Abstract: A DC-to-DC converter for an electrical aircraft propulsion system designed to be connected in series with an electrical energy storage unit of the electrical propulsion system. The DC-to-DC converter includes an inverter, a transformer and a rectifier, and further includes a current source that is connected to the rectifier and is configured to control the power passing through the DC-to-DC converter. The transformer includes a primary and two secondaries, the two secondaries sharing a common terminal designed to be connected to a high-voltage DC bus of the electrical propulsion system and two other terminals that are connected to the rectifier. The rectifier includes two arms including at least two transistors that are each in series and are connected, on the one hand, to the two other terminals of the transformer and, on the other hand, to the current source.