CN117783636A - Current detection method and circuit based on constant current source circuit - Google Patents

Abstract

The invention provides a current detection method and a circuit based on a constant current source circuit, wherein the method comprises the following steps: a first resistor is connected in series at the current inflow direction of a load resistor of the constant current source circuit, and the positive input end and the negative input end of the instrument amplifier are respectively connected into two ends of the first resistor for detection; the voltage at two ends of the first resistor is amplified through the instrument amplifier, and the output end of the instrument amplifier is connected with the outside, so that the purpose of detecting the current flowing through the load resistor is achieved. The invention directly amplifies the voltage at two ends of the first resistor through the instrument amplifier, and utilizes the output end of the instrument amplifier to be connected with the outside so as to realize the purpose of externally detecting the current flowing through the load resistor, and the method is simple and convenient.

Description

Current detection method and circuit based on constant current source circuit

Technical Field

The invention relates to the technical field of electronic devices, in particular to a current detection method and a circuit based on a constant current source circuit.

Background

With the rapid development of electronic devices, various fields are related to the application of constant current source circuits. The conventional constant current source circuit generally comprises a power supply end, a three-terminal adjustable voltage reference chip, an operational amplifier, a resistor, a grounding resistor, a load resistor and a power supply ground end, and constant current is generated by utilizing the voltage on the grounding resistor as negative feedback; or the battery is used for providing power, and a constant current source is generated by a circuit consisting of an operational amplifier, a plurality of resistors and a plurality of MOS tubes.

However, the current detection methods of these constant current source circuits are all measured by using a universal meter or an oscilloscope, and although some simple circuits can be used for current detection, the detection result is often rough, and especially for complex constant current source circuits, the detection of the constant current source current cannot be performed externally. In addition, the load resistor of the detection method has no protective measure, when the circuit fails abnormally, larger impact current is caused, the load resistor is lost, the later measurement error is larger and larger, and when the later measurement error is serious, the constant current source circuit is directly paralyzed, so that the normal work is inconvenient.

Disclosure of Invention

The invention provides a current detection method and a current detection circuit based on a constant current source circuit, which are used for improving the current detection defect of the conventional constant current source circuit.

In one aspect, the present invention provides a current detection method based on a constant current source circuit, the method comprising:

a first resistor is connected in series at the current inflow direction of a load resistor of the constant current source circuit, and the positive input end and the negative input end of the instrument amplifier are respectively connected into two ends of the first resistor for detection;

the voltage at two ends of the first resistor is amplified through the instrument amplifier, and the output end of the instrument amplifier is connected with the outside, so that the purpose of detecting the current flowing through the load resistor is achieved.

Further, the method further comprises:

the output end of the operational amplifier F1 of the constant current source circuit is connected with a second resistor in series;

and an operational amplifier F2, a third resistor and an MOS tube are sequentially connected in series between the output end of the instrumentation amplifier and the second resistor.

Further, the positive input end of the operational amplifier F2 is connected with the output end of the instrument amplifier; connecting the negative input end of the operational amplifier F2 to one end of a fourth resistor connected with a fifth resistor, wherein the other end of the fourth resistor is connected with a power supply end, and the other end of the fifth resistor is connected with a power supply ground end; and the output end of the operational amplifier F2 is connected with the third resistor.

Further, the MOS tube is a first NMOS tube and comprises a D pole, an S pole and a G pole; the D pole is connected with the output end of the operational amplifier F1 through the second resistor; the S pole is connected with the power supply ground terminal; and the G pole is connected with the output end of the operational amplifier F2 through the third resistor.

Further, an interface chip is connected to the power end of the constant current source circuit, and the charge pump of the interface chip is used for supplying power to the constant current source circuit;

the charge pump has a boosting function and a step-down function, and the driving capability of the charge pump is the same as that of the constant current source circuit.

Further, the power supply positive terminals of the operational amplifier F1, the operational amplifier F2 and the instrument amplifier are all connected to the power supply positive terminal of the interface chip; the power negative terminals of the operational amplifier F1 and the operational amplifier F2 are connected to the power ground of the interface chip, and the power negative terminal of the instrumentation amplifier is connected to the power negative terminal of the interface chip.

Further, the method comprises the steps of,

the constant current source circuit comprises a three-terminal adjustable voltage reference chip, an operational amplifier F1, a power supply terminal, a seventh resistor, a second NMOS tube, a load resistor and a power supply ground terminal which are sequentially connected in series; the three-terminal adjustable voltage reference chip is connected with the power supply terminal and the operational amplifier F1 at the same time; the second NMOS tube comprises a D pole, an S pole and a G pole; the second NMOS tube is connected with the seventh resistor through the D electrode, is connected with the load resistor through the S electrode, and is connected with the output end of the operational amplifier through the second resistor;

the interface chip comprises an RS232 interface chip.

On the other hand, the invention also provides a current detection circuit based on the constant current source circuit, which is characterized in that the current detection circuit comprises: a first resistor and an instrumentation amplifier;

the first resistor is connected in series with the current inflow direction of the load resistor of the constant current source circuit, and the positive input end and the negative input end of the instrument amplifier are respectively connected into two ends of the first resistor for detection;

the voltage at two ends of the first resistor is amplified through the instrument amplifier, and the output end of the instrument amplifier is connected with the outside, so that the purpose of detecting the current flowing through the load resistor is achieved.

Further, the current detection circuit further includes:

the second resistor is connected in series with the output end of the operational amplifier F1 of the constant current source circuit;

and the operational amplifier F2, the third resistor and the MOS tube are sequentially connected in series between the output end of the instrument amplifier and the second resistor.

Further, the current detection circuit further includes:

connecting the power supply positive ends of the operational amplifier F1, the operational amplifier F2 and the instrument amplifier to the power supply positive end of the interface chip; the power negative terminals of the operational amplifier F1 and the operational amplifier F2 are connected to the power ground of the interface chip, and the power negative terminal of the instrumentation amplifier is connected to the power negative terminal of the interface chip.

In general, by means of the technical solution conceived by the present invention, the following beneficial effects can be obtained compared with the prior art:

(1) The invention provides a current detection method and a circuit based on a constant current source circuit, which directly amplify the voltage at two ends of a first resistor through an instrument amplifier, and realize the purpose of externally detecting the current flowing through a load resistor by utilizing the output end of the instrument amplifier to be connected with the outside.

(2) The invention provides a current detection method and a circuit based on a constant current source circuit, which are characterized in that an operational amplifier F2, a third resistor and an MOS tube are sequentially connected in series between the output end of an instrument amplifier and a second resistor, so that a load resistor is protected, larger impact current caused by abnormal failure of the circuit is prevented, the circuit paralysis of the constant current source is avoided to a certain extent, and the normal operation of the circuit is ensured.

(3) The invention provides a current detection method and a circuit based on a constant current source circuit, wherein the power supply positive ends of an operational amplifier F1, an operational amplifier F2 and an instrument amplifier are all connected to the power supply positive end of an interface chip; the power negative terminals of the operational amplifier F1 and the operational amplifier F2 are connected to the power ground terminal of the interface chip, and the power negative terminal of the instrument amplifier is connected to the power negative terminal of the interface chip, so that the problem of insufficient driving capability caused by the fact that the operational amplifier is driven by the interface chip is solved. The detection method is simple, the thought is ingenious, and the practical range is wide.

Drawings

In order to more clearly illustrate the invention or the technical solutions of the prior art, the following description will briefly explain the drawings used in the embodiments or the description of the prior art, and it is obvious that the drawings in the following description are some embodiments of the invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.

FIG. 1 is a schematic diagram of a part of a current detection method and circuit based on a constant current source circuit;

FIG. 2 is a schematic diagram of a part of a current detection method and circuit embodiment based on a constant current source circuit;

fig. 3 is a schematic circuit diagram of a current detection method and a circuit embodiment based on a constant current source circuit.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and examples of the present invention, and it is apparent that the described examples are some, but not all, examples of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

It should be noted that in the description of embodiments of the present invention, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a method, circuit, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such method, circuit, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a method, circuit or apparatus comprising such elements.

In one aspect, the invention provides a current detection method based on a constant current source circuit, which comprises the following steps: the method comprises the steps that a first resistor is connected in series at the current inflow direction of a load resistor of a constant current source circuit, and a positive input end and a negative input end of an instrument amplifier are respectively connected to two ends of the first resistor for detection; the voltage at two ends of the first resistor is amplified through the instrument amplifier, and the output end of the instrument amplifier is connected with the outside, so that the purpose of detecting the current flowing through the load resistor is achieved.

The first resistor is used for measuring the current of the constant current source circuit.

The instrumentation amplifier is a precision differential voltage amplifier derived from, but superior to, an operational amplifier. The instrument amplifier integrates key elements in the amplifier, and the unique structure of the instrument amplifier enables the instrument amplifier to have the characteristics of high common mode rejection ratio, high input impedance, low noise, low linear error, low offset drift gain, flexible setting, convenient use and the like, so that the instrument amplifier is favored in the aspects of data acquisition, sensor signal amplification, high-speed signal regulation and the like.

As an embodiment of the invention, the instrumentation amplifier F' comprises a plurality of ports RG port 1, VIN-port 2, VIN + port 3, V-port 4, ref port 5, vo port 6, V + port 7 and RG port 8, respectively.

As an embodiment of the invention, RG port 1 and connection RG port 8 are connected via a resistor R' for configuring the amplification of the instrumentation amplifier, as shown in fig. 1.

VIN-port 2 and vin+ port 3 are the positive input terminal and the negative input terminal of the instrumentation amplifier F', and are respectively connected to two ends of the first resistor R1. The V-port 4 is connected with the negative end of the power supply, the Ref port 5 is connected with the ground end of the power supply, the Vo port 6 is connected with the outside, and the V+ port 7 is connected with the positive end of the power supply.

The constant current source circuit is a circuit capable of supplying a constant current. Is not changed by the change of load resistance, output voltage, ambient temperature and the like; and the internal resistance is infinite so that the current thereof can flow out entirely to the outside.

In order to avoid the condition that the circuit is abnormally invalid, the constant current source current is overlarge, and a circuit comprising a resistor, an MOS tube and an operational amplifier is used for protecting the load resistor RL.

As a preferred embodiment of the present invention, as shown in fig. 2, a second resistor R2 is connected in series to the output terminal of the operational amplifier F1 of the constant current source circuit; and an operational amplifier F2, a third resistor R3 and a MOS tube Q1 are sequentially connected in series between the output end of the instrument amplifier F' and the second resistor R2.

Wherein the second resistor R2 is used for limiting the current of the output end of the operational amplifier F1 in the constant current source circuit, thereby protecting the output end of the operational amplifier F1. The third resistor R3 is used to limit the current at the output of the operational amplifier F2, thereby protecting the output of the operational amplifier F2.

Of course, as another embodiment of the present invention, the operational amplifier F2, the third resistor R3 and the MOS transistor Q1 may be sequentially connected in series between the output terminal of the instrumentation amplifier F' and the output terminal of the operational amplifier F1 of the constant current source circuit.

As an embodiment of the present invention, a fourth resistor R4 and a fifth resistor R5 are further included.

Specifically, the positive input end of the operational amplifier F2 is connected with the output end VOUT of the instrument amplifier F'; the negative input end of the operational amplifier F2 is connected to one end of the fourth resistor R4 and one end of the fifth resistor R5, the other end of the fourth resistor R4 is connected with the power supply end VCC IN, and the other end of the fifth resistor R5 is connected with the power supply ground end AGND; the output of the operational amplifier F2 is connected to a third resistor R3.

The fourth resistor R4 and the fifth resistor R5 are used for dividing the voltage vcc_in and providing the divided voltage to the negative feedback end of the operational amplifier F2.

The MOS tube includes PMOS tube and NMOS tube.

As one embodiment of the invention, the MOS tube is a first NMOS tube Q1, comprising a D pole, an S pole and a G pole; the D pole is connected with the output end of the operational amplifier F1 through a second resistor R2; the S pole is connected with a power supply ground end AGND; the G pole is connected with the output end of the operational amplifier F2 through a third resistor R3.

As one embodiment of the invention, an interface chip is connected to the power end of the constant current source circuit, and the charge pump of the interface chip is used for supplying power to the constant current source circuit; the charge pump has a boosting function and a step-down function, and the driving capability of the charge pump is the same as that of the constant current source circuit.

Because the power supply driving capability generated by some interface chips is limited, the generated positive power supply is used for driving the constant current source circuit, and if the operational amplifier and the instrument amplifier are driven, a part of the driving capability is correspondingly divided into the operational amplifier and the instrument amplifier, so that the driving capability for the constant current source circuit is weaker.

Therefore, as one embodiment of the present invention, the power supply positive terminals of the operational amplifier F1, the operational amplifier F2, and the instrumentation amplifier are all connected to the power supply positive terminal of the interface chip; the negative power terminals of the operational amplifier F1 and the operational amplifier F2 are connected to the power ground terminal of the interface chip, and the negative power terminal of the instrument amplifier is connected to the negative power terminal of the interface chip.

The negative end of the generated power supply has no consumption driving capability, and the operational amplifier and the instrument amplifier output positive voltages, so that the problem of insufficient driving capability of the negative end of the operational amplifier and the instrument amplifier is solved.

The driving capability refers to the capability of outputting a current, that is, the value of the maximum output current. The driving capability of the charge pump is the same as that of the constant current source circuit, namely, the driving capability of the constant current source circuit is strong, and the driving capability of the charge pump of the matched interface chip needs to be strong in the same grade; the driving capability of the constant current source circuit is weak, and the driving capability of the charge pump of the matched interface chip is also weak at the same level.

As an embodiment of the present invention, as shown in fig. 3, the constant current source circuit includes a three-terminal adjustable voltage reference chip, an operational amplifier F1, and a power supply terminal, a seventh resistor, a second NMOS transistor Q2, a load resistor RL, and a power supply ground terminal, which are sequentially connected in series. The three-terminal adjustable voltage reference chip is connected with the power supply terminal and the operational amplifier F1 at the same time; the second NMOS tube Q2 comprises a D pole, an S pole and a G pole; the second NMOS tube Q2 is connected with a seventh resistor through a D electrode, is connected with a load resistor through an S electrode, and is connected with the output end of the operational amplifier through the second resistor; controlling the magnitude of current flowing through a load resistor by controlling the magnitude of voltage between an S pole and a G pole; thus realizing constant control of current on the load resistor by using the NMOS tube.

Constant control of current on a load resistor is realized by utilizing the volt-ampere characteristic of an NMOS tube: when the voltage between the S pole and the G pole of the NMOS tube is increased, the current flowing through the load resistor is large, and when the voltage between the S pole and the G pole of the NMOS tube is reduced, the current flowing through the load resistor is small until the current is zero. The voltage between the S-pole and the G-pole is controlled by introducing negative feedback and the output of the operational amplifier.

Because the constant current source circuit is a weak-drive constant current source, a weak power supply is needed, that is, the charge pump of the selected interface chip needs to have a boosting function and a step-down function, and the driving capability of the charge pump is the same as that of the constant current source circuit.

As one embodiment of the invention, the interface chip is an RS232 interface chip, and the current limiting protection of the constant current source circuit can be realized by directly connecting the RS232 interface chip to the power end of the constant current source circuit. This is because the charge pump of the RS232 interface chip is weak, and not only has a voltage boosting function and a voltage reducing function, but also the driving capability of the charge pump is the same as that of the constant current source circuit.

As one embodiment of the present invention, the constant current source circuit further includes an eighth resistor R8; the three-terminal adjustable voltage reference chip comprises a K pole, an R pole and an A pole; the K pole and the R pole are both connected to a power supply terminal, the A pole is connected to one end of an eighth resistor R8, and the other end of the eighth resistor R8 is connected to a power supply ground terminal.

As one embodiment of the present invention, the positive terminal of the operational amplifier F1 is connected between the seventh resistor and the D pole as the positive feedback of the operational amplifier F1; the negative terminal of the operational amplifier F1 is connected between the A pole and the eighth resistor as negative feedback of the operational amplifier F1.

In order to further filter noise on the reference voltage between the K pole and the a pole, as an embodiment of the present invention, the constant current source circuit further includes a first capacitor connected in parallel between the K pole and the a pole.

In order to further filter noise caused by fluctuation of the power supply end at two ends of the seventh resistor and noise caused by unstable closed loop of the operational amplifier, as an embodiment of the invention, the constant current source circuit further comprises a second capacitor connected in parallel between two ends of the seventh resistor.

As an embodiment of the invention, the first capacitance is the same as the second capacitance.

Since a parasitic diode exists in the NMOS transistor Q2, in order to prevent current flowing backward across the load resistor, as a preferred embodiment of the present invention, a diode D1 is connected in series between the NMOS transistor Q2 and the first resistor R1; the positive electrode is connected with the S electrode, and the negative electrode is connected with the first resistor R1.

In addition, in order to ensure the normal operation of the constant current source circuit, the voltage of the power supply end is larger than the reference voltage between the K pole and the A pole; and the current limited by the second resistor can ensure that the three-terminal adjustable voltage reference chip normally works in a voltage stabilizing range, and the power supply terminal can ensure the effective work of the cloud amplifier.

The reference voltage is stabilized at a constant value by controlling the current flowing through the three-terminal adjustable voltage reference chip. The constant current flowing through the load resistor RL can be obtained by the following calculation method: the reference voltage between the K pole and the A pole is divided by the seventh resistance.

As another embodiment of the present invention, the constant current source circuit is a constant current source circuit common in the prior art, and includes a power supply terminal, a three-terminal adjustable voltage reference chip, an operational amplifier, a resistor, a ground resistor, a load resistor and a power supply ground terminal, and generates a constant current by using a voltage on the ground resistor as negative feedback. Or the constant current source circuit provides power through a battery, and the constant current source is generated by utilizing a circuit comprising an operational amplifier, a plurality of resistors and a plurality of MOS tubes.

The current detection circuit of the present invention is applicable to any constant current source circuit, and is not limited to the embodiments of the present invention.

As a specific embodiment of the invention, an RS232 interface chip is connected to the power supply terminal +vcc of the constant current source circuit, and the constant current source circuit includes the power supply terminals +vcc, R7, Q2, D1, RL and the power supply ground terminal AGND connected in series in sequence; the three-terminal adjustable voltage reference chip U, F, R8, the first capacitor C1 and the second capacitor C2 are also included. The power supply end +VCC is connected to the RS232 interface chip for supplying power.

Since R7 is 300Ω, Q2 is 2N7002 model, D1 is IN5819 model, power ground terminal AGND, U is CD431 model, F1 is LM2904XS8G/TR model, R8 is 1.2kΩ, and both C1 and C2 are 0.1 μF. The driving capability of the constant current source circuit is 20mA. The DC/DC charge pump of the RS232 interface chip can be directly used as a power supply +VCC, -VCC, the voltage is approximately +5V and-5V by the boosting and price reduction of the charge pump of the RS232 interface chip, and the current protection function of the constant current source is realized by means of the limited driving capability of the charge pump of 20mA.

In order to detect the current of the constant current source, R1 (5.1Ω) is connected in series between D1 and RL, one end of the R1, which is connected with D1, is connected with the positive input end of F ' (COS 620 ARZ), one end of the R1, which is connected with RL, is connected with the negative input end of F ', and the voltage at two ends of the R1 is amplified by 25 times through F ' and then output through VOUT, so that the current of the constant current source can be detected externally.

IN order to realize the overlarge limiting protection of the constant current source current under the condition of abnormal failure of a circuit, VOUT output by F' is simultaneously introduced to the positive input end of F2 (LM 2904XS 8G/TR), the negative input end of F2 is connected between one end connected with R4 (10.2 kΩ) and R5 (3.48 kΩ), the other end of R4 is connected with VCC_IN (5V), the other end of R5 is connected with AGND, the output end of F2 is connected with the G pole of Q1 (2N 7002) through R3 (1 kΩ), the S pole of Q1 is connected with AGND, and the D pole of Q1 is connected between the G poles of R2 and Q2.

The K pole and R pole of U are both connected to power +VCC, the A pole is connected to one end of R8, and the other end of R8 is connected to power ground AGND; the current flowing through the U in the constant current source circuit is about 2mA, so that the voltage between the A pole and the K pole of the U can be stabilized about 2.5V.

The G pole of Q2 is connected with R2, the positive input end of F1 is connected between R7 and D pole, and positive feedback of F1 is introduced; the negative terminal of F1 is connected between the A pole and R8, introducing negative feedback of F1. The output of F1 is controlled by the introduction of negative feedback, thereby controlling the voltage between the G and S poles of Q2.

The +5VA of the power supply end is larger than 2.5V of the reference voltage between the K pole and the A pole, and the current 2mA limited by R8 can ensure that the work of U is stabilized at 2.5V, and the +5VA of the power supply end can ensure the effective work of F1.

Therefore, the constant current I flowing through the load resistor RL can be obtained as:

thereby realizing constant control of the current on the load resistor by using the NMOS tube.

It should be noted that when the current flowing through R1 exceeds the limit, the voltage across R1 exceeds the limit; further, the output end VOUT of the instrumentation amplifier F' is greater than the voltage between R4 and R5, and then the output is high voltage; opening the NMOS transistor Q1 to set the G pole of the NMOS transistor Q2 to be low level, and closing the NMOS transistor Q2 to limit the current output on R1; after normal operation, the NMOS transistor Q2 is turned on again to resume current output on R1.

That is, when measuring current, Q1 in the detection circuit is always in an off state, and Q2 in the constant current source circuit is always in an on state; when the current is excessive, Q1 is firstly turned on and then Q2 is turned off, so that the current is reduced; when the current is recovered to be normal, Q2 is turned on again, and Q1 in the protection circuit is turned off.

On the other hand, the invention also provides a current detection circuit based on the constant current source circuit, which is characterized in that the current detection circuit comprises: a first resistor and an instrumentation amplifier; the first resistor is connected in series with the current inflow direction of the load resistor of the constant current source circuit, and the positive input end and the negative input end of the instrument amplifier are respectively connected with the two ends of the first resistor for detection; the voltage at two ends of the first resistor is amplified through the instrument amplifier, and the output end of the instrument amplifier is connected with the outside, so that the purpose of detecting the current flowing through the load resistor is achieved.

The current detection circuit is consistent with the technical features of the method, and will not be described in detail herein.

It should be noted that, for simplicity of description, the foregoing circuit embodiments are all described as a series of combinations of actions, but it should be understood by those skilled in the art that the present application is not limited by the order of actions described, as some steps may be performed in other order or simultaneously in accordance with the present application. Further, those skilled in the art will also appreciate that the embodiments described in the specification are all preferred embodiments, and that the acts and modules referred to are not necessarily required in the present application.

In the foregoing embodiments, the descriptions of the embodiments are emphasized, and for parts of one embodiment that are not described in detail, reference may be made to related descriptions of other embodiments.

In the several embodiments provided in this application, it should be understood that the disclosed circuits may be implemented in other ways. For example, the circuit embodiments described above are merely illustrative, such as the division of the units, merely a logical functional division, and there may be additional divisions in actual implementation, such as multiple units or components may be combined or integrated into another system, or some features may be omitted, or not performed. Alternatively, the coupling or direct coupling or communication connection shown or discussed with each other may be through some service interface, indirect coupling or communication connection of circuits, electrical or other form.

The units described as separate units may or may not be physically separate, and units shown as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

In addition, each functional unit in each embodiment of the present application may be integrated in one processing unit, or each unit may exist alone physically, or two or more units may be integrated in one unit. The integrated units may be implemented in hardware or in software functional units.

The integrated units, if implemented in the form of software functional units and sold or used as stand-alone products, may be stored in a computer readable memory. Based on such understanding, the technical solution of the present application may be embodied in essence or a part contributing to the prior art or all or part of the technical solution in the form of a software product stored in a memory, including several instructions for causing a computer device (which may be a personal computer, a server or a network device, etc.) to perform all or part of the steps of the method described in the embodiments of the present application. And the aforementioned memory includes: a U-disk, a Read-Only Memory (ROM), a random access Memory (Random Access Memory, RAM), a removable hard disk, a magnetic disk, or an optical disk, or other various media capable of storing program codes.

Those skilled in the art will appreciate that all or part of the various circuits of the above described embodiments may be implemented by program code to instruct related hardware, and that the program may be stored in a computer readable memory, which may include: flash disk, read-Only Memory (ROM), random-access Memory (Random Access Memory, RAM), magnetic or optical disk, and the like.

The foregoing is merely exemplary embodiments of the present disclosure and is not intended to limit the scope of the present disclosure. That is, equivalent changes and modifications are contemplated by the teachings of this disclosure, which fall within the scope of the present disclosure. Embodiments of the present disclosure will be readily apparent to those skilled in the art from consideration of the specification and practice of the disclosure herein. This application is intended to cover any adaptations, uses, or adaptations of the disclosure following, in general, the principles of the disclosure and including such departures from the present disclosure as come within known or customary practice within the art to which the disclosure pertains. It is intended that the specification and examples be considered as exemplary only, with a scope and spirit of the disclosure being indicated by the claims.

The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

It will be readily appreciated by those skilled in the art that the foregoing description is merely a preferred embodiment of the invention and is not intended to limit the invention, but any modifications, equivalents, improvements or alternatives falling within the spirit and principles of the invention are intended to be included within the scope of the invention.

Claims (10)

1. A current detection method based on a constant current source circuit, the method comprising:

a first resistor is connected in series at the current inflow direction of a load resistor of the constant current source circuit, and the positive input end and the negative input end of the instrument amplifier are respectively connected into two ends of the first resistor for detection;

the voltage at two ends of the first resistor is amplified through the instrument amplifier, and the output end of the instrument amplifier is connected with the outside, so that the purpose of detecting the current flowing through the load resistor is achieved.

2. The current detection method based on a constant current source circuit according to claim 1, further comprising:

the output end of the operational amplifier F1 of the constant current source circuit is connected with a second resistor in series;

and an operational amplifier F2, a third resistor and an MOS tube are sequentially connected in series between the output end of the instrumentation amplifier and the second resistor.

3. The current detection method based on a constant current source circuit according to claim 2, wherein a positive input terminal of the operational amplifier F2 is connected to an output terminal of the instrumentation amplifier; connecting the negative input end of the operational amplifier F2 to one end of a fourth resistor connected with a fifth resistor, wherein the other end of the fourth resistor is connected with a power supply end, and the other end of the fifth resistor is connected with a power supply ground end; and the output end of the operational amplifier F2 is connected with the third resistor.

4. The current detection method based on the constant current source circuit as claimed in claim 2, wherein the MOS transistor is a first NMOS transistor comprising a D pole, an S pole and a G pole; the D pole is connected with the output end of the operational amplifier F1 through the second resistor; the S pole is connected with the power supply ground terminal; and the G pole is connected with the output end of the operational amplifier F2 through the third resistor.

5. The current detection method based on the constant current source circuit according to claim 2, wherein an interface chip is connected to a power end of the constant current source circuit, and a charge pump of the interface chip is used for supplying power to the constant current source circuit;

the charge pump has a boosting function and a step-down function, and the driving capability of the charge pump is the same as that of the constant current source circuit.

6. The current detection method based on a constant current source circuit according to claim 5, wherein power supply positive terminals of said operational amplifier F1, said operational amplifier F2 and said instrumentation amplifier are all connected to a power supply positive terminal of said interface chip; the power negative terminals of the operational amplifier F1 and the operational amplifier F2 are connected to the power ground of the interface chip, and the power negative terminal of the instrumentation amplifier is connected to the power negative terminal of the interface chip.

7. The current limiting protection method according to claim 6, wherein the constant current source circuit is used for the current limiting protection,

the constant current source circuit comprises a three-terminal adjustable voltage reference chip, an operational amplifier F1, a power supply terminal, a seventh resistor, a second NMOS tube, a load resistor and a power supply ground terminal which are sequentially connected in series; the three-terminal adjustable voltage reference chip is connected with the power supply terminal and the operational amplifier F1 at the same time; the second NMOS tube comprises a D pole, an S pole and a G pole; the second NMOS tube is connected with the seventh resistor through the D electrode, is connected with the load resistor through the S electrode, and is connected with the output end of the operational amplifier through the second resistor;

the interface chip comprises an RS232 interface chip.

8. A current detection circuit based on a constant current source circuit, the current detection circuit comprising: a first resistor and an instrumentation amplifier;

the first resistor is connected in series with the current inflow direction of the load resistor of the constant current source circuit, and the positive input end and the negative input end of the instrument amplifier are respectively connected into two ends of the first resistor for detection;

the voltage at two ends of the first resistor is amplified through the instrument amplifier, and the output end of the instrument amplifier is connected with the outside, so that the purpose of detecting the current flowing through the load resistor is achieved.

9. The current detection circuit based on a constant current source circuit according to claim 8, wherein the current detection circuit further comprises:

the second resistor is connected in series with the output end of the operational amplifier F1 of the constant current source circuit;

and the operational amplifier F2, the third resistor and the MOS tube are sequentially connected in series between the output end of the instrument amplifier and the second resistor.

10. The current detection circuit based on a constant current source circuit according to claim 9, wherein the current detection circuit further comprises:

connecting the power supply positive ends of the operational amplifier F1, the operational amplifier F2 and the instrument amplifier to the power supply positive end of the interface chip; the power negative terminals of the operational amplifier F1 and the operational amplifier F2 are connected to the power ground of the interface chip, and the power negative terminal of the instrumentation amplifier is connected to the power negative terminal of the interface chip.