CN117539317A - Constant current source circuit - Google Patents
Constant current source circuit Download PDFInfo
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- CN117539317A CN117539317A CN202311814479.8A CN202311814479A CN117539317A CN 117539317 A CN117539317 A CN 117539317A CN 202311814479 A CN202311814479 A CN 202311814479A CN 117539317 A CN117539317 A CN 117539317A
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- 238000005859 coupling reaction Methods 0.000 description 3
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- 230000006978 adaptation Effects 0.000 description 2
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- 239000004065 semiconductor Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
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- 230000003071 parasitic effect Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
- G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
- G05F1/10—Regulating voltage or current
- G05F1/46—Regulating voltage or current wherein the variable actually regulated by the final control device is dc
- G05F1/56—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices
- G05F1/561—Voltage to current converters
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- Automation & Control Theory (AREA)
- Continuous-Control Power Sources That Use Transistors (AREA)
Abstract
The invention provides a constant current source circuit which comprises a three-terminal adjustable voltage reference chip, an operational amplifier, a power supply terminal, a first resistor, an 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 at the same time; the NMOS tube comprises a D pole, an S pole and a G pole; the NMOS tube is connected with the first resistor through the D pole, is connected with the load resistor through the S pole and is connected with the output end of the operational amplifier through the G pole; controlling the magnitude of current flowing through the load resistor by controlling the magnitude of voltage between the S pole and the G pole; thereby realizing constant control of the current on the load resistor by using the NMOS tube. The constant current source circuit provided by the invention not only does not generate common-mode voltage, but also improves the stability of constant current source output current and constant current source.
Description
Technical Field
The invention relates to the technical field of electronic devices, in particular to 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 consists of 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.
However, this constant current source circuit has some drawbacks: on one hand, the voltage generated by the constant current flowing through the load resistor RL is common-mode voltage, so that the extraction is inconvenient; on the other hand, the constant current source circuit has limited driving capability of the constant current source which flows through the load resistor, limited by the driving capability of the operational amplifier itself.
Disclosure of Invention
The invention provides a constant current source circuit which is used for improving the defects of the conventional constant current source circuit.
In one aspect, the invention provides a constant current source circuit, which comprises a three-terminal adjustable voltage reference chip, an operational amplifier, a power supply terminal, a first resistor, an 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 at the same time;
the NMOS tube comprises a D pole, an S pole and a G pole; the NMOS tube is connected with the first resistor through the D pole, is connected with the load resistor through the S pole and is connected with the output end of the operational amplifier through the G pole;
controlling the magnitude of current flowing through the load resistor by controlling the magnitude of voltage between the S pole and the G pole; thereby realizing constant control of the current on the load resistor by using the NMOS tube.
Further, 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 end, the A pole is connected to one end of a second resistor, and the other end of the second resistor is connected to a power supply ground end.
Further, the method comprises the steps of,
the positive end of the operational amplifier is connected between the first resistor and the D pole and used as positive feedback of the operational amplifier;
the negative terminal of the operational amplifier is connected between the A pole and the second resistor as negative feedback of the operational amplifier.
Further, the constant current source circuit further comprises a first capacitor; the first capacitor is connected in parallel between the K pole and the A pole.
Further, the constant current source circuit further comprises a second capacitor; the second capacitor is connected in parallel with two ends of the first resistor.
Further, the constant current source circuit further comprises a diode; the diode is connected in series between the NMOS tube and the load resistor.
Further, the positive electrode of the diode is connected with the S electrode, and the negative electrode of the diode is connected with the load resistor.
Further, the voltage of the power supply terminal is greater than the reference voltage between the K pole and the A pole.
Further, the reference voltage is stabilized at a constant value by controlling the current flowing through the three-terminal adjustable voltage reference chip.
Further, the method comprises the steps of,
the constant current I flowing through the load resistor is calculated by the following steps:
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 constant current source circuit, which is characterized in that an NMOS (N-channel metal oxide semiconductor) tube is added in the circuit to adapt to a load resistor, and the load resistor is used as a grounding resistor of a grounding end, so that common-mode voltage is not generated, and meanwhile, the output current of the constant current source is improved.
(2) The invention provides a constant current source circuit, which is characterized in that the position of a three-terminal adjustable voltage reference chip is arranged, a K pole and an R pole are connected to a power supply end, an A pole is connected to one end of a second resistor, and the other end of the second resistor is connected to a power supply ground end, so that the self driving capability of an operational amplifier is not limited, and the driving capability of the constant current source circuit for generating a constant current source flowing through a load resistor is not limited.
(3) The invention provides a constant current source circuit, which filters noise on a reference voltage by connecting a first capacitor in parallel between a K pole and an A pole of a three-terminal adjustable voltage reference chip; the second capacitor is connected in parallel with the two ends of the first resistor, so that noise caused by fluctuation of the power supply end at the two ends of the first resistor and noise caused by unstable closed loop of the operational amplifier are filtered; the whole circuit is enabled to be more stable, and the output constant current source is more stable.
(4) The invention provides a constant current source circuit which is universal in used components, low in cost, simple in composition and wide in practical range.
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 constant current source circuit common in the prior art provided by the present invention;
fig. 2 is a schematic circuit diagram of a constant current source circuit provided by the invention.
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 circuit including a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such circuit. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a circuit comprising such elements.
As shown in fig. 1, a constant current source circuit commonly used in the prior art is composed of a power supply end VCC, a three-terminal adjustable voltage reference chip U, an operational amplifier F, a resistor R1, a grounding resistor R0, a load resistor RL and a power supply ground end AGND; the power supply end VCC, the resistor R1, the three-terminal adjustable voltage reference chip U and the power supply ground end AGND are sequentially connected in series, the K pole and the R pole of the three-terminal adjustable voltage reference chip U are simultaneously connected with the resistor R1, and the A pole of the three-terminal adjustable voltage reference chip U is directly connected with the power supply ground end AGND; the output end of the operational amplifier F is connected with the power ground end AGND through a load resistor RL and a grounding resistor R0 which are sequentially connected in series, the positive end of the operational amplifier F is connected between the resistor R1 and the K pole, and the negative end is connected between the resistor R1 and the grounding resistor R0. The voltage across the ground resistor R0 is used as negative feedback to generate a constant current.
However, the voltage generated by the current flowing through the load resistor RL by the common constant current source circuit is common mode voltage, so that the extraction is inconvenient; and limited by the drive capability of the operational amplifier itself, the constant current source produced across the load resistor has limited drive capability.
In order to solve the problems, the invention provides the constant current source circuit which has no common-mode voltage, no limit on the driving capability of the operational amplifier and wider practical range on the basis of the common constant current source circuit.
The invention provides a constant current source circuit which comprises a three-terminal adjustable voltage reference chip, an operational amplifier, a power supply terminal, a first resistor, an NMOS (N-channel metal oxide semiconductor) 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 at the same time; the NMOS tube comprises a D pole, an S pole and a G pole; the NMOS tube is connected with the first resistor through a D pole, connected with the load resistor through an S pole and connected with the output end of the operational amplifier through a G pole; 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.
As one embodiment of the present invention, the constant current source circuit further includes a second resistor; 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 a second resistor, and the other end of the second resistor is connected to a power supply ground terminal.
As one embodiment of the invention, the positive end of the operational amplifier is connected between the first resistor and the D pole and is used as positive feedback of the operational amplifier; the negative terminal of the operational amplifier is connected between the A pole and the second resistor as the negative feedback of the operational amplifier.
As an embodiment of the present invention, in order to further filter noise on the reference voltage between the K pole and the a pole, the constant current source circuit of the present invention further includes a first capacitor connected in parallel between the K pole and the a pole.
As an embodiment of the present invention, in order to further filter noise caused by fluctuation of the power supply terminal at both ends of the first resistor and noise caused by unstable closed loop of the operational amplifier, the constant current source circuit of the present invention further includes a second capacitor connected in parallel between both ends of the first resistor.
Because of the parasitic diode inside the NMOS tube, in order to prevent the current flowing backward on the load resistor, as a preferred embodiment of the invention, the diode is connected in series between the NMOS tube and the load resistor; further, the positive electrode of the diode is connected with the S electrode, and the negative electrode of the diode is connected with the load resistor.
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. 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 calculation method for obtaining the constant current flowing through the load resistor is as follows: the reference voltage between the K pole and the A pole is divided by the first resistance.
As a specific embodiment of the present invention, as shown in fig. 2, the constant current source circuit includes a power supply terminal VCC, a first resistor R1, an NMOS transistor Q, a diode D1, a load resistor RL, and a power supply ground terminal AGND connected in series; the three-terminal adjustable voltage reference chip comprises a three-terminal adjustable voltage reference chip U, an operational amplifier F, a second resistor R2, a first capacitor C1 and a second capacitor C2.
The power supply end VCC is +5VA, the first resistor R1 is 300 omega, the NMOS tube Q is 2N7002 model, the diode D1 is IN5819 model, the power supply ground end AGND, the three-end adjustable voltage reference chip U is CD431 model, the operational amplifier F is LM2904XS8G/TR model, the second resistor R2 is 1.2kΩ, and the first capacitor C1 and the second capacitor C2 are both 0.1 mu F.
The K pole and the R pole of the three-terminal adjustable voltage reference chip U are both connected to a power supply +5VA, the A pole is connected to one end of a second resistor R2, and the other end of the second resistor R2 is connected to a power supply ground AGND; the current flowing through the three-terminal adjustable voltage reference chip U1 in the constant current source circuit is about 2mA, so that the voltage between the A pole and the K pole of the three-terminal adjustable voltage reference chip U1 can be stabilized about 2.5V.
The G pole of the NMOS tube Q is connected with the output 1 pin of the operational amplifier F, the positive input 3 pin of the operational amplifier F is connected between the first resistor R1 and the D pole, and positive feedback of the operational amplifier F is introduced; the negative terminal 2 pin of the operational amplifier F is connected between the A pole and the second resistor R2, and negative feedback of the operational amplifier F is introduced. The output of the operational amplifier F is controlled by the introduced negative feedback, thereby controlling the voltage between the G pole and the S pole of the NMOS tube.
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 the second resistor R2 can ensure that the work of the three-terminal adjustable voltage reference chip U is stabilized at 2.5V, and the +5VA of the power supply end can ensure the effective work of the operational amplifier F.
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.
In a word, the constant current source circuit provided by the invention does not generate common-mode voltage, and the output current of the constant current source is improved.
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. The constant current source circuit is characterized by comprising a three-terminal adjustable voltage reference chip, an operational amplifier, a power supply terminal, a first resistor, an 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 at the same time;
the NMOS tube comprises a D pole, an S pole and a G pole; the NMOS tube is connected with the first resistor through the D pole, is connected with the load resistor through the S pole and is connected with the output end of the operational amplifier through the G pole;
controlling the magnitude of current flowing through the load resistor by controlling the magnitude of voltage between the S pole and the G pole; thereby realizing constant control of the current on the load resistor by using the NMOS tube.
2. The constant current source circuit according to claim 1, wherein said 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 end, the A pole is connected to one end of a second resistor, and the other end of the second resistor is connected to a power supply ground end.
3. The constant current source circuit according to claim 2, wherein,
the positive end of the operational amplifier is connected between the first resistor and the D pole and used as positive feedback of the operational amplifier;
the negative terminal of the operational amplifier is connected between the A pole and the second resistor as negative feedback of the operational amplifier.
4. A constant current source circuit according to claim 2 or 3, wherein the constant current source circuit further comprises a first capacitor; the first capacitor is connected in parallel between the K pole and the A pole.
5. The constant current source circuit according to claim 2, 3 or 4, wherein the constant current source circuit further comprises a second capacitor; the second capacitor is connected in parallel with two ends of the first resistor.
6. The constant current source circuit according to claim 1, wherein said constant current source circuit further comprises a diode; the diode is connected in series between the NMOS tube and the load resistor.
7. The constant current source circuit according to claim 6, wherein an anode of said diode is connected to said S-pole, and a cathode of said diode is connected to said load resistor.
8. The constant current source circuit according to claim 2, wherein a voltage of said power supply terminal is greater than a reference voltage between said K pole and said a pole.
9. The constant current source circuit according to claim 8, wherein said reference voltage is stabilized at a constant value by controlling a current flowing through said three-terminal adjustable voltage reference chip.
10. The constant current source circuit according to claim 9, wherein,
the constant current I flowing through the load resistor is calculated by the following steps:
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311814479.8A CN117539317A (en) | 2023-12-26 | 2023-12-26 | Constant current source circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311814479.8A CN117539317A (en) | 2023-12-26 | 2023-12-26 | Constant current source circuit |
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| Publication Number | Publication Date |
|---|---|
| CN117539317A true CN117539317A (en) | 2024-02-09 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN202311814479.8A Pending CN117539317A (en) | 2023-12-26 | 2023-12-26 | Constant current source circuit |
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| CN (1) | CN117539317A (en) |
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- 2023-12-26 CN CN202311814479.8A patent/CN117539317A/en active Pending
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