Self-check system, self-check circuit and self-check method for a thermopile-based device

Abstract

The present invention provides a self-checking system, a self-checking circuit and a self-checking method for a device based on a thermopile. The self-checking circuit includes: a power control circuit configured to apply a voltage or current excitation through the thermopile and turn off the excitation of the thermopile when the temperature of the thermopile rises to a preset temperature; a voltage measurement circuit configured to measure the change curve of the output voltage of the thermopile when the power control circuit turns off the excitation of the thermopile; a signal processing circuit configured to calculate the cooling response time of the thermopile based on the change curve of the output voltage of the thermopile; and determine whether the device based on the thermopile is qualified based on the cooling response time. Compared with the prior art, in the self-checking mode, the present invention provides a voltage or current excitation through the thermopile to heat it up, and realizes the self-checking function and judges the state of the chip by recording and calculating the cooling response time of the thermopile.

Description

Technical Field

[0001] The present invention relates to the field of MEMS (Micro-Electro-Mechanical System) devices, and particularly to a self-check system, a self-check circuit and a self-check method for a device based on a thermopile.

Background Art

[0002] During the production and use of infrared sensors, defective devices will inevitably occur. In order to conveniently and timely detect problems and ensure the accuracy of infrared testing, infrared sensors should have a self-detection function. In the usual technical solutions, some need to additionally set up a dedicated heating unit for self-check to generate excitation, which occupies a valuable sensitive area. Some need to heat different zones of the sensor thermopile and then measure the absolute values of the outputs of each other. The above methods can play a certain degree of detection role, but they cannot test and distinguish important failure modes such as whether the etching is clean, whether the package is airtight, and whether the gas composition is correct.

[0003] Therefore, it is necessary to propose a new technical solution to overcome the above problems.

Summary of the Invention

[0004] One object of the present invention is to provide a self-check system, a self-check circuit and a self-check method for a device based on a thermopile, which can realize the self-check of the device based on the thermopile without additionally setting up a dedicated heating unit.

[0005] According to the first aspect of the present invention, there is provided a self-check circuit for a device based on a thermopile, characterized in that it includes: a power control circuit configured to apply a voltage or current excitation through the thermopile when entering the self-check mode to heat up the thermopile, and to turn off the excitation of the thermopile when the temperature of the thermopile rises to a preset temperature; a voltage measurement circuit configured to measure the change curve of the output voltage of the thermopile when the power control circuit turns off the excitation of the thermopile; a signal processing circuit configured to calculate the cooling response time of the thermopile based on the change curve of the output voltage of the thermopile; and further configured to determine whether the device based on the thermopile is qualified based on the cooling response time.

[0006] According to a second aspect of the present invention, the present invention provides a self-checking system for a thermopile-based device, which includes: a thermopile-based device and a self-checking circuit. The self-checking circuit includes: a power control circuit configured to apply a voltage or current excitation through the thermopile when entering the self-checking mode to heat up the thermopile, and to turn off the excitation of the thermopile when the temperature of the thermopile rises to a preset temperature; a voltage measurement circuit configured to measure the change curve of the output voltage of the thermopile when the power control circuit turns off the excitation of the thermopile; a signal processing circuit configured to calculate the cooling response time of the thermopile based on the change curve of the output voltage of the thermopile; and further configured to determine whether the thermopile-based device is qualified based on the cooling response time.

[0007] According to a third aspect of the present invention, the present invention provides a self-checking method for a thermopile-based device, which includes: when entering the self-checking mode, applying a voltage or current excitation through the thermopile to heat up the thermopile; when the temperature of the thermopile rises to a preset temperature, turning off the excitation of the thermopile and measuring the change curve of the output voltage of the thermopile; calculating the cooling response time of the thermopile based on the change curve of the output voltage of the thermopile; and determining whether the thermopile-based device is qualified based on the cooling response time.

[0008] Compared with the prior art, in the self-checking mode, the present invention provides a voltage or current excitation through the thermopile to heat it up, and realizes the self-checking function and judges the state of the chip by recording and calculating the cooling response time of the thermopile.

Description of the Drawings

[0009] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings. Among them:

[0010] Figure 1 is a circuit schematic diagram of a self-checking system for a thermopile-based device in an embodiment of the present invention;

[0011] Figure 2 is as in an embodiment of the present invention Figure 1 shown in the flowchart of the self-checking method of the self-checking circuit;

[0012] Figure 3 is as in an embodiment of the present invention Figure 1 shown in the typical self-checking output curve of the thermopile measured by the voltage measurement circuit;

[0013] Figure 4 It is a top view of a typical thermopile infrared sensor.

Specific Embodiments

[0014] To make the above objects, features, and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0015] As used herein, the term "one embodiment" or "embodiment" refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments. Unless otherwise specified, the words indicating electrical connection such as "connected", "coupled", and "joined" in this article all mean direct or indirect electrical connection.

[0016] Please refer to Figure 1 shown, which is a schematic circuit diagram of a self-checking system of a thermopile-based device in one embodiment of the present invention. Figure 1 The self-checking system of the thermopile-based device shown includes a thermopile-based device 110 and a self-checking circuit 120.

[0017] In Figure 1 the specific embodiment shown, the thermopile-based device 110 is a thermopile infrared sensor. Please refer to Figure 4 shown, which is a top view of a typical thermopile infrared sensor. Figure 4 The thermopile infrared sensor shown includes a support and an infrared absorption coating 410 located on a base layer (not shown), an absorption region 420 located in the middle of the support and the infrared absorption coating 410, a plurality of thermocouples T1, T2, T3, T4 located around the absorption region 420, an infrared absorption optimization layer 430 located in the absorption region 420, and a plurality of etching holes 440 distributed in the absorption region 420. The etching holes 440 sequentially penetrate through the infrared absorption optimization layer 430, the support and the infrared absorption coating 410 to the base layer. Among them, the plurality of thermocouples T1, T2, T3, T4 are connected in series in sequence to form a thermopile.

[0018] The self-checking circuit 120 includes a power control circuit 122, a voltage measurement circuit 124, and a signal processing circuit (or microprocessor) 126.

[0019] The power control circuit 122 is connected to the thermopile infrared sensor 110, and the power control circuit 122 is configured to: apply a preset voltage or current excitation to the thermopile when entering the self-check mode. Due to the generated Joule heat, the temperature of the thermopile will rapidly rise to a preset temperature; when the temperature of the thermopile rises to the preset temperature, turn off the excitation of the thermopile (or stop providing voltage or current excitation to the thermopile). For example, by applying a certain controlled voltage to the thermopile through the power control circuit 122, heat is generated due to the Joule effect, and the temperature of the thermopile rises, where

[0020]

[0021] P is the total power applied to the thermopile, V is the voltage applied to the thermopile, and R is the total resistance of the thermopile.

[0022] The voltage measurement circuit 124 is configured to: measure the change curve of the output voltage of the thermopile when the temperature of the thermopile rises to the preset temperature and the power control circuit 122 turns off the excitation of the thermopile.

[0023] The signal processing circuit 126 is configured to: calculate the time constant τ of the thermopile based on the change curve of the output voltage of the thermopile measured by the voltage measurement circuit 124. The time constant τ of the thermopile is: in the change curve of the output voltage of the thermopile, the time required for the output voltage of the thermopile to decay from the maximum value to 1 / e of the maximum value (or to decrease by 63.2% of the maximum value).

[0024] The change curve of the output voltage of the thermopile (or the self-check output curve of the thermopile) generally conforms to the following formula:

[0025]

[0026] where V is the output voltage (or self-check output voltage) across the thermopile; e is the natural constant, whose value is approximately 2.718281828459045; τ is the time constant of the thermopile; and t is the decay time of the output voltage of the thermopile.

[0027] The time constant τ of the thermopile = R × C (3),

[0028] where R is the thermal resistance of the thermopile and C is the heat capacity of the thermopile. Therefore, the time constant τ of the thermopile is related to the specific heat capacity, density, and volume of the gas and the thermopile structure within the thermopile infrared sensor 110.

[0029] Please refer to Figure 3 as shown, which is in one embodiment of the present invention as Figure 1The typical self-check output curve of the thermopile measured by the shown voltage measurement circuit 124. At Figure 3 In the shown embodiment, the self-check output curves of the thermopile in three cases are shown, namely the self-check output curve of a normal thermopile, the self-check output curve of a thermopile with silicon residue, and the self-check output curve of a thermopile with insufficient air pressure. And the signal processing circuit 126 calculates the time constants τ of the three cases to be 11, 15, and 21 milliseconds respectively based on the self-check output curves of the thermopile in these three cases.

[0030] In one embodiment, the way for the signal processing circuit 126 to calculate the time constant τ of the thermopile based on the self-check output curve of the thermopile is: record the decay time when the output voltage of the thermopile drops from the highest point to the lowest point (the output value is equal to or infinitely close to zero), and calculate the time constant τ of the thermopile based on the decay time, where the highest point is the output voltage value when the thermopile is at the preset temperature, and the lowest point is the output voltage value when the thermopile drops to the ambient temperature (theoretically should be equal to or infinitely close to zero).

[0031] It should be noted specifically that Figure 1 The shown self-check circuit 120 further includes a signal amplification module (not shown) and an analog-to-digital conversion module (not shown). Among them, the output end of the voltage measurement circuit 124 is connected to the input end of the signal amplification module, the output end of the signal amplification module is connected to the input end of the analog-to-digital conversion module, and the output end of the analog-to-digital conversion module is connected to the input end of the signal processing module 126. The signal amplification module is used to amplify the change curve of the output voltage of the thermopile measured by the voltage measurement circuit 124; the analog-to-digital conversion module is used to convert the amplified change curve of the output voltage of the thermopile into a digital signal; the signal processing module 126 calculates the time constant τ of the thermopile based on this digital signal.

[0032] The signal processing circuit 126 is further configured to: determine whether the thermopile infrared sensor 110 is qualified based on the time constant τ of the thermopile calculated by the signal processing circuit 126. Specifically, the signal processing circuit 126 compares the calculated time constant τ of the thermopile with the reference time constant. If it is within the reference time constant range, it determines that the device is qualified; otherwise, it determines that the device is unqualified.

[0033] The signal processing circuit 126 is further configured to: after determining that the device is unqualified, judge the failure mode according to the magnitude of the difference between the calculated time constant τ of the thermopile and the reference constant. The failure modes include: unclean etching, air leakage in packaging, incorrect gas components, incorrect air pressure, device malfunction, etc.

[0034] The signal processing circuit 126 is further configured such that: when there is no pre-stored time constant in the memory (not identified), the reference time constant is a preset time constant; when there is a pre-stored time constant in the memory, the reference time constant is the pre-stored time constant. In one embodiment, the preset time constant may be the measured theoretical value range of the time constant.

[0035] The signal processing circuit 126 is further configured to: after determining that the device is qualified, store the calculated time constant τ of the thermopile in the memory as the pre-stored time constant for subsequent self-checking.

[0036] Please refer to Figure 2 as shown, which is a schematic flowchart of the self-checking method of the self-checking circuit 120 in one embodiment of the present invention Figure 1 as shown. Figure 2 The self-checking method of the self-checking circuit shown includes the following steps.

[0037] Step 201: Enter the test mode (or self-checking mode), and apply a preset voltage or current excitation through the thermopile via the power control circuit 122 to make it generate heat.

[0038] Step 202: When the temperature of the thermopile rises to the preset temperature, immediately stop the excitation of the thermopile via the power control circuit 122, and immediately measure and collect the change curve of the output voltage of the thermopile (or the output voltage across the two ends of the thermocouple in the thermopile).

[0039] Step 203: The signal processing circuit 126 calculates the time constant τ of the thermopile based on the change curve of the output voltage of the thermopile measured by the voltage measurement circuit 124.

[0040] Step 204: The signal processing circuit 126 determines whether there is a pre-stored time constant. If there is, go to Step 205; if not, go to Step 206.

[0041] Step 205: The signal processing circuit 126 compares the pre-stored time constant as the reference time constant with the calculated time constant τ. If the requirement is met (i.e., within the range of the pre-stored time constant), go to Step 208 to determine that the device is qualified; otherwise (i.e., not within the pre-stored time constant), go to Step 207 to determine that the device is unqualified.

[0042] Step 206: The signal processing circuit 126 compares the preset time constant with the calculated time constant τ as the reference time constant. If the requirement is met (i.e., within the range of the preset time constant), it proceeds to Step 208 to determine that the device is qualified, and proceeds to Step 209 to store the calculated time constant τ as the pre-stored time constant for subsequent self-check; otherwise (i.e., not within the preset time constant range), it proceeds to Step 207 to determine that the device is unqualified. In one embodiment, the preset time constant can be the measured theoretical value range of the time constant.

[0043] Step 210: After determining that the device is unqualified, based on the magnitude of the difference between the calculated time constant τ and the reference constant, the failure mode is judged. The failure modes include: incomplete etching, package leakage, incorrect gas components, incorrect air pressure, device malfunction, etc.

[0044] It should be particularly noted that Steps 206 to 209 can be summarized as: The signal processing circuit 126 compares the time constant τ of the thermopile obtained by calculation with the reference time constant to determine whether the thermopile infrared sensor 110 is qualified.

[0045] The self-check circuit and self-check method in the present invention have the following advantages:

[0046] 1. The present invention is applicable to all infrared detectors. No additional heaters or heating units are required.

[0047] 2. The present invention does not require the heating unit to occupy the effective area of the infrared detector, increasing the sensitivity.

[0048] 3. The present invention does not require adding additional circuits to the structure of the infrared detector.

[0049] 4. The present invention does not require adding specific layers for adding heaters, reducing the manufacturing cost.

[0050] 5. During the production process, the present invention can determine the status of each chip in the wafer state, for example, whether the etching is clean, whether there are problems such as the rupture of the detection structure. That is to say, the present invention can be used for wafer-level testing of production devices. This can pick out damaged chips in advance, reduce the waste of subsequent packaging materials, and improve the efficiency of the packaging process.

[0051] 6. During the production process, through the self-check function in the present invention, it can be confirmed whether the package is normal, whether the gas leaks, whether the air pressure is accurate, and whether the detection structure is damaged during the packaging process. That is to say, the present invention can be used for package-level testing of production devices.

[0052] 7. The self-checking circuit and method in the present invention are also applicable to an infrared detection module or other similar infrared detectors.

[0053] In summary, in the self-checking mode of the present invention, a voltage or current excitation is provided to heat up the thermopile, and the self-checking function is realized by recording and calculating the response time of the thermopile to cool down, so as to judge the state of the chip. It can not only improve the coverage rate and detection accuracy of the self-checking content of the thermopile infrared sensor, but also does not require an additional dedicated heating unit, realizing the detection of the functions and package integrity of the sensor.

[0054] In the present invention, words indicating electrical connection such as "connected", "linked", "joined", "connected to", etc., unless otherwise specified, mean direct or indirect electrical connection.

[0055] The above is only the preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiment. Any equivalent modification or change made by those of ordinary skill in the art according to the disclosure of the present invention shall be included in the protection scope recorded in the claims.

Claims

1. A self-checking circuit for a thermopile-based device, characterized in that, It includes: A power control circuit, which is configured to apply a voltage or current excitation through the thermopile when entering the self - test mode to heat up the thermopile, and when the temperature of the thermopile rises to a preset temperature, turn off the excitation to the thermopile; A voltage measurement circuit, which is configured to measure the change curve of the output voltage of the thermopile when the power control circuit turns off the excitation to the thermopile; A signal processing circuit, which is configured to calculate the cooling response time of the thermopile based on the change curve of the output voltage of the thermopile; It is also configured to determine whether the thermopile - based device is qualified based on the cooling response time; The cooling response time of the thermopile is the time constant τ of the thermopile. The time constant τ of the thermopile is: in the change curve of the output voltage of the thermopile, the time required for the output voltage of the thermopile to decay from the maximum value to 1 / e of the maximum value, The signal processing circuit calculates the time constant τ of the thermopile based on the change curve of the output voltage of the thermopile, including: recording the decay time of the output voltage of the thermopile from the highest point to the lowest point, and calculating the time constant of the thermopile based on the decay time, where the highest point is the output voltage value when the thermopile is at the preset temperature, and the lowest point is the output voltage value when the thermopile drops to the ambient temperature.

2. The self-checking circuit for a thermopile-based device according to claim 1, characterized in that, The signal processing circuit is also configured to determine the failure mode of the thermopile - based device based on the cooling response time.

3. The self-checking circuit for a thermopile-based device according to claim 1, characterized in that, The signal processing circuit is configured to determine whether the thermopile - based device is qualified based on the time constant τ of the thermopile, including: The signal processing circuit compares the time constant τ of the thermopile with a reference time constant. If it is within the reference time constant range, it determines that the device is qualified; if it is not within the reference time constant range, it determines that the device is unqualified.

4. The self-checking circuit for a thermopile-based device according to claim 3, characterized in that, The signal processing circuit is also configured to: after determining that the device is unqualified, determine the failure mode according to the magnitude of the difference between the time constant τ of the thermopile and the reference time constant; The failure modes include: incomplete etching, package leakage, incorrect gas components, incorrect air pressure, and device malfunction.

5. The self-checking circuit for a thermopile-based device according to claim 3, characterized in that, The signal processing circuit is also configured to: when there is no pre - stored time constant in the memory, the reference time constant is a preset time constant; when there is a pre - stored time constant in the memory, the reference time constant is the pre - stored time constant, The signal processing circuit is also configured to: after determining that the device is qualified, store the time constant τ of the thermopile in the memory as the pre - stored time constant.

6. A self-checking system for a thermopile-based device, characterized in that, It includes: A thermopile - based device; The self - test circuit according to any one of claims 1 - 5.

7. A self-checking method for a thermopile-based device, characterized in that, It includes: When entering the self - test mode, apply a voltage or current excitation through the thermopile to heat up the thermopile; When the temperature of the thermopile rises to a preset temperature, turn off the excitation to the thermopile and measure the change curve of the output voltage of the thermopile; Calculate the cooling response time of the thermopile based on the change curve of the output voltage of the thermopile; Determine whether the thermopile-based device is qualified based on the cooling response time; The cooling response time of the thermopile is the time constant τ of the thermopile, and the time constant τ of the thermopile is: in the change curve of the output voltage of the thermopile, the time required for the output voltage of the thermopile to decay from the maximum value to 1 / e of the maximum value, Calculating the time constant τ of the thermopile based on the change curve of the output voltage of the thermopile includes: recording the decay time of the output voltage of the thermopile from the highest point to the lowest point, and calculating the time constant of the thermopile based on the decay time, where the highest point is the output voltage value when the thermopile is at the preset temperature, and the lowest point is the output voltage value when the thermopile drops to the ambient temperature.

8. The self-checking method for a thermopile-based device according to claim 7, characterized in that, The cooling response time of the thermopile is the time constant τ of the thermopile, Determining whether the thermopile-based device is qualified based on the time constant τ of the thermopile includes: Determine whether there is a pre-stored time constant; If there is a pre-stored time constant, then use the pre-stored time constant as the reference time constant to compare with the time constant τ of the thermopile. If it is within the range of the pre-stored time constant, determine that the device is qualified, otherwise determine that the device is unqualified; If there is no pre-stored time constant, then use the preset time constant as the reference time constant to compare with the time constant τ of the thermopile. If it is within the range of the preset time constant, determine that the device is qualified, and store the time constant τ of the thermopile, otherwise determine that the device is unqualified.

9. The self-checking method of the thermopile-based device according to claim 8, characterized in that, It further includes: after determining that the device is unqualified, determine the failure mode according to the magnitude of the difference between the time constant τ of the thermopile and the reference time constant, The failure modes include: unclean etching, package leakage, incorrect gas composition, incorrect air pressure, and device malfunction.

10. The self-checking method of the thermopile-based device according to claim 7, characterized in that, The self-test method is used for wafer-level testing of manufactured devices; or The self-test method is used for package-level testing of manufactured devices.

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