Constant current source circuit

Abstract

The embodiment of the utility model provides a constant current source circuit. The constant current source circuit comprises a constant current circuit and a voltage stabilizing circuit, the constant current circuit comprises a constant current power supply, a first operational amplifier and a first resistor; wherein the in-phase input end of the first operational amplifier is connected with a constant-current power supply, and the output end of the first operational amplifier is connected in series with a load through a first resistor; the voltage stabilizing circuit comprises a second operational amplifier, a third operational amplifier, a second resistor, a third resistor, a fourth resistor and a fifth resistor; the non-inverting input end of the second operational amplifier is connected between the first resistor and the load, and the inverting input end and the output end of the second operational amplifier are connected with the inverting input end of the third operational amplifier through the fourth resistor; the in-phase input end of the third operational amplifier is respectively connected with the fourth resistor and the second resistor, is connected between the output end of the first operational amplifier and the first resistor through the fourth resistor, and is grounded through the second resistor; the output end of the third operational amplifier is connected with the inverted input end of the first operational amplifier, and the two ends of the third resistor are connected with the inverted input end and the output end of the third operational amplifier respectively.

Description

Technical Field

[0001] This utility model relates to the field of power supply circuit technology, and in particular to a constant current source circuit. Background Technology

[0002] In some applications, it is used as the excitation source for high-precision constant current sources in various sensor devices and high-precision temperature acquisition devices. However, some scenarios require the constant current source circuit to provide high-precision constant current in the nA to μA range. However, when the load changes, the current output of the constant current source circuit will fluctuate, affecting the operational stability of the load. Utility Model Content

[0003] This utility model embodiment provides a constant current source circuit, which uses a voltage regulator circuit to regulate the voltage across the first resistor R7, thereby making the current transmitted to the load side more stable, reducing current fluctuations, and improving the stability of load operation.

[0004] In a first aspect, embodiments of this application provide a constant current source circuit, which includes a constant current circuit and a voltage regulator circuit. The constant current circuit includes a constant current power supply, a first operational amplifier U1, and a first resistor R7. The non-inverting input terminal of the first operational amplifier U1 is connected to the constant current power supply, and the output terminal of the first operational amplifier U1 is connected in series with a load R8 via the first resistor R7. The voltage regulator circuit includes a second operational amplifier U2, a third operational amplifier U3, a second resistor R2, a third resistor R3, a fourth resistor R4, and a fifth resistor R5. The non-inverting input terminal of the second operational amplifier U2 is connected to the first resistor R7. 7. Between the second operational amplifier U2 and the load, the inverting input and output terminals of the second operational amplifier U2 are both connected to the inverting input terminal of the third operational amplifier U3 through the fourth resistor R5; the non-inverting input terminal of the third operational amplifier U3 is connected to the fourth resistor R4 and the second resistor R2 respectively, and is connected between the output terminal of the first operational amplifier U1 and the first resistor R7 through the fourth resistor R4, and grounded through the second resistor R2; the output terminal of the third operational amplifier U3 is connected to the inverting input terminal of the first operational amplifier U1, and the two ends of the third resistor R3 are connected to the inverting input terminal and the output terminal of the third operational amplifier U3 respectively.

[0005] In one possible implementation, the resistance values ​​of the second resistor R2, the third resistor R3, the fourth resistor R4, and the fifth resistor R5 are equal.

[0006] In one possible implementation, the first resistor R7 is an adjustable resistor.

[0007] In one possible implementation, the voltage regulator circuit further includes a first capacitor C1 connected in parallel across the third resistor R3.

[0008] In one possible implementation, the voltage regulator circuit further includes a first operating power supply connected to the first operational amplifier U1.

[0009] In one possible implementation, the first operating power supply includes a first positive voltage power supply and a first negative voltage power supply; the positive power supply pin of the first operational amplifier U1 is connected to the first positive voltage power supply, and the negative power supply pin of the first operational amplifier U1 is connected to the first negative voltage power supply.

[0010] In one possible implementation, the voltage regulator circuit further includes a second operating power supply connected to the second operational amplifier U2.

[0011] In one possible implementation, the second operating power supply includes a second positive voltage power supply and a second negative voltage power supply; the positive power supply pin of the second operational amplifier U2 is connected to the second positive voltage power supply, and the negative power supply pin of the second operational amplifier U2 is connected to the second negative voltage power supply.

[0012] In one possible implementation, the voltage regulator circuit further includes a third operating power supply connected to the third operational amplifier U3.

[0013] In one possible implementation, the third operating power supply includes a third positive voltage power supply and a third negative voltage power supply; the positive power supply pin of the third operational amplifier U3 is connected to the third positive voltage power supply, and the negative power supply pin of the third operational amplifier U3 is connected to the third negative voltage power supply.

[0014] Through the above technical solution, during the process of the constant current circuit supplying power to the load, the third operational amplifier U3 in the voltage regulator circuit collects the voltage at one end of the first resistor R7 through the non-inverting input terminal and provides it to the first operational amplifier U1 of the constant current circuit. The first operational amplifier U1 compares the voltage at one end of the first resistor R7 with the constant current power supply voltage, and adjusts the output voltage at the output terminal of the first operational amplifier U1 according to the comparison result, so that the voltage at one end of the first resistor R7 after balance is consistent with the constant current power supply voltage, stabilizing the stability of the output current of the constant current source circuit, thereby improving the stability of the load operation. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a connection diagram of a constant current source circuit provided in one embodiment of this application;

[0017] Figure 2 This is a schematic diagram of the connection of a constant current source circuit provided in another embodiment of this application. Detailed Implementation

[0018] To better understand the technical solution of this utility model, the embodiments of this utility model will be described in detail below with reference to the accompanying drawings.

[0019] It should be understood that the described embodiments are merely some embodiments of this utility model, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this utility model without creative effort are within the scope of protection of this utility model.

[0020] The terminology used in the embodiments of this utility model is for the purpose of describing particular embodiments only and is not intended to be limiting of the utility model. The singular forms “a,” “the,” and “the” used in the embodiments of this utility model and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0021] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0022] Figure 1 This is a schematic diagram of the connection of a constant current source circuit provided in one embodiment of this application.

[0023] Reference Figure 1 As shown, the constant current source circuit may include a constant current circuit and a voltage regulator circuit.

[0024] The constant current circuit includes a constant current power supply V3, a first operational amplifier U1, and a first resistor R7.

[0025] The non-inverting input terminal (U1+) of the first operational amplifier U1 is connected to the constant current power supply V3, and the output terminal (out1) of the first operational amplifier U1 is connected in series with the load R8 through the first resistor R7.

[0026] Reference Figure 1 As shown, the voltage regulator circuit includes a second operational amplifier U2, a third operational amplifier U3, a second resistor R2, a third resistor R3, a fourth resistor R4, and a fifth resistor R5.

[0027] The non-inverting input (U2+) of the second operational amplifier U2 is connected between the first resistor R7 and the load. The inverting input (U2-) and output (out2) of the second operational amplifier U2 are both connected to the inverting input (U3-) of the third operational amplifier U3 through the fourth resistor R5.

[0028] The non-inverting input (U3+) of the third operational amplifier U3 is connected to the fourth resistor R4 and the second resistor R2, and is connected between the output (out1) of the first operational amplifier U1 and the first resistor R7 through the fourth resistor R4, and grounded through the second resistor R2; the output (out3) of the third operational amplifier U3 is connected to the inverting input (U1-) of the first operational amplifier U1, and the two ends of the third resistor R3 are connected to the inverting input (U3-) and the output (out3) of the third operational amplifier U3, respectively.

[0029] based on Figure 1 The constant current source circuit provided in the illustrated embodiment, when supplying power to the load through this constant current source circuit, connects the non-inverting input terminal (U1+) of the first operational amplifier U1 to the constant current power supply V3, and the current output from the output terminal (out1) of the first operational amplifier U1 is transmitted to the load R8 through the first resistor R7. During the power supply process, the third operational amplifier U3 collects the voltage U at one end of the first resistor R7 through its non-inverting input terminal (U3+). L The third operational amplifier U3 acquires the voltage U across the other end of the first resistor R7 through its inverting input terminal (U3-). R The third operational amplifier U3, together with the second resistor R2, the third resistor R3, the fourth resistor R4, and the fifth resistor R5, forms a subtractor. It obtains the output voltage by subtracting the voltage across the first resistor R7. Specifically, the third operational amplifier U3, acting as a differential operational amplifier, performs differential operations based on the acquired voltage across the first resistor R7 to obtain the voltage U across the first resistor R7. R7 And the voltage U of the first resistor R7 R7 The voltage is transmitted to the first operational amplifier U1 through the output (out3) of the third operational amplifier U3. Furthermore, the first operational amplifier U1 can transmit the voltage U across the first resistor R7. R7 The voltage is compared with the constant current power supply voltage, and the output voltage of the first operational amplifier U1 (out1) is adjusted according to the comparison result, so that the voltage U of the first resistor R7 after balance is achieved. R7 By maintaining consistency with the constant current power supply voltage, the output current of the constant current source circuit is stabilized, thereby improving the stability of load operation.

[0030] In some embodiments, the first resistor R7 can be an adjustable resistor. The constant current source circuit uses active feedback to make the voltage drop across R7 equal to the power supply voltage provided by the constant current power supply V3 applied to the input terminal. Therefore, the current output to the load R8 is equal to the ratio of the voltage of the constant current power supply to the first resistor R7, i.e., V3 / R7. Thus, when there is a deviation between the current output to the load R8 and the target current value, the current output to the load R8 can be made to match the target current value by adjusting the resistor R7.

[0031] In some embodiments, the resistance values ​​of the second resistor R2, the third resistor R3, the fourth resistor R4, and the fifth resistor R5 are equal. When powering the load through this constant current source circuit, to maintain a constant voltage across the first resistor R7, the differential operational amplifier U3 (i.e., the third operational amplifier U3) samples the voltage U across one end of the first resistor R7 through its V+ pin (i.e., the non-inverting input U3+). L The voltage U at the other end of the first resistor R7, sampled by the emitter follower U2 (i.e., the second operational amplifier U2), is received through the V-pin (i.e., the inverting input terminal U3- of the third operational amplifier U3). R Since the resistance values ​​of the second resistor R2, the third resistor R3, the fourth resistor R4, and the fifth resistor R5 are equal (i.e., R2 = R3 = R4 = R5), the differential output voltage of the differential operational amplifier U3 is the voltage U across the first resistor R7. R7 Therefore, the voltage U of the first resistor R7 can be converted through the V- pin (i.e., the inverting input U1-) of the first operational amplifier U1. R7 The voltage is transmitted to the first operational amplifier U1. The first operational amplifier U1 can transmit the voltage U across the first resistor R7. R7 By comparing the voltage with the constant current power supply voltage, the first operational amplifier U1 can adjust the voltage output at its output terminal (out1) to increase or decrease for balance adjustment, thereby ensuring that the voltage across the first resistor R7 is consistent with the constant current power supply voltage. For example, if the constant current power supply voltage is 2.5V and the target current of the load is 10uA, after adjusting the resistance of the first resistor R7 to 250KΩ through the above balance adjustment, the current output to the load R8 is I = 2.5 / 250000 = 10uA. This provides a stable current output to the load R8, improving the stability of the load operation.

[0032] Figure 2 This is a schematic diagram of the connection of a constant current source circuit provided in another embodiment of this application.

[0033] Reference Figure 2 As shown, this constant current source circuit can... Figure 1The circuit shown also includes a first capacitor C2, which is connected in parallel across the third resistor R3. Since the second operational amplifier U2 has a very high input impedance, it only absorbs a small current, such as a pA level current, which has almost no effect on the load R8. Due to the long delay of the control loop, the first capacitor C1 is needed to compensate for the frequency of the first operational amplifier U1. Specifically, by increasing or decreasing the capacitor, the cutoff frequency can be lowered, the passband range can be extended, high-frequency noise can be filtered out, the system's anti-interference capability can be improved, the signal transmission matching can be improved, and the possibility of impedance mismatch can be reduced.

[0034] The voltage regulator circuit of the constant current source circuit provided in this application embodiment may further include a first operating power supply, which is connected to the first operational amplifier U1 and supplies power to the first operational amplifier U1. In some embodiments, the first operating power supply may include a first positive voltage power supply and a first negative voltage power supply. For example, the first positive voltage power supply provides a 5V voltage, and the first negative voltage power supply provides a -5V voltage. The positive power supply pin of the first operational amplifier U1 is connected to the first positive voltage power supply, and the negative power supply pin of the first operational amplifier U1 is connected to the first negative voltage power supply.

[0035] The voltage regulator circuit of the constant current source circuit provided in this application embodiment may further include a second operating power supply, which is connected to the second operational amplifier U2 and supplies power to the second operational amplifier U2. In some embodiments, the second operating power supply may include a second positive voltage power supply and a second negative voltage power supply. For example, the second positive voltage power supply provides a 5V voltage, and the second negative voltage power supply provides a -5V voltage. The positive power supply pin of the second operational amplifier U1 is connected to the second positive voltage power supply, and the negative power supply pin of the second operational amplifier U2 is connected to the second negative voltage power supply.

[0036] The voltage regulator circuit of the constant current source circuit provided in this application embodiment may further include a third operating power supply, which is connected to the third operational amplifier U3 and supplies power to the third operational amplifier U3. In some embodiments, the third operating power supply may include a third positive voltage power supply and a third negative voltage power supply. For example, the third positive voltage power supply provides a 5V voltage, and the third negative voltage power supply provides a -5V voltage. The positive power supply pin of the third operational amplifier U1 is connected to the third positive voltage power supply, and the negative power supply pin of the third operational amplifier U1 is connected to the third negative voltage power supply.

[0037] In some embodiments, the first operating power supply, the second operating power supply, and the third operating power supply can be three independent power supplies or the same power supply.

[0038] In some embodiments, the load R8 can be a sensor device or a high-precision temperature acquisition device. It should be noted that in other embodiments, the load R8 can also be other high-precision acquisition devices, and the device type of the load R8 in this application is not limited.

[0039] The above description is merely a preferred embodiment of this specification and is not intended to limit this specification. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this specification should be included within the scope of protection of this specification.

[0040] It should be noted that the terminals involved in the embodiments of this application may include, but are not limited to, personal computers (PCs), personal digital assistants (PDAs), wireless handheld devices, tablet computers, mobile phones, MP3 players, MP4 players, etc.

[0041] It is understood that the application may be a native application installed on the terminal, or it may be a web application of a browser on the terminal. This application embodiment does not limit this.

[0042] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0043] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection between apparatuses or units through some interfaces, and may be electrical, mechanical, or other forms.

[0044] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0045] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or in a combination of hardware and software functional units.

[0046] The integrated units implemented as software functional units described above can be stored in a computer-readable storage medium. These software functional units, stored in a storage medium, include several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) or processor to execute some steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0047] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A constant current source circuit, characterized in that, The circuit includes: a constant current circuit and a voltage regulator circuit; The constant current circuit includes a constant current power supply, a first operational amplifier U1, and a first resistor R7. Wherein, the non-inverting input terminal of the first operational amplifier U1 is connected to the constant current power supply, and the output terminal of the first operational amplifier U1 is connected in series with the load R8 through the first resistor R7; The voltage regulator circuit includes a second operational amplifier U2, a third operational amplifier U3, a second resistor R2, a third resistor R3, a fourth resistor R4, and a fifth resistor R5; The non-inverting input of the second operational amplifier U2 is connected between the first resistor R7 and the load, and the inverting input and output of the second operational amplifier U2 are both connected to the inverting input of the third operational amplifier U3 through the fourth resistor R5. The non-inverting input terminal of the third operational amplifier U3 is connected to the fourth resistor R4 and the second resistor R2, respectively, and is connected between the output terminal of the first operational amplifier U1 and the first resistor R7 through the fourth resistor R4, and is grounded through the second resistor R2; the output terminal of the third operational amplifier U3 is connected to the inverting input terminal of the first operational amplifier U1, and the two ends of the third resistor R3 are connected to the inverting input terminal and the output terminal of the third operational amplifier U3, respectively.

2. The circuit according to claim 1, characterized in that, The first resistor R7 is an adjustable resistor.

3. The circuit according to claim 1, characterized in that, The resistance values ​​of the second resistor R2, the third resistor R3, the fourth resistor R4, and the fifth resistor R5 are equal.

4. The circuit according to any one of claims 1-3, characterized in that, The voltage regulator circuit also includes a first capacitor C1, which is connected in parallel across the third resistor R3.

5. The circuit according to claim 1, characterized in that, The voltage regulator circuit also includes a first operating power supply, which is connected to the first operational amplifier U1.

6. The circuit according to claim 5, characterized in that, The first operating power supply includes a first positive voltage power supply and a first negative voltage power supply; The positive power supply pin of the first operational amplifier U1 is connected to the first positive voltage power supply, and the negative power supply pin of the first operational amplifier U1 is connected to the first negative voltage power supply.

7. The circuit according to claim 1, characterized in that, The voltage regulator circuit also includes a second operating power supply, which is connected to the second operational amplifier U2.

8. The circuit according to claim 7, characterized in that, The second operating power supply includes a second positive voltage power supply and a second negative voltage power supply; The positive power supply pin of the second operational amplifier U2 is connected to the second positive voltage power supply, and the negative power supply pin of the second operational amplifier U2 is connected to the second negative voltage power supply.

9. The circuit according to claim 1, characterized in that, The voltage regulator circuit also includes a third operating power supply, which is connected to the third operational amplifier U3.

10. The circuit according to claim 9, characterized in that, The third working power supply includes a third positive voltage power supply and a third negative voltage power supply; The positive power supply pin of the third operational amplifier U3 is connected to the third positive voltage power supply, and the negative power supply pin of the third operational amplifier U3 is connected to the third negative voltage power supply.

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