COMPRESSED-AIR SUPPLY UNIT, COMPRESSED-AIR SUPPLY SYSTEM, VEHICLE AND OPERATING METHOD

A compressed-air supply unit is for a sensor cleaning device and includes a compressed-air connection, a compressed-air supply connection, a main pneumatic line from the compressed-air connection to the compressed-air supply connection, and an air dryer arranged in the main pneumatic line. A water separator is arranged in the main line between the compressed-air connection and the air dryer. A branching line branches off from the main pneumatic line between the water separator and the air dryer and reconnects to the main pneumatic line between the air dryer and the compressed-air supply connection. The branching line has a pneumatic branching line switch valve which opens the branching line so as to allow a pneumatic flow in the direction of the compressed-air supply connection in a first operating mode. In the first operating mode, the compressed-air supply unit is configured to allow a recirculation of compressed-air out of the branching line.