A new type of soft switched bidirectional DC-DC converter for automotive electric power systems is presented in this paper. This converter consists of dual half-bridge circuits linked with a high frequency transformer, which is applicable as an interface between a high-voltage DC bus line and a low-voltage power source such as Supercapacitor. In order to reduce the switching losses and expand the soft switching range, a newly developed two-lossless switched capacitor snubber-assisted Zero Current Switching (ZCS) are applied to the primary side circuit. By using this ZCS scheme, the soft switching operation can be achieved for the wide range of output power. The converter operation is demonstrated with simulation results, and its feasibility is verified by experimental using its 1.0 kW-25 kHz prototype system.