US-12625017-B2 - Dual heat path temperature sensor

Abstract

A temperature sensing system includes absolute temperature sensor(s) and/or thermopiles that form concentric geometries and are uniform in height. In some examples, the temperature sensing system can determine internal body temperature and/or ambient temperature based at least on a thermal gradient associated with the inner thermopile, a thermal gradient associated with the outer thermopile, a lateral temperature difference between the inner and the outer thermopiles, and an absolute temperature. In some examples, the temperature sensing system can determine the internal body temperature and/or ambient temperature using at least four absolute temperature sensors forming a concentric structure.

Inventors

• Wanfeng Huang
• Hongling Chen
• Ali M. Amin
• James C. Clements

Assignees

• APPLE INC.

Dates

Publication Date

20260512

Application Date

20230714

Claims (20)

1. 1 . An electronic device, comprising: a thermal sensing system comprising: a sensing surface, wherein the sensing surface comprises an inner thermopile associated with a first heat path and an outer thermopile associated with a second heat path, wherein the inner thermopile is same in height as the outer thermopile, and wherein the inner thermopile and the outer thermopile form concentric geometries; and a first absolute temperature sensor configured to measure a first absolute temperature; and a processor communicatively coupled to the thermal sensing system and configured to compute an ambient temperature or body temperature using a first temperature gradient associated with the first heat path, a second temperature gradient associated with the second heat path, a lateral temperature difference between the inner thermopile and the outer thermopile, and the first absolute temperature.
2. 2 . The electronic device of claim 1 , wherein the processor is configured to compute the ambient temperature or the body temperature using the first temperature gradient associated with the first heat path, the second temperature gradient associated with the second heat path, and at least two absolute temperatures.
3. 3 . The electronic device of claim 1 , wherein the first absolute temperature sensor is configured to measure the first absolute temperature at a first surface of the inner thermopile, wherein the thermal sensing system comprises a second absolute temperature sensor configured to measure a second absolute temperature at a first surface of the outer thermopile.
4. 4 . The electronic device of claim 3 , wherein the processor is configured to compute the lateral temperature difference between the inner thermopile and the outer thermopile using the first absolute temperature and the second absolute temperature.
5. 5 . The electronic device of claim 1 , wherein the processor is configured to compute the lateral temperature difference between the inner thermopile and the outer thermopile using a surface thermopile disposed between the inner thermopile and the outer thermopile.
6. 6 . The electronic device of claim 1 , wherein the processor is configured to compute the ambient temperature using the first temperature gradient, the second temperature gradient, the lateral temperature difference between the inner thermopile and the outer thermopile, a first surface area of the first heat path exposed to the ambient temperature, a second surface area of the second heat path exposed to the ambient temperature, a first resistance associated with the first heat path, and a second resistance associated with the second heat path.
7. 7 . The electronic device of claim 1 , wherein the sensing surface comprises glass or a printed circuit board.
8. 8 . The electronic device of claim 1 , wherein the inner thermopile comprises a first set of metal fillings and the outer thermopile comprises a second set of metal fillings different from the first set of metal fillings.
9. 9 . The electronic device of claim 8 , wherein the first set of metal fillings comprises copper and constantan and the second set of metal fillings comprises chromel and constantan.
10. 10 . The electronic device of claim 1 , wherein the thermal sensing system comprises a passivation layer disposed on the sensing surface, wherein the passivation layer comprises epoxy, silicon nitride, glass, a polymer material, a ceramic material, a composite material, or any combination thereof.
11. 11 . The electronic device of claim 1 , wherein the thermal sensing system comprises a thermal insulation layer disposed a threshold distance from the outer thermopile.
12. 12 . The electronic device of claim 1 , wherein the concentric geometries comprise concentric cylinders.
13. 13 . A dual heat flux sensor, comprising: a sensing glass comprising an inner thermopile and an outer thermopile, wherein the inner thermopile and the outer thermopile are uniform in height and form concentric geometries; a plurality of vias in the sensing glass comprising a plurality of first vias from a first surface of the sensing glass to a second surface of the sensing glass and a plurality of second vias from the first surface of the sensing glass to the second surface of the sensing glass, wherein the inner thermopile is formed from a first set of conductive materials filling the plurality of first vias and the outer thermopile is formed from a second set of conductive materials filling the plurality of second vias; and sensing circuitry configured to measure a temperature gradient associated with the inner thermopile and a second temperature gradient associated with the outer thermopile.
14. 14 . The dual heat flux sensor of claim 13 , wherein a diameter of the dual heat flux sensor is at least 1.5 times greater than a diameter of the outer thermopile.
15. 15 . The dual heat flux sensor of claim 13 , wherein a diameter of the dual heat flux sensor is between 9 millimeters and 12 millimeters.
16. 16 . The dual heat flux sensor of claim 13 , wherein a height of the dual heat flux sensor is less than 4 millimeters.
17. 17 . The dual heat flux sensor of claim 13 , wherein the dual heat flux sensor comprises a housing coupled to the sensing glass, wherein the housing comprises a cavity disposed beneath the sensing glass, and wherein the cavity comprises air.
18. 18 . The dual heat flux sensor of claim 17 , wherein the cavity comprises a height between 0.5 millimeters and 2.5 millimeters.
19. 19 . The dual heat flux sensor of claim 13 , comprising a glass layer different from the sensing glass and disposed beneath the sensing glass.
20. 20 . A system, comprising: a first absolute temperature sensor configured to measure a first absolute temperature at a first surface of an inner thermopile; a second absolute temperature sensor configured to measure a second absolute temperature at a first surface of an outer thermopile, wherein the inner thermopile is same in height as the outer thermopile, and wherein the inner thermopile and the outer thermopile form concentric geometries; a third absolute temperature sensor configured to measure a third absolute temperature at a second surface of the inner thermopile; a fourth absolute temperature sensor configured to measure a fourth absolute temperature at a second surface of the outer thermopile; and a processor communicatively coupled to the first absolute temperature sensor, the second absolute temperature sensor, the third absolute temperature sensor, and the fourth absolute temperature sensor and configured to compute an ambient temperature or an internal body temperature using the first absolute temperature, the second absolute temperature, the third absolute temperature, and the fourth absolute temperature.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Application No. 63/371,820, filed Aug. 18, 2022, the content of which is incorporated herein by reference in its entirety for all purposes. FIELD OF THE DISCLOSURE This relates generally to temperature sensing systems and methods, and more particularly to temperature sensing systems and methods configured to measure internal body temperature and/or ambient temperature. BACKGROUND OF THE DISCLOSURE Many types of sensing devices, such as temperature sensors, are presently available in electronic devices to measure temperature or heat conditions. Electronic devices can include a wearable device to measure internal body temperature. Electronic devices can also measure ambient temperature. SUMMARY OF THE DISCLOSURE An electronic device, such as a wearable device, can leverage temperature gradient measurements from thermopiles to measure temperature inside or outside the electronic device. As described herein, a thermopile can include a series-connected thermocouples and output a voltage measurement that is directly proportional to a temperature gradient and/or heat flux. For example, the electronic device can include a temperature sensing system that includes at least two thermopiles, which form concentric geometries. In some examples, the temperature sensing system can include a step up in height (e.g., a height differential) between the at least two thermopiles. However, the step up in height can complicate integration within compact housing (e.g., within a smart watch) due to space considerations for the temperature sensing system. In some examples, an improved temperature sensing system (e.g., dual heat flux sensor) that is compact in design by including thermopiles with uniform height (e.g., no step up between thermopiles) that form concentric geometries. In some examples, the improved temperature sensing system can include thermopiles with a height difference that is less than a threshold height difference (e.g., less than a difference of 10, 100, or 1000 microns in height between thermopiles). For example, the temperature sensing system can include a sensing surface (e.g., a glass layer) embedded with thermopiles, such as an inner thermopile (e.g., first thermopile) and an outer thermopile (e.g., second thermopile). A respective thermopile is associated with a respective heat path based on a temperature gradient between a top surface of the respective thermopile and a bottom surface of the respective thermopile. For example, the inner thermopile and the outer thermopile can have different heat paths (e.g., temperature gradients). Temperature gradient measurements of the thermopiles (e.g., inner thermopile, outer thermopile) can be used for determining heat flux (e.g., through an electronic device), surface temperature of objects contacting housing of the electronic device (e.g., ambient temperature), body temperature of a user wearing the electronic device, and so forth. Processing circuitry of the temperature sensing system or processing circuitry of the electronic device (e.g., wearable device) can leverage temperature gradient measurements of the thermopiles to account for variances in thermal resistance of skin and/or air (e.g., amount of fat tissue, wind speed, humidity) to accurately determine ambient temperature and/or internal body temperature. In some examples, to accurately determine thermal resistance of skin and internal body temperature and/or thermal resistance of air and ambient temperature, the processing circuitry of the temperature sensing system or the processing circuitry of the electronic device can use a temperature gradient of the inner thermopile, a temperature gradient of the outer thermopile, a lateral temperature difference between the inner thermopile and the outer thermopile, an absolute temperature of at least one surface of the inner thermopile or the outer thermopile, surface area of a heat path associated with the inner thermopile exposed to skin and/or air, surface area of a heat path associated with the outer thermopile exposed to skin and/or air, and so forth as inputs. BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1A-1E illustrate example systems that can include a touch screen according to examples of the disclosure. FIG. 2 illustrates a block diagram of an example electronic device according to examples of the disclosure. FIG. 3 illustrates an example wearable device that includes an example temperature sensing system to measure thermal resistance of skin and internal body temperature according to examples of the disclosure. FIG. 4 illustrates an example wearable device that includes an example temperature sensing system to measure thermal resistance of air and ambient temperature according to examples of the disclosure. FIG. 5 illustrates a cross-section of an example temperature sensing system according to examples of the disclosure. FIG. 6 illustrates a cross-sectional side v