A parallel external current sensing circuit and method

Abstract

The application relates to a parallel external current detection circuit and method, wherein the circuit comprises a probe module, a constant voltage load module and a control module. The probe module obtains a first initial voltage value of a first test end of a mainboard to be tested and a second initial voltage value of a second test end; the constant voltage load module is provided with a sampling resistor, a load is pulled at the second test end according to a reference voltage, a pull load current of the sampling resistor is obtained, the probe module obtains a first pull load voltage value of the first test end of the mainboard to be tested and a second pull load voltage value of the second test end; the control module calculates a test current according to the first initial voltage value, the second initial voltage value, the second pull load voltage value and the pull load current; the test current of the mainboard to be tested is determined without adopting a method of cutting the copper foil of the mainboard and connecting the sampling resistor in series in a mainboard test circuit, so that irreparable damage to the mainboard is avoided, and material cost and wiring difficulty are reduced.

Description

Technical Field

[0001] This invention belongs to the field of detection circuits, specifically relating to a parallel external current detection circuit and method. Background Technology

[0002] There are two main methods for testing the current of a motherboard power supply: one is the series current measurement method based on Ohm's law, which requires a sampling resistor to be connected in series in the circuit. The current passing through the sampling resistor is calculated using the voltage and resistance of the sampling resistor, and then the current of the motherboard power supply is obtained; the other is the electromagnetic induction current measurement method based on the principle of electromagnetics.

[0003] Series-based current measurement requires a sampling resistor in series, but considering cost and motherboard space, it's not feasible to connect a sampling resistor in series for every power supply on the motherboard. Electromagnetic induction current measurement requires the power cable to be clamped in a current clamp and can only measure power supply ports on the motherboard that have power cables connected to them.

[0004] In addition, motherboard testing often requires measuring the power supply current on the motherboard. If there is no series sampling resistor, the copper foil on the motherboard needs to be cut open before using the series current detection method, which will cause irreparable damage to the motherboard. Summary of the Invention

[0005] Aimed at at least in solving one of the technical problems existing in the prior art, the present invention provides a parallel external current detection circuit and method, which improves the convenience of detecting the current of the motherboard.

[0006] A first aspect of the present invention provides a parallel external current detection circuit, comprising:

[0007] The probe module is used to acquire the first initial voltage value of the first test terminal and the second initial voltage value of the second test terminal of the motherboard under test.

[0008] A constant voltage load module is provided, wherein the constant voltage load module is provided with a sampling resistor, and the constant voltage load module is used to apply a load to the second test terminal according to a reference voltage and obtain the load current through the sampling resistor. The probe module is used to obtain the second load voltage value of the second test terminal of the motherboard under test, wherein the reference voltage is set according to the second initial voltage value.

[0009] The control module is used to calculate the test current of the motherboard under test based on the first initial voltage value, the second initial voltage value, the second load voltage value, and the load current.

[0010] According to certain embodiments of the first aspect of the present invention, the detection circuit further includes a reference voltage module for providing a reference voltage to the constant voltage load module, wherein the reference voltage is equal to the reference voltage.

[0011] According to certain embodiments of the first aspect of the present invention, the control module is provided with a first pin and a second pin, the control module is used to compare the current reference voltage and the reference voltage to obtain a reference voltage control signal, the first pin is used to receive the current reference voltage, and the second pin is used to output the reference voltage control signal.

[0012] According to certain embodiments of the first aspect of the present invention, the reference voltage module includes a first MOS transistor and a second MOS transistor, the gate of the first MOS transistor is used to receive the reference voltage control signal, the drain of the first MOS transistor is connected to the gate of the second MOS transistor, and the drain of the second MOS transistor is used to output the reference voltage.

[0013] According to certain embodiments of the first aspect of the present invention, the constant voltage load module includes a third MOSFET, a fourth MOSFET, a fifth MOSFET, and a comparator. The gate of the third MOSFET is used to receive a switching signal, the drain of the third MOSFET is connected to the gate of the fourth MOSFET, one input terminal of the comparator is connected to the drain of the fourth MOSFET, the other input terminal of the comparator is used to receive the reference voltage, the drain of the fourth MOSFET is connected to the drain of the fifth MOSFET, the output terminal of the comparator is connected to the gate of the fifth MOSFET, and the source of the fifth MOSFET is connected to the sampling resistor.

[0014] A second aspect of the present invention provides a parallel external current detection method, employing a parallel external current detection circuit as described in the first aspect of the present invention, the detection method comprising:

[0015] Obtain the first initial voltage value of the first test terminal and the second initial voltage value of the second test terminal of the motherboard under test;

[0016] Based on the reference voltage, a load is applied to the second test terminal to obtain the load current passing through the sampling resistor and the second load voltage value of the second test terminal;

[0017] The test current of the motherboard under test is calculated based on the first initial voltage value, the second initial voltage value, the second load voltage value, and the load current.

[0018] The reference voltage is set according to the second initial voltage value.

[0019] According to certain embodiments of the second aspect of the present invention, before the load is applied to the second test terminal according to the reference voltage, the detection method includes:

[0020] Determine the numerical relationship between the first initial voltage value and the second initial voltage value;

[0021] When the second initial voltage value is less than or equal to a first preset ratio of the first initial voltage value, the detection stops.

[0022] According to certain embodiments of the second aspect of the present invention, the reference voltage is set as a second preset ratio of the second initial voltage value; the second preset ratio is different in different loading cycles, and the reference voltage is different.

[0023] According to certain embodiments of the second aspect of the present invention, obtaining the load current through the sampling resistor includes:

[0024] The voltage value of the sampling resistor is measured;

[0025] The load current passing through the sampling resistor is obtained based on the voltage value and the resistance value of the sampling resistor.

[0026] According to certain embodiments of the second aspect of the present invention, the step of calculating the test current of the motherboard under test based on the first initial voltage value, the second initial voltage value, the second load voltage value, and the load current includes:

[0027] The first quotient is obtained by dividing the difference between the first initial voltage value and the second initial voltage value by the difference between the second initial voltage value and the second load voltage value.

[0028] The test current of the motherboard under test is obtained by multiplying the load current by the first quotient.

[0029] The beneficial effects of this invention include: the parallel external current detection circuit eliminates the need to cut the copper foil of the motherboard and connect a sampling resistor in series in the motherboard test circuit to determine the test current of the motherboard under test, avoiding irreparable damage to the motherboard, reducing material costs and wiring difficulty; the parallel external current detection circuit can be applied to the measurement of motherboard copper foil current and cable current, improving the versatility of application scenarios; and the integrated module allows for outdoor use, improving measurement convenience.

[0030] Furthermore, additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0031] Figure 1This is a structural diagram of the parallel external current detection circuit provided in an embodiment of the present invention;

[0032] Figure 2 This is a flowchart illustrating the steps of the parallel external current detection method provided in an embodiment of the present invention;

[0033] Figure 3 This is a circuit diagram of the reference voltage module provided in an embodiment of the present invention;

[0034] Figure 4 This is a circuit diagram of a constant voltage load module provided in an embodiment of the present invention;

[0035] Figure 5 This is a circuit diagram of the control module provided in an embodiment of the present invention. Detailed Implementation

[0036] The following will provide a clear and complete description of the concept, specific structure, and technical effects of the present invention in conjunction with the embodiments and accompanying drawings, so as to fully understand the purpose, solution, and effects of the present invention. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0037] It should be noted that, unless otherwise specified, when a feature is referred to as "fixed" or "connected" to another feature, it can be directly fixed or connected to the other feature, or indirectly fixed or connected to the other feature. Furthermore, the descriptions of "upper," "lower," "left," "right," "top," and "bottom" used in this invention are only relative to the relative positional relationships of the various components of the invention in the accompanying drawings.

[0038] Furthermore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this specification is for the purpose of describing particular embodiments only and not for limiting the invention. The term "and / or" as used herein includes any combination of one or more of the associated listed items.

[0039] Conventional methods for testing motherboard power supply current mainly include two approaches: one is the series current measurement method based on Ohm's law, which requires a sampling resistor connected in series in the circuit. The current passing through the sampling resistor is calculated using the voltage and resistance of the sampling resistor, thus obtaining the motherboard power supply current. The other approach is the electromagnetic induction current measurement method based on electromagnetic principles. The series current measurement method requires a sampling resistor in series, but considering cost and motherboard space, it's not feasible to have a sampling resistor in series for every power supply circuit on the motherboard. The electromagnetic induction current measurement method requires placing the power cable in a current clamp and can only measure power supply ports on the motherboard with power cables. Furthermore, motherboard testing often requires measuring the power supply current on the motherboard itself. Without a series sampling resistor, the motherboard's copper foil would need to be cut open to use the series current detection method, causing irreparable damage to the motherboard.

[0040] To address the above problems, embodiments of the present invention provide a parallel external current detection circuit and method, which can avoid irreparable damage to the motherboard and reduce material costs and wiring difficulty.

[0041] The embodiments of this application will be further described below with reference to the accompanying drawings.

[0042] Reference Figure 1 The parallel external current detection circuit includes: a probe module, a constant voltage load module, and a control module.

[0043] The system comprises the following modules: a probe module for acquiring the first initial voltage value at the first test terminal and the second initial voltage value at the second test terminal of the motherboard under test; a constant voltage load module with a sampling resistor R3 for applying a load to the second test terminal based on a reference voltage and acquiring the load current passing through the sampling resistor R3; and a probe module for acquiring the first load voltage value at the first test terminal and the second load voltage value at the second test terminal of the motherboard under test. The control module calculates the test current of the motherboard under test based on the first initial voltage value, the second initial voltage value, the second load voltage value, and the load current. The reference voltage is set based on the second initial voltage value.

[0044] In this embodiment, the copper foil path of the motherboard under test is selected, and the entry voltage test point and exit voltage test point are determined based on the copper foil path. Generally, the power output terminal is selected as the entry voltage test point, and the load terminal is selected as the exit voltage test point. The entry voltage test point is the first test terminal of the motherboard under test, and the exit voltage test point is the second test terminal of the motherboard under test.

[0045] The probe module has two probes. One probe is connected to the first test terminal of the motherboard under test, and the other probe is connected to the second test terminal of the motherboard under test. The first initial voltage value of the first test terminal and the second initial voltage value of the second test terminal of the motherboard under test are recorded.

[0046] The control module sets the reference voltage based on the second initial voltage value. The constant voltage load module applies a load to the second test terminal based on the reference voltage. The load current passing through the sampling resistor R3 of the constant voltage load module is measured. The first load voltage value of the first test terminal and the second load voltage value of the second test terminal of the motherboard under test are measured through the probe module.

[0047] The first initial voltage value, the second initial voltage value, the second load voltage value, and the load current are input to the control module. The control module calculates the test current of the motherboard under test based on the first initial voltage value, the second initial voltage value, the second load voltage value, and the load current.

[0048] This parallel external current detection circuit eliminates the need to cut the motherboard copper foil and connect a sampling resistor R3 in series in the motherboard test circuit to determine the test current of the motherboard under test, avoiding irreparable damage to the motherboard, reducing material costs and wiring difficulty. This parallel external current detection circuit can be used to measure the current of motherboard copper foil and cable current, improving the versatility of application scenarios. The integrated module can be used outdoors, improving the convenience of measurement.

[0049] Reference Figure 1 In some embodiments, the detection circuit further includes a reference voltage module, which provides a reference voltage to the constant voltage load module, wherein the reference voltage is equal to the base voltage. Since the base voltage is set based on a second initial voltage value and differs in different load cycles, the reference voltage module needs to provide a stable reference voltage to the constant voltage load module, i.e., a stable base voltage.

[0050] The control module has a first pin and a second pin. The control module is used to compare the current reference voltage and the reference voltage to obtain the reference voltage control signal. The first pin is used to receive the current reference voltage, and the second pin is used to output the reference voltage control signal.

[0051] Reference Figure 3 The reference voltage module includes a first MOSFET Q0 and a second MOSFET Q1. The gate of the first MOSFET Q0 receives the reference voltage control signal, and the drain of the first MOSFET Q0 is connected to the gate of the second MOSFET Q1. The drain of the second MOSFET Q1 outputs the reference voltage. Additionally, the drain of the first MOSFET Q0 is connected to one end of a resistor R0, and the source of the first MOSFET Q0 is grounded. The drain of the second MOSFET Q1 is connected to one end of a resistor R1, and the other end of the resistor R1 outputs the reference voltage. The other end of the resistor R0 is connected to the first test terminal, and the source of the second MOSFET Q1 is also connected to the first test terminal. Specifically, the first MOSFET Q0 is an NMOS transistor, and the second MOSFET Q1 is a PMOS transistor.

[0052] In this embodiment, the control module compares the current reference voltage with the reference voltage. When the reference voltage is less than the reference voltage, the reference voltage control signal is pulled high, the first MOSFET Q0 is turned on, the second MOSFET Q1 is turned on, and the reference voltage rises until the reference voltage and the reference voltage are equal. When the reference voltage is greater than the reference voltage, the reference voltage control signal is pulled low, the first MOSFET Q0 is turned off, the second MOSFET Q1 is turned off, and the reference voltage falls until the reference voltage and the reference voltage are equal.

[0053] Reference Figure 4 In some embodiments, the constant voltage load module includes a third MOSFET Q4, a fourth MOSFET Q2, a fifth MOSFET Q3, and a comparator. The gate of the third MOSFET Q4 is used to receive a switching signal, and the drain of the third MOSFET Q4 is connected to the gate of the fourth MOSFET Q2. One input terminal of the comparator is connected to the drain of the fourth MOSFET Q2, and the other input terminal of the comparator is used to receive a reference voltage. The drain of the fourth MOSFET Q2 is connected to the drain of the fifth MOSFET Q3, and the output terminal of the comparator is connected to the gate of the fifth MOSFET Q3. The source of the fifth MOSFET Q3 is connected to a sampling resistor R3. Additionally, the control module has a third pin for sending switching signals. The source of the third MOSFET Q4 is connected to one end of resistor R4, and the other end of resistor R4 is connected to a second test terminal. The source of the fourth MOSFET Q2 is also connected to the second test terminal. A resistor R2 is connected between one input terminal of the comparator and the drain of the fourth MOSFET Q2. The connection point between the sampling resistor R3 and the source of the fifth MOSFET Q3 is the voltage output terminal of the sampling resistor R3, and the other end of the sampling resistor R3 is grounded. Specifically, the third MOSFET Q4 is an NMOS transistor, the fourth MOSFET Q2 is a PNOS transistor, and the fifth MOSFET Q3 is an NMOS transistor.

[0054] In this embodiment, the control module pulls a high switching signal, turning on the third MOSFET Q4 and the fourth MOSFET Q2. A comparator compares the voltage at the second test terminal with a reference voltage. When the voltage at the second test terminal is greater than the reference voltage, the comparator's output level increases, strengthening the conduction of the fifth MOSFET Q3. Conversely, when the voltage at the second test terminal decreases until it falls below the reference voltage, the comparator's output level decreases, reducing the conduction of the fifth MOSFET Q3. This cycle continues until the second load voltage at the second test terminal equals the reference voltage. The fourth pin of the control module is connected to the voltage output of the sampling resistor R3. The voltage value of the sampling resistor R3 is measured, and the load current is calculated based on the voltage value and the set resistance value of the sampling resistor R3.

[0055] It should be noted that energy is consumed through the load MOSFET, and multiple MOSFETs need to be connected in parallel and heat dissipation devices need to be added depending on the actual situation.

[0056] Reference Figure 5 The control module is powered by a battery. It receives the required voltage data from the ADC interface, calculates the control and display signals internally, and outputs the control and display signals through the IO interface.

[0057] The fifth pin of the control module is connected to the first test terminal, and the sixth pin of the control module is connected to the second test terminal.

[0058] An embodiment of the present invention provides a parallel external current detection method, which applies the parallel external current detection circuit described above.

[0059] Reference Figure 2 The parallel external current detection method includes the following steps:

[0060] Step S100: Obtain the first initial voltage value of the first test terminal and the second initial voltage value of the second test terminal of the motherboard under test.

[0061] Step S200: Apply a load to the second test terminal based on the reference voltage, and obtain the load current through the sampling resistor, the first load voltage value of the first test terminal, and the second load voltage value of the second test terminal.

[0062] Step S300: Calculate the test current of the motherboard under test based on the first initial voltage value, the second initial voltage value, the second load voltage value, and the load current.

[0063] The reference voltage is set according to the second initial voltage value.

[0064] In some embodiments, the detection method includes the following steps before applying a load to the second test terminal based on a reference voltage:

[0065] Determine the numerical relationship between the first initial voltage value and the second initial voltage value;

[0066] When the second initial voltage value is less than or equal to a first preset ratio of the first initial voltage value, the detection stops.

[0067] According to certain embodiments of the second aspect of the invention, the reference voltage is set as a second preset ratio of the second initial voltage value; the second preset ratio is different in different loading cycles, and the reference voltage is different.

[0068] In some embodiments, obtaining the load current through the sampling resistor R3 includes the following steps:

[0069] The voltage value of sampling resistor R3 was measured;

[0070] Based on the voltage and resistance values ​​of sampling resistor R3, the load current passing through sampling resistor R3 can be obtained.

[0071] In some embodiments, the test current of the motherboard under test is calculated based on a first initial voltage value, a second initial voltage value, a second load voltage value, and a load current, including the following steps:

[0072] The first quotient is obtained by dividing the difference between the first initial voltage value and the second initial voltage value by the difference between the second initial voltage value and the second load voltage value.

[0073] Multiply the load current by the first quotient to obtain the test current of the motherboard under test.

[0074] In one specific embodiment, a probe module acquires a first initial voltage value at a first test terminal and a second initial voltage value at a second test terminal of the motherboard under test. A control module receives the first initial voltage value at the first test terminal and the second initial voltage value at the second test terminal via an ADC interface.

[0075] Set the initial parameters as follows: reference voltage = 99% * second initial voltage; total test current = 0; total number of tests q = 0; number of tests for a single set voltage n = 0; voltage drop count m = 0; sampling resistor R3 internal resistance = 0.5. Input the initial parameters into the control module.

[0076] The system determines the numerical relationship between a first initial voltage value and a second initial voltage value. If the second initial voltage value is less than or equal to a first preset percentage of the first initial voltage value, the detection stops. The first preset percentage is set to 95%. Specifically, when the second initial voltage value is less than or equal to 95% of the first initial voltage value, the switch signal is turned off. It also determines whether the total number of tests, q, is greater than 0. If the total number of tests, q, is less than or equal to 0, a display signal outputting the message "Voltage less than minimum value, test failed" is sent. If the total number of tests, q, is greater than 0, a display signal outputting the message "Test current = value A", where value A is the result of the test current.

[0077] Understandably, the default minimum power supply voltage cannot be less than 95% of the default value. If it is less than or equal to 95% of the default value, the test needs to be stopped. The default value can be set according to the actual situation. If the second initial voltage value is less than or equal to 95% of the first initial voltage value and the total number of tests q is less than or equal to 0, it indicates that the voltage was already below the minimum value before the test and does not meet the test requirements.

[0078] The number of tests for a single set voltage, n, increments by 1. It checks if the number of tests n is greater than 5. If so, after 5 tests, the reference voltage decreases, and the load is increased. If the number of tests n is less than or equal to 5, the reference voltage remains unchanged. If the number of tests n is greater than 5, the reference voltage decreases by 1% of the second initial voltage value each time, and the voltage drop count m increments by 1. The reference voltage is then determined.

[0079] The control module compares the current reference voltage with the base voltage. When the reference voltage is lower than the base voltage, the reference voltage control signal is pulled high, and the reference voltage output by the reference voltage module increases until the reference voltage and base voltage are equal. When the reference voltage is higher than the base voltage, the reference voltage control signal is pulled low, and the reference voltage output by the reference voltage module decreases until the reference voltage and base voltage are equal.

[0080] The control module sends a switching signal to start the constant voltage load module.

[0081] The timing is set for 2000ms, and the load is applied for 2 seconds to stabilize various voltage values. The load duration can be set according to actual conditions.

[0082] The voltage value of sampling resistor R3 is measured; the control module calculates the load current through sampling resistor R3 based on the voltage and resistance values ​​of R3. Specifically, according to Ohm's law, the load current through sampling resistor R3 is equal to the quotient of the voltage value of sampling resistor R3 divided by the resistance value of sampling resistor R3. That is: Load current through sampling resistor R3 = Voltage value of sampling resistor R3 / Resistance value of sampling resistor R3.

[0083] The control module divides the difference between the first initial voltage value and the second initial voltage value by the difference between the second initial voltage value and the second load voltage value to obtain the first quotient value; the load current is multiplied by the first quotient value to obtain the test current of the motherboard under test. That is: Test current = Load current * (first initial voltage value - second initial voltage value) / (second initial voltage value - second load voltage value).

[0084] The total number of tests, q, is incremented by 1.

[0085] Calculate the following data: Total test current = Previous total test current + Current test current; Average test current = Total test current / q. Averaging the results of each test increases test accuracy.

[0086] The above description is merely a preferred embodiment of the present invention. The present invention is not limited to the above-described embodiments. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this disclosure, as long as they achieve the same technical effects, should be included within the scope of protection of this disclosure and fall under the protection scope of the present invention. Within the protection scope of the present invention, the technical solutions and / or implementation methods can have various modifications and variations.

Claims

1. A parallel type external current detection circuit, characterized by comprising: The parallel external current detection circuit comprises: a probe module, which is used to acquire a first initial voltage value of a first test end and a second initial voltage value of a second test end of a mainboard to be tested; a constant voltage load module, which is provided with a sampling resistor and is used to pull load at the second test end according to a reference voltage, acquire a pull load current passing through the sampling resistor, and acquire a second pull load voltage value of the second test end of the mainboard to be tested, wherein the reference voltage is set according to the second initial voltage value; a control module, which is used to calculate a test current of the mainboard to be tested according to the first initial voltage value, the second initial voltage value, the second pull load voltage value and the pull load current; the control module is specifically used to divide the difference between the first initial voltage value and the second initial voltage value by the difference between the second initial voltage value and the second pull load voltage value to obtain a first quotient value, and multiply the pull load current by the first quotient value to obtain the test current of the mainboard to be tested; the probe module has two probes, one of the probes of the probe module is connected with the first test end of the mainboard to be tested, and the other probe of the probe module is connected with the second test end of the mainboard to be tested.

2. The shunt external current sense circuit of claim 1, wherein, The detection circuit further comprises a reference voltage module, which is used to provide a reference voltage for the constant voltage load module, wherein the reference voltage is equal to the reference voltage.

3. The shunt external current sense circuit of claim 2, wherein, The control module is provided with a first pin and a second pin, the control module is used to compare the current reference voltage with the reference voltage to obtain a reference voltage control signal, the first pin is used to receive the current reference voltage, and the second pin is used to output the reference voltage control signal.

4. The shunt external current sense circuit of claim 3, wherein, The reference voltage module comprises a first MOS tube and a second MOS tube, a gate of the first MOS tube is used to receive the reference voltage control signal, a drain of the first MOS tube is connected with a gate of the second MOS tube, and a drain of the second MOS tube is used to output the reference voltage; a source of the first MOS tube is grounded, and a source of the second MOS tube is connected with the first test end.

5. The shunt external current sense circuit of claim 1, wherein, The constant voltage load module comprises a third MOS tube, a fourth MOS tube, a fifth MOS tube and a comparator, a gate of the third MOS tube is used to receive a switching signal, a drain of the third MOS tube is connected with a gate of the fourth MOS tube, one input end of the comparator is connected with a drain of the fourth MOS tube, another input end of the comparator is used to receive a reference voltage, a drain of the fourth MOS tube is connected with a drain of the fifth MOS tube, an output end of the comparator is connected with a gate of the fifth MOS tube, a source of the fifth MOS tube is connected with the sampling resistor, a source of the third MOS tube is connected with one end of a fourth resistor, and a source of the fourth MOS tube is connected with the second test end.

6. A parallel external current detection method, characterized by, The detection method comprises: acquiring a first initial voltage value of a first test end and a second initial voltage value of a second test end of a mainboard to be tested; According to the reference voltage, a pull load is performed on the second test terminal, a pull load current passing through the sampling resistor and a second pull load voltage value of the second test terminal are obtained; According to the first initial voltage value, the second initial voltage value, the second pull load voltage value and the pull load current, a test current of the mainboard to be tested is calculated. The reference voltage is set according to the second initial voltage value.

7. The shunt external current sensing method of claim 6, wherein, Before the pull load is performed on the second test terminal according to the reference voltage, the detection method comprises: judging a numerical relationship between the first initial voltage value and the second initial voltage value; when the second initial voltage value is less than or equal to a first preset proportion of the first initial voltage value, stopping the detection.

8. The shunt-type external current sensing method according to claim 6, wherein The reference voltage is set as a second preset proportion of the second initial voltage value; in different pull load rounds, the second preset proportion is different, and the reference voltage is different.

9. The shunt-type external current sensing method according to claim 6, wherein The pull load current passing through the sampling resistor comprises: measuring a voltage value of the sampling resistor; according to the voltage value of the sampling resistor and a resistance value of the sampling resistor, the pull load current passing through the sampling resistor is obtained.

10. The shunt-type external current sensing method according to claim 6, wherein The calculation of the test current of the mainboard to be tested according to the first initial voltage value, the second initial voltage value, the second pull load voltage value and the pull load current comprises: dividing a difference between the first initial voltage value and the second initial voltage value by a difference between the second initial voltage value and the second pull load voltage value to obtain a first quotient value; multiplying the pull load current by the first quotient value to obtain the test current of the mainboard to be tested.

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