Since the 1990s, the national telecommunications department has gradually accelerated the requirements for networked management of communication equipment, requiring all equipment that make up the communication network to have intelligent and communication capabilities, and power supply equipment is no exception [1]. The application of computer technology has made communication power supply a high-tech product that integrates computing technology, control technology and communication technology, greatly improving the performance and function of the product, thereby realizing automatic testing, automatic diagnosis and automatic control of the system, and realizing remote signaling, remote measurement and remote control of the power supply system [2]. Therefore, high-frequency switching power supply has also entered the stage of intelligent control. This paper designs and implements a monitoring module of intelligent high-frequency switching power supply. 1. Principle and characteristics of high-frequency switching power supply Intelligent high-frequency switching power supply has the characteristics of highly flexible combination and autonomous monitoring. Especially in the field of communication, it is widely used because of its small size, low noise, convenient maintenance and ability to be incorporated into the computer monitoring system of the communication system. The circuit principle block diagram of high-frequency switching power supply is shown in Figure 1. It is mainly composed of AC power distribution, rectifier module, DC power distribution module, charging module, main monitoring module and related circuits. Among them, the charging module and the main monitoring module have built-in microprocessors. This high-frequency switching power supply converts 220V (or 380V) AC power into stable and reliable 48V or 24V DC power to supply power to loads (such as program-controlled exchanges, optical transceivers, etc.) and to float charge or equalize charge the battery pack. When the AC power input is interrupted, the battery pack supplies power to the load through this system to ensure continuous and uninterrupted power supply. When the AC power returns to normal, the system automatically performs equalization charging on the battery pack and rapidly replenishes the battery's energy after a significant discharge. Figure 1. Block Diagram of High-Frequency Switching Power Supply . This power supply has the following characteristics: ● Wide AC input voltage adaptability: three-phase 380±30% (266～494V), single-phase 220±30% (154～286V); ● Adopts active power factor correction technology, achieving a power factor ≥0.99 and high overall efficiency; ● Employs PWM edge resonance technology, which reduces power loss of switching devices during high-frequency switching, improving overall efficiency to over 90%, and also reduces electromagnetic interference, allowing the power supply system to be installed in a programmable control room; ● The system uses microcomputer control, Chinese character display, and keyboard operation, making it easy to learn and use, greatly facilitating users. 2. Composition of the Intelligent High-Frequency Switching Power Supply Main Monitoring Module Because this power supply system requires extremely high reliability, effective monitoring and control of its operating conditions is crucial. The main monitoring module, as an independent module, can monitor the operating status of each unit in the entire power supply system, and has the function of collecting, displaying, and setting system operating parameters. It can also communicate with an external computer (usually a PC) to form a local or remote centralized monitoring system. When communicating with an external computer, the main monitoring module is called the lower computer and the external computer is called the upper computer. Therefore, the main monitoring module must also be able to continuously receive commands from the upper computer and operate the power system according to the commands or send the operating status and parameters of each unit of the power system back to the upper computer, control the input and output of each module, complete the human-machine dialogue, and realize communication with the external computer or remote host. 2.1 Working principle and composition of the monitoring module Figure 2 is the block diagram of the main monitoring module [4]. As an independent module, the main monitoring module can monitor the working status of the entire power system, control the input and output of each module, and complete the human-machine dialogue. The module consists of an AT89C52 microcontroller, an AC/DC power distribution parameter acquisition unit, a display and operation unit, and a serial port communication unit. The monitoring module and the rectifier module exchange information through RS-485 serial communication, so that the hardware design of the monitoring module is not limited by the number of rectifier modules monitored, and the number of power modules in the system can be expanded arbitrarily. The system also uses serial communication with the host computer. The serial port is expanded using an 8250 chip. For local centralized monitoring, an RS-485 serial port can be used; for remote monitoring, an RS-232 serial port can be used. Communication is also achieved through a modem and telephone line. The system uses a large-screen LCD and keyboard for local human-machine interaction. The main monitoring module detects the DC bus voltage and current. When the voltage or current exceeds the upper limit setting, it commands the rectifier module to reduce the voltage and limit the current. Based on the operating status of each rectifier module, it determines the activation and deactivation of each module, thereby ensuring the entire power system operates in a stable state. In addition, the main monitoring system also detects fluctuations in the grid voltage, issues alarm signals, and records fault information. Figure 2 shows the block diagram of the monitoring system. The AC detection unit mainly consists of a three-phase AC voltage detection board and a three-phase display board. The three-phase AC voltage detection board is installed in the upper AC power distribution area inside the cabinet. Its function is to send the isolated AC mains signal to the controller, which then detects the AC mains parameters and determines whether the input AC power is "out of limit" or "phase missing." If "out of limit" or "phase missing" occurs, the controller issues an alarm. The transfer unit sends the frequency signal from the controller controlling the rectifier output voltage level to each rectifier, and sends the detected signals from each rectifier to the controller. These signals include: the frequency signal controlling the rectifier output voltage level, the voltage signal of the current sharing bus, the current signal of each rectifier, and the rectifier alarm signal. The DC detection unit mainly includes a battery current detection board and a battery protection board. It detects whether the load branch DC circuit breaker is open, whether the battery branch fuse is open, and detects the battery branch current and sends it to the controller. The controller detects, displays, and alarms the signals from the AC detection unit, transfer unit, and DC detection unit; and controls the rectifier's operating status. Status queries, system operations, and parameter settings are performed via the keyboard. 2.2 Main Functional Detection of the Controller: System AC power supply, battery status, rectifier status, battery current, main and branch current, and fault information; Control: System power on/off, equalization charge on/off, rectifier power on/off, battery test on/off; Parameter Setting: System parameter settings, number of rectifier cabinets; Battery Parameters: Equalization charge voltage, float charge voltage, overvoltage value, undervoltage value, charging current limit value, conversion current, etc.; Monitoring Parameters: Equipment number, communication interface, dialing method, telephone number, and fault reporting on/off, etc.; Communication: Realizes three-remote communication through the interface, and outputs system alarm signals to the system fault monitor through the fault interface. 3. Monitoring System Software Implementation 3.1 Implemented Functions This system adopts a centralized management and independent control mode. Each module's microcontroller has its own independent control program and communication program with the monitoring module. When an individual module fails, it will not affect the operation of the whole machine. The main monitoring module software adopts a modular structure design, and various functions are completed by corresponding interrupt subroutines. The monitoring module software mainly performs the following functions: (1) receiving data sent by each module; (2) sending control commands to each module; (3) human-machine interface. The main control microcontroller in the monitoring module is the master, and the microcontroller in the rectifier module is the slave. They use a 10-bit asynchronous communication format of N, 8, 1 with a baud rate of 4800B. Data sent from the slave to the master can only be sent after the master issues an allow command. That is, only the module selected by the address code has the right to send data to the monitoring module. 3.2 Main monitoring program The main monitoring software adopts a modular structure design, and all functions are completed by the corresponding interrupt subroutines. Figure 3 shows the flowchart of the main program. The initialization of the system includes the initialization of the MCU's internal control registers, the initialization of the register area and the data area, etc. Self-test includes RAM self-test and self-test of each sensor in the control system. After the self-test is passed, the interrupt and PTS are enabled, and the display initialization subroutine is called. The main menu of the display system can be selected by the keyboard, including the running parameter menu, status menu, fault record menu and parameter setting menu, etc. To ensure operational safety, the parameter setting menu is only accessible to authorized management and maintenance personnel and requires a password to operate. Figure 3 shows the main program. This monitoring system uses an 8×4 Chinese character display. Considering the large number of monitored parameters, which cannot all be displayed on one screen, a menu-driven operation method is adopted. Users select the menu information displayed on the screen and press the appropriate function key on the keyboard of the alarm module panel. The system's microprocessor reacts based on the information sent by the key press, realizing the corresponding function. Therefore, the keys include numeric keys and function keys. The program adopts a tree-like branching structure, as shown in Figure 4, the keyboard program flowchart. Figure 4 shows the keyboard program flowchart. The core part of the monitoring software is the serial port receive interrupt subroutine. This subroutine is responsible for serial communication, data reception and verification, format conversion, storage, and control. Due to the large amount of monitored data, each type of data must have a fixed format, and an error detection and retransmission mechanism is adopted to ensure data correctness. The data processing subroutine mainly completes A/D conversion, data comparison and judgment, digital signal output feedback control, and interrupt clearing. Figure 5 shows the flowchart of the serial port receive interrupt subroutine. Figure 5. Flowchart of Serial Port Receive Interrupt Subroutine 4. System Anti-interference Measures The performance of the monitoring module directly affects the operation of the entire switching power supply. If the anti-interference measures are not fully considered, interference entering the monitoring module can cause false measurements and false alarms, leading to the paralysis of the entire system. This system adopts a combination of hardware and software anti-interference measures. 4.1 Hardware Anti-interference Measures To improve the input impedance of analog quantities and reduce losses, a voltage follower is added before A/D conversion. The detected signal voltage is converted into current, and then a resistor is connected in parallel to restore it to a voltage signal. A high-precision 12-bit dual-slope A/D converter ICL7109 is used. To eliminate digital noise interference, a 10uF filter capacitor bank is added to the circuit. The entire system uses a 6N136 for isolation when completing serial communication with the computer. A watchdog circuit composed of MAX706 is used to improve the anti-interference measures of the MCU. 4.2 Software anti-interference measures mainly employ digital filtering and digital zeroing techniques to eliminate deviations in switching circuits and A/D conversion circuits, smoothing signals and reducing interference. Standardized formats are used for various data types, and verification, error detection, and retransmission mechanisms are implemented to improve reliability. Extensive use of redundant instructions further enhances software execution reliability. 5. Conclusion The intelligent high-frequency switching power supply, when paired with a battery, forms an uninterruptible power supply system, which can be widely used in telecommunications, water conservancy and hydropower, public security, railways, computing centers, and other locations requiring high-power DC power. The switching power supply using the monitoring module described in this paper, through operational testing, can achieve functions such as remote monitoring, remote control, and remote telemetry, is easy to maintain, highly reliable, operates normally, and all indicators meet the requirements. References [1] Tian Bing, Wang Zhengjun, Yang Wanquan, et al. Intelligent communication power supply monitoring system [J]. Communication Technology, 2003, (10): 65-66. [2] Lu Jianfeng, Han Lei, Yang Yongxin, et al. A DC power supply monitoring system based on AVR microcontroller [J]. 2004, 25 (4). [3] Zhu Junxing, Hua Wei. Application of COP8 microcontroller in switching power supply monitoring system [J]. 2004, 30 (1): 30-31. [4] He Limin. Application system design of [M] series microcontroller Beijing: Beijing University of Aeronautics and Astronautics Press, 1998. [5] Xu Xiaojie, Hou Zhenyi. Anti-interference design in communication power supply monitoring system [J]. Communication Power Supply Technology, 2002, 6: 12-14