Electricity: motive power systems – Automatic and/or with time-delay means – Responsive to thermal conditions
Reexamination Certificate
1996-09-18
2001-09-04
Martin, David S. (Department: 2837)
Electricity: motive power systems
Automatic and/or with time-delay means
Responsive to thermal conditions
C318S472000, C318S473000, C388S934000, C361S025000
Reexamination Certificate
active
06285150
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a method for controlling the operating voltage of a fan in electrical equipment.
For a power supply with fan cooling, a fan is frequently used whose rotation speed is controlled for noise reduction. Particularly in a quiet office environment, the fan noise using conventional temperature/rotation-speed control is nevertheless considered to be too loud in this case. When reducing the fan rotation speed, care must be taken to ensure that the electronic physical elements which are to be protected remain below the maximum permissible component temperature throughout the entire load and temperature range.
According to a previously known method, the air temperature of the power supply is converted into a control voltage for the fan with the aid of a power stage and a temperature-dependent physical element, for example using a so-called NTC or PTC thermistor, that is to say a resistor whose resistance becomes correspondingly greater when it is cooled down or heated up, respectively. The temperature/voltage characteristic which is used in this case is at the same time relatively flat or broad, that is to say the control voltage rises in a wide range, for example between 20° Celsius and 60° Celsius, from a basic voltage level to the maximum fan voltage.
In the case of some fan controllers, the temperature sensor is mounted on a heat sink of power components in the power supply so that the output power of the power supply is also taken into account when setting the fan operating voltage.
U.S. Pat. No. 5,197,858 discloses a temperature-controlled speed adjustment of fans in electrical equipment, which adjustment carries out the control of the fan in such a manner that the fan rotation speed is set to be constant at a first value up to a first equipment temperature limit. After this, the fan rotation speed is continuously increased up to a second equipment temperature limit. Above the second equipment temperature limit, the fan rotation speed remains constant.
In this context, a circuit arrangement is admittedly specified in which the respective equipment temperature limits can be adjusted between which the continuous rise in the fan rotation speed is intended to take place. However, only the principle is in fact specified as to how regulation of the fan rotation speed is intended to be carried out. The regulation of the fan rotation speed is admittedly related to a reduction in the fan noise. However, no proposal is made as to how the fan noise can be reduced to the maximum extent while maintaining the cooling function for an associated electrical equipment.
“PC-Lüfterregler” (PC fan regulators) by Svenkerud/Kristiansen in DE-Z “Elektor” (Elector), Issue 7-8/92, page 22 discloses a circuit arrangement for controlling the fan RPM of a fan in an electrical apparatus, which, besides a start-up controlling, carries out a fan RPM controlling, such that after the fan is started up, the fan RPM is controlled continuously with an increasing temperature in the electrical apparatus. For this purpose, an inception point and an increase function for the controlling are defined. The inception point is at 2° C. and the increasing is determined such that the fan RPM increases continually as the temperature increases up to a temperature of 30° C. The basis for the controlling is the air temperature in the electrical apparatus, which the control range of 2° C. through 30° C. matches. With the proposed air controlling, a noise reduction is achieved, however, the noise reduction does not correspond to the noise reduction that could be maximally achieved
SUMMARY OF THE INVENTION
An object of the invention is to specify a method for controlling the operating voltage of a fan in electrical equipment, by means of which method a maximum noise reduction in the fan is achieved in a cheap manner while maintaining required cooling performance.
In general terms the present invention is a method for controlling the operating voltage of a fan in an electrical equipment for cooling electrical physical elements used in the electrical equipment. The physical elements can assume a component temperature to above a maximum permissible operating temperature as a function of an instantaneous power and an ambient temperature. The temperature of an output diode of an output circuit of the power supply of the electrical equipment is monitored. The operating voltage of the fan is controlled as a function of the component temperature of this output diode such that up to a limit temperature which is in the region of the maximum permissible component temperature of a physical element which absolutely becomes the hottest in the electrical equipment. The operating voltage of the fan is regulated at a constant, minimum level. The operating voltage is then regulated to rise continuously and rapidly as a function of the temperature up to an operating voltage at which the increase in the fan rotation speed associated therewith still ensures that, although the component temperature of the physical element which absolutely becomes the hottest is still above the limit temperature, it is below the maximum permissible component temperature of this physical element.
In an advantageous development of the present invention a higher starting voltage is used for starting the fan than the minimum operating voltage of the fan after starting.
According to this, the fan is always operated at an operating voltage which is as low as possible. This is achieved by the following points.
A physical element in the power supply is used as the reference physical element for the determination of a temperature at which regulation is intended to take place, since this results in physical elements whose temperature responses correspond in a very highly proportional manner to the equipment power and thus make it possible to deduce how hot other physical elements in the equipment will become, in detail. On this basis, it is not necessary to monitor other temperature-critical physical elements in addition, even if this could still be done, in addition, directly. It is necessary only to determine the relationship between the reference physical element and a respective other physical element and then to set the regulation of the temperature of the reference physical element in such a manner that the maximum operating temperature of a respectively desired other physical element is also taken into account.
The output diode of an output circuit of the power supply with the greatest power to be emitted is used, in particular, since this component is one of the physical elements which becomes the hottest and, in addition, this component is as a rule already mounted on a heat sink so that its temperature response is correspondingly slow and a temperature sensor can very easily be provided.
As a result of the control of the fan according to the invention, the rotation speed of the fan is not accelerated until extremely late and then in all cases only to the extent that sufficient cooling is just still provided.
Electrical equipment, such as a personal computer, is composed of a main component or processor and a power supply. A fan is located in the power supply. The fan produces an air-flow in the electrical equipment. In a typical embodiment air at a first temperature enters the main component by a slot in the side of a case of the electrical equipment. The air that emerges from the main component at a second temperature then enters the power supply. The air which enters the power supply at the second temperature is measured in the power supply either by a temperature dependent thyristor having a positive temperature coefficient or by a temperature dependent thyristor having a negative temperature coefficient. The operating voltage of the fan is regulated as a function of the measured air temperature. The air in the power supply is then blown out of the power supply by the fan. This draws further fresh air into the main component. This is the typical operation in the prior art.
The operating voltage of the fan is controlled
Adam Jurgen
Busch Peter
Martin David S.
Schiff & Hardin & Waite
Siemens Nixdorf Informationssysteme Aktiengesellschaft
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