The invention relates to an apparatus comprising a functional component likely to be thermally overloaded during the operation thereof, and a system for cooling the component, comprising: a thermoelectric module comprising a cold surface and a hot surface, the cold surface being thermally coupled with the component; a heat sink thermally coupled with the hot surface of the module, the heat sink including an exchange surface with the surrounding environment and at least one cell containing a phase-change material (PCM), the PCM material contained in the cell or cells being suitable for melting when the heat released from the cold surface of the module is that of the thermally overloaded component, the exchange surface being suitable for bringing the PCM material from the molten phase to the solid phase thereof when the heat released from the cold surface of the module is that of the operational component which is not thermally overloaded.