Piston-type pressure converter comprising at least one master cylinder in which a master drive piston can move in such a way as to define a variable-volume master chamber able to be placed in communication with a master intake pipe via a master intake valve or with a master delivery pipe by a master delivery valve, the said pressure converter also comprising at least one slave cylinder in which a slave pump piston can move in such a way as to define a slave chamber, likewise of variable volume, the latter being able to admit a hydraulic fluid coming from a slave intake pipe via a slave intake valve shutter or deliver the said fluid to a slave delivery pipe via a slave delivery valve shutter, the master chamber and the slave chamber each being filled with a hydraulic fluid, characterized in that the pressure converter further comprises an end-of-stroke pressure reducer comprising: • at least one pressure-reducer master cylinder, filled with a hydraulic fluid, and in which a pressure-reducer master drive piston can move in such a way as to define a variable-volume pressure-reducer master chamber which communicates with the master chamber and/or at least one pressure-reducer master cylinder, filled with a hydraulic fluid, and in which a pressure-reducer master drive piston can move in such a way as to define a variable-volume pressure-reducer master chamber which communicates with the slave chamber; • at least one pressure-reducer slave cylinder which collaborates with the pressure-reducer master cylinder and in which a pressure-reducer slave pump piston can move in such a way as to define, with the said slave cylinder, a variable-volume pressure-reducer slave chamber filled with a hydraulic fluid, the said slave pump piston being mechanically connected to the pressure-reducer master drive piston by a progressive-effect lever transmission arranged in such a way that when the pressure-reducer master drive piston is at top dead centre, the pressure-reducer slave pump piston is at bottom dead centre, and vice versa; • at least one pressure-reducer slave intake valve shutter which opens into the pressure-reducer slave chamber and allows a hydraulic fluid contained in a pressure-reducer slave intake pipe to enter the said slave chamber but not to leave it; • at least one pressure-reducer slave delivery valve shutter which opens into the pressure-reducer slave chamber and allows a hydraulic fluid contained in a pressure-reducer slave delivery pipe to leave the said slave chamber but not to enter it; • at least one pressure-reducer unblocking actuator which is able, through contact or mechanical connection, to cause the progressive-effect lever transmission to start to move or unblock same. • at least one pressure-reducer master cylinder, filled with a hydraulic fluid, and in which a pressure-reducer master drive piston can move in such a way as to define a variable-volume pressure-reducer master chamber which communicates with the master chamber and/or at least one pressure-reducer master cylinder, filled with a hydraulic fluid, and in which a pressure-reducer master drive piston can move in such a way as to define a variable-volume pressure-reducer master chamber which communicates with the slave chamber; • at least one pressure-reducer slave cylinder which collaborates with the pressure-reducer master cylinder and in which a pressure-reducer slave pump piston can move in such a way as to define, with the said slave cylinder, a variable-volume pressure-reducer slave chamber filled with a hydraulic fluid, the said slave pump piston being mechanically connected to the pressure-reducer master drive piston by a progressive-effect lever transmission arranged in such a way that when the pressure-reducer master drive piston is at top dead centre, the pressure-reducer slave pump piston is at bottom dead centre, and vice versa; • at least one pressure-reducer slave intake valve shutter which opens into the pressure-reducer slave chamber and allows a hydraulic fluid contained in a pressure-reducer slave intake pipe to enter the said slave chamber but not to leave it; • at least one pressure-reducer slave delivery valve shutter which opens into the pressure-reducer slave chamber and allows a hydraulic fluid contained in a pressure-reducer slave delivery pipe to leave the said slave chamber but not to enter it; • at least one pressure-reducer unblocking actuator which is able, through contact or mechanical connection, to cause the progressive-effect lever transmission to start to move or unblock same.