The Research On Electric Contactless Power Supply System For Waterproof Electronic Balance

According to the requirements of power supply system for the development of waterproof electronic balance, the thesis discussed the research status, application and the development trends of some related key technologies, including electric contactless energy transmission technology, electricity storage technology, switching power technology, power electronic technology, and some other high and new technologies. Then, the thesis proposed a new electric contactless power supply method for waterproof electronic balance, which is based on contactless energy transmission technology. In this method, the side of power supply and other parts of the electronic balance are separated. The energy storage units are sealed inside of the electronic balance, while the power supply side, which is outside of the balance, provides power for the balance by utilizing electromagnetic inductive coupling. This new design overcomes the shortages of the traditional power supply methods by separation for the balance from level of the mechanical structure. Thanks to the new design, when the wire of supply system is dragged, the wire will split off from the balance immediately avoiding that the wire drags the balance as well as destroy the wire. Therefore, the new design can realize both complete waterproof and safety for the electronic balance.The thesis firstly analyzed the overall design of electric contactless power supply system after considering the energy transmission and feedback controlling respectively, then designed some key modules of the system in detail: (1)Firstly, this thesis designed the core part of the power supply system, separated transformer part, including the study of the characteristics of the separated transformer, magnetic circuit analysis, mutual inductance model, the equivalent circuit of the converter's secondary side and the circuit impedance, discussion of the compensation methods and its application field. After that, according to the AP design method on high frequency transformer, the parameter values for the separated transformers that are presented in the overall design are calculated, and some simulations and experiments to test some characteristics of the separated transformer are carried out as well. (2)Considering that the coupling of the separated transformer is not very good and the efficiency of energy transmission is low for 50Hz power frequency, this power supply system applied high frequency inverter technology. The thesis finished the comparison and selection of the circuit parameters such as topology, switching frequency, and duty cycle, then selected the appropriate devices for the inverter. The application of soft-switching technology is also studied and its advantage for reducing the power loss of MOSFET Power Transistor is shown by simulation. (3)In order to get accuracy voltage supplying for waterproof electronic balance and to monitor the status of power supply system, on basis of the analysis of the frequency composing, the thesis designed Feedback Circuit in detail. The power supply information including output voltage and current was fed back to the primary side using a wireless communication circuit. (4)The power supply side may be put on some other ferromagnetism object (named as Fault-Secondary-Side). In this case, Vortex Loss aggregation may cause the risk of danger. To avoid this risk, and to prevent the abnormal coupling when the two sides of the power supply system are not aligned, the thesis designed a Response Recognition Circuit. By using Emitting Diode and code technology, communications between the power supply side and the electronic balance side is enabled, which provide the information for the power supply side. Only after the power supply side receives the information and confirms its correction, can the electric energy transmission system start. Obviously, this Response Recognition Circuit increases the security of the system. (5)Finally, other modules of this new power supply system such as rectifier filter, and some key parameters in them are studied and designed.In a word, the new power supply system designed in the thesis, which is based on electric contactless energy transmission technology and some other high and new technologies, overcomes the shortages of the traditional power supply methods. It provides a new power supply method for the waterproof electronic balance. Furthermore, the design of Response Recognition Circuit and Feedback Circuit ensures the safety and stability of the system. Therefore, the waterproof electronic balance will get further improvement by the work of this thesis, and the work of this thesis may be a good foundation for deeper research and realization of this new power supply system.