A new primary-side-assisted zero-voltage and zero-current switching full bridge de-dc converter with transformer isolation is proposed. The proposed de-de converter uses only one auxiliary transformer and two diodes to obtain ZCS for the leading leg. It has a simple and robust structure, and load current control capability even in short circuit conditions. Possibility of magnetic saturation due to asymmetricity of circuits or transient phenomena is greatly reduced, which is a very attractive feature in dc-dc converters with transformer isolation. The power rating of the auxiliary transformer is about 10% of that of the main transformer. Operation of a 12 KW prototype designed for welding application was verified by experiments.