Analysis of Low Noise Switching Waveform Considering Both Laminated Bus Bar and Terminal Geometry for AC Resistance

This paper presents a design procedure of a low noise switching waveform considering AC resistance both the laminated bus bar and terminal geometry. It is hard to calculate the AC resistance which increases depending on the frequency because of skin and proximity effect. Hence the relationship between laminated bus bar geometry and its AC resistance is visualized to realize the design of AC resistance. Besides, it is shown that the terminal geometry, where the capacitor and power devices are connected, affects AC resistance components. The damped oscillation waveform, which is one of the causes of electromagnetic noise, under switching operations will occur under high-speed switching operation. In this case, the oscillation frequency depends on the parasitic parameters of the converter circuit geometry, and it is normally over 10 MHz. This paper presents that AC resistance considering the bus bar and terminal geometry, and it makes damping factor larger than that of only DC resistance to suppress the damped oscillation level. In this paper damped oscillation of drain-source voltage of SiC-MOSFET is simulated and experimented using buck converter circuit, rated at 500 V and 30 A.