Thermal management apparatus based on a power supply output

Details Thermal management apparatus based on a power supply output Thermal management apparatus based on a power supply output

1999-01-29

2001-04-17

Ray, Gopal C. (Department: 2181)

Electrical computers and digital processing systems: support

Computer power control

C713S322000

Reexamination Certificate

active

06219795

ABSTRACT:

BACKGROUND
The invention relates generally to power management in electronic circuits and more particularly, to power management based on a direct measure of a circuit's power consumption.
Power management techniques in, for example, a computer system typically employ thermal sensors and/or inactivity timers. Thermal sensors provide an indirect mechanism to monitor and control a circuit's power consumption by measuring the heat generated by one or more components within the circuit. System response to an over temperature condition is generally to reduce the operating speed of the computer system's central processing unit (CPU). This may be accomplished by asserting a stop clock signal (an input signal to many modern CPU devices) for some period of time, typically in a pulse width modulation (PWM) fashion, or by actually reducing the system clock frequency.
Many modern computer systems use only a limited number of thermal sensors. Most personal computer systems use only a single thermal sensor located near the CPU. Since the CPU is a large heat source, and one whose power consumption is highly subject to the computational task involved, this approach has been prudent. Still, thermal sensors have a number of limitations which make their use sub-optimal. One limitation is that thermal sensors are generally physically separated from the circuits they monitor. (This is true even if the thermal sensor is part of the CPU die.) Thus, the temperature indicated by a thermal sensor is only a rough estimate of the temperature of a device. Another limitation is that thermal sensors rely on the transfer of thermal energy from the circuits generating heat. This takes time. Thus, the current temperature indicated by a thermal sensor most accurately reflects the temperature of a device at some prior time. Yet another limitation is that thermal sensors located near a CPU are dominated by CPU thermal events. Thus, even though other system components may generate a significant amount of heat (representing a significant amount of power consumption), this generally goes undetected.
Inactivity timers, on the other hand, are generally used to power down input-output (I/O) ports and peripheral devices when they have not been used for a specified amount of time. As such, inactivity timers generally do not protect devices from an over temperature condition when they are being used.
Thus, it would be beneficial to provide a mechanism to protect electronic circuits from an over temperature condition based on a direct measure of a circuit's power consumption.
SUMMARY
In one embodiment, the invention provides an apparatus to manage power consumption in a computer system. The apparatus may include a power source furnishing power to the computer system, a detection circuit, coupled to the power source, to generate a first signal indicating the power transferred to a portion of the computer system from the power source, and a control circuit, coupled to the detection circuit, to generate at least one control signal to effect a power management action based on the first signal. By way of example, the power source may be a switching or linear power supply, and the second signal may be a fan control signal, a processor halt signal, or a processor interrupt signal, or a stop-clock signal.
In another embodiment, the invention provides a program storage device readable by a programmable control device that includes instructions to manage power in a computer system. The program storage device includes instructions to receive a power signal from a power source (the power signal furnishing power to a portion of the computer system), generate a first signal indicating the power transferred from the power source to the portion of the computer system, and generate a second signal to effect a power management action based on the first signal.


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