Multi-range current measuring circuit

Abstract

The invention relates to the technical field of current measurement, in particular to a multi-range current measurement circuit. The multi-level current measuring circuit comprises multi-level current measuring branches, the multi-level current measuring branches work in parallel, the first-level current measuring branch is connected to a TP point, current to be measured flows through the TP point and flows to the multi-level current measuring branches from the TP point, and the current to be measured is decomposed into parallel current of the multi-level current measuring branches to be measured respectively. The first-stage current measurement branch is continuously in a starting state and bears measurement of the minimum current gear, and the measurement voltage of the first-stage current measurement branch serves as a control signal to control starting or stopping of shunting work of all the rear-stage current measurement branches; the parallel connection of each stage of current measurement branch is smoothly connected from small to large from a zero current state, and the parallel quit of each stage of current measurement branch is smoothly quit from large to small to the zero current state. According to the invention, the problems of switch shift current abrupt change and sampling resistor voltage drop in the current measurement technology are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of current measurement, and in particular to a multi-range current measurement circuit. Background Art

[0002] With the widespread use of low-voltage power supplies, more and more handheld electronic devices are used with low-voltage power supplies. When producing electronic equipment, power consumption testing of electronic equipment is increasingly used. In the process of micro-current testing, the existing technology mostly uses switch shifting to achieve current measurement of different intervals, similar to the gear switch of a multimeter. When the MCU (single-chip microcomputer) automatically switches, the MCU must perform calculations and interpretations. The measurement current range applicable to a sampling resistor with a fixed resistance is limited. When the current in the circuit changes greatly, it is necessary to use a variety of current sampling resistors with different resistance values, and use switches to switch in turn. For example Figure 1 As shown, the series sampling resistor switching circuit is Figure 2 As shown, a parallel sampling resistor switching circuit is shown.

[0003] In the measurement circuit of the prior art, when a switch is used to switch the sampling resistor, the current passing through the sampling resistor changes suddenly, thereby causing circuit interference and inaccurate sampling. Figure 3 As shown, the circuit current I = 1mA, the sampling resistor R1 = 100 ohms, the sampling resistor R2 = 1 ohm, when the switch SW1 is open, the sampling resistor is set to R1 + R2 = 100 + 1 = 101 ohms, and the voltage added to the two sampling resistors is 101mV in total. Figure 4 As shown, SW1 is closed and shifted, and the two ends of R1 are short-circuited to 0 ohms by the switch. The sampling resistor is set to R1+R2=0+1=1 ohm. At the moment the switch is closed, the voltage across the sampling resistor is 101mV before, and it is instantly added to the resistor R2. The sampling current suddenly changes to 101mV / 1 ohm=101mA. This 101mA is obviously not the normal current of the circuit, 1mA, which leads to inaccurate sampling and circuit interference. It can be seen that for the switch shifting technology, interference caused by sudden changes in the switch current is an unsolvable system problem. In addition, in the measurement circuit of the prior art, the current sampling resistor is connected in series in the circuit loop to be measured, such as Figure 5 As shown, the voltage drop V on the current sampling resistor is measured to obtain the current I=V / R. This sampling resistor voltage drop V is also a system problem. Although the voltage drop is sometimes only 0.1V-0.2V, it is unbearable for low-voltage chips. Summary of the invention

[0004] The invention provides a multi-range current measurement circuit, aiming to solve the problem of switch shift current mutation and sampling resistor voltage drop in the existing current measurement technology.

[0005] The present invention provides a multi-range current measurement circuit, comprising a multi-stage current measurement branch, wherein the multi-stage current measurement branches work in parallel, the first-stage current measurement branch is connected to a TP point, a current I to be measured flows through the TP point and flows from the TP point to the multi-stage current measurement branches, the current I to be measured is decomposed into parallel currents I1-In of the multi-stage current measurement branches for separate measurements, n represents a sequence number corresponding to each stage of the current measurement branch, the first-stage current measurement branch is continuously in a startup state and undertakes the measurement of the minimum current gear, the measurement voltage of the first-stage current measurement branch is used as a control signal to control the startup or shutdown of the shunting work of all the subsequent-stage current measurement branches, the parallel connection of each stage of the current measurement branch is smoothly connected from a zero current state from small to large, and the parallel exit of each stage of the current measurement branch is smoothly exited from a large to small to a zero current state.

[0006] As a further improvement of the present invention, the first-level 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, the IN- terminal of the operational amplifier U1 is connected to the TP point 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-level 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 the present invention, the current measurement branch of the rear stage includes an operational amplifier Un, a current sampling resistor Rn, a voltage measurement module Vn, and a current amplifier IFn. The current measurement branches of the rear stage are all set with their own starting threshold voltages Bn, n≥2, the IN+ end of the operational amplifier Un is connected to the voltage signal V1 of the first-stage current measurement branch, the IN- end of the operational amplifier Un is connected to the starting threshold voltage Bn, the output end of the operational amplifier Un is connected to the current amplifier IFn, the voltage measurement module Vn is connected to both ends of the current sampling resistor Rn and obtains the voltage of the current measurement branch of this stage, 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 the present invention, when the voltage signal V1 of the first-stage current measurement branch exceeds the starting threshold voltage Bn, the current amplifier IFn of this stage immediately starts parallel shunting; when the voltage signal V1 of the first-stage current measurement branch is lower than the starting threshold voltage Bn, the current amplifier IFn of this stage immediately shuts down and exits parallel shunting.

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

[0010] As a further improvement of the present invention, the resistance values ​​of the current sampling resistors of the current measurement branches of each level decrease from large to small in sequence, R1>R2>...>Rn.

[0011] As a further improvement of the present invention, if the maximum current output value of the operational amplifier in a current measurement branch of a certain level is greater than or equal to the current measurement value of the gear position of that level, the current amplifier of that level of current measurement branch is omitted, and the operational amplifier of that level of current measurement branch replaces the current amplifier of that level, and the output end of the operational amplifier of that level of current measurement branch is connected to the current sampling resistor.

[0012] As a further improvement of the present invention, the current sampling resistors R1, R2, ...Rn of the current measurement branches at each level are connected in parallel to the TP point.

[0013] As a further improvement of the present invention, the current sampling resistors R1, R2, ..., Rn of the current measurement branches at each level are sequentially connected in series end to end and then connected to the TP point.

[0014] As a further improvement of the present invention, when the current I to be measured changes from small to large, the current measurement branch of the subsequent stage is started from small to large in the order of increasing n values ​​to join the parallel shunt; when the current I to be measured changes from large to small, the current measurement branch of the subsequent stage is closed from large to small in the order of increasing n values ​​to exit the parallel shunt.

[0015] The beneficial effects of the present invention are as follows: a multi-range current measurement circuit is constructed, the range is expanded by a multi-speed parallel current measurement technology, and no switch is used to switch the gears, which can solve the switch interference problem in the existing multi-range current measurement technology; in addition, the multi-range current measurement circuit converts the current to be measured into a negative current channel for measurement, and no sampling resistor is used in the current loop to be measured, and no resistance voltage drop is generated for the circuit to be measured, which can solve the sampling resistor voltage drop problem in the existing multi-range current measurement technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is the existing multi-range technology circuit diagram - series sampling resistor switching circuit; Figure 2 It is the existing multi-range technology circuit diagram - parallel sampling resistor switching circuit; Figure 3 It is the existing multi-range technology circuit diagram - the shift switch open state circuit; Figure 4 It is the existing multi-range technology circuit diagram - the shift switch closed state circuit; Figure 5 It is the existing multi-range technology circuit diagram - current sampling resistor and voltage drop circuit; Figure 6 It is a circuit structure diagram of a multi-range current measurement circuit of the present invention; Figure 7 It is a circuit structure diagram of a specific implementation case of multi-range current measurement of the present invention; Figure 8 It is a circuit structure diagram of another specific implementation case of multi-range current measurement of the present invention; Fig. 9 It is a summary table of current calculation results of a specific implementation case of multi-range current measurement in the present invention; Fig.10 It is a summary table of voltage calculation results of a specific implementation case of multi-range current measurement in the present invention. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0018] like Figure 6 As shown, a multi-range current measurement circuit of the present invention includes a multi-stage current measurement branch, the multi-stage current measurement branch works in parallel, the first-stage current measurement branch is connected to the TP point, the current I to be measured flows through the TP point and flows from the TP point to the multi-stage current measurement branch, the current I to be measured is decomposed into parallel currents I1~In of the multi-stage current measurement branches for separate measurement, n represents the serial number corresponding to each stage of the current measurement branch, the first-stage current measurement branch is continuously in the startup state and undertakes the measurement of the minimum current gear, the measurement voltage of the first-stage current measurement branch is used as a control signal to control the start or shutdown of the shunting work of all the subsequent current measurement branches, the parallel connection of each stage of the current measurement branch is smoothly connected from small to large from the zero current state, and the parallel exit of each stage of the current measurement branch is smoothly exited from large to small to the zero current state.

[0019] The current I to be measured flows through the TP point, and flows from the TP point to the multi-level current measurement branch. The current I to be measured is decomposed into parallel currents I1~In of the multi-level current measurement branches for separate measurement. I1 is the minimum gear, In is the maximum gear, I1~In increases in sequence, and the sum of I1~In is the current I to be measured. The parallel multi-range current measurement circuit includes a multi-level current measurement branch, and each level of the 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 serial number 1, 2, 3... corresponding to each level of the current measurement branch.

[0020] Multi-stage current measurement branches work in parallel. Except for the first-stage current measurement branch which keeps starting, all subsequent current measurement branches are controlled by the first-stage current measurement branch and timely connected in parallel or exit the current shunting and measurement work to adapt to the change of the current I to be measured. The parallel connection or exit of each stage of current measurement branch is smoothly connected from small to large from the zero current state, and smoothly exited from large to small to zero current state, without current mutation, so no circuit interference is generated.

[0021] 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. The IN+ terminal of the operational amplifier U1 is grounded, the IN- terminal of the operational amplifier U1 is connected to the measured current passing through the TP point, 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.

[0022] After the measured current I flows through the TP point, it is not directly connected to the ground level, but reaches the negative power supply after being measured in steps by the multi-range measurement circuit. The level of the TP point is kept equal to the ground level after being detected and controlled by the IN- pin of the first-stage current measurement branch, which is equivalent to the effect of the TP point being directly connected to the ground level. The IN+ pin of the operational amplifier U1 of the first-stage current measurement branch is connected to the ground level, and the IN- pin is connected to the TP point. The function of the operational amplifier U1 is to continuously monitor the level of the TP point, and by controlling the passage of the current amplifier of this stage and the subsequent stage, the measured current I is allowed to pass through the negative current channel, so that the level of the TP point is equal to the level of the IN+ pin, and the TP point is kept at the ground level. The benefit here is that the current sampling resistor is not directly used in the circuit where the measured current I flows to the ground level, so no voltage drop is generated, and there is no voltage loss to the circuit to be measured.

[0023] The post-stage current measurement branch includes an operational amplifier Un, a current sampling resistor Rn, a voltage measurement module Vn, and a current amplifier IFn. The post-stage current measurement branches are all set with their own startup threshold voltage Bn, n≥2, the IN+ end of the operational amplifier Un is connected to the voltage signal V1 of the first-stage current measurement branch, the IN- end of the operational amplifier Un is connected to the startup threshold voltage Bn, the output end of the operational amplifier Un is connected to the current amplifier IFn, the voltage measurement module Vn is connected to both ends of the current sampling resistor Rn and obtains the voltage of the current measurement branch of this stage, 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.

[0024] For example, the second-level 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-level current measurement branch, the IN- terminal of the operational amplifier U2 is connected to the start threshold voltage B2, and the output terminal of the operational amplifier U2 is connected to the current amplifier IF2.

[0025] The third-level current measurement branch includes an operational amplifier U3, a current sampling resistor R3, a voltage measurement module V3, and a current amplifier IF3. The IN+ terminal of the operational amplifier U3 is connected to the voltage signal V1 of the first-level current measurement branch, the IN- terminal of the operational amplifier U3 is connected to the start threshold voltage B3, and the output terminal of the operational amplifier U3 is connected to the current amplifier IF3. And so on.

[0026] When the voltage signal V1 of the first-stage current measurement branch exceeds the start threshold voltage Bn, the current amplifier IFn of this stage immediately starts parallel shunting; when the voltage signal V1 of the first-stage current measurement branch is lower than the start threshold voltage Bn, the current amplifier IFn of this stage immediately shuts down and exits parallel shunting. The first-stage current measurement branch continues to work and undertakes the measurement of the minimum current range. The subsequent current measurement branch starts immediately when it reaches the set start threshold voltage, and shuts down immediately when it is lower than the start threshold voltage.

[0027] The starting threshold voltage of each level of current measurement branch increases from small to large, B2 <B3<...<Bn。

[0028] The resistance of the current sampling resistors of each current measurement branch decreases from large to small, R1>R2>...>Rn. The current measurement branch is multi-stage, not less than two stages, using current sampling resistors with different resistance values ​​to measure currents in different ranges. The larger the resistance of the current sampling resistor, the smaller the measured current, and the smaller the resistance of the sampling resistor, the larger the measured current, R1>R2>...>Rn, I1 <I2<...<In。

[0029] The current sampling resistors R1, R2, ...Rn of each current measurement branch are connected in parallel to the TP point. Each current measurement branch diverts current from the same current node TP point, presenting a parallel relationship.

[0030] All current measurement branches are parallel shunt currents, and the detection voltage V1 of the first-stage current measurement branch is used as the control parameter. When the current I to be measured changes from small to large, the subsequent current measurement branches are started from small to large in the order of increasing n values ​​to join the parallel shunt; when the current I to be measured changes from large to small, the subsequent current measurement branches are closed from large to small in the order of increasing n values ​​to exit the parallel shunt.

[0031] Embodiment 1:

[0032] If the maximum current output value of the operational amplifier in a current measurement branch of a certain level is greater than or equal to the current measurement value of the gear level, the current amplifier of the current measurement branch of this level is omitted, and the operational amplifier of the current measurement branch of this level replaces the current amplifier of this level, and the output end of the operational amplifier of the current measurement branch of this level is connected to the current sampling resistor. In all current measurement branches, if the current output capacity of the operational amplifier of this branch is sufficient to bear the current of this level, the operational amplifier of this branch replaces the current amplifier circuit IFn of this level, and the current amplifier circuit IFn of this level can be omitted.

[0033] like Figure 7 As shown, a wide-range measurement circuit with a test current range of 1uA-1A is designed, the ratio of the maximum current to the minimum current is 1 million times, and the design uses a three-level current measurement branch. The first-level current measurement branch 1 and the second-level current measurement branch 2 omit the current amplifier circuit IFn of this level.

[0034] In the first-level current measurement branch 1, the sampling circuit R1 = 1000 ohms, and the current range I1 of the first-level current measurement branch 1 is approximately 1uA-300uA; In the second-level current measurement branch 2, the sampling circuit R2 = 10 ohms, the current range I2 of the second-level current measurement branch 2 is about 100uA-20mA, and the start-up threshold voltage is set to 0.1V; In the third-level current measurement branch 3, the sampling circuit R3=0.1 ohm, the current range I3 of the third-level current measurement branch 3 is about 10mA-1A, and the start threshold voltage is set to 0.2V.

[0035] Currently, suitable operational amplifiers can support output currents of 30mA-40mA. For the first-level current measurement branch 1 and the second-level current measurement branch 2, since the branch current range passing through is small, the operational amplifier can be directly used to pass the graded current. Therefore, the current amplification circuits IF1 and IF2 of the first-level current measurement branch 1 and the second-level current measurement branch 2 are omitted. The current of the third-level current measurement branch 3 is larger, and the current amplification circuit IF3 needs to be used.

[0036] When the current to be measured is 0uA≤I<100uA, the current passes through the first-level current measurement branch 1, I1=I, V1=R1×I1=1000×I1, and 0mV≤V1<100mV is calculated. At this time, V1 cannot reach the starting threshold voltage of 0.1V and 0.2V of the second-level current measurement branch 2 and the third-level current measurement branch 3, and the second-level current measurement branch 2 and the third-level current measurement branch 3 are both in the closed state.

[0037] When I=1uA, we get: V1=1mV, I1=1uA; When I=10uA, we get: V1=10mV, 1=10uA; When the current to be measured is 100uA≤I<10mA, assuming that the entire current passes through the first-level current measurement branch 1, then V1=R1×I1=1000×I1, and V1≥100mV is calculated. At this time, V1 first reaches the start-up threshold voltage of the second-level current measurement branch 2, 0.1V, and the second-level current measurement branch 2 starts current shunting. The current shunting calculation is as follows. The formula defaults to the international standard unit, the current is ampere A, the resistance is ohm Ω, and the voltage is volt V: I=I1+I2, V1=R1×I1=1000×I1, V2=V1-0.1=R2×I2=10×I2, At this time, for any current I to be measured, I1, I2, V1, and V2 can be obtained by jointly solving the above three formulas, as shown below: V1=(1000×I+10) / 101 (volts), V2=(1000×I-0.1) / 101 (volts), I1=(I+0.01) / 101 (ampere), I2=(100×I-0.01) / 101 (ampere).

[0038] When I=100uA, we get: V1=100mV, V2=0V, I1=100uA, I2=0A; When I=200uA, we get: V1=101mV, V2=0.99mV, I1=101uA, I2=99uA; When I=1mA, we get: V1=108.9mV, V2=8.91mV, I1=108.9uA, I2=891.1uA; When I=10mA, we get: V1=198.0mV, V2=98.02mV, I1=198.0uA, I2=9.802mA; When I=10.2mA, we get: V1=200mV, V2=100mV, I1=200uA, I2=10mA; 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.

[0039] When the current to be measured is 10.2mA≤I≤1A, the third-level current measurement branch 3 is started, and the three-level current measurement branches work simultaneously. The current shunt calculation is as follows: I=I1+I2+I3, V1=R1×I1=1000×I1, V2=V1-0.1=R2×I2=10×I2, V3=V1-0.2=R3×I3=0.1×I3, At this time, for any current I to be measured, the above four formulas can be used to jointly solve I1, I2, I3, V1, V2, and V3, as shown below: V1=(1000×I+2010) / 10101 (volts), V2=(1000×I+999.9) / 10101 (volts), V3=(1000×I-10.2) / 10101 (volts), I1=(I+2.01) / 10101 (ampere), I2=(100×I+99.99) / 10101 (ampere), I3=(10000×I-102) / 10101 (ampere).

[0040] When I=10.2mA, we get: V1=200mV, V2=100mV, V3=0V, I1=200uA, I2=10mA, I3=0A; When I=20mA, we get: V1=200.97mV, V2=100.97mV, V3=0.9702mV, I1=200.97uA, I2=10.097mA, I3=9.702mA; When I=100mA, we get: V1=208.89mV, V2=108.89mV, V3=8.89mV, I1=208.89uA, I2=10.889mA, I3=88.9mA; When I=1A, we get: V1=297.99mV, V2=197.99mV, V3=97.99mV, I1=297.99uA, I2=19.799mA, I3=979.9mA.

[0041] 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 are connected in parallel, and the other end is independent, the voltage across the current sampling resistor is related to the current passing therethrough.

[0042] The above calculation results are summarized in the table, as shown in Fig. 9 and Fig.10 shown.

[0043] Through the demonstration of the above practical design case, some characteristics of the multi-level parallel current measurement solution of the present invention can be further seen: (1) When the measured current I increases from 1uA to 1A, V1 and I1 rise very quickly in the initial stage, then slow down after the second-level measurement branch 2 is started, and even slower after the third-level measurement branch 3 is started. This shows that when the larger-scale measurement branch starts parallel shunting, the newly added current mainly flows to the newly started branch.

[0044] (2) The three current measurement branches are responsible for current diversion and measurement in different ranges, and the changes are small when approaching the upper limit of their own range.

[0045] (3) When the starting threshold voltage is reached, the second-stage current measurement branch 2 and the third-stage current measurement branch 3 both start from 0 current and enter the shunt state in parallel, which has no effect on the current state before parallel connection. This is also an advantage of the multi-range current measurement circuit of the present invention. When the parallel gear is used to expand the range, it starts from the 0 current state, so there is no circuit interference problem caused by current mutation.

[0046] In the above practical design case, the control function of the first-stage current measurement branch 1 for the subsequent current shunting is a linear equation: Vn=V1-Bn=Rn×In, V1≥Bn. Other linear equations or nonlinear equations can also be used as control functions to obtain different shunting ratio effects.

[0047] The above actual design case only uses a three-stage parallel solution as a demonstration. It can be 2, 3, 4, 5... and other different stages, and can be a range of different current sizes.

[0048] The above practical design case uses the detection of DC current as a demonstration to explain the working principle of the circuit. The current to be measured is also applicable to the measurement of AC current.

[0049] The above practical design case demonstrates that the current is measured from the TP point where the current I to be measured is connected to the ground terminal. The current can also be measured from other circuit connection points after changing the circuit form.

[0050] Embodiment 2:

[0051] The current sampling resistors R1, R2...Rn of each current measurement branch are connected in series and then connected to the TP point. The series structure allows the current sampling resistor with a large resistance value in the previous stage to share the current sampling resistor with a smaller resistance value in the next stage. The current sampling voltage of the next stage is superimposed on the current sampling voltage of the previous stage, so that the current measurement branch of the previous stage can sense the changes of the current measurement branch of the next stage in advance.

[0052] like Figure 8 Another connection circuit diagram of the preferred embodiment of the present invention, the current sampling resistors R1, R2...Rn of each level are connected in series and then connected to the TP point. The TP point is first connected to one end of the current sampling resistor Rn of the nth current measurement branch n, and 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 current measurement branch 2; the other end of the current sampling resistor R1 is connected to the current amplifier IF1 of the first current measurement branch 1.

[0053] Figure 8 The circuit diagram of the preferred embodiment shown still complies with the basic working principle of the above-mentioned multi-level parallel current measurement. The first-level current measurement branch 1 is continuously in the startup state and is responsible for the measurement of the minimum current level. The measurement voltage V1 of the first-level current measurement branch 1 is also used as a control parameter to control the shunting work of all subsequent current measurement branches. The subsequent current measurement branches are all provided with their own startup threshold voltages Bn. When V1 exceeds a certain level of startup threshold voltage Bn, the current amplifier IFn of this level immediately starts parallel shunting. When V1 is lower than the threshold voltage Bn, the current amplifier IFn of this level immediately shuts down and exits parallel shunting. The resistance values ​​of the sampling resistors R1, R2...Rn of each level change from large to small, R1>R2...>Rn, and the startup threshold voltage values ​​B2, B3...Bn of each level change from small to large, B2 <B3...<Bn。

[0054] This implementation can simplify circuit connection and current calculation, and the design case demonstration will not be repeated here.

[0055] The invention discloses a multi-range current measurement circuit, which expands the range by using a multi-speed parallel current measurement technology, does not use a switch to switch the gears, and does not use a sampling resistor in a circuit from a current to be measured to a ground level, thereby solving the switch interference problem and the sampling resistor voltage drop problem in the current measurement technology.

[0056] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A multi-range current measurement circuit, characterized in that: The invention comprises a multi-stage current measurement branch, wherein the multi-stage current measurement branches work in parallel, the first stage current measurement branch is connected to a TP point, the current I to be measured flows through the TP point and flows from the TP point to the multi-stage current measurement branches, the current I to be measured is decomposed into parallel currents I1~In of the multi-stage current measurement branches for separate measurement, n represents the serial number corresponding to each stage current measurement branch, the first stage current measurement branch is continuously in a startup state and undertakes the measurement of the minimum current gear, the measurement voltage of the first stage current measurement branch is used as a control signal to control the start or shut down of the shunting work of all the subsequent stage current measurement branches, the parallel connection of each stage current measurement branch is smoothly connected from a zero current state from small to large, and the parallel exit of each stage current measurement branch is smoothly exited from a large to small to a zero current state.

2. The multi-range current measurement circuit according to claim 1, characterized in that: 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, the IN- terminal of the operational amplifier U1 is connected to the TP point 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.

3. The multi-range current measurement circuit according to claim 2, characterized in that: The current measurement branch of the rear stage includes an operational amplifier Un, a current sampling resistor Rn, a voltage measurement module Vn, and a current amplifier IFn. The current measurement branches of the rear stage are all set with their own starting threshold voltages Bn, n≥2. The IN+ end of the operational amplifier Un is connected to the voltage signal V1 of the first-stage current measurement branch, the IN- end of the operational amplifier Un is connected to the starting threshold voltage Bn, the output end of the operational amplifier Un is connected to the current amplifier IFn, the voltage measurement module Vn is connected to both ends of the current sampling resistor Rn and obtains the voltage of the current measurement branch of this stage, 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.

4. The multi-range current measurement circuit according to claim 3, characterized in that: When the voltage signal V1 of the first-stage current measurement branch exceeds the starting threshold voltage Bn, the current amplifier IFn of this stage immediately starts parallel shunting; when the voltage signal V1 of the first-stage current measurement branch is lower than the starting threshold voltage Bn, the current amplifier IFn of this stage immediately shuts down and exits parallel shunting.

5. The multi-range current measurement circuit according to claim 3, characterized in that: The starting threshold voltage of each level of the current measurement branch increases from small to large, B2 <B3<...<Bn。 6. The multi-range current measurement circuit according to claim 3, characterized in that: The resistance values ​​of the current sampling resistors of the current measurement branches of each level decrease from large to small, R1>R2>...>Rn.

7. The multi-range current measurement circuit according to claim 3, characterized in that: If the maximum current output value of the operational amplifier in a current measurement branch of a certain level is greater than or equal to the current measurement value of the gear position of that level, 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 end of the operational amplifier of that current measurement branch is connected to the current sampling resistor.

8. The multi-range current measurement circuit according to claim 3, characterized in that: The current sampling resistors R1, R2, ...Rn of the current measurement branches at each level are connected in parallel to the TP point.

9. The multi-range current measurement circuit according to claim 3, characterized in that: The current sampling resistors R1, R2, ..., Rn of the current measurement branches at each level are sequentially connected in series end to end and then connected to the TP point.

10. The multi-range current measurement circuit according to claim 1, characterized in that: When the current I to be measured changes from small to large, the current measurement branch of the subsequent stage is started from small to large in the order of increasing n values ​​to join the parallel shunt; when the current I to be measured changes from large to small, the current measurement branch of the subsequent stage is closed from large to small in the order of increasing n values ​​to exit the parallel shunt.

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