High-precision high-power constant current source

Abstract

The utility model relates to the technical field of laser testing, and discloses a high-precision high-power constant current source, which comprises a current control circuit, a switching circuit and a feedback circuit, and is characterized in that the current control circuit can generate a control voltage according to user requirements and can compare a voltage signal fed back by the feedback circuit with the control voltage; the control circuit is connected with the load and outputs the control signal to the switching circuit, and the control signal can control the switching-on or switching-off of the switching circuit, that is, the power supply voltage corresponding to the power supply current of the load can change along with the control voltage by controlling the switching-on time and the switching-off time of the switching circuit, so that accurate control of the power supply current is realized.

Description

Technical Field

[0001] The utility model relates to the technical field of laser testing, in particular to a high-precision, high-power constant current source. Background Art

[0002] During the development and post-processing testing phase of communication chips, chip testing requires the use of power supplies of various specifications as driving sources. Communication chips are generally LD laser chips, and their luminescence principle is based on stimulated radiation luminescence. The characteristic of this luminescence principle is that current drive directly generates lasers, so the light output power is linearly related to the current. Therefore, the driving source of communication chips generally chooses a constant current source. However, depending on the manufacturing process and application scenarios of different communication chips, the size of the driving current, the total power size and the heat generated by the chip are different. Therefore, when testing communication chips, a high-precision, high-power, narrow-pulse constant current source is required. Utility Model Content

[0003] In view of this, the utility model provides a high-precision, high-power constant current source to solve the problem of how to achieve constant current and precise control.

[0004] The utility model provides a high-precision high-power constant current source, comprising: a current control circuit, a switch circuit, and a feedback circuit, wherein the switch circuit has a first end at which a power supply voltage is input, and a second end thereof is connected to the first end of the feedback circuit; the feedback circuit has a second end connected to a load, and a third end thereof is connected to the first end of the current control circuit, and is used for collecting the power supply current of the load and converting it into a voltage signal, and feeding back the voltage signal to the current control circuit; the current control circuit has a second end connected to a control end of the switch circuit, and is used for comparing the voltage signal with the control voltage and outputting a control signal to the switch circuit; the control signal is used for controlling the switching circuit to be turned on or off.

[0005] The current control circuit of the utility model can generate a control voltage according to user needs. The current control circuit can compare the voltage signal fed back by the feedback circuit with the control voltage, and output a control signal to the switch circuit. The control signal can control the on or off of the switch circuit, that is, by controlling the on time and off time of the switch circuit, the supply voltage corresponding to the supply current of the load can follow the change of the control voltage, so as to realize precise control of the supply current.

[0006] In an optional embodiment, the current control circuit includes: a control voltage circuit and a switch control circuit, wherein the control voltage circuit is connected to the first end of the switch control circuit and is used to generate a control voltage; the switch control circuit has a second end connected to the third end of the feedback circuit and a third end connected to the control end of the switch circuit and is used to compare the voltage signal with the control voltage and then output a control signal to the switch circuit.

[0007] In an optional embodiment, the control voltage circuit includes: a current source, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a first operational amplifier and a first switch, wherein the first operational amplifier has a non-inverting input terminal connected to the first end of the first resistor, and its non-inverting input terminal is also grounded through the second resistor, its inverting input terminal is connected to the first end of the third resistor, and its inverting input terminal is also connected to its output terminal through the fourth resistor, and its output terminal is connected to the first end of the first switch; the first resistor has a second end connected to the first end of the fifth resistor and one end of the current source; the third resistor has a second end connected to the second end of the fifth resistor and the other end of the current source; the first switch has a second end connected to the first end of the switch control circuit.

[0008] In an optional embodiment, the switch control circuit includes: a sixth resistor, a first capacitor and a second operational amplifier, wherein the second operational amplifier has a non-inverting input terminal connected to the first end of the control voltage circuit, an inverting input terminal connected to the third end of the feedback circuit and the first end of the first capacitor, and an output terminal connected to the first end of the sixth resistor and the second end of the first capacitor; the sixth resistor has a second end connected to the control end of the switch circuit.

[0009] In an optional implementation, the switch circuit includes: a field effect transistor, wherein the field effect transistor has a drain inputting a supply voltage, a source connected to a first end of the feedback circuit, and a gate connected to a second end of the current control circuit.

[0010] The field effect transistor of the utility model can drive a large current and has a fast start-up time, can output a pulse current with a narrower pulse width, the rising edge of the current pulse can be controlled within 50uS, and the current size can reach twelve amperes.

[0011] In an optional embodiment, the feedback circuit includes: an acquisition circuit and a signal processing circuit, wherein the acquisition circuit has a first end connected to the second end of the switching circuit and the first end of the signal processing circuit, and a second end connected to the second end of the signal processing circuit, and a second end connected to the load; the signal processing circuit has a third end connected to the first end of the current control circuit, and is used to obtain the power supply current of the load through the acquisition circuit and convert it into a voltage signal, and feed the voltage signal back to the current control circuit.

[0012] In an optional embodiment, the acquisition circuit includes: a seventh resistor, wherein the first end of the seventh resistor is connected to the second end of the switching circuit and the first end of the signal processing circuit, the second end of the seventh resistor is connected to the second end of the signal processing circuit, and the second end of the seventh resistor is also connected to the load.

[0013] The feedback circuit control current method adopted in this solution can accurately control the current on the load, and the current accuracy can reach 0.5%. Compared with the solution with the seventh resistor at the first end of the switch circuit, this solution has wider requirements for the op amp, and the function can be achieved without using a rail-to-rail op amp.

[0014] In an optional embodiment, the signal processing circuit includes: a voltage follower circuit and a subtraction circuit, wherein the voltage follower circuit has a first end connected to the first end of the acquisition circuit, and a second end connected to the second end of the acquisition circuit, and is used to follow the voltage across the acquisition circuit; a subtraction circuit has a first end connected to the third end of the voltage follower circuit, a second end connected to the fourth end of the voltage follower circuit, and a third end connected to the first end of the current control circuit, and is used to obtain a voltage signal based on the voltage across the acquisition circuit.

[0015] In an optional embodiment, the voltage follower circuit includes: an eighth resistor, a ninth resistor, a third operational amplifier and a fourth operational amplifier, wherein the third operational amplifier has a non-inverting input terminal connected to the first end of the acquisition circuit, and an inverting input terminal connected to its output terminal and the first end of the eighth resistor; the fourth operational amplifier has a non-inverting input terminal connected to the second end of the acquisition circuit, and an inverting input terminal connected to its output terminal and the first end of the ninth resistor; the eighth resistor has a second end connected to the first end of the subtraction circuit; and the ninth resistor has a second end connected to the first end of the subtraction circuit.

[0016] In an optional embodiment, the subtraction circuit includes: a tenth resistor, an eleventh resistor, a twelfth resistor and a fifth operational amplifier, wherein the fifth operational amplifier has a non-inverting input terminal connected to the third end of the voltage follower circuit and the first end of the tenth resistor, an inverting input terminal connected to the fourth end of the voltage follower circuit and the first end of the eleventh resistor, and an output terminal connected to the first end of the twelfth resistor; the tenth resistor has a second end connected to ground; the eleventh resistor has a second end connected to the first end of the twelfth resistor; the twelfth resistor has a second end connected to the first end of the current control circuit.

[0017] Beneficial effects:

[0018] The current control circuit of the utility model can generate a control voltage according to user needs. The current control circuit can compare the voltage signal fed back by the feedback circuit with the control voltage, and output a control signal to the switch circuit. The control signal can control the on or off of the switch circuit, that is, by controlling the on time and off time of the switch circuit, the supply voltage corresponding to the supply current of the load can follow the change of the control voltage, so as to realize precise control of the supply current. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the specific implementation methods of the utility model or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 It is a composition diagram of a high-precision, high-power constant current source according to an embodiment of the utility model;

[0021] Figure 2 is a composition diagram of a current control circuit according to an embodiment of the utility model;

[0022] Figure 3 It is a specific circuit structure diagram of a high-precision, high-power constant current source according to an embodiment of the utility model;

[0023] Figure 4 is a composition diagram of a feedback circuit according to an embodiment of the utility model;

[0024] Figure 5 It is a composition diagram of a signal processing circuit according to an embodiment of the utility model. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the embodiment of the utility model clearer, the technical solution in the embodiment of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiment of the utility model. Obviously, the described embodiment is a part of the embodiment of the utility model, not all the embodiments. Based on the embodiment of the utility model, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the utility model.

[0026] In this embodiment, a high-precision high-power constant current source is provided. Figure 1 As shown, it includes: a current control circuit, a switching circuit, and a feedback circuit.

[0027] like Figure 1 As shown, the switch circuit has a first end inputting a supply voltage and a second end connected to a first end of a feedback circuit.

[0028] Specifically, the switch circuit is connected between the power supply voltage and the load. The on and off of the switch circuit can realize whether the power supply voltage can power the load, and by controlling the on time and off time of the switch circuit, that is, the duty cycle, constant current control of the power supply current of the load can be achieved.

[0029] Optionally, the switch circuit has a built-in controllable switch, which can be a MOS tube, IGBT switch tube or other device, or the switch circuit has a built-in DC-DC circuit, which can convert direct current into direct current, and the DC-DC circuit is not limited to BUCK circuit, BOOST circuit, BUCK-BOOST circuit.

[0030] Optionally, the supply voltage may be provided by a DC power supply or by at least one battery, which is not limited here.

[0031] like Figure 1 As shown, the feedback circuit has a second end connected to the load and a third end connected to the first end of the current control circuit. It is used to collect the power supply current of the load and convert it into a voltage signal, and feed the voltage signal back to the current control circuit.

[0032] Specifically, the feedback circuit can realize the collection of power supply current, the conversion of power supply current into voltage signal, and the functions of signal amplification and conditioning.

[0033] like Figure 1 As shown, the current control circuit has a second end connected to the control end of the switch circuit, and is used to compare the voltage signal with the control voltage and then output a control signal to the switch circuit; the control signal is used to control the on or off of the switch circuit.

[0034] Specifically, the current control circuit can have two functions: one is to generate a control voltage according to user needs, and the other is to compare the voltage signal fed back by the feedback circuit with the control voltage, and output a control signal to the switching circuit. The control signal can control the on or off of the switching circuit, that is, by controlling the on time and off time of the switching circuit, the supply voltage corresponding to the load supply current can follow the change of the control voltage to achieve precise control of the supply current.

[0035] Optionally, in the current control circuit, the control voltage can be generated by a current source combined with an amplification and conditioning circuit, and the voltage comparison can be obtained by a comparator. The specific implementation method is not limited here.

[0036] In some optional embodiments, such as Figure 2 As shown, the current control circuit includes: a control voltage circuit and a switch control circuit.

[0037] like Figure 2 As shown, the control voltage circuit is connected to the first end of the switch control circuit and is used to generate a control voltage.

[0038] Optionally, the control voltage circuit has a built-in controllable current source and an amplifier circuit, the controllable current source outputs a preset current, and the amplifier circuit obtains the control voltage by amplifying and converting the preset current.

[0039] like Figure 2 As shown, the switch control circuit has a second end connected to the third end of the feedback circuit, and a third end connected to the control end of the switch circuit, and is used to compare the voltage signal with the control voltage and then output a control signal to the switch circuit.

[0040] Specifically, the switch control circuit compares the voltage signal fed back by the feedback circuit with the control voltage, and outputs a control signal to the switch circuit. The control signal can control the on or off of the switch circuit, that is, by controlling the on time and off time of the switch circuit, the supply voltage corresponding to the supply current of the load can follow the change of the control voltage to achieve precise control of the supply current.

[0041] Optionally, the switch control circuit has a built-in comparator to achieve voltage comparison. A drive voltage can also be connected to the rear stage of the comparator, and the drive circuit can convert the control signal into a drive voltage to drive the switch circuit on and off.

[0042] In some optional embodiments, such as Figure 3 As shown, the control voltage circuit includes: a current source I1, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a first operational amplifier OP1 and a first switch S1.

[0043] like Figure 3 As shown, the first operational amplifier OP1 has a non-inverting input terminal connected to the first end of the first resistor R1, and the non-inverting input terminal is also grounded through the second resistor R2, the inverting input terminal is connected to the first end of the third resistor R3, and the inverting input terminal is also connected to the output terminal of the fourth resistor R4 through the fourth resistor R4, and the output terminal is connected to the first end of the first switch S1; the first resistor R1 has a second end connected to the first end of the fifth resistor R5 and one end of the current source I1; the third resistor R3 has a second end connected to the second end of the fifth resistor R5 and the other end of the current source I1; the first switch S1 has a second end connected to the first end of the switch control circuit (that is, the second operational amplifier OP2).

[0044] Specifically, the current source I1 outputs a small current to the fifth resistor R5, the voltage of the fifth resistor R5 is the control voltage, and the first operational amplifier OP1 collects the control voltage and transmits it to the switch control circuit. The output current amplitude of the current source I1 is set as required.

[0045] In some optional embodiments, such as Figure 3As shown, the switch control circuit includes: a sixth resistor R6, a first capacitor C1 and a second operational amplifier OP2, wherein the second operational amplifier OP2 has a non-inverting input terminal connected to the first end of the control voltage circuit, an inverting input terminal connected to the third end of the feedback circuit and the first end of the first capacitor C1, and an output terminal connected to the first end of the sixth resistor R6 and the second end of the first capacitor C1; the sixth resistor R6 has a second end connected to the control end of the switch circuit.

[0046] Specifically, the two input terminals of the second operational amplifier OP2 are respectively input with a control voltage and a voltage signal, and the second operational amplifier OP2 compares the control voltage with the voltage signal and outputs different comparison results. For example, when the control voltage is higher than the voltage signal, the second operational amplifier OP2 outputs a high-level signal to control the switch circuit to turn on; when the control voltage is lower than the voltage signal, the second operational amplifier OP2 outputs a low-level signal to control the switch circuit to turn off.

[0047] Optionally, the sixth resistor R6 may also be replaced by a mature driving circuit of a power electronic device in the related art to achieve driving of the switch tube.

[0048] In some optional embodiments, such as Figure 3 As shown, the switch circuit includes: a field effect transistor T1, wherein the field effect transistor T1 has a drain inputting a supply voltage, a source connected to a first end of a feedback circuit, and a gate connected to a second end of a current control circuit.

[0049] Specifically, Figure 3 The field effect transistor T1 in the circuit is a P-type field effect transistor. When it is turned on, the supply voltage supplies power to the load (i.e., DUT). When it is turned off, the supply voltage is disconnected from the load. The supply current is regulated by controlling the duty cycle of the field effect transistor T1.

[0050] In some optional embodiments, such as Figure 4 As shown, the feedback circuit includes: an acquisition circuit and a signal processing circuit.

[0051] like Figure 4 As shown, the acquisition circuit has a first end connected to the second end of the switch circuit and the first end of the signal processing circuit, a second end connected to the second end of the signal processing circuit, and a second end also connected to the load.

[0052] Specifically, the acquisition circuit is connected in series between the switch circuit and the load. Based on the principle that the current is equal everywhere in the series circuit, the current on the load is controlled by controlling the voltage across the acquisition circuit.

[0053] like Figure 4As shown, the signal processing circuit has a third end connected to the first end of the current control circuit, and is used to obtain the power supply current of the load through the acquisition circuit and convert it into a voltage signal, and feed the voltage signal back to the current control circuit.

[0054] In some optional embodiments, such as Figure 3 As shown, the acquisition circuit includes: a seventh resistor R7, wherein the first end of the seventh resistor R7 is connected to the second end of the switch circuit and the first end of the signal processing circuit, the second end is connected to the second end of the signal processing circuit, and the second end is also connected to the load.

[0055] Optionally, the acquisition circuit is not limited to Figure 3 In the structure shown, the acquisition circuit can be composed of linear components according to requirements.

[0056] In some optional embodiments, such as Figure 5 As shown, the signal processing circuit includes: a voltage follower circuit and a subtraction circuit.

[0057] like Figure 5 As shown, the voltage follower circuit has a first end connected to the first end of the acquisition circuit and a second end connected to the second end of the acquisition circuit, and is used to follow the voltage across the acquisition circuit.

[0058] Specifically, the voltage follower circuit has a built-in voltage follower to follow and obtain the voltage across the acquisition circuit.

[0059] like Figure 5 As shown, the subtraction circuit has a first end connected to the third end of the voltage follower circuit, a second end connected to the fourth end of the voltage follower circuit, and a third end connected to the first end of the current control circuit, and is used to obtain a voltage signal based on the voltage across the acquisition circuit.

[0060] Specifically, the subtraction circuit has a built-in subtractor to make a difference between the voltage at the first end of the acquisition circuit and the voltage at the second end of the acquisition circuit, and the difference is the voltage of the acquisition circuit.

[0061] In some optional embodiments, such as Figure 3 As shown, the voltage follower circuit includes: an eighth resistor R8, a ninth resistor R9, a third operational amplifier OP3 and a fourth operational amplifier OP4, wherein the third operational amplifier OP3 has a non-inverting input terminal connected to the first end of the acquisition circuit, and an inverting input terminal connected to its output terminal and the first end of the eighth resistor R8; the fourth operational amplifier OP4 has a non-inverting input terminal connected to the second end of the acquisition circuit, and an inverting input terminal connected to its output terminal and the first end of the ninth resistor R9; the eighth resistor R8 has a second end connected to the first end of the subtraction circuit; the ninth resistor R9 has a second end connected to the first end of the subtraction circuit.

[0062] In some optional embodiments, such as Figure 3 As shown, the subtraction circuit includes: a tenth resistor R10, an eleventh resistor R11, a twelfth resistor R12 and a fifth operational amplifier OP5, wherein the fifth operational amplifier OP5 has a non-inverting input terminal connected to the third end of the voltage follower circuit and the first end of the tenth resistor R10, an inverting input terminal connected to the fourth end of the voltage follower circuit and the first end of the eleventh resistor R11, and an output terminal connected to the first end of the twelfth resistor R12; the tenth resistor R10 has a second end connected to the ground; the eleventh resistor R11 has a second end connected to the first end of the twelfth resistor R12; the twelfth resistor R12 has a second end connected to the first end of the current control circuit.

[0063] Specifically, Figure 3 In the circuit, OP3 and OP4 are voltage followers, and OP5 is a subtractor. OP3, OP4, and OP5 form a feedback circuit to feed back the voltage across R7 to the inverting input of OP2. The non-inverting input of OP2 is connected to the control voltage. When the control voltage is input, the voltage at the non-inverting input of OP2 is different from the voltage at the inverting input. At this time, OP2 will output a voltage to control the current of the drain of T1. When the current gradually changes, the voltage across R7 gradually changes to the same as the control voltage. Through the feedback circuit, the voltage at the inverting input of OP2 will gradually approach the control voltage. When the voltages at the non-inverting input and the inverting input of OP2 are the same, the entire circuit returns to the initial stable state, and the current flowing through the load (DUT) can be obtained from the control voltage and R7.

[0064] Although the embodiments of the present invention are described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A high-precision, high-power constant current source, characterized in that: include: Current control circuit, switch circuit, feedback circuit, among which, A switch circuit, a first end of which is input with a supply voltage, and a second end of which is connected with the first end of the feedback circuit; A feedback circuit, a second end of which is connected to the load, and a third end of which is connected to the first end of the current control circuit, and is used to collect the power supply current of the load and convert it into a voltage signal, and feed the voltage signal back to the current control circuit; A current control circuit, a second end of which is connected to the control end of the switch circuit, and is used to compare the voltage signal with the control voltage and then output a control signal to the switch circuit; the control signal is used to control the switch circuit to be turned on or off; The current control circuit includes: a control voltage circuit and a switch control circuit, wherein: a control voltage circuit connected to the first end of the switch control circuit and used to generate the control voltage; The switch control circuit has a second end connected to the third end of the feedback circuit and a third end connected to the control end of the switch circuit, and is used to compare the voltage signal with the control voltage and then output a control signal to the switch circuit.

2. The high-precision, high-power constant current source according to claim 1, characterized in that: The control voltage circuit includes: a current source, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a first operational amplifier and a first switch, wherein: A first operational amplifier, a non-inverting input terminal of which is connected to the first end of the first resistor, a non-inverting input terminal of which is also connected to the ground through the second resistor, an inverting input terminal of which is connected to the first end of the third resistor, a inverting input terminal of which is also connected to the output terminal of the third resistor through the fourth resistor, and an output terminal of which is connected to the first end of the first switch; a first resistor, a second end of which is connected to the first end of the fifth resistor and one end of the current source; a third resistor, a second end of which is connected to the second end of the fifth resistor and the other end of the current source; The first switch has a second end connected to the first end of the switch control circuit.

3. The high-precision, high-power constant current source according to claim 1, characterized in that: The switch control circuit includes: a sixth resistor, a first capacitor and a second operational amplifier, wherein: a second operational amplifier, wherein a non-inverting input terminal of the second operational amplifier is connected to the first terminal of the control voltage circuit, an inverting input terminal of the second operational amplifier is connected to the third terminal of the feedback circuit and the first terminal of the first capacitor, and an output terminal of the second operational amplifier is connected to the first terminal of the sixth resistor and the second terminal of the first capacitor; A sixth resistor, a second end of which is connected to the control end of the switch circuit.

4. The high-precision, high-power constant current source according to claim 1, characterized in that: The switch circuit comprises: a field effect transistor, wherein: A field effect transistor, a drain of which inputs a supply voltage, a source of which is connected to the first end of the feedback circuit, and a gate of which is connected to the second end of the current control circuit.

5. The high-precision, high-power constant current source according to claim 1, characterized in that: The feedback circuit includes: an acquisition circuit and a signal processing circuit, wherein: An acquisition circuit, wherein a first end of the acquisition circuit is connected to the second end of the switch circuit and the first end of the signal processing circuit, a second end of the acquisition circuit is connected to the second end of the signal processing circuit, and a second end of the acquisition circuit is also connected to a load; The signal processing circuit has a third end connected to the first end of the current control circuit, and is used to obtain the power supply current of the load through the acquisition circuit and convert it into a voltage signal, and feed the voltage signal back to the current control circuit.

6. The high-precision, high-power constant current source according to claim 5, characterized in that: The acquisition circuit includes: a seventh resistor, wherein: A seventh resistor has a first end connected to the second end of the switch circuit and the first end of the signal processing circuit, a second end connected to the second end of the signal processing circuit, and a second end also connected to the load.

7. The high-precision, high-power constant current source according to claim 5, characterized in that: The signal processing circuit includes: a voltage follower circuit and a subtraction circuit, wherein: A voltage follower circuit, a first end of which is connected to the first end of the acquisition circuit, and a second end of which is connected to the second end of the acquisition circuit, and is used to follow the voltage across the acquisition circuit; A subtraction circuit, whose first end is connected to the third end of the voltage follower circuit, whose second end is connected to the fourth end of the voltage follower circuit, and whose third end is connected to the first end of the current control circuit, is used to obtain the voltage signal based on the voltage across the acquisition circuit.

8. The high-precision, high-power constant current source according to claim 7, characterized in that: The voltage follower circuit includes: an eighth resistor, a ninth resistor, a third operational amplifier and a fourth operational amplifier, wherein: A third operational amplifier, whose non-inverting input terminal is connected to the first terminal of the acquisition circuit, and whose inverting input terminal is connected to its output terminal and the first terminal of the eighth resistor; A fourth operational amplifier, whose non-inverting input terminal is connected to the second terminal of the acquisition circuit, and whose inverting input terminal is connected to its output terminal and the first terminal of the ninth resistor; an eighth resistor, a second end of which is connected to the first end of the subtraction circuit; A ninth resistor has a second end connected to the first end of the subtraction circuit.

9. The high-precision, high-power constant current source according to claim 8, characterized in that: The subtraction circuit includes: a tenth resistor, an eleventh resistor, a twelfth resistor and a fifth operational amplifier, wherein: a fifth operational amplifier, whose non-inverting input terminal is connected to the third terminal of the voltage follower circuit and the first terminal of the tenth resistor, whose inverting input terminal is connected to the fourth terminal of the voltage follower circuit and the first terminal of the eleventh resistor, and whose output terminal is connected to the first terminal of the twelfth resistor; a tenth resistor, a second end of which is grounded; an eleventh resistor, a second end of which is connected to the first end of the twelfth resistor; A twelfth resistor has a second end connected to the first end of the current control circuit.

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