CN116413493A

CN116413493A - Current measuring device with leakage current prevention function

Info

Publication number: CN116413493A
Application number: CN202111652458.1A
Authority: CN
Inventors: 吴健铭; 杜嘉豪; 吴宗禧
Original assignee: Chroma ATE Suzhou Co Ltd
Current assignee: Chroma ATE Suzhou Co Ltd
Priority date: 2021-12-30
Filing date: 2021-12-30
Publication date: 2023-07-11

Abstract

The application provides a current measuring device with a leakage current prevention function, which comprises a first current measuring module and a second current measuring module. The first current measuring module is electrically connected between the input end and the output end, and selectively conducts a first current path to the output end. The second current measuring module is electrically connected between the input end and the output end, and selectively conducts a second current path to the output end. When the first current path is cut off and the second current path is conducted, the first current measuring module provides a first protection voltage to the first current path, the first protection voltage is equal to the output end voltage of the output end, and the output end is electrically connected with the component to be measured.

Description

Current measuring device with leakage current prevention function

Technical Field

The present invention relates to a current measuring device, and more particularly to a current measuring device with leakage current prevention function.

Background

Generally, when a current measuring device measures current, different measuring circuits are designed for different current measuring ranges of different specifications. For example, when measuring a large current, the current measuring module provided by the current measuring device may be provided with a plurality of gear positions, and each gear position corresponds to a different current measuring range. In contrast, in order to avoid interference and error, when measuring small current, the current measuring module provided by the current measuring device usually only corresponds to one current measuring range, so that a plurality of current measuring modules are required to correspond to a plurality of current measuring ranges for measuring the small current. Referring to fig. 1, fig. 1 is a functional block diagram of a conventional current measurement apparatus. As shown in fig. 1, a conventional current measuring device 9 for measuring small currents has a power amplifier 90 and a plurality of

current measuring modules

91, 92, 93, wherein the

current measuring modules

91, 92, 93 respectively correspond to different current measuring ranges. Here, the current measuring module 91 may be composed of the switch set SW91 and the measuring resistor R91, the current measuring module 92 may be composed of the switch set SW92 and the measuring resistor R92, and the current measuring module 93 may be composed of the switch set SW93 and the measuring resistor R93.

In practice, if one of the current measuring modules 92 measures the current flowing through the DUT, the remaining

current measuring modules

91 and 93 turn off the switch sets SW91 and SW93, so that theoretically the current can only pass through the current measuring module 92 to the DUT. That is, the current I92 flowing through the switch set SW92 and the measurement resistor R92 should be the current flowing through the DUT. At this time, by measuring the voltage across the resistor R92, the current I92 can be reversely pushed, thereby measuring the current flowing through the DUT. However, as the magnitude of the current to be measured becomes smaller, the circuit configuration of the testing device 9 shown in fig. 1 will generate larger and larger errors. For practical example, when the magnitude of the current to be measured is less than 100nA, the undesirable characteristics of the switch sets SW 91-SW 93 will begin to be affected. Such as leakage current problems of the switch sets SW 91-SW 93, which may become non-negligible as the magnitude of the current to be measured becomes smaller. Referring to fig. 1 and fig. 2 together, fig. 2 is a schematic current diagram of a conventional current measuring module. As shown in the figure, the undesirable characteristics of the switch groups SW91 and SW93 make the switch groups SW91 and SW93 inevitably leak current when turned off. In other words, the current flowing through the switch set SW92 and the measuring resistor R92 may leak to the switch sets SW91 and SW93, such as leakage current I _leak 91、I _leak 93. Presence of leakage current I _leak 91、I _leak 93 means that the current I92 flowing through the switch set SW92 and the measuring resistor R92 is not equal to the current flowing through the DUT, so that the voltage across the measuring resistor R92 is not known to be the actual current flowing through the DUTStream I92'. Accordingly, a new current measuring device is needed to eliminate the error in measuring small currents.

Disclosure of Invention

The technical problem to be solved in the application is to provide a current measuring device with a leakage current prevention function, which is provided with a plurality of current measuring modules, wherein the cut-off current measuring modules can keep a protection voltage similar to that of a component to be measured, so that leakage current is prevented from occurring from the output end.

The application provides a current measuring device with a leakage current prevention function, which comprises a first current measuring module and a second current measuring module. The first current measuring module is electrically connected between the input end and the output end, and is provided with a first switch group, a first voltage controller and a first measuring resistor which are connected in series with a first current path, wherein the first switch group selectively conducts the first current path to the output end. The second current measuring module is electrically connected between the input end and the output end and is provided with a second switch group, a second voltage controller and a second measuring resistor which are connected in series with a second current path, and the second switch group selectively conducts the second current path to the output end. When the first switch group is turned off and the second switch group is turned on, the first voltage controller provides a first protection voltage on the first current path according to the first control signal, the first protection voltage is equal to the output end voltage of the output end, and the output end is electrically connected with the component to be tested.

In some embodiments, the current measuring device may further include a control unit, where the control unit is electrically connected to the first current measuring module, the second current measuring module, and the voltage monitoring module may measure an output voltage of the output terminal, and the control unit may generate the first control signal according to the output voltage. In addition, the first measuring resistor is electrically connected between the first voltage controller and the output end, and when the first switch group is turned on and the second switch group is turned off, the first voltage controller can measure the first end voltage of the first measuring resistor, and the difference value between the first end voltage and the output end voltage is the voltage across the first measuring resistor. In addition, the voltage across the first measuring resistor can calculate the current to be measured of the component to be measured.

The application provides a current measuring device with a leakage current prevention function, which is provided with a plurality of current paths electrically connected to a component to be measured, wherein the cut-off current paths can keep a protection voltage similar to that of the component to be measured, so that leakage current is prevented from occurring from the cut-off current paths.

In some embodiments, the current measuring device may further include a control unit, where the control unit is electrically connected to the first current measuring module, the second current measuring module, and the voltage monitoring module, the voltage monitoring module may measure an output voltage of the output terminal, the control unit may generate a first control signal according to the output voltage, and the first current measuring module provides a first protection voltage to the first current path according to the first control signal. In addition, when the first current path is on and the second current path is off, the first current measuring module can measure the voltage across the first measuring resistor in the first current path, and the voltage across the first measuring resistor is related to the current to be measured of the component to be measured.

In summary, the current measuring device with the leakage current prevention function provided by the present application has a plurality of current measuring modules, and each current measuring module has a corresponding current path electrically connected to the component to be measured. The cut-off current measuring module can keep a protection voltage in the current path, wherein the protection voltage is similar to the voltage of the component to be measured, so that leakage current is prevented from occurring in the cut-off current path.

Other details of the other functions and embodiments of the present application are described below with reference to the drawings.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments described in the present application, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a functional block diagram of a conventional current measuring device;

FIG. 2 is a schematic diagram of a conventional current measurement module;

FIG. 3 is a functional block diagram of a current measuring device with leakage current prevention function according to an embodiment of the present application;

FIG. 4 is a functional block diagram of a current measuring device with leakage current prevention function according to another embodiment of the present application.

Symbol description

1. Current measuring device 10 and current measuring module

100. Voltage controller 12 current measuring module

120. Voltage controller 14 current measuring module

140. Voltage controller 16 power amplifier

18. Control unit 20 voltage monitoring module

90. DUT (device under test) component of power amplifier

91. 92, 93 current measuring module

Switch groups of SW10, SW12, SW14, SW91, SW92 and SW93

R10, R12, R14, R91, R92, R93 measuring resistance

I12 Current I92, I92' current

I _leak 91、I _leak 93. Leakage current a output terminal

b input x, y, z reference

Detailed Description

The positional relationship described in the following embodiments includes: the upper, lower, left and right, unless otherwise indicated, are relative to the orientation of the elements shown in the drawings.

Referring to fig. 3, fig. 3 is a functional block diagram of a current measuring device with a leakage current prevention function according to an embodiment of the present application. As shown in fig. 3, the current measuring device 1 with the leakage current prevention function of the present embodiment is used for measuring the current input to or output from the DUT. The current measuring device 1 may include a plurality of current measuring modules connected in parallel to the same output terminal a, and the output terminal a is electrically connected to the DUT. Here, the present embodiment shows a plurality of current measuring modules such as a current measuring module 10 (a first current measuring module), a current measuring module 12 (a second current measuring module), and a current measuring module 14. Practically, the current measuring device 1 is a small current measuring device, the small current is substantially smaller than 100nA, for example, at 10 nA ^-12 A (pA) to 10 ^-15 A (fA) of the order of magnitude. Although the embodiment shows three current measuring modules, it is not limited thereto. In one example, the number of current measuring modules in the current measuring device 1 is the number of file bits associated with the current measuring device 1, and fig. 3 shows three current measuring modules that indicate that the current measuring device 1 can correspond to at least three gears (current measuring ranges). In addition, the current measuring device 1 may further include a current measuring module for measuring a large current, so as to measure a large current and a small current respectively.

The current measuring module 10, the current measuring module 12 and the current measuring module 14 may be electrically connected in parallel between the output terminal a and the input terminal b, and each provide a current path from the input terminal b to the output terminal a. In practice, the current path (first current path) provided by the current measurement module 10 may be provided with a switch set SW10 (first switch set), a voltage controller 100 (first voltage controller) and a measurement resistor R10 (first measurement resistor) connected in series. Similarly, in the current path (second current path) provided by the current measurement module 12, a switch set SW12 (second switch set), a voltage controller 120 (second voltage controller) and a measurement resistor R12 (second measurement resistor) may be disposed in series. And, in the current path provided by the current measuring module 14, a switch set SW14, a voltage controller 140 and a measuring resistor R14 connected in series may be provided. Here, since the current measuring ranges corresponding to the

current measuring modules

10, 12 and 14 are different, the specifications of the internal components may be different, for example, the measuring resistor R10, the measuring resistor R12 and the measuring resistor R14 may be different, which is not limited in this embodiment.

In one example, the current measuring device 1 may also include other components. Referring to fig. 3 and fig. 4 together, fig. 4 is a functional block diagram of a current measuring device with a leakage current prevention function according to another embodiment of the present application. As shown, the input terminal b may be electrically connected to the power amplifier 16, the control unit 18 may be electrically connected to the current measuring module 10, the current measuring module 12 and the current measuring module 14, respectively, and the voltage monitoring module 20 may be electrically connected between the output terminal a and the control unit 18. In practice, the power amplifier 16 is a necessary component for performing the current measurement function, and those skilled in the art will understand the function of the power amplifier, and the present embodiment is not repeated here. The voltage monitoring module 20 may be configured to monitor the output voltage Va of the output terminal a at any time, and then notify the control unit 18 of the measured value of the output voltage Va. In addition, the control unit 18 may generate a control signal according to the value of the output voltage Va, and the control signal may be used to control the

voltage controllers

100, 120, and 140. Of course, it is possible for the control unit 18 to be controlled or set by a user to select whether to use the current measuring module 10, the current measuring module 12 or the current measuring module 14 to measure the current of the component DUT under test. That is, the control unit 18 has a possibility of controlling the on or off of the switch groups SW10, SW12 and SW14, and the present embodiment is not limited. In addition, the present embodiment does not limit that the control unit 18 and the voltage monitoring module 20 are disposed in the current measuring device 1, and other devices or separate circuit modules are also possible for the control unit 18 and the voltage monitoring module 20, so that the current measuring device 1 does not include the control unit 18 and the voltage monitoring module 20.

In one example, assuming current measurement module 12 is selected to measure the current of the DUT, switch set SW12 in current measurement module 12 is turned on so that current measurement module 12 is electrically connected to the DUT. At this time, since the current measuring module 10 and the current measuring module 14 are not selected, the switch set SW10 and the switch set SW14 need to be in the off state at the same time, so that the current measuring module 10 and the current measuring module 14 are not electrically connected (disconnected) to the DUT. Since the operation of the current measuring module 10 and the current measuring module 14 are substantially the same, the current measuring module 10 is only used for illustration in this embodiment. In view of the above, since the switch set SW10 of the current measuring module 10 is already turned off, the current path (first current path) formed by the switch set SW10, the voltage controller 100 and the measuring resistor R10 in the current measuring module 10 should be in a floating state. It will be understood by those skilled in the art that the floating potential of the current measurement module 10 may be lower than the potential of the output terminal a, so that the leakage current enters the current measurement module 10 from the output terminal a via the switch set SW10, resulting in an error in measuring the DUT current of the device under test. In other words, in order to avoid the influence of the non-ideal characteristics of the switch sets SW10 and SW14 on the measurement of the DUT current, the present embodiment needs to apply a guard voltage to the current paths of the current measurement module 10 and the current measurement module 14.

In actual operation, the output voltage Va at the output terminal a is measured by the voltage monitoring module 20 and provided to the control unit 18. It should be understood by those skilled in the art that the output voltage Va at the output a is the voltage of the DUT. Next, the control unit 18 generates a control signal (first control signal) according to the value of the output voltage Va, so that the current measurement module 10 provides a protection voltage (first protection voltage) on the first current path, and the protection voltage is substantially the same as the value of the output voltage Va. In detail, the voltage controller 100 in the current measuring module 10 is controlled by a control signal, and a protection voltage is provided at the reference terminal x of the voltage controller 100. Since the current measurement module 10 is originally in the floating state, after the reference terminal x of the voltage controller 100 provides the protection voltage, it can be seen that the protection voltage is given to the entire first current path. Taking the switch of the switch set SW10 on the right side of fig. 3 as an example, the protection voltage can be seen on the left side and the output voltage Va can be seen on the right side, and since the protection voltage and the output voltage Va have no voltage difference, it is theoretically possible to greatly reduce or even prevent the leakage current from entering the current measuring module 10 from the output terminal a through the switch set SW 10. The same operation manner can be applied to the current measurement module 14, and the description of this embodiment is omitted.

On the other hand, the current measuring module 12 measures the current of the DUT, and the switch set SW12 is turned on. At this time, the current I12 flowing through the second current path should be equal to the current to be measured flowing through the component to be measured DUT. That is, the current measuring module 12 only needs to measure the voltage across the measuring resistor R12 in the second current path, and can calculate the value of the current I12 in a back-pushing manner under the condition that the resistance value of the measuring resistor R12 is known, so as to obtain the current to be measured flowing through the DUT. In one example, the voltage across the measurement resistor R12 may be obtained by the voltage controller 120 and the voltage monitoring module 20. For example, the voltage controller 120 in the current measuring module 12 can measure the voltage at the reference terminal y, and in the case that the output terminal voltage Va at the output terminal a is already measured by the voltage monitoring module 20, the voltage difference between the reference terminal y and the output terminal a (both ends of the measuring resistor R12) is also known.

In another embodiment, the user may select other current measuring modules with different gears to measure the current of the DUT. For example, assuming that the current measuring module 10 is selected to measure the current of the DUT, the switch set SW10 in the current measuring module 10 is turned on, so that the current measuring module 10 is electrically connected to the DUT. Unlike the above example, since the current measuring module 12 is not selected, the switch set SW12 is turned off. Similarly, since the switch set SW12 of the current measuring module 12 is already turned off, the current path (second current path) formed by the switch set SW12, the voltage controller 120 and the measuring resistor R12 in the current measuring module 12 should be in a floating state. To avoid the non-ideal characteristics of the switch set SW12 from affecting the measurement of the DUT current, the present embodiment also applies a guard voltage to the current path of the current measurement module 12. At this time, the current measuring module 10 measures the voltage across the measuring resistor R10 in the first current path, and calculates the current flowing through the measuring resistor R10 from the voltage across the measuring resistor R10, so as to calculate the current to be measured of the DUT. The other implementation details are as described above, and are not described in detail in this embodiment.

The above examples and/or embodiments are merely for illustrating the preferred examples and/or embodiments for implementing the technology of the present application, and are not limited in any way to the embodiments of the technology of the present application, and any person skilled in the art should be able to make some changes or modifications to other equivalent examples without departing from the scope of the technical means disclosed in the present application, but should still consider the technology or examples substantially identical to the present application.

Claims

1. An electric current measuring apparatus having a leakage current prevention function, comprising:

the first current measuring module is electrically connected between an input end and an output end and is provided with a first switch group, a first voltage controller and a first measuring resistor which are connected in series with a first current path, wherein the first switch group selectively conducts the first current path to the output end; and

the second current measuring module is electrically connected between the input end and the output end and is provided with a second switch group, a second voltage controller and a second measuring resistor which are connected in series with a second current path, and the second switch group selectively conducts the second current path to the output end;

when the first switch group is turned off and the second switch group is turned on, the first voltage controller provides a first protection voltage on the first current path according to a first control signal, the first protection voltage is equal to an output end voltage of the output end, and the output end is electrically connected with a component to be tested.

2. The current measuring device with leakage current prevention function according to claim 1, further comprising a control unit electrically connected to the first current measuring module, the second current measuring module and a voltage monitoring module, wherein the voltage monitoring module is used for measuring the output voltage of the output terminal, and the control unit generates the first control signal according to the output voltage.

3. The apparatus of claim 2, wherein the first measuring resistor is electrically connected between the first voltage controller and the output terminal, and the first voltage controller is further configured to measure a first terminal voltage of the first measuring resistor when the first switch set is turned on and the second switch set is turned off, and a difference between the first terminal voltage and the output terminal voltage is a voltage across the first measuring resistor.

4. The apparatus of claim 3, wherein the voltage across the first measuring resistor is used to calculate a current to be measured of the device under test.

5. An electric current measuring apparatus having a leakage current prevention function, comprising:

the first current measuring module is electrically connected between an input end and an output end and selectively conducts a first current path to the output end; and

the second current measuring module is electrically connected between the input end and the output end and selectively conducts a second current path to the output end;

when the first current path is cut off and the second current path is conducted, the first current measuring module provides a first protection voltage to the first current path, the first protection voltage is equal to an output end voltage of the output end, and the output end is electrically connected with a component to be measured.

6. The device of claim 5, further comprising a control unit electrically connected to the first current measuring module, the second current measuring module and a voltage monitoring module, wherein the voltage monitoring module is configured to measure the output voltage of the output terminal, the control unit generates a first control signal according to the output voltage, and the first current measuring module provides the first protection voltage to the first current path according to the first control signal.

7. The apparatus of claim 6, wherein the first current measuring module measures a voltage across a first measuring resistor in the first current path when the first current path is on and the second current path is off, the voltage across the first measuring resistor being related to a current to be measured of the device under test.