This paper describes a simple dc–dc step-up converter topology for switch-mode dc power supplies. The proposed configuration is well suited for high-power applications with battery supply. In the automotive framework, the push–pull architecture is the most widespread. However, as power increases, the use of a full-bridge architecture is mandatory. This paper presents a full-bridge architecture where the traditional single-phase transformer is replaced by a three-phase transformer. A prototype was realized and tested for the power supply of automotive devices. In this environment, one of the most important requirements is the ability to provide a burst of power during short-duration events, together with high-efficiency and high-quality output voltage. The latter constraints can be achieved by only using closed-loop switch-mode dc–dc converters at high switching frequency, thus reducing converter efficiency and creating electromagnetic- compatibility (EMC) problems. In this paper, the aforementioned issues were tackled relying on an open-loop topology. Open-loop converters are feasible if the output resistance of the converter is as low as possible, and a possible solution is the minimization of power losses. The solution is the use of a three-phase transformer with a delta-wye connection within a full-bridge converter topology. The configuration will be referred to as 3boost power supply. The three-phase transformer replaces the common single-phase transformer, and it is driven by a three-phase full-bridge inverter operating in six-step modulation. At secondary, a three-phase full wave diode rectifier is used to obtain the output dc voltage level. Therefore, a unitary transformer utilization factor is achieved. A simple theoretical comparison between the three types of converter: push–pull, conventional full bridge, and 3boost is shown. A low-power version of the converter was realized. Experiments confirm that this topology allows to achieve a high efficiency, a lower ripple factor, and a good EMC behavior.