Constant-current driving circuit and physiotherapy instrument

Abstract

The invention relates to the technical field of electronic control, in particular to a constant-current driving circuit and a physiotherapy instrument. The constant-current driving circuit adopts a monopulse hardware closed-loop control circuit, current output is adjusted by acquiring real-time feedback of stimulation current, high-precision constant-current control is realized, sampling and control by software are not needed, software complexity is reduced, and compared with software control, the constant-current driving circuit has higher response speed and higher reliability. Current output can be adjusted in real time according to the change of an external load, the response is quick, the circuit design is simplified, the number of circuit elements is reduced, the circuit structure is simple, the size of the physiotherapy instrument is reduced, and the reliability and stability of the system are also improved.

Description

Technical Field

[0001] This application relates to the field of electronic control technology, specifically to a constant current drive circuit and a physiotherapy device. Background Technology

[0002] Physiotherapy devices are medical equipment that utilize physical factors to act on the human body to prevent and treat diseases. Common physical factors include electricity, magnetism, light, and sound, among which electrical stimulation devices are an important type of physiotherapy device. Electrical stimulation devices stimulate human tissues by generating specific electrical currents to regulate physiological functions, relieve pain, or promote tissue repair.

[0003] In existing technologies, since electrical stimulation devices act on the human body, they are required to maintain the stability of the current to the greatest extent possible during operation, and to output in a constant voltage or constant current manner. However, current constant current output solutions often suffer from problems such as excessive size, slow response speed, and poor constant current accuracy. Summary of the Invention

[0004] In view of the above problems, this application provides a constant current drive circuit and a physiotherapy device to solve the above-mentioned technical problems existing in the prior art.

[0005] One aspect of this application provides a constant current driving circuit, the circuit including a first operational amplifier unit, a second operational amplifier unit, a first transistor and a second transistor, the first transistor and the second transistor having opposite polarities; it also includes a third operational amplifier unit, a fourth operational amplifier unit, a third transistor and a fourth transistor, the third transistor and the fourth transistor having opposite polarities; The first input terminal of the first operational amplifier unit is used to receive a first control signal. The second input terminal of the first operational amplifier unit is connected to its output terminal, and its output terminal is connected to the base of the first transistor and the base of the second transistor respectively. The collector of the first transistor is connected to a power supply signal, its emitter is electrically connected to the emitter of the second transistor, and its emitter is also connected to an external first contact. The collector of the second transistor is electrically connected to the first input terminal of the second operational amplifier unit. The output terminal of the second operational amplifier unit is connected to its second input terminal to amplify the input signal at its first input terminal and send the amplified signal to the second input terminal of the third operational amplifier unit. The first input terminal of the third operational amplifier unit is used to receive a second control signal, wherein the first control signal and the second control signal are pulse signals with opposite phases. The output terminal of the third operational amplifier unit is connected to its second input terminal. The third operational amplifier unit is used to adjust the second control signal according to the amplified signal output by the second operational amplifier unit, and output the adjusted second control signal to the base of the third transistor and the base of the fourth transistor. The collector of the third transistor is connected to a power supply signal, its emitter is connected to the emitter of the fourth transistor, and its emitter is also connected to an external second contact. The collector of the fourth transistor is electrically connected to the first input terminal of the fourth operational amplifier unit. The output terminal of the fourth operational amplifier unit is connected to its second input terminal, used to amplify the input signal at its first input terminal, and send the amplified signal to the second input terminal of the first operational amplifier unit, so that the first operational amplifier unit adjusts the first control signal according to the amplified signal, and outputs the adjusted first control signal to the base of the first transistor and the base of the second transistor.

[0006] According to another aspect of the embodiments of this application, a physiotherapy device is also proposed, including the constant current driving current, the first contact and the second contact described in the above embodiments; The first and second contacts are used to make contact with an external load.

[0007] In summary, the constant current drive circuit proposed in this application controls the magnitude and on / off state of the stimulation current through an operational amplifier unit and a switching transistor to stimulate an external load. When the resistance of the external load changes, the current flowing through it also changes. To capture this change, this application samplees the stimulation current flowing through the external load at the back end, amplifies the sampled current through an operational amplifier unit, and feeds the amplified current back to the operational amplifier unit through which the single-pulse control signal passes. After capturing the change in the feedback stimulation current, the operational amplifier unit controls the conduction level of the switching transistor by adjusting the output voltage, thereby adjusting the output magnitude of the stimulation current and maintaining a constant current output. This application embodiment uses a single-pulse hardware closed-loop setting, eliminating the need for software sampling and control, reducing software complexity, and providing a faster response speed compared to software control, enabling real-time adjustment of the current output according to changes in the external load. Meanwhile, by using high-precision components such as sampling operational amplifier units, switching transistors, and sampling resistors, the circuit design is simplified, the number of circuit components is reduced, the size of the physiotherapy device is decreased, and the reliability and stability of the system are improved.

[0008] The above description is merely an overview of the technical solutions of the embodiments of this application. In order to better understand the technical means of the embodiments of this application and to implement them in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the embodiments of this application more obvious and understandable, specific implementation methods of this application are described below. Attached Figure Description

[0009] The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 A schematic diagram of the structure of the physiotherapy device proposed in the embodiments of this application is shown; Figure 2 A schematic diagram of the structure of the constant current drive current proposed in an embodiment of this application is shown; Figure 3 A circuit diagram of the constant current drive current proposed in an embodiment of this application is shown; Figure 4 A circuit diagram of the power supply unit proposed in an embodiment of this application is shown.

[0010] Figure label: 100. Power control section; 200. Drive section; 300. Signal transmission section; 400. Battery section; 110. Power supply unit; 211. First signal amplification unit; 212. First drive unit; 213. First contact; 214. Load detection unit; 221. First signal amplification unit; 222. First drive unit; 223. First contact; U1, First operational amplifier unit; U2, Second operational amplifier unit; U3, Third operational amplifier unit; U4, Fourth operational amplifier unit; U5, Fifth operational amplifier unit; Q1, First transistor; Q2, Second transistor; Q3, Third transistor; Q4, Fourth transistor; Q5, Fifth transistor; Q6, Sixth transistor; D3, Third diode; D4, Fourth diode; R4, First feedback resistor; R3, Second feedback resistor; R5, Third feedback resistor; R9, Fourth feedback resistor; R6, Fifth feedback resistor; R10, First pull-up resistor; R14, Second pull-up resistor; R13, Third pull-up resistor; R11, First sampling resistor; R12, Second sampling resistor; R1, First resistor; R2, Second resistor; R7, Seventh resistor; R8, Eighth resistor; RLoad, External load; CH1_P, External first contact; CH1_N, External second contact; U7, Reference Voltage Module; U8, Optocoupler Unit; U9, Power Drive Module; T1, Transformer; Q7, Field-Effect Transistor; D1, First Diode; D2, Second Diode; D5, Fifth Diode; R23, First Voltage Divider Resistor; R28, Second Voltage Divider Resistor; C1, First Filter Capacitor; C2, Second Filter Capacitor; C3, Third Filter Capacitor; C4, Fourth Filter Capacitor; R17, First Current-Limiting Resistor; R18, Second Current-Limiting Resistor; C13, Fourth Capacitor; R20, Fourth Pull-Up Resistor; R24, Sixth Feedback Resistor. Detailed Implementation

[0011] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0012] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0013] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0014] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0015] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A exists, A and B exist simultaneously, and B exists. In addition, the character " / " in this document generally indicates that the related objects before and after it have an "or" relationship.

[0016] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0017] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0018] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0019] To ensure stable voltage or current output, existing electrical stimulation devices typically employ constant voltage or constant current output. This is generally achieved through hardware DC-DC converters or hardware boost circuits, combined with software control for intensity adjustment. While this approach achieves constant current or voltage output to some extent, the complex circuitry results in a large device size, hindering miniaturization. Furthermore, software-based intensity adjustment leads to slow response times, poor constant current accuracy, and high software complexity, significantly impacting the user experience.

[0020] To address the aforementioned technical problems in the prior art, this application proposes a constant current drive circuit and a physiotherapy device. This application employs a single-pulse hardware closed-loop control circuit, adjusting the current output by acquiring real-time feedback of the stimulation current to achieve high-precision constant current control. In a specific implementation, the single-pulse control signal controls the magnitude and on / off state of the stimulation current through an operational amplifier unit and a switching transistor, stimulating an external load. When the resistance of the external load changes, the current flowing through it also changes. To capture this change, this application samples the stimulation current flowing through the external load at the back end, amplifies the sampled current through a set operational amplifier unit, and feeds the amplified current back to the operational amplifier unit through which the single-pulse control signal passes. After capturing the change in the feedback stimulation current, the operational amplifier unit controls the conduction level of the switching transistor by adjusting the output voltage, thereby adjusting the output magnitude of the stimulation current and maintaining a constant current output. This embodiment utilizes a single-pulse hardware closed-loop setup, eliminating the need for software sampling and control, thus reducing software complexity. Furthermore, it offers a faster response speed compared to software control, enabling real-time adjustment of the current output based on changes in the external load. Simultaneously, the use of high-precision components such as the sampling operational amplifier unit, switching transistors, and sampling resistors simplifies circuit design, reduces the number of circuit components, decreases the size of the physiotherapy device, and improves system reliability and stability.

[0021] It should be noted that the constant current driving circuit proposed in this application embodiment can be applied to electrical stimulation devices such as physiotherapy devices to control the output stimulation current, and can also be applied to other electronic devices that require constant current output. The application scenarios mentioned in this application embodiment should not be construed as limiting its application scenarios. This application embodiment only uses the application of the constant current driving circuit in a physiotherapy device as an example for illustration.

[0022] Figure 1 A schematic diagram of the physiotherapy device proposed in this application embodiment is shown. One such device typically provides two or more channels of electrical stimulation output. Each channel's electrical stimulation output includes two contacts for contact with the human body. Each channel includes mutually isolated power control section 100, drive section 200, signal transmission section 300, and battery section 400. It should be noted that these components can be shared between different channels or can be independent of each other, as long as they are isolated and do not interfere with each other. Since the circuit structure is identical across all channels, this application embodiment only uses one channel as an example for explanation.

[0023] like Figure 1As shown, the battery section 400 is mainly used to power the physiotherapy device, including a battery, charging chip, and boost chip, primarily for energy storage to facilitate the use of the physiotherapy device. Of course, some physiotherapy devices can also be directly connected to AC power or a power adapter via a plug; in this case, the battery section can be omitted. The power control section 100 includes a power driver chip, a transformer, and an LDO circuit. The power control section 100 mainly provides stable isolation voltage and current for the driving of different stimulation channels and the load. The power output from the transformer is amplified and provided to the physiotherapy device's driving circuit to provide a stable stimulation current to the external load. The driving circuit is connected to contacts, which make contact with the external load, such as the human body, to provide the stimulation current. The LDO provides operating voltage to the load detection section. The signal transmission section 300 provides isolated communication for each stimulation channel to avoid mutual interference. Different channels can communicate with the main control section wirelessly or via wired means to obtain physiotherapy data.

[0024] The constant current driving circuit proposed in this application embodiment is applied in the above-mentioned physiotherapy device, corresponding to the power control part 100 and the driving part 200 in the structure of the physiotherapy device. The specific module structure diagram of the constant current driving circuit proposed in this application embodiment is as follows: Figure 2 As shown.

[0025] Among them, the power supply unit 110 is from Figure 1 The battery section 400 in the power supply unit 110 receives external power input and forms different voltage output channels that are isolated from each other. It can provide stable power output to the outside through two or more channels and provide stable power to the driving circuits of different stimulation channels respectively.

[0026] Each stimulation channel includes two different constant current drive paths, each corresponding to a signal amplification unit, a drive unit, and a contact, used to provide stimulation current to an external load. Figure 2The first signal amplification unit 211, the first driving unit 212, and the first contact 213 are interconnected to form a first constant current driving path; the second signal amplification unit 221, the second driving unit 222, and the second contact 223 are interconnected to form a second constant current driving path. The control signal for the first constant current driving path is IN1, and the control signal for the second constant current driving path is IN2. Both IN1 and IN2 are single-pulse signals with opposite phases. The power supply unit 110 provides stimulation current to the first driving unit 212 and the second driving unit 222. The first control signal IN1 and the second control signal IN2 are used to provide control signals to the first driving unit 212 and the second driving unit 222 to adjust the stimulation current provided by the power supply unit 110. The load detection unit is used to detect the load status of the two paths to ensure that the circuit will not malfunction under no-load conditions, further improving the accuracy and reliability of constant current control. The first contact 213 and the second contact 223 are used to contact external loads respectively.

[0027] Figure 3 The diagram illustrates the circuit structure of the constant current drive circuit proposed in this application, including a first operational amplifier unit U1, a second operational amplifier unit U2, a first transistor Q1, and a second transistor Q2, wherein the first transistor Q1 and the second transistor Q2 have opposite polarities. It also includes a third operational amplifier unit U3, a fourth operational amplifier unit U4, a third transistor Q3, and a fourth transistor Q4, wherein the third transistor Q3 and the fourth transistor Q4 have opposite polarities. The operational amplifier units can be commonly used operational amplifiers; the first transistor Q1 and the third transistor Q3 can be NPN transistors; and the second transistor Q2 and the fourth transistor Q4 can be PNP transistors.

[0028] Continue to refer to Figure 3 , Figure 3 In the above, the first input terminal of the first operational amplifier unit U1 is used to receive the first control signal IN1, the first control signal IN1 being obtained through... Figure 1 The main control unit, such as a microcontroller, outputs a single-pulse control signal after DAC conversion. That is, the DAC circuit converts the control signal output by the microcontroller into an analog signal, which is then input to the first input terminal of the first operational amplifier unit U1. Figure 3 In this context, the first input terminal is a positive input terminal.

[0029] The second input terminal of the first operational amplifier unit U1 is connected to the output terminal of the first operational amplifier unit U1, and is connected to the base of the first transistor Q1 and the base of the second transistor Q2 through the output terminal of the first operational amplifier unit U1. The second input terminal is a negative input terminal. When the negative input terminal is connected to the output terminal, a voltage follower circuit structure is formed. When the negative input terminal receives a feedback signal from the fourth operational amplifier unit U4, the output terminal of the first operational amplifier unit U1 adjusts its output voltage according to the change in the feedback signal. This output voltage is used to control the on / off state of the first transistor Q1 and the second transistor Q2, respectively. Figure 3 In the first operational amplifier unit U1, the output terminal can be directly connected to the base of the second transistor Q2. In actual implementation, the output terminal of the first operational amplifier unit U1 can also be connected to the base of the second transistor Q2 through the fifth transistor Q5, which will be described later.

[0030] Continue to refer to Figure 3 The collector of the first transistor Q1 is connected to a power supply signal, wherein the power supply signal is... Figure 2 The constant voltage power supply signal output by the power supply unit 110 will be explained later. The emitter of the first transistor Q1 is electrically connected to the emitter of the second transistor Q2, and its emitter is also connected to an external first contact CH1_P. The external first contact CH1_P is connected to an external load RLoad. In this application, the external load RLoad can be a human body with an internal resistance of 500R. The first transistor Q1 is turned on or off under the control of the output voltage of the first operational amplifier unit U1, and can have different conduction degrees according to the output voltage of the first operational amplifier unit U1, thereby controlling the magnitude of the stimulation current of the power supply signal PWR_VCC1 supplied by the power supply flowing through the first transistor Q1.

[0031] Since the first transistor Q1 and the second transistor Q2 have opposite polarities, assuming the first transistor Q1 is an NPN transistor and the second transistor Q2 is a PNP transistor, when the first operational amplifier unit U1 outputs a high-level signal, the first transistor Q1 is in the on state and the second transistor Q2 is in the off state. At this time, the power supply signal PWR_VCC1 flows through the first transistor Q1 and the external first contact CH1_P through the external load RLoad. When the first operational amplifier unit U1 outputs a low-level signal, the first transistor Q1 is in the off state and the second transistor Q2 is in the on state. Then, the stimulation current flowing from the external second contact CH1_N through the external load RLoad flows through the second transistor Q2.

[0032] The collector of the second transistor Q2 is electrically connected to the first input terminal of the second operational amplifier unit U2; the output terminal of the second operational amplifier unit U2 is connected to its second input terminal, used to amplify the input signal at its first input terminal, and send the amplified signal to the second input terminal of the third operational amplifier unit U3. Wherein, in Figure 3 In this configuration, the first input terminal is a positive input terminal, and the second input terminal is a negative input terminal. The second operational amplifier unit U2 is used to sample and amplify the stimulation current flowing through the third transistor Q3 and the second transistor Q2 through the external load RLoad, and then input it as a sampling feedback signal to the third operational amplifier unit U3.

[0033] The first input terminal of the third operational amplifier unit U3 is used to receive the second control signal IN2, wherein the second control signal IN2 is also... Figure 1 The control signal output by the main control section is converted by a DAC to generate a single-pulse control signal. The first control signal IN1 and the second control signal IN2 are out of phase, the purpose of which is to alternately turn on the first transistor Q1 and the third transistor Q3, thereby causing the external first contact CH1_P and the external second contact CH1_N to alternately output stimulation current. That is, when the first transistor Q1 is on, the third transistor Q3 is off, and the power signal PWR_VCC1 flows from the first transistor Q1 through the external load RLoad and forms a loop through the fourth transistor Q4; when the first transistor Q1 is off, the third transistor Q3 is on, and the power signal PWR_VCC1 flows from the third transistor Q3 through the external load RLoad and forms a loop through the second transistor Q2.

[0034] The output terminal of the third operational amplifier unit U3 is connected to its second input terminal. The third operational amplifier unit U3 is used to adjust the second control signal IN2 according to the amplified signal output by the second operational amplifier unit U2, and output the adjusted second control signal to the base of the third transistor Q3 and the base of the fourth transistor Q4. The collector of the third transistor Q3 is connected to the power supply signal, its emitter is connected to the emitter of the fourth transistor Q4, and its emitter is also connected to the external second contact CH1_N. Figure 3In this embodiment, the first input terminal of the third operational amplifier unit U3 is a positive input terminal, and the second input terminal is a negative input terminal. Since the third transistor Q3 and the fourth transistor Q4 have opposite polarities, in this embodiment, the third transistor Q3 can be an NPN transistor, and the fourth transistor Q4 can be a PNP transistor. When the third operational amplifier unit U3 outputs a high-level signal, the third transistor Q3 is in the conducting state, and the fourth transistor Q4 is in the off state. That is, the stimulation current provided by the power supply signal PWR_VCC1 flows through the third transistor Q3 through the external load RLoad and the second transistor Q2. Since the first control signal IN1 and the second control signal IN2 are single-pulse signals with opposite phases, when the third operational amplifier unit U3 provides a high-level signal, the first operational amplifier unit U1 provides a low-level signal. The third transistor Q3 is turned on, and the second transistor Q2 is also turned on. The stimulation current provided by the power supply signal PWR_VCC1 passes through the third transistor Q3, the external second contact CH1_N, the external first contact CH1_P, and the second transistor Q2, and then passes through the first sampling resistor R11 to form a sampling feedback signal, which is input to the positive input terminal of the second operational amplifier unit U2. The second operational amplifier unit U2 amplifies the sampling feedback signal and inputs it to the negative input terminal of the third operational amplifier unit U3. The third operational amplifier unit U3 adjusts the voltage signal output by detecting the difference between the sampling feedback signal and the second control signal IN2, so as to adjust the conduction degree of the third transistor Q3, thereby achieving the purpose of controlling the current flowing through the third transistor Q3, so that the stimulation current flowing through the external load RLoad is in a stable state.

[0035] Continue to refer to Figure 3 The collector of the fourth transistor Q4 is electrically connected to the first input terminal of the fourth operational amplifier unit U4; the output terminal of the fourth operational amplifier unit U4 is connected to its second input terminal, used to amplify the input signal at its first input terminal, and send the amplified signal to the second input terminal of the first operational amplifier unit U1, so that the first operational amplifier unit U1 adjusts the first control signal IN1 according to the amplified signal, and outputs the adjusted first control signal to the base of the first transistor Q1 and the base of the second transistor Q2. Figure 3 In the above, the first input terminal of the fourth operational amplifier unit U4 is a positive input terminal, and the second input terminal is a negative input terminal. Figure 3In this configuration, the output of the third operational amplifier unit U3 can be directly connected to the base of the fourth transistor Q4. In actual implementation, the output of the third operational amplifier unit U3 can also be connected to the base of the fourth transistor Q4 via the sixth transistor Q6, which will be described later. Similarly, since the first control signal IN1 and the second control signal IN2 are single-pulse signals with opposite phases, when the first operational amplifier unit U1 provides a high-level signal, the third operational amplifier unit U3 provides a low-level signal. The first transistor Q1 is turned on, the second transistor Q2 is turned off, the fourth transistor Q4 is turned on, and the third transistor Q3 is turned off. Therefore, the stimulation current provided by the power supply signal PWR_VCC1 passes through the first transistor Q1, the external first contact CH1_P, the external second contact CH2_N, and the fourth transistor Q4, and then passes through the second sampling resistor. R12 forms a sampling feedback signal and is input to the positive input terminal of the fourth operational amplifier unit U4. The fourth operational amplifier unit U4 amplifies the sampling feedback signal and inputs it to the negative input terminal of the first operational amplifier unit U1. The first operational amplifier unit U1 adjusts the voltage signal output by detecting the difference between the sampling feedback signal and the first control signal IN1, so as to adjust the conduction degree of the first transistor Q1, thereby controlling the current flowing through the first transistor Q1 and keeping the stimulation current flowing through the external load RLoad in a stable state.

[0036] The constant current driving circuit provided in this application embodiment can achieve closed-loop feedback of the change when the external load RLoad between the external first contact CH1_P and the external second contact CH1_N changes. By following the change of the external load RLoad, the conduction degree of the switching transistor is controlled, thereby realizing the current following adjustment and thus realizing the constant current closed loop.

[0037] Figure 3In the first operational amplifier unit U1, when the first constant current path is in the output state, the first control signal IN1 is high and the second control signal IN2 is low. At this time, the output of the first operational amplifier U1 outputs a high-level signal, the first transistor Q1 is in the conducting state, the second transistor Q2 is in the off state, the third transistor Q3 is in the off state, and the fourth transistor Q4 is in the conducting state. Simultaneously, the power supply signal PWR_VCC1 outputs a stimulation current through the first transistor Q1, the external first contact CH1_P, the external load RLoad, the external second contact CH2_N, and the fourth transistor Q4. At the same time, a sampling feedback signal is output to the fourth operational amplifier unit U4 through the second sampling resistor R12. The fourth operational amplifier unit U4 amplifies the sampling feedback signal and outputs it to the negative input terminal of the first operational amplifier unit U1. The first operational amplifier unit U1 compares the first control signal IN1 at the positive input terminal with the sampling feedback signal and outputs an adjusted voltage signal to adjust the conduction level of the first transistor Q1, thereby achieving closed-loop control. When the external load RLoad remains unchanged, the voltage difference between the sampling feedback signal and the first control signal IN1 remains unchanged, and the voltage signal output from the output terminal of the first operational amplifier unit U1 remains unchanged. Therefore, the current flowing through the first transistor Q1 is stable. When the external load RLoad decreases, the current flowing through it increases, leading to an increase in the current flowing through the second sampling resistor R12. This results in a larger sampling feedback signal output to the fourth operational amplifier unit U4, which in turn increases the voltage output to the negative input terminal of the first operational amplifier unit U1. Consequently, the voltage difference between the first control signal IN1 and the sampling feedback signal at the positive input terminal of the first operational amplifier unit U1 decreases, and the voltage output from the output terminal of the first operational amplifier unit U1 also decreases. This reduces the conduction level of the first transistor Q1, and the current flowing through the external load RLoad from the power signal PWR_VCC1 also decreases, ultimately achieving a constant current closed loop. When the external load RLoad increases, the current flowing through it decreases, which in turn reduces the current flowing through the second sampling resistor R12. This results in a smaller sampling feedback signal output to the fourth operational amplifier unit U4, which in turn reduces the voltage output to the negative input terminal of the first operational amplifier unit U1. Consequently, the voltage difference between the first control signal IN1 and the sampling feedback signal at the positive input terminal of the first operational amplifier unit U1 increases, leading to a corresponding increase in the output voltage of the first operational amplifier unit U1. This increases the conduction level of the first transistor Q1, and the current flowing through the external load RLoad from the power supply signal PWR_VCC1 also increases, ultimately achieving a constant current closed loop.

[0038] Similarly, Figure 3In this context, when the second constant current path is in the output state, its working state is the same as that of the first constant current path, which will not be elaborated here.

[0039] In summary, the constant current drive circuit proposed in this application requires no software sampling and control, reducing software complexity. Compared to software control, it offers a faster response speed, adjusting the current output in real time according to changes in the external load RLoad. This simplifies circuit design, reduces the number of circuit components, and simplifies the circuit structure, decreasing the size of the physiotherapy device while improving system reliability and stability. Using a 500R load resistor (the internal resistance of the human body is 500R), the constant current drive circuit proposed in this application achieves a constant current accuracy of ±20uA. It eliminates the need for software sampling and control, high-performance main control chips, high-precision software sampling, and complex control logic, thus realizing a low-cost, high-precision solution.

[0040] Continue to refer to Figure 3 To improve the voltage tracking sensitivity of the first operational amplifier unit U1 and the third operational amplifier unit U3, a first feedback resistor R4 and a second feedback resistor R3 are also provided. One end of the first feedback resistor R4 is connected to the inverting input terminal of the first operational amplifier unit U1, and the other end is connected to the output terminal of the first operational amplifier unit U1. The output terminal of the first operational amplifier unit U1 is connected to the base of the first transistor Q1 through the first resistor R1. One end of the second feedback resistor R3 is connected to the inverting input terminal of the third operational amplifier unit U3, and the other end is connected to the output terminal of the first operational amplifier unit U1. The output terminal of the third operational amplifier unit U3 is connected to the base of the third transistor Q3 through the second resistor R2. In this way, the tracking sensitivity of the first operational amplifier unit U1 and the third operational amplifier unit U3 is higher, greatly improving the accuracy of the constant current.

[0041] Continue to refer to Figure 3 In order to better generate the sampling feedback signal and prevent current backflow, a seventh resistor R7, a third diode D3 and a first sampling resistor R11 are also provided in the first constant current path; an eighth resistor R8, a fourth diode D4 and a second sampling resistor R12 are also provided in the second constant current path.

[0042] The collector of the second transistor Q2 is connected to the positive terminal of the third diode D3 through the seventh resistor R7. The negative terminal of the third diode D3 is connected to one end of the first sampling resistor R11 and is also electrically connected to the positive input terminal of the second operational amplifier unit U2. The other end of the first sampling resistor R11 is grounded.

[0043] The collector of the fourth transistor Q4 is connected to the positive terminal of the fourth diode D4 through the eighth resistor R8. The negative terminal of the fourth diode D4 is connected to one end of the second sampling resistor R12 and is also electrically connected to the positive input terminal of the fourth operational amplifier unit U4. The other end of the second sampling resistor R12 is grounded.

[0044] In this way, the constant current drive circuit can accurately control and detect the load current, achieving high-precision constant current control.

[0045] In some embodiments of this application, in order to better amplify the sampling feedback signal generated by the sampling resistor, the negative input terminal of the second operational amplifier unit U2 is connected to one end of the fourth feedback resistor R9 and the second pull-up resistor R14, respectively; one end of the fourth feedback resistor R9 is connected to the output terminal of the second operational amplifier unit U2; and the other end of the second pull-up resistor R14 is grounded. The negative input terminal of the fourth operational amplifier unit U4 is connected to one end of the fifth feedback resistor R6 and the third pull-up resistor R13, respectively; one end of the fifth feedback resistor R6 is connected to the output terminal of the fourth operational amplifier unit U4; and the other end of the third pull-up resistor R13 is grounded.

[0046] In the above embodiments, the second operational amplifier U2 and the fourth amplifier U4 are used to amplify the voltage changes across the first sampling resistor R11 and the second sampling resistor R12. The fifth feedback resistor R6 and the third pull-up resistor R13 form a feedback network connected to the input and output terminals of the fourth operational amplifier unit U4. The fourth feedback resistor R9 and the second pull-up resistor R14 form a feedback network connected to the input and output terminals of the second operational amplifier unit U2. This feedback network design helps improve amplification accuracy and stability, and reduces the error between the set current value and the detected value.

[0047] In other embodiments, to reduce the leakage of base current in the second transistor Q2 and the fourth transistor Q4 and improve the current control accuracy, such as... Figure 3 As shown, the circuit further includes a fifth transistor Q5 and a sixth transistor Q6. The fifth transistor Q5 has the same polarity as the second transistor Q2, and the sixth transistor Q6 has the same polarity as the fourth transistor Q4. The base of the fifth transistor Q5 is connected to the output terminal of the first operational amplifier unit U1, its emitter is connected to the base of the second transistor Q2, and its collector is connected to the collector of the second transistor Q2. The base of the sixth transistor Q6 is connected to the output terminal of the third operational amplifier unit U3, its emitter is connected to the base of the fourth transistor Q4, and its collector is connected to the collector of the fourth transistor Q4.

[0048] Since a transistor requires a certain amount of base current to maintain conduction, there will be a difference of approximately one base current between the constant current in the main circuit and the set constant current. To reduce the error between the set value and the actual value, in the first constant current circuit of this application, the second transistor Q2 and the fifth transistor Q5 form a cascaded structure. The base of the fifth transistor Q5 is connected to the emitter of the second transistor Q2 through the first transistor Q1, while the emitter of the fifth transistor Q5 is connected to the base of the second transistor Q2. When current flows through the second transistor Q2 and the fifth transistor Q5, the base current flowing through the fifth transistor Q5 will become 1 / β times the original current (β is the DC gain of the transistor), thereby reducing the base current leakage of the second transistor Q2, reducing the error of current control, and improving the accuracy of current control.

[0049] Similarly, in the second constant current path, the fourth transistor Q4 and the sixth transistor Q6 form a cascaded structure. The base of the sixth transistor Q6 is connected to the emitter of the fourth transistor Q4 through the third transistor Q3, while the emitter of the sixth transistor Q6 is connected to the base of the fourth transistor Q4. When current flows through the second transistor Q4 and the fifth transistor Q6, the base current flowing through the fifth transistor Q6 will become 1 / β times the original current (β is the DC gain of the transistor), thereby reducing the base current leakage of the fourth transistor Q4, reducing the error of current control, and improving the accuracy of current control.

[0050] Furthermore, to detect the no-load condition of the external load RLoad, a fifth operational amplifier unit U5 is provided in this embodiment to detect the no-load condition of the load. The positive input terminal of the fifth operational amplifier unit U5 is connected to the collector of the fourth transistor Q4, and its first input terminal is connected to one end of the third feedback resistor R5 and one end of the first pull-up resistor R10, respectively; one end of the third feedback resistor R5 is connected to the output terminal of the fifth operational amplifier unit U5; and the other end of the first pull-up resistor R10 is grounded.

[0051] The fifth operational amplifier unit U5 can be located in either the first or second constant current path to detect the no-load condition of the load. Therefore, the positive input terminal of the fifth operational amplifier unit U5 can also be connected to the collector of the second transistor Q2, and its negative input terminal is connected to one end of the third feedback resistor R5 and one end of the first pull-up resistor R10, respectively; one end of the third feedback resistor R5 is connected to the output terminal of the fifth operational amplifier unit U5; and the other end of the first pull-up resistor R10 is grounded.

[0052] When there is no load between the external first contact CH1_P and the external second contact CH1_N, the second transistor Q2 or the fourth transistor Q4 is in the off state, and the third diode D3 or the fourth diode D4 is also in the off state. No current flows through the first sampling resistor R11 or the second sampling resistor R12. At this time, the first sampling resistor R11 or the second sampling resistor R12 outputs a low-level signal, and the output terminal CH1_CHECK of the fifth amplification unit U5 is a low-level signal. When the external first contact CH1_P and the external second contact CH1_N are connected to an external load, the second transistor Q2 or the fourth transistor Q4 is in the on state, and current flows through the first sampling resistor R11 or the second sampling resistor R12. Due to the forward voltage drop of the third diode D3 or the fourth diode D4, the voltage sampled at this point is the sum of the forward voltage drop of the third diode D3 or the fourth diode D4 and the voltage drop across the first sampling resistor R11 or the second sampling resistor R12. After amplification by the fifth amplification unit U5, the output is saturated and output as a high-level signal. Therefore, when the main control unit reads the output signal CH1_CHECK as low, it indicates that the system is unloaded; when it reads the output signal CH1_CHECK as high, it indicates that the system is outputting to an external load. This application solves the problem of insufficient detection accuracy for low-end loads by detecting at the low end. When in an unloaded state, the main control unit turns off the power signal output, avoiding electric shock caused by no-load operation and greatly improving the user experience.

[0053] Furthermore, in some embodiments, to enable the constant current drive current to have a more stable constant current output, embodiments of this application also propose a dual-channel isolated power supply unit 110, such as... Figure 4 As shown, through Figure 4 The power supply unit 110 shown is capable of providing a stable isolated power output to the signal amplification unit and the drive unit.

[0054] Figure 4 In the power supply unit 110, there are a power drive module U9, a field-effect transistor Q7, a transformer T1, a fifth diode D5, and an optocoupler unit U8.

[0055] The control port of the power drive module U9 is connected to the gate of the field-effect transistor Q7, and is used to control the switching of the field-effect transistor Q7. The drain of the field-effect transistor Q7 is connected to the opposite terminal of the primary winding of the transformer T1, and the source of the field-effect transistor Q7 is connected to the fourth pull-up resistor R20 and then grounded. The source of the field-effect transistor Q7 is also electrically connected to the overcurrent protection pin ISEN of the power drive module U9 through the sixth feedback resistor R24, and is used to sample the overcurrent current of the field-effect transistor Q7. The power drive module U9 controls the switching state of the field-effect transistor Q7 to realize energy transfer and output voltage regulation. Based on the voltage input of the feedback pin, it adjusts the duty cycle of the output voltage, thereby controlling the on / off time of the field-effect transistor Q7, and thus regulating the voltage output of the transformer T1. The power drive module U9 includes a power supply terminal VCC, a control port OUT, and a feedback terminal VFB. The power supply terminal is connected to an external power source, and the duty cycle of the output voltage output through the control port OUT is controlled by the feedback signal input through the feedback terminal VFB. Simultaneously, the power drive module U9, in conjunction with the transformer T1, achieves high power isolation, ensuring electrical safety isolation between high-voltage and low-voltage stages.

[0056] Continue to refer to Figure 4 The primary winding of transformer T1 is connected to the external power source at the same terminal. The external power source can be... Figure 1 The battery section 400 outputs; the same-name terminal of the primary winding of the transformer T1 is also connected to the negative terminal of the fifth diode D5, and the opposite-name terminal of its primary winding is also connected to the positive terminal of the fifth diode D5; the output terminal of the first secondary winding of the transformer T1 outputs the power signal PWR_VCC1.

[0057] exist Figure 4 In this transformer T1, a flyback topology is used, which features small size and high isolation. When the power drive module U9 outputs a high-level signal, the field-effect transistor Q7 is in the on state, and the fifth diode D5 is in the off state. The inductance of the primary winding of the transformer T1 begins to charge, and at this time, the secondary winding has no output. When the field-effect transistor Q7 is turned off, the charging of the primary winding ends, and the inductance of the primary winding couples energy to the secondary winding through the magnetic core. The first and second secondary windings discharge outwards through the first diode D1 and the second diode D2, respectively, outputting power signals PWR_VCC1 and PWR_VCC2. The output terminals of the transformer T1 are respectively equipped with a first filter capacitor C1, a second filter capacitor C2, a third filter capacitor C3, and a fourth filter capacitor C4 connected in parallel to filter the output power signals. Figure 4Since the power signals PWR_VCC1 and PWR_VCC2 are isolated from each other and have the same circuit structure, in this embodiment, only the output of the power signal PWR_VCC1 is used as an example for explanation.

[0058] In the power supply unit 110, the positive terminal of the optocoupler unit U8 is connected to the output terminal of the first secondary winding of the transformer T1, and its emitter is electrically connected to the feedback terminal of the power drive module U9. The optocoupler unit U8 is an electronic component that uses optical signals to achieve electrical isolation, typically consisting of a light-emitting diode (LED) and a photosensitive element (such as a phototransistor or photodiode). Figure 4 As shown, the optocoupler unit U8 includes a positive pin 1, which is connected to the power signal PWR_VCC1 through a first current-limiting resistor R17 to provide forward current to the light-emitting diode. The negative pin 2 of the optocoupler unit U8 is grounded, its collector pin 4 is connected to the power supply, and its emitter pin 3 is electrically connected to the feedback terminal VFB of the power drive module U9. When the phototransistor receives a light signal, a current path is formed between the emitter pin 3 and the collector pin 4, and a current signal is output through the emitter pin 3. The current signal output by the emitter pin 3 of the optocoupler unit U8 will change according to the strength of the power signal PWR_VCC1. Therefore, the optocoupler unit U8 is used to generate a feedback signal to the power drive module U9 according to the strength of the power signal PWR_VCC1. The power drive module U9 adjusts the duty cycle of the output signal of the control port according to the input signal of its feedback terminal, thereby controlling the on / off time of the field effect transistor Q7 to control the output voltage of the transformer T1 and realize closed-loop control of the output power signal PWR_VCC1.

[0059] exist Figure 4 During system operation, when the power signal PWR_VCC1 output by transformer T1 is decreasing, the current between the positive pin 1 and the negative pin 2 of optocoupler unit U8 decreases. Consequently, the output voltage of optocoupler unit U8 decreases with the decrease in input current, thus inputting a decreasing feedback signal to the feedback terminal VFB of power drive module U9. As the feedback signal voltage decreases, power drive module U9 increases the duty cycle of the output voltage signal, thereby controlling the increase in the output voltage output to field-effect transistor Q7. The increased output voltage leads to an increase in the conduction time of field-effect transistor Q7, which in turn increases the charging time of the primary winding of transformer T1, thereby increasing the output voltage of the secondary winding of transformer T1. In other words, the power signal PWR_VCC1 gradually increases.

[0060] When the power signal PWR_VCC1 is increasing, the current between the positive pin 1 and the negative pin 2 of the optocoupler unit U8 increases. As a result, the output voltage of the optocoupler unit U8 increases with the increase of the input current, which means that a gradually increasing feedback signal is input to the feedback terminal VFB of the power drive module U9. As the feedback signal voltage increases, the power drive module U9 gradually reduces the duty cycle of the output voltage signal, thereby controlling the reduction of the output voltage to the field-effect transistor Q7. As the output voltage decreases, the conduction time of the field-effect transistor Q7 decreases, thereby reducing the charging time of the primary winding of the transformer T1, and further reducing the output voltage of the secondary winding of the transformer T1. That is, the power signal PWR_VCC1 gradually decreases.

[0061] Through the above power output feedback and control process, closed-loop control of voltage output can be achieved, enabling the power supply unit 110 to output a stable power signal to the drive unit, further improving the constant current output effect of the constant current drive circuit.

[0062] In some embodiments, to more accurately detect changes in the power supply signal PWR_VCC1, this application embodiment also provides a reference voltage for comparison for the optocoupler unit U8, such as... Figure 4 As shown, the power supply unit 110 further includes a first voltage divider resistor R23, a second voltage divider resistor R28, and a reference voltage module U7. One end of the first voltage divider resistor R23 is connected to the output terminal of the first secondary winding of the transformer T1, and the other end of the first voltage divider resistor R23 is connected to the input terminal of the second voltage divider resistor R28 and the reference voltage module U7, respectively. The other end of the second voltage divider resistor R28 is grounded. The output terminal of the reference voltage module U7 is connected to the negative terminal of the optocoupler unit U8.

[0063] The reference voltage module U7 provides a stable reference voltage for voltage comparison and feedback adjustment in closed-loop control. Figure 4In this process, the output power signal PWR_VCC1 is divided by a first voltage divider resistor R23 and a second voltage divider resistor R28. The divided voltage is then connected to the negative input terminal of the optocoupler unit U8. The output power signal PWR_VCC1 is compared with the reference voltage provided by the reference voltage module U7. If the output voltage PWR_VCC1 decreases, the divided voltage also decreases; if the output voltage PWR_VCC1 increases, the divided voltage also increases. The change in the divided voltage causes a change in the current between the positive pin 1 and the negative pin 2 of the optocoupler unit U8. When the divided voltage decreases, the current between the positive pin 1 and the negative pin 2 of the optocoupler unit U8 decreases; when the divided voltage increases, the current between the positive pin 1 and the negative pin 2 of the optocoupler unit U8 increases. Therefore, by setting the reference voltage module U7 to provide a stable voltage for the feedback detection of the power signal PWR_VCC1, the feedback effect is improved, and the accuracy of voltage output regulation is increased.

[0064] In summary, the power supply unit provided in this embodiment achieves closed-loop detection of the output power signal by incorporating a power drive module, a field-effect transistor, and an optocoupler unit. This allows the power supply unit to automatically adjust according to increases or decreases in the output power signal, ensuring its stability and providing a stable voltage output to the constant current drive circuit. This approach features a simple circuit structure, high voltage adjustment sensitivity, and excellent isolation. Furthermore, the inclusion of a reference voltage module provides a stable reference voltage for voltage feedback detection, improving the feedback effect and increasing the accuracy of voltage output regulation.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A constant current drive circuit, characterized in that, The circuit includes a first operational amplifier unit, a second operational amplifier unit, a first transistor, and a second transistor, wherein the first transistor and the second transistor have opposite polarities; it also includes a third operational amplifier unit, a fourth operational amplifier unit, a third transistor, and a fourth transistor, wherein the third transistor and the fourth transistor have opposite polarities; The first input terminal of the first operational amplifier unit is used to receive a first control signal. The second input terminal of the first operational amplifier unit is connected to its output terminal, and its output terminal is connected to the base of the first transistor and the base of the second transistor respectively. The collector of the first transistor is connected to a power supply signal, its emitter is electrically connected to the emitter of the second transistor, and its emitter is also connected to an external first contact. The collector of the second transistor is electrically connected to the first input terminal of the second operational amplifier unit. The output terminal of the second operational amplifier unit is connected to its second input terminal to amplify the input signal at its first input terminal and send the amplified signal to the second input terminal of the third operational amplifier unit. The first input terminal of the third operational amplifier unit is used to receive a second control signal, wherein the first control signal and the second control signal are pulse signals with opposite phases. The output terminal of the third operational amplifier unit is connected to its second input terminal. The third operational amplifier unit is used to adjust the second control signal according to the amplified signal output by the second operational amplifier unit, and output the adjusted second control signal to the base of the third transistor and the base of the fourth transistor. The collector of the third transistor is connected to a power supply signal, its emitter is connected to the emitter of the fourth transistor, and its emitter is also connected to an external second contact. The collector of the fourth transistor is electrically connected to the first input terminal of the fourth operational amplifier unit. The output terminal of the fourth operational amplifier unit is connected to its second input terminal, used to amplify the input signal at its first input terminal, and send the amplified signal to the second input terminal of the first operational amplifier unit, so that the first operational amplifier unit adjusts the first control signal according to the amplified signal, and outputs the adjusted first control signal to the base of the first transistor and the base of the second transistor.

2. The constant current drive circuit according to claim 1, characterized in that, It also includes a first feedback resistor and a second feedback resistor; One end of the first feedback resistor is connected to the inverting input terminal of the first operational amplifier unit, and the other end is connected to the output terminal of the first operational amplifier unit. One end of the second feedback resistor is connected to the inverting input terminal of the third operational amplifier unit, and the other end is connected to the output terminal of the first operational amplifier unit.

3. The constant current drive circuit according to claim 1, characterized in that, The circuit also includes a first sampling resistor and a second sampling resistor; One end of the first sampling resistor is electrically connected to the collector of the second transistor and the positive input terminal of the second operational amplifier unit, and the other end of the first sampling resistor is grounded. One end of the second sampling resistor is electrically connected to the collector of the fourth transistor and the positive input terminal of the fourth operational amplifier unit, and the other end of the second sampling resistor is grounded.

4. The constant current drive circuit according to claim 3, characterized in that, It also includes a third diode and a fourth diode; The positive terminal of the third diode is connected to the collector of the second transistor, and its negative terminal is connected to the first sampling resistor. The positive terminal of the fourth diode is connected to the collector of the fourth transistor, and its negative terminal is connected to the second sampling resistor.

5. The constant current drive circuit according to claim 1, characterized in that, The negative input terminal of the second operational amplifier unit is connected to one end of the fourth feedback resistor and the second pull-up resistor, respectively; one end of the fourth feedback resistor is connected to the output terminal of the second operational amplifier unit; and the other end of the second pull-up resistor is grounded. The negative input terminal of the fourth operational amplifier unit is connected to one end of the fifth feedback resistor and one end of the third pull-up resistor, respectively; one end of the fifth feedback resistor is connected to the output terminal of the fourth operational amplifier unit; and the other end of the third pull-up resistor is grounded.

6. The constant current drive circuit according to any one of claims 1-5, characterized in that, The circuit also includes a fifth transistor and a sixth transistor, wherein the fifth transistor has the same polarity as the second transistor, and the sixth transistor has the same polarity as the fourth transistor; The base of the fifth transistor is connected to the output terminal of the first operational amplifier unit, its emitter is connected to the base of the second transistor, and its collector is connected to the collector of the second transistor. The base of the sixth transistor is connected to the output terminal of the third operational amplifier unit, its emitter is connected to the base of the fourth transistor, and its collector is connected to the collector of the fourth transistor.

7. The constant current drive circuit according to claim 6, characterized in that, It also includes a fifth operational amplifier unit; The positive input terminal of the fifth operational amplifier unit is connected to the collector of the fourth transistor, and its negative input terminal is connected to one end of the third feedback resistor and one end of the first pull-up resistor, respectively; one end of the third feedback resistor is connected to the output terminal of the fifth operational amplifier unit; the other end of the first pull-up resistor is grounded. or, The positive input terminal of the fifth operational amplifier unit is connected to the collector of the second transistor, and its negative input terminal is connected to one end of the third feedback resistor and one end of the first pull-up resistor, respectively; one end of the third feedback resistor is connected to the output terminal of the fifth operational amplifier unit; and the other end of the first pull-up resistor is grounded.

8. The constant current drive circuit according to claim 1, characterized in that, It also includes a power supply unit; The power supply unit includes a power drive module, a field-effect transistor, a transformer, and an optocoupler unit; The control port of the power drive module is connected to the gate of the field-effect transistor and is used to control the conduction and disconnection of the field-effect transistor. The drain of the field-effect transistor is connected to the opposite terminal of the primary winding of the transformer. The primary winding of the transformer is connected to the external power source at the same terminal; the output terminal of the first secondary winding of the transformer outputs the power signal. The positive terminal of the optocoupler unit is connected to the output terminal of the first secondary winding of the transformer, and its emitter is electrically connected to the feedback terminal of the power drive module. The power drive module is also used to adjust the duty cycle of the output signal of the control port according to the input signal of its feedback terminal, thereby controlling the on and off time of the field-effect transistor to control the output voltage of the transformer.

9. The constant current drive circuit according to claim 8, characterized in that, The power supply unit also includes a first voltage divider resistor, a second voltage divider resistor, and a reference voltage module; One end of the first voltage divider resistor is connected to the output terminal of the first secondary winding of the transformer, and the other end of the first voltage divider resistor is connected to the second voltage divider resistor and the input terminal of the reference voltage module, respectively. The other end of the second voltage divider resistor is grounded. The output terminal of the reference voltage module is connected to the negative terminal of the optocoupler unit.

10. A physiotherapy device, characterized in that, Includes the constant current drive current, the first contact, and the second contact as described in any one of claims 1-9; The first and second contacts are used to make contact with an external load.

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