Research On Intrinsically Safe Active-clamp Flyback Converter Based On GaN

Due to the presence of a large amount of flammable and explosive gas in the working areas of coal mines and other underground operations,intrinsically safe electrical equipment is increasingly required to be used in hazardous gas environments.Therefore,intrinsically safe switch power supplies are also increasingly applied in such environments.This poses strict challenges to the safyty and reliability of intrinsically safe power supplies.At the same time,with the increase in monitoring equipment and sensors in coal mines,the requirements for the power and voltage level of intrinsically safe power supplies are also increasing.Therefore,it is of great significance to develop an intrinsically safe switch power supply that is safe,reliable,and capable of delivering high output power.Through investigation of existing intrinsically safe power supply products and related literature on the market,it was found that most of the intrinsically safe power supplies currently designed have low power and an output voltage of no more that 18 V,with a power of no more than 30 W.Due to the limitaion of spark discharge energy in underground coal mines,it will be much more difficult to further increase the output voltage level or output power.To address this issue,this thesis takes the intrinsically safe type switch power supply as the research object and uses GaN power devices to increase the switching frequency of intrinsically safe power supplies.In addition,the capacity of the energy storage element at the output of the converter is reduced within the allowable range of ripple to reduce the spark energy when a short circuit occurs at the output end.These measures can effectively improve the voltage level and output power of intrinsically safe power supplies.Therefore,this thesis designs two activeclamp flyback converters based on GaN power devices and Si MOSFET respectively,starting from improving the power and reducing the volume of intrinsically safe power supplies.Firstly,this thesis compares the self-characteristics of GaN power and Si MOSFET and concludes that the use of GaN power devices can increase the switching frequency of the converter.The type and protection methods of intrinsically safe power supplies are analyzed,and it is determined that the intrinsically safe power supply designed in this thesis adopts a one-time intrinsically safe and back-end current-limiting protection method.Secondly,the basic principle of active-clamp flyback topology is analyzed,and the basic working mode,energy transfer process and spark energy release during output short-circuiting of the active-clamp flyback converter are derived.According to the minimum ignition curve of the capacitance circuit in GB3836.4,the non-explosion evaluation critera of the output intrinsically safe performance of the active-clamp flyback topology are given.Subsequently,the power circuits and control circuits of the intrinsically safe active-clamp flyback converters based on GaN and Si MOSFETs were designed respectively,and a current limiting protection circuit was also designed.The intrinsically safe performance of the two designed converters was verified,and it was found that under the same design specifications,the converter based on GaN can achieve output intrinsically safe,while the converter based on Si MOSFET cannot not achieve output intrinsically safe.Simulation and prototype experiments shown that the main and auxiliary switches of the two converters can soft switching.Spark discharge experiments were conducted to obtain the spark discharge energy of the GaN-based converter.According to the nonexplosive evaluation criteria,it was found that the prototype designed based on GaN power devices met the requirements of output intrinsically safe,proving the correctness of its theoretical analysis and design.There are 59 figures,10 tables and 84 references in this thesis.