Closed-Loop Gate Drive for Single-Ended Forward Converter to Reduce Conducted EMI

Forward DC/DC converters are widely used in low and medium power circuits that are widely used in the aerospace and navigation fields. Power converters are usually sources of electromagnetic interference (EMI), which is due to their higher voltage and current transients. The traditional method is to add expensive filters on the primary side or the secondary side, but its disadvantages are high cost and poor adjustability. Based on the principle that the greater the number of derivations of voltage transients, the lower the high frequency electromagnetic interference contained in this voltage, a signal containing small high-frequency noise that is suitable for the hardware circuit as a reference signal is selected, and a closed-loop gate drive method is used in this paper, which attenuate the conducted EMI noise in the input bus of the forward DC/DC converter. The reference signal shapes the output signal to achieve the purpose of suppressing electromagnetic interference through the closed loop circuit. The advantages of this method are making the output highly adjustable, reducing hardware size and weight and lower cost compared with filter method. Compared with the method of controlling current to reduce electromagnetic interference, the proposed method is easier to implement. Firstly, the relationship between the derivative order of voltage transient and electromagnetic interference is introduced. Secondly, the experimental principle of single-ended forward circuit controlled by closed loop is introduced. Simulation and experimental results show that the proposed method can achieve voltage shaping and suppression of voltage overshoot effectively. Compared with the traditional hard-switching control method, the proposed method can make the high-frequency components of the drain-source voltage of the primary-side MOS transistor and the secondary-side output voltage have a greater attenuation.