A Closed Loop Delay Compensation Technique to Mitigate the Common Mode Conducted Emissions of Bipolar PWM Switched Circuits

This article presents the design of a new closed loop technique that reduces the common mode conducted emission. It can be applied to any kind of switching circuit in which couples of outputs are modulated by a bipolar PWM signal. It is based on the compensation of the delay between complementary output switching edges, using a simple sensing circuit and a low computational effort software algorithm, which is implemented in a microcontroller driving the switching circuit. One of the main advantages of the proposed solution is the reduction of the disturbance energy, without affecting the system efficiency. The technique is practical to implement, and the measurements performed on a power inverter prototype confirm the theoretical analysis outcomes about the reduction of the conducted emission in the lower-to-medium frequency range.