Electricity: measuring and testing – Determining nonelectric properties by measuring electric...
Reexamination Certificate
2001-11-05
2004-04-13
Le, N. (Department: 2858)
Electricity: measuring and testing
Determining nonelectric properties by measuring electric...
Reexamination Certificate
active
06720756
ABSTRACT:
FIELD
Embodiments of the present invention relate to fan speed control, and more specifically, to controlling the fan so that it is perceived as quieter.
BACKGROUND
Illustrated in
FIG. 1
is a portion of a computer system comprising central processing unit (CPU)
102
, chipset
104
, graphics card
106
, and memory
108
. Chipset
104
allows for communication between CPU
102
, memory
108
, and graphics card
106
, as well as other peripheral components (not shown) connected to system bus
110
. One or more of these system components may generate an appreciable amount of heat, so that fan
112
is employed to cool part or all of the computer system. Usually, CPU
102
generates the most heat, and for some computer systems, more than one fan may be employed.
Customers of computer systems, both in the home and in business, often prefer computer systems with quiet fans. As a result, many original equipment manufacturers are sensitive to the acoustic noise generated by fans. One approach to reducing fan noise is to adjust the fan speed according to measured temperature, as shown in FIG.
1
. Heat sensor
112
provides to fan voltage controller
114
a signal indicative of temperature. Heat sensor
112
may be placed near CPU
102
, for example, and may be integrated with CPU
102
. Fan voltage controller
114
provides a fan control voltage to fan
112
so as to adjust the speed of fan
112
. When heat sensor
112
indicates that maximum cooling is needed, the fan control voltage is increased to its maximum nominal value so that fan
112
circulates sufficient air flow for cooling. When maximum cooling is not required, fan voltage controller
114
lowers the fan control voltage supplied to fan
112
so that the speed of fan
112
is reduced, along with the accompanying acoustic noise. Fan voltage controller
114
may even cause fan
112
to stand idle.
The combination of sensor
112
, fan voltage controller
114
, and fan
112
comprises a closed feedback loop so that the computer system of
FIG. 1
is sufficiently cooled, so that the acoustic noise generated by fan
112
is reduced when CPU
102
is not operating at its maximum workload. However, the acoustic noise reduction scheme of
FIG. 1
does not provide a reduction in acoustic noise when CPU
102
is operating at its maximum workload.
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patent: 5825972 (1998-10-01), Brown
patent: 6010310 (2000-01-01), MacBeth
patent: 6182902 (2001-02-01), Shih
patent: 6247898 (2001-06-01), Henderson et al.
patent: 6249099 (2001-06-01), Nessi et al.
patent: 6276900 (2001-08-01), Lyszkowski et al.
patent: 6433507 (2002-08-01), Makaran et al.
Beltman Willem M.
Quiet Duane G.
Skinner Harry G.
Kalson Seth Z.
Le N.
Teresinski John
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