Electric vehicles, due to the limited capacity of their energy storage devices, require extremely strict management of energy flow during operation. Precise energy management can extend vehicle range, reduce battery charging frequency, and thus save operating costs. The onboard energy management system needs to constantly monitor battery voltage, motor output power, and the power consumption of other devices. Simultaneously, the dynamic information of the electric vehicle's electronic control system must be real-time, with each subsystem needing to share common vehicle data in real time, such as motor speed, wheel rotation, and accelerator pedal position. However, different control units have different control cycles, data conversion speeds, and different control command priorities, thus requiring a data exchange network with a priority contention mode and extremely high communication speed. Furthermore, as a means of passenger transport, electric vehicles must possess extremely high operational stability, and the vehicle communication system must have strong fault tolerance and rapid processing capabilities. To address the numerous control and data exchange problems in modern vehicles, the German company Bosch developed a CAN (Controller Area Network) fieldbus communication structure, widely used in conventional gasoline-powered vehicles such as Mercedes-Benz, BMW, and Porsche. Simultaneously, the CAN bus is considered the optimal communication structure for electric vehicles. my country's "863 Program" explicitly states that newly submitted electric vehicle development projects must adopt the CAN bus communication mode. The CAN bus structure is an effective serial communication network supporting distributed or real-time control. Figure 1 shows a typical CAN bus structure for an electric vehicle, including multiple devices such as the main motor controller, battery management system, and human-machine interface display system. These subsystems communicate and transmit commands via CAN. Each node device can operate independently without the CAN bus, thus meeting the requirements of vehicle safety. Furthermore, the CAN bus will not experience system collapse due to the disconnection of any device. The three-phase inverter power supply for electric vehicles described in this article belongs to the on-board auxiliary inverter power supply shown in Figure 1. It's called an "auxiliary power supply" because its load consists of auxiliary AC motors in electric vehicles, such as the power steering pump, brake pump, coolant pump, and compressor in the air conditioning system. The requirements for this three-phase inverter are: under normal operating conditions, it should independently maintain the stable operation of the auxiliary motors and be able to adjust its operating status appropriately according to instructions from the host computer; in the event of a load failure (such as a motor short circuit), it should quickly shut down the output and safely shut down the power supply, while simultaneously reporting its own fault to the host computer and other nodes via the CAN bus, triggering relevant operations in various vehicle systems (for example, the HMI display system on the dashboard will immediately display a warning message, report the location of the vehicle fault, and prompt the driver to slow down; while the vehicle energy management system will issue a command to shut down the input of the auxiliary inverter and save the received error code and current operating parameters for maintenance personnel to diagnose the fault). Therefore, although a general-purpose frequency converter can be retrofitted to achieve the basic functions of a vehicle three-phase inverter, to create an intelligent node supporting various CAN bus functions, it is necessary to develop from the ground up, directly selecting a control chip that supports the CAN bus interface and integrating CAN communication functionality into the control program to meet the vehicle's communication requirements. 1. Introduction to the P8xC592 Chip In the design of auxiliary inverter power supplies for electric vehicles, the control circuit must not only support CAN bus communication, but also detect analog quantities such as load voltage and current, perform various logic judgments, and drive other chips to complete the three-phase inverter function. Therefore, simply selecting a standalone CAN controller is insufficient; the most convenient option is to use a controller with on-chip CAN functionality. The P8xC592 is an 8-bit microprocessor developed and manufactured by Philips. It primarily includes: an 80C51 central processing unit (CPU); two standard 16-bit timers/counters with four capture and three compare registers; a 10-bit A/D converter with eight analog inputs; two 8-bit pulse-width modulation outputs; 15 interrupt sources with two priority levels; five sets of 8-bit I/O ports and one 8-bit input port shared with the A/D converter's analog inputs; a CAN controller for DMA data transfer with internal RAM; a 1 Mbps CAN controller with bus fault management; and a full-duplex UART compatible with the standard 80C51. The P8xC592 has 68 pins, including six 8-bit I/O ports (P0-P3 are identical to the 80C51, but P1 can be used for special functions, including four capture inputs, an external counter input, an external counter reset input, and the CTX0 and CTX1 outputs for the CAN interface. The parallel I/O port P4 functions the same as P1, P2, and P3. Port P5 is a parallel input port without output functionality, primarily used as the analog input terminal for the A/D converter. The P8xC592 contains a CAN controller, including all the hardware necessary for high-performance serial network communication, enabling smooth communication flow through a CAN protocol local area network. To avoid confusion, the CAN controller added to the chip is presented to the CPU as a memory-mapped peripheral device capable of independent operation; the P8xC592 can be simply considered as an integration of two independent operating devices. If the CAN controller functionality is disabled, the chip can be used simply as a general-purpose 8-bit microcontroller with analog A/D conversion. Enabling the CAN controller functionality is mainly achieved through four special function registers (SPRs). The CPU controls and accesses the CAN controller through these registers, as shown in Figure 2. The four special function registers are: (1) Address register (CANADR), through which the CPU reads/writes the acceptance code register of the CAN controller; (2) Data register (CANDAT), which corresponds to the internal register of the CAN controller pointed to by CANADR; (3) Control register (CANCON), which has two functions: reading CANCON means accessing the interrupt register of the CAN controller, and writing CANCON means accessing the command register; (4) Status register (CANSTA), which has two functions: reading CANSTA means accessing the status register of the CAN controller, and writing CANSTA means providing the address of the internal data memory RAM of the subsequent DMA transfer device. In addition, the DMA logic allows high-speed data exchange between the CAN controller and the CPU in the main RAM of the chip. During the chip initialization phase, the CPU completes the functional initialization of the CAN controller by writing content to CANCON and CANSTA. In the actual communication process, the CPU uses the four registers to enable the CAN controller to receive and send data information. 2 Hardware Composition of Inverter Power Supply System The auxiliary three-phase inverter power supply for electric vehicles can be divided into three parts in terms of structure: (1) DC/DC multi-channel power supply - automatically adapts to the wide range of voltage fluctuations at the DC input terminal, providing isolated and stable low-voltage power supplies for other circuits in the system; (2) Main control board - detects the voltage and current of each output, intelligently adjusts the output of the inverter circuit according to the operating conditions, and participates in the vehicle data communication through the CAN bus; (3) Main power inverter circuit - composed of highly integrated three-phase inverter modules (IPM), which completes the inverter function of the main circuit. The basic structure diagram of the system is shown in Figure 3, in which the DC/DC multi-channel power supply that supplies power to each device in the system is not marked. The DC/DC multi-channel power supply adopts the standard design of a switching power supply, and is equipped with a multi-tap high-frequency transformer with different transformations to output 5V, 12V, 20V and other isolated DC power. At the same time, considering that the voltage fluctuation range of the electric vehicle battery pack is relatively large (400V when fully charged, which may drop to 280V during use), an appropriate circuit structure was selected in the design to achieve better input voltage adaptability. The control board is the core of the entire system, employing a P80C592 microcontroller (without on-chip ROM), an SA8282 dedicated pulse width modulation chip, an 82C250 CAN bus transceiver, and main circuit voltage and current data acquisition modules. The control board provides six PWM signals to the three-phase inverter module (IPM) via the SA8282 dedicated chip. Developed and manufactured by MITEL, the SA8282 chip is characterized by its simple control, high frequency accuracy, and high operational reliability. It supports the standard 8-bit MOTEL multiplexed data bus, facilitating data exchange with the microcontroller. The microcontroller only needs to assign values ​​to the chip's five internal data registers to complete the initialization and real-time control of the PWM waveform output. The SA8282 chip is a standard 28-pin dual in-line package. Its RPHT, RPHB, YPHT, YPHB, BPHT, and BPHB pins output three independently controllable TTL drive signals, which can drive the six IGBTs on a three-phase inverter bridge. After connecting the SA8282 chip to the IPM, the P80C592 only needs to initialize it during startup. Once the three-phase output reaches the predetermined values, the SA8282 can independently drive the IPM module. The P80C592 only needs to control the SA8282 when adjusting the PWM output. Simultaneously, the SA8282 chip's SET TRIP pin can respond to fault signals from the IPM, quickly shutting down all PWM waveform outputs to provide rapid protection for the inverter circuit. It also notifies the P80C592 microcontroller via the TRIP status output, ensuring system safety. Data acquisition modules distributed at the DC input and three-phase output terminals of the main circuit can collect voltage and current data from each circuit. After A/D conversion by the P80C592, the data is stored in the data memory, allowing the CPU to determine whether the system input/output is normal and perform corresponding operations. The 82C250 CAN bus transceiver is the interface between the CAN controller and the physical bus. Originally designed for high-speed automotive communication, it incorporates many features tailored to vehicle applications. Its characteristics include: effectively reducing the impact of instantaneous interference in the automotive environment on the signal; bus protection capability; protection against short circuits between the battery and ground; and support for low-current standby mode. Therefore, it is very suitable for the needs of electric vehicle auxiliary inverters. Connecting the 82C250 to the CAN interface input and output terminals of the P80C592 forms the external communication interface for the auxiliary inverter, as shown in Figure 4. 3. Inverter System Software Design The control software for the auxiliary three-phase inverter is written in 8051 assembly language. In addition to fulfilling its control functions, the program strives for rationality and simplification to meet the system stability and reliability requirements of electric vehicles. The control flow is shown in Figure 5. After the system powers on, the P80C952 microcontroller first initializes the SA8282 chip's initialization register, and then executes a soft-start program based on the characteristics of the load motor. When the three-phase output voltage reaches the predetermined value, the three-phase inverter enters a stable operating state. Subsequently, the control program will cyclically monitor the voltage and current of each line, modifying the SA8282 control register parameters and adjusting the PWM output accordingly to change the three-phase output. For example, after the electric vehicle has been running for a period of time, the battery pack voltage may drop, causing the inverter's three-phase output voltage to fall below the set value. Upon detecting this, the P80C592 will increase the voltage output amplitude through the SA8282 to ensure stable power output. Simultaneously, the control program will periodically check the control parameters in the data memory. If the vehicle control system modifies the inverter's operating parameters via CAN communication, the P80C592 will adjust the output according to the new parameters. The control program includes three interrupt routines: a data acquisition routine, a CAN bus communication routine, and a fault handling routine. The data acquisition program is triggered periodically by the chip's internal counter to acquire data from the input and output lines of the inverter power supply. After analog-to-digital conversion, the data is stored in the data memory and then handed over to the CPU for operational status judgment. The CAN bus communication program contains several subroutines, and its basic program structure is shown in Figure 6. When the communication program is triggered, the P80C592's CAN controller issues command words to execute related tasks. When the host computer requests data, it transmits various operating parameters of the inverter power supply to the vehicle system; when the host computer queries the node status, it sends out data such as the current CAN node status; when the host computer requests to modify operating parameters, it stores the received data parameters in the data memory. The fault handling program has the highest interrupt priority, that is, the P80C592's external interrupt 0 (INT0) pin is connected to the SA8282 chip's TRIP pin. When a fault occurs in the inverter circuit, the IPM will send a fault signal to the SA8282 chip, which will immediately shut down the PWM output and send an interrupt signal to the P80C592, triggering the fault handling program. The fault handling procedure first shuts down the SA8282; then, it notifies the host computer of a fault via the CAN bus, writing the fault code and current system operating parameters into a message and sending it simultaneously; finally, it controls the microcontroller to shut down the entire system, achieving a safe shutdown. The introduction of the CAN communication network provides conditions for the global optimized control of electric vehicles, making each subsystem of the vehicle an intelligent node in the overall vehicle control. Using a P8xC592 microcontroller with an integrated CAN controller as the control core, combined with the SA8282 dedicated PWM waveform generator chip, the auxiliary three-phase inverter power supply for electric vehicles not only boasts high safety and stability but also fully participates in the vehicle's data exchange and control. For electric vehicles using different CAN bus protocols, only appropriate modifications to the CAN communication-related code segments in the control program are needed to successfully integrate it into the vehicle system, making the inverter power supply more versatile.