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Smooth fan speed avoiding oscillation Disclosure Number: IPCOM000238263D
Publication Date: 2014-Aug-13
Document File: 2 page(s) / 41K

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In the most system thermal design, in order to cool the target components with higher power consumption, system fan is easily oscillated with respect to the work load and cause the noise quality issue. In the temperature base cooling algorithm, temperature hystereses is deployed to fix this; but now, more power base method is used for the cooling algorithm where can enhance the temperature hystereses. In this disclosure, the temperature and power hysteresis are deployed inside the fan algorithm via BMC and fan speed will not decrease until the margin hysteresis is reached. Using this, the fan speed can be stable than not using he hysteresis method.

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Smooth fan speed avoiding oscillation

    With the increasing power on the devices, the component temperature is very sensitive according to its power usage and cause the fan speed oscillation. It is because the fan speed triggered point is around the stabilized temperature. Therefore, in order to avoid this oscillation, the hysteresis is necessary to be used in the algorithm which means that the fan ramp up and down temperature should use individual value. For example, if ramp up is at M=0, the fan speed ramp down should use M+5 (TBD). In this new idea, we deployed the power hysteresis because if the power input is part of the algorithm input, power variation is also causing the fan oscillation especially we are using more and more higher power part components like higher wattage CPU and GPU.

    The Following is the example of the new feature on the temperature and power hysteresis.

    1. Add the hysteresis in CPU margin. Currently, when M

5 (TBD, positive value) to decrease the fan speed with dwell time. Currently, there is no hysteresis in the CPU. When M><0, there is the fan speed change. The way to solve the oscillation is to have the base fan speed increasing to avoid the fan trigger point. It wastes more power. The invention here is to add the margin hysteresis and let the steady state margin value in this range. The fan speed will be stable.

    2. Add the power hysteresis with 10% tolerance in any power base components like CPU, memory, GPU and so on to switch the pow...