퍼지 이득 조정기를 이용한 초고주파 무전극 방전등 전원장치에 관한 연구
(A) Study of inverter power supply with fuzzy gain scheduler for microwave electrodeless lamp
퍼지이득조정기 초고주파 무전극방전등 전원장치;
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Faced with potentially serious energy crisis, engineers around the world have been working on high-efficiency energy convertors and ways to reduce and lighten their sizes, as well as on development of alternative energy. To keep up with this energy-saving trend, research and experiments have been made to apply invertor technology to home appliances such as air-conditioners, washing machines, refrigerators, and lighting systems in order to enhance efficiency and control performance. Conventional lighting technology, as represented by the incandescent electric lamp and fluorescent lamp, have limitation in efficiency improvement and applications. As a solution to this, developed countries have focused on developing new light-sources so as to seek drastic increase in efficiency and to preoccupy the market. Standing in the spotlight of lighting technology are electrodeless light-sources and semiconductor light-sources. Light-source technology employing microwave electrical discharge has many advantages since it does not use electrodes, and there have been a number of research effort to harness this technology. In particular, the invention of microwave electrodeless in the early 1990's has been hailed as a breakthrough in lighting technology, but its commercialization was delayed due to technical problems with the peripheral devices. The power supply employed for electrodeless sulfur lamps are based on iron core high voltage transformer. Since this method uses the power-frequency, thus necessitating big-size step up transformer and high voltage capacitor, the whole system can be exceedingly heavy, and there is a problem of power fluctuation. Nowadays, to solve the problems, inverter-based power supply is under research and development. In this study, it was applied to solve disadvantage of power supply when iron core high voltage transformer was used in power-frequency, so that shortening durability of a lamp was improved and controlled constant output power. The circuit was based on series resonant half bridge inverter which is the most efficient and excellent among resonant type inverters applying on microwave ovens, The circuit was devised by analyzing the working features of it. The controller contains self oscillator and used IR2155 half bridge driver in IR co. which can apply soft switching with various protection circuit such as high offset voltage and dead time controller in the early time. It needs to work with road of linear and magnetron of road of nonlinear structure in order to improve power factor and efficiency of inverter. In this study, pulse frequency modulation was made to control magnetron. Voltage controlled resistance was used to compensate linearity of output power of magnetron. Since durability of magnetron depends on initial departure, soft starting was made to remove emission moding not with initial departure. Illumination is changed when microwave electrodeless lamp does not control output power constantly. As a solution to this, a controller was designed by using micro controller so that control output power. Since magnetron has particular features of output power, when it is used in high output power or various output power, it shows too more nonlinear that it is difficult PID controller to compensate nonlinear output power. Therefore, fuzzy controller which has more advantages was applied on nonlinear system. Fuzzy controller does not need exact mathematic modelling of the object system and it is applied on system which has uncertainty of structure and gain of plant. It is stranger and freer in formation of control rules because it decides fuzzy rules and input-output parameter depending on designer's experience and knowledge. In this study, the existing microwave electrodeless lamp was designed and manufactured to analyze the features of output power and fuzzy gain scheduler controlling P controller was devised . Fuzzy membership function was quantized to be 31 considering speed and response of micro controller, inference used Mamdani's method of MAX-MIN and defuzzification used the most popular method, center of gravity. The proposed power system, through high frequency transformer with ferrite core which can ensure small size and lightness and high voltage capacitor under 5[nF] of small capacitor, made it possible to have various output power of 900∼1250[W] and lightening of about 1/3(2.2kg) in comparison with the existing power supply(7.6kg). The proposed power system compensation keeps output of the power source constant regardless of fluctuation in input power ±15[%] and could have a satisfactory results of luminous efficiency(97[lm/W]) and high power factor(96%).