Abstract: Based on current switching power supply control technology, this paper presents two digital switching power supplies: one based on microcontroller control and the other on DSP control. The advantages, disadvantages, and application scenarios of each are analyzed and compared. Keywords: Switching power supply; Analog control; Digital control; DSP 0 Introduction Switching power supplies are renowned for their high efficiency and energy saving. Traditional switching power supplies employ analog control technology, using comparators, error amplifiers, and analog modulators to adjust the output voltage. Analog control methods are only suitable for switching power supplies with high frequency, low power consumption, and limited functionality. They also suffer from drawbacks such as complex control circuits, numerous components, and difficulty in modification once the control circuit is established, hindering the integration and miniaturization of switching power supplies. Digital control technology for switching power supplies can effectively address these issues. This paper introduces digital control technology for switching power supplies and presents two models: one based on microcontroller control and the other based on DSP control. The advantages, disadvantages, and application scenarios of both are analyzed and compared, as described below. 1. Comparison of Analog and Digital Control of Switching Power Supplies 1.1 Types and Characteristics of Analog Control in Switching Power Supplies Analog control methods for switching power supplies have been used for decades, resulting in a series of control modes, broadly categorized into three types: Pulse Width Modulation (PWM), Pulse Frequency Modulation (PFM), and Combined Modulation. Figure 1 shows a Pulse Width Modulation (PWM) switching power supply. The AC 220V input voltage is rectified and filtered to become a DC voltage U. This is then chopped by the power switch VT and stepped down by the high-frequency transformer T to obtain a high-frequency rectangular wave voltage. Finally, the required DC output voltage U0 is obtained through the output rectifier filters VD and C2. A closed-loop regulation system is constructed using an error amplifier and a PWM comparator. This analog control circuit requires a large amount of space due to the numerous components used. The values ​​of these components themselves change with usage time, temperature, and other environmental conditions, negatively impacting system stability and response capability, and hindering the testing and maintenance of analog systems. Furthermore, the control response characteristics of analog control are determined by the values ​​of discrete components, thus failing to provide optimal control response for all power supply values ​​or load points. 1.2 Characteristics and Applications of Digital Control of Switching Power Supply The so-called digital control of power supply, also known as "processor inside the loop", refers to the controller being able to execute all system control algorithms in the digital domain. It must compare two digital strings to generate pulse widths to drive the power switch, instead of using a traditional analog PWM comparator. It converts all analog system parameters into digital signals, calculates the control response using these data in the digital domain, and then transmits the newly generated control information to the system. The digital control power supply system has the following characteristics: (1) It is an intelligent switching power supply system with a digital signal processor (DSP) or microcontroller as the core and digital power driver and PWM controller as the control objects. (2) It adopts "integrated digital power supply" technology, realizing the optimized combination of analog and digital components in the switching power supply. (3) It has a high degree of integration, realizing the monolithic integration of the power supply system, integrating a large number of discrete components into one chip or a group of chips. (4) It can give full play to the advantages of digital signal processors and microcontrollers, enabling the designed digital power supply to achieve high technical indicators. This technology can be used in applications with constant load time, enabling the power supply to operate at high frequencies, such as power factor correction, uninterruptible power supplies, multi-cell battery power conversion, and motor control; it can also be used in other applications such as the PMU of mobile phones and PDAs employing several configurable PWM cores and control, diagnostic, and interface circuits. Sub-circuits or peripherals in the runtime control circuit can provide the most suitable operating voltage for its current state to save energy. Digital power control makes the regulator more sensitive. 2. Switching Power Supply Schemes Based on Digital Control Technology Combining current digital control technology and popular power management models, we propose the following two schemes. 2.1 Switching Power Supply Based on Microcontroller Control With the rapid development of electronic technology and the further improvement of VLSI design, microcontroller technology has also developed rapidly and has been widely used in intelligent instruments, industrial detection and control, power electronics, automotive electronics, mechatronics, and other fields, achieving great results. Using a microcontroller as the control core, the design method is easy to master, and the requirements for the microcontroller are not high, resulting in relatively low cost. This scheme uses a microcontroller to sample data via an external A/D converter chip. After sampling, the obtained data is processed and adjusted, and the result is then transmitted to the PWM chip via D/A conversion, realizing indirect control of the switching power supply by the microcontroller. Its principle structure is shown in Figure 2. The microcontroller used is an MCS51; the A/D converter uses a TLC2543 chip, which uses a serial interface. Compared to parallel interfaces, this method is simpler, easier to expand, and smaller in size. The TLC2543 uses a typical SPI interface, and its hardware circuit is very simple when connected to the MCS51 microcontroller. However, since the MCS51 does not have a standard SPI interface, the TLC2543 can only be operated by simulating SPI operation in the program, making the program more complex. The D/A converter uses a TLC5615 chip connected to the MCS51, also using a serial interface. The watchdog timer provides a power-on reset signal to the microcontroller. When the program malfunctions or the voltage is abnormal, the internal watchdog circuit is activated, forcing the microcontroller to reset and restart the program. It has a 512-byte EPROM memory unit to store various important data in case of data loss after an AC power cycle. An external serial port is provided, connecting to RS-485 or RS-232 via level conversion, enabling signal transmission between the switching power supply and the host computer. An LCD and keyboard interface circuit enables human-machine interaction. Although this microcontroller-based digital power supply method has a relatively complex control circuit and some delay, which affects the dynamic performance and voltage regulation accuracy of the power supply, it is suitable for applications where high voltage regulation accuracy and dynamic performance requirements are not critical because the microcontroller requirements are not high, the cost is low, and the design method is easy to master. 2.2 Switching Power Supply Based on Digital Signal Processing Control Utilizing high-performance DSP digital chips for direct power supply control simplifies control circuit design. Furthermore, these chips offer high sampling speeds (the TMS320LF2407's internal 10-bit A/D converter completes one A/D conversion in just 500ns) and processing speeds, enabling the rapid and efficient implementation of various complex control algorithms. The principle structure of a DSP-controlled switching power supply is shown in Figure 3. The DSP uses the popular TMS320LF2407, primarily for digital PID calculations. The Complex Programmable Logic Device (CPLD) generates a digital PWM waveform to control the main power converter based on the DSP's calculations, thus avoiding the double-pulse and half-frequency phenomena found in analog PWM controllers and achieving complete digitalization of PWM control. An AID conversion circuit is used for acquiring data such as voltage, current, and temperature. The chip used can be either a TLC5540 or a TLC2543. The voltage and other signals acquired through this AID conversion circuit are fed into the DSP via the lower eight bits of the data bus and compared with a standard sine wave signal. When the output voltage amplitude is detected to be higher than the standard sine wave signal, the duty cycle is reduced proportionally, thereby adjusting the output sine wave and amplitude of the switching power supply. The DSP can also be expanded with an LCD and keyboard for human-machine interaction, and data communication via RS-485 or RS-232 serial ports. Although the DSP chip structure of this digital switching power supply is complex and the cost is relatively high, and the DSP control technology is relatively difficult to master, the chip has a high sampling speed and operation speed, which can quickly and effectively implement various complex control algorithms, realize effective control of the power supply, and has high dynamic performance and voltage regulation accuracy. Therefore, this method will play an important role in the digital control technology of switching power supplies in the future. 3 Conclusion Switching power supplies adopt fully digital control technology, which can effectively reduce the size of the power supply, reduce the cost, and greatly improve the reliability of the equipment and the adaptability to users. It is a trend in the future development of switching power supplies. At present, it has been well applied in the field of communication. The two schemes of switching power supply based on digital control technology given in this paper are suitable for different environments. We can choose different schemes according to factors such as sampling speed, operation speed and control algorithm complexity. References [1] Qiu Wei, Hou Zhenyi, Design of a smart high frequency switching power supply monitoring module [J]. Power World, 2006, 3: 15-17 [2] Ka Leung, Alfano, D. Design and Implementation of a Practical Digital PWM Controller [C], 2006. APEC6 [3] Huang Jiqing, Huang Xiaojun. High-frequency switching power supply for communication [M]. Beijing: Machinery Industry Press. 2004 [4] Zhang Song, et al. Soft switching power supply control system based on DSP [J]. Information and Electronic Engineering. 2003, 1(2): 50-53 [5] Fan Linan, Xie Zidian. 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