A Real Redundant Fan Module with Alternative Tachometer

A Real Redundant Fan Module with Alternative Tachometer

We propose a "real" redundant fan module. The redundant behavior will be controlled inside the redundant fan module. On system point of view, system looks the new redundant fan module as a single fan. Originally, redundant fan requires 6 pin connections. But now, we want to keep 4-pin connection to system, instead, which provide fan-speed sensing, redundant fan feature. The new design could show more fan module status (ok, single fan failed, or both fans failed) than conventional redundant fan does.

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Tachometer Output Algorithm of the New Redundant Fan Module
Behavior of the Tachpin on the new redundant fan module

A controller on the module would send the Tachpin signal to system by this algorithm.

While (true){
if(fan1==ok and fan2==ok)

{tech=avg{fan1_speed, fan2_speed}; // output formula could pre-defined by user
// ex. tech=max{fan1_speed, fan2_speed}
// or it could show alternative fan-speed values by time division modulation (TDM)

else if(fan1==ok and fan2==fail)
{tech=1; // if one of two fans is failed, tech outputs high }

else if(fan1==fail and fan2==ok)
{tech=1; // if one of two fans is failed, tech outputs high }

else
{tech=0; // if two fans are both failed, tech outputs low continue; // back to while (true)
}

}

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