Output constant current adjustable circuit and control method thereof

Abstract

The invention provides an output constant current adjustable circuit and a control method thereof, and the circuit comprises a power conversion module which is used for converting an input voltage into a stable and adjustable constant output current; the current sampling module is connected to the output end of the power supply conversion module and is used for sampling current from the output end of the power supply conversion module and converting the current into sampling voltage; the reference voltage comparison module is used for generating adjustable reference voltage corresponding to the constant output current and comparing the reference voltage with the sampling voltage; the optocoupler feedback module is connected to the output end of the reference voltage comparison module and used for feeding back a comparison result of the reference voltage and the sampling voltage to the control module; and the control module is connected with the power supply conversion module and the optocoupler feedback module and is used for adjusting the working state of the power supply conversion module according to a voltage comparison result fed back by the optocoupler feedback module, so that the output current of the power supply conversion module is kept as the constant output current. The method has higher stability and higher response speed.

Description

Technical Field

[0001] This invention relates to the field of electronic circuit technology, and in particular to an adjustable constant current output circuit and its control method. Background Technology

[0002] A constant current source is a power supply circuit that outputs a fixed current. Because the output current of a constant current source is unaffected by input voltage fluctuations and load changes, it has wide applications in lighting control, charging control, and semiconductor device testing. Traditional constant current sources output a single, fixed current. However, as the application scenarios of constant current sources have become increasingly diverse, adjustable current constant current sources have been designed to meet the demand for adjustable current. For example, Chinese patent CN103929061A achieves controllable output current by connecting an adjustable resistor to the output terminal of the constant current source. However, when the resistor connected to the output terminal of the constant current source changes, it causes the current to change with the load voltage, resulting in oscillations in the output current and a delay in the output response of the constant current source. In high-frequency applications, its response speed may not meet the requirements. Summary of the Invention

[0003] Based on the above problems, this invention proposes an adjustable constant current output circuit and its control method, which has higher stability and faster response speed.

[0004] In view of this, a first aspect of the present invention provides an adjustable constant current output circuit, comprising: A power conversion module is used to convert the input voltage into a stable and adjustable constant output current; A current sampling module is connected to the output terminal of the power conversion module and is used to sample the current from the output terminal of the power conversion module and convert it into a sampling voltage. A reference voltage comparison module is used to generate an adjustable reference voltage corresponding to the constant output current and compare the reference voltage with the sampled voltage; An optocoupler feedback module is connected to the output of the reference voltage comparison module and is used to feed back the comparison result between the reference voltage and the sampled voltage to the control module. A control module, connected to the power conversion module and the optocoupler feedback module, is used to adjust the operating state of the power conversion module according to the voltage comparison result fed back by the optocoupler feedback module, so that the output current of the power conversion module is kept at the constant output current.

[0005] Optionally, a current-limiting resistor is also included between the output terminal of the power conversion module and ground. The current sampling module includes a second resistor. Third resistor and the first operational amplifier The second resistor One end is connected to the current limiting resistor One end is connected to the output terminal of the power conversion module, and the other end is connected to the first operational amplifier. The inverting input terminal, the third resistor The two ends are respectively connected to the first operational amplifier The inverting input terminal and the first operational amplifier The output terminal of the first operational amplifier The non-inverting input terminal is grounded, and the first operational amplifier The negative power supply terminal is grounded, and the first operational amplifier... Connect the positive power supply terminal to the power source.

[0006] Optionally, the reference voltage comparison module includes a fourth resistor. Fifth resistor First capacitor Adjustable resistor and the second operational amplifier The first operational amplifier The output terminal is connected to the second operational amplifier. The inverting input terminal; the fifth resistor and the first capacitor After being connected in series, one end is connected to the second operational amplifier. The inverting input terminal is connected to the second operational amplifier, and the other end is connected to the second operational amplifier. The output terminal; the fourth resistor One end is connected to the input voltage The other end is connected to the second operational amplifier. The non-inverting input terminal; the adjustable resistor One end is connected to the fourth resistor and the second operational amplifier Between the non-inverting input terminals, the adjustable resistor The other end is grounded.

[0007] Optionally, the optocoupler feedback module includes a sixth resistor. and an optocoupler, the optocoupler including a light-emitting diode and a photoelectric sensor; the sixth resistor One end is connected to the power supply, and the other end is connected to the current input terminal of the light-emitting diode; the second operational amplifier The output terminal of the photoelectric sensor is connected to the current output terminal of the light-emitting diode; the first output terminal of the photoelectric sensor is connected to the controller, and the second output terminal of the photoelectric sensor is grounded.

[0008] A second aspect of the present invention provides a control method for an output constant current adjustable circuit, comprising: Configure the target resistance value of the adjustable resistor To enable the reference voltage comparison module to output a reference voltage: ; Determine the sampling voltage output by the current sampling module. ; The sampled voltage With the reference voltage Compare; According to the sampling voltage With the reference voltage The comparison results are used to adjust the operating state of the power conversion module.

[0009] Optionally, the target resistance value of the adjustable resistor is configured. So that the reference voltage comparison module outputs a reference voltage. Before the steps, it also includes: Define the sampling amplification factor of the sampling module: ; Configure target constant output current ; Based on the target constant output current Determine the target resistance value of the adjustable resistor: .

[0010] Optionally, the sampling voltage output by the current sampling module is determined. The specific steps include: The current is obtained by sampling the output of the power conversion module through a current sampling module. ; Calculate the voltage at the sampling node: ; Convert the sampling node voltage into the sampling voltage: .

[0011] Optionally, based on the sampling voltage With the reference voltage The steps for adjusting the operating state of the power conversion module based on the comparison results specifically include: According to the sampling voltage With the reference voltage Configure PID control parameters according to the magnitude relationship; Generate the PWM control signal corresponding to the PID control parameters; The PWM control signal is used to control the on-time of the switching transistor of the power conversion module so that the output current of the power conversion module remains at the constant output current.

[0012] Optionally, the control method for the output constant current adjustable circuit further includes: With a current greater than the target constant output current Initial constant output current Start the constant current source; Maintain the initial constant output current And continuously start the buffer duration ; Switch the output current of the constant current source to the target constant output current. ; Continuous current protection duration Then, the output current of the constant current source is... Conduct testing; When the output current of the constant current source Greater than the preset protection current When necessary, protective measures should be implemented.

[0013] Optionally, with a current greater than the target constant output current. Initial constant output current Before starting the constant current source, the following steps are also included: Configure startup buffer duration Current protection duration Initial constant output current Target constant output current and protective current ,in: ,and ; With a current greater than the target constant output current Initial constant output current The specific steps to start a constant current source include: Configure the resistance value of the adjustable resistor to the first target resistance value. The first target resistance value satisfy: ; Switch the output current of the constant current source to the target constant output current. The specific steps include: Configure the resistance value of the adjustable resistor to the second target resistance value. The first target resistance value satisfy: ; Continuous current protection duration Then, the output current of the constant current source is... The specific steps for conducting the test include: The adjustable resistor is kept at the second target resistance value. And continue ; exist The output current of the power conversion module is then acquired via a current sampling module. .

[0014] This invention proposes an adjustable constant current output circuit and its control method. The adjustable constant current output circuit includes a power conversion module for converting an input voltage into a stable and adjustable constant output current; a current sampling module connected to the output terminal of the power conversion module for sampling the current from the output terminal of the power conversion module and converting it into a sampling voltage; a reference voltage comparison module for generating an adjustable reference voltage corresponding to the constant output current and comparing the reference voltage with the sampling voltage; an optocoupler feedback module connected to the output terminal of the reference voltage comparison module for feeding back the comparison result of the reference voltage and the sampling voltage to a control module; and a control module connected to the power conversion module and the optocoupler feedback module for adjusting the operating state of the power conversion module according to the voltage comparison result fed back by the optocoupler feedback module, so that the output current of the power conversion module remains at the constant output current, resulting in higher stability and faster response speed. Attached Figure Description

[0015] Figure 1 This is a circuit block diagram of an adjustable constant current output circuit provided in one embodiment of the present invention; Figure 2 This is a circuit diagram of an adjustable constant current output circuit provided in one embodiment of the present invention; Figure 3 This is a circuit diagram of an adjustable constant current output circuit provided in one embodiment of the present invention. Detailed Implementation

[0016] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0017] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0018] In the description of this invention, the term "multiple" refers to two or more. Unless otherwise explicitly defined, the terms "upper," "lower," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. The terms "connect," "install," "fix," etc., should be interpreted broadly. For example, "connect" can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "multiple" means two or more.

[0019] In the description of this specification, the terms "one embodiment," "some implementations," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0020] The following description, with reference to the accompanying drawings, describes an adjustable constant current output circuit and its control method according to some embodiments of the present invention.

[0021] like Figure 1 As shown, a first aspect of the present invention provides an adjustable constant current output circuit, comprising: A power conversion module is used to convert the input voltage into a stable and adjustable constant output current; A current sampling module is connected to the output terminal of the power conversion module and is used to sample the current from the output terminal of the power conversion module and convert it into a sampling voltage. A reference voltage comparison module is used to generate an adjustable reference voltage corresponding to the constant output current and compare the reference voltage with the sampled voltage; An optocoupler feedback module is connected to the output of the reference voltage comparison module and is used to feed back the comparison result between the reference voltage and the sampled voltage to the control module. A control module, connected to the power conversion module and the optocoupler feedback module, is used to adjust the operating state of the power conversion module according to the voltage comparison result fed back by the optocoupler feedback module, so that the output current of the power conversion module is kept at the constant output current.

[0022] The power conversion module is a circuit module that converts DC or AC voltage VIN (input voltage) into an adjustable and constant output current that can be provided to the load through methods such as boosting, bucking, and regulating. In the technical solution of this invention, the power conversion module is controlled by the control module, which adjusts the operating state of the power conversion module based on a sampled feedback signal. For example, the control module adjusts the on-time of the switching transistor of the power conversion module through a PWM (Pulse Width Modulation) control loop to achieve constant current output. In some embodiments of this invention, the power conversion module can be a DC / DC converter, such as a Buck converter, Boost converter, or Buck-Boost converter, or a linear regulator or a switching power supply.

[0023] The current sampling module is connected to the output terminal of the power conversion module. By connecting a low-impedance sampling element, such as a low-resistance resistor, in series at the output terminal of the power conversion module, the output current of the power conversion module is converted into a measurable voltage signal.

[0024] The reference voltage comparison module generates an adjustable reference voltage and compares it with the sampled voltage. The reference voltage also corresponds to a pre-configured target constant output current. When the output current of the power conversion module is inconsistent with the set target constant output current, the sampled voltage output by the current sampling module will also be inconsistent with the reference voltage. When the two are inconsistent, the reference voltage comparison module outputs an error signal to the optocoupler feedback module.

[0025] The optocoupler feedback module feeds back the error signal output by the reference voltage comparison module to the control module in the form of an optical signal, so that the control module can adjust the duty cycle of the PWM signal of the power conversion module.

[0026] like Figure 2As shown, a current-limiting resistor is also included between the output terminal of the power conversion module and ground. The current sampling module includes a second resistor. Third resistor and the first operational amplifier The second resistor One end is connected to the current limiting resistor One end is connected to the output terminal of the power conversion module, and the other end is connected to the first operational amplifier. The inverting input terminal, the third resistor The two ends are respectively connected to the first operational amplifier The inverting input terminal and the first operational amplifier The output terminal of the first operational amplifier The non-inverting input terminal is grounded, and the first operational amplifier The negative power supply terminal is grounded, and the first operational amplifier... Connect the positive power supply terminal to the power source.

[0027] In the technical solution of the above embodiments, the first operational amplifier The negative power supply terminal is connected to VCC (Voltage Common Collector, circuit supply voltage). The voltage drop across the first resistor is proportional to the output current, thus the sampling error is small. The first operational amplifier... Through the second resistor and the third resistor An adjustable gain is applied to the node voltage to boost the weak node voltage signal to a value within the 0-VCC range. The magnitude of this gain is related to the second resistor. and the third resistor The resistance value is related. This is because the first operational amplifier... The positive and negative power supplies are asymmetrical. Its negative power supply terminal is connected to VCC and grounded. Its input bias current is eliminated at both the load and source terminals, reducing common-mode error. It has strong suppression capability for common-mode noise and can maintain stable output in harsh environments.

[0028] Optionally, the reference voltage comparison module includes a fourth resistor. Fifth resistor First capacitor Adjustable resistor and the second operational amplifier The first operational amplifier The output terminal is connected to the second operational amplifier. The inverting input terminal; the fifth resistor and the first capacitor After being connected in series, one end is connected to the second operational amplifier. The inverting input terminal is connected to the second operational amplifier, and the other end is connected to the second operational amplifier. The output terminal; the fourth resistor One end is connected to the input voltage The other end is connected to the second operational amplifier. The non-inverting input terminal; the adjustable resistor One end is connected to the fourth resistor and the second operational amplifier Between the non-inverting input terminals, the adjustable resistor The other end is grounded.

[0029] In the technical solution of the above embodiments, the fourth resistor and the adjustable resistor This forms an adjustable reference voltage source, which can output 0- The reference voltage between them enables high-precision reference voltage setting. The fifth resistor... and the first capacitor A low-pass filter network is formed in the second operational amplifier. A first-order RC filter is formed at the inverting input, and its cutoff frequency is usually set below several hundred hertz, so that the driving current of the optocoupler LED presents a very stable DC value.

[0030] In a specific implementation, the adjustable resistor It can be a mechanically adjustable resistor, which can be linearly adjusted via a knob or similar mechanism. The adjustable resistor... It can also be a digital adjustable resistor, whose resistance value is adjusted by the digital control signal of the control module. For example, it can be a programmable resistor such as a sliding resistor driven by a DAC (Digital to Analog Converter).

[0031] Optionally, the optocoupler feedback module includes a sixth resistor. and an optocoupler, the optocoupler including a light-emitting diode and a photoelectric sensor; the sixth resistor One end is connected to the power supply, and the other end is connected to the current input terminal of the light-emitting diode; the second operational amplifier The output terminal of the photoelectric sensor is connected to the current output terminal of the light-emitting diode; the first output terminal of the photoelectric sensor is connected to the controller, and the second output terminal of the photoelectric sensor is grounded.

[0032] Specifically, the sixth resistor This is a current-limiting resistor used to limit the maximum drive current of the light-emitting diode (LED). The light signal from the LED in the optocoupler is converted into a voltage signal by the photoelectric sensor, which is then used for feedback control by the control module. The optocoupler provides complete electrical isolation between the high and low sides, preventing high-side noise, transient overvoltage, or reverse current from being fed back to the control module.

[0033] In some embodiments of the present invention, the photoelectric sensor may be a phototransistor, the first output terminal of the photoelectric sensor is the collector of the phototransistor, and the second output terminal of the photoelectric sensor is the emitter of the phototransistor.

[0034] like Figure 3 As shown, a second aspect of the present invention provides a control method for an output constant current adjustable circuit, comprising: Configure the target resistance value of the adjustable resistor To enable the reference voltage comparison module to output a reference voltage: ; Determine the sampling voltage output by the current sampling module. ; The sampled voltage With the reference voltage Compare; According to the sampling voltage With the reference voltage The comparison results are used to adjust the operating state of the power conversion module.

[0035] In the technical solution of the above embodiments, the target resistance value is configured according to the required output current. The output current of the power conversion module is converted into node voltage by the current sampling module, and then amplified to obtain the sampling voltage. The sampled voltage The target resistance value is compared with the reference voltage by the comparison module. Corresponding reference voltage A comparison is made, and the operating state of the power conversion module is adjusted based on the comparison result. The target resistance value is... It can be configured using programmable resistors, such as sliding resistors driven by a DAC, or manually configured using mechanical adjustable resistors with knobs.

[0036] By adopting the technical solution of the above implementation method, the target current is mapped to an adjustable reference voltage, and closed-loop control is achieved by high-speed comparison and optocoupler isolation. That is, a high-speed operational amplifier is used to compare the reference voltage and the sampled voltage, and the power conversion module can use PWM control to achieve fast response, so that the entire feedback control process can achieve a response speed of milliseconds.

[0037] Optionally, the target resistance value of the adjustable resistor is configured. So that the reference voltage comparison module outputs a reference voltage. Before the steps, it also includes: Define the sampling amplification factor of the sampling module: ; Configure target constant output current ; Based on the target constant output current Determine the target resistance value of the adjustable resistor: .

[0038] The sampling amplification factor is the voltage gain coefficient of the current sampling module, and its gain can be configured during the design by selecting the resistance values ​​of the second resistor and the third resistor.

[0039] In the technical solution of the present invention, due to the target resistance value and the target constant output current There is a clear correspondence, so it is only necessary to determine the target constant output current. The corresponding target resistance value This generates a corresponding reference voltage, allowing the circuit's current output to quickly stabilize and maintain the target constant output current. .

[0040] Optionally, the sampling voltage output by the current sampling module is determined. The specific steps include: The current is obtained by sampling the output of the power conversion module through a current sampling module. ; Calculate the voltage at the sampling node: ; Convert the sampling node voltage into the sampling voltage: .

[0041] For example, the first resistor It can be a high-precision, low-temperature-drift, low-resistance shunt resistor. Using the technical solution of the above embodiment, the sampling voltage... It is the node voltage The linear gain is obtained by ensuring that the amplified signal remains linear throughout the entire operating range, thus making the comparator error predictable.

[0042] Optionally, based on the sampling voltage With the reference voltage The steps for adjusting the operating state of the power conversion module based on the comparison results specifically include: According to the sampling voltage With the reference voltage Configure PID (Proportion Integration Differentiation) control parameters according to the magnitude relationship; Generate the PWM control signal corresponding to the PID control parameters; The PWM control signal is used to control the on-time of the switching transistor of the power conversion module so that the output current of the power conversion module remains at the constant output current.

[0043] The technical solution of the above implementation method, which combines PID with PWM duty cycle control, can complete current error correction in microseconds, meeting the application requirements of high-load dynamic changes such as LED (Light Emitting Diode) driving and lithium battery charging control.

[0044] Optionally, the control method for the output constant current adjustable circuit further includes: With a current greater than the target constant output current Initial constant output current Start the constant current source; Maintain the initial constant output current And continuously start the buffer duration ; Switch the output current of the constant current source to the target constant output current. ; Continuous current protection duration Then, the output current of the constant current source is... Conduct testing; When the output current of the constant current source Greater than the preset protection current When necessary, protective measures should be implemented.

[0045] In the technical solution of the above embodiments, the initial constant output current is maintained. And continuously start the buffer duration The specific steps are as follows: maintain the resistance of the adjustable resistor at the first target resistance value. And continue .

[0046] Optionally, with a current greater than the target constant output current. Initial constant output current Before starting the constant current source, the following steps are also included: Configure startup buffer duration Current protection duration Initial constant output current Target constant output current and protective current ,in: ,and ; With a current greater than the target constant output current Initial constant output current The specific steps to start a constant current source include: Configure the resistance value of the adjustable resistor to the first target resistance value. The first target resistance value satisfy: ; Switch the output current of the constant current source to the target constant output current. The specific steps include: Configure the resistance value of the adjustable resistor to the second target resistance value. The first target resistance value satisfy: ; Continuous current protection duration Then, the output current of the constant current source is... The specific steps for conducting the test include: The adjustable resistor is kept at the second target resistance value. And continue ; exist The output current of the power conversion module is then acquired via a current sampling module. .

[0047] Furthermore, in The output current of the power conversion module is then acquired via a current sampling module. Following these steps, the following are also included: Determine the output current of the power conversion module Does it meet the requirements? ; when At that time, determine the output current of the constant current source. Greater than the preset protection current Implement protective measures.

[0048] By adopting the technical solution of the above implementation method, the power devices in the circuit can be rapidly heated to the operating area through high current start-up, which can reduce the waiting time for voltage and temperature to stabilize, shorten the start-up delay, improve the response speed, and make the control loop of the internal regulation circuit more stable under high current, resulting in smaller errors during subsequent switching.

[0049] In addition, high-current preheating allows the internal reference voltage and temperature compensation to quickly reach a steady state, overcoming the problem of output drift of constant current sources under initial low load conditions.

[0050] Buffer duration This setting can reduce continuous heat accumulation and avoid the risk of overheating caused by long-term high-current operation, such as MOS (Metal Oxide Semiconductor) burnout and lithium plating in the battery.

[0051] Furthermore, to prevent the current from still exceeding the expected value after current reduction, such as due to load short circuits or mechanical jamming, a protective current is used. The setting can promptly implement protective measures such as shutting off the output in case of abnormal load or measurement error causing an increase in current, thus preventing the device from burning out.

[0052] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0053] As described above, these embodiments of the present invention do not exhaustively cover all details, nor do they limit the invention to the specific embodiments described. Clearly, many modifications and variations can be made based on the above description. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to effectively utilize the invention and its modifications. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. An adjustable constant current output circuit, characterized in that, include: A power conversion module is used to convert the input voltage into a stable and adjustable constant output current; A current sampling module is connected to the output terminal of the power conversion module and is used to sample the current from the output terminal of the power conversion module and convert it into a sampling voltage. A reference voltage comparison module is used to generate an adjustable reference voltage corresponding to the constant output current and compare the reference voltage with the sampled voltage; An optocoupler feedback module is connected to the output of the reference voltage comparison module and is used to feed back the comparison result between the reference voltage and the sampled voltage to the control module. A control module, connected to the power conversion module and the optocoupler feedback module, is used to adjust the operating state of the power conversion module according to the voltage comparison result fed back by the optocoupler feedback module, so that the output current of the power conversion module is kept at the constant output current.

2. The adjustable constant current output circuit according to claim 1, characterized in that, A current-limiting resistor is also included between the output terminal of the power conversion module and ground. The current sampling module includes a second resistor. Third resistor and the first operational amplifier The second resistor One end is connected to the current limiting resistor One end is connected to the output terminal of the power conversion module, and the other end is connected to the first operational amplifier. The inverting input terminal, the third resistor The two ends are respectively connected to the first operational amplifier The inverting input terminal and the first operational amplifier The output terminal of the first operational amplifier The non-inverting input terminal is grounded, and the first operational amplifier The negative power supply terminal is grounded, and the first operational amplifier... Connect the positive power supply terminal to the power source.

3. The adjustable constant current output circuit according to claim 2, characterized in that, The reference voltage comparison module includes a fourth resistor. Fifth resistor First capacitor Adjustable resistor and the second operational amplifier The first operational amplifier The output terminal is connected to the second operational amplifier. The inverting input terminal; the fifth resistor and the first capacitor After being connected in series, one end is connected to the second operational amplifier. The inverting input terminal is connected to the second operational amplifier, and the other end is connected to the second operational amplifier. The output terminal; the fourth resistor One end is connected to the input voltage The other end is connected to the second operational amplifier. The non-inverting input terminal; the adjustable resistor One end is connected to the fourth resistor and the second operational amplifier Between the non-inverting input terminals, the adjustable resistor The other end is grounded.

4. The adjustable constant current output circuit according to claim 3, characterized in that, The optocoupler feedback module includes a sixth resistor. and an optocoupler, the optocoupler including a light-emitting diode and a photoelectric sensor; the sixth resistor One end is connected to the power supply, and the other end is connected to the current input terminal of the light-emitting diode; the second operational amplifier The output terminal of the photoelectric sensor is connected to the current output terminal of the light-emitting diode; the first output terminal of the photoelectric sensor is connected to the controller, and the second output terminal of the photoelectric sensor is grounded.

5. A control method applied to the output constant current adjustable circuit as described in any one of claims 1-4, characterized in that, include: Configure the target resistance value of the adjustable resistor To enable the reference voltage comparison module to output a reference voltage: ； Determine the sampling voltage output by the current sampling module. ; The sampled voltage With the reference voltage Compare; According to the sampling voltage With the reference voltage The comparison results are used to adjust the operating state of the power conversion module.

6. The control method for the output constant current adjustable circuit according to claim 5, characterized in that, Configure the target resistance value of the adjustable resistor. So that the reference voltage comparison module outputs a reference voltage. Before the steps, it also includes: Define the sampling amplification factor of the sampling module: ； Configure target constant output current ; Based on the target constant output current Determine the target resistance value of the adjustable resistor: 。 7. The control method for the output constant current adjustable circuit according to claim 6, characterized in that, Determine the sampling voltage output by the current sampling module. The specific steps include: The current is obtained by sampling the output of the power conversion module through a current sampling module. ; Calculate the voltage at the sampling node: ； Convert the sampling node voltage into the sampling voltage: 。 8. The control method for the output constant current adjustable circuit according to claim 6, characterized in that, According to the sampling voltage With the reference voltage The steps for adjusting the operating state of the power conversion module based on the comparison results specifically include: According to the sampling voltage With the reference voltage Configure PID control parameters according to the magnitude relationship; Generate the PWM control signal corresponding to the PID control parameters; The PWM control signal is used to control the on-time of the switching transistor of the power conversion module so that the output current of the power conversion module remains at the constant output current.

9. The control method for the output constant current adjustable circuit according to claim 6, characterized in that, Also includes: With a current greater than the target constant output current Initial constant output current Start the constant current source; Maintain the initial constant output current And continuously start the buffer duration ; Switch the output current of the constant current source to the target constant output current. ; Continuous current protection duration Then, the output current of the constant current source is... Conduct testing; When the output current of the constant current source Greater than the preset protection current When necessary, protective measures should be implemented.

10. The control method for the output constant current adjustable circuit according to claim 9, characterized in that, With a constant output current greater than the target Initial constant output current Before starting the constant current source, the following steps are also included: Configure startup buffer duration Current protection duration Initial constant output current Target constant output current and protective current ,in: ,and ; With a current greater than the target constant output current Initial constant output current The specific steps to start a constant current source include: Configure the resistance value of the adjustable resistor to the first target resistance value. The first target resistance value satisfy: ； Switch the output current of the constant current source to the target constant output current. The specific steps include: Configure the resistance value of the adjustable resistor to the second target resistance value. The first target resistance value satisfy: ； Continuous current protection duration Then, the output current of the constant current source is... The specific steps for conducting the test include: The adjustable resistor is kept at the second target resistance value. And continue ; exist The output current of the power conversion module is then acquired via a current sampling module. .

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