| The digital switching power supply is a hot research direction of DC regulated power supply, compared with the traditional analog switching power supply which has the advantages of low cost, portability, scalability, can realize the complex algorithms and other advantages, in recent years, the digital switching power supply has been rapid development. In this paper, taking the STM32F103 microcontroller as the core, designed for DC power supply system for nuclear magnetic resonance gradient power amplifier, digital designed phase-shifting PWM drive signal, feedback control and protection measures.The application of soft-switching technology in switching power supply design, can improve the efficiency of power system and reduce the interference of the switching tube switch, is the inevitable trend of the switching power supply research. Based on the ZVS soft-switching as the design goal, realization of full bridge zero voltage turn-on and turn off of the IGBT, the realization of the principle of ZVS soft-switching are analyzed and discussed in depth, and achieves the design goal of soft-switching in the design of power supply.The main research contents of this paper are as follows:1. In reference to the design of DC regulated power supply at home and abroad, the design of magnetic resonance gradient power amplifier DC regulated power supply, including the comparison of the analysis of inverter topology, the hard switching and soft-switching, ZVS structure and ZVZCS structure, the converter control strategy, digital control and analog control etc.. This paper selected the digital control phase shifting full bridge soft-switching power supply system as the research project.2. The working principle of digital control phase shifting full bridge soft-switching power supply system are analyzed in detail, and discuss the hardware circuit of power supply system of the device design and selection of the parameters, including the design of primary rectifier and filter circuit, main control board, a full bridge inverter circuit, high-frequency transformer, secondary rectifier and filter circuit, feedback control circuit, the protection circuit module, etc.. Completed the software design of the power supply system, including the programming and testing of the main program module, phase shifted PWM module, feedback signal sampling module and PID control module. In order to increase the reliability of the system, this paper discusses the anti-jamming design of system from two aspects of hardware and software.3. Using the switching power supply simulation software Saber to simulate and analysis the soft-switching design and stability of the power supply system. The power system time domain simulation analysis, confirmed the full bridge inverter lead and lag bridge arm to achieve soft-switching. By Saber software loop scanner complete power system frequency domain simulation analysis, acquire the Bode plot of the system, and then verify the stability of the system.4. The production of a switching power supply prototype was completed, the waveform analysis showed that: the output power, source effect, load effect, ripple voltage and other indicators of digital control phase shifting full bridge soft-switching power supply system in testing process to achieve the design goal. The system can load MRI gradient amplifier as realization of the leading leg and lagging leg of zero voltage switching. |
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