The invention is a device (1) for cooling a power electronic system (EP) comprising at least one power electronic component (2) mounted on at least one circuit board (3), the cooling device (1) comprises a hose (4) for circulating a flow (5) at an ambient temperature. The cooling device (1) comprises a first heat exchange surface (6) that is thermally connected to the power electronic components (2) and at least one second heat exchange surface (7). The second heat exchange surface (7) is for heat exchange with the flow (5) circulating through the hose. The second heat exchange surface (7) is fitted inside the circulation hose (4) to remove heat by convection with the circulating flow (5). The second heat exchange surface (7) is thermally connected to the first heat exchange surface (6).