Pump assembly, breast pump and controller

The embodiment of the utility model relates to a pump assembly, a breast pump and a controller. A pump assembly is configured for use in a breast pump, the breast pump comprising at least one compression unit configured to interact with a breast from which milk is to be extracted by the breast pump, the pump assembly being connectable to the at least one compression unit and comprising a pump device, the pump arrangement is configured to achieve a pressure distribution to be applied to the breast during a milk extraction process when the pump assembly is actually used in the milk pump and the milk pump is operated to perform the milk extraction process, where the pump arrangement comprises a pump conduit comprising a pump element and a pump load arrangement, the pump load device is drivable by the pump element to produce a low pressure stroke in the pressure profile, and wherein the pump device further comprises an energy storage unit configured to receive and mechanically store energy from and release energy