Anti-condensation control system

• US 8,250,873 B2
• Filed: 12/18/2008
• Issued: 08/28/2012
• Est. Priority Date: 10/03/2008
• Status: Active Grant

• Current Assignee: Anthony Incorporated (Dover Corporation)
• Original Assignee: Anthony Incorporated (Dover Corporation)
• Inventors: Yoon, Doo Eui, Artwohl, Paul
• Primary Examiner(s): Tyler, Cheryl J
• Assistant Examiner(s): Bradford, Jonathan
• Application Number:
  US12/337,981
• Publication Number:
  US 20100083672A1
• Time in Patent Office: 1,349 Days
• Field of Search: 621/28, 621/50, 622/48, 621/761
• US Class Current: 62/150
• CPC Class Codes: F25D 21/002 Defroster control
• CPC Class Codes: F25D 21/04 Preventing the formation of frost or condensate
• CPC Class Codes: F25D 2400/02 Refrigerators including a heater

Abstract

System and methods for providing anti-condensation system are disclosed. A relative humidity (RH) sensor signal from a sensor on or near a control surface is received. An AC power input is received. A phase of the AC power input is modulated at least partly in response to the sensor signal in such a manner that a phase-modulated AC power output provided to a heater is a) substantially constant at a first power level (P_1st) in a low RH region ranging from 0% RH to a first RH (RH₁), b) varying as a function of the sensor signal from P_1st to a second power level (P_2nd) in an intermediate RH region ranging from RH₁ to a second RH (RH₂), and c) substantially constant at P_2nd in a high RH region beginning at RH₂.

Claims

1. An anti-condensation control apparatus comprising:

a sensor circuit comprising a humidity sensor and configured to provide a sensor signal indicative of a relative humidity (RH) on or near a control surface; and

a control circuit comprising a phase control circuit configured to;

receive the sensor signal and a high-voltage AC power input, and

modulate a phase of the high-voltage AC power input at least partly in response to the sensor signal indicative of the RH on or near the control surface and without use of a temperature sensor, the phase control circuit configured to modulate the phase of the high-voltage AC power input in such a manner that a phase-modulated AC power output provided to a heater is;

a) substantially constant at a minimum power level (P_min) in a low RH region ranging from 0% RH to a first RH (RH₁),

b) linearly varying from P_min to a maximum power level (P_max) in an intermediate RH region ranging from RH₁ to a second RH (RH₂), and

c) substantially constant at P_max in a high RH region ranging from RH₂ to 100% RH,

wherein the phase control circuit does not comprise a digital logic circuit.

2. The apparatus of claim 1, wherein the control surface comprises a window of a refrigerator door.

3. The apparatus of claim 2, wherein the heater is disposed in a frame of the refrigerator door.

4. The apparatus of claim 1, wherein:

the sensor circuit comprises a plurality of sensor modules installed at a plurality of zones comprising a plurality of control surfaces and configured to provide a plurality of sensor signals; and

the control circuit comprises a plurality of phase-control modules and is configured to receive the plurality of sensor signals from the plurality of sensor modules, and provide a plurality of phase-modulated AC power outputs to a plurality of heaters installed in the vicinity of the plurality of control surfaces.

5. The apparatus of claim 1, wherein the humidity sensor comprises a resistance-type humidity sensor comprising two conductors installed in contact with the control surface, wherein a resistance across the two conductors changes as a function of RH.

6. The apparatus of claim 1, wherein the humidity sensor comprises a capacitance-type humidity sensor comprising two conductors installed in contact with the control surface, wherein a capacitance between the two conductors changes as a function of RH.

7. The apparatus of claim 1, wherein the sensor module further comprises a dew sensor configured to measure water condensation on or near the control surface.

8. The apparatus of claim 1, wherein the phase control circuit comprises a triode for alternating current (TRIAC) configured to phase module the high-voltage AC power.

9. The apparatus of claim 1, wherein the phase control circuit comprises one or more silicon-controlled rectifiers (SCRs) configured to phase module the high-voltage AC power.

10. The apparatus of claim 9, wherein the phase control circuit comprises at least two SCRs connected in an inverse parallel configuration.

11. The apparatus of claim 1, wherein the high-voltage AC power signal has an AC voltage whose RMS value is in a range between about 90 volts to about 500 volts.

12. The apparatus of claim 1, wherein the position of RH₁ and/or RH₂ is user-adjustable.

13. A method of preventing condensation anti condensation comprising:

receiving a relative humidity (RH) sensor signal from a sensor on or near a control surface;

receiving an AC power input;

modulating a phase of the AC power input at least partly in response to the sensor signal and without use of a temperature sensor, wherein the phase of the AC power input is modulated in such a manner that a phase-modulated AC power output provided to a heater is;

a) substantially constant at a first power level (P_1st) in a low RH region ranging from 0% RH to a first RH (RH₁),

b) varying as a function of the sensor signal from P_1st to a second power level (P_2nd) in an intermediate RH region ranging from RH₁ to a second RH (RH₂), and

c) substantially constant at P_2nd in a high RH region beginning at RH₂.

14. The method of claim 13, wherein the high RH region extends to 100% RH.

15. The method of claim 13, wherein the phase-modulated AC power output provided to the heater is substantially linearly varying from P_1st to P_2nd in the intermediate RH region ranging from RH₁ to RH₂.

16. The method of claim 13, wherein the act of modulating the phase is performed without a digital logic circuit.

17. The method of claim 13, wherein the position of RH₁ and/or RH₂ is user-adjustable.

18. The method of claim 13, wherein the control surface comprises a window of a refrigerator.

19. The method of claim 13, wherein the heater is disposed in a frame of a refrigerator door.

20. The method of claim 13, further comprising measuring water condensation on or near the control surface.

21. The method of claim 13, wherein the AC power input comprises an AC voltage whose RMS value is in a range between about 90 volts to about 500 volts.

22. The method of claim 13, further comprising:

receiving a condensation sensor signal from a condensation sensor configured to measure condensation formed on or near the control surface; and

modulating the phase of the AC power input such that the phase-modulated AC power output provided to the heater is at a maximum power level (P_max) when the condensation sensor signal indicates that condensation is formed on or near the control surface, wherein the P_max is greater than P_1st and P_2nd.

23. An anti-condensation control apparatus, the apparatus comprising:

a sensor module configured to measure a relative humidity (RH) and/or a water condensation on or near a control surface, and provide a sensor signal indicative of the RH and/or the water condensation;

a control module configured to receive the sensor signal and an AC power input, and provide a phase-modulated AC power output to a heater at least partly in response to the sensor signal and without using a temperature sensor, the control module comprising;

an alternating current (AC) switch configured to receive a phase-control input that triggers the AC switch to deliver the phase-modulated AC power output to the heater during a specified phase of the AC power input,

a first output control circuit configured to provide at least a portion of a first control voltage to the phase-control input to cause the AC switch to provide a first substantially constant phase-modulated AC power output to the heater in a low RH region,

a second output control circuit configured to provide at least a portion of a second control voltage to the phase-control input to cause the AC switch to provide a substantially linearly varying phase-modulated AC power output to the heater in an intermediate RH region, and

a third output control circuit configured to provide at least a portion of a third control voltage to the phase-control input to cause the AC switch to provide a second substantially constant phase-modulated AC power output to the heater in a high RH region.

24. The apparatus of claim 23, wherein the AC switch is a triode for alternating current (TRIAC) configured to phase modulate the high-voltage AC power input.

25. The apparatus of claim 23, wherein the sensor module is configured to measure the relative humidity (RH) and the water condensation on or near a control surface, and the control module is configured to provide a maximum phase-modulated AC power output to the heater when the sensor module indicates that condensation is formed on or near the control surface.