What Is the Application of Power Supply, CAN, RS485/232 Isolation on DC Charging Piles

Figure 1 Schematic diagram of charging pile

1. The main communication method of DC pile

1. CAN-bus: According to the GB/T 20234.1-2015 "Connecting Device for Conductive Charging of Electric VehiclesThere are multiple CAN interfaces for one stack of two chargers and one stack of four chargers. At the same time, the control unit and the charger generally also communicate through CAN to control the entire charging process.

2. RS485: The electric energy meter, insulation detection and control unit are generally connected through RS-485 to complete the statistical charging of electricity, leakage detection, etc.

3. RS232: The functional components such as swiping card, micro-printing, etc. and the control unit are generally connected by RS-232 to complete functions such as identification, deduction, and bill printing.

4. Wifi, GPRS, industrial Ethernet, etc.: Mainly connect to the Internet of Vehicles, server background, etc., to facilitate remote system monitoring, upgrade, data management, etc.

Figure 2 shows the communication relationship diagram of an example of general technical specifications for DC chargers of the State Grid.

Figure 2 The communication relationship diagram of the charging pile of the State Grid

2. Power supply, CAN, RS485/232 isolation application solutions on DC piles

As far as CAN, RS485 and RS232 communication methods are concerned, whether it is DC pile or AC pile, the general communication distance is not very long, and the number of nodes does not need to be many. General transceivers can meet the baud rate and number of nodes. Demand. For DC piles, other protection and reliability requirements must also be emphasized:

1. Excellent EMS performance: There are high-power chargers inside or around the DC pile, which will produce strong electromagnetic interference. The communication module itself needs to be able to effectively protect electromagnetic energy, and at the same time have an isolation function to reduce the mutual interference of each subsystem. The influence of crosstalk and common mode noise.

2. Reliable bus protection: When the charging pile is charging the car, the charging gun often needs to be connected or disconnected with the on-board charging port. At the same time, the car condition and environment of different cars are different. During this process, the charging gun is responsible for communicating with the BMS The CAN interface is very prone to ESD, transient voltage changes, electric spark interference, etc. If there is no adequate protection, the CAN interface is easily damaged.

3. Wide temperature adaptability: DC piles are generally installed outdoors in open areas. The outdoor temperature in the north and south of the country can reach -35℃45℃. At the same time, the high-power charger in the pile will radiate a lot of heat to the surrounding area when working. Considering the ambient temperature and the working status of the DC pile, the temperature change in the pile is expected to range from -35°C to 70°C, which is a severe test for the components inside the pile, and the communication module needs to be competent. .

4. Low failure rate: DC piles are responsible for the endurance of electric vehicles. At the same time, most of them are installed in highways, open fields and other environments. The direct loss and maintenance costs after failure are relatively high, and the requirements include isolation modules. The high reliability and low failure of each component ensure that the charging pile can serve customers lastingly and steadily.

Combined with the power supply application of each subsystem in the pile, the communication scheme of CAN and RS485/232 is as shown.

Figure 3 Power supply, CAN, RS485/232 isolation application solution on DC pile

ZLG's CTM series CAN isolation, RSM series RS485, RS232 isolation can easily meet the above requirements, high common mode rejection performance, modular design, help users quickly realize functions, while meeting the complex electromagnetic and temperature environment of DC piles. For example, CTM1051KT, which integrates a new generation technology of isolation DC-DC, the isolation voltage of the entire module is as high as 3500VDC, and the allowable working temperature range supports -40105℃.

Figure 4 RSM isolation CAN module

Figure 5 Isolated RS485 transceiver module

3. CAN port expansion solution on DC pile

In applications that require more CAN interfaces such as multiple charging, the CAN interface of the main control system may not be enough. At this time, the CAN application needs to be covered by peripherals, slave MCUs, etc. In this regard, the CSM100L series embedded UART to CAN module can provide an ideal solution. CSM100L has 2500VDC electrical isolation between UART and CAN, small volume modular design, CAN port conforms to ISO11898 standard, supports 5K1Mbps rate, can communicate with CAN device by operating UART, as shown in Figure 6 Embedded UART to CAN Shown.

Figure 6 Embedded UART to CAN

The design of the internal communication interface of the DC pile mainly considers anti-electromagnetic interference, wide temperature range, and long-time working reliability. Performance and quality are the most important considerations. It is recommended to use an integrated interface isolation module, and then match it with a reasonable The power isolation scheme effectively helps users design highly reliable DC pile products.

Figure 7 Industrial-grade isolated AC-DC power supply