How does the dead zone of an EPS inverter cause EMC problems?

Dead time in EPS inverters is designed to prevent shoot-through between upper and lower bridge arms, and its impact on EMC is two-sided. The negative impact is the introduction of output voltage distortion (dead-time effect), generating low-order harmonic voltages related to the switching frequency. These harmonics can interfere with the system through conduction and radiation. A longer dead time exacerbates this distortion. The positive impact is that a reasonable dead time ensures complete turn-off of the switching transistors, avoiding large current pulses caused by overlapping conduction and the resulting severe di/dt noise, which helps suppress high-frequency EMI spikes.

Therefore, setting the dead time requires a trade-off: while ensuring safety and preventing shoot-through, the dead time should be shortened as much as possible by optimizing the drive circuit speed and selecting fast components to reduce output voltage harmonics, while relying on other means (such as output filtering) to suppress the noise of the switching process itself.