Noise reduction in power electronics circuits

In the power conversion operation of power electronics, electromagnetic noise is generated by the switching operation of power devices. There are two types of electromagnetic noise in circuits: differential mode, which is superimposed in the opposite phase on the paired circuit wiring, and common mode, which is superimposed in the same phase. Differential-mode electromagnetic noise has a relatively small propagation path and is easily filtered out. On the other hand, common mode electromagnetic noise forms a large loop because its propagation path is formed between the common mode and the ground through parasitic capacitance, etc., and it easily radiates to the outside and has an impact. In particular, if the parasitic components such as the ground capacitance of the power devices that make up the circuit are unbalanced, the common mode component flowing through the ground tends to become large. In a vertical power device, the source (emitter) and gate are on the front side and the drain is on the back side. In a bridge structure with these devices arranged in the upper and lower arms, the ground-to-ground structure of the positive and negative poles becomes asymmetric, and common mode electromagnetic noise is easily generated. By compensating for the unbalanced parasitic components and equalizing them, common-mode electromagnetic noise is less likely to flow. In other words, we aim to reduce electromagnetic noise by designing circuits that satisfy the equilibrium condition.

Research work