Research On Electromagnetica Interference Of Switching Power Supply Based On GaN

Electromagnetic interference has been a known problem since the introduction of silicon-based BJT,MOSFET and IGBT.EMI noise is inevitable due to sudden changes in current and voltage caused by switching on and off of semiconductor devices.Noise travels through conductors and space in the form of conduction and radiation.With the development of wide bandgap devices such as gallium nitride(GaN)transistors,silicon carbid(Si C)BJT and MOSFET,higher power density and circuit efficiency can be achieved by taking advantage of their high switching frequency and larger temperature range.With a more compact design,EMI control at high frequencies becomes more challenging in terms of functional issues,operational robustness,increased costs,thermal constraints,and space constraints.Due to the superior switching capability of WBG(wide band gap)devices,more and more attention has been paid to the non-inductive circuit topology,such as the switching capacitor circuit.Due to the rapid change of node voltage,the inherent common-mode noise of this circuit is very serious.The thesis takes switched-capacitor circuits as the research object,and puts forward a method to suppress CM(common mode)noise,and performs simulation verification in PSpice environment.Starting from the theoretical analysis of EMI,this theses introduces the three elements of EMI and the classification of electromagnetic noise,and analyzes the generating mechanism of all kinds of noise and the characteristics of magnetic components at high frequencies.The mechanism and path of conduction noise are analyzed emphatically.After introducing the strategy of suppressing noise by designing the filter,the passive components in the filter are modeled and analyzed,and the performance of the CM choke is evaluated and predicted by using the PSpice model,with an accuracy of up to100 MHz.In addition,this theses also analyzes the capability of Y-capacitor's grounding to effectively suppress CM noise.Many researchers have determined that rapid transients of dv/dt and di/dt with various parasitic elements are responsible for leading to the main conducting noise in pulse width modulation(PWM)controlled converters and inverters.In order to predict the emission level of conducted noise,it is necessary to identify the noise path at the initial design stage of the electronic circuit.In this theses,PSpice circuit modeling and transient analysis are carried out,and the transmission path of CM noise is predicted and recognized based on GaN's switching capacitor circuit.On the basis of deducing the equivalent circuit of CM noise,the improved scheme of reducing CM noise is proposed based on the circuit balance theory,which is verified in the computer simulation test.Through simulation and experimental verification,the passive device model obtained can be used to analyze the grounding effect of common mode noise,and the accuracy of the active device model to predict the noise path is also verified.The combination of active device model and passive device model will greatly reduce the overall noise level.