Parallel external current detection circuit and method

Abstract

The invention relates to a parallel external current detection circuit and method. 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 and a second initial voltage value of a second test end of the mainboard to be tested; the constant-voltage load module is provided with a sampling resistor, load pulling is carried out at the second test end according to the reference voltage, load pulling current of the sampling resistor is obtained, and the probe module obtains a first load pulling voltage value of the first test end and a second load pulling voltage value of the second test end of the mainboard to be tested; the control module calculates a test current according to the first initial voltage value, the second initial voltage value, the second load pulling voltage value and the load pulling current; the test current of the mainboard to be tested does not need to be determined by cutting a mainboard copper foil and connecting a sampling resistor in a mainboard test circuit in series, so that irreparable damage to the mainboard is avoided, and the material cost and the wiring difficulty are reduced.

Description

Technical Field

[0001] The invention belongs to the field of detection circuits, and in particular relates to a parallel external current detection circuit and method. Background Art

[0002] Conventional current testing methods for motherboard power supplies mainly include two methods; one method is a series current measurement method based on Ohm's law, which requires connecting a sampling resistor in series in the circuit, and using the voltage and resistance of the sampling resistor to calculate the current passing through the sampling resistor, and then obtain the current of the motherboard power supply; the other method is an electromagnetic induction current measurement method based on the principle of electromagnetism.

[0003] The series current measurement method requires a sampling resistor to be connected in series, but considering the cost and motherboard space, a sampling resistor cannot be connected in series to each power supply on the motherboard. The electromagnetic induction current measurement method requires the power cord to be placed in a current clamp, and can only measure the power supply port with a power cord on the motherboard.

[0004] In addition, it is often necessary to measure the current of the power supply on the motherboard during motherboard testing. If there is no series sampling resistor, it is necessary to cut the copper foil of the motherboard and then use the series current detection method, which will cause irreparable damage to the motherboard. Summary of the invention

[0005] Aiming to solve at least 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 mainboard.

[0006] An embodiment of the first aspect of the present invention provides a parallel external current detection circuit, comprising: A probe module, the probe module is used to obtain a first initial voltage value of a first test terminal and a second initial voltage value of a second test terminal of the motherboard to be tested; A constant voltage load module, wherein the constant voltage load module is provided with a sampling resistor, and the constant voltage load module is used to pull a load at the second test end according to a reference voltage to obtain a pull current passing through the sampling resistor, and the probe module is used to obtain a second pull voltage value of the second test end of the motherboard to be tested, wherein the reference voltage is set according to the second initial voltage value; A control module 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 load voltage value and the load current.

[0007] According to some embodiments of the first aspect of the present invention, the detection circuit further includes 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 base voltage.

[0008] 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, and 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.

[0009] According to certain embodiments of the first aspect of the present invention, the reference voltage module includes a first MOS tube and a second MOS tube, the gate of the first MOS tube is used to receive the reference voltage control signal, the drain of the first MOS tube is connected to the gate of the second MOS tube, and the drain of the second MOS tube is used to output the reference voltage.

[0010] According to certain embodiments of the first aspect of the present invention, the constant voltage load module includes a third MOS tube, a fourth MOS tube, a fifth MOS tube and a comparator, the gate of the third MOS tube is used to receive a switching signal, the drain of the third MOS tube is connected to the gate of the fourth MOS tube, one of the input ends of the comparator is connected to the drain of the fourth MOS tube, the other input end of the comparator is used to receive the reference voltage, the drain of the fourth MOS tube is connected to the drain of the fifth MOS tube, the output end of the comparator is connected to the gate of the fifth MOS tube, and the source of the fifth MOS tube is connected to the sampling resistor.

[0011] An embodiment of the second aspect of the present invention provides a parallel external current detection method, using the parallel external current detection circuit as described in the embodiment of the first aspect of the present invention, the detection method comprises: Obtain a first initial voltage value of a first test terminal and a second initial voltage value of a second test terminal of the motherboard to be tested; Loading the second test end according to the reference voltage to obtain a load current passing through the sampling resistor and a second load voltage value of the second test end; Calculate the test current of the motherboard to be tested according to the first initial voltage value, the second initial voltage value, the second load voltage value and the load current; Wherein, the reference voltage is set according to the second initial voltage value.

[0012] According to some embodiments of the second aspect of the present invention, before loading the second test terminal according to the reference voltage, the detection method includes: determining 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 ratio of the first initial voltage value, detection is stopped.

[0013] According to some embodiments of the second aspect of the present invention, the reference voltage is set to a second preset ratio of the second initial voltage value; in different loading rounds, the second preset ratio is different and the reference voltage is different.

[0014] According to some embodiments of the second aspect of the present invention, obtaining the load current passing through the sampling resistor includes: Measure and obtain the voltage value of the sampling resistor; The load current passing through the sampling resistor is obtained according to the voltage value of the sampling resistor and the resistance value of the sampling resistor.

[0015] According to some embodiments of the second aspect of the present invention, the step of calculating the test current of the motherboard to be tested according to the first initial voltage value, the second initial voltage value, the second load voltage value, and the load current includes: 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 to obtain a first quotient value; The load current is multiplied by the first quotient to obtain a test current of the mainboard to be tested.

[0016] The beneficial effects of the present invention include: through the parallel external current detection circuit, there is no need to use the method of cutting the copper foil of the mainboard and connecting a sampling resistor in series in the mainboard test circuit to determine the test current of the mainboard to be tested, thereby avoiding irreparable damage to the mainboard and reducing material costs and wiring difficulty; the parallel external current detection circuit can be applied to the measurement of the copper foil current of the mainboard and the cable current, thereby improving the wide range of scene applications; the module is integrated and can be used outdoors, thereby improving the convenience of measurement.

[0017] In addition, additional aspects and advantages of the present invention will be given in part in the following description, and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a structural diagram of a parallel external current detection circuit provided by an embodiment of the present invention; Figure 2 is a step diagram of a parallel external current detection method provided by an embodiment of the present invention; Figure 3 is a circuit diagram of a reference voltage module provided by an embodiment of the present invention; Figure 4 is a circuit diagram of a constant voltage load module provided by an embodiment of the present invention; Figure 5 is a circuit diagram of a control module provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0019] The following will be combined with the embodiments and drawings to clearly and completely describe the concept, specific structure and technical effects of the present invention, so as to fully understand the purpose, scheme and effect of the present invention. It should be noted that the embodiments and features in the embodiments of this application can be combined with each other without conflict.

[0020] It should be noted that, unless otherwise specified, when a feature is referred to as being "fixed" or "connected" to another feature, it may be directly fixed or connected to the other feature, or it may be indirectly fixed or connected to the other feature. In addition, the descriptions of up, down, left, right, top, bottom, etc. used in the present invention are only relative to the relative positional relationship of the components of the present invention in the drawings.

[0021] In addition, unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art. The terms used in this specification are only for describing specific embodiments, not for limiting the present invention. The term "and / or" used herein includes any combination of one or more related listed items.

[0022] Conventional current testing methods for motherboard power supplies mainly include two methods; one method is a series current measurement method based on Ohm's law, which requires a sampling resistor to be connected in series in the circuit, and 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 method is an electromagnetic induction current measurement method based on the principle of electromagnetism. The series current measurement method requires a sampling resistor to be connected in series, but considering the cost and motherboard space, a sampling resistor cannot be connected in series to each power supply on the motherboard. The electromagnetic induction current measurement method requires the power cord to be placed in a current clamp, and can only measure the power supply port with a power cord on the motherboard. In addition, it is often necessary to measure the current of the power supply on the motherboard during motherboard testing. If there is no series sampling resistor, it is necessary to cut the motherboard copper foil and then use the series current detection method, which will cause irreparable damage to the motherboard.

[0023] In order to solve the above problems, an embodiment of the present invention provides a parallel external current detection circuit and method, which can avoid irreparable damage to the mainboard and reduce material costs and wiring difficulty.

[0024] The embodiments of the present application are further described below in conjunction with the accompanying drawings.

[0025] Reference Figure 1 , a parallel external current detection circuit includes: a probe module, a constant voltage load module and a control module.

[0026] Among them, the probe module is used to obtain the first initial voltage value of the first test end of the motherboard to be tested and the second initial voltage value of the second test end; the constant voltage load module is provided with a sampling resistor R3, the constant voltage load module is used to pull a load at the second test end according to the reference voltage, and obtain the pull current passing through the sampling resistor R3, the probe module is used to obtain the first pull voltage value of the first test end of the motherboard to be tested and the second pull voltage value of the second test end; the control module is used to calculate the test current of the motherboard to be tested according to the first initial voltage value, the second initial voltage value, the second pull voltage value and the pull current. The reference voltage is set according to the second initial voltage value.

[0027] In this embodiment, a copper foil path of the motherboard to be tested is selected on the motherboard, and an entry voltage test point and an exit voltage test point are determined according to the copper foil path of the motherboard to be tested. Generally, the power output end is selected as the entry voltage test point, and the load end is selected as the exit voltage test point. The entry voltage test point is the first test end of the motherboard to be tested, and the exit voltage test point is the second test end of the motherboard to be tested.

[0028] The probe module has two probes, one of which is connected to the first test end of the motherboard to be tested, and the other is connected to the second test end of the motherboard to be tested. The first initial voltage value of the first test end and the second initial voltage value of the second test end of the motherboard to be tested are recorded.

[0029] The control module sets a reference voltage according to the second initial voltage value, and the constant voltage load module loads at the second test end according to the reference voltage. The load current passing through the sampling resistor R3 of the constant voltage load module is measured, and the first load voltage value of the first test end and the second load voltage value of the second test end of the motherboard to be tested are measured through the probe module.

[0030] The first initial voltage value, the second initial voltage value, the second load voltage value and the load current are input into the control module, and the control module calculates the test current of the motherboard to be tested according to the first initial voltage value, the second initial voltage value, the second load voltage value and the load current.

[0031] The parallel external current detection circuit eliminates the need to cut the copper foil of the motherboard and connect a sampling resistor R3 in series in the motherboard test circuit to determine the test current of the motherboard to be tested, thereby avoiding irreparable damage to the motherboard and reducing material costs and wiring difficulty. The parallel external current detection circuit can be applied to the measurement of the copper foil current of the motherboard and the cable current, thereby improving the breadth of scene applications. The module is integrated and can be used outdoors, thereby improving measurement convenience.

[0032] Reference Figure 1In some embodiments, the detection circuit further includes 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. Since the reference voltage is set according to the second initial voltage value, and the reference voltage is different in different loading rounds, it is necessary to provide a stable reference voltage for the constant voltage load module through the reference voltage module, that is, to provide a stable reference voltage.

[0033] 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 base 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.

[0034] Reference Figure 3 The reference voltage module includes a first MOS tube Q0 and a second MOS tube Q1. The gate of the first MOS tube Q0 is used to receive a reference voltage control signal. The drain of the first MOS tube Q0 is connected to the gate of the second MOS tube Q1, and the drain of the second MOS tube Q1 is used to output a reference voltage. In addition, the drain of the first MOS tube Q0 is also connected to one end of the resistor R0, and the source of the first MOS tube Q0 is grounded; the drain of the second MOS tube Q1 is connected to one end of the resistor R1, and the other end of the resistor R1 outputs a reference voltage. The other end of the resistor R0 is connected to the first test end, and the source of the second MOS tube Q1 is connected to the first test end. Specifically, the first MOS tube Q0 is an NMOS tube, and the second MOS tube Q1 is a PMOS tube.

[0035] In this embodiment, the control module compares the current reference voltage and the reference voltage. When the reference voltage is less than the reference voltage, the reference voltage control signal is pulled high, the first MOS tube Q0 is turned on, the second MOS tube 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 MOS tube Q0 is turned off, the second MOS tube Q1 is turned off, and the reference voltage decreases until the reference voltage and the reference voltage are equal.

[0036] Reference Figure 4In some embodiments, the constant voltage load module includes a third MOS tube Q4, a fourth MOS tube Q2, a fifth MOS tube Q3 and a comparator, the gate of the third MOS tube Q4 is used to receive a switch signal, the drain of the third MOS tube Q4 is connected to the gate of the fourth MOS tube Q2, one of the input terminals of the comparator is connected to the drain of the fourth MOS tube Q2, the other input terminal of the comparator is used to receive a reference voltage, the drain of the fourth MOS tube Q2 is connected to the drain of the fifth MOS tube Q3, the output terminal of the comparator is connected to the gate of the fifth MOS tube Q3, and the source of the fifth MOS tube Q3 is connected to the sampling resistor R3. In addition, the control module is provided with a third pin, and the third pin is used to send a switch signal. The source of the third MOS tube Q4 is connected to one end of the resistor R4, the other end of the resistor R4 is connected to the second test end, and the source of the fourth MOS tube Q2 is connected to the second test end. A resistor R2 is connected between one of the input terminals of the comparator and the drain of the fourth MOS tube Q2, the connection between the sampling resistor R3 and the source of the fifth MOS tube 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 MOS tube Q4 is an NMOS tube, the fourth MOS tube Q2 is a PNOS tube, and the fifth MOS tube Q3 is an NMOS tube.

[0037] In this embodiment, the control module pulls up the switch signal, the third MOS tube Q4 is turned on, the fourth MOS tube Q2 is turned on, and the voltage of the second test end is compared with the reference voltage through the comparator. When the voltage of the second test end is greater than the reference voltage, the output level of the comparator increases, the conduction degree of the fifth MOS tube Q3 is strengthened, the voltage of the second test end decreases until it is less than the reference voltage, the output level of the comparator decreases, and the conduction degree of the fifth MOS tube Q3 decreases, and the adjustment is cyclically adjusted so that the second pull-up voltage of the second test end is equal to the reference voltage. The fourth pin of the control module is connected to the voltage output end of the sampling resistor R3, and the voltage value of the sampling resistor R3 is measured, and the pull-up current is calculated according to the voltage value of the sampling resistor R3 and the set resistance value of the sampling resistor R3.

[0038] It should be noted that energy is consumed by the load MOS tube, and it is necessary to connect multiple MOS tubes in parallel and add heat dissipation devices according to actual conditions.

[0039] Reference Figure 5 The control module is powered by a battery, receives the required voltage data according to the ADC interface, obtains the control signal and the display signal through internal calculation, and outputs the control signal and the display signal through the IO interface.

[0040] The fifth pin of the control module is connected to the first test end, and the sixth pin of the control module is connected to the second test end.

[0041] An embodiment of the present invention provides a parallel external current detection method, which uses the above parallel external current detection circuit.

[0042] Reference Figure 2 , the parallel external current detection method includes the following steps: Step S100, obtaining a first initial voltage value of a first test terminal and a second initial voltage value of a second test terminal of the motherboard to be tested; Step S200, loading the second test end according to the reference voltage, obtaining a loading current passing through the sampling resistor, a first loading voltage value of the first test end, and a second loading voltage value of the second test end; Step S300, calculating a test current of the motherboard to be tested according to the first initial voltage value, the second initial voltage value, the second load voltage value and the load current; The reference voltage is set according to the second initial voltage value.

[0043] In some embodiments, before loading the second test terminal according to the reference voltage, the detection method includes the following steps: Determining 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 ratio of the first initial voltage value, the detection is stopped.

[0044] According to some embodiments of the second aspect of the present invention, the reference voltage is set to a second preset ratio of the second initial voltage value; in different loading rounds, the second preset ratio is different and the reference voltage is different.

[0045] In some embodiments, obtaining the load current passing through the sampling resistor R3 includes the following steps: Measure and obtain the voltage value of the sampling resistor R3; According to the voltage value of the sampling resistor R3 and the resistance value of the sampling resistor R3, the load current passing through the sampling resistor R3 is obtained.

[0046] In some embodiments, calculating the test current of the motherboard to be tested according to the first initial voltage value, the second initial voltage value, the second load voltage value and the load current includes the following steps: 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 to obtain a first quotient value; The test current of the motherboard to be tested is obtained by multiplying the load current by the first quotient.

[0047] In a specific embodiment, the probe module obtains the first initial voltage value of the first test terminal and the second initial voltage value of the second test terminal of the tested motherboard. The control module receives the first initial voltage value of the first test terminal and the second initial voltage value of the second test terminal through the ADC interface.

[0048] Set the initial parameters as follows: reference voltage = 99% * second initial voltage; total test current = 0; total number of tests q = 0; number of single set voltage tests n = 0; voltage drop count m = 0; internal resistance of sampling resistor R3 = 0.5. Input the initial parameters into the control module.

[0049] Determine the 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 the first preset ratio of the first initial voltage value, stop the detection. The first preset ratio is set to 95%. Specifically, when the second initial voltage value is less than or equal to 95% of the first initial voltage value, turn off the switch signal. And determine whether the total number of tests q is greater than 0. When the total number of tests q is less than or equal to 0, send a display signal output information "voltage is less than the minimum value, test failed"; when the total number of tests q is greater than 0, send a display signal output information "test current = value A", where value A is the result of the test current.

[0050] It is understandable that the default power supply voltage minimum value cannot be less than 95% of the default value. If it is less than or equal to 95% of the default value, the detection 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 means that the voltage is lower than the minimum value before the test and does not meet the test requirements.

[0051] The single set voltage test number n is incremented by 1. Determine whether the single set voltage test number n is greater than 5 times. After the single set voltage value is tested 5 times by default, the reference voltage decreases and the load is increased. When the single set voltage test number n is less than or equal to 5 times, the reference voltage remains unchanged. When the single set voltage test number n is greater than 5 times, the reference voltage decreases by 1% of the second initial voltage value each time, and the voltage drop count m is incremented by 1. Determine the reference voltage.

[0052] The control module compares the current reference voltage and the reference voltage. When the reference voltage is less than the reference voltage, the reference voltage control signal is pulled high, and the reference voltage output by the reference voltage module 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, and the reference voltage output by the reference voltage module decreases until the reference voltage and the reference voltage are equal.

[0053] The control module sends a switch signal to start the constant voltage load module.

[0054] The timing is 2000mS, and the load is continued for 2S to stabilize the various voltage values. The load duration can be set according to the actual situation.

[0055] The voltage value of the sampling resistor R3 is measured; the control module obtains the pull current through the sampling resistor R3 according to the voltage value of the sampling resistor R3 and the resistance value of the sampling resistor R3. Specifically, according to Ohm's law, the pull current of the sampling resistor R3 is equal to the quotient of the voltage value of the sampling resistor R3 divided by the resistance value of the sampling resistor R3. That is, the pull current of the sampling resistor R3 = the voltage value of the sampling resistor R3 / the resistance value of the sampling resistor R3.

[0056] 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 a first quotient; and multiplies the load current by the first quotient to obtain the test current of the motherboard to be tested. That is, test current = load current * (first initial voltage value - second initial voltage value) / (second initial voltage value - second load voltage value).

[0057] The total number of tests q is incremented by 1.

[0058] Calculate the following data: total test current = previous total test current + current test current; average test current = total test current / q. The test accuracy can be increased by averaging the test results of each time.

[0059] The above is only a preferred embodiment of the present invention. The present invention is not limited to the above implementation. As long as the technical effect of the present invention is achieved by the same means, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure shall be included in the scope of protection of the present disclosure. All should belong to the protection scope of the present invention. Within the protection scope of the present invention, its technical scheme and / or implementation method can have various modifications and changes.

Claims

1. A parallel external current detection circuit, characterized in that: include: A probe module, the probe module is used to obtain a first initial voltage value of a first test terminal and a second initial voltage value of a second test terminal of the motherboard to be tested; A constant voltage load module, wherein the constant voltage load module is provided with a sampling resistor, and the constant voltage load module is used to pull a load at the second test end according to a reference voltage to obtain a pull current passing through the sampling resistor, and the probe module is used to obtain a second pull voltage value of the second test end of the motherboard to be tested, wherein the reference voltage is set according to the second initial voltage value; A control module 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 load voltage value and the load current.

2. The parallel external current detection circuit according to claim 1, characterized in that: The detection circuit further includes a reference voltage module, and the reference voltage module is used to provide a reference voltage for the constant voltage load module, wherein the reference voltage is equal to the base voltage.

3. The parallel external current detection circuit according to claim 2, characterized in that: 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 parallel external current detection circuit according to claim 3, characterized in that: The reference voltage module includes a first MOS tube and a second MOS tube, the gate of the first MOS tube is used to receive the reference voltage control signal, the drain of the first MOS tube is connected to the gate of the second MOS tube, and the drain of the second MOS tube is used to output the reference voltage.

5. The parallel external current detection circuit according to claim 1, characterized in that: The constant voltage load module includes a third MOS tube, a fourth MOS tube, a fifth MOS tube and a comparator, the gate of the third MOS tube is used to receive a switch signal, the drain of the third MOS tube is connected to the gate of the fourth MOS tube, one of the input ends of the comparator is connected to the drain of the fourth MOS tube, the other input end of the comparator is used to receive the reference voltage, the drain of the fourth MOS tube is connected to the drain of the fifth MOS tube, the output end of the comparator is connected to the gate of the fifth MOS tube, and the source of the fifth MOS tube is connected to the sampling resistor.

6. A parallel external current detection method, characterized in that: Using the parallel external current detection circuit as described in any one of claims 1 to 5, the detection method includes: Obtain a first initial voltage value of a first test terminal and a second initial voltage value of a second test terminal of the motherboard to be tested; Loading the second test end according to the reference voltage to obtain a load current passing through the sampling resistor and a second load voltage value of the second test end; Calculate the test current of the motherboard to be tested according to the first initial voltage value, the second initial voltage value, the second load voltage value and the load current; Wherein, the reference voltage is set according to the second initial voltage value.

7. The parallel external current detection method according to claim 6, characterized in that: Before loading the second test terminal according to the reference voltage, the detection method includes: determining 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 ratio of the first initial voltage value, detection is stopped.

8. The parallel external current detection method according to claim 6, characterized in that: The reference voltage is set to a second preset ratio of the second initial voltage value; in different loading rounds, the second preset ratio is different and the reference voltage is different.

9. The parallel external current detection method according to claim 6, characterized in that: Obtaining the load current passing through the sampling resistor, including: Measure the voltage value of the sampling resistor; The load current passing through the sampling resistor is obtained according to the voltage value of the sampling resistor and the resistance value of the sampling resistor.

10. The parallel external current detection method according to claim 6, characterized in that: The step of calculating the test current of the motherboard to be tested according to the first initial voltage value, the second initial voltage value, the second load voltage value and the load current includes: 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 to obtain a first quotient value; The load current is multiplied by the first quotient to obtain a test current of the mainboard to be tested.

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