Method for eliminating magnetic saturation in low-voltage and high-current DC-DC converter with fast dynamic response is described. The magnetic saturation is observed in onboard isolated bridge-type DC-DC converter due to inherently asymmetrical PWM signal during transient condition. The saturation is not eliminated by using ac-coupling capacitor for transformer. Mechanism of the saturation is analyzed and confirmed by experiments. Based on the analysis a solution for the magnetic saturation is proposed. The effectiveness of proposed method is also confirmed by experiments.