Thermoelectric cooling system and method

• US 4,639,883 A
• Filed: 11/28/1984
• Issued: 01/27/1987
• Est. Priority Date: 11/28/1984
• Status: Expired due to Term

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: RCA Corporation
• Inventors: Michaelis, Theodore D.
• Primary Examiner(s): Gruber, Felix D.
• Assistant Examiner(s): Juffernbruch, Daniel W.
• Application Number:
  US06/675,779
• Time in Patent Office: 790 Days
• Field of Search: 364/557, 322/2 R, 374/179, 374/180, 374/182, 374/170, 62/3, 136/201, 136/203, 73/338
• US Class Current: 700/300
• CPC Class Codes: F25B 21/02 using Peltier effect; using Nernst-Ettinghausen effect
• CPC Class Codes: F25B 2321/021 Control thereof
• CPC Class Codes: G05D 23/1919 characterised by the type of controller

Abstract

A temperature-controlled thermoelectric cooling system regulates the flow of electric current into the thermoelectric cooler in order to maintain a desired cold-side temperature without directly measuring the temperature of the device affixed to the cold side of the cooler. The system includes an apparatus for periodically interrupting the current flowing to the cooler, and during these interruptions measuring the open circuit voltage across the cooler induced by the temperature difference between the hot and cold sides. Computational means use this voltage measurement in conjunction with the temperature of the hot side of the cooler to determine the cold side temperature. From the cold side temperature determination, a controller regulates the current flow to the cooler to maintain a desired cold side temperature.

Claims

1. An apparatus for determining the temperature of the cold side of a thermoelectric cooler, said cooler having terminals adapted to receive electric current therethrough, said apparatus comprising:

means for interrupting said electric current to said thermoelectric cooler;

means for detecting the voltage induced across said terminals during said interruption;

means for sensing the temperature of the hot side of said thermoelectric cooler; and

means responsive to said sensing means and said detecting means for computing the temperature of said cold side of said thermoelectric cooler.

2. The apparatus according to claim 1 in which said computing means computes the temperature of said cold side according to

3. The apparatus according to claim 2 in which said computing means computes the temperature of said cold side using a Seebeck coefficient which is a function of T_C, and wherein said computing means iteratively computes a value of T_C using a Seebeck coefficient which is a function of the immediately preceding computed value of T_C.

4. The apparatus according to claim 3 in which said computing means iteratively computes values of T_C until the difference between a computed value of T_C and the immediately preceding computed value of T_C is less than a predetermined value.

5. The apparatus according to claim 1 in which said means for interrupting interrupts said electric current for ten microseconds.

6. The apparatus according to claim 1 in which said detecting means comprising a sample and hold circuit.

7. The apparatus according to claim 1 in which said sensing means includes a thermocouple.

8. A thermoelectric cooling system including:

means for providing electric current;

a thermoelectric cooler having a cold side and a hot side and having terminals for receiving said electric current therethrough, said electric current being applied to said terminals such that said current flows through said thermoelectric cooler in a direction so as to maintain said cold side at a temperature lower than said hot side, said thermoelectric cooler being adapted to be affixed at its cold side to a workpiece;

means for sensing the temperature at said hot side of said thermoelectric cooler;

means for periodically interrupting said electric current supplied to said thermoelectric cooler;

means for detecting the voltage across said terminals during said interruptions, said voltage being induced by the difference in temperature between hot side and said cold side;

means responsive to said sensing means and to said detecting means for computing the temperature of said cold side of said thermoelectric cooler; and

means coupled to said source of electric current and responsive to said computing means for controlling said flow of electric current.

9. The system according to claim 8 in which said computing means computes the temperature of said cold side according to

10. The system according to claim 9 in which said computing means computes the temperature of said cold side using a Seebeck coefficient which is a function of T_C, and wherein said computing means iteratively computes a value of T_C using a Seebeck coefficient which is a function of the immediately preceding computed value of T_C.

11. The system according to claim 10 in which said computing means iteratively computes values of T_C until the difference between a computed value of T_C and the immediately preceding computed value of T_C is less than a predetermined value.

12. The system according to claim 8 in which said means for interrupting interrupts said electric current for ten microseconds.

13. The system according to claim 8 in which said detecting means comprises a sample and hold circuit.

14. The system according to claim 8 in which said sensing means includes a thermocouple.

15. A method for determining the temperature of the cold side of a thermoelectric cooler having electric current supplied through terminals thereof, said method comprising the steps of:

a. interrupting said electric current to said thermoelectric cooler;

b. detecting the voltage induced across said terminals during said interruption;

c. sensing the temperature of the hot side of said thermoelectric cooler; and

d. computing the temperature of said cold side of said thermoelectric cooler from said detected voltage and said sensed hot side temperature.

16. The method according to claim 15 in which the temperature of said cold side is computed during said computing step according to

17. The method according to claim 16 in which the temperature of said cold side is computed during said computing step using a Seebeck coefficient which is a function of T_C, and wherein said computing step iteratively computes a value of T_C using a Seebeck coefficient which is a function of the immediately preceding computed value of T_C.

18. The method according to claim 17 in which said computing step iteratively computes values of T_C until the difference between a computed value of T_C and the immediately preceding computed value of T_C is less than a predetermined value.

19. A method for controlling the temperature of the cold side of a thermoelectric cooler comprising the steps of:

a. supplying electric current through terminals of said thermoelectric cooler;

b. periodically interrupting said electric current to said thermoelectric cooler;

c. detecting the voltage induced across said terminals during said interruption;

d. sensing the temperature of the hot side of said thermoelectric cooler;

e. computing the temperature of said cold side of said thermoelectric cooler from said detected voltage and said sensed hot side temperature;

f. comparing said computed cold side temperature with a reference temperature; and

g. controlling said electric current supplied to said thermoelectric cooler in response to said comparison.

20. The method according to claim 19 in which the temperature of said cold side is computed during said computing step according to

21. The method according to claim 20 in which the temperature of said cold side is computed during said computing step using a Seebeck coefficient which is a function of T_C, and wherein said computing step iteratively computes a value of T_C using a Seebeck coefficient which is a function of the immediately preceding computed value of T_C.

22. The method according to claim 21 in which said computing step iteratively computes values of T_C until the difference between a computed value of T_C and the immediately preceding computed value of T_C is less than a predetermined value.