFET eFuses that switch, measure and report each load.
Two shifts drive the change. Zonal electrical architectures place power distribution in zone controllers, so each zone becomes a smart PDU for its corner of the car; Tesla's Cybertruck and Rivian's Gen 2 vehicles moved this way, and Cybertruck runs a 48-volt low-voltage bus. ADAS and autonomy computers draw hundreds of watts with fast transients, so they need dedicated, monitored channels to avoid brownouts and resets.
The supply chain is electromechanical more than semiconductor. HV contactors come from TE Connectivity, Sensata (Gigavac), Panasonic, Omron and China's Hongfa, which leads high-voltage DC relay volume; pyrofuses from Autoliv, Daicel and Mersen; fuses from Littelfuse, Eaton (Bussmann) and Mersen. BDUs and junction boxes are assembled by battery makers and harness suppliers such as Lear, Yazaki, Sumitomo Electric and Aptiv.
Domains
Two Voltage Domains
Every EV has a high-voltage domain and at least one low-voltage domain fed by the DC-DC converter.
| Domain | Sources | Loads | PDU job |
|---|---|---|---|
| High voltage (400-800 V) | Traction battery | Traction inverter, OBC, DC-DC, HV heater, A/C compressor | Isolation, safe switching, fault protection, service disconnect |
| Low voltage (12 V or 48 V) | DC-DC converter, LV battery | ECUs, lighting, pumps, infotainment, ADAS compute | Load protection, diagnostics, sleep and wake control |
Hardware
PDU Building Blocks and Suppliers
Content varies by automaker; these blocks appear in nearly every EV.
| Block | Function | Suppliers |
|---|---|---|
| HV contactors | Connect and disconnect the pack from the HV bus | TE Connectivity, Sensata Gigavac, Panasonic, Omron, Hongfa |
| Precharge circuit | Limits inrush current into DC-link capacitors at wake-up | Contactor and resistor makers; BDU integrators |
| Pyrofuse | Explosive disconnect in a crash or severe fault | Autoliv, Daicel, Mersen |
| HV and LV fuses | Overcurrent protection on each branch | Littelfuse, Eaton Bussmann, Mersen |
| Current and voltage sensing | Branch and bus measurement for diagnostics | LEM, Allegro, Infineon, Melexis |
| Isolation monitoring | Detects leakage from HV to chassis | BMS and BDU suppliers |
| Solid-state switches (eFuses) | Electronic switching with per-load diagnostics | Infineon, ST, NXP, onsemi, Texas Instruments |
| BDU and junction box assembly | Integrates the blocks above in one enclosure | Lear, Yazaki, Sumitomo Electric, Aptiv, battery makers |
Smart PDUs
Smart PDUs and Compute Loads
Semiconductor switching gives per-load control and data; compute loads make it necessary.
| Topic | Conventional PDU | Smart PDU |
|---|---|---|
| Switching | Contactors, relays and melting fuses | MOSFET eFuses and electronically controlled relays |
| Diagnostics | Branch level, after a fault | Per-load current, temperature and fault reporting |
| Fault response | Fuse replaced in service | Resettable trip; software-set limits |
| Compute loads | Shared fused branch | Dedicated channels sized for high sustained draw and fast transients |
| Standby | Fixed always-on circuits | Software-controlled sleep and wake with low quiescent loss |
| Cost and supply | Lower cost, mature supply | More semiconductor content; zonal controllers |
Sources
Sources and scope
- Scope
- EV Power Distribution Units
- Sources
- Supplier disclosures (TE, Sensata, Hongfa, Autoliv, Mersen, Littelfuse, Eaton); Tesla and Rivian architecture disclosures
- Updated
- October 2026