A charging station is part of the grid infrastructure installed along a street, parking lot or in a home garage; its primary purpose is to supply the power to the PHEV for charging the battery. An onboard charger is responsible for the final stage of charging the battery pack. It takes the AC power source from the EVSE and transforms the power into the required battery-charging profile.
Despite having separate functions for charging a vehicle, similarities in the naming conventions (“on-” and “off-” board chargers) have caused general confusion about these two types of systems.
While the onboard charger has to condition (convert to high-voltage DC) power from the off-board AC charger before supplying it to the battery management system (BMS), the off-board DC charger works without an onboard charger and interfaces directly with the BMS.
In Texas Instruments' whitepapers, they will attempt to explain onboard chargers, how they work and why they’re used. TI will also explain charging stations and how they interact with onboard charger and EV BMS systems, along with various power-architecture implementations.
Read the whitepapers here.