Method and device for testing thermal resistance of photoelectric coupler

Abstract

The invention discloses a thermal resistance testing method and device for a photoelectric coupler. The method comprises the following steps: acquiring a temperature and pressure drop characteristic curve of the photoelectric coupler; determining junction temperatures of the photoelectric coupler under different test powers according to the temperature and pressure drop characteristic curve; and determining the thermal resistance of the photoelectric coupler according to the relationship between the junction temperature and the test power. According to the technical scheme provided by the invention, the current of the input end of the photoelectric coupler is controlled to be unchanged, so that the illumination intensity of the photoelectric coupler is a fixed value; measuring the voltage of the output side of the photoelectric coupler at different junction temperatures to obtain a temperature and voltage drop characteristic curve of the photoelectric coupler; the voltage of the output side is obtained by changing the power applied to the output end of the photoelectric coupler, then the junction temperature of the photoelectric coupler under the corresponding voltage is searched according to the temperature and voltage drop characteristic curve, the thermal resistance of the photoelectric coupler is calculated by adopting a thermal resistance general formula, and the maximum power rated value of the photoelectric coupler is calibrated according to the thermal resistance. And product use is guided.

Description

Technical Field

[0001] The present invention relates to the technical field of photoelectric couplers, and in particular to a method and device for testing thermal resistance of a photoelectric coupler. Background Art

[0002] In addition to signal isolation and transmission, output-type photocouplers also require a certain power handling capability at their output terminals. Excessive power can easily damage the photocoupler. Therefore, measuring the thermal resistance of output-type photocouplers is necessary to calibrate the photocoupler's operating parameters and ensure proper product operation. Currently, thermal resistance testing of photocouplers is not available in the industry. A method for performing thermal resistance testing on the entire photocoupler is urgently needed. Summary of the Invention

[0003] The present invention provides a method and device for testing the thermal resistance of a photoelectric coupler, so as to measure the thermal resistance of the photoelectric coupler and perform parameter calibration on the photoelectric coupler.

[0004] According to one aspect of the present invention, a method for testing thermal resistance of an optocoupler is provided, comprising:

[0005] Obtaining a temperature-voltage drop characteristic curve of the photoelectric coupler;

[0006] determining the junction temperature of the photoelectric coupler at different test powers according to the temperature-voltage drop characteristic curve;

[0007] The thermal resistance of the optocoupler is determined according to the relationship between the junction temperature and the test power.

[0008] Optionally, obtaining a temperature-voltage drop characteristic curve of the photoelectric coupler includes:

[0009] Obtaining the voltage drop of the photoelectric coupler at different test temperatures;

[0010] A temperature-voltage drop characteristic curve is determined according to the voltage drop and the test temperature.

[0011] Optionally, before obtaining the voltage drop of the photoelectric coupler at different test temperatures, the method includes:

[0012] The first test current and the second test current of the photoelectric coupler are determined according to the maximum output current and the input current of the photoelectric coupler; wherein the first test current is the current on the output side of the photoelectric coupler, and the second test current is the current on the input side of the photoelectric coupler.

[0013] Optionally, obtaining the voltage drop of the photoelectric coupler at different test temperatures includes:

[0014] placing the photoelectric coupler in a test liquid;

[0015] The first test current and the second test current of the photoelectric coupler are controlled to remain unchanged, and the voltage drop of the photoelectric coupler corresponding to the test liquid at different temperature data is obtained.

[0016] Optionally, determining a temperature-voltage drop characteristic curve according to the voltage drop and the test temperature includes:

[0017] The temperature-voltage drop characteristic curve is obtained by linearly fitting the multiple sets of temperature data and the corresponding voltage drops.

[0018] Optionally, determining the junction temperature of the optocoupler at different test powers according to the temperature-voltage drop characteristic curve includes:

[0019] controlling the first test current and the second test current of the photoelectric coupler to remain unchanged, and obtaining the instantaneous voltage drop of the photoelectric coupler under different test powers;

[0020] The junction temperature of the optocoupler is determined according to the instantaneous voltage drop and the temperature-voltage drop characteristic curve.

[0021] Optionally, the thermal resistance of the optocoupler is determined according to the relationship between the junction temperature and the test power, and is determined by the following formula:

[0022]

[0023] Among them, R thJ-A is the thermal resistance of the optocoupler, T J is the junction temperature of the optocoupler, T A is the ambient temperature during the test, and P is the test power of the photoelectric coupler.

[0024] Optionally, the first test current of the photoelectric coupler is less than 1 / 10 of the maximum output current of the photoelectric coupler.

[0025] Optionally, the test power is greater than or equal to ten times the dissipated power of the input end of the optocoupler.

[0026] According to another aspect of the present invention, a device for testing thermal resistance of a photoelectric coupler is provided, which uses the method for testing thermal resistance of a photoelectric coupler according to any one of the first aspects to perform thermal resistance testing on the photoelectric coupler.

[0027] The technical solution provided by the embodiment of the present invention controls the current at the input end of the photoelectric coupler to remain constant so that the light intensity of the photoelectric coupler is constant; measures the voltage at the output side of the photoelectric coupler at different junction temperatures to obtain the temperature-voltage drop characteristic curve of the photoelectric coupler; obtains the voltage drop at the output end of the photosensitive side by adjusting the power applied to the output end of the photoelectric coupler, and then obtains the junction temperature of the photoelectric coupler at the corresponding voltage drop based on the temperature-voltage drop characteristic curve. The thermal resistance of the photoelectric coupler is then calculated using a general formula for the thermal resistance of components. Therefore, the maximum power rating of the photoelectric coupler can be calibrated based on the thermal resistance to guide product use.

[0028] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present invention, nor is it intended to limit the scope of the present invention. Other features of the present invention will become readily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 A schematic structural diagram of a photoelectric coupler provided in an embodiment of the present invention;

[0031] Figure 2 A flow chart of a method for testing thermal resistance of a photoelectric coupler provided in an embodiment of the present invention;

[0032] Figure 3 A flow chart of another method for testing thermal resistance of an optocoupler provided in an embodiment of the present invention;

[0033] Figure 4 The output voltage and temperature characteristic curve of a photoelectric coupler under different power-on conditions provided by an embodiment of the present invention;

[0034] Figure 5 The temperature-voltage drop characteristic curve obtained by fitting the thermal resistance testing method of the optocoupler provided by the embodiment of the present invention;

[0035] Figure 6 A flow chart of another method for testing thermal resistance of an optocoupler provided in an embodiment of the present invention;

[0036] Figure 7 An input characteristic curve of a photoelectric coupler under different temperature conditions provided by an embodiment of the present invention;

[0037] Figure 8An output characteristic curve of a photoelectric coupler under different input conditions provided by an embodiment of the present invention;

[0038] Figure 9 A flow chart of a method for obtaining the voltage drop of an optocoupler at different test temperatures provided by an embodiment of the present invention;

[0039] Figure 10 A flow chart of another method for testing thermal resistance of an optocoupler provided in an embodiment of the present invention;

[0040] Figure 11 A flowchart of another method for testing thermal resistance of an optocoupler provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0041] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0042] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0043] Figure 1 A schematic structural diagram of a photoelectric coupler provided in an embodiment of the present invention. Figure 2 This is a flow chart of a method for testing the thermal resistance of a photoelectric coupler provided by an embodiment of the present invention. Figure 1 and Figure 2 , a photocoupler is an electronic device that achieves electrical isolation through optical signals and can be used in scenarios such as signal isolation, noise suppression, and level conversion. A photocoupler can usually be composed of three parts: a light-emitting part, a photosensitive part, and a shell; among them, the light-emitting part and the photosensitive part are encapsulated in an opaque insulating package. Figure 1As shown, the light-emitting portion of the photocoupler can be a light-emitting diode 10, and the light-sensitive portion can be a phototransistor 20. The light-emitting diode 10 and the phototransistor 20 are encapsulated in an opaque insulating package 30. When current at the input end of the photocoupler flows through the light-emitting diode 10, the light-emitting diode 10 emits light. After the phototransistor 20 receives the light, conduction between the collector and emitter electrodes generates an output current, thereby achieving conversion between electrical signals, optical signals, and electrical signals.

[0044] The thermal resistance testing method of a photoelectric coupler disclosed in an embodiment of the present invention includes:

[0045] S110 , obtaining a temperature-voltage drop characteristic curve of the photoelectric coupler.

[0046] Specifically, the temperature voltage drop characteristic curve of the photoelectric coupler refers to the curve of the voltage at the photosensitive side output end of the photoelectric coupler 20 changing with temperature when the light intensity of the light-emitting diode 10 is constant and the output side current is a certain value, that is, when the input side current of the light-emitting diode 10 and the current between the collector and emitter of the phototransistor 20 are constant, the curve of the voltage between the collector and emitter of the phototransistor 20 changing with the junction temperature of the photocoupler 20. The thermal resistance test method provided in the embodiment of the present invention can be applied to BJT output type photoelectric couplers and other types of photoelectric couplers. Figure 1 In the photoelectric coupler shown, the current flowing through the light-emitting diode 10 can be controlled to remain constant, which is equivalent to controlling the light intensity of the light-emitting diode 10 to a constant value, and intermittent short-term constant pulse current is connected between the collector and emitter of the phototransistor 20. Then, the voltage between the collector and emitter of the phototransistor 20 of the photocoupler is measured at different junction temperatures, thereby obtaining the temperature-voltage drop characteristic curve of the photoelectric coupler under standard experimental conditions.

[0047] S120 . Determine the junction temperature of the optocoupler at different test powers according to the temperature-voltage drop characteristic curve.

[0048] Specifically, the test power of the optocoupler refers to the power at the output of the optocoupler, that is, the power applied between the collector and emitter of the phototransistor in the optocoupler during the test. During the actual thermal resistance test of the optocoupler, the power applied to the output of the optocoupler can be adjusted, and the instantaneous voltage on the output side can be obtained. Then, the junction temperature of the optocoupler under the corresponding instantaneous voltage can be found based on the temperature-voltage drop characteristic curve. Figure 1The photoelectric coupler shown adjusts the test power applied between the collector and emitter of the phototransistor 20 and obtains the voltage drop between the collector and emitter of the phototransistor 20. The junction temperature of the photoelectric coupler corresponding to the voltage drop is found according to the temperature-voltage drop characteristic curve. It should be noted that during actual testing, it is necessary to control the input-side current of the photoelectric coupler to be consistent with the input current of the light-emitting diode 10 under standard experimental conditions, and to control the output-side current to be consistent with the current applied between the collector and emitter of the phototransistor 20 under standard experimental conditions, so as to ensure that the voltage drop at the output end of the photoelectric coupler can correspond to the temperature one-to-one, thereby ensuring the accuracy of the results.

[0049] S130 , determining the thermal resistance of the optocoupler based on the relationship between the junction temperature and the test power.

[0050] Specifically, after the test power and junction temperature of the optocoupler are determined, the thermal resistance of the optocoupler can be calculated based on the ambient temperature during actual use and the general formula for the thermal resistance of components.

[0051] The technical solution provided by the embodiment of the present invention controls the current at the input end of the photoelectric coupler to remain constant so that the light intensity of the photoelectric coupler is constant; measures the voltage at the output side of the photoelectric coupler at different junction temperatures to obtain the temperature-voltage drop characteristic curve of the photoelectric coupler; obtains the voltage drop at the output end of the photosensitive side by adjusting the power applied to the output end of the photoelectric coupler, and then obtains the junction temperature of the photoelectric coupler at the corresponding voltage drop based on the temperature-voltage drop characteristic curve. The thermal resistance of the photoelectric coupler is then calculated using a general formula for the thermal resistance of components. Therefore, the maximum power rating of the photoelectric coupler can be calibrated based on the thermal resistance to guide product use.

[0052] Optionally, Figure 3 A flowchart of another method for testing thermal resistance of an optocoupler provided by an embodiment of the present invention. Figure 4 The output voltage and temperature characteristic curves of a photoelectric coupler under different power-on conditions are provided in an embodiment of the present invention. Figure 5 The temperature-voltage drop characteristic curve is obtained by fitting the thermal resistance test method of the optocoupler provided by the embodiment of the present invention. Figure 3 、 Figure 4 and Figure 5 , the thermal resistance test methods of optocouplers include:

[0053] S210. Obtain the voltage drop of the optocoupler at different test temperatures.

[0054] Specifically, the photocoupler can be placed in a container with an adjustable internal temperature. At this time, the photocoupler and the container as a whole are in a steady state. Then, the current on the input side of the photocoupler is controlled to remain unchanged to control the light intensity inside the photocoupler to remain unchanged. An intermittent short-time constant-value pulse current source is connected between the collector and emitter of the phototransistor. By adjusting the temperature of the photocoupler and the container as a whole, the junction temperature of the photocoupler is changed, and the voltage drop on the output side of the photocoupler at different test temperatures is measured.

[0055] S220. Determine a temperature-voltage drop characteristic curve according to the voltage drop and the test temperature.

[0056] Specifically, the voltage drop data obtained from the test can be curve-fitted with the corresponding test temperature to obtain a temperature-voltage drop curve. Figure 4 As shown, the horizontal axis is the junction temperature T of the optocoupler, and the vertical axis is the output voltage U on the output side of the optocoupler. Curve L1 and curve L2 are the temperature-voltage drop characteristic curves of the optocoupler under different power-on conditions. Under different conditions of the input side current and output side current of the optocoupler, the voltage drop and test temperature of the optocoupler will show different characteristics; by changing the input side current and output side current of the optocoupler, a temperature-voltage drop characteristic curve showing a linear relationship between the voltage drop and the test temperature can be obtained. As shown Figure 5 As shown, curve K2 is a temperature-voltage drop characteristic curve obtained by connecting multiple sets of data obtained by the thermal resistance testing method of the optocoupler provided by an embodiment of the present invention, and curve K1 is a temperature-voltage drop characteristic curve obtained by fitting curve K2 using the industry-wide equipment PHASE11.

[0057] S230 . Determine the junction temperature of the optocoupler at different test powers according to the temperature-voltage drop characteristic curve.

[0058] S240. Determine the thermal resistance of the optocoupler based on the relationship between the junction temperature and the test power.

[0059] The technical solution provided by the present invention places a photoelectric coupler in a container with an adjustable internal temperature, so that the photoelectric coupler and the container as a whole are in a steady state. By adjusting the temperature of the photoelectric coupler and the container as a whole, the junction temperature of the photoelectric coupler is changed, thereby measuring the voltage drop on the output side of the photoelectric coupler at different test temperatures under standard experimental conditions, and then obtaining a temperature-voltage drop characteristic curve of the photoelectric coupler. By adjusting the power-on conditions of the photoelectric coupler, a temperature-voltage drop characteristic curve showing a linear relationship between the voltage drop and the test temperature can be obtained.

[0060] Optionally, Figure 6 A flowchart of another method for testing thermal resistance of an optocoupler provided by an embodiment of the present invention. Figure 7The input characteristic curve of the photoelectric coupler under different temperature conditions provided by the embodiment of the present invention is as follows: Figure 8 The output characteristic curve of the photoelectric coupler under different input conditions provided by the embodiment of the present invention is shown in FIG. Figure 6 、 Figure 7 and Figure 8 , the thermal resistance test methods of optocouplers include:

[0061] S310. Determine a first test current and a second test current of the photoelectric coupler according to the maximum output current and input current of the photoelectric coupler; wherein the first test current is the current on the output side of the photoelectric coupler, and the second test current is the current on the input side of the photoelectric coupler.

[0062] Specifically, the thermal resistance testing method for a photocoupler provided by the present invention can use the industry-standard equipment PHASE11 to perform a thermal resistance test on the photocoupler. During the test, the current applied to the output side and the current applied to the input side of the photocoupler need to be determined based on the maximum output current and input current of the photocoupler. The maximum output current of the photocoupler refers to the maximum current value that can be output between the collector and emitter of the phototransistor on the output side of the photocoupler under a certain input current. When the first test current is applied to the phototransistor on the output side of the photocoupler, the photocoupler will self-heat, causing the junction temperature of the photocoupler to change. Therefore, it is necessary to minimize the impact of the first test current on the junction temperature of the photocoupler. The first test current can be less than 0.1 times the maximum output current of the photocoupler, which can reduce the impact of the first test current on the junction temperature of the photocoupler. Furthermore, the voltage drop on the output side of the photocoupler measured by a smaller first test current will also be smaller, thereby exceeding the error in fitting the temperature-voltage drop characteristic curve of the photocoupler. Therefore, the first test current can select a larger current value while meeting the requirement of less than 0.1 times the maximum output current of the photocoupler.

[0063] like Figure 7 As shown, the horizontal axis is the voltage drop U on the output side of the optocoupler, and the vertical axis is the current I on the output side of the optocoupler C Curves L3-L9 are the output characteristic curves of the optocoupler at different input current values, where the input current values of curves L3-L9 gradually increase. Figure 7 It can be seen that when the input current value of the optocoupler gradually increases, the maximum output current I C Also gradually increases, at this time a larger test current can be applied to the output side of the optocoupler to increase V F , so that the voltage drop on the output side can show a better linear relationship with the temperature. Figure 8As shown, the horizontal axis is the voltage V on the input side of the optocoupler F , the vertical axis is the current I on the input side of the optocoupler F Curves L10 to L19 are the input characteristic curves of the optocoupler at different temperatures. The temperature of curves L10 to L19 gradually increases. Figure 8 It can be seen that the light-emitting diode has an input current I F When fixed, the input voltage V F It decreases with increasing temperature, that is, the luminous power decreases with increasing temperature; a smaller input current will cause the relationship between the first test current and the voltage drop to enter the amplification region or the cutoff region. Therefore, combining the above two points, a current value with a larger gear can be selected as the second test current within the maximum input current range of the optocoupler. After determining the first test current and the second test current, a constant current source with a current value of the second test current can be connected to the light-emitting diode on the input side of the optocoupler, and an intermittent pulse current with a current value of the first test current can be connected to the phototransistor on the output side of the optocoupler. By adjusting the temperature of the optocoupler and the container as a whole, the junction temperature of the optocoupler is changed, thereby measuring the voltage drop on the output side of the optocoupler at different test temperatures under standard experimental conditions, and then obtaining a linear temperature-voltage drop characteristic curve.

[0064] S320 . Determine the junction temperature of the optocoupler at different test powers according to the temperature-voltage drop characteristic curve.

[0065] S330. Determine the thermal resistance of the optocoupler based on the relationship between the junction temperature and the test power.

[0066] The technical solution provided by the present invention determines a first test current and a second test current based on the input and output characteristics of the optocoupler. By adjusting the temperature of the optocoupler and the container as a whole, the junction temperature of the optocoupler is changed. Thus, the voltage drop on the output side of the optocoupler at different test temperatures under standard experimental conditions is measured, and a linear temperature-voltage drop characteristic curve is obtained. This provides an accurate basis for calculating the thermal resistance of the optocoupler and ensures the reliability of the calculated thermal resistance of the optocoupler.

[0067] Optionally, Figure 9 A flow chart of a method for obtaining the voltage drop of an optocoupler at different test temperatures provided by an embodiment of the present invention. Figure 9 , obtain the voltage drop of the optocoupler at different test temperatures, including:

[0068] S410. Place the photoelectric coupler in the test liquid.

[0069] Specifically, a test liquid can be placed in the container where the photocoupler is placed. The junction temperature of the photocoupler can be adjusted by adjusting the temperature of the test liquid and the container. For example, the photocoupler can be placed in an oil tank. In this case, the photocoupler, the oil tank, and the oil in the tank are all in a steady state. The junction temperature of the photocoupler can be adjusted by heating the oil in the tank.

[0070] S420 , controlling the first test current and the second test current of the photoelectric coupler to remain unchanged, and obtaining the voltage drop of the photoelectric coupler corresponding to different temperature data of the test liquid.

[0071] Specifically, after placing the photocoupler in a container containing the test liquid, a constant current source with a current value of the second test current can be connected to the light-emitting diode on the input side of the photocoupler to ensure that the light intensity remains unchanged, and an intermittent pulse current with a current value of the first test current is connected to the phototransistor on the output side of the photocoupler. Then, by adjusting the temperature of the photocoupler and the container as a whole, the junction temperature of the photocoupler is changed, thereby measuring the voltage drop on the output side of the photocoupler at different test temperatures under standard experimental conditions.

[0072] The technical solution provided by the present invention places the photoelectric coupler in a temperature-variable test liquid, so that the photoelectric coupler, the test liquid, and the container as a whole can be considered to be in a steady state. By adjusting the temperature of the test liquid and the container, the junction temperature of the photoelectric coupler can be adjusted, and the voltage drop on the output side of the photoelectric coupler at different test temperatures can be obtained.

[0073] Optionally, Figure 10 This is a flow chart of another method for testing the thermal resistance of an optocoupler provided by an embodiment of the present invention. Figure 10 , the method comprising:

[0074] S510. Determine a first test current and a second test current of the photoelectric coupler according to the maximum output current and input current of the photoelectric coupler; wherein the first test current is the current on the output side of the photoelectric coupler, and the second test current is the current on the input side of the photoelectric coupler.

[0075] S520. Place the photoelectric coupler in the test liquid.

[0076] S530 , controlling the first test current and the second test current of the photoelectric coupler to remain unchanged, and obtaining the voltage drop of the photoelectric coupler corresponding to different temperature data of the test liquid.

[0077] S540 , performing linear fitting on multiple sets of temperature data and corresponding voltage drops to obtain a temperature-voltage drop characteristic curve.

[0078] Specifically, because the influence of power-on conditions on the temperature-voltage drop characteristic curve of the optocoupler is fully considered when determining the first test current and the second test current, the temperature and voltage drop data obtained based on the first test current and the second test current exhibit a substantially linear relationship, and a linear temperature-voltage drop characteristic curve can be determined through linear fitting.

[0079] S550: Determine the junction temperature of the optocoupler at different test powers according to the temperature-voltage drop characteristic curve.

[0080] S560. Determine the thermal resistance of the optocoupler based on the relationship between the junction temperature and the test power.

[0081] Optionally, Figure 11 This is a flow chart of another method for testing the thermal resistance of an optocoupler provided by an embodiment of the present invention. Figure 11 , the method comprising:

[0082] S610. Determine a first test current and a second test current of the photoelectric coupler according to the maximum output current and input current of the photoelectric coupler; wherein the first test current is the current on the output side of the photoelectric coupler, and the second test current is the current on the input side of the photoelectric coupler.

[0083] S620. Place the photoelectric coupler in the test liquid.

[0084] S630 , controlling the first test current and the second test current of the photoelectric coupler to remain unchanged, and obtaining the voltage drop of the photoelectric coupler corresponding to different temperature data of the test liquid.

[0085] S640 , performing linear fitting on multiple sets of temperature data and corresponding voltage drops to obtain a temperature-voltage drop characteristic curve.

[0086] S650 , controlling the first test current and the second test current of the photoelectric coupler to remain unchanged, and obtaining the instantaneous voltage drop of the photoelectric coupler under different test powers.

[0087] Specifically, after obtaining the temperature-voltage drop characteristic curve of the optocoupler under standard experimental conditions, the thermal resistance of the optocoupler can be calculated using the general equipment PHASE11 in actual use. In order to ensure that the temperature-voltage drop characteristic curve is available, it is necessary to control the first test current and the second test current of the optocoupler to remain unchanged. That is, a constant second test current is applied to the input end of the optocoupler, a test power is applied to the output end of the optocoupler, and then the first test current is applied to the output end of the optocoupler at the moment of power removal, and the instantaneous voltage drop at the output end of the optocoupler is measured. By adjusting the applied power, the instantaneous voltage drop of the optocoupler under different test powers is obtained. It should be noted that in the process of applying the test power, the current at the output end of the optocoupler gradually increases. When the current at the output end is small, the corresponding voltage drop at the output end is also small, which is easy to exceed the range of the temperature-voltage drop characteristic curve. The error of the obtained thermal resistance value is large, and this error should be eliminated.

[0088] S660: Determine the junction temperature of the optocoupler according to the instantaneous voltage drop and temperature voltage drop characteristic curve.

[0089] Specifically, the instantaneous voltage drop is used as the voltage drop between the collector and emitter at the output side of the photoelectric coupler, and the junction temperature of the photoelectric coupler corresponding to each instantaneous voltage drop is determined according to the temperature-voltage drop characteristic curve.

[0090] S670. Determine the thermal resistance of the optocoupler based on the relationship between the junction temperature and the test power.

[0091] Specifically, the thermal resistance of the optocoupler can be determined by the following formula:

[0092]

[0093] Among them, R thJ-A is the thermal resistance of the optocoupler, T J is the junction temperature of the optocoupler, T A is the ambient temperature during the test, and P is the test power of the optocoupler. It should be noted that the thermal resistance test process must take into account the self-heating of the light-emitting diode. When the power applied to the optocoupler is low, the power of the light-emitting diode cannot be ignored. The thermal resistance test value calculated according to the thermal resistance calculation formula will be larger than the actual value. Therefore, it is necessary to ensure that the test power is greater than or equal to ten times the power dissipation at the input end of the optocoupler.

[0094] Table 1 shows the thermal resistance test results of the GD4N24 type optocoupler with a B-pole terminal produced using the thermal resistance test method for optocouplers provided in an embodiment of the present invention. Table 2 shows the thermal resistance test results of the GH332-1G BJT output type optocoupler tested using the thermal resistance test method for optocouplers provided in an embodiment of the present invention.

[0095] Table 1:

[0096]

[0097]

[0098] Table 2:

[0099]

[0100] Table 1 shows that at a power of 0.29 W and a junction temperature of approximately 102°C, the test result of the embodiment of the present invention on the GD4N24 optocoupler is approximately 267°C / W. This result is close to the thermal resistance test result of 270°C / W for the GD4N24 optocoupler with a B-pole terminal produced using a traditional test method, verifying the effectiveness of this test method. Table 2 shows that at a power of 0.3 W and a junction temperature of 105°C, the test result of the embodiment of the present invention on the GH332-1G BJT output optocoupler is approximately 271°C / W, verifying the versatility and feasibility of the test method.

[0101] An embodiment of the present invention further provides a thermal resistance testing device for a photoelectric coupler. The thermal resistance testing method for a photoelectric coupler provided by any embodiment of the present invention can be used to test the thermal resistance of the photoelectric coupler, which has the same beneficial effects and will not be described in detail here.

[0102] It should be understood that the various forms of the processes shown above can be used to reorder, add, or delete steps. For example, the steps described in the present invention can be performed in parallel, sequentially, or in a different order, as long as the desired results of the technical solution of the present invention can be achieved. This is not limited herein.

[0103] The above specific embodiments do not limit the scope of protection of the present invention. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. A method for testing thermal resistance of a photoelectric coupler, characterized in that: include: Obtaining a temperature-voltage drop characteristic curve of the photoelectric coupler; determining the junction temperature of the photoelectric coupler at different test powers according to the temperature-voltage drop characteristic curve; The thermal resistance of the optocoupler is determined according to the relationship between the junction temperature and the test power.

2. The thermal resistance testing method of a photoelectric coupler according to claim 1, wherein: Obtaining a temperature-voltage drop characteristic curve of the photoelectric coupler, including: Obtaining the voltage drop of the photoelectric coupler at different test temperatures; A temperature-voltage drop characteristic curve is determined according to the voltage drop and the test temperature.

3. The thermal resistance testing method of a photoelectric coupler according to claim 2, wherein: Before obtaining the voltage drop of the optocoupler at different test temperatures, the following steps are included: The first test current and the second test current of the photoelectric coupler are determined according to the maximum output current and the input current of the photoelectric coupler; wherein the first test current is the current on the output side of the photoelectric coupler, and the second test current is the current on the input side of the photoelectric coupler.

4. The thermal resistance testing method of a photoelectric coupler according to claim 3, wherein: Obtaining the voltage drop of the optocoupler at different test temperatures, including: placing the photoelectric coupler in a test liquid; The first test current and the second test current of the photoelectric coupler are controlled to remain unchanged, and the voltage drop of the photoelectric coupler corresponding to the test liquid at different temperature data is obtained.

5. The thermal resistance testing method of a photoelectric coupler according to claim 4, wherein: Determining a temperature-voltage drop characteristic curve according to the voltage drop and the test temperature includes: The temperature-voltage drop characteristic curve is obtained by linearly fitting the multiple sets of temperature data and the corresponding voltage drops.

6. The method for testing thermal resistance of a photoelectric coupler according to claim 3, wherein: Determining the junction temperature of the optocoupler at different test powers according to the temperature-voltage drop characteristic curve includes: controlling the first test current and the second test current of the photoelectric coupler to remain unchanged, and obtaining the instantaneous voltage drop of the photoelectric coupler under different test powers; The junction temperature of the optocoupler is determined according to the instantaneous voltage drop and the temperature-voltage drop characteristic curve.

7. The method for testing thermal resistance of a photoelectric coupler according to claim 1, wherein: The thermal resistance of the optocoupler is determined based on the relationship between the junction temperature and the test power, using the following formula: Among them, R thJ-A is the thermal resistance of the optocoupler, T J is the junction temperature of the optocoupler, T A is the ambient temperature during the test, and P is the test power of the photoelectric coupler.

8. The method for testing the thermal resistance of a photoelectric coupler according to claim 3, wherein: The first test current of the photoelectric coupler is less than 1 / 10 of the maximum output current of the photoelectric coupler.

9. The method for testing thermal resistance of a photoelectric coupler according to claim 1, wherein: The test power is greater than or equal to ten times the dissipated power of the input end of the optocoupler.

10. A thermal resistance test device for a photoelectric coupler, characterized in that: The thermal resistance test of the photoelectric coupler is performed using the thermal resistance test method of the photoelectric coupler according to any one of claims 1 to 9.

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