Study On The Mechanism Of Boost PFC Radiated EMI In Critical Mode

With the wide usage of switching power supply and power factor correction(PFC) technology in medical devices, three-dimensional printing, aerospace and other fields, which can effectively improve the power supply quality and utilization.However, Switching power MOSFETs and IGBTs and other semiconductor devices will produce high transient current and electromagnetic interference (Electromagnetic Interference, EMI) noise, seriously affecting the normal operation of electronic equipment and space electromagnetic environment. Aimed at the above problems, this paper is based on the Boost PFC radiation EMI noise model under the critical working mode, and reveals the radiation noise mechanism caused by the high frequency current of the semiconductor device, In addition, it proposes a Boost inductance current recoil design method which can effectively suppress the high frequency noise so as to provide theoretical and experimental basis of High frequency noise suppression and space electromagnetic environment, including:1 .The buck topology of Buck circuit, Boost and Buck-boost, and the equivalent circuit model of PFC circuit are analyzed. The control principle of intermittent,continuous and critical working modes of the circuit including the effects of different circuit topologies and working modes are compared and further researched.Advantages and disadvantages, including power factor and current transient rate of change.2.The radiation EMI model of Boost PFC circuit under critical working mode is established, and the high frequency noise current caused by Boost PFC switching device is extracted. The mechanism of radiation noise caused by Boost inductance and high frequency current is revealed. By using Helmholtz equation,Lorentz condition, delay potential equation, current density and energy density function to establish the electric field radiation EMI and magnetic field radiation EMI noise analytical equation.3.The effect of Boost inductance and parasitic capacitance on inrush current recoil, transient current change rate and radiated EMI noise are studied. The effect of Boost inductance and parasitic capacitance on Boost PFC circuit are proposed. Boost PFC hardware circuit(L6564H), is also carried out based on RE 101 (magnetic field radiation)and RE 102(electric field radiation) circuit EMI standard detection experiment.Theoretical analysis and experimental results show that the Boost inductance current recoil method can effectively suppress the radiated EMI noise of the Boost PFC circuit in the critical mode. The noise of the magnetic field can be reduced by 2 dBpT in the 25 Hz-100 kHz band. Moreover, the radiation EMI noise can be reduced by 20 dB?V/m in the 100 KHz-5 MHz band, which verifies the radiation EMI model of Boost PFC circuit in critical working mode, may well provide theoretical and experimental basis for high frequency noise suppression and space electromagnetic environment control of switching power supply.