Two charging architectures — different sensing priorities.
EV charging is built around two main power-conversion arrangements: an on-board charger (OBC), which converts AC from the grid inside the vehicle, and an external DC fast charger, which performs the conversion in the charging station and supplies regulated DC directly to the traction battery.
On-board conversion
The vehicle contains the rectifier/PFC stage and isolated DC/DC converter. Typical charging power is around 3.7–22 kW depending on the vehicle and supply.
Off-board conversion
High-power PFC and isolated DC/DC stages are located in the charger. Power can range from about 50 kW to several hundred kilowatts.
AC grid → PFC → DC link → isolated DC/DC → battery
The input-current measurement supports power-factor correction and grid-side overcurrent protection. DC-link voltage is monitored between the PFC and DC/DC stages, while battery-side current and voltage close the charging-control loop.
Three-phase grid → high-power conversion → vehicle DC interface
The architecture is functionally similar to an OBC but at much higher current. The charger must regulate output current and voltage precisely, supervise isolation before connection, and manage substantial thermal stress at high continuous power.
What each measurement is doing
AC input current
Used for PFC control and grid-side overcurrent protection in both OBC and DC-fast architectures.
DC-link voltage
Supervises the intermediate energy buffer and provides a control reference for the isolated DC/DC stage.
Battery-side current
Controls charge rate, supports battery protection and becomes bidirectional in V2G/V2H-capable systems.
Battery / output voltage
Ensures the charger stays within the battery's permitted voltage envelope and supports delivered-energy measurement.
Insulation monitoring
Before a DC fast charger connects to the vehicle, the floating DC output must be checked for adequate insulation to earth by the system's IMD function.
V2G, V2H and V2L change the measurement requirement.
When energy flows from the vehicle back to the grid, home or external load, battery-current measurement must remain accurate in both directions. Directional asymmetry, offset drift and long-term stability therefore become more important than in a purely unidirectional charging system.
Where exported energy has contractual value, the discharge-direction measurement can become part of the transaction chain and may be subject to market-specific legal-metrology requirements.
OBC and DC-fast charging impose different constraints
| Criterion | On-board charger (OBC) | DC fast charger |
|---|---|---|
| Typical power | 3.7–22 kW | 50–400 kW+ |
| Typical output current | 16–32 A per phase on AC side | 125–500 A on DC output |
| Typical DC output voltage | ~200–500 V battery pack | ~200–1,000 V |
| Dominant integration constraint | Vehicle volume and thermal budget | High continuous current and outdoor operation |
| Bidirectionality | Increasingly common | Still less common |
| Specific safety focus | Vehicle galvanic isolation | Insulation monitoring before connection |
Electrical safety, interface and communication references
| Reference | Domain | Measurement relevance |
|---|---|---|
| IEC 61851 series | Conductive EV charging systems | Charging modes and general safety requirements |
| IEC 62196 | Plugs, socket-outlets and vehicle connectors | AC/DC interface definition |
| ISO 15118 | Vehicle-to-grid communication | Digital exchange of current and voltage limits |
| IEC 61000 series | Electromagnetic compatibility | Emission and immunity of power-conversion equipment |
| IEC 60364-7-722 | Electrical installations for EV charging | Supply-circuit and residual-current protection |
Sensor selection follows the measurement function.
Continuous-current capability and thermal behaviour can be as important as static accuracy.
Compact size, production cost and thermal budget are major drivers inside the vehicle.
Long-term stability and low thermal drift matter when output measurements contribute to billed energy.
Measurement architecture must be evaluated with the complete insulation and protection concept rather than as an isolated component choice.
Translate the measurement requirement into the right sensing architecture.
Use the Product Selector for a first technical orientation, or share your electrical, mechanical and environmental constraints with our engineering team.