As the core controller of the power battery system, the hardware main board of the battery energy management system mainly realizes the BMS strategy operation and execution functions, including information collection of total voltage / total current, real-time SOC estimation, fault diagnosis and storage, real-time control of the main relay, etc.
- System framework and overview
The hardware circuit block diagram of the designed motherboard system is shown in Figure 1, including power supply circuit, digital / analog input, high / low-end drive output, PWM input / output, can communication, etc.
The designed microprocessor adopts Infineon’s tricore32bit series tc1728, the main frequency is 133MHz, and the storage space is 1.5MB flash; Abundant peripheral IO resources can meet the design requirements.
1.1. working voltage
The working voltage range of the main board is 6 ~ 16V, and the static current of the main board shall not exceed 1mA.
1.2. Self programming and diagnosis ability
The motherboard can support self programming in the offline stage through UDS protocol. The mainboard is required to have hardware diagnosis functions, such as detecting the open circuit and open circuit status of the output IO port (including short circuit to ground and short circuit to power), and turning off the output function in time according to the fault status. The requirements for shutdown time are as follows: high voltage relay drives IO, acquisition board / high voltage board enable signal, and the response time after fault detection is 10ms; The rest output IO, and the response time after fault detection is 100ms.
1.3. Electrical interface and can communication interface
1.3.1 power interface
The power interface block diagram is shown in Figure 3, and the pin definition is shown in Table 4.
The designed maximum withstand voltage of the power supply is 65V and the maximum current is 5A; The designed maximum current resistance of the power supply ground is 25A, and the offset voltage to the ground shall not exceed ± 0.5V.
- Digital input and analog input
The high-level interlocking detection is designed to be effective at high level. It is required to pull down 1.2k Ω resistance to the ground, and the filtering time constant shall not exceed 1ms. The emergency diagnosis line is designed to be effective at high level. It is required to pull down 1.2k Ω resistance to the ground, and the filtering time constant shall not exceed 1ms. The fast charging wake-up line is designed to be effective at high level. It is required to pull down 3.3k Ω resistance to the ground, and the filtering time constant shall not exceed 1ms. The slow charging wake-up line is designed to be effective at high level. It is required to pull down 3.3k Ω resistance to the ground, and the filtering time constant shall not exceed 1ms.
Fast charge signal detection input port, the internal resistance is 4.64k Ω, pulled up to 5V, the connected effective signal is lower than 1V, and the non connected invalid signal is 5V; The temperature sensor adopts NTC, the typical value is 10K Ω, and the designed pull-up resistance is 3K Ω to 5V.
2.1. Digital output
Main board digital output pin pin, main positive relay control, main negative relay control and fast charging relay control. The design is equipped with small relay drive. The relay model is acb33401, the interface is active at low level, and the driving current does not exceed 300mA. Precharge relay control, slow charge relay control, design direct drive relay evr10-12s, the interface is low-level effective, and the drive current does not exceed 300mA. Accessory relay control, designed to directly drive relay acb33401, the interface is effective at low level, and the driving current does not exceed 300mA.
2.3. Communication interface, storage space and mechanical interface
Pin pin of the main board communication interface. The main board uses two-way can, in which hcan is used as the whole vehicle can to communicate with the whole vehicle controller; As an internal can, Ican communicates with acquisition slave board and high voltage board; Both channels of can adopt high-speed can, and the communication rate is 500kbit / s.
The flash storage space of the main board is 1.5MB, which is divided into application software area, calibration area, test area, production data retention area and boot loader area according to function. The external EEPROM storage space is 8KB, which is used to store vehicle data. The connector adopts Tyco series automotive connector, which is divided into a / B two parts, with a total of 121pins, as shown in Figure 6.