| The linear power supply is traditionally used as magnetization power supply which is an important device in measuring DC magnetic properties of soft magnetic material. Nowadays, it shows a strong need in application if the traditional linear power supply could be replaced by switching power supplies. With the unique properties such as low power consumption, small in size and light in weight, portable and high efficiency SMPS (switching power supply) will be used in many application fields and become the main stream in engineering. However, the ripple voltage in output of SMPS restricts its application. In the measurement of magnetic properties of materials this disadvantage will definitely affect the measurement results and result in measurement error.GB3657-83 is the national standard measurement methods of DC magnetic properties of soft magnetic materials. First of all, according to research and experiments related magnetization process of soft magnetic materials, the influence of ripple voltage in DC magnetic properties of measurement is analyzed. Secondly, the ripple voltage output in low-frequency during rectification process in SMPS is analyzed. Formulations for ripple voltage output in low-frequency are deduced by power matching method and equivalent current source circuit method. During the energy transmission process, switching frequency ripple voltage of fly-back converter is analyzed. The converter is divided into three operating phrases, i.e., the complete inductor supply mode (CISM), the incomplete inductor supply mode with continuous conduction mode (IISM-CCM), and the incomplete inductor supply mode with discontinuous conduction mode (IISM-DCM). Formulations for switching frequency ripple voltage are deduced respectively in each mode. The measuring ripple voltage can be obtained by using oscilloscope method. Than, the ripple voltage attenuation circuits are designed for ripple voltage of low-switching frequency including the LC resonant filters and LDO circuits. The Simulation with Pspice indicates that ripple voltage is obviously attenuation. Finally, in DC magnetic properties measurement system of the soft magnetic material, a constant current source is designed to eliminate the ripple voltage in the magnetization current.Experimental results show that there is no any difference between the application of adjusted switching power supply in DC magnetic properties measurement system and GB3657-83.Relative error of the measuring result is less than±3%.The textual research work can provide important reference value for the application of switching power supply in magnetic properties measurement system.
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