An active thermal management system for electronic devices comprises: a heat spreader having an internal channel; a thermally conductive body moveably positioned in the internal channel; and two or more electronic devices in thermal contact with a back surface of the heat spreader and positioned adjacent to the internal channel. A location of the thermally conductive body within the internal channel determines a path for heat flow from the back surface to a front surface of the heat spreader. The location of the thermally conductive body within the internal channel may be selected to minimize a temperature differential (ΔT) between the electronic devices.