CN116009636A - A voltage-controlled constant current source drive circuit - Google Patents

Abstract

The application discloses a voltage-controlled constant current source drive circuit. The circuit comprises: a comparison output circuit for outputting a first pulse signal according to a comparison result of the first input signal and the second input signal; a switching circuit for turning on or off according to the level of the first pulse signal; the current sampling circuit is used for generating a first current and outputting a first voltage according to the on or off frequency of the switching circuit; the voltage amplifying circuit is used for amplifying the first voltage to generate a second voltage output; the digital-to-analog conversion circuit is used for generating analog voltage signal output; and the feedback circuit is used for generating a differential mode voltage of the analog voltage signal and the second voltage, and integrating the differential mode voltage to generate a second input signal. The voltage-controlled constant current source driving circuit improves error precision, expands output power, and solves the technical problems that when the conventional constant current source circuit is applied to a low-voltage constant current occasion, error is large and constant current output by the conventional constant current source circuit is small.

Description

A voltage-controlled constant current source drive circuit

technical field

The application belongs to the technical field of constant current source circuits, and relates to a voltage-controlled constant current source driving circuit.

Background technique

The existing constant current source circuit usually includes a constant current source circuit composed of transistors and a constant current source circuit composed of integrated operational amplifiers. Among them, the existing constant current source circuit composed of transistors has The equivalent resistance between electrodes is more than tens of kiloohms, so when the constant current source circuit is applied to low-voltage constant current, it will cause relatively large errors; and the constant current source circuit composed of integrated operational amplifiers is affected by the operation in the circuit. The limitation of the saturation voltage and current of the amplifier prevents the form current of the operational amplifier circuit of the constant current source circuit from being too large, which eventually leads to a small constant current output by the circuit.

Contents of the invention

In view of the above problems, the present application provides a voltage-controlled constant current source drive circuit to solve the above technical problems.

In order to solve the problems of the technologies described above, the technical scheme of the present application is as follows:

The application provides a voltage-controlled constant current source drive circuit, including:

A comparison output circuit, configured to receive a first input signal and a second input signal, and output a first pulse signal according to a comparison result between the first input signal and the second input signal;

a switch circuit, configured to receive the first pulse signal, and turn on or off according to the level of the first pulse signal;

a current sampling circuit, configured to generate a first current and output a first voltage according to the frequency at which the switch circuit is turned on or off;

a voltage amplifying circuit, configured to receive the first voltage, and amplify the first voltage to generate a second voltage output;

A digital-to-analog conversion circuit, configured to generate an output analog voltage signal, and the analog voltage signal is used to control the magnitude of the first current;

The feedback circuit is configured to receive an analog voltage signal and the second voltage, generate a differential mode voltage of the analog voltage signal and the second voltage, and perform integral processing on the differential mode voltage to generate a second input signal.

Further, the voltage-controlled constant current source drive circuit also includes an isolated power supply module;

The input terminal of the isolated gate driver is connected to the comparison output circuit, and the output terminal of the isolated gate driver is connected to the switch circuit for connecting the first power supply connected to the comparison output circuit to the comparison output circuit. The second power supply of the switch circuit is isolated, and the switch circuit is driven to be turned on or off according to the first pulse signal output by the comparison output circuit.

Further, the voltage-controlled constant current source driving circuit also includes a first chip and a sawtooth wave generating circuit;

The first chip is used to output a square wave with a set frequency;

The sawtooth wave generating circuit is configured to receive the square wave and output the first input signal having the same frequency as the square wave.

Further, the sawtooth wave generating circuit includes a first triode, a first capacitor, a first resistor and a clamping diode;

The base of the first triode is connected to the first chip, and the emitter of the first triode is respectively connected to the first end of the first capacitor and the anode of the clamping diode, so The collector of the first triode is respectively connected to the second end of the first capacitor, the first end of the first resistor, and the cathode of the clamping diode to the comparison output circuit, and the first The first terminal of the capacitor is also used for grounding, and the second terminal of the first resistor is used for connecting to the first power supply.

Further, the comparison output circuit includes a first comparator;

The non-inverting input terminal of the first comparator is connected to the sawtooth wave generating circuit, the inverting input terminal of the first comparator is connected to the feedback circuit, and the output terminal of the first comparator is connected to the Isolated gate driver connection.

Further, the switch circuit includes a first MOS transistor;

The gate of the first MOS transistor is connected to the isolated gate driver, the source of the first MOS transistor is connected to the current sampling circuit, and the drain of the first MOS transistor is used to connect to the second power supply.

Further, the current sampling circuit includes a freewheeling diode, a first inductor, a second capacitor, a second resistor and a sampling resistor;

The cathode of the freewheeling diode is respectively connected to the switch circuit and the first end of the first inductance, the anode of the freewheeling diode is used for grounding, and the second end of the first inductance is respectively connected to the first end of the first inductance. The first end of the second capacitor is connected to the first end of the second resistor, and the second end of the second capacitor and the second end of the second resistor are both connected to the first end of the sampling resistor, so The first end of the sampling resistor is also connected to the voltage amplifying circuit, and the second end of the sampling resistor is used for grounding.

Further, the voltage amplifying circuit includes a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor and a first operational amplifier;

The two ends of the third resistor are respectively connected to the non-inverting input terminal of the first operational amplifier and the first end of the fourth resistor, and the two ends of the fifth resistor are respectively connected to the first terminal of the first operational amplifier. The inverting input terminal is connected to the second terminal of the fourth resistor, and the second terminal of the fourth resistor is also connected to the current sampling circuit;

The first end of the sixth resistor is connected to the non-inverting input end of the first operational amplifier, and the second end of the sixth resistor is used for grounding;

Both ends of the seventh resistor are respectively connected to the inverting input terminal of the first operational amplifier and the output terminal of the first operational amplifier, and the output terminal of the operational amplifier is also connected to the feedback circuit.

Further, the feedback circuit includes a second operational amplifier, an eighth resistor, a ninth resistor, and a third capacitor;

The non-inverting input terminal of the second operational amplifier is connected to the voltage amplifying circuit, the inverting input terminal of the second operational amplifier is respectively connected to the eighth resistor and the second capacitor, and the second operational amplifier The output end of the amplifier is connected to the ninth resistor, and the ninth resistor is also connected to the second capacitor, and the eighth resistor is also used to connect to the digital-to-analog conversion circuit.

Further, the digital-to-analog conversion circuit includes a digital-to-analog converter, and the digital-to-analog converter is connected to the feedback circuit.

Compared with the prior art, the beneficial effects of the present application:

The voltage-controlled constant current source drive circuit provided by this application controls the on and off of the switch circuit by comparing the pulse signal output by the output circuit. When the frequency of the switch circuit on or off is constant, the current sampling circuit generates the first The current and the error voltage in the circuit, that is, the first voltage, amplifies the error voltage through the voltage amplifier circuit to generate a second voltage and input it to the feedback circuit, and the feedback circuit receives the analog voltage signal and the second voltage to eliminate the error voltage. When the voltage signal is equal to the second voltage signal, the circuit reaches a balanced state. The voltage-controlled constant-current source drive circuit provided by the application improves the error accuracy of the circuit. Further, the voltage-controlled constant-current source drive circuit provided by the application is provided with an isolated gate driver that will be connected to the first power supply and the connection of the comparison output circuit. The second power supply isolation of the switching circuit greatly expands the output power of the current sampling circuit, and solves the problem of large errors when the existing constant current source circuit is applied to low-voltage constant current occasions and the constant current output of the existing constant current source circuit. small problem; and the voltage-controlled constant current source drive circuit provided by the embodiment of the present application has a fast settling time from feedback to balance, has a fast response function, and has high output accuracy. The output is continuously adjustable within a certain range, and can be adapted to multiple requirements for a constant current circuit.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application or in the prior art, the accompanying drawings that need to be used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are only for the application. For some embodiments, those of ordinary skill in the art can also obtain other drawings based on these drawings without any creative effort.

FIG. 1 is a block diagram of a voltage-controlled constant current source drive circuit provided by an embodiment of the present application.

FIG. 2 is a schematic structural diagram of a voltage-controlled constant current source driving circuit provided by an embodiment of the present application.

Detailed ways

The technical solutions in the embodiments of the present application are clearly and completely described below in conjunction with the drawings in the embodiments of the present application. It should be clear that the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the scope of protection of this application.

The terms "first", "second" and the like in the specification and claims of the present application are used to distinguish similar objects, and are not used to describe a specific sequence or sequence. It is to be understood that the data so used are interchangeable under appropriate circumstances such that the embodiments of the application can be practiced in sequences other than those illustrated or described herein.

Fig. 1 is a module block diagram of the voltage-controlled constant current source drive circuit provided by the embodiment of the present application. As shown in Fig. 1, the voltage-controlled constant current source drive circuit provided by the embodiment of the present application includes a comparison output circuit 101, a switch circuit 102, a current Sampling circuit 103 , voltage amplifying circuit 104 , digital-to-analog conversion circuit 108 and feedback circuit 105 .

The comparison output circuit 101 is used to receive the first input signal and the second input signal, and output the first pulse signal according to the comparison result of the first input signal and the second input signal; wherein, the first input signal is a sawtooth wave, and the second input signal Outputted by the feedback circuit 105, the first pulse signal is a PWM wave (Pulsewidthmodulation, pulse width modulation) generated after the comparison between the first input signal and the second input signal.

In some embodiments, as shown in FIG. 1 , the voltage-controlled constant current source drive circuit provided by the embodiment of the present application further includes a first chip 106 and a sawtooth wave generating circuit 107, and the first chip 106 is used to output a set frequency. wave, that is, the frequency of the square wave output by the first chip 106 can be set according to the needs of circuit designers, and the frequency of the square wave is the switching period of the voltage-controlled constant current source drive circuit; the sawtooth wave generating circuit 107 is used for receiving wave, and output a sawtooth wave with the same frequency as the square wave, that is, the first input signal.

It should be clear that in the voltage-controlled constant current source driving circuit provided in the embodiment of the present application, the first input signal is not limited to be generated by the first chip 106 and the sawtooth wave generating circuit 107, and can also be generated by other The first chip 106 and the sawtooth wave generating circuit 107 are replaced by the same circuits.

In some embodiments, as shown in FIG. 1 , the voltage-controlled constant current source driving circuit provided by the embodiment of the present application further includes an isolated gate driver 108, and the input terminal and the output terminal of the isolated gate driver 108 are respectively connected to the comparison output The circuit 101 is connected to the switch circuit 102, and is used to isolate the first power supply VCC connected to the comparison output circuit from the second power supply VDD connected to the switch circuit, and drive the switch circuit to be turned on or off according to the first pulse signal, wherein the connection to the comparison output circuit The first power supply VCC of the circuit is a small power supply of the control stage, and the second power supply VDD connected to the switch circuit is a large power supply of the power stage.

The switch circuit 102 is used to receive the first pulse signal output by the comparison output circuit 101, and turn on or off according to the level of the first pulse signal; the first pulse signal is a PWM wave modulation signal, and the switch circuit 102102 receives the first pulse signal The signal is turned on when the signal is at a high level, and is turned off when the first received pulse signal is at a low level; The switch circuit 102 can also be turned on at a low level and turned off at a high level by redesigning the switch circuit 102 .

The current sampling circuit 103 is used to generate a first current and output a first voltage according to the frequency at which the switch circuit 102 is turned on or off; the first current is the constant current provided by the voltage-controlled constant current source driving circuit provided in the embodiment of the present application, The first voltage is the error voltage of the circuit.

The voltage amplifying circuit 104 is used for receiving the first voltage, amplifying the first voltage to generate a second voltage and outputting it to the feedback circuit 105 .

The feedback circuit 105 is used to receive the analog voltage signal and the second voltage, generate the differential mode voltage of the analog voltage signal and the second voltage, and perform integral processing on the differential mode voltage to generate the second input signal, and the feedback circuit 105 is a PID integral converter , used to eliminate the error voltage in the circuit. When the voltage-controlled constant current source driving circuit provided by the embodiment of the present application is in the initial state, the feedback circuit 105 only receives the analog voltage signal.

Wherein, the analog voltage signal is generated by the digital-to-analog conversion circuit 108 , and circuit designers or application personnel determine the required constant current value by setting the value of the analog voltage signal.

FIG. 2 is a schematic structural diagram of a voltage-controlled constant current source drive circuit provided by an embodiment of the present application. As shown in FIG. 2, in some embodiments, as shown in FIG. 2, the sawtooth wave generating circuit 107 includes a first triode Q1 , a first capacitor C1, a first resistor R1 and a clamping diode D1.

The base of the first triode Q1 is connected to the first chip 106, the emitter of the first triode Q1 is respectively connected to the first end of the first capacitor C1 and the anode of the clamping diode D1, and the first triode Q1 The collector of the first capacitor C1 is connected to the second end of the first capacitor C1, the first end of the first resistor R1, the cathode of the clamping diode D1 is connected to the comparison output circuit 101, and the first end of the first capacitor C1 is also used for grounding , the second end of the first resistor R1 is used to connect to the first power supply.

The sawtooth wave generating circuit 107 receives the square wave signal generated by the first chip 106 to control the turn-on and turn-off of the first triode Q1, and forms a circuit with the same frequency as the square wave signal by charging and discharging the first resistor R1 and the first capacitor C1. Sawtooth wave signal; when the first transistor Q1 is turned off, the power supply charges the first capacitor C1 through the first resistor R1, and the voltage of the first capacitor C1 slowly rises. When the first transistor Q1 is turned on, it is quite For a wire, the charge of the first capacitor C1 is rapidly discharged, and its voltage drops nearly linearly, forming a sawtooth wave.

The comparison output circuit 101 includes a first comparator A1, the non-inverting input terminal of the first comparator A1 is connected with the sawtooth wave generation circuit 107, and is used to receive the first input signal output by the sawtooth wave generation circuit 107, the first comparator A1 The inverting input terminal is connected to the feedback circuit 105 for receiving the second input signal output by the feedback circuit 105, the output terminal of the first comparator A1 is connected to the isolated gate driver 108, and the first The pulse signal is output to the switch circuit 102 to control the switch circuit 102 to be turned on or off; it should be clear that, as common knowledge in the art, the comparator also includes a non-inverting input terminal, an inverting input terminal and an output terminal, and Positive voltage terminal and negative voltage terminal, the positive voltage terminal is used to connect to positive voltage, and the negative voltage terminal is used to connect to negative voltage or ground. In the embodiment of this application, the positive voltage terminal of the first comparator A1 is used to connect to the first power supply VCC , The negative voltage terminal is used for grounding.

The switch circuit 102 includes a first MOS transistor Q2, the gate of the first MOS transistor Q2 is connected to the isolated gate driver 108, and is used to receive the first pulse signal output by the comparison output circuit through the isolated gate driver 108, and the first MOS transistor Q2 The source of the transistor Q2 is connected to the current sampling circuit 103, and the drain of the first MOS transistor Q2 is used to connect to the second power supply VDD; it should be clear that the embodiment of the present application sets the N-channel MOS transistor as a circuit switch, but through the circuit design, It is still possible to set the P communication MOS tube as a circuit switch.

The current sampling circuit 103 includes a freewheeling diode D2, a first inductor L1, a second capacitor C2, a second resistor R2 and a sampling resistor Rm.

The cathode of the freewheeling diode D2 is respectively connected to the switch circuit 102 and the first end of the first inductor L1, the anode of the freewheeling diode D2 is used for grounding, and the second end of the first inductor L1 is respectively connected to the first end of the second capacitor C2 It is connected to the first end of the second resistor R2, the second end of the second capacitor C2 and the second end of the second resistor R2 are connected to the first end of the sampling resistor Rm, and the first end of the sampling resistor Rm is also connected to the voltage amplifier The circuit 104 is connected, and the second end of the sampling resistor Rm is used for grounding.

In the voltage-controlled constant current source driving circuit provided in the embodiment of the present application, when the first pulse signal is at a low level, the first MOS transistor Q2 is turned off, and at this time, the first inductance L1 of the current sampling circuit 103 passes through the second resistor R2 and the sampling resistor Rm is then grounded, and flows back to the first end of the first inductor L1 through the freewheeling diode D2. When the frequency of the first MOS transistor Q2 being turned on or off and the pulse width of the first pulse signal are set properly, the current sampling circuit 103 is It can output a constant current value, which is the first circuit. At the same time, when the first current flows through the sampling resistor Rm, a sampling voltage value, that is, the first voltage, will be formed on the sampling resistor Rm, and the first voltage is the error voltage.

The voltage amplifying circuit 104 includes a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7 and a first operational amplifier W1.

The two ends of the third resistor R3 are respectively connected to the non-inverting input terminal of the first operational amplifier W1 and the first terminal of the fourth resistor R4, and the two ends of the fifth resistor R5 are respectively connected to the inverting input terminal of the first operational amplifier W1 and the first terminal of the fourth resistor R4. The second end of the fourth resistor R4 is connected, and the second end of the fourth resistor R4 is also connected to the current sampling circuit 103 .

A first end of the sixth resistor R6 is connected to the non-inverting input end of the first operational amplifier W1, and a second end of the sixth resistor R6 is used for grounding.

Both ends of the seventh resistor R7 are respectively connected to the inverting input terminal of the first operational amplifier W1 and the output terminal of the first operational amplifier W1 , and the output terminal of the operational amplifier is also connected to the feedback circuit 105 .

The feedback circuit 105 includes a second operational amplifier W2, an eighth resistor R8, a ninth resistor R9 and a third capacitor C3.

The non-inverting input terminal of the second operational amplifier W2 is connected to the voltage amplifying circuit 104, the inverting input terminal of the second operational amplifier W2 is respectively connected to the eighth resistor R8 and the second capacitor C2, and the output terminal of the second operational amplifier W2 is connected to the first capacitor C2. Nine resistors R9 are connected, and the ninth resistor R9 is also connected to the second capacitor C2, and the eighth resistor R8 is also used to connect to the digital-to-analog conversion circuit 108 .

The voltage amplifying circuit 104 amplifies the first voltage and outputs it to the feedback circuit 105. The inverting input terminal of the feedback circuit 105 receives the analog voltage signal, which is a differential mode voltage with the first voltage. The feedback circuit 105 is a PID integrating loop. When the first voltage and When the analog voltage signals are equal, that is, when the circuit is balanced, the second input signal output by the feedback circuit 105 will be a constant value. The pulse signal is also determined, and the first current output by the circuit is constant at this time.

It should be clear that, as common knowledge in the field, the operational amplifier includes, in addition to the non-inverting input terminal, the inverting input terminal and the output terminal, it also includes a positive voltage terminal and a negative voltage terminal, and the positive voltage terminal is used to connect to a positive voltage. The negative voltage terminal is used to connect to a negative voltage or ground. In the embodiment of the present application, the positive voltage terminal of the first operational amplifier W1 and the second operational amplifier W2 is used to connect to the first power supply VCC, and the negative voltage terminal is used to be grounded.

Wherein, the analog voltage signal is generated by the digital-to-analog conversion circuit 108 , and the digital-to-analog conversion circuit 108 includes a digital-to-analog converter, which converts the digital voltage signal to be converted into an analog voltage signal and outputs it to the feedback circuit 105 .

In the voltage-controlled constant current source driving circuit provided by the embodiment of the present application, a first inductor is set in the current sampling circuit to balance the storage current, and the error voltage in the circuit is a relatively low voltage floating between the low potential of the second resistor in the current sampling circuit and the ground. Small potential; even if the current is a hundred amperes, it can be directly connected to the feedback circuit after passing through the voltage amplification circuit through the small potential, which solves the problem that the operational amplifier cannot output large current due to the limitation of saturation voltage and current, and broadens the constant current source drive The output power of the circuit solves the problem that the existing constant current source circuit has a large error when it is applied to a low-voltage constant current occasion and the problem that the constant current output by the existing constant current source circuit is small; and the voltage-controlled constant current provided by the embodiment of the application The current source drive circuit has a fast establishment time from feedback to balance, has a fast response function, and has high output precision. The output can be continuously adjusted within a certain range, and can adapt to the requirements of various constant current circuits.

The above content is a further detailed description of the present application in conjunction with specific implementation modes, and it cannot be considered that the specific implementation of the present application is limited to these descriptions. For those of ordinary skill in the technical field to which this application belongs, some simple deduction or substitutions can be made without departing from the concept of this application, which should be regarded as the protection scope of this application.

Claims (10)

1. A voltage controlled constant current source driving circuit, comprising:

the comparison output circuit is used for receiving a first input signal and a second input signal and outputting a first pulse signal according to the comparison result of the first input signal and the second input signal;

the switching circuit is used for receiving the first pulse signal and is switched on or off according to the level of the first pulse signal;

the current sampling circuit is used for generating a first current and outputting a first voltage according to the on-off frequency of the switching circuit;

the voltage amplifying circuit is used for receiving the first voltage, amplifying the first voltage and then generating a second voltage output;

the digital-to-analog conversion circuit is used for generating an analog voltage signal output, and the analog voltage signal is used for controlling the magnitude of the first current;

and the feedback circuit is used for receiving the analog voltage signal and the second voltage, generating a differential mode voltage of the analog voltage signal and the second voltage, and integrating the differential mode voltage to generate a second input signal.

2. The voltage controlled constant current source drive circuit according to claim 1, further comprising an isolated gate driver;

the input end of the isolated gate driver is connected with the comparison output circuit, the output end of the isolated gate driver is connected with the switch circuit, and the isolated gate driver is used for isolating a first power supply connected with the comparison output circuit from a second power supply connected with the switch circuit and driving the switch circuit to be turned on or off according to a first pulse signal output by the comparison output circuit.

3. The voltage controlled constant current source driving circuit according to claim 2, further comprising a first chip and a sawtooth wave generating circuit;

the first chip is used for outputting square waves with set frequency;

the sawtooth wave generating circuit is used for receiving the square wave and outputting the first input signal with the same frequency as the square wave.

4. The voltage controlled constant current source driving circuit according to claim 3, wherein the sawtooth wave generating circuit comprises a first triode, a first capacitor, a first resistor and a clamping diode;

the base of the first triode is connected with the first chip, the emitter of the first triode is connected with the first end of the first capacitor and the anode of the clamping diode respectively, the collector of the first triode is connected with the second end of the first capacitor, the first end of the first resistor, the cathode of the clamping diode and the comparison output circuit respectively, the first end of the first capacitor is further connected with the ground, and the second end of the first resistor is connected with a first power supply.

5. The voltage controlled constant current source drive circuit according to claim 3, wherein said comparison output circuit comprises a first comparator;

the non-inverting input end of the first comparator is connected with the sawtooth wave generating circuit, the inverting input end of the first comparator is connected with the feedback circuit, and the output end of the first comparator is connected with the isolated gate driver.

6. The voltage controlled constant current source driving circuit according to claim 3, wherein the switching circuit comprises a first MOS transistor;

the grid electrode of the first MOS tube is connected with the isolated grid electrode driver, the source electrode of the first MOS tube is connected with the current sampling circuit, and the drain electrode of the first MOS tube is used for being connected with a second power supply.

7. The voltage controlled constant current source drive circuit according to claim 3, wherein the current sampling circuit comprises a freewheeling diode, a first inductor, a second capacitor, a second resistor, and a sampling resistor;

the cathode of the free-wheeling diode is connected with the switch circuit and the first end of the first inductor respectively, the anode of the free-wheeling diode is used for being grounded, the second end of the first inductor is connected with the first end of the second capacitor and the first end of the second resistor respectively, the second end of the second capacitor and the second end of the second resistor are connected with the first end of the sampling resistor, the first end of the sampling resistor is also connected with the voltage amplifying circuit, and the second end of the sampling resistor is used for being grounded.

8. The voltage controlled constant current source driving circuit according to claim 3, wherein the voltage amplifying circuit comprises a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, and a first operational amplifier;

the two ends of the third resistor are respectively connected with the non-inverting input end of the first operational amplifier and the first end of the fourth resistor, the two ends of the fifth resistor are respectively connected with the inverting input end of the first operational amplifier and the second end of the fourth resistor, and the second end of the fourth resistor is also connected with the current sampling circuit;

the first end of the sixth resistor is connected with the non-inverting input end of the first operational amplifier, and the second end of the sixth resistor is used for being grounded;

and two ends of the seventh resistor are respectively connected with the inverting input end of the first operational amplifier and the output end of the first operational amplifier, and the output end of the operational amplifier is also connected with the feedback circuit.

9. The voltage controlled constant current source drive circuit according to claim 3, wherein the feedback circuit comprises a second operational amplifier, an eighth resistor, a ninth resistor, and a third capacitor;

the non-inverting input end of the second operational amplifier is connected with the voltage amplifying circuit, the inverting input end of the second operational amplifier is respectively connected with the eighth resistor and the second capacitor, the output end of the second operational amplifier is connected with the ninth resistor, the ninth resistor is also connected with the second capacitor, and the eighth resistor is also used for being connected with the digital-to-analog conversion circuit.

10. The voltage controlled constant current source drive circuit according to claim 3, wherein said digital-to-analog conversion circuit comprises a digital-to-analog converter, said digital-to-analog converter being coupled to said feedback circuit.

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