On-line conduction voltage drop test circuit and test system

Abstract

The invention relates to a conduction voltage drop on-line test circuit and a test system. The on-line test circuit for the conduction voltage drop comprises a tested module, a clamping module, a first current source module, a compensation module, a second current source module and a differential amplification module, one end of the clamping module is connected with the tested module, and the other end of the clamping module is connected with the output end of the first current source module; the output end of the first current source module is connected with the positive input end of the differential amplification module; the output end of the second current source module is connected with the compensation module, and the output end of the second current source module is connected with the reverse input end of the differential amplification module. The on-line test circuit for the conduction voltage drop has the advantages of being compatible with negative voltage, high in sampling precision and high in test precision.

Description

Technical Field

[0001] This invention relates to the field of circuit testing technology, and in particular to an online test circuit and system for conduction voltage drop. Background Technology

[0002] Power devices in power converters must continuously withstand the combined stress of high voltage, high current, high switching frequency, and high temperature, leading to an increase in internal interface states, accumulation of defects, and degradation of package bonding leads and solder joints, resulting in deterioration of their electrical performance parameters. This is particularly evident in third-generation semiconductor SiC and GaN power devices, affecting electrical performance parameters such as on-resistance (Rdson), threshold voltage, leakage current, and gate charge. Increased on-resistance exacerbates device power consumption and can induce reliability problems such as thermal failure of the power converter system. Therefore, on-resistance degradation has become a core indicator for evaluating the reliability of power devices.

[0003] In existing technologies, the on-state voltage drop of power devices is typically tested using clamping circuits and differential amplifiers. However, when the on-resistance of the device under test (DUT) is too high, measuring the negative on-resistance of the soft-start circuit results in a negative current flowing through the DUT, generating a large negative voltage that impacts the clamping circuit, potentially causing circuit damage or measurement failure. Furthermore, existing test circuits have relatively low accuracy and precision. Summary of the Invention

[0004] Based on this, the purpose of the present invention is to provide an online conduction voltage drop test circuit and test system, which has the advantages of being compatible with negative voltage, having high sampling accuracy, and high test accuracy.

[0005] An online on-state voltage drop test circuit includes: a module under test, a clamping module, a first current source module, a compensation module, a second current source module, and a differential amplifier module; one end of the clamping module is connected to the module under test, and the other end is connected to the output terminal of the first current source module; the output terminal of the first current source module is connected to the positive input terminal of the differential amplifier module; the output terminal of the second current source module is connected to the compensation module, and the output terminal of the second current source module is connected to the inverting input terminal of the differential amplifier module. The clamping module includes a clamping diode, a reverse protection diode, and a Zener diode; the anode of the clamping diode is connected to the output terminal of the first current source module, and the cathode of the clamping diode is connected to the module under test; the cathode of the Zener diode is connected to the output terminal of the first current source module, and the anode is connected to the anode of the reverse protection diode, and the cathode of the reverse protection diode is grounded; the compensation module includes a first diode; the anode of the first diode is connected to the output terminal of the second current source module, and the cathode of the first diode is grounded.

[0006] The online conduction voltage drop test circuit of the present invention clamps the module under test through a clamping module and a Zener diode, thereby improving the sampling accuracy; and resists negative voltage through an anti-reverse diode, so that the test circuit can be compatible with negative voltage of the component under test.

[0007] Furthermore, the differential amplifier module also includes a first resistor, a second resistor, a third resistor, a fourth resistor, a first operational amplifier, and a reference power supply; one end of the first resistor is connected to the inverting input terminal of the first operational amplifier, and the other end is connected to the output terminal of the first operational amplifier; one end of the second resistor is connected to the reference power supply, and the other end is connected to the non-inverting input terminal of the first operational amplifier; one end of the third resistor is connected to the non-inverting input terminal of the first operational amplifier, and the other end serves as the non-inverting input terminal of the differential amplifier module; one end of the fourth resistor is connected to the inverting input terminal of the first operational amplifier, and the other end serves as the inverting input terminal of the differential amplifier module.

[0008] Furthermore, the first resistor is equal to the second resistor, and the third resistor is equal to the fourth resistor.

[0009] Furthermore, a first filter module and a first buffer module are provided between the output terminal of the first current source module and the positive input terminal of the differential amplifier module, and a second filter module and a second buffer module are provided between the output terminal of the second current source module and the inverted input terminal of the differential amplifier module.

[0010] Furthermore, the first filtering module includes a fifth resistor and a first capacitor. One end of the fifth resistor is connected to the output terminal of the first current source module, and the other end of the fifth resistor is connected to the input terminal of the first buffer module. One end of the first capacitor is grounded, and the other end is connected to the other end of the fifth resistor and the input terminal of the first buffer module. The second filtering module includes a sixth resistor and a second capacitor. One end of the sixth resistor is connected to the output terminal of the second current source module, and the other end of the sixth resistor is connected to the input terminal of the second buffer module. One end of the second capacitor is grounded, and the other end is connected to the other end of the sixth resistor and the input terminal of the second buffer module.

[0011] Furthermore, the first buffer module includes a second operational amplifier, the positive input terminal of the second operational amplifier is the input terminal of the first buffer module, and the output terminal is the output terminal of the first buffer module; the inverting input terminal of the second operational amplifier is connected to the output terminal of the second operational amplifier. The second buffer module includes a third operational amplifier, the positive input terminal of which is the input terminal of the second buffer module, and the output terminal of which is the output terminal of the second buffer module; the inverting input terminal of the third operational amplifier is connected to the output terminal of the third operational amplifier.

[0012] Furthermore, the current output by the first current source module and the second current source module are equal.

[0013] Furthermore, the first current source module and the second current source module have the same structure; the second current source module includes a second power supply, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, a fourth operational amplifier, and a fifth operational amplifier; the output terminal of the fifth operational amplifier is connected to one end of the eleventh resistor, the other end of the eleventh resistor is the output terminal of the second current source module, and the other end of the eleventh resistor is connected to the positive input terminal of the fourth operational amplifier; one end of the seventh resistor is connected to the output terminal of the fourth operational amplifier, and the other end is connected to the positive input terminal of the fifth operational amplifier; one end of the eighth resistor is connected to the output terminal of the fifth operational amplifier, and the other end is connected to the negative input terminal of the fifth operational amplifier; one end of the ninth resistor is connected to the positive input terminal of the fifth operational amplifier, and the other end is connected to the positive terminal of the second power supply, the negative terminal of the second power supply is grounded; one end of the tenth resistor is connected to the negative input terminal of the fifth operational amplifier, and the other end is grounded; the output terminal of the fourth operational amplifier is connected to the negative input terminal of the fourth operational amplifier.

[0014] Furthermore, the first current source module and the second current source module are mirror current sources.

[0015] A testing system includes: the aforementioned on-state voltage drop online testing circuit and a calculation module; the calculation module is connected to the output terminal of the on-state voltage drop online testing circuit.

[0016] To better understand and implement this invention, the following detailed description is provided in conjunction with the accompanying drawings. Attached Figure Description

[0017] Figure 1 This is a topology diagram of the on-state voltage drop online test circuit according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the on-state voltage drop online test circuit according to an embodiment of the present invention; Figure 3 This is a schematic diagram of an online forward voltage drop test circuit in an embodiment of the present invention, in which a diode group is used instead of a Zener diode. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] In the description of this invention, it should be noted that the terms "vertical direction," "up," "down," and "horizontal," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0020] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to thermally conductive connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or connections through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0021] Example Please see Figure 1 and Figure 2 This invention provides an online conduction voltage drop test circuit and test system.

[0022] The on-state voltage drop online test circuit of the present invention includes: a module under test 1, a clamping module 2, a first current source module 3, a first filter module 4, a compensation module 5, a second current source module 6, a second filter module 7, a first buffer module 8, a second buffer module 9, and a differential amplifier module 10.

[0023] One end of the clamping module 2 is connected to the DUT module 1, and the other end is connected to the output end of the first current source module 3; the output end of the first current source module 3 is connected to the input end of the first filtering module 4; the output end of the first filtering module 4 is connected to the input end of the first buffer module 8, and the output end of the first buffer module 8 is connected to the positive input end of the differential amplification module 10. The output end of the second current source module 6 is connected to the compensation module 5, and the output end of the second current source module 6 is connected to the input end of the second filtering module 7; the output end of the second filtering module 7 is connected to the input end of the second buffer module 9, and the output end of the second buffer module 9 is connected to the negative input end of the differential amplification module 10.

[0024] The DUT module 1 includes a DUT element and a test power supply, and the test power supply provides a measurement voltage VIN for the DUT element. The test power supply is connected to the input end of the DUT element and one end of the clamping module 2.

[0025] The first current source module 3 and the second current source module 6 are used to provide precise, stable, and quickly established current sources, and the current I1 provided by the first current source module 3 is equal to the current I2 provided by the second current source.

[0026] I3 is the current I3 input from the test power supply to the DUT element, and I1 << I3. When the DUT element is turned off, the voltage V of the DUT module 1 DUT = VIN; when the DUT element is turned on, V DUT = R DUT *(I3 + I1). Because I1 << I3, so V DUT ≈ R DUT * I3, where R [[ID=]20] DUT is the resistance of the DUT element.

[0027] The compensation circuit includes a first diode D1. The positive electrode of the first diode D1 is connected to the output end of the second current source module 6, and the negative electrode of the first diode D1 is grounded. Due to the existence of the compensation circuit, the voltage VB0 at the output end of the second current source module 6 is equal to the on - voltage drop VD1 of the first diode D1 based on the current I2.

[0028] The clamping module 2 includes a clamping diode D2, an anti - reverse diode D3, and a voltage - stabilizing diode D4. The positive electrode of the clamping diode D2 is connected to the output end of the first current source module 3, and the negative electrode of the clamping diode D2 is connected to the DUT module 1; the negative electrode of the voltage - stabilizing diode D4 is connected to the output end of the first current source module 3, the positive electrode is connected to the positive electrode of the anti - reverse diode D3, and the negative electrode of the anti - reverse diode D3 is grounded. When the DUT element is turned on, VA0 = VD2 + V DUTWherein, VD2, VD3, and VD4 are the clamping diode D2D2, the reverse protection diode D3D3, and the Zener diode D4D4, respectively, based on the forward voltage drop of the current I1, and VA0 is the voltage at the output terminal of the first current source module 3. In this embodiment of the invention, the clamping module 2, through the clamping diode D2 and the Zener diode D4, clamps the voltage within the Zener diode D4's regulation range when the device under test (DUT) is turned off; furthermore, through the reverse protection diode, it prevents negative current from flowing through the clamping diode D2 and the Zener diode D4 when the DUT is negatively conducting, thus preventing damage to the diodes and enabling the circuit to measure the negative forward voltage drop of the DUT.

[0029] Please see Figure 3 In some other embodiments, the Zener diode D4 can be replaced by a diode group DN consisting of several diodes.

[0030] The differential amplifier module 10 includes a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, and a first operational amplifier OP1. It further includes a reference power supply, which provides a reference voltage VREF. One end of the first resistor R1 is connected to the inverting input terminal of the first operational amplifier OP1, and the other end is connected to the output terminal of the first operational amplifier OP1. One end of the second resistor R2 is connected to the reference power supply, and the other end is connected to the non-inverting input terminal of the first operational amplifier OP1. One end of the third resistor R3 is connected to the non-inverting input terminal of the first operational amplifier OP1, and the other end serves as the non-inverting input terminal of the differential amplifier module 10. One end of the fourth resistor R4 is connected to the inverting input terminal of the first operational amplifier OP1, and the other end serves as the inverting input terminal of the differential amplifier module 10.

[0031] In the differential amplifier module 10, R3=R4 and R2=R1. Let VA1 be the voltage at the output of the first buffer module 8 and VB1 be the voltage at the output of the second buffer module 9. The output of the differential amplifier module 10 is the voltage V of the measured component DUT. DUT V DUT =(VA1-VB1)*R2 / R3+VREF.

[0032] The differential amplifier module can compensate for the forward voltage drop of the clamping diode D2 and improve the gain and sampling accuracy. VREF will boost the voltage of the input differential amplifier module 10 so that it can adapt to different controller sampling.

[0033] The first filter module 4 includes a fifth resistor R5 and a first capacitor C1. One end of the fifth resistor R5 is connected to the output terminal of the first current source module 3, and the other end of the fifth resistor R5 is connected to the input terminal of the first buffer module 8. One end of the first capacitor C1 is grounded, and the other end is connected to the other end of the fifth resistor R5 and the input terminal of the first buffer module 8.

[0034] The second filter module 7 includes a sixth resistor R6 and a second capacitor C2. One end of the sixth resistor R6 is connected to the output terminal of the second current source module 6, and the other end of the sixth resistor R6 is connected to the input terminal of the second buffer module 9. One end of the second capacitor C2 is grounded, and the other end is connected to the other end of the sixth resistor R6 and the input terminal of the second buffer module 9.

[0035] The first filter module 4 and the second filter module 7 are used to filter out the interference waveform of the current input to the filter module. The cutoff frequency of the first filter module 4 is f1=1 / (2*π*R5*C1), and the cutoff frequency of the second filter module 7 is f1=1 / (2*π*R6*C2). In some embodiments, R5=R6, C1=C2.

[0036] The first buffer module 8 includes a second operational amplifier OP2, the positive input terminal of the second operational amplifier OP2 is the input terminal of the first buffer module 8, and the output terminal is the output terminal of the first buffer module 8; the inverting input terminal of the second operational amplifier OP2 is connected to the output terminal of the second operational amplifier OP2.

[0037] The second buffer module 9 includes a third operational amplifier OP3. The positive input terminal of the third operational amplifier OP3 is the input terminal of the second buffer module 9, and the output terminal is the output terminal of the second buffer module 9. The inverting input terminal of the third operational amplifier OP3 is connected to the output terminal of the third operational amplifier OP3.

[0038] The first buffer module 8 and the second buffer module 9 can increase the input impedance of the differential amplifier module 10 and improve the sampling accuracy.

[0039] Since the buffer module and the filter module only serve the functions of buffering and filtering, VA0 = VA1 and VB0 = VB1.

[0040] Furthermore, the second current source module 6 includes a second power supply V2, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, an eleventh resistor R11, a fourth operational amplifier OP4, and a fifth operational amplifier OP5. The output of the fifth operational amplifier OP5 is connected to one end of the eleventh resistor R11, the other end of which is the output of the second current source module 6, and the other end of the eleventh resistor R11 is connected to the positive input of the fourth operational amplifier OP4; one end of the seventh resistor R7 is connected to the output of the fourth operational amplifier OP4, and the other end is connected to the positive input of the fifth operational amplifier OP5; one end of the eighth resistor R8 is connected to the output of the fifth operational amplifier OP5, and the other end is connected to the negative input of the fifth operational amplifier OP5; one end of the ninth resistor R9 is connected to the positive input of the fifth operational amplifier OP5, and the other end is connected to the positive terminal of the second power supply V2, the negative terminal of the second power supply V2 is grounded, and the output voltage of the second power supply V2 is V2; one end of the tenth resistor R10 is connected to the negative input of the fifth operational amplifier OP5, and the other end is grounded; the output of the fourth operational amplifier OP4 is connected to the negative input of the fourth operational amplifier OP4.

[0041] In the second current source module 6, R9=R10 and R7=R8, then I2=V2*R7 / R9 / R11.

[0042] The structure of the first current source module 3 is the same as that of the second current source module 6. Further, the first current source module 3 includes a first power supply V1, a twelfth resistor R12, a thirteenth resistor R13, a fourteenth resistor R14, a fifteenth resistor R15, a sixteenth resistor R16, a sixth operational amplifier OP6, and a seventh operational amplifier OP7. The output of the seventh operational amplifier OP7 is connected to one end of the sixteenth resistor R16, the other end of which is the output of the first current source module 3, and the other end of the sixteenth resistor R16 is connected to the positive input of the sixth operational amplifier OP6; one end of the twelfth resistor R12 is connected to the output of the sixth operational amplifier OP6, and the other end is connected to the positive input of the seventh operational amplifier OP7; one end of the thirteenth resistor R13 is connected to the output of the seventh operational amplifier OP7, and the other end is connected to the negative input of the seventh operational amplifier OP7; one end of the fourteenth resistor R14 is connected to the positive input of the seventh operational amplifier OP7, and the other end is connected to the positive terminal of the first power supply V1, the negative terminal of the first power supply V1 is grounded, and the output voltage of the first power supply V1 is V1; one end of the fifteenth resistor R15 is connected to the negative input of the seventh operational amplifier OP7, and the other end is grounded; the output of the sixth operational amplifier OP6 is connected to the negative input of the sixth operational amplifier OP6.

[0043] In the first current source module 3, R14=R15 and R12=R13, then I1=V1*R12 / R14 / R16.

[0044] In this embodiment of the invention, R14=R15=R9=R10, R16=R11, R12=R13=R7=R8, V1=V2; at this time, I1=V1*R12 / R14 / R16=V2*R7 / R9 / R11=I2, that is, I1=I2, therefore VD2=VD3=VD1.

[0045] The first current source module 3 and the second current source module 6 have high precision and high stability, which makes the current flowing through the clamping diode D2 and the first diode D1 the same, and makes the forward voltage drop height of the clamping diode D2 and the first diode D1 the same, which greatly increases the sampling accuracy of the circuit.

[0046] In this embodiment, the first operational amplifier OP1, the second operational amplifier OP2, and the third operational amplifier OP3 are powered by dual power supplies, while the fourth operational amplifier OP4, the fifth operational amplifier OP5, the sixth operational amplifier OP6, and the seventh operational amplifier OP7 are powered by a single power supply.

[0047] In other embodiments, the first current source module 3 and the second current source module 6 can be mirror current sources or ordinary current sources that output the same current.

[0048] When the device under test (DUT) is turned off, I3 = 0A, I1 flows through the fourth and third inductors, and I2 flows through the first inductor; the second, third, and fourth inductors clamp the voltage VA0 to VA0 = VD2 + R. DUT *I3. Because VA0=VA1 and VB0=VB1, the differential amplifier module 10 amplifies VA1 and VB1 differentially to obtain the forward voltage drop of the device under test: V DUT =(VA1-VB1)*R2 / R3+VREF= (VD4+VD3)-VD1*R2 / R3+VREF=VD4*R2 / R3+VREF; At this time, the output of the differential amplifier module 10 is the sum of the voltage applied to the Zener diode D4 when current I1 flows through it and the reference voltage VREF.

[0049] When the device under test (DUT) is turned on, current I3 flows through the DUT, I1 flows through the clamping diode D2 and the DUT, and current I2 flows through the first diode D1; the clamping diode D2 clamps VA0 to VA0 = VD2 + R. DUT*I3. Because VA0=VA1 and VB0=VB1, after differential amplification of VA1 and VB1 by differential amplification module 10, the forward voltage drop of the measured component is obtained: V DUT =(VA1-VB1)*R2 / R3+VREF= (VD2+RDUT*I3-VD1)*R2 / R3+VREF=R DUT *I3*R2 / R3+VREF; At this time, the output of the differential amplifier module 10 is the forward voltage drop +VREF of the current flowing through I3 in the measured component DUT, therefore R DUT =(V DUT -VREF)*R3 / R2.

[0050] Based on the same inventive concept, the present invention also provides a test system for an online on-state voltage drop test circuit, including the aforementioned online on-state voltage drop test circuit and a calculation module; the calculation module is connected to the output terminal of the online on-state voltage drop test circuit and is able to record or set the magnitudes of the second resistor R2, the third resistor R3, and the reference voltage VREF; the test system is able to record the changes in on-state voltage drop and calculate the changes in on-resistance based on the on-state voltage drop.

[0051] The online conduction voltage drop test circuit and test system of the present invention have high sampling accuracy and can measure the negative conduction voltage drop of the test element, which greatly improves the compatibility and safety of the test circuit.

[0052] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and the present invention also intends to include these modifications and variations.

Claims

1. An on- voltage drop online test circuit, characterized in that, include: The module under test, clamping module, first current source module, compensation module, second current source module, and differential amplifier module; One end of the clamping module is connected to the module under test, and the other end is connected to the output terminal of the first current source module; the output terminal of the first current source module is connected to the positive input terminal of the differential amplifier module; the output terminal of the second current source module is connected to the compensation module, and the output terminal of the second current source module is connected to the inverting input terminal of the differential amplifier module. The clamping module includes a clamping diode, a reverse protection diode, and a Zener diode; the anode of the clamping diode is connected to the output terminal of the first current source module, and the cathode of the clamping diode is connected to the module under test; the cathode of the Zener diode is connected to the output terminal of the first current source module, and the anode is connected to the anode of the reverse protection diode, and the cathode of the reverse protection diode is grounded; the compensation module includes a first diode; the anode of the first diode is connected to the output terminal of the second current source module, and the cathode of the first diode is grounded.

2. The on- voltage drop online test circuit of claim 1, wherein: The differential amplifier module further includes a first resistor, a second resistor, a third resistor, a fourth resistor, a first operational amplifier, and a reference power supply; one end of the first resistor is connected to the inverting input terminal of the first operational amplifier, and the other end is connected to the output terminal of the first operational amplifier; one end of the second resistor is connected to the reference power supply, and the other end is connected to the non-inverting input terminal of the first operational amplifier; one end of the third resistor is connected to the non-inverting input terminal of the first operational amplifier, and the other end serves as the non-inverting input terminal of the differential amplifier module; one end of the fourth resistor is connected to the inverting input terminal of the first operational amplifier, and the other end serves as the inverting input terminal of the differential amplifier module.

3. The on- voltage drop online test circuit of claim 2, wherein: The first resistor is equal to the second resistor, and the third resistor is equal to the fourth resistor.

4. The on- voltage drop online test circuit of claim 1, wherein: A first filter module and a first buffer module are provided between the output terminal of the first current source module and the positive input terminal of the differential amplifier module, and a second filter module and a second buffer module are provided between the output terminal of the second current source module and the inverted input terminal of the differential amplifier module.

5. The on- voltage drop online test circuit of claim 4, wherein: The first filtering module includes a fifth resistor and a first capacitor. One end of the fifth resistor is connected to the output terminal of the first current source module, and the other end of the fifth resistor is connected to the input terminal of the first buffer module. One end of the first capacitor is grounded, and the other end is connected to the other end of the fifth resistor and the input terminal of the first buffer module. The second filtering module includes a sixth resistor and a second capacitor. One end of the sixth resistor is connected to the output terminal of the second current source module, and the other end of the sixth resistor is connected to the input terminal of the second buffer module. One end of the second capacitor is grounded, and the other end is connected to the other end of the sixth resistor and the input terminal of the second buffer module.

6. The on- voltage drop online test circuit of claim 4, wherein: The first buffer module comprises a second operational amplifier, a positive input end of the second operational amplifier is an input end of the first buffer module, and an output end is an output end of the first buffer module; and a negative input end of the second operational amplifier is connected with an output end of the second operational amplifier. The second buffer module comprises a third operational amplifier, a positive input end of the third operational amplifier is an input end of the second buffer module, and an output end is an output end of the second buffer module; and a negative input end of the third operational amplifier is connected with an output end of the third operational amplifier.

7. The on- voltage drop online test circuit according to any one of claims 1-6, characterized in that: The first current source module and the second current source module output equal currents.

8. The on- voltage drop online test circuit of claim 7, wherein: The first current source module and the second current source module are of the same structure; the second current source module comprises a second power supply, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, a fourth operational amplifier and a fifth operational amplifier; an output end of the fifth operational amplifier is connected with one end of the eleventh resistor, the other end of the eleventh resistor is an output end of the second current source module, and the other end of the eleventh resistor is connected with a positive input end of the fourth operational amplifier; one end of the seventh resistor is connected with an output end of the fourth operational amplifier, and the other end is connected with a positive input end of the fifth operational amplifier; one end of the eighth resistor is connected with an output end of the fifth operational amplifier, and the other end is connected with a negative input end of the fifth operational amplifier; one end of the ninth resistor is connected with a positive input end of the fifth operational amplifier, and the other end is connected with a positive pole of the second power supply, a negative pole of the second power supply is grounded; one end of the tenth resistor is connected with a negative input end of the fifth operational amplifier, and the other end is grounded; and an output end of the fourth operational amplifier is connected with a negative input end of the fourth operational amplifier.

9. The on- voltage drop online test circuit of claim 7, wherein: The first current source module and the second current source module are mirror current sources.

10. A test system, characterized by, The method comprises the following steps: The method comprises the following steps: The calculation module is connected with an output end of the on-voltage drop online test circuit.

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