U.S. patent application number 09/780025 was filed with the patent office on 2001-10-18 for super cooler for a heat producing device.
Invention is credited to Evans, Nigel, Hewlett, William E..
Application Number | 20010029740 09/780025 |
Document ID | / |
Family ID | 22664673 |
Filed Date | 2001-10-18 |
United States Patent
Application |
20010029740 |
Kind Code |
A1 |
Evans, Nigel ; et
al. |
October 18, 2001 |
Super cooler for a heat producing device
Abstract
A super cooler device including a thermo electric cooler on a
digital micro mirror device.
Inventors: |
Evans, Nigel; (Sutton
Coldfield, GB) ; Hewlett, William E.; (Burton on
Trent, GB) |
Correspondence
Address: |
FISH & RICHARDSON, PC
4350 LA JOLLA VILLAGE DRIVE
SUITE 500
SAN DIEGO
CA
92122
US
|
Family ID: |
22664673 |
Appl. No.: |
09/780025 |
Filed: |
February 9, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60181530 |
Feb 10, 2000 |
|
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|
Current U.S.
Class: |
62/3.2 ;
348/E5.142; 348/E5.143; 62/259.2; 62/3.7 |
Current CPC
Class: |
H04N 9/3141 20130101;
H01L 35/00 20130101; H04N 5/7458 20130101; F25B 21/02 20130101;
G05D 23/1931 20130101; F25B 49/00 20130101; G02B 26/0841 20130101;
H04N 2005/7466 20130101; F21V 29/67 20150115; G02B 7/1815 20130101;
F21V 29/505 20150115; G05D 23/1919 20130101; F25B 2321/021
20130101 |
Class at
Publication: |
62/3.2 ; 62/3.7;
62/259.2 |
International
Class: |
F25B 021/02; F25D
023/12 |
Claims
What is claimed:
1. An apparatus, comprising: a temperature sensing device,
monitoring a front temperature of a front surface of a first driven
device, and a rear temperature related to a rear surface of the
first driven device; a controller, detecting both a temperature of
the first driven device and a temperature differential across the
first driven device; a thermoelectric cooler, coupled to actively
cool the first driven device under control of said controller; and
wherein said controller produces outputs which control both overall
temperature of the first driven device and temperature differential
of the first driven device.
2. An apparatus as in claim 1, wherein the first driven device is a
digital mirror device.
3. An apparatus as in claim 1, further comprising a lighting
projector, projecting light on said front surface of said first
driven device.
4. An apparatus as in claim 1, further comprising a pulse width
modulated device, driven by said controller, to produce a pulse
width modulated output to drive said thermoelectric cooler.
5. An apparatus as in claim 4, wherein said pulse width modulated
output is applied directly to said thermoelectric cooler.
6. An apparatus as in claim 4, further comprising a filter, which
filters said pulse width modulated output, to provide a smoothed
output.
7. An apparatus as in claim 1, further comprising a super cooler
assembly, connected to a hot side of said thermoelectric cooler,
said super cooler assembly including a metal plate, a heat sink,
connected to said metal plate, and a fan, actively cooling said
heat sink.
8. An apparatus as in claim 7, wherein said temperature sensing
device includes a sensor mounted to said metal plate.
9. An apparatus as in claim 7, further comprising insulation,
mounted to insulate portions of said first driven device, to
insulate said first driven device from ambient.
10. An apparatus as in claim 9, wherein said first driven device is
a digital mirror device.
11. An apparatus as in claim 7, wherein said heat sink has a
cross-sectional area which is substantially square, and an outer
frame of said fan is substantially square and coupled to said heat
sink.
12. An apparatus as in claim 11, wherein said heat sink has a
square cross-section, in a first direction, and has a rectangular
cross-section in a second direction.
13. An apparatus as in claim 6, wherein said filter includes an LC
filter.
14. An apparatus as in claim 1, wherein said controller monitors
overall temperature of the first driven device, a ratio between
front and rear temperature of the first driven device, and an
increment over time of cooling of the first driven device.
15. An apparatus as in claim 14, wherein the first driven device is
a digital mirror device.
16. An apparatus as in claim 2, further comprising insulation
between said digital mirror device and ambient.
17. An apparatus, comprising: a digital micro mirror device
assembly, including a mounting plate for a digital micro mirror
device, and a digital micro mirror device mounted on said mounting
plate; and insulation, positioned around at least a part of said
digital micro mirror device, to insulate said at least part of the
digital micro mirror device from ambient.
18. An apparatus as in claim 17, further comprising a
thermoelectric cooling device, coupled to cool said at least part
of the digital micro mirror device.
19. An apparatus as in claim 18, further comprising a controller
for said thermoelectric cooling device.
20. An apparatus as in claim 19, further comprising temperature
sensors on said digital micro mirror device, wherein said
controller is operative responsive to said temperature sensors, to
control at least one temperature of said digital micro mirror
device.
21. An apparatus as in claim 20, wherein said controller controls
production of a pulse width modulated signal, whose pulse width is
based on said temperature.
22. An apparatus, comprising: a digital micro mirror device
assembly, including a digital micro mirror device mounted thereon;
and an active cooling unit, coupled to cool said digital micro
mirror device.
23. An apparatus as in claim 22, wherein said active cooling unit
includes a thermoelectric cooler.
24. An apparatus as in claim 23, further comprising a temperature
sensor, sensing a temperature of said digital micro mirror device,
and a controller, controlling said thermoelectric cooler based on
the sensed temperature.
25. An apparatus as in claim 24, wherein said temperature sensor
includes a first temperature sensor sensing a temperature near the
front of the digital micro mirror device, and a second temperature
sensor sensing a temperature near the rear of the digital micro
mirror device.
26. An apparatus as in claim 25, wherein said controller operates
to control the thermoelectric cooler based on both the front
temperature, and a difference between the front and rear
temperatures.
27. An apparatus as in claim 22, further comprising a controller
for said active cooling unit, said controller controlling
production of a pulse width modulated signal that controls the
active cooling unit.
28. An apparatus as in claim 26, further comprising a controller
for said active cooling unit, said controller controlling
production of a pulse width modulated signal that controls the
active cooling unit.
29. An apparatus as in claim the 28, further comprising a filter
which smooths said pulse width modulated signal to reduce an amount
of transitions therein.
30. An apparatus as in claim 29, wherein said filter includes an LC
filter.
31. An apparatus as in claim 22, further comprising a plate formed
of heat distributing material, coupled to said digital micro mirror
device assembly and said active cooling unit, and of a size which
is affective to evenly distribute heat from the digital micro
mirror device assembly into said plate.
32. An apparatus as in claim 31, further comprising a temperature
sensor, sensing a temperature of said digital micro mirror device,
and a controller, controlling said thermoelectric cooler based on
the sensed temperature.
33. An apparatus as in claim 32, wherein said temperature sensor
includes a first temperature sensor, sensing a temperature near a
front of the digital micro mirror device, and a second temperature
sensor sensing a temperature of said plate, and wherein said
controller operates both on said front temperature, and based on a
difference between said front and said rear temperature.
34. As apparatus in claim 22, further comprising insulation coupled
between said digital micro mirror device and ambient, to insulate
said digital micro mirror device from ambient.
35. An apparatus as in claim 31, further comprising a heat sink and
fan, connected to said plate, to dissipate heat from said
plate.
36. A method, comprising: operating a digital micro mirror device
in an environment where one side thereof is exposed to heat from
light that is applied thereto; and actively cooling the other side
of said digital micro mirror device.
37. A method as in claim 36, wherein said actively cooling
comprises using a thermoelectric cooler coupled to an other side of
said digital micro mirror device.
38. A method as in claim 36, wherein said actively cooling
comprises using a pulse width modulated signal to control an amount
of cooling provided by said thermoelectric cooler.
39. A method as in claim 38, further comprising filtering said
pulse width modulated signal prior to applying said signal to said
thermoelectric cooler.
40. A method as in claim 36, further comprising detecting a
temperature of said digital micro mirror device, and wherein an
amount of said active cooling is based on the detected
temperature.
41. A method as in claim 40, wherein said detecting comprises
detecting a temperature of the front of the digital micro mirror
device and a temperature of the rear of the digital micro mirror
device.
42. A method as in claim 41, wherein said amount of active cooling
is based both on a temperature of the front of the device and on a
differential between the temperature of the front of the device and
a temperature of the rear of the device.
43. A method as in claim 36, further comprising: detecting a
temperature of the digital micro mirror device; detecting a
temperature near a rear of the digital micro mirror device;
determining a temperature of the digital micro mirror device, and a
difference between a temperature of the micro mirror device and a
rear temperature of the micro mirror device, and changing a cooling
amount based on both said temperature and said difference.
44. A method as in claim 43, further comprising determining a rate
of change of increment of temperature, and establishing a fault if
said rate of change is higher than a specified amount.
45. A method as in claim 36, further comprising insulating the
digital micro mirror device from ambient temperature.
46. A method, comprising: energizing a digital micro mirror device;
determining a first temperature related to a front of the digital
micro mirror device and a second temperature related to a rear
temperature of the digital micro mirror device; forming a pulse
width modulated control signal based on both temperature on the
front of the digital micro mirror device, and a difference between
temperature of the front and rear of the digital micro mirror
device; and actively cooling the rear of the digital micro mirror
device based on said pulse width modulated signal.
47. A method as in claim 46, further comprising filtering said
pulse width modulated signal, prior to said actively cooling.
48. A method as in claim 46, further comprising insulating said
digital micro mirror device from ambient temperature.
49. A method as in claim 46, further comprising dissipating heat
from the actively cooling using a heat sink and fan.
50. A method as in claim 46, wherein said forming comprises
establishing a desired temperature and a desired temperature
differential, and increasing and active amount of said pulse width
modulated signal when said desired temperature is exceeded, and
decreasing said active amount when said desired temperature
differential is exceeded.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims benefit of U.S. Provisional
Application No. 60/181,530 filed Feb. 10, 2000.
[0002] The present application relates to cooling of a heat
producing device, using a thermoelectric cooler arranged as a super
cooler. More specifically, the present application teaches cooling
of a device, such as a digital mirror device, which requires a
specified temperature gradient across the device, using a
supercooled element.
BACKGROUND
[0003] Electronic devices often have specified cooling
requirements. One device that has specific cooling requirements is
a digital micromirror device ("DMD") available from Texas
Instruments ("TI"). The manufacturer of this device has specified a
maximum overall temperature for the device and also a specified
maximum temperature gradient between the front and rear faces of
the device during operation.
[0004] For example, the temperature of the specific DMD used in
this application needs to be kept below 55.degree. C., however, in
this application it is desirable to keep the device at or below
ambient. This may allow operation in an ambient environment up to
55.degree. C., such as may be encountered in a stage theater or
studio environment. The temperature differential between the front
and rear of the DMD cannot exceed 15.degree.. Besides the heat from
the operation of the DMD itself, large amounts of heat from a high
intensity light source must be dissipated.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] These and other aspects will now be described in detail with
reference to the accompanying, wherein:
[0006] FIG. 1 shows an exploded diagram of the parts making up the
supercooler assembly;
[0007] FIG. 2 shows the rear of the DMD and parts which are
assembled to the DMD;
[0008] FIG. 3 shows a circuit for driving a thermoelectric cooler;
and
[0009] FIG. 4 shows a flowchart of operation.
DETAILED DESCRIPTION
[0010] According to the present system, a "supercooler" device, is
used to monitor and control the temperature of a device which can
control light on a pixel-by-pixel basis, e.g. a digital mirror
device (DMD).
[0011] The mechanical structure of the supercooling assembly is
shown in FIG. 1. The pixel element is a DMD 99, which forms part of
a DMD assembly 100. As shown, a thermal connection 105 to the DMD
99 is provided.
[0012] A cold plate 120 is assembled to a mounting bracket 110 in a
manner which allows minimal thermal transfer between the two
components. The DMD is attached directly to the cold plate 120,
hereby allowing maximum thermal transfer between the DMD and cold
plate 120, but minimal thermal transfer to the mounting bracket
110. The rear surface of the cold plate 120 is directly connected
to one side of the thermoelectric device 130, and the other side of
the thermoelectric device is connected to a heat sink/fan assembly
140.
[0013] Insulating foam gaskets are fitted around the DMD rear stud,
the cold plate, and the thermoelectric device in order to isolate
them from the outside ambient air. This improves the efficiency of
the cooling system by eliminating the effects of condensation and
properly controlling the flow of heat from the DMD to the cold
plate, through the thermoelectric device, and into the heat
sink/fan assembly.
[0014] The thermoelectric cooler element 130 operates as
conventional to produce one cold side 131 and one hot side 132. The
hot side is coupled to the heat sink/fan assembly 140 to dissipate
the heat. In a preferred mode, the heat sink/fan assembly is
columnar is shape, with a substantially square cross section. This
facilitates using a square shaped fan housing 142. The square
shaped fan unit allows the maximum use of the space for a fan,
whose blades usually follow a round shape. Any type of cooling fan,
however can be used.
[0015] The DMD assembly 100 has an extending rear stud 105 which is
covered with thermal grease. This stud extends though a hole 112 in
the bracket assembly 110.
[0016] The plate 120 is actively cooled, and hence becomes a "cold
plate". The active cooling keeps the metal plate at a cooled
temperature, and the thermal characteristics of the plate material
allow the heat flowing into the plate from the DMD to be evenly
distributed throughout the entire plate. The plate is preferably
about 1/4" to 3/8" in thickness, and of comparable outer size to
the thermal contact area of the thermoelectric cooler element 130.
This allows the localized and concentrated heat at the rear stud of
the DMD to be evenly dissipated through the cold plate and then
efficiently transferred through the full surface area of the
thermoelectric cooler element. As shown, the assembly employs
thermal insulation techniques such as fiber/plastic sleeves and
washers in the mounting of components, in order to prevent heat
transfer via mounting screws etc. Since this heat transfer could be
uncontrolled, it could otherwise reduce the cooling efficiency.
[0017] The front of the DMD is shown in FIG. 2. Temperature sensor
200 is mounted to have a fast response to temperature changes. A
second temperature sensor 122 is mounted to the cold plate 120 and
effectively measures the temperature of the rear of the DMD 99.
This second temperature sensor 122 therefore monitors the back
temperature.
[0018] The hot side 132 of the thermoelectric cooler is coupled to
a heat sink assembly 130. The heat sink assembly 140 includes a
heat sink element 140. As shown, the device has fins and a
top-located cooling fan 142.
[0019] A block diagram of the control system is shown in FIG. 3.
Controller 300 operates in a closed loop mode to maintain a desired
temperature differential across the sensors 122, 200.
[0020] One important feature of the present application is that the
thermoelectric cooler is controlled to maintain the temperature of
the DMD at the desired limits. These limits are set at a target of
16.degree. C. on the front, and a differential no greater than
15.degree. between front and rear. The thermoelectric cooler is
controlled using very low frequency or filtered pulse width
modulation. In a first embodiment, the controlling micro controller
300 produces an output 302, e.g., digital or analog. This drives a
pulse width modulator 304. The output of the pulse width modulator
is a square wave 306 or a signal close to a square wave, with
sufficient amplitude and power to produce the desired level of
cooling down the thermoelectric cooler. The square wave is coupled
to an LC filter 308 which has a time constant effective to smooth
the 20 KHz switching frequency. The output to the thermoelectric
cooler is therefore a DC signal. This drives the thermoelectric
cooler 130 and causes it to produce a cooling output. In a second
embodiment, the LC filter is removed and the TEC is driven directly
by the square wave 306 at a lower frequency, e.g. 1 Hz.
[0021] The microcontroller operates according to the flowchart of
FIG. 4. Step 400 determines if the temperature of the first
temperature sensor T1 is greater than 16.degree.. If so, the output
to the TEC remains "on", resulting in further cooling. When the
temperature falls below 16.degree., the drive to the TEC is
switched off. The sample period is approximately 1/2 second between
samples.
[0022] At 410, the system checks temperature of the first sensor
(T1) and of the second sensor (T2) to determine if the differential
is greater than 15.degree.. If so, the output is switched "on".
Step 420 indicates a limit alarm, which represents the time of
increase if the rate of change continues. If the rate of change
continues to increase, as detected at step 420, a fault is declared
at step 425. This fault can cause, for example, the entire unit to
be shut off, to reduce the power and prevent permanent damage.
[0023] Other embodiments are contemplated.
* * * * *