A voltage and current source test circuit and test method

Abstract

The present invention provides a voltage and current source test circuit and test method, the test circuit includes a voltage and current source, the voltage and current source includes a control unit, an output power amplifier circuit, a current measurement circuit and a voltage measurement circuit, and a four-wire Kelvin circuit connected thereto, the four-wire Kelvin circuit includes a high-end current driving circuit, a high-end voltage sensing circuit, a low-end current driving circuit, and a low-end voltage sensing circuit; the voltage and current source also includes a four-way voltage measurement circuit corresponding to the four-wire Kelvin circuit. The present invention realizes additional differential voltage measurement by adding four-way voltage measurement circuits to measure the voltage drop on the current line, and also adds a switching circuit at the output end of the voltage and current source device to realize the overlap switching of the Kelvin measurement circuit, thereby realizing the equivalent contact resistance test on the current line before each test.

Description

Technical Field

[0001] The present invention relates to the technical field of integrated circuit testing, and in particular to a voltage and current source testing circuit and a testing method. Background Art

[0002] In integrated circuit testing, a voltage and current source (hereinafter referred to as VI source) is required to perform signal excitation and voltage and current measurement on the device under test (hereinafter referred to as DUT).

[0003] In order to improve the accuracy of output voltage and test voltage, traditional VI sources all use four-wire Kelvin wiring, which are high-end current drive circuit (FH, Force High), high-end voltage sensing circuit (SH, Sense High), low-end current drive circuit (FL, Force Low), and low-end voltage sensing circuit (SL, Sense Low). The current is output (or input) from the high-end current drive circuit (FH, Force High) and flows back (or out) from the low-end current drive circuit (FL, Force Low). Rfh and Rfl are the equivalent resistances generated by the transmission links of FH and FL respectively. Since the current flows through Rfh and Rfl, a certain voltage drop will be generated in the current transmission link.

[0004] For voltage measurement, the difference between the high-end voltage sensing circuit (SH, Sense High) and the low-end voltage sensing circuit (SL, Sense Low) is taken as the voltage difference on the DUT. The SH and SL terminals are high-impedance input terminals, and the voltages of the near and far ends of the signal are the same. Rsh and Rsl are the equivalent resistances of the transmission links of the SH and SL terminals, respectively. Since the SH and SL terminals are high-impedance input terminals, Rsh and Rsl are in the order of less than ohms when in good contact, and in the order of more than megohms when in poor contact. When the contact is good, it can be ignored compared to the high impedance of the SH and SL terminals, which is in the order of more than gigahertz, so the voltage difference between Rsh and Rsl is very small and can be ignored.

[0005] Figure 1The figure shows a traditional VI source architecture, which includes the following parts: the SH terminal and the SL terminal are connected to the differential operational amplifier OP2 and then to the CONTROL control, the voltage follower OP1 is connected in series to the SH terminal, the voltage follower OP5 is connected in series to the SL terminal, the range resistor Ri is connected in series to the FL terminal, the current differential measurement OP4 is connected in parallel across the range resistor Ri, and the output power amplifier OP3 is connected in series between the CONTROL control and the FH terminal. When the VI source architecture is working, the CONTROL control is set to the corresponding VI source mode state according to the required VI source mode, driving the output amplifier OP3 to work, and outputting from the FH terminal. The voltage follower OP1 and the voltage follower OP5 perform voltage following measurement to obtain Vsh and Vsl respectively, and pass through the differential operational amplifier OP2 to obtain the Vmeter signal, which is sent to the CONTROL control for feedback and measurement; at the same time, the signal output from the FH terminal flows through the DUT to the FL terminal, flows through Ri and finally flows to the GND terminal; the differential amplifier OP4 measures the voltage across Ri to obtain the Imeter signal, which is sent to the CONTROL control for feedback and measurement.

[0006] like Figure 2 As shown in the figure, when the traditional VI source architecture is used to perform signal excitation or voltage and current measurement on the DUT, a four-wire Kelvin connection is usually used. The voltage difference generated by the current on the equivalent resistance of the current line can be deducted, thereby accurately measuring the voltage difference sent to the two ends of the DUT.

[0007] However, in actual application, the output of the VI source must pass through cables, various adapter sockets, gold fingers or probes to reach the DUT. Each link has transmission resistance or contact resistance, which will cause different voltage drops. For fixed connection lines such as cables, the electrical transmission resistance is relatively stable, and the voltage drop on the transmission resistance is relatively fixed under a certain current. For adapter sockets that have electrical connections due to pressure, especially gold fingers or probes, the resistance of the contact part is related to the contact pressure, and also to the cleanliness and flatness of the contact surface. When the contact pressure becomes smaller, or the contact surface is not clean, or the contact surface is uneven, the contact resistance will become abnormally large, resulting in poor contact.

[0008] In particular, when using gold fingers or probes, they come into contact with multiple devices multiple times, which may cause wear and tear, resulting in reduced cleanliness of the contact surface, uneven contact surface, or reduced contact pressure; this problem will cause the test contact resistance to increase abnormally, resulting in test abnormalities. For this reason, it is necessary to detect the possible poor contact described above. Once poor contact is found, it is necessary to clean the gold finger or probe surface in time. If it is still abnormal, the contact pressure needs to be adjusted; if it is still abnormal, the gold finger or probe needs to be replaced to ensure good contact.

[0009] The traditional VI source architecture cannot accurately measure the equivalent contact resistance on the current line, namely Rfhc and Rflc. In high current tests, the equivalent contact resistance has a great impact on the voltage drop of the current line, and these equivalent contact resistances may change during each test. In each test of the VI source, if the values ​​of these equivalent contact resistances can be accurately measured, it is possible to quickly determine whether there is a reliability risk in the contact link (such as contact resistance changes caused by gold finger oxidation, wear, impurities, etc.), so as to make early warnings based on the test data and enter equipment maintenance to reduce greater quality risks in the later stage, such as burning needles, burning devices, burning VI sources, etc., especially in high-power and high-current tests, this problem is more serious.

[0010] Based on this, the traditional VI source architecture has been improved, such as Figure 3 As shown, based on the four-wire Kelvin connection of the traditional VI source, a differential voltage measurement circuit is added to the high and low ends of the VI source to implement additional differential voltage measurement to measure the voltage drop on the current line, thereby dynamically reading back the equivalent contact resistance on the current line during each test.

[0011] exist Figure 3 Based on the improvement of the traditional VI source architecture, Figure 4 When the measurement connection circuit shown is used to measure the contact resistance at both ends (high end and low end) of the DUT, the measuring current passes through the FL end of the VI source, flows through Rfl, Rflc, DUT, Rfhc and Rfh, and finally flows into the FH end of the VI source. Through the two differential operational amplifiers added at the high and low ends, the differential voltages between the SH end and the SHx end, and between the SL end and the SLx end are tested at the same time, and the voltages of Vdiff_High and Vdiff_low are obtained. By performing operations with the set current, the values ​​of Rfhc and Rflc can be calculated.

[0012] Although the above Figure 3 and Figure 4 The improved VI source architecture and its measurement connection circuit shown can well test the values ​​of Rfhc and Rflc, but there are several problems:

[0013] First, the contact test of the improved VI source architecture requires the cooperation of the device, that is, the device has a certain ability to flow current or the ability to flow a certain current in one direction, such as the device's own protection diode or parasitic diode, because the current of the contact resistance test needs to flow through the device under test. However, if the device itself is abnormal, such as the protection diode or parasitic diode is abnormal or there is an empty tube, the abnormality will be misjudged as a contact abnormality, which will affect the production test parameter statistics and the maintenance of the gold finger;

[0014] Second, for some devices, the pin does not have or needs other resources to have the ability to flow a certain current or the ability to flow a certain current in one direction. For example, the Gate end of MOSFET or IGBT has no parasitic diodes and other devices with the other two ends. In high-speed switching, the contact resistance of the Gate end has a great influence on the switching speed of the switch. Therefore, it is necessary to accurately test the contact resistance of the Gate end. For example, the Collector end of the transistor cannot be connected to the Emitter end when the Gate end is not driven;

[0015] Third, for the contact test of certain pins of such devices, the improved VI source architecture with contact resistance test is not fully applicable. In addition, in the contact resistance test of devices with multiple pins, when the VI source is connected, usually one power pin is used in parallel, such as the ground of the chip. For the floating VI source, the improved VI source architecture with contact resistance test performs contact resistance tests on multiple pins at the same time. A large current will flow through the parallel-connected power pins, which has a certain overcurrent risk and may damage the device. Summary of the invention

[0016] In view of this, the main purpose of the present invention is to provide a voltage and current source test circuit and test method. On the basis of the traditional four-wire Kelvin line, an additional differential voltage measurement is realized by adding a four-way voltage measurement circuit to measure the voltage drop on the current line. At the same time, a switching circuit is added at the output end of the voltage and current source device to realize the overlap switching of the Kelvin measurement circuit, so as to realize the equivalent contact resistance test on the current line before each test. Under the premise of not affecting the original characteristics of the VI source, the present invention can also realize the additional differential voltage measurement in the four-wire Kelvin circuit, accurately measure the equivalent contact resistance, so as to quickly determine whether there is a reliability risk in the contact link, and prevent the problem of easy damage to the device during large current testing due to the reduced reliability of the contact link.

[0017] The technical solution adopted by the present invention is a voltage and current source test circuit, comprising a voltage and current source, the voltage and current source comprising a control unit, an output power amplifier circuit, a current measurement circuit and a voltage measurement circuit, and a four-wire Kelvin circuit connected thereto, the four-wire Kelvin circuit comprising a high-end current driving circuit (FH), a high-end voltage sensing circuit (SH), a low-end current driving circuit (FL), and a low-end voltage sensing circuit (SL);

[0018] The voltage and current source further includes four voltage measurement circuits corresponding to the four-wire Kelvin circuit;

[0019] The two voltage measurement circuits (FHS, SHS) corresponding to the high-end current driving circuit (FH) and the high-end voltage sensing circuit (SH) are respectively used to measure the voltage generated by the contact resistance of the high-end port of the device under test, and output it to the first differential operational amplifier (OP103) for differential voltage operation. The first differential operational amplifier (OP103) is connected to the high-end current driving circuit (FH) and its corresponding voltage measurement circuit (FHS) through a first single-pole double-throw switch (K103) for dual control, and is also connected to the high-end voltage sensing circuit (SH) and its corresponding voltage measurement circuit (SHS) for dual control through a second single-pole double-throw switch (K104). The fixed ends of the first and second single-pole double-throw switches (K103, K104) are respectively connected to the input ends of the first differential operational amplifier (OP103);

[0020] The two voltage measurement circuits (FLS, SLS) corresponding to the low-end current driving circuit (FL) and the low-end voltage sensing circuit (SL) are respectively used to measure the voltage generated by the contact resistance of the low-end port of the device under test, and output it to the second differential operational amplifier (OP107) for differential voltage operation. The second differential operational amplifier (OP107) is connected to the low-end current driving circuit (FL) and its corresponding voltage measurement circuit (FLS) through a third single-pole double-throw switch (K110) for dual control, and is also connected to the low-end voltage sensing circuit (SL) and its corresponding voltage measurement circuit (SLS) for dual control through a fourth single-pole double-throw switch (K109). The fixed ends of the third and fourth single-pole double-throw switches (K110, K109) are respectively connected to the input ends of the second differential operational amplifier (OP107).

[0021] From the above, the technical solution adds four voltage measurement circuits corresponding to the four-wire Kelvin circuit on the basis of the original four-wire Kelvin circuit of the voltage and current source, and through the single-pole double-throw switch, the differential voltage on two of the circuits can be selected for measurement. In actual test applications, it is possible to test whether the contact between the voltage and current source and the device under test through the Kelvin external circuit is abnormal, and it is also possible to test the precise value of the contact resistance between the voltage and current source and the port of the device under test, so as to quickly determine whether there is a reliability risk in the contact link, and prevent the problem of damage to the device during high current testing due to reduced reliability of the contact link.

[0022] Preferably, the voltage and current source further includes:

[0023] A first switch (K101) is connected in series to the high-end current driving circuit (FH), and the high-end current driving circuit (FH) is also connected to its corresponding voltage measuring circuit (FHS) through a second switch (K102), and by switching the first switch (K101) or the second switch (K102), the current output by the output power amplifier circuit is transmitted to the high-end port of the device under test through the high-end current driving circuit (FH) or its corresponding voltage measuring circuit (FHS);

[0024] The low-end current driving circuit (FL) is connected to the high-end voltage sensing circuit (SH) and its corresponding voltage measuring circuit (SHS) through a third switch (K106) and a fourth switch (K105), respectively. By switching the third switch (K106) or the fourth switch (K105), the current flowing back from the high-end port of the device under test is transmitted to the low-end current driving circuit (FL) through the high-end voltage sensing circuit (SH) or its corresponding voltage measuring circuit (SHS).

[0025] From the above, by adding a relay switch to the four-wire Kelvin circuit of the voltage and current source and its corresponding voltage measurement circuit, without changing the external circuit, the current output by the voltage and current source can be output to the high-end port of the device under test through different circuits by only controlling the closing or opening of the switching relay switch, and the differential voltage between any two circuits can also be measured, thereby realizing the contact resistance test function between different circuits and the high-end port of the device under test.

[0026] Preferably, the voltage and current source further includes:

[0027] The high-end current driving circuit (FH) is connected to the low-end voltage sensing circuit (SL) and its corresponding voltage measuring circuit (SLS) through a fifth switch (K107) and a sixth switch (K108) respectively, and by switching the fifth switch (K107) or the sixth switch (K108), the current on the high-end current driving circuit (FH) is transmitted to the low-end port of the device under test through the low-end voltage sensing circuit (SL) or its corresponding voltage measuring circuit (SLS);

[0028] A seventh switch (K112) is connected in series to the low-end current driving circuit (FL), and the low-end current driving circuit (FL) is also connected to its corresponding voltage measuring circuit (FLS) through an eighth switch (K111). By switching the seventh switch (K112) or the eighth switch (K111), the current flowing back from the low-end port of the device under test flows back to the ground terminal through the low-end current driving circuit (FL) or its corresponding voltage measuring circuit (FLS).

[0029] From the above, by adding a relay switch to the four-wire Kelvin circuit of the voltage and current source and its corresponding voltage measurement circuit, without changing the external circuit, only by controlling the closing or opening of the switching relay switch, the current output by the voltage and current source can be output to the low-end port of the device under test through different circuits to form a complete loop, and the differential voltage between any two circuits can also be measured, thereby realizing the contact resistance test function between different circuits and the low-end port of the device under test.

[0030] Preferably, the voltage and current source is connected to two ends of the device under test via a six-wire Kelvin external connection method, and the six-wire Kelvin external connection method includes:

[0031] The high-end current driving circuit (FH) and its corresponding voltage measuring circuit (FHS) are connected to the high-end port of the device under test after being short-circuited near the high-end port of the device under test, and the high-end voltage sensing circuit (SH) and its corresponding voltage measuring circuit (SHS) are respectively connected to the high-end port of the device under test;

[0032] The low-end current driving circuit (FL) and its corresponding voltage measuring circuit (FLS) are connected to the low-end port of the device under test after being short-circuited near the low-end port of the device under test, and the low-end voltage sensing circuit (SL) and its corresponding voltage measuring circuit (SLS) are respectively connected to the low-end port of the device under test.

[0033] Preferably, the voltage and current source is connected to two ends of the device under test through a four-wire Kelvin external connection method, and the four-wire Kelvin external connection method includes:

[0034] The high-end current driving circuit (FH) and its corresponding voltage measuring circuit (FHS) are connected to the high-end port of the device under test after being short-circuited near the high-end port of the device under test, and the high-end voltage sensing circuit (SH) and its corresponding voltage measuring circuit (SHS) are connected to the high-end port of the device under test after being short-circuited near the high-end port of the device under test;

[0035] The low-end current driving circuit (FL) and its corresponding voltage measuring circuit (FLS) are connected to the low-end port of the device under test after being short-circuited near the low-end port of the device under test, and the low-end voltage sensing circuit (SL) and its corresponding voltage measuring circuit (SLS) are connected to the low-end port of the device under test after being short-circuited near the low-end port of the device under test.

[0036] As described above, due to the different fixtures for installing the device under test, it usually has six ports or four ports. At this time, according to the actual fixture selected, the six-wire Kelvin external connection method or the four-wire Kelvin external connection method can be selected to connect the voltage and current source to the device under test.

[0037] Optionally, the second switch (K102) and the fourth switch (K105) are closed, the first single-pole double-throw switch (K103) is connected to the voltage measurement circuit (FHS) corresponding to the high-end current driving circuit, and the second single-pole double-throw switch (K104) is connected to the voltage measurement circuit (SHS) corresponding to the high-end voltage sensing circuit, and according to the differential voltage measured by the first differential operational amplifier (OP103) and the current measured by the current test circuit, it is determined whether the two voltage measurement circuits (FHS, SHS) are connected to the high-end port of the device under test normally;

[0038] The first switch (K101) and the third switch (K106) are closed, the first single-pole double-throw switch (K103) is connected to the high-end current driving circuit (FH), and the second single-pole double-throw switch (K104) is connected to the high-end voltage sensing circuit (SH), and whether the high-end current driving circuit (FH) and the high-end voltage sensing circuit (SH) are connected to the high-end port of the device under test is normal according to the differential voltage measured by the first differential operational amplifier (OP103) and the current measured by the current test circuit.

[0039] From the above, through the above control method, the contact between the high-end current driving circuit and the high-end voltage sensing circuit and the high-end port of the device under test can be tested, and the contact between the voltage measurement circuits corresponding to the high-end current driving circuit and the high-end voltage sensing circuit and the high-end port of the device under test can also be tested.

[0040] Optionally, the first switch (K101) and the third switch (K106) are closed, the first single-pole double-throw switch (K103) is connected to the voltage measurement circuit (FHS) corresponding to the high-end current driving circuit, and the second single-pole double-throw switch (K104) is connected to the voltage measurement circuit (SHS) corresponding to the high-end voltage sensing circuit, and the contact resistance between the voltage and current source and the high-end port of the device under test is calculated based on the differential voltage measured by the first differential operational amplifier (OP103) and the current measured by the current test circuit.

[0041] From the above, through the above control method, the contact resistance value between the voltage and current source and the high-end port of the device under test can be accurately tested. It is worth noting that when the voltage and current source and the device under test are connected in a six-wire Kelvin external manner, the tested contact resistance value is the contact resistance value of the high-end current drive circuit and the contact terminal of the high-end port of the device under test. When the voltage and current source and the device under test are connected in a four-wire Kelvin external manner, the tested contact resistance value is the sum of the contact resistance values ​​of the high-end current drive circuit and the high-end voltage sensing circuit and the contact terminal of the high-end port of the device under test.

[0042] Optionally, the sixth switch (K108) and the eighth switch (K111) are closed, the third single-pole double-throw switch (K110) is connected to the voltage measurement circuit (FLS) corresponding to the low-end current driving circuit, and the fourth single-pole double-throw switch (K109) is connected to the voltage measurement circuit (SLS) corresponding to the low-end voltage sensing circuit, and according to the differential voltage measured by the second differential operational amplifier (OP107) and the current measured by the current test circuit, it is determined whether the two voltage measurement circuits (FLS, SLS) are connected to the low-end port of the device under test normally;

[0043] The fifth switch (K107) and the seventh switch (K112) are closed, the third single-pole double-throw switch (K110) is connected to the low-end current driving circuit (FL), and the fourth single-pole double-throw switch (K109) is connected to the low-end voltage sensing circuit (SL), and whether the low-end current driving circuit (FL) and the low-end voltage sensing circuit (SL) are connected to the low-end port of the device under test is normal according to the differential voltage measured by the second differential operational amplifier (OP107) and the current measured by the current test circuit.

[0044] From the above, through the above control method, the contact between the low-end current driving circuit and the low-end voltage sensing circuit and the low-end port of the device under test can be tested, and the contact between the voltage measurement circuits corresponding to the low-end current driving circuit and the low-end voltage sensing circuit and the low-end port of the device under test can also be tested.

[0045] Optionally, the fifth switch (K107) and the seventh switch (K112) are closed, the third single-pole double-throw switch (K110) is connected to the voltage measurement circuit (FLS) corresponding to the low-end current driving circuit, and the fourth single-pole double-throw switch (K109) is connected to the voltage measurement circuit (SLS) corresponding to the low-end voltage sensing circuit, and the contact resistance between the voltage and current source and the low-end port of the device under test is calculated based on the differential voltage measured by the second differential operational amplifier (OP107) and the current measured by the current test circuit.

[0046] From the above, through the above control method, the contact resistance value between the voltage and current source and the low-end port of the device under test can be accurately tested. It is worth noting that when the voltage and current source and the device under test are connected in a six-wire Kelvin external manner, the tested contact resistance value is the contact resistance value of the low-end current driving circuit and the contact terminal of the low-end port of the device under test. When the voltage and current source and the device under test are connected in a four-wire Kelvin external manner, the tested contact resistance value is the sum of the contact resistance values ​​of the low-end current driving circuit and the low-end voltage sensing circuit and the contact terminal of the low-end port of the device under test.

[0047] According to the above voltage and current source test circuit, the present invention also provides a test method, which uses the test circuit to perform a test on the contact resistance of the port of the device under test.

[0048] From the above, through the voltage and current source test circuit of the present invention, the contact condition between the auxiliary circuit of the voltage and current source and the device under test can be tested, and the contact resistance value when the voltage and current source is connected to the device under test through the terminal can be accurately measured. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is the circuit schematic diagram of the traditional voltage and current source;

[0050] Figure 2 The diagram is a four-wire Kelvin connection diagram of a traditional voltage and current source and a DUT;

[0051] Figure 3 A circuit schematic diagram of an improved voltage and current source in the prior art;

[0052] Figure 4 A schematic diagram of a circuit for measuring contact resistance using an improved voltage and current source in the prior art;

[0053] Figure 5 is a circuit schematic diagram of the voltage and current source device of the present invention;

[0054] Figure 6 A schematic diagram of a six-wire Kelvin connection between the voltage and current source device of the present invention and the DUT;

[0055] Figure 7-Figure 9 The circuit diagram of the present invention adopting the six-wire Kelvin method to measure the contact resistance of the high-end port of the DUT;

[0056] Figure 10-12 The present invention is a circuit diagram for measuring the contact resistance of the DUT low-end port using a six-wire Kelvin method;

[0057] Fig.13 A schematic diagram of a four-wire Kelvin connection between the voltage and current source device of the present invention and the DUT;

[0058] Figure 14-16 The present invention is a circuit diagram for measuring the contact resistance of the DUT high-end port using a four-wire Kelvin method;

[0059] Figure 17-Figure 19 The present invention is a circuit diagram for measuring the contact resistance of the DUT low-end port using a four-wire Kelvin method. DETAILED DESCRIPTION

[0060] Refer to the following Figures 5 to 19 The specific implementation of the voltage and current source device of the present invention is described in detail.

[0061] like Figure 5As shown, in the voltage-current source (hereinafter referred to as VI source) provided by the present invention, on the basis of the original four-wire Kelvin line of the internal circuit of the VI source, four voltage signal measurement circuits (FHS, SHS, FLS, SLS) are added to realize additional differential voltage measurement to measure the voltage drop on the current line;

[0062] Specifically, the original architecture of the VI source includes CONTROL control, output power amplifier circuit, current measurement circuit and voltage measurement circuit, and its internal four-wire Kelvin circuit, the four-wire Kelvin circuit is FH (high-end current drive circuit, Force High), SH (high-end voltage sensing circuit, Sense High), FL (low-end current drive circuit, ForceLow), SL (low-end voltage sensing circuit, Sense Low), and its corresponding output ports are FHout, SHout, FLout, SLout. When connected to the DUT, the four output ports are respectively connected to the two ends (high end and low end) of the DUT through an external signal line;

[0063] When the VI source architecture is working, the CONTROL control sets the VI source mode to the corresponding VI source mode state according to the required VI source mode, drives the output amplifier OP101 to work, outputs current from the FH signal line, and the current flows back to the FL signal line through the externally connected DUT, flows through the range resistor Ri and finally flows to the GND end. The differential amplifier OP109 connected to both ends of the range resistor Ri measures the voltage across the range resistor Ri to obtain the Imeter signal, which is sent to the CONTROL control for feedback and measurement. The voltage follower OP104 connected to the SH signal line and the voltage follower OP106 connected to the SL signal line perform voltage follower measurement respectively to obtain the measured voltages Vshx and Vslx respectively. The measured voltages Vshx and Vslx are subjected to differential operation by the differential operational amplifier OP105 to obtain the Vmeter signal, which is sent to the CONTROL control for feedback and measurement.

[0064] Based on the original architecture of the VI source, the present invention adds four additional voltage signal measurement circuits (FHS, SHS, FLS, SLS) for measuring the voltage drops on the corresponding lines (FH, SH, FL, SL), and the corresponding output ports are FHSout, SHSout, FLSout, and SLSout. When connected to the DUT, the four output ports are connected to the two ends (high end and low end) of the DUT through an external signal line. Figure 5 The connection method of the four-channel voltage signal measurement circuit added inside the VI source is described in detail:

[0065] The voltage signal measurement circuit (FHS) includes a differential operational amplifier OP103, a voltage follower OP102, a single-pole double-throw switch K103 and an FHS signal line, wherein the negative input end of the differential operational amplifier OP103 receives the voltage Vshx fed back from the output end of the voltage follower OP104 connected to the SH signal line, and the positive input end receives the voltage Vfhx fed back from the output end of the voltage follower OP102, the input end of the voltage follower OP102 is connected to the fixed end of the single-pole double-throw switch K103 through a wire FHX, and the two moving ends of the single-pole double-throw switch K103 are respectively connected to the FH signal line and the FHS signal line;

[0066] The voltage signal measurement circuit (SHS) comprises a single-pole double-throw switch K104 and a SHS signal line, wherein the fixed end of the single-pole double-throw switch K104 is connected to the input end of the voltage follower OP104 through a wire SHX, and the two moving ends of the single-pole double-throw switch K104 are respectively connected to the SH signal line and the SHS signal line;

[0067] The voltage signal measurement circuit (FLS) includes a differential operational amplifier OP107, a voltage follower OP108, a single-pole double-throw switch K110 and an FLS signal line, wherein the positive input end of the differential operational amplifier OP107 receives the voltage Vslx fed back from the output end of the voltage follower OP106 connected to the above-mentioned SL signal line, and the negative input end receives the voltage Vflx fed back from the output end of the voltage follower OP108, the input end of the voltage follower OP108 is connected to the fixed end of the single-pole double-throw switch K110 through a wire FLX, and the two moving ends of the single-pole double-throw switch K110 are respectively connected to the FL signal line and the FLS signal line;

[0068] The voltage signal measurement circuit (SLS) includes a single-pole double-throw switch K109 and an SLS signal line, wherein the fixed end of the single-pole double-throw switch K109 is connected to the input end of the voltage follower OP106 through a wire SLX, and the two moving ends of the single-pole double-throw switch K109 are respectively connected to the SL signal line and the SLS signal line.

[0069] In addition to the above-mentioned four-way voltage signal measurement circuit, the VI source also adds a switch switching circuit composed of several relay switches. Since the VI source is usually a complete structure, when using it to measure the DUT, it is often necessary to change the wiring method to achieve connection or disconnection with a certain port or a certain line of the DUT. It is extremely cumbersome to use and prone to wiring errors or poor contact. Therefore, the added switch switching circuit can improve the above shortcomings. By using it in conjunction with the above-mentioned single-pole double-throw switch, the relay switch is switched and selected during the actual measurement process, and the connection or disconnection with a certain port or a certain line of the DUT can be achieved, so as to achieve the measurement of contact resistance of different ports and other measurement functions. Specifically, the switch switching circuit includes:

[0070] A relay switch K101 connected in series to the FH signal line (close to the output port FHout), a relay switch K102 connected in series between the FH signal line and the FHS signal line, a relay switch K107 connected in series between the FH signal line and the SL signal line, and a relay switch K108 connected in series between the FH signal line and the SLS signal line;

[0071] Relay switch K112 connected in series on the FL signal line (close to the output port FLout), relay switch K111 connected in series between the FL signal line and the FLS signal line, relay switch K106 connected in series between the FL signal line and the SH signal line, and relay switch K105 connected in series between the FL signal line and the SHS signal line.

[0072] In actual measurement applications, due to the different types of fixtures for installing DUT devices, some fixtures have six external ports, while some fixtures may only have four external ports. Therefore, when using the VI source to measure the contact resistance at both ends of the DUT, the VI source can choose to use a six-wire Kelvin external connection method or a four-wire Kelvin external connection method to connect to the DUT according to the number of fixture ports. Here, the "external connection" refers to the signal line connecting the VI source and the DUT, and the external "six-wire Kelvin" or "four-wire Kelvin" refers to the number of signal lines connected to the DUT.

[0073] When the voltage and current source is connected to the DUT using a six-wire Kelvin external connection to measure contact resistance, the wiring method and test principle are as follows:

[0074] like Figure 6As shown, when the VI source is connected to the DUT using a six-wire Kelvin external connection method, for the convenience of the following description, the six-wire Kelvin external connection method and signal lines are defined separately: the FHS' signal line connected to the FHSout port and the FH' signal line connected to the FHout port are connected at a port close to the DUT and then connected to one end (high end) of the DUT, and the SHSout port and the SHout port are also connected to one end of the DUT through a SHS' signal line and a SH' signal line respectively; the FLS' signal line connected to the FLSout port and the FL' signal line connected to the FLout port are connected at a port close to the DUT and then connected to the other end (low end) of the DUT, and the SLSout port and the SLout port are also connected to the other end of the DUT through a SLS' signal line and a SL' signal line respectively;

[0075] It is worth noting that the above definition of the internal signal line and the external signal line of the VI source is only for the convenience of the following description. In actual use, the corresponding internal signal line and the external signal line, for example, FH and FH' may be one line.

[0076] According to the above six-wire Kelvin external connection method between the VI source and the DUT, the contact resistance of the high-end port of the DUT can be measured. The measurement process is as follows:

[0077] Contact test of DUT high-end auxiliary circuit 1: Figure 7 As shown, the relay switches K102 and K105 are closed, the single-pole double-throw switch K103 connects the FHS signal line, and the single-pole double-throw switch K104 connects the SHS signal line; the VI source outputs a constant current I (usually 10mA) through the output power amplifier OP101, and the current I flows out from the output end of the output power amplifier OP101, passes through the relay switch K102, the line resistance Rfhs of the FHS' signal line connected to the output port FHSout, the contact resistance Rfhc of the high-end port of the DUT, the contact resistance Rshsc between the SHS' signal line connected to the output port SHSout and the high-end port of the DUT, the line resistance Rshs of the SHS' signal line connected to the output port SHSout, and the relay switch K105, and flows into the FL signal line. At this time, by measuring the output terminal Vdiff_High of the differential operational amplifier OP103, the differential voltage Vdiff_High1 can be obtained, and by measuring the output terminal Imeter of the differential amplifier OP109, the current I1 can be obtained. When the current I1 is within the constant current error range of the VI source, the current I1 can be considered to be a normal output current. At this time, the auxiliary circuit contact resistance can be calculated, that is, Rh1=Vdiff_High1 / I1=Rfhs+Rfhc+Rshsc+Rshs;

[0078] When the result of the contact test 1 of the DUT high-end auxiliary circuit, i.e., the Rh1 value, is less than a certain value (usually 100 ohms), it is verified that the contact between the FHS' signal line connected to the output port FHSout and the SHS' signal line connected to the output port SHSout at the high-end port of the DUT is normal, and there is no contact disconnection or contact port damage, etc., which can prove that the results of the subsequent contact resistance test using the auxiliary circuit of the FHSout end and the auxiliary circuit of the SHSout end are valid;

[0079] Contact test 2 of DUT high-end auxiliary circuit: Figure 8 As shown, the relay switches K101 and K106 are closed, the single-pole double-throw switch K103 connects the FH signal line, the single-pole double-throw switch K104 connects the SH signal line, and the VI source outputs a constant current I (usually 10mA) through the output power amplifier OP101. The current I flows out from the output end of the output power amplifier OP101, passes through the relay switch K101, the line resistance Rfh of the FH' signal line connected to the output port FHout, the contact resistance Rfhc of the high-end port of the DUT, the contact resistance Rshc between the SH' signal line connected to the output port SHout and the high-end port of the DUT, the line resistance Rsh of the SH' signal line connected to the output port SHout, and the relay switch K106, and flows into the FL signal line. At this time, by measuring the output terminal Vdiff_High of the differential operational amplifier OP103, the differential voltage Vdiff_High2 can be obtained, and by measuring the output terminal Imeter of the differential amplifier OP109, the current I2 can be obtained. When the current I2 is within the constant current error range of the VI source, the current I2 can be considered to be a normal output current. At this time, the contact resistance of the auxiliary circuit can be calculated, that is, Rh2=Vdiff_High2 / I2=Rfh2+Rfhc+Rshc+Rsh, where Rfh2 includes the line resistance Rfh of the FHS' signal line connected to the output port FHout and the line resistance of the wire FHX and part of the FH signal line to the output port FHout;

[0080] When the result of the contact test 2 of the DUT high-end auxiliary circuit, i.e., the Rh2 value, is less than a certain value (usually 100 ohms), it is verified that the contact between the signal line FH' connected to the output port FHout and the signal line SH' connected to the output port SHout at the high-end port of the DUT is normal, and there is no contact break or contact port damage, etc., which can prove that the results of the subsequent contact resistance test using the auxiliary circuit of the FHout end and the auxiliary circuit of the SHout end are valid;

[0081] Contact resistance Rfhc test: Fig. 9As shown, the relay switches K101 and K106 are closed, the single-pole double-throw switch K103 connects the FHS signal line, the single-pole double-throw switch K104 connects the SHS signal line, and the VI source outputs a constant current I (usually 10mA) through the output power amplifier OP101. The current I flows out from the output end of the output power amplifier OP101, passes through the relay switch K101, the line resistance Rfh of the FH' signal line connected to the output port FHout, the contact resistance Rfhc of the high-end port of the DUT, the contact resistance Rshc of the SH' signal line connected to the output port SHout and the high-end port of the DUT, the line resistance Rsh of the SH' signal line connected to the output port SHout, and the relay switch K106, and flows into the FL signal line. The input end of the differential operational amplifier OP103 collects the voltage at the high-end contact of the DUT through the FHS signal line and the SHS signal line respectively. At this time, by measuring the output end Vdiff_High of the differential operational amplifier OP103, the differential voltage Vdiff_High3 can be obtained, and by measuring the output end Imeter of the differential amplifier OP109, the current I3 can be obtained. When the current I3 is within the constant current error range of the VI source, the current I3 can be considered to be a normal output current. Since the differential operational amplifier OP103 is a high-impedance input end, the line resistances Rfhs, Rshs and Rshsc on the FHS signal line and the SHS signal line have basically no effect on the pressure measurement result when the above-mentioned on-resistance is less than 100 ohms, and can be ignored. Therefore, the auxiliary circuit contact resistance Rfhc can be calculated, that is, Rh3=Vdiff_High3 / I3=Rfhc;

[0082] Through the above three-step measurement, the key contact resistance Rfhc value of the DUT high-end port can be accurately measured. The combined value of the remaining contact resistances can also be estimated based on the value of Rfhc (Rh3) and the above-measured Rh1 and Rh2, within a certain allowable range (usually 100 ohms), to meet other test requirements of the subsequent VI source. Fig. 9 By changing the connection of the single-pole double-throw switch K103 from the FHS signal line to the FH signal line, it can also be tested to obtain Rh3=Rfhc+Rfh2, where Rfh2 includes the line resistance Rfh of the FH' signal line connected to the output port FHout and the line resistance of the wire FHX and part of the FH signal line to the output port FHout.

[0083] Similarly, according to the contact resistance measurement principle of the high-end port of the DUT, the contact resistance measurement of the low-end port of the DUT can also be performed. The principle is the same. Figure 10-12 The description is as follows:

[0084] Contact test of DUT low-end auxiliary circuit 1: Fig.10As shown, the relay switches K111 and K108 are closed, the single-pole double-throw switch K109 is connected to the SLS signal line, and the single-pole double-throw switch K110 is connected to the FLS signal line; the VI source outputs a constant current I (usually 10mA) through the output power amplifier OP101, and the current I flows out from the output end of the output power amplifier OP101, passes through the relay switch K108, the line resistance Rsls of the SLS' signal line connected to the output port SLSout, the contact resistance Rslsc between the SLS' signal line connected to the output port SLSout and the low-end port of the DUT, the contact resistance Rflc of the low-end port of the DUT, the line resistance Rfls of the FLS' signal line connected to the output port FLSout, and the relay switch K111, and flows into the FL signal line. At this time, by measuring the output terminal Vdiff_Low of the differential operational amplifier OP107, the differential voltage Vdiff_Low4 can be obtained, and by measuring the output terminal Imeter of the differential amplifier OP109, the current I4 can be obtained. When the current I4 is within the constant current error range of the VI source, the current I4 can be considered to be a normal output current. At this time, the auxiliary circuit contact resistance can be calculated, that is, Rh4=Vdiff_Low4 / I4=Rsls+Rslsc+Rflc+Rfls;

[0085] When the result of the contact test 1 of the auxiliary circuit at the low end of the DUT, i.e., the Rh4 value, is less than a certain value (usually 100 ohms), it is verified that the contact between the FLS' signal line connected to the output port FLSout and the SLS' signal line connected to the output port SLSout at the low end port of the DUT is normal, and there is no contact disconnection or contact port damage, etc., which can prove that the results of the subsequent contact resistance test using the auxiliary circuit at the FLSout end and the auxiliary circuit at the SLSout end are valid;

[0086] Contact test 2 of DUT low-end auxiliary circuit: Fig.11As shown, the relay switches K112 and K107 are closed, the single-pole double-throw switch K109 connects the SL signal line, the single-pole double-throw switch K110 connects the FL signal line, and the VI source outputs a constant current I (usually 10mA) through the output power amplifier OP101. The current I flows out from the output end of the output power amplifier OP101, passes through the relay switch K107, the line resistance Rsl of the SL' signal line connected to the output port SLout, the contact resistance Rslc between the SL' signal line connected to the output port SLout and the low-end port of the DUT, the contact resistance Rflc of the low-end port of the DUT, the line resistance Rfl of the FL' signal line connected to the output port FLout, and the relay switch K112, and flows into the FL signal line. At this time, by measuring the output terminal Vdiff_Low of the differential operational amplifier OP107, the differential voltage Vdiff_Low5 can be obtained, and by measuring the output terminal Imeter of the differential amplifier OP109, the current I5 can be obtained. When the current I5 is within the constant current error range of the VI source, the current I5 can be considered to be a normal output current. At this time, the contact resistance of the auxiliary circuit can be calculated, that is, Rh5=Vdiff_Low5 / I5=Rfl5+Rslc+Rflc+Rfl, wherein Rfl5 includes the line resistance Rfl of the FL' signal line externally connected to the output port FLout and the line resistance of the wire FLX and part of the FL signal line to the output port FLout;

[0087] When the result of the contact test 2 of the auxiliary circuit at the low end of the DUT, i.e., the Rh5 value, is less than a certain value (usually 100 ohms), it is verified that the contact between the signal line FL' connected to the output port FLout and the signal line SL' connected to the output port SLout at the high end port of the DUT is normal, and there is no contact disconnection or contact port damage, etc., which can prove that the results of the subsequent contact resistance test using the auxiliary circuit at the FLout end and the auxiliary circuit at the SLout end are valid;

[0088] Contact resistance Rflc test: Fig.12As shown, the relay switches K112 and K107 are closed, the single-pole double-throw switch K109 connects the SLS signal line, the single-pole double-throw switch K110 connects the FLS signal line, and the VI source outputs a constant current I (usually 10mA) through the output power amplifier OP101. The current I flows out from the output end of the output power amplifier OP101, passes through the relay switch K107, the line resistance Rsl of the SL' signal line connected to the output port SLout, the contact resistance Rslc between the line resistance Rsl of the SL' signal line connected to the output port SLout and the low-end port of the DUT, the contact resistance Rflc of the low-end port of the DUT, the line resistance Rfl of the FL' signal line connected to the output port FLout, and the relay switch K112, and flows into the FL signal line. The input end of the differential operational amplifier OP107 collects the voltage at the low-end contact of the DUT through the SLS signal line and the FLS signal line respectively. At this time, by measuring the output end Vdiff_Low of the differential operational amplifier OP107, the differential voltage Vdiff_Low6 can be obtained, and by measuring the output end Imeter of the differential amplifier OP109, the current I6 can be obtained. When the current I6 is within the constant current error range of the VI source, the current I6 can be considered to be a normal output current. Since the differential operational amplifier OP109 is a high-impedance input end, the line resistances Rsls, Rslsc and Rfls on the SLS signal line and the FLS signal line have basically no effect on the pressure measurement result when the above-mentioned on-resistance is less than 100 ohms, and can be ignored. Therefore, the auxiliary circuit contact resistance Rflc can be calculated, that is, Rh6=Vdiff_Low6 / I6=Rflc;

[0089] Through the above three-step measurement, the key contact resistance Rflc of the DUT low-end port can be accurately measured. The combined value of the remaining contact resistances can also be estimated based on the value of Rflc (Rh6) and the above-measured Rh4 and Rh5, within a certain allowable range (usually 100 ohms), to meet other test requirements of the subsequent VI source. Fig.12 By changing the connection of the single-pole double-throw switch K110 from the FLS signal line to the FL signal line, it can also be tested to obtain Rh6=Rflc+Rfl5, where Rfl5 includes the line resistance Rfl of the FL' signal line connected to the output port FLout and the line resistance of the wire FLX and part of the FL signal line to the output port FLout.

[0090] When the voltage and current source is connected to the DUT using a four-wire Kelvin external connection to measure contact resistance, the wiring method and test principle are as follows:

[0091] like Fig.13As shown, when the VI source is connected to the DUT by a four-wire Kelvin external connection method, the four-wire Kelvin external connection method and the signal lines are defined separately for the convenience of the following description: the FHS' signal line connected to the FHSout port and the FH' signal line connected to the FHout port are connected at a port close to the DUT and then connected to one end (high end) of the DUT; the SHS' signal line connected to the SHSout port and the SH' signal line connected to the SHout port are also connected to the one end (high end) of the DUT after being connected at a port close to the DUT; the FLS' signal line connected to the FLSout port and the FL' signal line connected to the FLout port are connected at a port close to the DUT and then connected to the other end (low end) of the DUT; the SLS' signal line connected to the SLSout port and the SL' signal line connected to the SLout port are also connected to the other end (low end) of the DUT after being connected at a port close to the DUT;

[0092] It is worth noting that the above definition of the internal signal line and the external signal line of the VI source is only for the convenience of the following description. In actual use, the corresponding internal signal line and the external signal line, for example, FH and FH' may be one line.

[0093] According to the above four-wire Kelvin external connection method between the VI source and the DUT, the contact resistance of the high-end port of the DUT can be measured. The measurement process is the same as the measurement process using the six-wire Kelvin external connection method, and the only difference is that:

[0094] The high-end contact resistance measured by the six-wire Kelvin external connection method is Rfhc, while the high-end contact resistance measured by the four-wire Kelvin external connection method is Rfhc+Rshc; similarly, the low-end contact resistance measured by the six-wire Kelvin external connection method is Rflc, while the low-end contact resistance measured by the four-wire Kelvin external connection method is Rflc+Rslc;

[0095] Refer to the following Figure 14-Figure 19 A brief description of the process of contact resistance testing using four-wire Kelvin:

[0096] Contact test of DUT high-end auxiliary circuit 1: Fig.14 As shown, the relay switches K102 and K105 are closed, the single-pole double-throw switch K103 is connected to the FHS signal line, and the single-pole double-throw switch K104 is connected to the SHS signal line; by measuring the output terminal Vdiff_High of the differential operational amplifier OP103, the differential voltage Vdiff_High7 can be obtained, and by measuring the output terminal Imeter of the differential amplifier OP109, the current I7 can be obtained. At this time, the auxiliary circuit contact resistance can be calculated, that is, Rh7=Vdiff_High7 / I7=Rfhs+Rfhc+Rshc+Rshs;

[0097] When the result of the contact test 1 of the DUT high-end auxiliary circuit, i.e., the Rh7 value, is less than a certain value (usually 100 ohms), it is verified that the contact between the FHS' signal line connected to the output port FHSout and the SHS' signal line connected to the output port SHSout is normal near the high-end port of the DUT, and there is no contact disconnection or contact port damage, etc., which can prove that the results of the subsequent contact resistance test using the auxiliary circuit of the FHSout end and the auxiliary circuit of the SHSout end are valid;

[0098] Contact test 2 of DUT high-end auxiliary circuit: Fig.15 As shown, the relay switches K101 and K106 are closed, the single-pole double-throw switch K103 is connected to the FH signal line, and the single-pole double-throw switch K104 is connected to the SH signal line. By measuring the output terminal Vdiff_High of the differential operational amplifier OP103, the differential voltage Vdiff_High8 can be obtained, and by measuring the output terminal Imeter of the differential amplifier OP109, the current I8 can be obtained. At this time, the auxiliary circuit contact resistance can be calculated, that is, Rh8=Vdiff_High8 / I8=Rfh8+Rfhc+Rshc+Rsh, wherein Rfh8 includes the line resistance Rfh of the FHS' signal line connected to the output port FHout and the line resistance of the wire FHX and part of the FH signal line to the output port FHout;

[0099] When the result of the contact test 2 of the DUT high-end auxiliary circuit, i.e., the Rh8 value, is less than a certain value (usually 100 ohms), it is verified that the contact between the signal line FH' connected to the output port FHout and the signal line SH' connected to the output port SHout at the high-end port of the DUT is normal, and there is no contact break or contact port damage, etc., which can prove that the results of the subsequent contact resistance test using the auxiliary circuit of the FHout end and the auxiliary circuit of the SHout end are valid;

[0100] Contact resistance Rfhc+Rshc test: Fig.16As shown, the relay switches K101 and K106 are closed, the single-pole double-throw switch K103 is connected to the FHS signal line, and the single-pole double-throw switch K104 is connected to the SHS signal line. The input end of the differential operational amplifier OP103 collects the voltage at the high-end contact of the DUT through the FHS signal line and the SHS signal line respectively. At this time, by measuring the output end Vdiff_High of the differential operational amplifier OP103, the differential voltage Vdiff_High9 can be obtained, and by measuring the output end Imeter of the differential amplifier OP109, the current I9 can be obtained. Since the differential operational amplifier OP103 is a high-impedance input end, the line resistance Rfhs and Rshs on the FHS signal line and the SHS signal line have basically no effect on the pressure measurement result when the above-mentioned on-resistance is less than 100 ohms, and can be ignored. Therefore, the circuit contact resistance Rfhc+Rshc can be calculated, that is, Rh9=Vdiff_High9 / I9=Rfhc+Rshc;

[0101] Through the above three-step measurement, the key contact resistance Rfhc+Rshc value of the DUT high-end port can be accurately measured. The combined value of the remaining contact resistances can also be estimated based on the value of Rfhc+Rshc (Rh9) and the above-measured Rh1 and Rh2, within a certain allowable range (usually 100 ohms), to meet other test requirements of the subsequent VI source. For example, the above Fig.16 By changing the connection of the single-pole double-throw switch K103 from the FHS signal line to the FH signal line, it can also be tested to obtain Rh9=Rfhc+Rshc+Rfh2, where Rfh2 includes the line resistance Rfh of the FH' signal line connected to the output port FHout and the line resistance of the wire FHX and part of the FH signal line to the output port FHout.

[0102] Similarly, according to Figure 17-Figure 19 As shown, combined with the contact resistance measurement principle of the high-end port of the above-mentioned DUT, the contact resistance measurement of the low-end port of the DUT can also be performed, and the contact resistance (Rflc+Rslc) value of the low-end port of the DUT and the values ​​of the remaining line resistance combinations can be measured. The measurement principle and the control process of the switch switching circuit are consistent with the control process of measuring the contact resistance of the low-end port of the DUT using a six-wire Kelvin external connection, and will not be repeated here.

[0103] In summary, the voltage and current source device and contact resistance measurement circuit provided by the present invention have the following advantages compared with the existing voltage and current source and measurement circuit:

[0104] The contact resistance on the high and low end force lines (current lines) can be accurately tested by the six-wire Kelvin method;

[0105] The contact resistance and key transmission resistance of the high-end and low-end Force lines can be accurately tested by the six-wire Kelvin method. By subtracting the contact resistance of the Force line tested previously, the key transmission resistance of the Force line can be accurately tested.

[0106] If the device connection is limited, the traditional four-wire Kelvin connection can be used. However, compared with the traditional four-wire Kelvin connection, the sum of the contact resistances on the high and low end Force lines and Sense lines can be accurately tested separately;

[0107] Through the switch switching circuit inside the VI source, the six-wire Kelvin or four-wire Kelvin line connection of the high and low ends is realized, saving the use of external relays;

[0108] Through an external relay, measure the loop resistance between any two points.

[0109] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A voltage and current source test circuit, comprising a voltage and current source, the voltage and current source comprising a control unit, an output power amplifier circuit, a current measurement circuit and a voltage measurement circuit, and a four-wire Kelvin circuit connected thereto, the four-wire Kelvin circuit comprising a high-end current driving circuit (FH), a high-end voltage sensing circuit (SH), a low-end current driving circuit (FL), and a low-end voltage sensing circuit (SL); It is characterized in that The voltage and current source further includes four voltage measurement circuits corresponding to the four-wire Kelvin circuit; The two voltage measurement circuits (FHS, SHS) corresponding to the high-end current driving circuit (FH) and the high-end voltage sensing circuit (SH) are respectively used to measure the voltage generated by the contact resistance of the high-end port of the device under test, and output it to the first differential operational amplifier (OP103) for differential voltage operation. The first differential operational amplifier (OP103) is connected to the high-end current driving circuit (FH) and its corresponding voltage measurement circuit (FHS) through a first single-pole double-throw switch (K103) for dual control, and is also connected to the high-end voltage sensing circuit (SH) and its corresponding voltage measurement circuit (SHS) for dual control through a second single-pole double-throw switch (K104). The fixed ends of the first and second single-pole double-throw switches (K103, K104) are respectively connected to the input ends of the first differential operational amplifier (OP103); The two voltage measurement circuits (FLS, SLS) corresponding to the low-end current driving circuit (FL) and the low-end voltage sensing circuit (SL) are respectively used to measure the voltage generated by the contact resistance of the low-end port of the device under test, and output it to the second differential operational amplifier (OP107) for differential voltage operation. The second differential operational amplifier (OP107) is connected to the low-end current driving circuit (FL) and its corresponding voltage measurement circuit (FLS) through a third single-pole double-throw switch (K110) for dual control, and is also connected to the low-end voltage sensing circuit (SL) and its corresponding voltage measurement circuit (SLS) for dual control through a fourth single-pole double-throw switch (K109). The fixed ends of the third and fourth single-pole double-throw switches (K110, K109) are respectively connected to the input ends of the second differential operational amplifier (OP107).

2. The test circuit according to claim 1, characterized in that: The voltage and current source further comprises: A first switch (K101) is connected in series to the high-end current driving circuit (FH), and the high-end current driving circuit (FH) is also connected to its corresponding voltage measuring circuit (FHS) through a second switch (K102), and by switching the first switch (K101) or the second switch (K102), the current output by the output power amplifier circuit is transmitted to the high-end port of the device under test through the high-end current driving circuit (FH) or its corresponding voltage measuring circuit (FHS); The low-end current driving circuit (FL) is connected to the high-end voltage sensing circuit (SH) and its corresponding voltage measuring circuit (SHS) through a third switch (K106) and a fourth switch (K105), respectively. By switching the third switch (K106) or the fourth switch (K105), the current flowing back from the high-end port of the device under test is transmitted to the low-end current driving circuit (FL) through the high-end voltage sensing circuit (SH) or its corresponding voltage measuring circuit (SHS).

3. The test circuit according to claim 2, characterized in that: The voltage and current source further comprises: The high-end current driving circuit (FH) is connected to the low-end voltage sensing circuit (SL) and its corresponding voltage measuring circuit (SLS) through a fifth switch (K107) and a sixth switch (K108) respectively, and by switching the fifth switch (K107) or the sixth switch (K108), the current on the high-end current driving circuit (FH) is transmitted to the low-end port of the device under test through the low-end voltage sensing circuit (SL) or its corresponding voltage measuring circuit (SLS); A seventh switch (K112) is connected in series to the low-end current driving circuit (FL), and the low-end current driving circuit (FL) is also connected to its corresponding voltage measuring circuit (FLS) through an eighth switch (K111). By switching the seventh switch (K112) or the eighth switch (K111), the current flowing back from the low-end port of the device under test flows back to the ground terminal through the low-end current driving circuit (FL) or its corresponding voltage measuring circuit (FLS).

4. The test circuit according to claim 3, characterized in that: The voltage and current source is connected to two ends of the device under test through a six-wire Kelvin external connection method, and the six-wire Kelvin external connection method includes: The high-end current driving circuit (FH) and its corresponding voltage measuring circuit (FHS) are connected to the high-end port of the device under test after being short-circuited near the high-end port of the device under test, and the high-end voltage sensing circuit (SH) and its corresponding voltage measuring circuit (SHS) are respectively connected to the high-end port of the device under test; The low-end current driving circuit (FL) and its corresponding voltage measuring circuit (FLS) are connected to the low-end port of the device under test after being short-circuited near the low-end port of the device under test, and the low-end voltage sensing circuit (SL) and its corresponding voltage measuring circuit (SLS) are respectively connected to the low-end port of the device under test.

5. The test circuit according to claim 3, characterized in that: The voltage and current source is connected to two ends of the device under test through a four-wire Kelvin external connection method, and the four-wire Kelvin external connection method includes: The high-end current driving circuit (FH) and its corresponding voltage measuring circuit (FHS) are connected to the high-end port of the device under test after being short-circuited near the high-end port of the device under test, and the high-end voltage sensing circuit (SH) and its corresponding voltage measuring circuit (SHS) are connected to the high-end port of the device under test after being short-circuited near the high-end port of the device under test; The low-end current driving circuit (FL) and its corresponding voltage measuring circuit (FLS) are connected to the low-end port of the device under test after being short-circuited near the low-end port of the device under test, and the low-end voltage sensing circuit (SL) and its corresponding voltage measuring circuit (SLS) are connected to the low-end port of the device under test after being short-circuited near the low-end port of the device under test.

6. The test circuit according to claim 4 or 5, characterized in that: The second switch (K102) and the fourth switch (K105) are closed, the first single-pole double-throw switch (K103) is connected to the voltage measurement circuit (FHS) corresponding to the high-end current driving circuit, the second single-pole double-throw switch (K104) is connected to the voltage measurement circuit (SHS) corresponding to the high-end voltage sensing circuit, and according to the differential voltage measured by the first differential operational amplifier (OP103) and the current measured by the current test circuit, it is determined whether the two voltage measurement circuits (FHS, SHS) are connected to the high-end port of the device under test normally; The first switch (K101) and the third switch (K106) are closed, the first single-pole double-throw switch (K103) is connected to the high-end current driving circuit (FH), and the second single-pole double-throw switch (K104) is connected to the high-end voltage sensing circuit (SH), and whether the high-end current driving circuit (FH) and the high-end voltage sensing circuit (SH) are connected to the high-end port of the device under test is normal according to the differential voltage measured by the first differential operational amplifier (OP103) and the current measured by the current test circuit.

7. The test circuit according to claim 6, characterized in that: The first switch (K101) and the third switch (K106) are closed, the first single-pole double-throw switch (K103) is connected to a voltage measurement circuit (FHS) corresponding to a high-end current driving circuit, the second single-pole double-throw switch (K104) is connected to a voltage measurement circuit (SHS) corresponding to a high-end voltage sensing circuit, and the contact resistance between the voltage and current source and the high-end port of the device under test is calculated based on the differential voltage measured by the first differential operational amplifier (OP103) and the current measured by the current test circuit.

8. The test circuit according to claim 4 or 5, characterized in that: Closing the sixth switch (K108) and the eighth switch (K111), connecting the third single-pole double-throw switch (K110) to the voltage measurement circuit (FLS) corresponding to the low-end current driving circuit, connecting the fourth single-pole double-throw switch (K109) to the voltage measurement circuit (SLS) corresponding to the low-end voltage sensing circuit, and judging whether the two voltage measurement circuits (FLS, SLS) are connected to the low-end port of the device under test normally according to the differential voltage measured by the second differential operational amplifier (OP107) and the current measured by the current test circuit; The fifth switch (K107) and the seventh switch (K112) are closed, the third single-pole double-throw switch (K110) is connected to the low-end current driving circuit (FL), and the fourth single-pole double-throw switch (K109) is connected to the low-end voltage sensing circuit (SL), and whether the low-end current driving circuit (FL) and the low-end voltage sensing circuit (SL) are connected to the low-end port of the device under test is normal according to the differential voltage measured by the second differential operational amplifier (OP107) and the current measured by the current test circuit.

9. The test circuit according to claim 8, characterized in that: The fifth switch (K107) and the seventh switch (K112) are closed, the third single-pole double-throw switch (K110) is connected to the voltage measurement circuit (FLS) corresponding to the low-end current driving circuit, the fourth single-pole double-throw switch (K109) is connected to the voltage measurement circuit (SLS) corresponding to the low-end voltage sensing circuit, and the contact resistance between the voltage and current source and the low-end port of the device under test is calculated based on the differential voltage measured by the second differential operational amplifier (OP107) and the current measured by the current test circuit.

10. A testing method based on the testing circuit according to any one of claims 1 to 9, characterized in that: The test circuit is used to test the contact resistance of the port of the device under test.

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