Analysis, Design And Optimization Of An Isolated High Frequency Differential Inverter With Low Distortion Output Voltage

High precision apparatuses demand high performance from the power supply. However, it is hard to improve the quality of the output voltages in the existing power inverters for their inherent drawbacks. Hence the employments of the conventional inverters in the high precision apparatuses are limited. A comprehensive review of the current solutions of power supplies is taken to analysis the reasons that distort the output voltages. Based on which, a new isolated high frequency differential inverter is proposed. It avoids the problems which the conventional inverters are suffering. Thus, a very high precision output voltage can be obtained without any special control or compensations. Besides, all the switches of the inverter can achieve soft-switching within a wide load range, which is helpful to reduce the EMI in the power supply. Therefore, the new inverter is suitable for the high precision apparatuses. The detailed theoretical study and experimental verifications are made, then an overall solution including design and optimization of the inverter is given as well.Firstly, principle analysis of the proposed configuration is taken. This inverter is composed by two identical isolated high frequency dc/dc converters. Each of the dc/dc converters contains a phase shifted full bridge in the primary side and a synchronous current-doubler rectifier in the secondary side. The outputs of the two dc/dc converters are connected across the load and constitute differential structure. How the proposed scheme produce a sinusoidal output voltage and why it can obtain high precision performance are discussed. Moreover, the criteria for the switches to achieve soft-switching are given. Besides, equivalent mode of the circuit is derived. These theoretical analyses lay the foundation for the later design and optimization of the circuit.Then the designs of the inverter are given, and based on which a prototype is built to verify the theories. Non-ideal factors and their effects over the distortion of output voltage are expounded. Consequently, the countermeasures in circuit design are given. The design methods for parameters of the circuit and control loop are discussed. A prototype is built and the experiments validate the correctness and feasibility of the theories.Thirdly, power loss of the proposed inverter and its distribution are discussed, and the corresponding optimal design is given. The original design emphasizes the output waveform quality, which leads to relatively lower efficiency. In this dissertation, loss distribution of the circuit are analyzed and the main source of the loss is located. Optimization is then proposed. Comparative experiments indicate that the new design can improve the efficiency significantly while largely maintain the precision of the output voltage.Finally, extension of the differential inverter from single phase to the multiphase is discussed. Especially in the case of three phase inverters. It has not only theoretical but also pratical value in such extensions. Three phase inverter is taken as the demonstration of multiphase differential inverters. Also, simulation results are given to certificate the analyses.