Multi-range current measuring circuit

Abstract

The utility model relates to the technical field of current measurement, in particular to a multi-range current measurement circuit. The system comprises multiple stages of current measurement branches, the multiple stages of current measurement branches work in parallel, a first-stage current measurement branch is connected to a TP point, a to-be-measured current I flows through the TP point and flows to the multiple stages of current measurement branches from the TP point, and the level of the TP point is kept equal to the ground level after being measured and controlled by the first-stage current measurement branch. A current I to be measured is decomposed into parallel current I1-In of multiple stages of current measurement branches to be measured respectively, n represents a serial number corresponding to each stage of current measurement branch, the first stage of current measurement branch is continuously in a starting state and bears measurement of a minimum current gear, the measurement voltage of the first stage of current measurement branch serves as a control signal, and the first stage of current measurement branch is connected with the control signal. Therefore, starting or stopping of shunting work of all post-stage current measurement branches is controlled. According to the utility model, the problems of switch shift current abrupt change and sampling resistor voltage drop in the current measurement technology are solved.

Description

Technical Field

[0001] This utility model relates to the field of current measurement technology, and in particular to a multi-range current measurement circuit. Background Technology

[0002] With the widespread use of low-voltage power supplies, more and more handheld electronic devices are using them, leading to an increasing demand for power consumption testing during electronic device manufacturing. Current technologies for micro-current testing often rely on switching between ranges on a multimeter, similar to range switches. When using an MCU (microcontroller unit) for automatic switching, the MCU must perform calculations and interpretations. A fixed-value sampling resistor has a limited applicable current measurement range. When the current in the circuit varies significantly, it is necessary to use multiple current sampling resistors with different resistance values, switching them sequentially. Figure 1 As shown, the series sampling resistor switching circuit is as follows: Figure 2 As shown, a parallel sampling resistor switching circuit.

[0003] In existing measurement circuits, when a switch is used to switch the sampling resistor, the current through the sampling resistor changes abruptly, resulting in circuit interference and inaccurate sampling. For example... Figure 3 As shown, the circuit current I = 1mA, sampling resistor R1 = 100 ohms, and sampling resistor R2 = 1 ohm. With switch SW1 open, the sampling resistors are set to R1 + R2 = 100 + 1 = 101 ohms, and the total voltage across the two sampling resistors is 101mV. When a switch shift occurs, as... Figure 4 As shown, when SW1 closes for range switching, R1 is short-circuited to 0 ohms by the switch. The sampling resistor is set to R1+R2=0+1=1 ohm. At the instant the switch closes, because the voltage across the sampling resistor was previously 101mV, it is instantaneously applied across resistor R2, causing the sampling current to suddenly change to 101mV / 1 ohm = 101mA. This 101mA is clearly not the normal current of 1mA in the circuit, leading to inaccurate sampling and circuit interference. Therefore, it is evident that interference from sudden changes in switching current is an unsolvable system problem for switch-range switching technology. Furthermore, in existing measurement circuits, the current sampling resistor is connected in series in the circuit under test, such as... Figure 5 As shown, the current I = V / R is obtained by measuring the voltage drop V across the current sampling resistor. This voltage drop V across the sampling resistor is also a system problem. Although the voltage drop is sometimes only 0.1V-0.2V, it is still unbearable for low-voltage chips. Utility Model Content

[0004] This invention provides a multi-range current measurement circuit, which aims to solve the problems of sudden current changes during switching and voltage drop of sampling resistors in existing current measurement technologies.

[0005] This utility model provides a multi-range current measurement circuit, including multiple current measurement branches. The multiple current measurement branches operate in parallel. The first-stage current measurement branch is connected to point TP. The current to be measured, I, flows through point TP and from point TP to the multiple-stage current measurement branches. The level of point TP is maintained at the same level as ground after being measured and controlled by the first-stage current measurement branch. The current to be measured, I, is decomposed into parallel currents I1-In of the multiple-stage current measurement branches for separate measurement. n represents the sequence number of each current measurement branch. The first-stage current measurement branch is always in the start state and undertakes the measurement of the minimum current range. The measurement voltage of the first-stage current measurement branch is used as a control signal to control the start or stop of the current shunting operation of all subsequent current measurement branches.

[0006] As a further improvement of this utility model, the first-stage current measurement branch includes an operational amplifier U1, a current sampling resistor R1, a voltage measurement module V1, and a current amplifier IF1, n=1. The IN+ terminal of the operational amplifier U1 is grounded, and the IN- terminal of the operational amplifier U1 is connected to the point TP through which the current to be measured passes. The output terminal of the operational amplifier U1 is connected to the current amplifier IF1. The voltage measurement module V1 is connected to both ends of the current sampling resistor R1 and obtains the voltage signal of the first-stage current measurement branch. One end of the current amplifier IF1 is connected to the current sampling resistor R1, and the other end of the current amplifier IF1 is connected to the negative power supply.

[0007] As a further improvement of this utility model, the subsequent current measurement branch includes an operational amplifier Un, a current sampling resistor Rn, a voltage measurement module Vn, and a current amplifier IFn. Each of the subsequent current measurement branches is set with its own start-up threshold voltage Bn, n≥2. The IN+ terminal of the operational amplifier Un is connected to the voltage signal V1 of the first-stage current measurement branch, the IN- terminal of the operational amplifier Un is connected to the start-up threshold voltage Bn, the output terminal of the operational amplifier Un is connected to the current amplifier IFn, the voltage measurement module Vn is connected across the current sampling resistor Rn and obtains the voltage of the current measurement branch, one end of the current amplifier IFn is connected to the current sampling resistor Rn, and the other end of the current amplifier IFn is connected to the negative power supply.

[0008] As a further improvement of this utility model, when the voltage signal V1 of the first-stage current measurement branch exceeds the start-up threshold voltage Bn, the current amplifier IFn of that stage immediately starts parallel current shunting; when the voltage signal V1 of the first-stage current measurement branch is lower than the start-up threshold voltage Bn, the current amplifier IFn of that stage immediately shuts down and exits parallel current shunting.

[0009] As a further improvement of this utility model, the starting threshold voltage of each current measurement branch increases sequentially from small to large, B2 <B3<...<Bn。

[0010] As a further improvement of this utility model, the resistance values ​​of the current sampling resistors in each current measurement branch decrease sequentially from large to small, R1>R2>...>Rn.

[0011] As a further improvement of this utility model, if the maximum current output value of the operational amplifier in a certain current measurement branch is greater than or equal to the current measurement value of that level, then the current amplifier of that current measurement branch is omitted, and the operational amplifier of that current measurement branch replaces the current amplifier of that level, and the output terminal of the operational amplifier of that current measurement branch is connected to a current sampling resistor.

[0012] As a further improvement of this utility model, the current sampling resistors R1, R2...Rn of each current measurement branch are connected in parallel to the TP point.

[0013] As a further improvement of this utility model, the current sampling resistors R1, R2...Rn of each current measurement branch are connected in series from beginning to end and then connected to point TP.

[0014] As a further improvement of this utility model, when the current to be measured I increases from small to large, the current measurement branch of the subsequent stage is started in order of increasing n value to join the parallel current shunting; when the current to be measured I decreases from large to small, the current measurement branch of the subsequent stage is shut down in order of increasing n value to exit the parallel current shunting.

[0015] The beneficial effects of this invention are as follows: It constructs a multi-range current measurement circuit, which expands the measurement range through multi-range parallel current measurement technology. It does not use a switch to switch the range, thus solving the switching interference problem in existing multi-range current measurement technologies. In addition, this multi-range current measurement circuit converts the current to be measured into a negative current channel for measurement. It does not use a sampling resistor in the current loop to be measured, and does not generate a resistance voltage drop for the circuit under test, thus solving the sampling resistor voltage drop problem in existing multi-range current measurement technologies. Attached Figure Description

[0016] Figure 1 It is an existing multi-range technology circuit diagram - series sampling resistor switching circuit;

[0017] Figure 2 It is an existing multi-range technology circuit diagram - parallel sampling resistor switching circuit;

[0018] Figure 3 This is the circuit diagram of existing multi-range technology - the circuit for the gear shift switch in the open state;

[0019] Figure 4 This is the circuit diagram of existing multi-range technology - the circuit of the shift switch closed state;

[0020] Figure 5 This is an existing multi-range technology circuit diagram - current sampling resistor and voltage drop circuit;

[0021] Figure 6 This is a circuit structure diagram of the multi-range current measurement circuit of this utility model;

[0022] Figure 7 This is a circuit structure diagram of a specific implementation example of the multi-range current measurement of this utility model;

[0023] Figure 8 This is a circuit diagram of another specific implementation of the multi-range current measurement of this utility model. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments.

[0025] like Figure 6 As shown, this utility model discloses a multi-range current measurement circuit, including multiple current measurement branches that operate in parallel. The first-stage current measurement branch is connected to point TP. The current to be measured, I, flows through point TP and from point TP to the multiple-stage current measurement branches. The level of point TP is maintained at the same level as ground after being measured and controlled by the first-stage current measurement branch. The current to be measured, I, is decomposed into parallel currents I1~In of the multiple-stage current measurement branches for separate measurement. n represents the sequence number of each current measurement branch. The first-stage current measurement branch is always in the start state and undertakes the measurement of the minimum current range. The measurement voltage of the first-stage current measurement branch serves as a control signal to control the start or stop of the current shunting operation of all subsequent current measurement branches.

[0026] The current to be measured, I, flows through point TP and from TP to the multi-stage current measurement branch. The current I is decomposed into parallel currents I1~In of the multi-stage current measurement branch for separate measurement. I1 is the minimum range, In is the maximum range, and I1~In increase sequentially. The sum of I1~In is the current to be measured, which is the current I. The parallel multi-range current measurement circuit includes multiple current measurement branches. Each current measurement branch includes an operational amplifier Un, a current sampling resistor Rn, a voltage measurement module Vn, and a current amplifier IFn, where n represents the sequence number of each current measurement branch (1, 2, 3, ...).

[0027] The multi-stage current measurement branches operate in parallel. Except for the first-stage current measurement branch which is continuously running, all subsequent current measurement branches are controlled by the first-stage current measurement branch. They are connected or disconnected in parallel as needed to adapt to changes in the magnitude of the measured current I. The connection or disconnection of each current measurement branch is a smooth connection from zero current to large current and a smooth disconnection from large current to zero current, without sudden current changes, thus avoiding circuit interference.

[0028] The first-stage current measurement branch includes an operational amplifier U1, a current sampling resistor R1, a voltage measurement module V1, and a current amplifier IF1, with n=1. The IN+ terminal of the operational amplifier U1 is grounded, and the IN- terminal of the operational amplifier U1 receives the measured current through point TP. The output terminal of the operational amplifier U1 is connected to the current amplifier IF1. The voltage measurement module V1 is connected across the current sampling resistor R1 and acquires the voltage signal of the first-stage current measurement branch. One end of the current amplifier IF1 is connected to the current sampling resistor R1, and the other end of the current amplifier IF1 is connected to the negative power supply.

[0029] The current I to be measured, after flowing through point TP, is not directly connected to ground. Instead, it is measured in stages by a multi-range measurement circuit before reaching the negative power supply. The level of point TP is detected and controlled by the IN- pin of the first-stage current measurement branch to maintain it equal to the ground level, which is equivalent to the effect of point TP being directly connected to ground. The IN+ pin of the operational amplifier U1 in the first-stage current measurement branch is grounded, and the IN- pin is connected to point TP. The function of operational amplifier U1 is to continuously monitor the level of point TP. By controlling the current amplifiers in this stage and the subsequent stage, the current I to be measured is directed to the negative current path, so that the level of point TP is equal to the level of the IN+ pin, and point TP is kept at ground level. The advantage of this is that there is no current sampling resistor directly used in the circuit where the current I to be measured flows to ground level, so no voltage drop occurs and there is no voltage loss in the circuit under test.

[0030] The subsequent current measurement branch includes an operational amplifier Un, a current sampling resistor Rn, a voltage measurement module Vn, and a current amplifier IFn. Each subsequent current measurement branch has its own start-up threshold voltage Bn, where n≥2. The IN+ terminal of the operational amplifier Un is connected to the voltage signal V1 of the first-stage current measurement branch, and the IN- terminal of the operational amplifier Un is connected to the start-up threshold voltage Bn. The output terminal of the operational amplifier Un is connected to the current amplifier IFn. The voltage measurement module Vn is connected across the current sampling resistor Rn and obtains the voltage of this stage of the current measurement branch. One end of the current amplifier IFn is connected to the current sampling resistor Rn, and the other end of the current amplifier IFn is connected to the negative power supply.

[0031] For example, the second-stage current measurement branch includes an operational amplifier U2, a current sampling resistor R2, a voltage measurement module V2, and a current amplifier IF2. The IN+ terminal of the operational amplifier U2 is connected to the voltage signal V1 of the first-stage current measurement branch, the IN- terminal of the operational amplifier U2 is connected to the start-up threshold voltage B2, and the output terminal of the operational amplifier U2 is connected to the current amplifier IF2.

[0032] The third-stage current measurement branch includes operational amplifier U3, current sampling resistor R3, voltage measurement module V3, and current amplifier IF3. The IN+ terminal of operational amplifier U3 is connected to the voltage signal V1 of the first-stage current measurement branch, the IN- terminal of operational amplifier U3 is connected to the start-up threshold voltage B3, and the output terminal of operational amplifier U3 is connected to current amplifier IF3. And so on.

[0033] When the voltage signal V1 of the first-stage current measurement branch exceeds the start-up threshold voltage Bn, the current amplifier IFn of that stage immediately starts parallel current shunting; when the voltage signal V1 of the first-stage current measurement branch is lower than the start-up threshold voltage Bn, the current amplifier IFn of that stage immediately shuts down and exits parallel current shunting. The first-stage current measurement branch continues to operate and undertakes the measurement of the minimum current range. The subsequent current measurement branches start immediately when the set start-up threshold voltage is reached and shut down immediately when the voltage is lower than the start-up threshold voltage.

[0034] The starting threshold voltages of each current measurement branch increase sequentially from small to large, B2 <B3<...<Bn。

[0035] The resistance values ​​of the current sampling resistors in each current measurement branch decrease sequentially, R1>R2>...>Rn. The current measurement branch has multiple stages, at least two stages, using current sampling resistors with different resistance values ​​to measure currents within different ranges. A larger resistance value results in a smaller measured current, and a smaller resistance value results in a larger measured current, R1>R2>...>Rn, I1 <I2<...<In。

[0036] The current sampling resistors R1, R2...Rn of each current measurement branch are connected in parallel to point TP. Each current measurement branch draws current from the same current node TP, thus exhibiting a parallel relationship.

[0037] All current measurement branches are parallel shunt currents. The detection voltage V1 of the first-stage current measurement branch is used as the control parameter. When the current to be measured I increases, the subsequent current measurement branches are started in order of increasing n value to join the parallel shunt current. When the current to be measured I decreases, the subsequent current measurement branches are shut down in order of increasing n value to exit the parallel shunt current.

[0038] Example 1:

[0039] If the maximum current output value of the operational amplifier in a certain current measurement branch is greater than or equal to the current measurement value of that range, then the current amplifier for that current measurement branch is omitted, and the operational amplifier of that current measurement branch replaces the current amplifier of that stage. Furthermore, the output terminal of the operational amplifier of that current measurement branch is connected to a current sampling resistor. In all current measurement branches, if the current output capability of the operational amplifier in that branch is sufficient to handle the current range of that stage, then the operational amplifier of that branch replaces the current amplifier circuit IFn of that stage, and the current amplifier circuit IFn of that stage can be omitted.

[0040] like Figure 7 As shown, a wide-range measurement circuit with a test current range of 1uA-1A is designed, with the ratio of the maximum current to the minimum current being 1 million times. The design uses a three-stage current measurement branch. The first-stage current measurement branch 1 and the second-stage current measurement branch 2 omit the current amplifier circuit IFn.

[0041] In the first-stage current measurement branch 1, the sampling circuit R1 = 1000 ohms, and the current range I1 of the first-stage current measurement branch 1 is approximately 1uA-300uA;

[0042] In the second-stage current measurement branch 2, the sampling circuit R2 = 10 ohms, the current range I2 of the second-stage current measurement branch 2 is approximately 100uA-20mA, and the start-up threshold voltage is set to 0.1V.

[0043] In the third-stage current measurement branch 3, the sampling circuit R3 = 0.1 ohms, the current range I3 of the third-stage current measurement branch 3 is approximately 10mA-1A, and the start-up threshold voltage is set to 0.2V.

[0044] Currently, suitable operational amplifiers can support output currents of 30mA-40mA. For the first-stage current measurement branch 1 and the second-stage current measurement branch 2, since the current range of the branch is small, operational amplifiers can be used directly to pass the ranged currents. Therefore, the current amplifier circuits IF1 and IF2 of the first-stage current measurement branch 1 and the second-stage current measurement branch 2 are omitted. The current of the third-stage current measurement branch 3 is larger, so the current amplifier circuit IF3 needs to be used.

[0045] When the current to be measured is 0uA≤I<100uA, the current passing through the first-stage current measurement branch 1 is I1=I, V1=R1×I1=1000×I1, and we can calculate that 0mV≤V1<100mV. At this time, V1 does not reach the start-up threshold voltages of 0.1V and 0.2V of the second-stage current measurement branch 2 and the third-stage current measurement branch 3, respectively. Therefore, the second-stage current measurement branch 2 and the third-stage current measurement branch 3 are both in the closed state.

[0046] When I = 1uA, we get: V1 = 1mV, I1 = 1uA;

[0047] When I = 10uA, we get: V1 = 10mV, 1 = 10uA;

[0048] When the measured current is 100uA ≤ I < 10mA, assuming the entire current flows through the first-stage current measurement branch 1, then V1 = R1 × I1 = 1000 × I1. Calculations show V1 ≥ 100mV. At this point, V1 first reaches the starting threshold voltage of the second-stage current measurement branch 2 (0.1V). The second-stage current measurement branch 2 then starts current shunting. The current shunting calculation is as follows, where the formulas assume international standard units: current is in amperes (A), resistance is in ohms (Ω), and voltage is in volts (V):

[0049] I = I1 + I2,

[0050] V1 = R1 × I1 = 1000 × I1,

[0051] V2 = V1 - 0.1 = R2 × I2 = 10 × I2,

[0052] For any current I to be measured, I1, I2, V1, and V2 can be obtained by combining the above three formulas, as shown below:

[0053] V1 = (1000 × I + 10) / 101 (volts).

[0054] V2 = (1000 × I - 0.1) / 101 (volts)

[0055] I1 = (I + 0.01) / 101 (Amperes).

[0056] I2 = (100 × I - 0.01) / 101 (Amperes).

[0057] When I = 100uA, we get: V1 = 100mV, V2 = 0V, I1 = 100uA, I2 = 0A;

[0058] When I = 200uA, we get: V1 = 101mV, V2 = 0.99mV, I1 = 101uA, I2 = 99uA;

[0059] When I = 1mA, we get: V1 = 108.9mV, V2 = 8.91mV, I1 = 108.9uA, I2 = 891.1uA;

[0060] When I = 10mA, we get: V1 = 198.0mV, V2 = 98.02mV, I1 = 198.0uA, I2 = 9.802mA;

[0061] When I = 10.2mA, we get: V1 = 200mV, V2 = 100mV, I1 = 200uA, I2 = 10mA;

[0062] It can be seen that when the measured current I is 10mA, V1 is 198mV, which is very close to the starting threshold voltage of 200mV of the third-level current measurement branch 3. When the measured current I rises to 10.2mA, V1 reaches the starting threshold voltage of 200mV of the third-level current measurement branch 3.

[0063] When the current to be measured is 10.2mA≤I≤1A, the third-level current measurement branch 3 starts, and all three current measurement branches work simultaneously. The current shunting calculation is as follows.

[0064] I = I1 + I2 + I3,

[0065] V1 = R1 × I1 = 1000 × I1,

[0066] V2 = V1 - 0.1 = R2 × I2 = 10 × I2,

[0067] V3 = V1 - 0.2 = R3 × I3 = 0.1 × I3,

[0068] For any current I to be measured, I1, I2, I3, V1, V2, and V3 can be obtained by combining the above four formulas, as shown below:

[0069] V1 = (1000 × I + 2010) / 10101 (volts).

[0070] V2 = (1000 × I + 999.9) / 10101 (volts).

[0071] V3 = (1000 × I - 10.2) / 10101 (volts)

[0072] I1 = (I + 2.01) / 10101 (Amperes).

[0073] I² = (100 × I + 99.99) / 10¹⁰¹ (Amperes).

[0074] I3 = (10000 × I - 102) / 10101 (Amperes).

[0075] When I = 10.2mA, we get: V1 = 200mV, V2 = 100mV, V3 = 0V, I1 = 200uA, I2 = 10mA, I3 = 0A;

[0076] When I = 20mA, we get: V1 = 200.97mV, V2 = 100.97mV, V3 = 0.9702mV, I1 = 200.97uA, I2 = 10.097mA, I3 = 9.702mA;

[0077] When I = 100mA, we get: V1 = 208.89mV, V2 = 108.89mV, V3 = 8.89mV, I1 = 208.89uA, I2 = 10.889mA, I3 = 88.9mA;

[0078] When I=1A, we get: V1=297.99mV, V2=197.99mV, V3=97.99mV, I1=297.99uA, I2=19.799mA, I3=979.9mA.

[0079] Since V1, V2, and V3 refer to the voltages across R1, R2, and R3 respectively, one end of the current sampling resistors R1, R2, and R3 is connected in parallel, while the other end is independent. The voltage across the current sampling resistor is related to the magnitude of the current passing through it.

[0080] The calculation results are summarized in the tables, as shown in Table 1 and Table 2.

[0081]

[0082] Table 1

[0083]

[0084] Table 2

[0085] Through the demonstration of the above practical design examples, some features of the multi-stage parallel current measurement scheme of this utility model can be further seen:

[0086] (1) When the measured current I increases from 1uA to 1A, V1 and I1 rise rapidly in the initial stage, slow down after the second-level measurement branch 2 is started, and slow down even more after the third-level measurement branch 3 is started. This indicates that when a larger range measurement branch is started and connected in parallel, the newly added current mainly flows to the newly started branch.

[0087] (2) The three current measurement branches are responsible for current shunting and measurement in different ranges, and the changes are small when they approach the upper limit of their own range.

[0088] (3) When the second-level current measurement branch 2 and the third-level current measurement branch 3 reach the start-up threshold voltage, they both start from 0 current and enter the shunt state in parallel. This has no effect on the current state before parallel connection. This is also an advantage of the multi-range current measurement circuit of this utility model. When the parallel range is extended, it starts from 0 current state, so there is no circuit interference problem caused by sudden current change.

[0089] In the above actual design case, the control function for the current shunting of the subsequent current in the first-stage current measurement branch 1 is a linear equation: Vn=V1-Bn=Rn×In, V1≥Bn. Other linear or nonlinear equations can also be used as control functions to obtain different shunting ratio effects.

[0090] The above actual design case only uses a three-level parallel scheme as an example. It can be 2, 3, 4, 5, etc., with different numbers of levels and different current ranges.

[0091] The above practical design case uses the detection of DC current as a demonstration to illustrate the working principle of the circuit. The current to be measured is also applicable to the measurement of AC current.

[0092] The above practical design case demonstrates measuring the current from point TP, where the current to be measured I is connected to the ground terminal. However, the current can also be measured from other circuit connection points by changing the circuit configuration.

[0093] Example 2:

[0094] The current sampling resistors R1, R2...Rn of each current measurement branch are connected in series to point TP. This series connection allows the larger current sampling resistor in the previous stage to share the smaller current sampling resistor in the next stage. The current sampling voltage of the next stage is superimposed on the current sampling voltage of the previous stage, enabling the previous stage current measurement branch to detect changes in the subsequent stage current measurement branch in advance.

[0095] like Figure 8 In another preferred embodiment of this utility model, the current sampling resistors R1, R2...Rn are connected in series to point TP. Point TP is first connected to one end of the current sampling resistor Rn of the nth current measurement branch n. The other end of the current sampling resistor Rn is simultaneously connected to one end of the current sampling resistor R(n-1) and the current amplifier IFn of the nth current measurement branch n. The other end of the current sampling resistor R(n-1) is connected to one end of the current sampling resistor R(n-2) and the current amplifier IF(n-1) of the (n-1)th current measurement branch (n-1). And so on, ... The other end of the current sampling resistor R2 is connected to one end of the current sampling resistor R1 and the current amplifier IF2 of the second-stage current measurement branch 2. The other end of the current sampling resistor R1 is connected to the current amplifier IF1 of the first-stage current measurement branch 1.

[0096] Figure 8 The circuit diagram of the preferred embodiment shown still adheres to the basic working principle of multi-stage parallel current measurement. The first-stage current measurement branch 1 is continuously in the start-up state and undertakes the measurement of the smallest current stage. The measurement voltage V1 of the first-stage current measurement branch 1 is also used as a control parameter to control the current shunting operation of all subsequent current measurement branches. Each subsequent current measurement branch is equipped with its own start-up threshold voltage Bn. When V1 exceeds the start-up threshold voltage Bn of a certain stage, the current amplifier IFn of that stage immediately starts parallel current shunting. When V1 is lower than the threshold voltage Bn, the current amplifier IFn of that stage immediately shuts down and exits parallel current shunting. The resistance values ​​of the sampling resistors R1, R2...Rn of each stage decrease sequentially from large to small, R1>R2...>Rn. The start-up threshold voltage values ​​B2, B3...Bn of each stage increase sequentially from small to large, B2...Bn ... <B3...<Bn。

[0097] This implementation method simplifies circuit connections and current calculations; design examples will not be repeated here.

[0098] This invention relates to a multi-range current measurement circuit that extends the measurement range through multi-range parallel current measurement technology. It eliminates the need for switches to change ranges and avoids the use of sampling resistors in the circuit where the measured current reaches ground level. This solves the problems of switch interference and sampling resistor voltage drop in current multi-range current measurement technologies.

[0099] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the protection scope of the present invention.

Claims

1. A multi-range current measurement circuit, characterized in that, The system includes multiple current measurement branches, which operate in parallel. The first-stage current measurement branch includes an operational amplifier U1, a current sampling resistor R1, a voltage measurement module V1, and a current amplifier IF1, where n=1, and n represents the sequence number of each current measurement branch. The IN+ terminal of the operational amplifier U1 is grounded, and the IN- terminal of the operational amplifier U1 is connected to the TP point through which the measured current passes. The output terminal of the operational amplifier U1 is connected to the current amplifier IF1. The voltage measurement module V1 is connected across the current sampling resistor R1 and acquires the voltage signal of the first-stage current measurement branch. One end of the current amplifier IF1 is connected to the current sampling resistor R1, and the other end of the current amplifier IF1 is connected to the negative power supply. The first-stage current measurement branch is continuously in the start-up state and undertakes the measurement of the minimum current level. The measured voltage of the first-stage current measurement branch serves as a control signal to control the start-up or shutdown of the current shunting operation of all subsequent current measurement branches.

2. The multi-range current measurement circuit according to claim 1, characterized in that, The subsequent current measurement branch includes an operational amplifier Un, a current sampling resistor Rn, a voltage measurement module Vn, and a current amplifier IFn. Each of the subsequent current measurement branches is set with its own start-up threshold voltage Bn, where n≥2. The IN+ terminal of the operational amplifier Un is connected to the voltage signal of the first-stage current measurement branch, and the IN- terminal of the operational amplifier Un is connected to the start-up threshold voltage Bn. The output terminal of the operational amplifier Un is connected to the current amplifier IFn. The voltage measurement module Vn is connected across the current sampling resistor Rn and obtains the voltage of this stage of the current measurement branch. One end of the current amplifier IFn is connected to the current sampling resistor Rn, and the other end of the current amplifier IFn is connected to the negative power supply.

3. The multi-range current measurement circuit according to claim 2, characterized in that, The start-up threshold voltages of the current measurement branches at each stage increase sequentially from small to large, B2 <B3<...<Bn。 4. The multi-range current measurement circuit according to claim 2, characterized in that, The resistance values ​​of the current sampling resistors in each current measurement branch decrease sequentially from large to small: R1>R2>...>Rn.

5. The multi-range current measurement circuit according to claim 2, characterized in that, The current sampling resistors R1, R2...Rn of each current measurement branch are connected in parallel to point TP.

6. The multi-range current measurement circuit according to claim 2, characterized in that, The current sampling resistors R1, R2...Rn of each current measurement branch are connected in series from beginning to end and then connected to point TP.

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