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Publication Date: 2011-Jul-27

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An electronic assembly arranged to detect an air flow disruption, the assembly constituted of: an integrated circuit comprising an internal thermal sensor; and a control circuit in communication with the integrated circuit, the control circuit arranged to: receive an indication of ambient temperature information; receive an indication of an internal temperature of the integrated circuit from the internal thermal sensor; receive an indication of power dissipation of the integrated circuit; determine an estimated air flow responsive to the received indication of internal temperature, the received indication of ambient temperature and the received power dissipation indication; and in the event that the determined estimated air flow is different than an expected air flow by more than a predetermined value, output an error signal.

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[0001]                           The present invention relates to the field of fault detection, and more particularly to a method for detecting a disruption in air flow. 


[0002]                           Electronic systems typically require air flow in order to prevent thermal damage caused by heat dissipation.  The heat dissipation may come from a plurality of sources, most notably from the power supply and any dissipative elements.  The air flow may be passive, i.e. without any active element to force the flow of air, or active such as by providing one or more fans.  In either case, a ventilation path is typically supplied to enable ambient air to flow past any heat producing elements, thereby maintaining thermal control.

[0003]                           Increased thermal stress may occur due to a disruption in the air flow, caused either by failure of a fan or by blockage of the air flow path.   Blockage of the air flow path may be partial or complete, and various electronic components are arranged with air flow entry on the sides, bottom or top, without limitation.  Many prior art patents have addressed the issues of detecting an actual fan failure, but unfortunately these patents do not address a secondary cause of thermal stress, namely that of partial or complete blockage of air flow entry or exit points.

[0004]                           In the event of a blockage of one or more entry points, overall air flow will decline, however individual locations may experience an increase in air flow.  For example, a fan associated with a power supply is typically arranged to draw air flow through the power supply, and then exhaust the drawn air via an exhaust air flow point.  In the event that the exhaust air flow point is sealed, the air flow will seek another exit, and may provide increased air flow across certain heat producing elements.  Thus, in certain circumstances, a blocked air flow point may result in a decrease, at least temporarily, of the temperature of certain heat producing elements in an electronic assembly.  

[0005]                           Certain integrated circuits are provided with internal thermal sensors, which are arranged to provide an indication of the semiconductor operating temperature at one or more locations.  For example, the PD 64012 12 channel power over Ethernet (PoE) manager, available from Microsemi Corporation, Irvine, California, exhibits a plurality of internal temperature sensors, and internal dissipative elements.  Other PoE managers are arranged to work with external dissipative elements, while providing internal temperature sensors. 

[0006]                           What is desired, and not provided by the prior art, is a method of detecting a disruption in the air flow.  Preferably, the air flow disruption is detected without requiring a dedicated temperature sensing element.   


[0007]                           In view of the discussion provided above and other considerations, the present disclosure provides methods and apparatus to overcome some or all of the disadvantages of prior and present met...