A heat exchanger assembly for cooling an electrical component, comprising: at least one passive cooling circuit, the passive cooling circuit comprising an evaporator connectable to a device to be cooled for conducting heat from the device to be cooled to the cooling fluid within the evaporator, thereby evaporating the cooling fluid, and a condenser interconnected with the evaporator for receiving the evaporated cooling fluid from the evaporator, releasing heat from the cooling fluid to an environment of the condenser, thereby condensing the cooling fluid, and for returning the condensed cooling fluid to the evaporator; an active partial circuit comprising a compressor and an auxiliary condenser, the active partial circuit being activatable and deactivatable and being connected to the passive cooling circuit for receiving, in an activated state of the active partial circuit, the cooling fluid from the evaporator, for compressing the received cooling fluid by the compressor, for releasing heat, by the auxiliary condenser, from the compressed cooling fluid to an environment of the auxiliary condenser, and for returning the condensed cooling fluid to the evaporator, wherein the passive cooling circuit comprises a coolant connection from the condenser to the active partial circuit, or wherein the passive cooling circuit comprises a coolant connection from an area of the evaporator to the active partial circuit, particularly from an upstream area of the evaporator to the active partial circuit, wherein the passive cooling circuit is a base-to-air type thermosiphon or an air-to-air type thermosiphon, characterised in that the heat exchanger assembly further comprises a controllable activation means (230, 231, 232) for selectively switching the active partial circuit between the activated state and the deactivated state, and a control device capable of controlling the activation means (230, 231, 232) such that the active partial circuit is switched to the activated state for a compression cycle cooling mode, and such that the active partial circuit is switched to the deactivated state for a passive cooling mode, according to an operating condition of the heat exchanger assembly; wherein the control device is configured to control, in the activated state of the active partial circuit, the compressor such that it operates and the passive cooling circuit is combined with the active partial circuit for performing a vapor compression cycle, and to control, in the deactivated state of the active partial circuit, the compressor such that it ceases to operate. at least one passive cooling circuit, the passive cooling circuit comprising an evaporator connectable to a device to be cooled for conducting heat from the device to be cooled to the cooling fluid within the evaporator, thereby evaporating the cooling fluid, and a condenser interconnected with the evaporator for receiving the evaporated cooling fluid from the evaporator, releasing heat from the cooling fluid to an environment of the condenser, thereby condensing the cooling fluid, and for returning the condensed cooling fluid to the evaporator; an active partial circuit comprising a compressor and an auxiliary condenser, the active partial circuit being activatable and deactivatable and being connected to the passive cooling circuit for receiving, in an activated state of the active partial circuit, the cooling fluid from the evaporator, for compressing the received cooling fluid by the compressor, for releasing heat, by the auxiliary condenser, from the compressed cooling fluid to an environment of the auxiliary condenser, and for returning the condensed cooling fluid to the evaporator, wherein the passive cooling circuit comprises a coolant connection from the condenser to the active partial circuit, or wherein the passive cooling circuit comprises a coolant connection from an area of the evaporator to the active partial circuit, particularly from an upstream area of the evaporator to the active partial circuit, wherein the passive cooling circuit is a base-to-air type thermosiphon or an air-to-air type thermosiphon, characterised in that the heat exchanger assembly further comprises a controllable activation means (230, 231, 232) for selectively switching the active partial circuit between the activated state and the deactivated state, and a control device capable of controlling the activation means (230, 231, 232) such that the active partial circuit is switched to the activated state for a compression cycle cooling mode, and such that the active partial circuit is switched to the deactivated state for a passive cooling mode, according to an operating condition of the heat exchanger assembly; wherein the control device is configured to control, in the activated state of the active partial circuit, the compressor such that it operates and the passive cooling circuit is combined with the active partial circuit for performing a vapor compression cycle, and to control, in the deactivated state of the active partial circuit, the compressor such that it ceases to operate.