BACKGROUND OF THE INVENTION Central Processing Units (CPU's) of computers generate large quantities of heat during operation, especially as the speed of operation increases. However, this heat, if confined in the computer housing, can affect the operation and reliability of many heat sensitive elements forming parts of the computer, including the CPU itself, motherboard components, memory, CD ROM, CDRW, DVD, hard drive, Disk on Chip, Magnetic media, floppy drives, electronic cards (such as data acquisition, video, receivers, 3D, I/O ports, communication devices, electronic components, etc.), especially in personal computers, industrial computers, servers, workstations, mainframes, other computers and telecommunication devices. The trend at present is to increase the power of the CPU's, which causes an increase in the temperature inside the computer housing. Accordingly, is it becoming more necessary to find an efficient method of cooling the computer housing.

At present, the most common method is to provide one or more fans inside the housing, one adjacent the CPU particularly for cooling the CPU, and another inside the computer housing, for general cooling of the computer hardware. This method does not provide cooling, in the sense that it does not provide air flow at a temperature below the ambient temperature level.

A number of alternative solutions have been proposed in the patent literature.

There is shown in US 5, 89, 964 to Nakayama, for example, a thermoelectric cooling system including a thermoelectric cooling element comprising two dissimilar metals thermally coupled to a circuit element in a circuit for cooling the circuit element. A

source is provided for applying a driving current to the circuit element, and the circuit is arranged such that the driving current passes to the thermoelectric cooling element as an operating current thereof.

US 5, 896, 917 to Lemont discloses an active heat sink structure for use in the transfer of heat from a heat generating device such as a semiconductor chip with a heat sink having an embedded fan surrounded by a plurality of heat conducting flow augmenting rings separated by apertures through which a radially inward flow arises and with the rings being sufficiently axially separated to enable fan propeller tip vortices to penetrate the axial spacings so as to cause a substantial cooling of annular ring regions so as to raise the overall heat transfer coefficient of the active heat sink.

There is shown in US 5, 890, 371 to Rajasubramanian a hybrid air conditioning system including a passive heat removal system, for pre-cooling the air, and a thermoelectric temperature control system used in conjunction with the passive heat removal system to achieve additional cooling, temperature control and heating. The passive heat removal system includes a heat pipe system.

US 5, 841, 204 to English discloses a temperature control system and method for regulating the temperature of an external device which maintains the actual abvient temperature of the external device at a desired set point temperature.

There are also known devices known as thermoelectric coolers (TEC). A thermoelectric cooler includes two metal plates which, under a voltage difference, pump heat using the Peltier effect. The thermoelectric cooler utilizes electrical current to absorb heat from one side of the cooler (one of the plates) and dissipate that heat on the opposite side (the other plate). These devices are very reliable and cost effective in low wattage applications. However, as the number of watts to be removed increases, the cooling capacity may be limited because of the power supply requirements, since more thermoelectric devices are required, and/or because more cooling power or current is consumed per unit, and because of the heat radiated by the thermoelectric devices themselves.

Accordingly, it would be very desirable to have an efficient temperature control system for a computer enclosure and CPU which does not suffer from the drawbacks of the prior art.

SUMMARY OF THE INVENTION According to the present invention, there is provided an active cooling system for an enclosure of heat sensitive components, having no pre-cooling unit, the cooling system including a thermoelectric cooler unit mounted adjacent the computer, the thermoelectric cooler unit including a hot side heat sink and a cold side heat sink. The thermoelectric cooler unit has a unique form factor-a box having substantially the same length and width as the computer, with a low height profile.

The unit applies cooled forced air to the computer and draws warm air from the computer. Conventional computer casings need only minor adjustments, such as two air passages, a temperature sensor, and sealing means to prevent external air circulation inside the computer.

There is thus provided in accordance with the present invention cooling system for a computer enclosure, having no pre-cooling unit, the cooling system including a thermoelectric cooler unit mounted adjacent the computer enclosure, the thermoelectric cooler unit including at least one thermoelectric cooler module coupled on one side to a hot side heat sink and on another side to a cold side heat sink via a heat transfer element.

According to a preferred embodiment, the cooling system further includes a housing, the thermoelectric cooler unit being mounted in the housing, wherein the thermoelectric cooler unit further includes a hot air intake from the computer enclosure mounted adjacent one end of the cold side heat sink, and a cold air outlet from the thermoelectric cooler unit to the computer enclosure mounted adjacent an opposite end of the cold side heat sink.

There is also provided in accordance with the present invention a method for cooling a computer enclosure, the method including mounting the computer

enclosure adjacent a thermoelectric cooler unit, the thermoelectric cooler unit including at least one thermoelectric cooler module coupled on one side to a hot side heat sink and on another side to a cold side heat sink via a heat transfer element.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be further understood and appreciated from the following detailed description taken in conjunction with the drawings in which : Fig. 1 is a schematic illustration of a computer including the cooling system of the present invention ; Fig. 2 is a schematic illustration of the cooling system according to one embodiment of the present invention ; Fig. 3 is a schematic top view of a cooling system constructed and operative in accordance with one preferred embodiment of the invention ; Figs. 4a and 4b are respective front and top views of the cooling system of Fig. 3; Fig. 4c is a sectional view of the cover of the cooling system of Fig. 3 ; Fig. 5 is a flow chart of the operation of the cooling system of the present invention ; Fig. 6 is a plan view of a cooling system constructed and operative in accordance with another embodiment of the invention ; Figs. 7a, 7b and 7c are respective schematic top, side and front views of a card in the cooling system of Fig. 6 ; and Fig. 8 is a plan view of a cooling system constructed and operative in accordance with yet another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an active system for temperature stabilization and adjustment of enclosures of heat sensitive components, such as computers and communications equipment, etc. It will be appreciated that the performance of a computer CPU and other heat sensitive components is improved when the enclosure has been cooled. The cooling system includes a thermoelectric cooler having a hot side heat sink and a cold side heat sink, and requires no pre-cooling of the air entering the thermoelectric cooler. The present invention permits the use of a highly efficient and economical cooling system, even when the wattage to be removed from the CPU and enclosure is relatively high. In the following description, the active cooling system will be described, by way of example only, with reference to cooling of a computer enclosure, for which it is particularly suited.

Referring now to Fig. 1, there is shown a schematic illustration of a computer system 10 including a thermoelectric cooler according to the present invention.

Computer system 10 includes a computer 12 mounted in a housing or enclosure 14, and coupled to a monitor 16, a keyboard 18, a mouse 20, or other similar input device, an RS232 outlet 22, and an AC mains outlet 24, all as known. According to the present invention, a thermoelectric cooler unit 30 is mounted adjacent computer 12, i. e., beneath, on top of, or beside the computer. While thermoelectric cooler unit 30 can be mounted adjacent the CPU (central processing unit) itself, this is not required. Preferably, the thermoelectric cooling system of the present invention is of about the same length and width as the computer enclosure, so can seat neatly on top of the computer enclosure or beneath it.

Thermoelectric cooler unit 30, illustrated schematically in Fig. 2, includes a power supply 32, which is also coupled to AC mains outlet 24 (Fig. 1). Power supply 32 can be a linear or switching power supply, with or without a planar transformer, preferably with switching power supply. By using a planar transformer and related electronics, the size of the power supply can be significantly reduced. Thermoelectric cooler unit 30 further includes a thermoelectric cooling module (TEC) 34 which

serves as a temperature exchange unit, and a pair of fans 36 and 38 for respectively blowing air into and out from TEC 34. It will be appreciated that it is important to select TECs 34 of the required capacity, depending upon the speed and power dissipation of the CPU and the available power supply.

Small TEC units draw 1 to 2 amperes from a power supply with a voltage range of 5 to 24 volts. Larger TEC units of higher power, as preferred in the present invention, require 3-7 amperes at 12 volts.

A control unit 40 is powered by the power supply 32, and is controllingly coupled to TEC 34 and fans 36 and 38. A temperature sensor 42 is mounted in housing 14 of the computer and coupled to control unit 40 to provide an indication of the temperature inside computer 12. In accordance with the indicated temperature, control unit 40 activates or turns off TEC 34 and fans 36 and 38, as described hereinbelow.

Referring now to Figs. 3, 4a and 4b, there is shown, in greater detail, respective open top, front, and closed top views of a cooling system 50 constructed and operative in accordance with a preferred embodiment of the invention. Cooling system 50 includes a housing formed of a front panel 52, a rear panel 54, an intake side panel 56, an outlet side panel 58, and an optional top cover 60. Front panel 52 preferably includes ventilation slots 62 for hot air intake, as well as a temperature display 64, such as an LCD or LED digital display, coupled to the temperature sensor in the computer housing. An on/off light 66 is preferably provided in front panel 52 to indicate when the power is on in the unit, as well as a light 68 indicating whether the cooling unit is operating or not.

Rear panel 54 of cooling system 50 may include an optional power on/off switch 70. Otherwise, cooling system 50 turns on automatically when turning on the computer. Rear panel 54 also includes an AC inlet 72, for coupling a power supply 74 to the AC mains, and an optional AC outlet 76 for connecting the computer itself.

A communication connector or terminal 78 is coupled via an input/output connector 79 to a control unit 80, to permit interaction of the computer with the cooling unit, for instance, for collecting temperature data or making a correction or remote

adjustment to the control unit and, thus, to the cooling system itself. Control unit 80 is powered by a power connection 81 to the power supply 74. A temperature sensor connector 83 is also provided in control unit 80.

Intake side panel 56 includes power supply ventilation slots 82 through which ambient air is intaken into the cooling system. Outlet side panel 58 includes a plurality of side cover outlet ventilation slots 84, to permit the discharge of heated air from the cooling system. The top cover 60, shown in sectional view in Fig. 4c, is lined with insulation material 86, such as Neoprene or Styrofoam, or other insulation material.

A thermoelectric cooler unit 90 is mounted in the housing, separated from power supply 74 and from digital display 64 by insulation material 92, such as Neoprene or Styrofoam or other suitable insulation. Thermoelectric cooler unit 90 includes one or more thermoelectric cooler modules (TEC) 94, each coupled on one side to a hot side heat sink 96, and on the other side to a heat transfer element 98, which is preferably an aluminum element, which can be a cube or have any other shape, or silicon, to provide suitable heat transfer from TEC's 94 to a cold side heat sink 100 mounted in a cold side frame 101. Preferably, heat transfer elements 98 have the same surface area as the TEC's. In addition, they provide an extension to permit placement of an insulation material between the cold and hot sides of the cooler. Suitable insulation material 102, such as Neoprene or Styrofoam, is provided to insulate hot side heat sink 96 from cold side heat sink 100 all along their lengths, except where TEC's 94 are coupled. TEC's 94 are powered by a control unit, as described below.

It is a particular feature of the present invention that a cold side axial fan 106 is mounted on a semi-elevated frame 104 to push cooled air into the computer enclosure. The use of a semi-elevated frame provides better air flow with no pressure of air on the fan. Frame 104 is coupled to cold side heat sink 100 to hold fan 106 in the desired location, for example directly underneath the CPU in a computer enclosure to be cooled. Axial fan 106 takes air from its side and blows it out at 90 degrees through a cold air outlet 108 into the computer enclosure (not shown). In this

way, the air flow can be focused so as to reach the CPU or other desired location.

Cold side axial fan 106 is powered by a DC output 107 from power supply 74.

A hot air fan 110 for pushing hot air out of cooling system 50 is mounted inside the housing adjacent side cover ventilation slots 84 near control unit 80. Hot air fan 110 serves to pull ambient air from or through the cooling system power supply ventilation slots 82 to partially cool the power supply 74 and control unit 80 of the cooling system, as well as to push out heated air from the thermoelectric cooler unit 90. A cold side/hot side barrier 112 is provided to prevent the flow of ambient air over the cold side of the thermoelectric cooler unit.

One or more hot air intake fans 114 are mounted inside the housing of cooling system 50 adjacent ventilation slots 62 for ambient air intake through front panel 52.

Ambient air passes through the hot side heat sink and leaves the system through ventilation slots 84, partially directly, and partially pulled out by fan 110. A cold air intake 116 is provided for cold air returning from the computer for additional cooling.

Operation of the cooling system of the present invention is as follows. After the cooling system has been arranged adjacent the computer enclosure to be cooled, with cold air outlet 108 adjacent the computer CPU or in any other selected location, the cooling system is switched on via switch 70. Preferably, the computer has been substantially sealed, so as to permit control of circulation within the enclosure. When the computer enclosure is substantially sealed, no ambient air can enter except via the TEC cooling system.

The temperature inside the computer is measured by a temperature sensor 61 (Fig. 4b), which can be inserted via an aperture 43 (seen in Fig. 5), so that it senses the temperature inside the enclosure. The temperature sensor is connected via connector 83 to control unit 80. If the temperature is above a predetermined threshold, control unit 80 activates hot air output fan 110 and hot air intake fan 114, as well as cold side axial fan 106. Between them, these fans create circulation through the computer enclosure, around the computer CPU, and through the cooling system, itself. Thus, it will be appreciated that there are two"circles", one from cold

air outlet 108 into the computer and out again through air intake 116 from the computer over cold side heat sink and back to the computer ; and the other, ambient air in from the side and front panels, over the hot side heat sink, and over the power supply and control unit, and out through side panel 84.

When voltage is applied across TEC's 94, heat is transferred from the cold side to the hot side. Thus, hot air from the computer entering air intake 116 and flowing over cold side heat sink 110 is cooled, and the heat therefrom is transferred, by the Peltier effect, to the hot side heat sink.

Operation of the control unit is illustrated in Fig. 5. A temperature sensor is mounted in the computer, preferably closest to the area which requires the most cooling, and coupled via connector 83 to the control unit to provide a signal corresponding to the sensed temperature (block 120). An operator inputs a desired temperature to be maintained by the cooling system (block 122), such as via a manually adjustable signal generator (block 124). This can be accomplished by means of an adjustable signal generating circuit for generating a set point signal having a manually adjustable magnitude within a predetermined range, the set point signal being representative of a desired temperature of the computer. A first fixed signal generating circuit 126 is provided for generating a reference signal having a predetermined magnitude to be sent to the control unit. The second fixed signal generating circuit 128 generates a reference signal having a predetermined magnitude, which permits the control unit to determine when to operate second relay 138 in order to switch from cooling to heating of the computer.

A first comparator or other comparison device compares the magnitudes associated with the set point signal (the temperature input by the operator by the manually adjustable signal generator) and the output signal generated by temperature sensing apparatus inside the enclosure (block 130). The first comparison device generates an output signal having a first voltage level when the magnitude of output voltage of the temperature sensing apparatus is greater than or equal to the magnitude of the set point signal. The generated output signal has a second voltage

level when the magnitude of the output voltage of the temperature sensing apparatus is less than the magnitude of the set point signal.

A second comparator or other comparison device compares the magnitudes associated with the first reference signal (the output of the first fixed signal generator) and the set point signal (input temperature) (block 132). The second comparison device generates an output signal having a first voltage level when the magnitude of the set point signal is greater than or equal to the magnitude of the first reference signal, and having a second voltage level when the set point signal is less than the first reference signal.

A third comparator or other comparison device compares the magnitudes associated with the second fixed reference signal (the output of the second fixed signal generator) and the output signal generated by the temperature sensing apparatus (block 134). The third comparison device generates an output signal having a first voltage level when the magnitude of the second reference signal is less than the output signal generated by the temperatures sensing apparatus, and having a second voltage level when the magnitude of the second reference signal is greater than or equal to the output signal generated by the temperature sensing apparatus.

In accordance with the results of the three comparators, the temperature inside the computer enclosure will be lowered, raised, or left unchanged. This is accomplished by means of the TECs 94 as follows. Each TEC 94 is coupled via a first relay 136 and a second relay 138 to a switching device 140 which, in turn, is coupled to comparators 130, 132 and 134. When the sensed temperature equals the input temperature (i. e., the output signals of the first comparator or the second comparator or the third comparator are at the second voltage level), all circuits remain open, and TEC 94 does not operate.

The switching device 140 is responsive to the output signals of the first, second and third comparators, and allows a flow of current therethrough when the output signals of all three comparators are at the high voltage level. The switching device blocks the flow of current therethrough when the output signal of any of the three comparison devices is at the low voltage level. The first relay has a coil

operatively connected to the switching device, a relay contact switch operatively connected to the TECs, and a relay contact switch having a normally open position and a closed position with respect to the switching device. The first relay contact switch is in the normally open position when the switching device blocks current flow, and is in the closed position when the switching device allows current flow.

The second relay has a coil operatively connected to the third comparator, a second relay contact switch operatively connected to the TECs, and a second relay contact switch having a normally open position and a closed position with respect to the output of the third comparator. The second relay contact switch is in the normally open position when the third comparator allows current flow, and in the closed position when the third comparator blocks current flow.

When the temperature inside the computer rises above the preset temperature maximum, switching device 140 activates relay 136 (relay 138 is not activated) so as to activate TEC 94 with the cold side adjacent the computer and the hot side adjacent the air output of the cooling system, thereby cooling the computer enclosure. Thus, a variable or constant electrical charge (volts or amperes) is applied in a first direction to the TECs, based upon the voltage levels associated with the first, second and third output signals.

On the other hand, in the event that the sensed temperature falls below an input minimum, switching device 140 activates relay 138 (relay 136 is not activated), so as to activate TEC 94 with the hot side adjacent the computer and the cold side adjacent the air output of the cooling system, thereby pumping the heat in the opposite direction, and warming the computer enclosure. In other words, a variable or constant electrical charge (volts or amperes) is applied in a second direction to the TECs based upon the voltage levels associated with the third output signal.

Referring now to Figs. 6, 7a, 7b and 7c, there are shown respective plan, top, side, and front views of a cooling system 120 constructed and operative in accordance with a preferred embodiment of the invention. In this embodiment, the cooling system includes a thermoelectric cooler unit 122 mounted adjacent the computer enclosure 124 to be cooled and a PCI card 126, seated in a PCI card slot in

the computer enclosure, which serves to deliver the cooled air to the inside of the enclosure. Thermoelectric cooler unit 122 provides cooled air by a flexible pipe 128 to PCI card 126 in the card slot.

Thermoelectric cooler unit 122 includes one or more thermoelectric cooler modules (TEC) as described above with reference to Fig. 3. All the cold air from the cold side of the TECs flows out cold air outlet 132 through flexible pipe 128.

Flexible pipe 128 merges into a plug 130, which is coupled to a special bracket 134, shown in detail in Fig. 7c. Bracket 134 includes an inlet socket 136 with a plastic adapter 138 into which plug 130 of flexible pipe 128 is plugged. Bracket 134 also includes a plurality of hot air outlets 140.

PCI card 126 is a simple card with vents having fans 142, 144 on each side.

The card is divided into two halves by a separator 146 (i. e., plastic and/or insulation), so cold air circulation is separate from hot air circulation. The cold air is pushed by the cooling unit and sucked by the card fan 144 and delivered to the inside of the PC.

The hot air is sucked by vent 142 out from the PC via hot air outlets 140. PCI card 126 is installed or inserted into a standard PCI slot inside the PC, as by a small printed circuit board 128 attached to the card. The printed circuit board can be attached by screws through the plastic card, or in any other fashion. The printed circuit board 148 has conductors to the PCI bus to the +12 volt power source. This voltage is fed via connectors 150, 152 to the vent fans 142 and 144 as operating voltage. In this way, card fan power is taken from the PC power source via PCI slot, so the card does not need an external voltage. An indicator 154, such as an LED, can be provided on bracket 134 to indicate when the fan is on or when the card is installed correctly.

It will be appreciated that PCI card 126 can suck in ambient air for simple cooling, and not only cold air from the cooling unit. In addition, instead of providing fans on the PCI card, it is possible to provide an external cooling unit pushing cold air via the card in the PCI slot.

With reference to Fig. 8, there is shown a plan view of a cooling system for a computer enclosure 160 constructed and operative in accordance with yet another

embodiment of the invention. This embodiment is similar to that of Fig. 6, wherein the air is cooled in a separate thermoelectric cooler unit (not shown) which provides cooled air by a flexible pipe 162 to enclosure 160. In this embodiment, the cooled air is drawn through the power supply of the computer via the computer's power supply fan. Flexible pipe 162 is coupled, as by a ring 163, to an adapter 164, which includes an air flow passage 166 and an optional air intake pipe 168. Adapter 164 can be formed of plastic, or any other suitable material. Preferably, adapter 164 also includes two screw holes 170 for attaching the pipe and adapter to a rear plate 172 of the computer power supply using the computer power supply screws. In this way, cooled air flows through the cooling vents 174 of the power supply plate, through the power supply, and into the computer enclosure. Thus, this embodiment permits cooling of any conventional computer enclosure without requiring modification of the computer enclosure, merely by plugging in the adapter. However, it will be appreciated that the pull fan in the enclosure must be turned down or turned off, so that all the cold air which flows in is not immediately pulled out.

It will be appreciated that the cooling system of the present invention can improve performance and reliability of computer and other heat sensitive components by allowing PCU speed, and therefore heat, to increase, without damaging any heat sensitive components.

It will be appreciated that the invention is not limited to what has been described hereinabove merely by way of example. Rather, the invention is limited solely by the claims which follow.