Font Size: a A A

Research On A Passive Lossless Snubber With Minimum Voltage Stress

Posted on:2005-11-19Degree:MasterType:Thesis
Country:ChinaCandidate:X G QuFull Text:PDF
GTID:2132360122997792Subject:Power electronics and electric drive
Abstract/Summary:PDF Full Text Request
Switch-mode-power-supply (SMPS) has been widely used because of its small volume, light weight, high power density and good performance. With the enhancement of frequency, Electro-Magnetic Interference (EMI) problem produces, the dissipation of the main power switch increases as well. How to improve the operation circumstance of the switch, how to decrease the current and voltage stress of the main switch during turn on and turn off transient, become one of the focus people study.The efficient approach to solve switching dissipation is to use soft switching technique. It can be classified into two groups of active and passive according to the use of additional switch. The passive one can also be classified into passive dissipation and non-dissipation. The active soft-switching method can achieve real soft switch, provides zero voltage or zero current turn on, zero current or zero voltage turn off. It can solve power dissipation efficiently and improve the efficiency of the converter. Because of introduction of the additional switch, the control circuit of the converter becomes complex and the amount of the added parts and cost increases. While using passive lossless soft switching technique, the zero current turn on and zero voltage turn off of the main switch can be achieved, the efficiency of the converter is improved as well. The control circuit of the original converter is not changed too much, the amount of the added parts is small, and the cost is reduced. So it will be used widely.In this thesis, the reason that leads to the dissipation of the switch and EMI was deeply analyzed. One topology of a so-called passive, lossless soft-switching technique with minimum voltage stress was studied and applied to APFC circuit. The operation mode of the circuit is analyzed and the condition of how to achieve soft switch is discussed, how to design the parameters of the snubber is presented as well. SABER was used to simulate the operation of this soft-switching topology, the result showed that it could achieve zero current switchingwhen the main switch turned on and zero voltage switching when it turned off.The principle and implementation of the average current mode control was deeply analyzed in this thesis.Small signal analysis is an efficient tool for the study of power converter. After building a small signal model of a converter, one can deeply and thoroughly study its operation process. The transfer functions between input, output and control can be presented. These transfer functions are the premise of design the control circuit. In this thesis the small signal model of the power stage of the converter was established and analyzed, the relative transfer functions were presented.A prototype of a 250W APFC converter was established to validated the theory analysis and simulation result. A wide adjusted power was used as the input, the output was a constant DC voltage. The result showed that the studied passive lossless soft-switching technique could achieve zero current switching when the main switch turned on and zero voltage switching when it turned off in wide input voltage range. The existence of the soft- switching had no effect on the converter to get high quality factor, and the THD could achieve therequirement as well. Simulation and experiment waveforms were presented, the two formerand the theoretical waveform were basically in consistent.
Keywords/Search Tags:SMPS, Passive lossless soft- switching, Small signal analysis, Average current mode control
PDF Full Text Request
Related items