Common Mode EMI Mitigation in Power Inverters Using Output Delay Compensation

The techniques used to reduce the electromagnetic interferences (EMI) generated by power inverters, in order to comply with the standards, can be classified as hardware and software. The latter are usually preferred because cheaper and flexible. Often the inverter output waveforms, which are modulated by bipolar PWM, are not perfectly aligned, due to the delay introduced by the circuit components. This misalignment generates common mode (CM) conducted emissions. Among the software approaches, one consists in aligning these output waveforms. The present paper proposes a new EMI on-board sensing technique to control the output waveform alignment. Mixed-signal simulations show that the proposed technique is able to reduce the CM emission spectrum over a wide frequency range. Moreover, this approach does not affect either the power loss or the system safety.