A thermal ballast temporarily stores heat generated during a heat generating device's operation thereby extending the device's operating time during an interval of adverse thermal operating condition. The thermal ballast (10) includes: a. a highly thermally conductive layer (42) that is adapted for being thermally coupled to the heat generating device; and b. a high heat capacity layer (44) that is laminated to the high thermal conductivity layer (42). The high heat capacity layer (44) may be formed from a solid piece of a suitably chosen material. Alternatively, the high heat capacity layer (44) may be formed from a piece of a suitably chosen material having a cavity that is filled with a material (46) which changes phase at a temperature below the heat generating device's maximum operating temperature. Disclosed are various different ways for infusing the material (46) which changes phase at a temperature below the heat generating device's maximum operating temperature into the high heat capacity layer (44) and retaining the material (46) therein.