Since the first electric vehicle was launched in the 19th century, rechargeable batteries have been used as its power source. For an electric vehicle, battery charging equipment is one of the indispensable subsystems. Its function is to convert the power of the power grid into the power of the on-board battery of the electric vehicle. There are different ways to classify electric vehicle charging devices, which can be generally divided into on-board charging devices and off-board charging devices.
On-board charging devices refer to devices installed on electric vehicles that use ground AC power grids and on-board power supplies to charge battery packs, including on-board chargers, on-board charging generators, and operating energy recovery charging devices. An AC power cable with a plug is directly plugged into the charging socket of the electric vehicle to charge the battery. On-board charging devices usually use contact chargers with simple structures and convenient control, or they can be inductive chargers. It is designed completely according to the types of on-board batteries and is highly targeted. Off-board charging devices, namely ground charging devices, mainly include dedicated chargers, dedicated charging stations, universal chargers, charging stations for public places, etc. It can meet various charging methods for various batteries. Usually, the power, volume and weight of non-on-board chargers are relatively large so that they can adapt to various charging methods.
In addition, according to the different ways of energy conversion when charging electric vehicle batteries, charging devices can be divided into contact type and induction type. With the rapid development of power electronics technology and current conversion control technology, the maturity and popularization of high-precision controllable current conversion technology, the staged constant current charging mode has been basically replaced by the constant voltage current limiting charging mode with continuous changes in charging current and charging voltage. The dominant charging process is still the constant voltage current limiting charging mode. The biggest problem of contact charging is its safety and versatility. In order to make it meet the strict safety charging standards, many measures must be adopted in the circuit to enable the charging equipment to charge safely in various environments. Constant voltage current limiting charging and staged constant current charging are both contact charging technologies. New electric vehicle induction charging technology is developing rapidly. The induction charger uses the transformer principle of high-frequency AC magnetic field to induce electrical energy from the primary side away from the vehicle to the secondary side on the vehicle to achieve the purpose of charging the battery. The biggest advantage of inductive charging is safety. This is because there is no direct point contact between the charger and the vehicle. Even if the vehicle is charged in bad weather, such as rain or snow, there is no risk of electric shock.