| Modern ultra-precise equipment need high-precision temperature circulating cooling water to reduce the influence of temperature error. TEC(Thermoelectric Cooler) can provide excellent cooling performance for the circulating constant-temperature cooling water system. Switching power supply is the best choice to meet high-current and high-power requirements for driving TEC. However, the working principle of switching power supply causes its output coupled to a lot of noise and harmonics, which will affect the accuracy of semiconductor refrigeration badly, thereby affecting the circulating cooling water temperature control accuracy. Therefore, research on the key technologies of switching power supply to improve the switching power supply output performance is essential.According to the application background and problems above, this paper will analyze the principle of switching power supply, and do specific research on key technologies for the output characteristics of the switching power supply, and complete the overall design and prototype debugging.The main points are as follows:Firstly, to meet high-power switching power supply design requirements, all aspects are investigated and explained,like the circuit structure, materials, devices, work methods, After some comparation and analysis, full bridge converter is chosen as the basic structure of the power supply in the design;Secondly, design specifications of driving power is formulated by the operating characteristics of semiconductor refrigeration, combined with the actual needs of high-precision recirculating cooling water systems, and the full-bridge inverter architecture is completed after module is designed: the pulse modulation mode for driving power switch, the driving circuit structure, the circuit topology for output rectifier, the control mode of circuit regulator feedback loop. All above forms a detailed schematic circuit of switching power;Thirdly, with the working process of switching power supply this paper will find the oscillation source of output ripple- the power switch driving, power switching process and the rectifier diode turning off progress, and explore the mechanism how the oscillation circuit is formed. And the relevant devices and circuits parameter will be extracted. Using resonance analysis, critical parameters of components is to be obtained; theoretical analysis is performed about the size parameter selection methods of the transformer core in the switching power supply, and a transformer with low leakage inductance is designed to meet the task’s needs; at the same time, the output filter structure for the output circuit is selected to meet the requirements of the subject.Fourthly, the control loop of regulator control is extracted according to control theory and a small signal model of the switching power supply is used to calculate the transfer function of each module and the overall control circuit, characteristics of the open loop transfer function of the power supply voltage control system are analysied according to the frequency domain analysis. A three-pole-double-zero compensation network is designed to compensate double pole brought in by inductor and capacitor of large value in the output filter. To enhance the safety and stability requirements of the system further, a soft-start circuit and two-stage overcurrent protection circuit for the power system are added, and a MCU is used to complete the auxiliary aspects of the work detecting circuit and numerical control circuit.Finally, simulation and experimental tests will be done about the key design technology of switching power supply, and the desired effect is actually obtained; engineering prototype is assembled, to test the main functions of the driving power like control linearity, ripple and noise, and frequency response. The results show theoutput ripple can decline to 88 m V from 190 m V with 11.290 V output. What’s more, the results indicate that the prototype can work with control linearity 0.33%, adjusting bandwith 1.2k Hz and up to 933 W power supply, which proves correctness and rationality involved in the design of switching power provides a basis for further research... |
PDF Full Text Request