The Improvement Of A Single-ended Flyback Switching Power Supply

Along with the development of economy and the progress of science and technology, saving the energy and protecting the environment have been pay more attention to by all circles of the society. "The technological revolution of 20kHz power supply" brought by the development of the high frequency switching power supply technology, makes it widespread application and rapid development in many industries power supply domain. However the massive use of switching power supply, especially the high power switching power supply, has brought the electromagnetism pollution to power system, has made a large amount higher harmonics and electronmagetic interference (EMI), this point violates the connotation of "the green power source" which was proposed by the power electronics circles recently.The topic takes the auxiliary switching power supply of inverter as the research object, the main reason of making above problems is discussed, one is the nonlinear rectifier with a bulky capacitor in the input stage of switching power supply, which leads to a narrow pulse and rich harmonics; the other is the hard-switching work mode, this makes di/dt and du/dt in circuit increased under the high frequency switching-speed, accordingly makes the EMI to environment increase. To decrease the switching power supply electromagnetism pollution to environment, one way is carrying on the power factor correction (PFC); the other way is using the soft-switching work mode, the soft-switching compared with hard-switching makes di/dt and du/dt greatly reduce during the work progress, thus it enables EMI to be solved.Basing on the above analysis and focusing on the EMI and main lose of switching power supply, the thesis has made some improvements based on the original electric circuit. Mainly includes: 1, the aspect of power factor correction (PFC), using one kind of the passive PFCtechnologies-chase-flows technology, it reduce "the pollution" to power system; 2, theaspect of switching mode, using the active clamp soft -switching in the soft-switching to replace the original hard-switching solves kinds of disadvantage under hard-switching mode well.The thesis gives concrete simulation analysis and experiment to every improvement step, the conclusion verified the feasibility of the improved thoughts and the validity of reducing the environmental pollution and enhancing the power efficiency of it.