0 Introduction With the rapid development of power electronics technology, switching power supplies have received increasing attention, especially in the fields of communication and power. In recent years, to improve the convenience and ease of use of power supplies, modularization and integration have become important research topics. Modular design allows different systems to select the number of parallel modules according to their own capacity, while ensuring redundancy, facilitating maintenance and replacement, and achieving a "building block" structure. However, for this new system structure, the old power supply monitoring and maintenance methods can no longer meet management requirements. Therefore, it is necessary to adopt a "building block" multi-monitoring system. Currently, some literature introduces this power supply monitoring method; however, the monitoring modules do not consider factors such as cost and size, which must be considered when integrating the main power supply with other peripheral circuits. To facilitate the integration of the monitoring module with the main power module, achieve miniaturization, and ensure reliability, it is necessary to design a monitoring module that is simple in structure, powerful in function, has strong anti-interference ability, low in cost, and is easy to mass-produce. 1. Monitoring System Hardware Design 1.1 Monitoring System Hardware Structure To simplify the circuitry of the monitoring modules, a bus-based design is adopted. This involves placing a large amount of data processing in system-level monitoring, while module-level monitoring is responsible for data acquisition (including output voltage and current), providing various protection functions, and performing status monitoring (including overheating, overcurrent, overvoltage, and power grid faults). The host computer manages each power module via a communication bus. The monitoring system block diagram is shown in Figure 1. 1.2 Monitoring Module Hardware Function Design The functions to be implemented by a single monitoring module include monitoring, control, and communication. Monitoring refers to dynamically acquiring the module's output current, determining the module's operating status, and transmitting the data and relevant status information to the host computer. Control refers to receiving voltage adjustment signals from the host computer to adjust the module's output voltage, or adjusting the output voltage via a potentiometer on the panel, while also implementing fault protection. Communication refers to the module being equipped with an RS485 interface to communicate with the host computer. The functional block diagram of the monitoring module is shown in Figure 2. The main power circuit uses a phase-shifted full-bridge design to achieve soft switching and improve efficiency. An auxiliary network is added to expand the load range of the soft switching; the specific circuitry and operation are not discussed in this paper. The dashed box shows the entire monitoring module. The module's inputs include the mains input voltage, heatsink temperature, power output voltage, and output current. The module's outputs include a voltage regulation signal, a power-off signal, and a power operation status signal sent to the host computer. The microprocessor is the core device of the monitoring system. This system uses a PHILIPS P87LPC768 microcontroller, which integrates a PWM port, UART, and WATCHDOG. This microprocessor is small (20 pins), low-power, and powerful. The PWM port can be used for D/A conversion. Since the output voltage adjustment is not a fast speed control system, only ordinary optocoupler isolation and a follow-up RC filter are needed to obtain the control signal for adjusting the output voltage. This fully utilizes the microcontroller's internal resources and reduces the need for external components susceptible to temperature and electromagnetic interference. Because the internal temperature of the power module varies significantly, ordinary analog signal isolation (such as using linear optocouplers) is greatly affected by temperature. Therefore, the output voltage and current are first sampled to obtain digital signals, which are then sent to the microcontroller for processing via optocoupler isolation. A serial A/D converter (such as the MAX1109) is used for current sampling, which saves limited microcontroller pin resources and reduces module size. Since the data read and write frequencies of the serial A/D converter can be relatively low, ordinary optocouplers can be used, reducing costs. The conversion clock can use the high-frequency clock inside the A/D converter without affecting conversion accuracy. The sampled output voltage and current values ​​can also be transmitted to the host computer via serial communication for monitoring and management of the entire system, as well as for display on the module's LCD. To save microcontroller resources, a serial transmission scheme can be used. This function is implemented using a serial/parallel converter (such as the 74LS164). The LCD can be a module, simplifying the circuit design and improving reliability. Furthermore, to save microcontroller resources, the LCD module can operate in 4-bit data mode. There are two ways to adjust the voltage of the monitoring module: one is manual adjustment via a knob, and the other is adjustment via software settings (only involved in system-level monitoring). Controlling the output voltage of the power supply module mainly involves controlling the duty cycle of the PWM waveform. In the first method, a circuit capable of generating an adjustable duty cycle PWM waveform must be designed (such as a multivibrator circuit with an adjustable duty cycle composed of a 555 timer). In the second method, the PWM waveform is generated using the PWM port of the PHILIPS P87LPC768 microcontroller, and the duty cycle is changed in the software. When the monitoring module communicates with the host computer, since it is a multi-level communication, addresses are necessary for mutual differentiation. Each module is address-encoded, and the module address setting is controlled by a DIP switch. The set address is read into the microcontroller for processing via a parallel-input-serial-output shift register. Communication uses the RS-485 protocol. The monitoring module designed using the above scheme is small in size, low in cost, and relatively complete in functionality. 2. Monitoring System Software Design The entire system software adopts a modular design, consisting of multiple subroutines, facilitating debugging and expansion. To improve the accuracy of sampled data and reduce errors, digital filtering technology is used in the program. The flowchart of the main program is shown in Figure 3. After initialization, it enters the main loop to detect the system status, determine whether there is overvoltage, power grid fault, overtemperature, or overcurrent, and sample the output current, converting it into a voltage signal for display and transmitting it to the host computer via the communication bus. Since the voltage and current displays of the module only serve a monitoring function and are not used for measurement, the refresh frequency does not need to be very high, basically not increasing the burden on the MCU. When detecting the system status, if a fault occurs, a delay is made before determining whether a fault has actually occurred. Once a fault is confirmed, the module output is turned off, and different LED indicators are used to display different faults. Among these, overtemperature faults and power grid faults are recoverable faults, so a certain waiting time is required. When the fault disappears, the module can restart; however, output overvoltage and overcurrent faults are unrecoverable faults, and the module should not be restarted. The host computer controls the slave computer primarily through a communication bus, employing a master-slave multi-machine communication method. The host computer initially operates in mode two, sending an address frame and then waiting for a response signal from the slave. Upon receiving the response, it switches to mode three and then sends commands. The called slave, upon receiving the host's address frame, if it matches its own address, switches from mode two to mode three, sends its own address as data, and then waits for commands. The data format is as follows: bit D8 being 1 indicates an address frame is being sent, and bit 08 being 0 indicates a data frame is being sent. Module address numbers range from 0 to 15, corresponding one-to-one with the module placement order. The communication baud rate is 2400bps. 3. Conclusion The monitoring system described in this paper is feature-rich, highly reliable, compact, and possesses strong anti-interference capabilities, minimal temperature sensitivity, and low cost. It can be applied in high-power-density power modules and has significant practical value, and is currently used in communication power supply products.