U.S. patent application number 11/336951 was filed with the patent office on 2007-07-19 for temperature control system.
This patent application is currently assigned to BOOKHAM TECHNOLOGY, PLC.. Invention is credited to Joseph Barnard, Qi Pan.
Application Number | 20070163271 11/336951 |
Document ID | / |
Family ID | 35998066 |
Filed Date | 2007-07-19 |
United States Patent
Application |
20070163271 |
Kind Code |
A1 |
Pan; Qi ; et al. |
July 19, 2007 |
Temperature control system
Abstract
A system including: (i) a semiconductor device; (ii) a
thermoelectric controller for controlling the temperature of the
semiconductor device; (iii) an electrical power supply for powering
the thermoelectric controller; (iv) a first device capable of
determining both a direction and a magnitude of current through the
thermoelectric controller; (v) a second device also capable of
determining a magnitude of current through the thermoelectric
controller; and (vi) a controller for controlling the first and
second devices on the basis of an electrical indicator of the
temperature of the semiconductor device so as to achieve a desired
direction and magnitude of current through the thermoelectric
controller at a level of power consumption lower than could be
achieved using the first device alone.
Inventors: |
Pan; Qi; (Didcot, GB)
; Barnard; Joseph; (London, GB) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W., SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
BOOKHAM TECHNOLOGY, PLC.
|
Family ID: |
35998066 |
Appl. No.: |
11/336951 |
Filed: |
January 23, 2006 |
Current U.S.
Class: |
62/3.7 ;
257/E23.082 |
Current CPC
Class: |
F25B 21/02 20130101;
H01L 23/38 20130101; F25B 2321/0212 20130101; H01S 5/02415
20130101; H01L 2924/00 20130101; H01L 2924/0002 20130101; H01L
2924/0002 20130101 |
Class at
Publication: |
62/3.7 |
International
Class: |
F25B 21/02 20060101
F25B021/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 16, 2006 |
GB |
0600766.0 |
Claims
1. A system including: (i) a semiconductor device; (ii) a
thermoelectric controller for controlling the temperature of the
semiconductor device; (iii) an electrical power supply for powering
the thermoelectric controller; (iv) a first device capable of
determining both a direction and a magnitude of current through the
thermoelectric controller; (v) a second device also capable of
determining a magnitude of current through the thermoelectric
controller; and (vi) a controller for controlling the first and
second devices on the basis of an electrical indicator of the
temperature of the semiconductor device so as to achieve a desired
direction and magnitude of current through the thermoelectric
controller at a level of power consumption lower than could be
achieved using the first device alone.
2. A system according to claim 1, wherein the semiconductor device
is a laser.
3. A system according to claim 1, wherein the second device is a
DC-DC converter.
4. A system according claim 1, wherein the first device comprises
first, second, third and fourth transistors; said first and second
transistors are connected in parallel to the power supply in
parallel with the third and fourth transistors; and wherein the
first and third transistors are connected in series to the
thermoelectric controller and the second and fourth transistors are
also connected in series to the thermoelectric controller.
5. A system according to claim 4, wherein the controller is a
microprocessor and controls the second device and the first,
second, third and fourth transistors via respective
digital-analogue converters.
6. A method for controlling the temperature of a semiconductor
device using a thermoelectric controller, using a first device
capable of determining both a magnitude and a direction of current
through the thermoelectric controller; the method including the
steps of providing a second device also capable of determining a
magnitude of current through the thermoelectric controller, and
controlling the first and second devices to achieve a desired
direction and magnitude of current through the thermoelectric
controller at a level of electric power consumption lower than
could be achieved using the first device alone.
7. A system including: (i) a semiconductor device; (ii) a
thermoelectric controller for controlling the temperature of the
semiconductor device; (iii) an electrical power supply for powering
the thermoelectric controller; (iv) a first device capable of
determining the direction of current through the thermoelectric
controller; (v) a second device separate from the first device and
capable of determining a magnitude of current through the
thermoelectric controller; and a controller for controlling the
first and second devices on the basis of an electrical indicator of
the temperature of the semiconductor device.
8. A controller for controlling the temperature of a semiconductor
device using a thermoelectric controller, wherein said controller
is arranged to control a first device capable of determining both a
magnitude and a direction of current through the thermoelectric
controller and a second device also capable of determining a
magnitude of current through the thermoelectric controller, on the
basis of an electrical indicator of the temperature of the
semiconductor device so as to achieve a desired direction and
magnitude of current through the thermoelectric controller at a
level of power consumption lower than could be achieved using the
first device alone.
9. An electronic circuit for controlling the temperature of a
semiconductor device using a thermoelectric controller, the
electronic circuit including: a first device capable of determining
both a direction and a magnitude of current through the
thermoelectric controller; a second device also capable of
determining a magnitude of current through the thermoelectric
controller; and a controller for controlling the first and second
devices on the basis of an electrical indicator of the temperature
of the semiconductor device so as to achieve a desired direction
and magnitude of current through the thermoelectric controller at a
level of power consumption lower than could be achieved using the
first device alone.
10. A computer program product comprising program code means which
when loaded into a computer controls the computer to carry out the
method step of claim 6 of controlling the first and second devices
to achieve a desired direction and magnitude of current through the
thermoelectric controller at a level of electric power consumption
lower than could be achieved using the first device alone.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a technique for controlling
the temperature of a device, particularly a laser.
BACKGROUND OF THE INVENTION
[0002] Laser diodes are widely used for optical communications.
However, the optical output properties of laser diodes can be
dependent on temperature, and to maintain a stable optical output
the temperature of the laser may need to be regulated.
Thermoelectric coolers (also known as Peltier devices) are often
used to regulate the temperature of laser diodes. A thermoelectric
cooler (TEC) is a solid state heat-pump, whereby, when a current is
passed through the TEC, heat is transferred from one side of the
TEC to the other, producing a cold side and a hot side. A component
such as a laser diode mounted on the cold side can therefore have
heat transferred away from it to the hot side, from where it can be
dissipated. In addition to being used as coolers, TECs can also be
used to heat a component by reversing the direction of the current
through the TEC. A TEC is therefore useful in applications where a
temperature must be maintained, as can be the case with laser
diodes.
[0003] In order to maintain a temperature, the TEC current needs to
be controlled. In particular, the direction of the current must to
be controlled in order to determine the direction of heat transfer,
and the magnitude of the current must be controlled in order to
determine the rate of the heat transfer.
[0004] A known TEC control system 100 for controlling the
temperature of a laser diode is shown in FIG. 1. The system 100
controls the operation of a TEC 102 using an H-bridge circuit
comprising four MOSFETs (104, 106, 108, 110). The H-bridge allows
the direction of the current through the TEC 102 to be controlled.
For example, if MOSFETs 104 and 110 are "switched on" (i.e. in a
conducting state) and MOSFETs 106 and 108 are "switched off" (i.e.
non-conducting), then current can flow from a fixed input voltage
VIN 112, through the TEC via MOSFET 104 and 110 to ground.
Therefore, the current flows from left to right through the TEC as
seen in FIG. 1. Alternatively, if MOSFETs 106 and 108 are switched
on and MOSFETs 104 and 110 are switched off, then the current flows
from right to left through the TEC, as seen in FIG. 1. Therefore,
by controlling the MOSFETs in the H-bridge, the direction of
current through the TEC can be controlled.
[0005] The system 100 utilizes a temperature sensor 114 mounted on
the side of the TEC on which the laser diode 124 is mounted to
monitor the temperature of the TEC 102. The signal indicative of
the temperature of the laser diode produced by the temperature
sensor 114 is converted to digital data by an analogue to digital
converter 116. The digital signal indicative of the temperature of
the TEC 102 is then input to a microprocessor 118. The
microprocessor 118 uses this reading of the TEC temperature to
control the currents through the TEC 102, in order to maintain the
temperature. The microprocessor 118 controls the current through
the TEC 102 by using digital to analogue converters (DACs) 120, 122
to control the MOSFETs of the H-bridge. The microprocessor 118
provides a digital signal to the DACs 120 and 122, which convert
this to an analogue voltage level that is applied to the gate
terminal of the MOSFETs. The magnitude of the analogue voltage
level controls the extent to which the MOSFETs are switched on. A
voltage applied to the gate of the MOSFET that is lower than the
voltage required to switch the MOSFET to full conduction will allow
the MOSFET to conduct, but it will have a resistance related to the
value of the gate voltage. Hence, the MOSFETs are controlled to
provide variable levels of resistance, and thereby control the
magnitude as well as the direction of the current through the TEC
102.
[0006] The MOSFETs in the H-bridge are arranged such that MOSFETs
104 and 106 are N-channel MOSFETs (NMOS) and MOSFETs 108 and 110
are P-channel MOSFETs (PMOS). By utilising this configuration, the
H-bridge can be controlled with two signals from the
microprocessor, as the same signal can be applied to the gates of
an N-channel and P-channel MOSFET. A signal to activate the
N-channel MOSFET will correspondingly deactivate the P-channel
MOSFET and vice versa. Therefore, when the signal from the DAC 120
or 122 is such that N-channel MOSFET 104 or 106 is activated,
P-channel MOSFET 108 or 110 is deactivated. Similarly, when the
signal from the DAC 120 or 122 is such that P-channel MOSFET 108 or
110 is activated, N-channel MOSFET 104 or 106 is deactivated, as is
required to operate the H-bridge.
SUMMARY OF THE INVENTION
[0007] It has been observed that there can be a problem with the
TEC control technique shown in FIG. 1. Because there can be
variation in the efficiency of individual TECs and also variation
in the thermal resistance between individual TECs and their
respective heat dissipating devices, such as heatsinks, the supply
voltage VIN 112 is generally set relatively high so as to be able
to provide the necessary rate of heat transfer even for the
worst-case scenario such as where both the efficiency and the
thermal resistance for the individual TEC are as poor as might be
expected and where the operating conditions are as severe as might
be expected. Accordingly, for individual TECs for which the
efficiency and/or thermal resistance is not so poor and/or where
the operating conditions are not at their severest, the MOSFETs
(104, 106, 108, 110) in the H-bridge are operated as resistive
elements in a partially-on state in order to limit the magnitude of
the current through the TEC, and as a consequence of such operation
dissipate relatively large amounts of power.
[0008] The power dissipated in the MOSFETs leads to an increase in
the temperature of the substrate under the TEC, thereby making it
more difficult for the TEC to cool the thermal load. Furthermore,
the power dissipated in the MOSFETs also increases the overall
power dissipation for a module comprising the TEC control system of
FIG. 1, which can be an important factor in low-power systems.
[0009] It is an aim of the present invention to provide a new type
of TEC control, which can at least alleviate this problem.
[0010] According to one aspect of the present invention, there is
provided a system including: (i) a semiconductor device; (ii) a
thermoelectric controller for controlling the temperature of the
semiconductor device; (iii) an electrical power supply for powering
the thermoelectric controller; (iv) a first device capable of
determining both a direction and a magnitude of current through the
thermoelectric controller; (v) a second device also capable of
determining a magnitude of current through the thermoelectric
controller; and (vi) a controller for controlling the first and
second devices on the basis of an electrical indicator of the
temperature of the semiconductor device so as to achieve a desired
direction and magnitude of current through the thermoelectric
controller at a level of power consumption lower than could be
achieved using the first device alone.
[0011] In a preferred embodiment, the semiconductor device is a
laser.
[0012] In one embodiment, the second device is a DC-DC
converter.
[0013] In one embodiment, the first device comprises first, second,
third and fourth transistors; said first and second transistors are
connected in parallel to the power supply in parallel with the
third and fourth transistors; and wherein the first and third
transistors are connected in series to the thermoelectric
controller and the second and fourth transistors are also connected
in series to the thermoelectric controller.
[0014] In one embodiment, the controller is a microprocessor and
controls the second device and the first, second, third and fourth
transistors via respective digital-analogue converters.
[0015] According to another aspect of the present invention, there
is provided a method for controlling the temperature of a
semiconductor device using a thermoelectric controller, using a
first device capable of determining both a magnitude and a
direction of current through the thermoelectric controller; the
method including the steps of providing a second device also
capable of determining a magnitude of current through the
thermoelectric controller, and controlling the first and second
devices to achieve a desired direction and magnitude of current
through the thermoelectric controller at a level of electric power
consumption lower than could be achieved using the first device
alone.
[0016] According to another aspect of the present invention, there
is provided a system including: (i) a semiconductor device; (ii) a
thermoelectric controller for controlling the temperature of the
semiconductor device; (iii) an electrical power supply for powering
the thermoelectric controller; (iv) a first device capable of
determining the direction of current through the thermoelectric
controller; (v) a second device separate from the first device and
capable of determining a magnitude of current through the
thermoelectric controller; and a controller for controlling the
first and second devices on the basis of an electrical indicator of
the temperature of the semiconductor device.
[0017] According to another aspect of the present invention, there
is provided a controller for controlling the temperature of a
semiconductor device using a thermoelectric controller, wherein
said controller is arranged to control a first device capable of
determining both a magnitude and a direction of current through the
thermoelectric controller and a second device also capable of
determining a magnitude of current through the thermoelectric
controller, on the basis of an electrical indicator of the
temperature of the semiconductor device so as to achieve a desired
direction and magnitude of current through the thermoelectric
controller at a level of power consumption lower than could be
achieved using the first device alone.
[0018] According to another aspect of the present invention, there
is provided an electronic circuit for controlling the temperature
of a semiconductor device using a thermoelectric controller, the
electronic circuit including: a first device capable of determining
both a direction and a magnitude of current through the
thermoelectric controller; a second device also capable of
determining a magnitude of current through the thermoelectric
controller; and a controller for controlling the first and second
devices on the basis of an electrical indicator of the temperature
of the semiconductor device so as to achieve a desired direction
and magnitude of current through the thermoelectric controller at a
level of power consumption lower than could be achieved using the
first device alone.
[0019] According to another aspect of the present invention, there
is provided a computer program product comprising program code
means which when loaded into a computer controls the computer to
carry out the method step of claim 5 of controlling the first and
second devices to achieve a desired direction and magnitude of
current through the thermoelectric controller at a level of
electric power consumption lower than could be achieved using the
first device alone.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] For a better understanding of the present invention and to
show how the same may be put into effect, reference will now be
made, by way of example, to the following drawings in which:
[0021] FIG. 1 shows a known TEC control system; and
[0022] FIG. 2 shows a laser system according to an embodiment of
the present invention.
DESCRIPTION OF PREFERRED EMBODIMENT
[0023] Reference will first be made to FIG. 2, in which is shown a
laser system 200 according to an embodiment of the present
invention. The laser system 200 comprises a TEC 102, an H-bridge
comprising four MOSFETs (104, 106, 108, 110), a microprocessor 118,
two DACs (120, 122) controlling the MOSFETs, and an ADC 116 reading
the value of the TEC temperature from a temperature sensor 114
mounted on the side of the TEC on which the laser diode 124 is
mounted.
[0024] The laser system 200 further comprises a DC-DC converter 202
and a further DAC 204. The DC-DC converter 202 is a high-efficiency
device, with an efficiency typically >90% and often produced as
an integrated circuit (IC). The DC-DC converter 202 takes as input
a DC voltage level (VIN 112 as shown in FIG. 2) and produces a DC
output voltage 206. The magnitude of the DC output voltage 206 can
be controlled by a control input to the DC-DC converter 202, such
that the voltage level applied to the control input of the DC-DC
converter 202 determines the voltage level of the DC output voltage
206. The voltage applied to the control input is provided by the
output of the DAC 204.
[0025] The system 200 shown in FIG. 2 operates as follows. The
microprocessor 118 receives an input signal from the temperature
sensor 114 via the ADC 116. In response to this input, the
microprocessor 118 determines the required direction and rate of
heat transfer for the TEC.
[0026] The microprocessor 118 determines a value for the supply
voltage 206 to provide the desired magnitude of current through the
TEC 102, and sends a digital signal to the DAC 204, which generates
a corresponding analogue voltage level. This analogue voltage level
is applied to the control input of the DC-DC converter. In response
to the control input voltage level, the DC-DC converter produces an
output voltage 206, which is applied to the H-bridge.
[0027] In order to control the direction of the current through the
TEC 102, the microprocessor 118 determines which MOSFETs of the
H-bridge need to be activated. Digital signals are sent to the DACs
120 and 122, which produce corresponding analogue voltage levels.
The output of the DAC 120 is applied to the gates of the MOSFETs
104 and 108, and the output of the DAC 122 is applied to the gates
of the MOSFETs 106 and 110. These signals switch the MOSFETs on or
off in order to set the direction of current through the TEC 102.
For a given gate signal from DAC 120, the NMOS 104 and the PMOS 108
will be in opposite on and off states, and likewise for a given
signal from DAC 122, the NMOS 106 and PMOS 110 will also be in
opposite on and off states.
[0028] Using the TEC control system 200 shown in FIG. 2, the supply
voltage 206 applied to the TEC 102 via the H-bridge is varied, and
hence the magnitude of the current through the TEC is controlled by
adapting the supply voltage, rather than relying on the MOSFETs for
doing so. As control of the supply voltage is used to determine the
magnitude of the current through the TEC, those MOSFETs that are
controlled to be "on" only need to be operated in a "fully on"
state. The "fully on" resistance of the MOSFETs is low, with a
typical NMOS "fully on" resistance of approximately 50 milliohms
("m.OMEGA.") and a typical PMOS "fully on" resistance of
approximately 200 m.OMEGA.. Therefore, very little power is
dissipated in the MOSFETs, thereby minimising the heat produced and
the power consumed.
[0029] Since the efficiency of the DC-DC converter 202 is very
high, this does not produce significant amounts of heat, and the
power consumed by the DC-DC converter 202 is substantially less
than that consumed by the MOSFETs in the known system shown in FIG.
1.
[0030] The DACs (120, 122, 204) and ADC 116 may be internal to the
microprocessor 118, or external devices. The DACs (120, 122)
controlling the MOSFETs (104, 106, 108, 110) must be able to
produce both a positive and negative voltage sufficient to fully
activate either the N-channel or P-channel MOSFETs in the
H-bridge.
[0031] If the DC-DC converter 202 has a minimum output voltage
greater than 0V (for example this may typically be 0.4V), then DACs
120 and 122 are also used to control the amount of the current
delivered to the TEC 102 in addition to controlling the
direction.
[0032] The applicant draws attention to the fact that the present
invention may include any feature or combination of features
disclosed herein either implicitly or explicitly or any
generalisation thereof, without limitation to the scope of any
definitions set out above. In view of the foregoing description it
will be evident to a person skilled in the art that various
modifications may be made within the scope of the invention.
* * * * *