Patent ID: 7995340
Filing Date: 2011-08-09
Classification: H01L,H05K

Abstract:
1. A ventilation device ventilating an electronic module and being supplied with electrical energy by a power supply unit, the ventilation device comprising: a motor; a fan fixed to the motor, the fan comprising a shaft and at least one blade fixed to a hub of the shaft; a protective screen comprising an anti-dust filter; a selector switch connected between the power supply unit and a motor of the ventilation device: and a control circuit connectable to the selector switch, a comparator circuit coupled to the control circuit; and an alarm coupled to the comparator circuit, wherein the selector switch has a plurality of states, wherein each state corresponds to a sense of rotation of the fan, wherein the sense of rotation comprises a first sense and a second sense that is opposite of the first sense, and wherein the control circuit is configured to switch the selector switch amongst the plurality of states so as to operate the fan in the first sense for a first duration and the second sense for a second duration, to compute an efficiency from variation in temperature of the electronic module, and to adjust one of the first duration and the second duration by a pre-defined fraction F, wherein the control circuit is further configured to adjust the pre-defined fraction F to maintain the efficiency as constant during operation of the electronic module, and wherein the comparator circuit generates an output to activate the alarm in response to the computed efficiency deviating from a pre-defined efficiency for said ventilation device.