UA-level positive and negative output constant current source circuit

Abstract

The utility model relates to a uA-level positive and negative output constant current source circuit, which comprises a microcontroller, an H-bridge module, a DAC (Digital-to-Analog Converter) circuit and a current adjusting module, the microcontroller controls the H-bridge module, and the H-bridge module is connected with a load and outputs forward current or negative current to the load; the microcontroller controls the DAC circuit to output a DA value, and the DAC circuit is connected with the current adjusting module and used for controlling the stepping precision of the current output to the load. According to the utility model, on one hand, the flow direction of current passing through a load can be controlled through the H-bridge circuit, and positive and negative current output is realized; on the other hand, the stepping precision of the current passing through the load is controlled through the current adjusting module, and uA-level stepping current is achieved; compared with a common constant current source circuit, the constant current source circuit can better meet the electric control requirements of special loads such as a liquid lens.

Description

Technical Field

[0001] The utility model relates to the technical field of electronic circuits, in particular to a uA-level positive and negative output constant current source circuit. Background Art

[0002] Traditional optical lenses are made of optical materials and cannot change optical parameters such as curvature. Liquid lenses use one or more liquids as media and can dynamically adjust the focal length of the lens by changing the surface curvature. Liquid lenses based on liquid lenses have the advantages of fast zoom, no mechanical movement, and less wear. In the field of image vision, they can achieve single millisecond zoom speeds.

[0003] The liquid lens part is electrically controlled, changing the internal charge distribution and conductivity through an external control circuit. For this type of special load, the existing control circuit has difficulty in achieving positive and negative current output and high-precision step current, and thus has difficulty in achieving fast and precise control. Utility Model Content

[0004] To this end, the technical problem to be solved by the utility model is to overcome the technical difficulty of insufficient step current accuracy of the control circuit of special loads such as liquid lenses in the prior art, and to provide a uA-level positive and negative output constant current source circuit that can achieve uA-level step current regulation accuracy while outputting positive and negative currents.

[0005] In order to solve the above technical problems, the utility model provides a uA level positive and negative output constant current source circuit, which includes:

[0006] A microcontroller, wherein the microcontroller is used to output a first control signal and a second control signal;

[0007] An H-bridge module, wherein the H-bridge module is connected to the microcontroller to receive a first control signal of the microcontroller, and the H-bridge module is connected to a load and outputs a positive current or a negative current to the load according to the first control signal;

[0008] A DAC circuit, the DAC circuit is connected to the microcontroller to receive the second control signal and output a DA value;

[0009] A current regulating module is connected to the DAC circuit and the H-bridge module, and is used to adjust the step accuracy of the current output to the load to uA level according to the DA value.

[0010] In one embodiment of the utility model, the current regulation module includes an operational amplifier, a feedback resistor and a current sampling resistor; the first end of the current sampling resistor is grounded, the second end of the current sampling resistor is connected to the first end of the feedback resistor, and the second end of the feedback resistor is connected to the inverting input end of the operational amplifier.

[0011] In one embodiment of the present invention, the output end of the DAC circuit is connected to the inverting input end of the operational amplifier through a first resistor.

[0012] In one embodiment of the present utility model, the resistance value of the current sampling resistor is set to 2.49Ω, the resistance value of the feedback resistor is set to 1000Ω, and the resistance value of the first resistor is set to 2000Ω.

[0013] In one embodiment of the utility model, the current regulating module includes a voltage regulator, a first regulating resistor and a second regulating resistor; the anode of the voltage regulator is grounded, and the cathode of the voltage regulator is connected to a power supply; the reference electrode of the voltage regulator is connected to the cathode of the voltage regulator, and the cathode of the voltage regulator is connected to the first end of the first regulating resistor, the second end of the first regulating resistor is connected to the first end of the second regulating resistor, and the second end of the second regulating resistor is grounded; the in-phase input end of the operational amplifier is connected to the second end of the first regulating resistor.

[0014] In an embodiment of the present invention, the reference voltage of the non-inverting input terminal of the operational amplifier is set to 0.78V.

[0015] In one embodiment of the present utility model, the H-bridge module includes an H-bridge circuit, and the H-bridge circuit includes a first transistor, a second transistor, a third transistor, and a fourth transistor;

[0016] The first transistor and the second transistor are both configured as P-channel transistors; the third transistor and the fourth transistor are both configured as N-channel transistors;

[0017] The source of the first transistor is connected to the drain of the third transistor, and the first end of the load is connected between the source of the first transistor and the drain of the third transistor; the source of the second transistor is connected to the drain of the fourth transistor, and the second end of the load is connected between the source of the second transistor and the drain of the fourth transistor;

[0018] The source of the third transistor and the source of the fourth transistor are both connected to the output pin of the operational amplifier of the current regulating module.

[0019] In one embodiment of the utility model, the H-bridge module also includes an H-bridge driving circuit, which is connected to the microcontroller; the H-bridge driving circuit includes a converter, four pins of which are respectively connected to the gates of the first transistor, the second transistor, the third transistor and the fourth transistor.

[0020] In one embodiment of the present invention, a BUCK buck circuit is further included, and an output end of the BUCK buck circuit is connected to the drain of the first transistor and the drain of the second transistor.

[0021] In one embodiment of the present invention, the DAC circuit includes a DAC chip, the resolution of the DAC chip is set to 16 bits, and the reference voltage of the DAC chip is 2.5V.

[0022] The above technical solution of the utility model has the following beneficial effects compared with the prior art:

[0023] The uA-level positive and negative output constant current source circuit described in the utility model can, on the one hand, simultaneously control the current flow direction passing through the load through the H-bridge circuit to achieve positive and negative current output; on the other hand, it can control the current step accuracy passing through the load through the current regulation module to achieve uA-level step current size; compared with ordinary constant current source circuits, it can better meet the electrical control requirements of special loads such as liquid lenses. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to make the content of the utility model easier to understand, the utility model is further described in detail according to the specific embodiments of the utility model in combination with the accompanying drawings, wherein:

[0025] Figure 1 This is a schematic diagram of the structure of the uA-level positive and negative output constant current source circuit in the preferred embodiment of the utility model;

[0026] Figure 2 This is a circuit diagram of a uA-level positive and negative output constant current source circuit in a preferred embodiment of the utility model;

[0027] Figure 3 for Figure 2 Schematic diagram of the H-bridge circuit in;

[0028] Figure 4 for Figure 2 Schematic diagram of the H-bridge drive circuit;

[0029] Figure 5 for Figure 2 Schematic diagram of the current regulation module.

[0030] Explanation of the reference numerals in the specification: 1. microcontroller; 21. H-bridge driving circuit; 22. H-bridge circuit; 3. BUCK step-down circuit; 4. DAC circuit; 5. current regulation module. DETAILED DESCRIPTION

[0031] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0032] Example

[0033] Reference Figure 1 to Figure 5 As shown, the utility model provides a uA-level positive and negative output constant current source circuit, the uA-level positive and negative output constant current source circuit includes a microcontroller 1, an H-bridge module, a BUCK buck circuit 3, a DAC circuit 4 and a current regulation module 5; wherein the H-bridge module includes an H-bridge driving circuit 21 and an H-bridge controlled circuit (hereinafter referred to as "H-bridge circuit"), the microcontroller 1 controls the H-bridge module to output a first control signal, the BUCK buck circuit 3 realizes positive and negative current output through the load through the H-bridge circuit 22; the microcontroller 1 controls the DAC circuit 4 to output a second control signal, and the DAC circuit 4 controls the step current accuracy by the current regulation module 5 after conversion. The utility model is aimed at special loads such as liquid lenses, and can achieve positive and negative current output and uA-level step current accuracy. Compared with ordinary constant current source circuits, it has higher adaptability to the load and meets the electrical control requirements of the load.

[0034] Specifically, refer to Figure 2 As shown, the microprocessor constitutes the main control circuit of the uA-level positive and negative output constant current source circuit; some output pins of the microprocessor are connected to the H-bridge driving circuit 21 of the H-bridge module, which is used to drive the H-bridge circuit 22 to achieve positive and negative current output. At least some pins of the microprocessor other than those used to connect to the H-bridge module are connected to the DAC circuit 4, which is used to control the step current accuracy passing through the load.

[0035] Specifically, refer to Figure 2 As shown, the H-bridge module includes the H-bridge driving circuit 21 and the H-bridge circuit 22; the H-bridge driving circuit 21 is connected to the microcontroller 1 and is used to control the H-bridge circuit 22, and the H-bridge circuit 22 includes a first transistor Q1, a second transistor Q2, a third transistor Q3 and a fourth transistor Q4; the H-bridge driving circuit 21 includes a converter U2, and the converter U2 is set to CD40109BPWR. Four pins of the converter U2 are respectively connected to the gates of the four groups of transistors in the H-bridge circuit 22 to control their conduction states. At the same time, the gates of the four groups of transistors are also grounded through a 10KΩ resistor respectively; refer to Figure 4As shown, the 13th pin of the converter U2 is used to connect and control the gate of the first transistor Q1, and the first transistor Q1 is set as a P-channel transistor; the 11th pin of the converter U2 is used to connect and control the gate of the second transistor Q2, and the second transistor Q2 is set as a P-channel transistor; the 5th pin of the converter U2 is used to connect and control the gate of the third transistor Q3, and the third transistor Q3 is set as an N-channel transistor; the 4th pin of the converter U2 is used to connect and control the gate of the fourth transistor Q4, and the fourth transistor Q4 is set as an N-channel transistor.

[0036] Further, refer to Figure 3 As shown, two groups of P-channel transistors are symmetrically arranged, and two groups of N-channel transistors are symmetrically arranged. The output end of the BUCK step-down circuit 3 is connected to the drain of the first transistor Q1 and the drain of the second transistor Q2 for output voltage control; the source of the first transistor Q1 is connected to the drain of the third transistor Q3, and the source of the second transistor Q2 is connected to the drain of the fourth transistor Q4; the source of the third transistor Q3 and the source of the fourth transistor Q4 are connected to the current regulation module 5.

[0037] Continue, refer to Figure 3 As shown, the H-bridge circuit 22 is also connected to a load, and the load is located between two groups of P-channel transistors and two groups of N-channel transistors; the first end of the load is connected between the source of the first transistor Q1 and the drain of the third transistor Q3, and the second end of the load is connected between the source of the second transistor Q2 and the drain of the fourth transistor Q4. The H-bridge driving circuit 21 controls the on and off of the four transistors to achieve the flow direction control of the current passing through the load.

[0038] In a preferred embodiment of the utility model, when the first transistor Q1 and the fourth transistor Q4 are turned on and the second transistor Q2 and the third transistor Q3 are turned off, the current flows from the first end to the second end of the load, and the current output to the load is a forward current.

[0039] When the first transistor Q1 and the fourth transistor Q4 are turned off and the second transistor Q2 and the third transistor Q3 are turned on, current flows from the second end to the first end of the load, and the current output to the load is a negative current.

[0040] Specifically, refer to Figure 2 and Figure 5As shown, the DAC circuit 4 is connected to the microcontroller 1 to receive the second control signal, and the DAC circuit 4 performs digital-to-analog conversion to output a DA value; the DAC circuit 4 includes a DAC chip U3, and the first pin of the DAC chip U3 is connected to the current regulation module 5 to provide a voltage V DAC In a preferred embodiment of the utility model, the resolution of the DAC chip U3 is set to 16 bits, and the reference voltage of the DAC chip U3 is 2.5V.

[0041] Specifically, refer to Figure 5 As shown, the current regulating module 5 includes an operational amplifier U4 and a first resistor R8; the model of the operational amplifier U4 is preferably set to LMH6642MF, and the resistance value of the first resistor R8 is preferably set to 2000Ω; the first end of the first resistor R8 is connected to the first pin of the DAC circuit 4, and the voltage of the first end of the first resistor R8 is V DAC , the second end of the first resistor R8 is connected to the inverting input end of the operational amplifier U4, and the voltage of the inverting output end of the operational amplifier U4, that is, the voltage of the second end of the first resistor R8, is set to V A .

[0042] Next, the current regulation module 5 also includes a feedback resistor R12 and a current sampling resistor R15; preferably, the resistance of the feedback resistor R12 is set to 1000Ω, and the resistance of the current sampling resistor R15 is set to 2.49Ω. The first end of the current sampling resistor R15 is grounded, the second end of the current sampling resistor R15 is connected to the first end of the feedback resistor R12, and the second end of the feedback resistor R12 is connected to the inverting input terminal of the operational amplifier U4. The voltage at the second end of the feedback resistor R12 is the voltage V at the inverting output terminal of the operational amplifier U4. A , the voltage at the first end of the feedback resistor R12 is consistent with the voltage at the second end of the current sampling resistor R15 and is set to V B ; The nodes of the inverting output terminal of the operational amplifier U4 can be obtained according to Kirchhoff's current law,

[0043] (V DAC -V A ) / R8=(V A -V B ) / R12 (1)

[0044] V B =I out *R15 (2)

[0045] Among them, I out The current of the current regulating module 5 is set.

[0046] Further, refer to Figure 5 As shown, the current regulating module 5 also includes a voltage stabilizer U5; the voltage stabilizer U5 is set as a three-terminal controllable precision voltage source, preferably its model is set to TL431, and it has a 2.5V reference source inside; the anode of the voltage stabilizer U5 is grounded, and the cathode of the voltage stabilizer U5 is connected to the power supply; the reference electrode of the voltage stabilizer U5 is connected to the cathode of the voltage stabilizer U5, and at this time, the cathode of the voltage stabilizer U5 outputs a fixed voltage value of 2.5V. The cathode of the voltage stabilizer U5 is also grounded through a capacitor C10 for filtering.

[0047] Continue, refer to Figure 5 As shown, the current regulating module 5 also includes a first regulating resistor R10 and a second regulating resistor R13; the cathode of the voltage regulator U5 is connected to the first end of the first regulating resistor R10, the second end of the first regulating resistor R10 is connected to the first end of the second regulating resistor R13, and the second end of the second regulating resistor R13 is grounded; preferably, the resistance of the first regulating resistor R10 is 2.2KΩ, and the resistance of the second regulating resistor R13 is 1KΩ; since the voltage at the first end of the first regulating resistor R10 is the fixed voltage value of 2.5V output by the voltage regulator U5, it can be obtained that the voltage at the second end of the first regulating resistor R10 and the voltage at the first end of the second regulating resistor R13 are 0.78V; the in-phase input terminal of the operational amplifier U4 is connected to the second end of the first regulating resistor R10, that is, the reference voltage of the in-phase input terminal of the operational amplifier U4 is 0.78V.

[0048] It should be noted that a negative feedback circuit is formed on one side of the inverting input terminal of the operational amplifier U4. Due to the existence of negative feedback, according to the "virtual short" of the operational amplifier U4, it can be known that the potentials of the inverting input terminal and the inverting input terminal are equal, that is, the voltage V A =0.78V.

[0049] Substituting the resistance value of R15 into equation (2), we get V B =2.49I out ;

[0050] V A , R8, R12 and V B Substituting the expression into (1), we can simplify it to get

[0051] I out =0.47-0.2V DAC

[0052] Since the bit width of the DAC chip U3 is 16 bits and the reference voltage is 2.5V, V DAC The minimum step is

[0053] 2.5V / 2 16 =38uV;

[0054] Then I out The minimum step current is 0.2*38uV=7.6uA, which can achieve uA-level current step accuracy adjustment. Figure 2 As shown, the current regulating module 5 is also connected to the H-bridge circuit 22, and the current regulating module 5 is used to control the step accuracy of the current output to the load; specifically, the source of the third transistor Q3 and the source of the fourth transistor Q4 are connected to the second end of the current sampling resistor and the output pin of the operational amplifier U4 of the current regulating module 5 through a packaged transistor to achieve control of the load current step accuracy.

[0055] Obviously, the above embodiments are merely examples for the purpose of clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention of the utility model.

Claims

1. A uA level positive and negative output constant current source circuit, characterized in that: include, A microcontroller, wherein the microcontroller is used to output a first control signal and a second control signal; An H-bridge module, wherein the H-bridge module is connected to the microcontroller to receive a first control signal of the microcontroller, and the H-bridge module is connected to a load and outputs a positive current or a negative current to the load according to the first control signal; A DAC circuit, the DAC circuit is connected to the microcontroller to receive the second control signal and output a DA value; A current regulating module is connected to the DAC circuit and the H-bridge module, and is used to adjust the step accuracy of the current output to the load to uA level according to the DA value.

2. The uA level positive and negative output constant current source circuit according to claim 1, characterized in that: The current regulating module includes an operational amplifier, a feedback resistor and a current sampling resistor; the first end of the current sampling resistor is grounded, the second end of the current sampling resistor is connected to the first end of the feedback resistor, and the second end of the feedback resistor is connected to the inverting input end of the operational amplifier.

3. The uA level positive and negative output constant current source circuit according to claim 2, characterized in that: The output end of the DAC circuit is connected to the inverting input end of the operational amplifier through a first resistor.

4. The uA level positive and negative output constant current source circuit according to claim 3, characterized in that: The resistance value of the current sampling resistor is set to 2.49Ω, the resistance value of the feedback resistor is set to 1000Ω, and the resistance value of the first resistor is set to 2000Ω.

5. The uA level positive and negative output constant current source circuit according to claim 2, characterized in that: The current regulating module includes a voltage regulator, a first regulating resistor and a second regulating resistor; the anode of the voltage regulator is grounded, and the cathode of the voltage regulator is connected to a power supply; the reference electrode of the voltage regulator is connected to the cathode of the voltage regulator, and the cathode of the voltage regulator is connected to the first end of the first regulating resistor, the second end of the first regulating resistor is connected to the first end of the second regulating resistor, and the second end of the second regulating resistor is grounded; the in-phase input end of the operational amplifier is connected to the second end of the first regulating resistor.

6. The uA level positive and negative output constant current source circuit according to claim 2 or 5, characterized in that: The reference voltage of the non-inverting input terminal of the operational amplifier is set to 0.78V.

7. The uA level positive and negative output constant current source circuit according to claim 1, characterized in that: The H-bridge module includes an H-bridge circuit, and the H-bridge circuit includes a first transistor, a second transistor, a third transistor and a fourth transistor; The first transistor and the second transistor are both configured as P-channel transistors; the third transistor and the fourth transistor are both configured as N-channel transistors; The source of the first transistor is connected to the drain of the third transistor, and the first end of the load is connected between the source of the first transistor and the drain of the third transistor; the source of the second transistor is connected to the drain of the fourth transistor, and the second end of the load is connected between the source of the second transistor and the drain of the fourth transistor; The source of the third transistor and the source of the fourth transistor are both connected to the output pin of the operational amplifier of the current regulating module.

8. The uA level positive and negative output constant current source circuit according to claim 7, characterized in that: The H-bridge module also includes an H-bridge driving circuit, which is connected to the microcontroller; the H-bridge driving circuit includes a converter, four pins of which are respectively connected to the gates of the first transistor, the second transistor, the third transistor and the fourth transistor.

9. The uA level positive and negative output constant current source circuit according to claim 7, characterized in that: It also includes a BUCK buck circuit, the output end of which is connected to the drain of the first transistor and the drain of the second transistor.

10. The uA level positive and negative output constant current source circuit according to claim 1, characterized in that: The DAC circuit includes a DAC chip, the resolution of the DAC chip is set to 16 bits, and the reference voltage of the DAC chip is 2.5V.

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