CN217689887U - Heavy current high accuracy constant current source circuit - Google Patents
Heavy current high accuracy constant current source circuit Download PDFInfo
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- CN217689887U CN217689887U CN202221970773.9U CN202221970773U CN217689887U CN 217689887 U CN217689887 U CN 217689887U CN 202221970773 U CN202221970773 U CN 202221970773U CN 217689887 U CN217689887 U CN 217689887U
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Abstract
A high-current high-precision constant current source circuit comprises: the MOS tube switch unit is connected between a load RL connected with the VCC and GND, and the bias voltage unit is used for providing a direct current voltage to the gain compression unit; a control voltage unit for providing a control voltage to the gain compression unit; the gain compression unit is used for adding and combining the direct-current voltage and the control voltage, performing gain compression or increasing, and outputting a single voltage to the comparison control unit; the input end of the feedback unit is connected between the MOS tube switch unit and GND, and the output end of the feedback unit is connected with the other input end of the comparison control unit and is used for acquiring a sampling voltage from the input end of the feedback unit and transmitting the sampling voltage to the comparison control unit; and the output end of the comparison control unit is connected with the MOS tube switching unit and is used for comparing the single voltage with the sampling voltage to output a control voltage Vctrl to control the opening or closing of the MOS tube switching unit. The control precision is greatly improved, and the constant current capability of large current is also greatly improved.
Description
Technical Field
The application relates to the technical field of simulation application circuits, relates to a constant current source, and particularly relates to a large-current high-precision constant current source circuit.
Background
The common constant current source circuit structure is shown in fig. 1, a fixed voltage is applied to a control input, a DC power supply is set to a required power supply range, in an initial state of a system, a switch MOS transistor is not turned on, the voltage at Vr is 0, an operational amplifier is used as a comparator, and because the input voltage is greater than 0, the operational amplifier outputs a high level at the moment, the control switch MOS transistor is turned on, a current flows out from the DC power supply, passes through a load, the switch MOS transistor, a sampling resistor and finally flows back to the ground. The current can produce a new Vr voltage on sampling resistor R, the new Vr voltage will be compared with the input voltage again, the operational amplifier can renew the output value again, the on-state of the switch MOS tube is adjusted, after a plurality of adjustments, the Vr voltage will be the same as the control voltage, the switch MOS tube reaches the stable on-state degree, the current flowing through the switch MOS tube tends to be constant, the current in the load is also constant, and the constant current source constant-current process is finished. After the next input voltage update, the previous process will be repeated until the current is once again constant.
The traditional constant current source circuit is easy to control the current with high precision in the aspect of small current and fine precision application, but the control precision is deficient in the constant current scene of large current; moreover, because the control voltage range of the constant current region of the switch MOS transistor is generally small, and is only 1V-2V in common, if a DAC chip with a common 0V-5V output range is used, the actual control output voltage is only 1V-2V, and a voltage output range close to 80% is not completely utilized, and before entering the constant current region of the switch MOS transistor, the start voltage Vth of the switch MOS transistor needs to be output first, and the switch MOS transistors of the same model also have the start voltage Vth, so that the control accuracy of the constant current source is reduced, and meanwhile, the control uncertainty is increased.
SUMMERY OF THE UTILITY MODEL
In order to solve the defects of the prior art, the application provides a high-current high-precision constant current source circuit, the control precision is greatly improved, and the constant current capacity of the high current is also greatly improved.
In order to achieve the above purpose, the utility model adopts the following technology:
a high-current high-precision constant current source circuit comprises:
a MOS transistor switch unit connected between load RL connected with VCC and GND,
the bias voltage unit is connected to one input end of the gain compression unit and used for providing a direct current voltage to the gain compression unit;
the control voltage unit is connected to the other input end of the gain compression unit and used for providing a control voltage to the gain compression unit;
the output end of the gain compression unit is connected with one input end of the comparison control unit and is used for adding and combining the direct-current voltage and the control voltage, and outputting the single voltage to the comparison control unit after gain compression or gain increase;
the input end of the feedback unit is connected between the MOS tube switch unit and GND, and the output end of the feedback unit is connected with the other input end of the comparison control unit and used for acquiring a sampling voltage from the input end of the feedback unit and transmitting the sampling voltage to the comparison control unit;
and the output end of the comparison control unit is connected with the MOS tube switching unit and is used for comparing the single voltage with the sampling voltage to output a control voltage Vctrl to control the opening or closing of the MOS tube switching unit.
Further, the bias voltage unit is used for selecting a voltage from a preset reference voltage range and converting the voltage into a negative voltage signal with the same absolute value to be transmitted to the gain compression unit as a direct current voltage, and comprises a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a potentiometer RP and an operational amplifier U1, one end of the resistor R1 is connected with the reference voltage VDAC, the other end of the resistor R is connected with one positioning pin of the potentiometer RP, the other positioning pin of the potentiometer RP is connected with the resistor R2, the resistor R2 is connected to the VPR-, an action pin of the potentiometer RP is connected with an inverse phase input end of the operational amplifier U1 through the resistor R3, the same phase input end of the U1 is connected with the VPR-, the resistor R5 is connected between the inverse phase input end and the output end of the operational amplifier U1, and the output end of the operational amplifier U1 is connected with the gain compression unit through the resistor R4.
Further, the control voltage unit is used for converting the output voltage of the preceding-stage DAC into a negative voltage signal with the same absolute value and outputting the negative voltage signal to the gain compression unit as a control voltage, and comprises a resistor R6, a resistor R7, a resistor R8, a resistor R9, a resistor R10, a resistor R11 and an operational amplifier U2, wherein one end of the resistor R6 is connected with the output of the preceding-stage DAC, the other end of the resistor R6 is connected with the inverting input end of the operational amplifier U2, the same input end of the operational amplifier U2 is connected with the resistor R7 and the resistor R9, the resistor R7 is connected with the VPR through the resistor R8, the resistor R9 is connected with the VPR, the resistor R11 is connected between the inverting input end and the output end of the operational amplifier U2, and the output end of the operational amplifier U2 is connected with the gain compression unit through the resistor R10.
Further, the gain compression unit comprises a resistor R12, a resistor R13, a resistor R14, a resistor R15, a resistor R16 and an operational amplifier U3, one end of the resistor R12 is connected with the bias voltage unit and the control voltage unit respectively, the other end of the resistor R12 is connected with the inverting input end of the operational amplifier U3, the non-inverting input end of the operational amplifier U3 is connected with the VPR through the resistor R13, the resistor R15 is connected between the inverting input end and the output end of the operational amplifier U3, the output end of the operational amplifier U3 is connected with one end of the resistor R14, the other end of the resistor R14 is connected with the comparison control unit, and is connected with the VPR through the resistor R16.
Further, the comparison control unit comprises an operational amplifier U4 and a resistor R17, the in-phase input end of the operational amplifier U4 is connected with the output end of the gain compression unit, the reverse-phase input end of the operational amplifier U4 is connected with the output end of the feedback unit, and the output end of the operational amplifier U4 is connected with the MOS tube switch unit through the resistor R17.
Further, the feedback unit comprises a sampling resistor R21, a resistor R20, a resistor R19 and an operational amplifier U5, the sampling resistor R21 is connected between the MOS transistor switch unit and GND through pins 1 and 4, pins 2 of the sampling resistor R21 are connected to the non-inverting input end of the operational amplifier U5, pins 3 are connected with VPR-and the resistor R20, the resistor R20 is connected with DGND, the inverting input end of the operational amplifier U5 is connected with the output end of the operational amplifier U5, and the output end of the operational amplifier U5 is connected with the comparison control unit through the resistor R19.
Further, the MOS tube switching unit comprises one or more MOS tubes Q1 connected in parallel, the S pole of each MOS tube Q1 is connected with a resistor R18, the G pole is connected with the output end of the comparison control unit, the D pole is connected with a load RL, and the resistor R18 is connected to the input end of the feedback unit. Preferably, the MOS transistor switching unit includes a plurality of MOS transistors Q1, for example, 10.
The utility model has the advantages that:
1. compared with the traditional constant current source circuit, the constant current precision is greatly improved, and the control utilization efficiency of the DAC is improved;
2. by utilizing the shunt scheme of parallel connection/array of the switch MOS tube, the maximum constant current capability and the service life of the system are greatly improved, and the use reliability is improved;
3. the circuit is simple and clear, and the constant current source required by self design and matched design can be selected under the limited production cost.
Drawings
Fig. 1 is a constant current source circuit of the prior art.
Fig. 2 is a circuit structure diagram of a large-current high-precision constant current source according to an embodiment of the present application.
Fig. 3 is a circuit configuration diagram of a preferred example of a MOS transistor switching unit according to an embodiment of the present application.
Detailed Description
To make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the following detailed description of the embodiments of the present invention is provided with reference to the accompanying drawings, but the described embodiments of the present invention are some embodiments of the present invention, not all embodiments.
The embodiment of the application discloses a high-current high-precision constant current source circuit, as shown in fig. 2, which comprises an MOS transistor switch unit, a bias voltage unit, a control voltage unit, a gain compression unit, a feedback unit and a comparison control unit.
The MOS tube switch unit is connected between a load RL connected with the VCC and GND, and the bias voltage unit is connected with one input end of the gain compression unit and is used for providing a direct current voltage to the gain compression unit; the control voltage unit is connected to the other input end of the gain compression unit and used for providing a control voltage to the gain compression unit; the output end of the gain compression unit is connected with one input end of the comparison control unit and is used for adding and combining the direct-current voltage and the control voltage, and outputting the single voltage to the comparison control unit after gain compression or gain increase; the input end of the feedback unit is connected between the MOS tube switch unit and GND, and the output end of the feedback unit is connected with the other input end of the comparison control unit and is used for acquiring a sampling voltage from the input end of the feedback unit and transmitting the sampling voltage to the comparison control unit; the output end of the comparison control unit is connected with the MOS tube switch unit and used for comparing the single voltage with the sampling voltage to output a control voltage Vctrl to control the opening or closing of the MOS tube switch unit.
As a more detailed embodiment, the bias voltage unit is configured to select a voltage from a predetermined reference voltage range and convert the voltage into a negative voltage signal with the same absolute value to be transmitted to the gain compression unit as a dc voltage, and optionally, the bias voltage unit may adopt a circuit structure as shown in fig. 2, and include a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a potentiometer RP, and an operational amplifier U1, where one end of the resistor R1 is connected to the reference voltage VDAC, and the other end of the resistor R1 is connected to one positioning pin of the potentiometer RP, the other positioning pin of the potentiometer RP is connected to the resistor R2, the resistor R2 is connected to VPR- (ground of the sampling circuit), the action pin of the potentiometer RP is connected to the inverting input terminal of the operational amplifier U1 through the resistor R3, the non-inverting input terminal of the U1 is connected to VPR-, the resistor R5 is connected between the inverting input terminal and the output terminal of the operational amplifier U1, and the output terminal of the operational amplifier U1 is connected to the gain compression unit through the resistor R4.
As a more detailed embodiment, the control voltage unit is configured to convert the output voltage of the DAC at the previous stage into a negative voltage signal with the same absolute value, and output the negative voltage signal as a control voltage to the gain compression unit, and optionally, a circuit structure as shown in fig. 2 may be adopted, where the circuit structure includes a resistor R6, a resistor R7, a resistor R8, a resistor R9, a resistor R10, a resistor R11, and an operational amplifier U2. The output of preceding stage DAC is connected to resistance R6 one end, and the inverting input end of U2 is put to the other end connection fortune, and U2's the same input end connecting resistance R7 and resistance R9 are put to fortune, and resistance R7 passes through resistance R8 and connects VPR-, resistance R9 connects VPR-, resistance R11 connects between U2's inverting input end and output is put to fortune, and U2's output is put to fortune passes through resistance R10 and connects the gain compression unit.
As a more detailed embodiment, optionally, the gain compression unit adopts a structure as shown in fig. 2, and includes a resistor R12, a resistor R13, a resistor R14, a resistor R15, a resistor R16, and an operational amplifier U3, one end of the resistor R12 is connected to the resistor R4 of the bias voltage unit and the resistor R10 of the control voltage unit, the other end is connected to the inverting input terminal of the operational amplifier U3, the non-inverting input terminal of the operational amplifier U3 is connected to VPR through the resistor R13, the resistor R15 is connected between the inverting input terminal and the output terminal of the operational amplifier U3, the output terminal of the operational amplifier U3 is connected to one end of the resistor R14, the other end of the resistor R14 is connected to the comparison control unit, and is connected to VPR through the resistor R16.
As a more detailed implementation manner, optionally, the comparison control unit adopts a circuit as shown in fig. 2, and includes an operational amplifier U4 and a resistor R17, a non-inverting input terminal of the operational amplifier U4 is connected to an output terminal of the gain compression unit, that is, the other terminal of the resistor R14, an inverting input terminal of the operational amplifier U4 is connected to an output terminal of the feedback unit, and an output terminal of the operational amplifier U4 is connected to the MOS transistor switching unit through the resistor R17.
As a more detailed implementation manner, optionally, the feedback unit adopts a circuit structure as shown in fig. 2, and includes a sampling resistor R21, a resistor R20, a resistor R19, and an operational amplifier U5, where the sampling resistor R21 is connected between the MOS transistor switching unit and GND through its 1 pin and 4 pins, 2 pins of the sampling resistor R21 are connected to the non-inverting input terminal of the operational amplifier U5, 3 pins of the sampling resistor R21 are connected to VPR-and the resistor R20, the resistor R20 is connected to DGND, the inverting input terminal of the operational amplifier U5 is connected to its output terminal, and the output terminal of the operational amplifier U5 is connected to the inverting input terminal of the operational amplifier U4 of the comparison control unit through the resistor R19.
As a more detailed implementation, as shown in fig. 2, the MOS transistor switching unit may optionally include one or more parallel MOS transistors Q1. The G pole of each MOS pipe Q1 is connected to the resistor R17, the D pole is connected to the load RL, and the S pole is connected to the 1 pin of the sampling resistor R21 after being connected with the resistor R18.
When in work:
at the bias voltage, VDAC _5V output by a precision reference chip provides a power supply for the output of the bias voltage, the reference voltage output can be adjusted to be selected within the range of 0V-5V through a potentiometer RP, then the reference voltage is converted into a negative voltage signal with the same absolute value through an inverting operational amplifier U1 (namely an operational amplifier U1), the gain of the operational amplifier U1 is set to be 1, the bias voltage has the function of providing a direct current voltage which is always stably existed, the direct current voltage is transmitted to a rear-stage comparison control unit after being processed through the operational amplifier U1 so as to provide a fixed input voltage for an MOS tube switching unit, the fixed voltage can be adjusted to be just equal to the Vth of an MOS tube Q1 in the MOS tube switching unit through changing the resistance value of the potentiometer RP, and thus the lowest output of the DAC output voltage can be coincided with the starting point of a constant current area of the MOS tube Q1.
At the control voltage, a control voltage is output by the preceding-stage output DAC, and then the control signal is continuously converted into a negative voltage signal with the same absolute value through an inverting proportional operational amplifier (namely, an operational amplifier U2), and the gain of the operational amplifier U2 is also set to be 1.
At the gain compression, an inverse proportion operational amplifier (i.e. an operational amplifier U3) is also used, which has two functions, namely, the voltages (the dc voltage output from the bias voltage and the control voltage output from the control voltage) input by the two parts are added and combined, and then output to the non-inverting input terminal of the operational amplifier U4 of the comparison control unit. Here, the operational amplifier U3 can flexibly adjust gain compression or gain amplification. As the gain calculation formula of the homodromous proportional operational amplifier determines that the amplifier of the type has 1 time of gain at least and is not suitable for a scene needing gain compression, the gain compression is needed at the scene, so the operational amplifier U3 adopts an inverse proportional operational amplifier, the gain setting needs to be set according to the actual situation and is set to be 0.2 time at the scene, and the DAC of 0V-5V is input and compressed to the control voltage range of 1V, so that the output precision of the constant current source is higher.
And at the feedback unit, sampling voltage is acquired through the sampling resistor R21 and is input to the inverse input end of the operational amplifier U4 of the comparison control unit after being gained by the operational amplifier U5.
At the comparison control unit, the operational amplifier U4 compares the voltages at the non-inverting input terminal and the inverting input terminal thereof to generate a signal which is finally used for controlling the MOS transistor Q1 and is a single voltage signal, thereby controlling the MOS transistor switching unit more accurately.
The control precision problem of the constant current source is solved through the embodiment, and compared with the scheme that the switch MOS tube is directly controlled by the DAC output, the control precision is greatly improved.
In order to improve the upper limit of the constant current source and serve as a more detailed implementation manner, optionally, the MOS transistor switching unit adopts a circuit structure as shown in fig. 3, and 10 MOS transistors Q1 are connected in parallel to form a MOS transistor shunt array, specifically, the MOS transistor switching unit includes 10 MOS transistors Q1 connected in parallel, an S pole of each MOS transistor Q1 is connected to one resistor R18, a G pole is connected to an output end of the comparison control unit, a D pole is connected to a load RL, and the resistor R18 is connected to an input end of the feedback unit, specifically, to pin 1 of the sampling resistor R21.
Here, each path of switching MOS transistor Q1 may share a certain current, and it is assumed that the maximum continuous current at which each path of switching MOS transistor Q1 can work well is 0.5A, and then the maximum current at which a constant current source formed by 10 paths of switching MOS transistor arrays can work stably is 5A, in order to eliminate the internal constant current difference of switching MOS transistors Q1 of the same type, there is a matching resistor R18 below each path of switching MOS transistor Q1, for balancing the problem of unbalanced shunting in each shunting path due to the internal difference of switching MOS transistor Q1, which is beneficial to prolonging the use of the whole circuit. Compared with a constant current source circuit of a single switching tube, the constant current capability of large current is greatly improved in the mode of the embodiment.
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and it is apparent that those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if such modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is intended to include such modifications and variations as well.
Claims (8)
1. A high-current high-precision constant current source circuit is characterized by comprising:
a MOS transistor switch unit connected between load RL connected with VCC and GND,
the bias voltage unit is connected to one input end of the gain compression unit and used for providing a direct current voltage to the gain compression unit;
the control voltage unit is connected to the other input end of the gain compression unit and used for providing a control voltage to the gain compression unit;
the output end of the gain compression unit is connected with one input end of the comparison control unit and used for adding and combining the direct-current voltage and the control voltage, and outputting the single voltage to the comparison control unit after gain compression or increase;
the input end of the feedback unit is connected between the MOS tube switch unit and GND, and the output end of the feedback unit is connected with the other input end of the comparison control unit and is used for acquiring a sampling voltage from the input end of the feedback unit and transmitting the sampling voltage to the comparison control unit;
and the output end of the comparison control unit is connected with the MOS tube switching unit and is used for comparing the single voltage with the sampling voltage to output a control voltage Vctrl to control the opening or closing of the MOS tube switching unit.
2. The large-current high-precision constant current source circuit as claimed in claim 1, wherein the bias voltage unit is used for selecting a voltage from a predetermined reference voltage range and converting the voltage into a negative voltage signal with the same absolute value to be transmitted to the gain compression unit as a direct current voltage, and comprises a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a potentiometer RP and an operational amplifier U1, wherein one end of the resistor R1 is connected with the reference voltage VDAC, the other end of the resistor R1 is connected with one positioning pin of the potentiometer RP, the other positioning pin of the potentiometer RP is connected with the resistor R2, the resistor R2 is connected to VPR-, an action pin of the potentiometer RP is connected with an inverting input end of the operational amplifier U1 through the resistor R3, the U1 operational amplifier in-phase input end is connected with the VPR-, the resistor R5 is connected between the inverting input end and the output end of the operational amplifier U1, and the output end of the operational amplifier U1 is connected with the gain compression unit through the resistor R4.
3. The large-current high-precision constant current source circuit as claimed in claim 1, wherein the control voltage unit is configured to convert the output voltage of the preceding stage DAC into a negative voltage signal with the same absolute value and output the negative voltage signal as a control voltage to the gain compression unit, and includes a resistor R6, a resistor R7, a resistor R8, a resistor R9, a resistor R10, a resistor R11, and an operational amplifier U2, wherein one end of the resistor R6 is connected to the output of the preceding stage DAC, the other end of the resistor R6 is connected to the inverting input terminal of the operational amplifier U2, the same input terminal of the operational amplifier U2 is connected to the resistor R7 and the resistor R9, the resistor R7 is connected to VPR through the resistor R8, the resistor R9 is connected to VPR, the resistor R11 is connected between the inverting input terminal and the output terminal of the operational amplifier U2, and the output terminal of the operational amplifier U2 is connected to the gain compression unit through the resistor R10.
4. The large-current high-precision constant current source circuit as claimed in claim 1, wherein the gain compression unit comprises a resistor R12, a resistor R13, a resistor R14, a resistor R15, a resistor R16, and an operational amplifier U3, wherein one end of the resistor R12 is connected to the bias voltage unit and the control voltage unit, the other end of the resistor R12 is connected to the inverting input terminal of the operational amplifier U3, the non-inverting input terminal of the operational amplifier U3 is connected to VPR through the resistor R13, the resistor R15 is connected between the inverting input terminal and the output terminal of the operational amplifier U3, the output terminal of the operational amplifier U3 is connected to one end of the resistor R14, and the other end of the resistor R14 is connected to the comparison control unit and connected to VPR through the resistor R16.
5. The high-current high-precision constant current source circuit as claimed in claim 1, wherein the comparison control unit comprises an operational amplifier U4 and a resistor R17, a non-inverting input terminal of the operational amplifier U4 is connected to the output terminal of the gain compression unit, an inverting input terminal of the operational amplifier U4 is connected to the output terminal of the feedback unit, and an output terminal of the operational amplifier U4 is connected to the MOS transistor switching unit through the resistor R17.
6. The large-current high-precision constant current source circuit according to claim 1, wherein the feedback unit comprises a sampling resistor R21, a resistor R20, a resistor R19, and an operational amplifier U5, the sampling resistor R21 is connected between the MOS transistor switching unit and GND through its 1 pin and 4 pins, 2 pins of the sampling resistor R21 are connected to the non-inverting input terminal of the operational amplifier U5, 3 pins of the sampling resistor R21 are connected to VPR-and the resistor R20, the resistor R20 is connected to DGND, the inverting input terminal of the operational amplifier U5 is connected to the output terminal thereof, and the output terminal of the operational amplifier U5 is connected to the comparison control unit through the resistor R19.
7. The high-current high-precision constant current source circuit according to claim 1, wherein the MOS transistor switching unit comprises one or more parallel MOS transistors Q1, the S pole of each MOS transistor Q1 is connected with a resistor R18, the G pole is connected with the output end of the comparison control unit, the D pole is connected with the load RL, and the resistor R18 is connected with the input end of the feedback unit.
8. The high-current high-precision constant current source circuit according to claim 7, wherein the MOS transistor switching unit comprises 10 MOS transistors Q1.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| CN202221970773.9U CN217689887U (en) | 2022-07-28 | 2022-07-28 | Heavy current high accuracy constant current source circuit |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202221970773.9U CN217689887U (en) | 2022-07-28 | 2022-07-28 | Heavy current high accuracy constant current source circuit |
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| CN217689887U true CN217689887U (en) | 2022-10-28 |
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| CN202221970773.9U Active CN217689887U (en) | 2022-07-28 | 2022-07-28 | Heavy current high accuracy constant current source circuit |
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