Thermographic sensor with thermal transistors driven by thermo-couples

Patent metadata

Field	Value
Publication number	US-12385788-B2
Application number	US-202117537074-A
Country	US
Kind code	B2
Filing date	Nov 29, 2021
Priority date	Nov 30, 2020
Publication date	Aug 12, 2025
Grant date	Aug 12, 2025

Abstract

A thermographic sensor is proposed. The thermographic sensor includes one or more thermo-couples, each for providing a sensing voltage depending on a difference between a temperature of a hot joint and a temperature of a cold joint of the thermo-couple; the thermographic sensor further comprises one or more sensing transistors, each driven according to the sensing voltages of one or more corresponding thermo-couples for providing a sensing electrical signal depending on its temperature and on the corresponding sensing voltages. A thermographic device including the thermographic sensor and a corresponding signal processing circuit, and a system including one or more thermographic devices are also proposed.

First claim

The invention claimed is:

1. A thermographic sensor for sensing a thermal radiation, the thermographic sensor comprising:
a body including a first cavity and a second cavity, the body having a membrane including a frame;
one or more thermocouples each having a hot joint configured to be heated to a temperature in response to the thermal radiation and a cold joint configured to be maintained at a temperature independent of the thermal radiation, each thermocouples being configured to provide a sensing voltage based on a difference between the temperature of the hot joint and the temperature of the cold joint;
one or more sensing transistors each configured to be heated to a temperature in response to the thermal radiation and coupled with corresponding one or more of the thermocouples and having a gate terminal coupled to be driven with a corresponding sensing voltage, each sensing transistor being configured to provide a sensing electrical signal based on the temperature of the sensing transistor and on the corresponding sensing voltage;
one or more reference transistors each configured to be shielded from the thermal radiation and have a temperature independent of the thermal radiation, each reference transistor being configured to provide a reference electrical signal based on the temperature of the reference transistor; and
a comparison circuit configured to provide one or more temperature electrical signals indicative of the thermal radiation based on a comparison between a sensing electrical signal of the one or more sensing transistors and a reference electrical signal of the one or more reference transistors.

2. The thermographic sensor according to claim 1 , wherein the thermographic sensor comprises one or more reference thermocouples each having a hot joint and a cold joint configured to provide a sensing voltage based on a difference between the temperature of the hot joint and the temperature of the cold joint of the reference thermocouples, the reference thermocouples being configured to be shielded from the thermal radiation and have at a temperature independent of the thermal radiation, and each of the reference transistors is coupled with one or more reference thermocouples and configured to be driven according to a corresponding sensing voltage of the one or more reference thermocouples and to provide a reference electrical signal based on the reference sensing voltages of the one or more reference thermocouples.

3. The thermographic sensor according to claim 1 , wherein the thermographic sensor comprises one or more sensing elements, each sensing element including at least one of the one or more thermocouples and at least one of the one or more sensing transistors, and wherein the thermographic sensor comprises one or more reference elements corresponding to the one or more sensing elements, each reference element comprising at least one of the one or more reference transistors.

4. The thermographic sensor according to claim 3 , wherein the sensing elements are integrated on the body having a substrate, a functional layer and an insulating layer interposed between the substrate and the functional layer, the body being patterned to define a grid of the functional layer and the insulating layer suspended from the substrate, wherein for each of the one or more sensing elements the grid comprises the frame, a plate and one or more arms coupling the plate from the frame, wherein the sensing transistor of the sensing element is formed in the plate and wherein the thermocouple of the sensing element comprises a first conductor of a first electrically conductive material extending from a first terminal of the cold joint in the frame to the plate through one of the arms and a second conductor of a second electrically conductive material, different from the first electrically conductive material, extending from a second terminal of the cold joint in the frame to the plate through one of the arms, the first conductor and the second conductor being short-circuited at the plate into the hot joint.

5. The thermographic sensor according to claim 3 , wherein the thermographic sensor comprises a plurality of sensing elements, the sensing transistors of the sensing elements being coupled to provide a common sensing electrical signal based on the sum of the sensing electrical signals of the plurality of sensing elements and the thermocouples of the plurality of sensing elements being coupled in series to provide a common sensing voltage based on a sum of the sensing voltages of the thermocouples for driving all the sensing transistors, and wherein the comparison circuit is configured to provide a temperature electrical signal based on a comparison between the common sensing signal.

6. The thermographic sensor according to claim 5 , wherein each of the sensing transistors has a first conduction terminal and a second conduction terminal for providing the corresponding a sensing current as a sensing electrical signal, the first conduction terminals and the second conduction terminals of the sensing transistors being coupled in parallel into a common first conduction terminal and a common second conduction terminal, respectively, for providing a common sensing current as the common sensing electrical signal, and wherein each of the sensing transistors has a control terminal for controlling the sensing transistor, the control terminals of the sensing transistors being coupled in parallel into a common control terminal that is coupled to receive the common sensing voltage.

7. The thermographic sensor according to claim 6 , wherein the second terminal of a first thermocouple is coupled with the first terminal of a second thermocouple in the corresponding frames, the first terminal of the first thermocouple being a biasing terminal for receiving a biasing voltage of the thermographic sensor and the second terminal of the second thermocouple being coupled with the control terminal of each of the sensing transistors through a corresponding one of the arms.

8. The thermographic sensor according to claim 1 , wherein the thermographic sensor comprises a plurality of sensing elements, in each of the sensing elements the sensing transistor being coupled with a thermocouple to be driven based on sensing voltage of the thermocouple, and wherein the comparison circuit is configured to provide a corresponding one of the temperature electrical signals for each of the sensing elements according to a comparison between the sensing signal of the sensing transistor thereof and the reference signal of the corresponding reference element.

9. The thermographic sensor according to claim 8 , wherein in each of the sensing elements the second terminal of the thermocouple is coupled with the control terminal of the sensing transistor through one of the arms.

10. The thermographic sensor according to claim 1 , wherein the sensing transistors are thermally insulated MOS (TMOS) transistors.

Assignees

• St Microelectronics Srl

Inventors

• Bruno Giuseppe
• Vaiana Michele
• Castagna Maria Eloisa
• Recchia Angelo

Classifications

• H10D48/50

  Devices controlled by mechanical forces, e.g. pressure · CPC title

• G01J5/48

  Thermography; Techniques using wholly visual means · CPC title

• G01J5/14 Primary

  Electrical features thereof · CPC title

• G01J5/068

  by controlling parameters other than temperature · CPC title

• G01J5/20

  using resistors, thermistors or semiconductors sensitive to radiation, e.g. photoconductive devices · CPC title