Howland-based drive control circuit

Abstract

The present invention relates to the field of drive control, and particularly to a drive control circuit based on Howland. Among them, the first output terminal of the first operational amplifier is connected to the first end of the detection resistor, and the second end of the detection resistor is connected to the first end of the load resistor. One end of the first circuit is connected between the power supply terminal and the input power supply, and the other end is connected between the second end of the detection resistor and the first end of the load resistor. The first positive input terminal is connected to the first circuit. One end of the second circuit and one end of the third circuit are connected between the first output terminal and the first end of the detection resistor. The other end of the second circuit is connected between the power supply terminal and the ground terminal, and the other end of the third circuit is connected to the second end of the load resistor. The first negative input terminal is connected to the second circuit. The second positive input terminal of the second operational amplifier is connected between the power supply terminal and the ground terminal, the second negative input terminal is connected to the third circuit, and the second output terminal is connected to the second end of the load resistor. The complexity of the drive control circuit is reduced.

Description

Technical Field

[0001] The present invention belongs to the field of drive control, and particularly relates to a drive control circuit based on Howland. Background Art

[0002] Due to its high precision and stability, the Howland constant current source has been widely used in many fields, and it can be applied to sensor drive, precision measuring instruments, current source amplifiers, current excitation systems, audio devices, motor drives and other application fields. Among them, the Howland current pump uses a differential amplifier to apply a voltage across parallel resistors and sets the feedback through an operational amplifier to form a constant current output, so as to generate a voltage-controlled current source capable of driving a wide range of load resistors.

[0003] At present, many Howland applications require the current source to support bipolar (sourcing or sinking) operation, and the bipolar operation of the current source usually requires a bipolar power supply, that is, it requires the simultaneous supply of a positive power supply +Vcc and a negative power supply -Vcc, which increases the complexity of the system. The operational amplifier powered by a single power supply can only amplify the DC voltage that is positive (non-inverting input) or negative (inverting input) with respect to ground. If the signal is an input and an AC signal with respect to ground, then it can only amplify its positive half-wave (non-inverting input) or negative half-wave (inverting input), and the other half-wave will be severely distorted due to cutoff. Summary of the Invention

[0004] In view of this, the present invention aims to provide a drive control circuit based on Howland, which can achieve bipolar linear output by using an operational amplifier powered by a single power supply, reducing the complexity of the drive control circuit.

[0005] To achieve the above object, the technical solution of the present invention is realized as follows:

[0006] A drive control circuit based on Howland, which includes:

[0007] A load resistor and a sense resistor;

[0008] A first operational amplifier, including a first non-inverting input terminal, a first inverting input terminal and a first output terminal; the first output terminal is connected to the first end of the sense resistor, and the second end of the sense resistor is connected to the first end of the load resistor;

[0009] A first circuit, one end is connected between the power supply terminal and the input power supply, and the other end is connected between the second end of the sense resistor and the first end of the load resistor; the first non-inverting input terminal is connected to the first circuit;

[0010] The second circuit and the third circuit, one end of the second circuit and one end of the third circuit are connected between the first output terminal and the first end of the detection resistor, the other end of the second circuit is connected between the power supply terminal and the ground terminal, and the other end of the third circuit is connected to the second end of the load resistor; the first negative input terminal is connected to the second circuit;

[0011] The second operational amplifier, including a second positive input terminal, a second negative input terminal and a second output terminal; the second positive input terminal is connected between the power supply terminal and the ground terminal, the second negative input terminal is connected to the third circuit, and the second output terminal is connected to the second end of the load resistor.

[0012] Further, the resistance value of the load resistor is greater than twenty times the resistance value of the detection resistor.

[0013] Further, the first circuit includes a first resistor, a switch and a second resistor connected in series. One end of the first resistor is connected between the power supply terminal and the input power supply, the other end is connected to one end of the switch, the other end of the switch is connected to one end of the second resistor, and the other end of the second resistor is connected between the second end of the detection resistor and the first end of the load resistor; the first positive input terminal is connected between the first resistor and the switch.

[0014] Further, the second circuit includes a third resistor and a fourth resistor connected in series. One end of the third resistor is connected between the power supply terminal and the ground terminal, the other end is connected to one end of the fourth resistor, and the other end of the fourth resistor is connected between the first output terminal and the first end of the detection resistor; the first negative input terminal is connected between the third resistor and the fourth resistor.

[0015] Further, it further includes a fifth resistor and a sixth resistor. One end of the fifth resistor is connected to the power supply terminal, the other end is connected to one end of the sixth resistor, the other end of the sixth resistor is connected to the positive pole of the input power supply, and the negative pole of the input power supply is connected to the ground terminal; one end of the first circuit is connected between the fifth resistor and the sixth resistor.

[0016] Further, it further includes a seventh resistor and an eighth resistor. One end of the seventh resistor is connected to the power supply terminal, the other end is connected to one end of the eighth resistor, and the other end of the eighth resistor is connected to the ground terminal; the other end of the second circuit is connected between the seventh resistor and the eighth resistor.

[0017] Further, the third circuit includes a ninth resistor and a tenth resistor connected in series. One end of the tenth resistor is connected between the first output terminal and the first end of the detection resistor, the other end of the tenth resistor is connected to one end of the ninth resistor, and the other end of the ninth resistor is connected between the second output terminal and the second end of the load resistor; the second negative input terminal is connected between the tenth resistor and the ninth resistor.

[0018] Further, the resistance value of the ninth resistor is equal to the resistance value of the tenth resistor.

[0019] Further, it further includes an eleventh resistor and a twelfth resistor. One end of the eleventh resistor is connected to the power supply terminal, and the other end is connected to one end of the twelfth resistor. The other end of the twelfth resistor is connected to the ground terminal; the second positive input terminal is connected between the eleventh resistor and the twelfth resistor.

[0020] Further, the resistance value of the eleventh resistor is equal to that of the twelfth resistor.

[0021] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0022] The Howland-based drive control circuit of the present invention can utilize the first positive input terminal and the first negative input terminal of the first operational amplifier to construct a high-impedance current source, enabling the input voltage at the first positive input terminal to be flexibly converted into a current flowing through the load resistor in proportion, that is, the constant current source mode of the drive control circuit. In the constant current source mode, the value of the current flowing through the load resistor is proportional to the voltage value of the input power supply. The magnitude of the current flowing through the load resistor can be controlled by controlling the magnitude of the voltage value of the input power supply, thereby realizing the constant current control of the load by the constant voltage source, ensuring a good linear relationship between the current flowing through the load resistor and the input voltage at the first positive input terminal, and being adaptable to different application scenarios. In this way, by using an operational amplifier powered by a single power supply, bipolar linear output can be achieved, simplifying the power supply configuration, thereby reducing the complexity of the drive control circuit, saving costs while improving the overall reliability of the drive control circuit. At the same time, by switching resistors with different resistance values, different proportional current values flowing through the load resistor can be achieved corresponding to the voltage value of the same input power supply, realizing adjustable proportional constant current drive, thereby improving the overall performance of the drive control circuit. And by adopting the method of bridging the operational amplifier, the current gain effect of the current flowing through the load resistor is doubled, not only improving the current drive ability but also being applicable to high-power usage scenarios, broadening the application range of the drive control circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0024] Figure 1 is the circuit diagram of the Howland-based drive control circuit according to the embodiment of the present invention in the constant current source mode;

[0025] Figure 2 is the circuit diagram of the Howland-based drive control circuit according to the embodiment of the present invention in the constant voltage source mode.

[0026] Description of the reference numerals:

[0027] 10. Drive control circuit; 11. First circuit; 12. Second circuit; 13. Third circuit; V CC . Power supply terminal; V r . Input power supply; GND, Ground terminal; U1, First operational amplifier; U2, Second operational amplifier; R1, First resistor; S1, Switch; R2, Second resistor; R3, Third resistor; R4, Fourth resistor; R5, Fifth resistor; R6, Sixth resistor; R7, Detection resistor; R8, Seventh resistor; R9, Eighth resistor; R 10 . Load resistor; R 11 . Ninth resistor; R 12 . Tenth resistor; R 13 . Eleventh resistor; R 14 . Twelfth resistor. Detailed implementation manners

[0028] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention. Similar elements in different embodiments are labeled with related similar element numbers. In the following embodiments, many detailed descriptions are provided to enable a better understanding of the present invention. However, those skilled in the art can easily recognize that some of the features can be omitted in different situations, or can be replaced by other elements, materials, or methods. In some cases, some operations related to the present invention are not shown or described in the specification to avoid the core part of the present invention being overwhelmed by excessive descriptions. For those skilled in the art, it is not necessary to describe these related operations in detail, and they can fully understand the related operations based on the descriptions in the specification and the general technical knowledge in the art.

[0029] It should be noted that, without conflict, the embodiments and features in the embodiments of the present invention can be combined with each other to form various embodiments. At the same time, the steps or actions in the method description can also be reordered or adjusted in a manner obvious to those skilled in the art. Therefore, the various sequences in the specification and drawings are only for clearly describing a certain embodiment, and do not mean that they are necessary sequences, unless it is stated that a certain sequence must be followed.

[0030] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. In addition, terms such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise stated, the meaning of "a plurality" is two or more.

[0031] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "mounted", "connected", "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific circumstances.

[0032] The present invention will be described in detail below with reference to the drawings and in conjunction with embodiments.

[0033] See Figure 1 and Figure 2 As shown, an embodiment of the present invention provides a Howland-based drive control circuit 10. The drive control circuit 10 includes a load resistor R 10 , a sense resistor R7, a first operational amplifier U1, a second operational amplifier U2, a first circuit 11, a second circuit 12, and a third circuit 13.

[0034] The load resistor R 10 refers to the resistance of the load. The load can be a motor such as a voice coil motor or a DC motor, or other devices, and the present invention is not limited thereto. In one embodiment, the resistance value of the load resistor R 10 is greater than twenty times the resistance value of the sense resistor R7, that is, R 10 > 20 × R7.

[0035] The first operational amplifier U1 includes a first positive input terminal, a first negative input terminal, and a first output terminal. The first output terminal is connected to the first end of the detection resistor R7, and the second end of the detection resistor R7 is connected to the first end of the load resistor R 10 of.

[0036] One end of the first circuit 11 is connected between the power supply terminal VCC and the input power supply V r and the other end is connected between the second end of the detection resistor R7 and the first end of the load resistor R 10 of. The first positive input terminal is connected to the first circuit 11.

[0037] The second circuit 12 and the third circuit 13, one end of the second circuit 12 and one end of the third circuit 13 are connected between the first output terminal and the first end of the detection resistor R7, the other end of the second circuit 12 is connected between the power supply terminal VCC and the ground terminal GND, and the other end of the third circuit 13 is connected to the second end of the load resistor R 10 of. The first negative input terminal is connected to the second circuit 12.

[0038] The second operational amplifier U2 includes a second positive input terminal, a second negative input terminal, and a second output terminal. Among them, the first operational amplifier U1 and the second operational amplifier U2 can be power operational amplifiers. The second positive input terminal is connected between the power supply terminal VCC and the ground terminal GND, the second negative input terminal is connected to the third circuit 13, and the second output terminal is connected to the second end of the load resistor R 10 of.

[0039] The Howland-based drive control circuit 10 of the present invention can utilize the first positive input terminal and the first negative input terminal of the first operational amplifier U1 to construct a high-impedance current source, so that the input voltage of the first positive input terminal can be flexibly converted into the current flowing through the load resistor R 10 i.e., the constant current source mode of the drive control circuit 10. In the constant current source mode, the current value flowing through the load resistor R 10 is proportional to the voltage value of the input power supply V r and the size of the voltage value of the input power supply V r can be controlled to control the size of the current value flowing through the load resistor R 10 thus realizing the constant current control of the constant voltage source to the load and ensuring that the current flowing through the load resistor R 10There is a good linear relationship between the current and the input voltage of the first positive input terminal, which can be adapted to different application scenarios. By using an operational amplifier powered by a single power supply (i.e., the power supply Vcc) in this way, a bipolar linear output can be achieved, simplifying the power supply configuration, thereby reducing the complexity of the drive control circuit 10, saving costs while improving the overall reliability of the drive control circuit 10. At the same time, by switching resistors with different resistance values, different proportional currents flowing through the load resistor R r corresponding to different voltage values of the input power supply V 10 can be achieved, realizing adjustable proportional constant current drive, thereby improving the overall performance of the drive control circuit 10. And by adopting the method of bridging the operational amplifier, the current gain effect of the current flowing through the load resistor R 10 is doubled, not only improving the current driving ability, but also being applicable to high-power usage scenarios, broadening the application range of the drive control circuit 10.

[0040] In one embodiment, the first circuit 11 includes a first resistor R1, a switch S1, and a second resistor R2 connected in series. One end of the first resistor R1 is connected between the power supply terminal V CC and the input power supply V r , the other end is connected to one end of the switch S1. The other end of the switch S1 is connected to one end of the second resistor R2, and the other end of the second resistor R2 is connected between the second end of the detection resistor R7 and the first end of the load resistor R 10 . The first positive input terminal is connected between the first resistor R1 and the switch S1. In this way, the drive control circuit 10 can switch between the constant voltage source mode and the constant current source mode through the switch S1, forming a constant current source and constant voltage source switchable and reusable circuit, expanding the function of the drive control circuit 10 at low cost and achieving function multiplexing of the drive control circuit 10. As Figure 1 shown, when the switch S1 is in the closed state, the drive control circuit 10 is in the constant current source mode. As Figure 2 shown, when the switch S1 is in the open state, the drive control circuit 10 is in the constant voltage source mode, where the input voltage of the first positive input terminal can be flexibly converted into the voltage across the load resistor R 10 to form a stable voltage source to meet the loads with different voltage requirements. In the constant voltage source mode of the drive control circuit 10, the voltage value across the load resistor R 10 is proportional to the voltage value of the input power supply V r . By controlling the magnitude of the voltage value of the input power supply V r , the magnitude of the voltage value across the load resistor R 10 can be controlled, thereby achieving constant voltage control of the load by the constant voltage source.

[0041] In one embodiment, the second circuit 12 includes a third resistor R3 and a fourth resistor R4 connected in series. One end of the third resistor R3 is connected between the power supply terminal V CC and the ground terminal GND, and the other end is connected to one end of the fourth resistor R4. The other end of the fourth resistor R4 is connected between the first output terminal and the first end of the detection resistor R7. The first negative input terminal is connected between the third resistor R3 and the fourth resistor R4.

[0042] In this embodiment, the ratio of the resistance value of the second resistor R2 to the resistance value of the first resistor R1 is equal to the ratio of the resistance value of the fourth resistor R4 to the resistance value of the third resistor R3, that is

[0043] In one embodiment, the drive control circuit 10 further includes a fifth resistor R5 and a sixth resistor R6. One end of the fifth resistor R5 is connected to the power supply terminal V CC , and the other end is connected to one end of the sixth resistor R6. The other end of the sixth resistor R6 is connected to the positive electrode of the input power supply V r , and the negative electrode of the input power supply V r is connected to the ground terminal GND. One end of the first circuit 11 is connected between the fifth resistor R5 and the sixth resistor R6.

[0044] In one embodiment, the drive control circuit 10 further includes a seventh resistor R8 and an eighth resistor R9. One end of the seventh resistor R8 is connected to the power supply terminal V CC , and the other end is connected to one end of the eighth resistor R9. The other end of the eighth resistor R9 is connected to the ground terminal GND. The other end of the second circuit 12 is connected between the seventh resistor R8 and the eighth resistor R9.

[0045] In this embodiment, the resistance value of the fifth resistor R5 is equal to the resistance value of the sixth resistor R6, the resistance value of the sixth resistor R6 is equal to the resistance value of the seventh resistor R8, and the resistance value of the seventh resistor R8 is equal to the resistance value of the eighth resistor R9, that is, R5 = R6 = R8 = R9.

[0046] In one embodiment, the third circuit 13 includes a ninth resistor R 11 and a tenth resistor R 12 connected in series. One end of the tenth resistor R 12 is connected between the first output terminal and the first end of the detection resistor R7. The other end of the tenth resistor R 12 is connected to one end of the ninth resistor R 11 . The other end of the ninth resistor R 11 is connected between the second output terminal and the second end of the load resistor R 10 . The second negative input terminal is connected between the tenth resistor R 12 and the ninth resistor R 11 .

[0047] In this embodiment, the resistance value of the ninth resistor R 11 is equal to that of the tenth resistor R 12 , that is, R 11 = R 12 .

[0048] In one embodiment, the drive control circuit 10 further includes an eleventh resistor R 13 and a twelfth resistor R 14 . One end of the eleventh resistor R 13 is connected to the power supply terminal V CC , and the other end is connected to one end of the twelfth resistor R 14 . The other end of the twelfth resistor R 14 is connected to the ground terminal GND. The second positive input terminal is connected between the eleventh resistor R 13 and the twelfth resistor R 14 .

[0049] In this embodiment, the resistance value of the eleventh resistor R 13 is equal to that of the twelfth resistor R 14 , that is, R 13 = R 14 .

[0050] Figure 1 is the circuit diagram of the Howland-based drive control circuit in the constant current source mode according to the embodiment of the present invention. Referring to Figure 1 as shown, in this embodiment, it can be known from the virtual open characteristic of the first operational amplifier U1 and the principle of Thevenin equivalent circuit that:

[0051]

[0052]

[0053] Among them, , , after simplification, the following formula can be obtained:

[0054]

[0055]

[0056] It can be known from the virtual short characteristic of the first operational amplifier U1 that:

[0057] It can be known from Ohm's law that the current flowing through the load resistor R 10 is:

[0058]

[0059] Substituting V 1 andV Substituting 2 gives:

[0060]

[0061] It can be seen from this that since the resistance values of the resistors (R1, R2, R5, R7) are fixed, in the constant current source mode of the drive control circuit 10, the current value flowing through the load resistor R 10 is in a fixed proportional relationship with the voltage value of the input power supply V r . The current value flowing through the load resistor R r can be controlled by controlling the magnitude of the voltage value of the input power supply V 10 . Furthermore, the constant current control of the load by the constant voltage source is achieved. And by switching the first resistor R1, the second resistor R2, the fifth resistor R5 and the detection resistor R7 with different resistance values, different proportional current values flowing through the load resistor R r corresponding to the voltage value of the same input power supply V 10 can be realized, and adjustable proportional constant current drive is achieved.

[0062] For the second operational amplifier U2:

[0063]

[0064] It can be known from the virtual short characteristic of the second operational amplifier U2 that:

[0065] Therefore, the second operational amplifier U2 can effectively double the current gain effect of the current flowing through the load resistor R 10 .

[0066] Figure 2 This is the circuit diagram of the drive control circuit based on Howland in the constant voltage source mode described in the embodiment of the present invention. Referring to Figure 2 as shown, it can be known from the virtual open characteristic of the first operational amplifier U1 and the principle of Thevenin equivalent circuit that:

[0067]

[0068]

[0069] It can be known from the virtual short characteristic of the first operational amplifier U1 that:

[0070] Combining the above formulas gives:

[0071]

[0072] For the second operational amplifier U2:

[0073]

[0074] According to the virtual short - circuit characteristic of the second operational amplifier U2, it can be known that:

[0075] The second operational amplifier U2 can effectively double the current gain effect flowing through the load resistor R 10 and we can get:

[0076]

[0077] Substituting V 3 and V 4 into it, the voltage value applied across the load resistor R 10 is:

[0078]

[0079] From this, it can be known that since the resistance values of the resistors (R3, R4, R8) are fixed, in the constant - voltage source mode of the drive control circuit 10, the voltage value applied across the load resistor R 10 is in a proportional relationship with the voltage value of the input power supply V r . The voltage value applied across the load resistor R r can be controlled by controlling the magnitude of the voltage value of the input power supply V 10 , thus realizing the constant - voltage control of the constant - voltage source over the load.

[0080] In summary, the embodiments of the present invention provide an efficient, flexible and easy - to - implement solution, which is applicable to various electronic devices and control systems, and provides an excellent application basis for current control and voltage control.

[0081] It should be understood that various forms of the processes shown above can be used, re - ordering, adding or deleting steps. For example, the steps recorded in the present invention disclosure can be executed in parallel, sequentially or in a different order, as long as the desired results of the technical solution disclosed in the present invention can be achieved, and no limitation is made herein.

[0082] The above - mentioned specific implementation manners do not constitute a limitation to the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub - combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A Howland-based drive control circuit, characterized in that, Comprising: A load resistor and a detection resistor; A first operational amplifier, including a first positive input terminal, a first negative input terminal, and a first output terminal; The first output terminal is connected to the first end of the detection resistor, the second end of the detection resistor is connected to the first end of the load resistor, and the first operational amplifier is powered by a single power supply; A first circuit, one end is connected between the power supply terminal and the input power supply, and the other end is connected between the second end of the detection resistor and the first end of the load resistor. The first circuit includes a first resistor, a switch, and a second resistor connected in series; the first positive input terminal is connected between the first resistor and the switch; A fifth resistor and a sixth resistor, one end of the fifth resistor is connected to the power supply terminal, the other end is connected to one end of the sixth resistor, the other end of the sixth resistor is connected to the positive pole of the input power supply, and the negative pole of the input power supply is connected to the ground terminal; one end of the first circuit is connected between the fifth resistor and the sixth resistor; A second circuit and a third circuit, one end of the second circuit and one end of the third circuit are connected between the first output terminal and the first end of the detection resistor, the other end of the second circuit is connected between the power supply terminal and the ground terminal, and the other end of the third circuit is connected to the second end of the load resistor; the first negative input terminal is connected to the second circuit; The second circuit includes a third resistor and a fourth resistor connected in series; the first negative input terminal is connected between the third resistor and the fourth resistor; A seventh resistor and an eighth resistor, one end of the seventh resistor is connected to the power supply terminal, the other end is connected to one end of the eighth resistor, the other end of the eighth resistor is connected to the ground terminal; the other end of the second circuit is connected between the seventh resistor and the eighth resistor; A second operational amplifier, including a second positive input terminal, a second negative input terminal, and a second output terminal; the second positive input terminal is connected between the power supply terminal and the ground terminal, the second negative input terminal is connected to the third circuit, and the second output terminal is connected to the second end of the load resistor. The second operational amplifier is powered by a single power supply; Among them, , When the switch is in the closed state, wherein, R1 is the first resistor, R2 is the second resistor, R3 is the third resistor, R4 is the fourth resistor, R5 is the fifth resistor, R6 is the sixth resistor, R7 is the detection resistor, R8 is the seventh resistor, R9 is the eighth resistor, I is the current flowing through the load resistor, and Vr is the input power supply.

2. The Howland-based drive control circuit according to claim 1, wherein The resistance value of the load resistor is greater than twenty times the resistance value of the detection resistor.

3. The Howland-based drive control circuit according to claim 1, wherein One end of the first resistor is connected between the power supply terminal and the input power supply, the other end is connected to one end of the switch, the other end of the switch is connected to one end of the second resistor, and the other end of the second resistor is connected between the second end of the detection resistor and the first end of the load resistor.

4. The Howland-based drive control circuit according to claim 1, characterized in that, One end of the third resistor is connected between the power supply terminal and the ground terminal, the other end is connected to one end of the fourth resistor, and the other end of the fourth resistor is connected between the first output terminal and the first end of the detection resistor.

5. The Howland-based drive control circuit according to claim 1, characterized in that, The third circuit includes a ninth resistor and a tenth resistor connected in series. One end of the tenth resistor is connected between the first output terminal and the first end of the detection resistor. The other end of the tenth resistor is connected to one end of the ninth resistor. The other end of the ninth resistor is connected between the second output terminal and the second end of the load resistor. The second negative input terminal is connected between the tenth resistor and the ninth resistor.

6. The Howland-based drive control circuit according to claim 5, wherein, The resistance value of the ninth resistor is equal to that of the tenth resistor.

7. The Howland-based drive control circuit according to claim 1, characterized in that, It further includes an eleventh resistor and a twelfth resistor. One end of the eleventh resistor is connected to the power supply terminal, and the other end is connected to one end of the twelfth resistor. The other end of the twelfth resistor is connected to the ground terminal. The second positive input terminal is connected between the eleventh resistor and the twelfth resistor.

8. The Howland-based drive control circuit according to claim 7, wherein The resistance value of the eleventh resistor is equal to that of the twelfth resistor.

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