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Compared with traditional oil cars, pure electric cars have many advantages, not to list here, but one trouble with pure electric cars is the need to consider the length of charging time and battery life. There are so many compromises in the hybrid field such as plug-in, add-on, etc., which do not require a larger battery capacity and shorten the charging waiting time compared to pure electric vehicles.
In the field of pure electric vehicles, it is difficult to unilaterally optimize the charging time or battery life, because the battery life is related to the size of the charging multiplier, and in general the larger the charging and discharging multiplier, the smaller the number of cycles.
In order to ensure that the cycle charge times of the battery can be between 800~1000, usually the charge multiplier should be between 0.5C~0.25C, using the national grid power supply, using the vehicle charger to charge the power battery, which belongs to the slow charging scheme, and the supporting public facilities are AC chargers.
In order to cope with emergency, the battery should be fully charged to 80% of the maximum capacity within 15~30minutes, and the corresponding charging rate should be between 2C~4C. This is a fast charging scheme, and the supporting public facilities are DC chargers.
The chargers at home and abroad are similar in principle, but slightly different in appearance.
Compared with DC charger, AC charger is low cost, simple structure, more friendly to battery, and suitable for popularization in a large area.
The main function of AC charger (including GB/T and non-GB/T) is to draw out single-phase or three-phase electricity, the charger only plays the role of current transfer station, and the subsequent rectification + DC/DC conversion is done by vehicle charger.
The GB/T AC charging post is based on the original AC charging post, adding some commercial modules (such as human-machine interface, billing module, alarm module, etc.) and control guidance circuit, which is the core content of the AC charging post interface technology. And in order to be compatible with both single-phase power and three-phase power, the 7-terminal structure finally adopted by the GB/T AC charging post interface.
The main role of the control guidance circuit is used to confirm whether the charging interface and the charging socket are connected, and then perform periodic detection during the charging process to determine whether to continue charging or stop charging, etc.
The following details describe the working principle of the control GB/T EV charger guide circuit.
(1) The vehicle control device confirms whether the vehicle plug and the vehicle socket are connected by detecting the resistance value between PE and monitoring point 3.
(2) The power supply control device on the charging post side determines whether the power supply plug and the power supply socket are connected by detecting the voltage value of monitoring point 4 or testing point 1.
When both vehicle interface and power supply interface are confirmed to be connected, the charger switches switch S1 from 12V connection state to PWM state and waits for the vehicle control device to close switch S2. At this time, the peak voltage of test point 1 is 9V and the CP terminal generates a 1KHz PWM wave whose duty cycle represents the rated current size of the charger. When the vehicle side switch S2 is closed, it means the vehicle is ready for charging, at this time the peak voltage of test point 1 is 6 V. After confirming the vehicle is ready, the charger closes the contactors K1 and K2 to make the AC circuit conductive and charging starts.
During the charging process, the car charger EV performs periodic detection of the detection point to confirm the connection status of the charging connection device and whether the vehicle is in a chargeable state, with a detection period of no more than 50ms.
(1) During the charging process, the charging control device continuously detects detection point 4 and detection point 1. If the power supply interface is detected to be disconnected, the power supply control device switch S1 switches to 12V and disconnects the AC power supply circuit.
(2) During the charging process, the vehicle control device continuously detects detection point 2 and detection point 3, and if the vehicle interface is judged to be disconnected, the vehicle control device controls the vehicle charger to stop charging and disconnects switch S2.
The general principle is as mentioned above, the control guide circuit is the soul of the charging post interface technology, which is crucial for electric vehicle designers as well as users, please refer to GBT 20234-2011, the GB/T, for more details.