CN207817564U - Constant-current control circuit - Google Patents

Abstract

The utility model discloses a constant current control circuit, which performs current induction through a magnetic induction device, provides a feedback voltage signal for a first operational amplifier, provides a constant voltage for a field effect transistor through the first operational amplifier, and uses the drain of the field effect transistor as a laser Provide constant current, provide constant current for the laser, and make the laser work stably. Since the magnetic induction device generates little heat during the induction process, it can accurately induce the magnetic field of the current, so that it can output an accurate feedback voltage signal, and then make the first operational amplifier output an accurate control voltage, so that the field effect transistor outputs an accurate constant current flow to Laser, make sure the laser works stably.

Description

Constant current control circuit

technical field

The utility model relates to the field of laser power supply circuits, in particular to a constant current control circuit.

Background technique

A laser is a device capable of emitting laser light. The laser has a wide range of applications, and its working status affects the application effect. The laser can only work safely and normally under a suitable and stable constant current drive power supply. Excessive changes in the drive current will affect its work efficiency and Stability, the constant current control circuit is a circuit that can ensure the normal operation of the laser under constant current.

At present, in the process of providing constant current to the laser through the constant current control circuit, in order to improve the current stability, the current of the laser can be fed back to the constant current control circuit, that is, the current feedback is carried out through the current feedback detection circuit, usually through the sampling resistor. Current feedback, however, because the larger the current, the greater the heating of the sampling resistor, the greater the temperature drift of the sampling resistor, resulting in inaccurate current feedback results, so that the constant current control circuit cannot accurately provide constant current for the laser.

Utility model content

Based on this, it is necessary to provide a constant current control circuit for the problem that the existing constant current control circuit cannot accurately provide a constant current for the laser.

A constant current control circuit, comprising: a magnetic induction device, a first operational amplifier, a first resistor, a second resistor, and a field effect transistor;

One end of the magnetic induction device is connected to the first power supply, and the other end is connected to the inverting input terminal of the first operational amplifier, and the inverting input terminal of the first operational amplifier is also connected to the first operational amplifier through the first resistor. The output terminal of the amplifier is connected, the non-inverting input terminal of the first operational amplifier is connected to the preset power supply through the second resistor, the output terminal of the first operational amplifier is connected to the gate of the field effect transistor, and the field The source of the effect transistor is grounded through a wire, the drain of the field effect transistor is respectively connected to the second power supply and the laser, and the source and drain of the field effect transistor are connected;

The magnetic induction device senses the magnetic field generated after the wire passes through the current and outputs a corresponding feedback voltage signal, the inverting input terminal of the first operational amplifier receives the feedback voltage signal, and the first operational amplifier receives the feedback voltage signal according to the feedback The voltage signal and the voltage corresponding to the preset power supply output a control voltage, the gate of the field effect transistor receives the control voltage, and the drain of the field effect transistor provides current for the laser.

In one embodiment, the above-mentioned constant current control circuit further includes a second operational amplifier, a third resistor, a fourth resistor, and a fifth resistor, and the other end of the magnetic induction device is connected to the second operational amplifier through the third resistor. The non-inverting input terminal of the second operational amplifier is connected to the ground through the fourth resistor, and the output terminal of the second operational amplifier is connected to the output terminal of the second operational amplifier through the fifth resistor, and the output terminal of the second operational amplifier is connected to the first The inverting input of the second operational amplifier.

In one embodiment, the constant current control circuit further includes a sixth resistor connected between the output terminal of the second operational amplifier and the inverting input terminal of the first operational amplifier.

In one embodiment, the above-mentioned constant current control circuit further includes a seventh resistor, and the other end of the magnetic induction device is grounded through the seventh resistor.

In one embodiment, the constant current control circuit further includes a first capacitor connected between the inverting input terminal of the first operational amplifier and the first resistor.

In one embodiment, the above-mentioned constant current control circuit further includes an eighth resistor and a ninth resistor, the output terminal of the first operational amplifier is connected to the gate through the eighth resistor, and the gate is also connected to the gate through the eighth resistor. The ninth resistor is grounded.

In one embodiment, the laser includes a negative input terminal and a positive input terminal, the constant current control circuit further includes a first diode and a second capacitor, and the drains are respectively connected to the first diode The anode of the second capacitor, one end of the second capacitor, and the negative input end, the second power supply are respectively connected to the cathode of the first diode, the other end of the second capacitor, and the positive input end.

In one embodiment, the constant current control circuit further includes a second diode connected between the drain and the source.

In one embodiment, the constant current control circuit further includes a tenth resistor and a third capacitor, and the non-inverting input terminal of the first operational amplifier is also grounded through the tenth resistor and grounded through the third capacitor.

In one of the embodiments, the magnetic induction device is a Hall sensor.

The above-mentioned constant current control circuit performs current induction through the magnetic induction device, provides a feedback voltage signal for the first operational amplifier, and provides a constant voltage for the field effect transistor through the first operational amplifier, and the drain of the field effect transistor generates a constant current for the laser. Constant current makes the laser work stably. Because the magnetic induction device generates little heat during the induction process, it can accurately induce the magnetic field of the current, so that it can output an accurate feedback voltage signal, and then make the first operational amplifier output an accurate control voltage, so that the field effect transistor outputs an accurate electric constant flow to Laser, make sure the laser works stably. In addition, the magnetic induction device does not need to be connected to the line that provides current for the laser. It only needs to induce the magnetic field generated by the current to output a feedback voltage signal, thereby isolating large currents (in the case of current feedback through the sampling resistor, the sampling resistor needs to be connected as a laser In the power supply line, there is no isolation function, and high current isolation cannot be achieved), so that the constant current control circuit can stably provide a constant current to the laser.

Description of drawings

FIG. 1 is a schematic structural diagram of a constant current control circuit of an embodiment;

FIG. 2 is a schematic structural diagram of a constant current control circuit in another embodiment.

Detailed ways

Referring to FIG. 1 and FIG. 2 , an embodiment of a constant current control circuit is provided, including: a magnetic induction device 110 , a first operational amplifier 120 , a first resistor R1 , a second resistor R2 and a field effect transistor 130 .

One end of the magnetic induction device 110 is connected to the first power supply, and the other end is connected to the inverting input terminal r2 of the first operational amplifier 120, and the inverting input terminal r2 of the first operational amplifier 120 is also connected to the output of the first operational amplifier 120 through the first resistor R1. terminal connection, the non-inverting input terminal r1 of the first operational amplifier 120 is connected to the preset power supply through the second resistor R2, the output terminal of the first operational amplifier 120 is connected to the gate G of the field effect transistor 130, and the source electrode S of the field effect transistor 130 The drain D of the field effect transistor 130 is connected to the second power supply and the laser 140 respectively, and the source S and the drain D of the field effect transistor 130 are connected to the ground through a wire.

When the drain D of the field effect transistor 130 provides current to the laser 140 to make it work, the current flows into the ground through the wire, and a magnetic field will be generated on the wire. The magnetic induction device 110 can be arranged on the above wire to sense the magnetic field generated after the wire is passed through the current. And output the corresponding feedback voltage signal, the inverting input terminal r2 of the first operational amplifier 120 receives the feedback voltage signal, the voltage provided by the preset power supply is input to the non-inverting input terminal r1 of the first operational amplifier 120 after passing through the second resistor R2, The first operational amplifier 120 outputs the control voltage according to the feedback voltage signal and the voltage corresponding to the preset power supply through the second resistor R2, the gate G of the field effect transistor 130 receives the control voltage, and the drain D of the field effect transistor 130 is A laser 140 provides electrical current.

Through the magnetic induction device 110, a feedback voltage signal is output to the magnetic field generated by passing current on the wire, and the feedback voltage signal is transmitted to the inverting input terminal r2 of the first operational amplifier 120. The larger the current, the stronger the magnetic field generated, and the feedback obtained by the induced current The larger the voltage signal is, the feedback voltage signal corresponds to the magnitude of the current input to the laser 140, the inverting input terminal r2 of the first operational amplifier 120 receives the feedback voltage signal, and the non-inverting input terminal receives the voltage provided by the preset power supply, due to the first operation Due to the imaginary short characteristic of the input terminal of the amplifier 120, the voltage at the inverting input terminal is equal to the voltage at the non-inverting input terminal, and the feedback voltage signal of the inverting input terminal r2 of the first operational amplifier 120 is always consistent with the non-inverting input terminal r1 of the first operational amplifier 120. The voltages of the first operational amplifier 120 are the same as the voltages of the non-inverting input terminal r1 and the constant control of the voltage of the inverting input terminal r2. In order to ensure the constant output control voltage, the control voltage is input to the field effect transistor 130, and the current corresponding to the control voltage is output through the drain D. Since the control voltage is constant, the current generated by the drain D is constant, so as to provide a constant voltage for the laser 140. current.

The above-mentioned constant current control circuit performs current induction through the magnetic induction device 110, provides a feedback voltage signal for the first operational amplifier 120, and provides a constant voltage for the field effect transistor 130 through the first operational amplifier 120, which is generated by the drain D of the field effect transistor 130. Constant current, providing a constant current for the laser 140 to make the laser 140 work stably. Since the magnetic induction device 110 generates little heat during the induction process, it can accurately induce the magnetic field of the current, thereby outputting an accurate feedback voltage signal, and then making the first operational amplifier 120 output an accurate control voltage, so that the field effect transistor 130 outputs an accurate voltage. A constant flow to the laser 140 ensures that the laser 140 works stably. In addition, the magnetic induction device 110 does not need to be connected to the circuit that provides current for the laser 140, but only needs to induce the magnetic field generated by the current to output a feedback voltage signal, thereby isolating a large current (in the prior art, when feedback is performed through a sampling resistor, the sampling resistor needs to be connected In the circuit for powering the laser 140, there is no isolation function, and high current isolation cannot be realized), so that the constant current control circuit can stably provide a constant current to the laser 140.

In one example, the field effect transistor 130 is an N-type metal-oxide-semiconductor field effect transistor 130 .

In one example, the first power supply provides a voltage of 3.3v, the second power supply provides a voltage of 36v, the resistance of the first resistor R1 is 5.1 kΩ, and the resistance of the second resistor R2 is 1 kΩ.

In one embodiment, the magnetic induction device 110 may be a Hall sensor. The Hall sensor is small in size and low in cost, which can reduce the size of the entire constant current control circuit and save costs, and can improve sensing efficiency.

In one of the embodiments, the above-mentioned constant current control circuit further includes a second operational amplifier U2, a third resistor R3, a fourth resistor R4 and a fifth resistor R5, and the other end of the magnetic induction device 110 is connected to the second The non-inverting input terminal r3 of the operational amplifier U2, the inverting input terminal r4 of the second operational amplifier U2 are grounded through the fourth resistor R4, and connected to the output terminal t2 of the second operational amplifier U2 through the fifth resistor R5, the second operational amplifier U2 The output terminal t2 of the second operational amplifier U2 is connected to the inverting input terminal r4 of the second operational amplifier.

When the current is small, the magnetic field generated by the current is weak, and the feedback voltage signal output by the magnetic induction device 110 is weak, which needs to be amplified. In this embodiment, through the second operational amplifier U2, the third resistor R3, the fourth The amplifying circuit composed of the resistor R4 and the fifth resistor R5 amplifies the feedback voltage signal, and the amplified feedback voltage signal is input to the inverting input terminal of the first operational amplifier 120 . Specifically, the voltage dropped by the feedback voltage signal through the third resistor R3 is input to the non-inverting input terminal r3 of the second operational amplifier U2, and the voltage at the non-inverting input terminal is amplified by the second operational amplifier U2 and then output. The voltage of the output terminal t2 of the operational amplifier U2 is K times the voltage of the non-inverting input terminal, and the value of K is (R5+R4)/R4, and the corresponding amplification factor can be set by adjusting the size of the resistor R5. In this embodiment, the voltage drop processing is performed on the feedback voltage signal output by the magnetic induction device 110 through the third resistor R3, so as to prevent the current supplied to the laser 140 from being too large due to the feedback voltage signal output by the magnetic induction device 110 being too large.

In one example, the resistance of the third resistor R3 is 1 kΩ, the resistance of the fourth resistor R4 is 1 kΩ, and the resistance of the fifth resistor R5 is 10 kΩ.

In one embodiment, the constant current control circuit further includes a sixth resistor R6 connected between the output terminal t2 of the second operational amplifier U2 and the inverting input terminal r2 of the first operational amplifier 120 .

A sixth resistor R6 is set between the output terminal t2 of the second operational amplifier U2 and the inverting input terminal r2 of the first operational amplifier 120 for transition, so as to prevent the transition amplification of the second operational amplifier U2 from causing the voltage at the output terminal to be too high, the sixth The voltage dropped by the resistor R6 from the output terminal t2 of the second operational amplifier U2 is output to the inverting input terminal r2 of the first operational amplifier 120 .

In an example, the resistance of the sixth resistor R6 is 750Ω.

In one embodiment, the above constant current control circuit further includes a seventh resistor R7, and the other end of the magnetic induction device 110 is grounded through the seventh resistor R7.

When the current is large, the feedback voltage signal output by the magnetic induction device 110 may be too high, which may cause the current flowing through the third resistor R3 to be too large, so that the other end of the magnetic induction device 110 is also grounded through the seventh resistor R7, and passed through the seventh resistor R3. Resistor R7 performs shunting to ensure the safety and stability of the entire circuit.

In an example, the resistance of the seventh resistor R7 is 750Ω.

In one embodiment, the constant current control circuit further includes a first capacitor C1 connected between the inverting input terminal r2 of the first operational amplifier 120 and the first resistor R1.

During the process of outputting the feedback voltage signal output by the magnetic induction device 110 to the inverting input terminal r2 of the first operational amplifier 120 through the third resistor R3, the second amplifier and the sixth resistor R6, it may be interfered by factors such as lines, causing the input to The voltage at the inverting input terminal r2 of the first operational amplifier 120 is noisy, and a first capacitor C1 is provided between the inverting input terminal r2 of the first operational amplifier 120 and the first resistor R1 to filter noise and increase the voltage signal accuracy. In an example, the capacitance of the first capacitor C1 is 560 picofarads.

In one embodiment, the above-mentioned constant current control circuit further includes an eighth resistor R8 and a ninth resistor R9, the output terminal of the first operational amplifier 120 is connected to the gate G through the eighth resistor R8, and the gate G is also connected to the gate G through the ninth resistor R8. Resistor R9 is grounded.

Transition between the first operational amplifier 120 and the field effect transistor 130 through the eighth resistor R8 prevents the voltage of the output terminal of the first operational amplifier 120 from being too high and causing the current generated by the field effect transistor 130 to be too high, resulting in unstable operation of the laser 140 . The voltage at the output end of the first operational amplifier 120 is stepped down through the eighth resistor R8 and then output to the gate G. In addition, a ninth resistor R9 is also provided, and the gate G is grounded through the ninth resistor R9 to ensure that the entire circuit security and stability.

In one example, the resistance of the eighth resistor R8 is 22 ohms, and the resistance of the ninth resistor R9 is 10 kohms.

In one embodiment, the laser 140 includes a negative input terminal 141 and a positive input terminal 142, the constant current control circuit further includes a first diode D1 and a second capacitor C2, and the drains D are respectively connected to the terminals of the first diode D1. The anode, one terminal of the second capacitor C2 and the negative input terminal 141 , and the second power supply are respectively connected to the cathode of the first diode D1 , the other terminal of the second capacitor C2 and the positive input terminal 142 .

The drain D is connected to the second power supply through the first diode D1. After the gate G receives the voltage output by the eighth resistor R8, a current is generated on the drain D, and the drain D has a drain voltage. Since the drain D is still It is connected with the negative input terminal 141 so as to provide a voltage for the negative input terminal 141 . In addition, the second power supply is connected to the anode input terminal 142, and the second power supply provides voltage to the anode of the laser 140, and is filtered by the second capacitor C2 to remove interference noise. In this way, a voltage difference can be generated between the positive input terminal 142 and the negative input terminal 141 of the laser to power the laser. In one example, the model of the first diode D1 is STT3R06U, the capacitance of the second capacitor C2 is 0.01 microfarads, and the maximum voltage it can withstand is 100v.

In one embodiment, the constant current control circuit further includes a second diode D2 connected between the drain D and the source S.

To ensure safe and stable operation of the field effect transistor 130 , a second diode D2 is connected between the drain D and the source S.

In one of the embodiments, the above-mentioned constant current control circuit further includes a tenth resistor R10 and a third capacitor C3, the non-inverting input terminal r1 of the first operational amplifier 120 is grounded through the tenth resistor R10, and the third capacitor C3 grounded.

Since the voltage output from the preset power supply may have interference, after being stepped down by the second resistor R2, it is also filtered by the third capacitor C3 to remove the interference noise. In addition, the non-inverting input terminal is also grounded through the tenth resistor R10, which can shunt the output current from the second resistor R2 and improve the safety and stability of the entire circuit.

In an example, the capacitance of the third capacitor C3 is 200 picofarads, and the resistance of the tenth resistor R10 is 300 ohms.

In one embodiment, the above-mentioned constant current control circuit further includes an eleventh resistor R11 and a fourth capacitor C4, one end of the first operational amplifier 120 is grounded, and the other end is connected to the third power supply through the eleventh resistor R11, and through The fourth capacitor C4 is grounded.

The third power supply supplies power to the first operational amplifier 120 to make it work normally, and the voltage provided by the third power supply is subjected to voltage drop processing through the eleventh resistor R11 to prevent the voltage from being too high from affecting the normal operation of the first operational amplifier 120. The fourth capacitor C4 performs filtering. In one example, the third power supply provides a voltage of 8v.

In one example, the capacitance of the fourth capacitor C4 is 4.7 microfarads, and the maximum voltage it can withstand is 16v.

The technical features of the above embodiments can be combined arbitrarily. To make the description concise, all possible combinations of the technical features in the above embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, they should be It is considered to be within the range described in this specification.

The above embodiments only express several embodiments of the present utility model, and the description thereof is relatively specific and detailed, but it should not be understood as limiting the patent scope of the present utility model. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the scope of protection of the utility model patent should be based on the appended claims.

Claims (10)

1. A constant current control circuit, characterized in that it comprises: a magnetic induction device, a first operational amplifier, a first resistor, a second resistor and a field effect transistor; One end of the magnetic induction device is connected to the first power supply, and the other end is connected to the inverting input terminal of the first operational amplifier, and the inverting input terminal of the first operational amplifier is also connected to the first operational amplifier through the first resistor. The output terminal of the amplifier is connected, the non-inverting input terminal of the first operational amplifier is connected to the preset power supply through the second resistor, the output terminal of the first operational amplifier is connected to the gate of the field effect transistor, and the field The source of the effect transistor is grounded through a wire, the drain of the field effect transistor is respectively connected to the second power supply and the laser, and the source and drain of the field effect transistor are connected; The magnetic induction device senses the magnetic field generated after the wire passes through the current and outputs a corresponding feedback voltage signal, the inverting input terminal of the first operational amplifier receives the feedback voltage signal, and the first operational amplifier receives the feedback voltage signal according to the feedback The voltage signal and the voltage corresponding to the preset power supply output a control voltage, the gate of the field effect transistor receives the control voltage, and the drain of the field effect transistor provides current for the laser. 2. The constant current control circuit according to claim 1, further comprising a second operational amplifier, a third resistor, a fourth resistor and a fifth resistor, the other end of the magnetic induction device is connected to the The non-inverting input terminal of the second operational amplifier, the inverting input terminal of the second operational amplifier is grounded through the fourth resistor, and the output terminal of the second operational amplifier is connected through the fifth resistor, the output of the second operational amplifier The terminal is connected to the inverting input terminal of the second operational amplifier. 3. The constant current control circuit according to claim 2, further comprising a sixth resistor connected between the output terminal of the second operational amplifier and the inverting input terminal of the first operational amplifier. 4. The constant current control circuit according to claim 2, further comprising a seventh resistor, and the other end of the magnetic induction device is grounded through the seventh resistor. 5. The constant current control circuit according to claim 1, further comprising a first capacitor connected between the inverting input terminal of the first operational amplifier and the first resistor. 6. The constant current control circuit according to claim 1, further comprising an eighth resistor and a ninth resistor, the output terminal of the first operational amplifier is connected to the gate through the eighth resistor, so The grid is also grounded through the ninth resistor. 7. The constant current control circuit according to claim 1, wherein the laser comprises a positive input terminal and a negative input terminal, the constant current control circuit further comprises a first diode and a second capacitor, the The drains are respectively connected to the positive pole of the first diode, one end of the second capacitor and the negative input terminal, and the second power supply is respectively connected to the negative pole of the first diode, the second capacitor the other end and the positive input. 8. The constant current control circuit according to claim 1, further comprising a second diode connected between the drain and the source. 9. The constant current control circuit according to claim 1, further comprising a tenth resistor and a third capacitor, the non-inverting input terminal of the first operational amplifier is also grounded through the tenth resistor, and is connected to the ground through the third capacitor. capacitor to ground. 10. The constant current control circuit according to any one of claims 1-9, wherein the magnetic induction device is a Hall sensor.