What is on board charger (OBC)?

An on-board charger (OBC), also known as an on-board charger, is a charger fixed on an electric vehicle. It can safely and automatically charge the power battery of the electric vehicle. It is mainly used in chargers that must be "plugged in". ” Rechargeable electric vehicles such as battery electric vehicles (BEV, purely battery-powered) and plug-in hybrid electric vehicles (PHEV)

As the interface between electric vehicles and the public power grid, OBC can convert the alternating current (AC) from the power grid into the direct current (DC) required by the high-voltage battery of electric vehicles to charge the power battery of the electric vehicle; it can also convert the DC power from the power battery. The inverter converts alternating current back to the grid to realize energy conversion between the car's power battery and the grid.

The OBC of new energy vehicles is divided into unidirectional OBC and bidirectional OBC. The circuit includes a power circuit (PFC+ phase-shifted full bridge/LLC) and a control circuit. One-way OBC can only charge the power battery, while two-way OBC can invert the DC power of the power battery into household 220V AC power.

OBC can also provide corresponding protection functions required during charging, including overvoltage, undervoltage, overcurrent, undercurrent, and other protection measures. When the charging system is abnormal, the power supply will be cut off in time. To improve electrical safety, an electrical isolation layer with a withstand voltage of 2500V-3750V is usually required between the grid side and the vehicle side, that is, an isolated onboard charger (OBC). Currently, the vast majority of electric vehicles are equipped with isolated on-board chargers.

                  

（Picture from 车载充电机OBC(On-board Charger)的技术方向与碳化硅应用 - 知乎 (zhihu.com)）

Power level: Domestic and overseas new energy vehicles have different charging powers. Common OBC charging powers are 3.3 kW, 6.6 kW, 11 kW, and 22 kW. The 11kW OBC means that it takes 6 hours to fully charge the 66kWh power battery.

Conversion efficiency: Efficiency is a very important goal and is closely related to the heat dissipation method of the entire unit. More than 90% of OBCs are very energy-saving and time-saving. OBC is particularly suitable for high-power systems, which means it can consume less power and charge faster.

Cooling methods: There are two methods: active air cooling and liquid cooling. After the power increases to 11KW, the demand for liquid cooling increases.

Product Features:

1. It has the function of high-speed CAN network and BMS communication to determine whether the battery connection status is correct; and obtain battery system parameters and real-time data of groups and individual batteries before and during charging.

2. The working status, working parameters and fault alarm information of the charger can be uploaded through the highway CAN communication network and vehicle monitoring system, and the start or stop charging control instructions can be accepted.

3. Complete safety protection measures:

• AC input overvoltage protection function.
• AC input undervoltage alarm function.
• AC input overcurrent protection function.
• DC output overcurrent protection function.
• DC output short circuit protection function.
• Output soft start function to prevent current impact.

During the charging process, the charging function ensures that the temperature, charging voltage, and current of the power battery do not exceed the allowed values; it also has a single battery voltage limiting function that automatically adjusts the charging current dynamically based on BMS battery information.

Automatically determine whether the charging connector and charging cable are connected correctly. When the charger is properly connected to the charging pile and the battery, the charger can start the charging process; when the charger is abnormally connected to the charging pile or the battery, charging will be stopped immediately.

The charging interlock function ensures that the vehicle cannot be started before the charger is disconnected from the power battery.

High-voltage interlock function, when there is high voltage that endangers personal safety, the module is locked and has no outlet.

 Flame retardant function.

These functions greatly protect our personal safety and battery life

Choosing an efficient charger for your battery not only saves energy and money but also improves charging safety！

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