Research On Switching Power Supply For Ship Corrorision

Ship corrosion can cause serious ocean pollution, which affects ship’s performance and brings high maintenance costs. Impressed current cathodic protection is effective in preventing corrosion and also of low cost. With the rapid development of modern power electronics and the widely use of microprocessor technology in the field of ship power, intelligent anti-corrosive ship power supply has become a hot area of research.The thesis introduces the theoretical basis and key technology of switching power supply. Then, the thesis researches on topologies and control methods of AC / DC and CV / CC. Finally, the thesis designs the system of numerically controlling constant current switching power supply for the ship. System hardware is divided into AC/DC, CV/CC, communication monitoring module, while the system software includes controlling programs of host computer and slave computer.In Hardware circuit, AC / DC module convert 220V(AC) to 24V(DC) by using a single-ended flyback circuit and PWM pulse width modulation method. AC / DC includes an input rectifier circuit, RCD clamp circuit, EMI filter circuit, the transformer, the output filter circuit, a control circuit, a voltage feedback circuit and overvoltage, overcurrent, overtemperature protection circuit. The CV/CC module converts the constant voltage to constant current output which maximum value is 2000 m A. The CV/CC module uses the operational amplifier to constitute the follower to reduce the front stage disturbance, and the 1.25 V high precision voltage source is used as the reference power source of the programmable resistance network. C8051F340 regulate the output current of the constant current module through I2 C to control programmable resistance network. Communication monitoring module designs conversion circuit to support the communication between the upper and lower computer.In control software, the slave computer program is based on the C language in the Keil compiler environment for debugging. The Program adopts a modular design, including system initialization module, I2 C communication module and serial port UART0 monitoring module, which are all used by the software to set the output current and the feedback current and voltage. Host computer program is based on C++ language in QT compiling environment for debugging, and the design includes man-machine interface, serial port setting, serial port communication module. Host computer program also use these function modules to set the slave computer current and read the next bit machine output current and voltage. In order to communicate effectively, the same communication protocol and data frame format are defined in the control program of the host computer and the slave computer to construct and resolve data frame.After completing design, the thesis uses Altium Designer 09 drawing schematic and PCB layout. After welding components and burning programs, the thesis also sets up a test platform for debugging and testing the performances of system. Debug AC/DC module, CV/CC module and communication monitoring module are independently tested to ensure each module work normally. Finally, the whole system is tested, including the output ripple, control precision, load adjustment rate, power adjustment. According to the analysis of test data and waveform, the system basically achieves the default function and the performance of the indicators. The test shows that the system has friendly man-machine interface, easy operation, fast response and strong stability. It has a certain application prospect in the field of ship power supply.