Constant current source and constant current source circuit board

Abstract

The embodiment of the invention provides a constant current source and a constant current source circuit board. The constant current source comprises an isolation power supply module, an isolation CAN communication module, a single-chip microcomputer control module, a sampling module and a constant current control module. Wherein the isolation power supply module comprises a power supply conversion module and an optocoupler controller, and the input end and the output end of the power supply conversion module are electrically isolated by the power supply conversion module; the input end of the power conversion module is connected with the output end of the power supply device, so that the on-off of the power conversion module is controlled by the singlechip control module; the isolated CAN communication module comprises an isolated CAN transceiver and a CAN bus protection circuit; the constant-current control module is connected with the isolation power supply module and performs output based on a preset value; the sampling module is arranged at the output end of the constant-current control module and used for obtaining the current value of the output end of the constant-current control module, and the single-chip microcomputer control module adjusts the output of the constant-current control module to a preset value at least based on the current value in a feedback mode.

Description

Technical Field

[0001] The present application relates to the technical field of current control, and in particular to a constant current source and a constant current source circuit board. Background Art

[0002] In the existing constant current source technology, facing the complex electromagnetic environment, its reliability and anti-interference ability are often low. In the existing technology, the constant current source is easily affected by external electromagnetic interference, resulting in unstable output current and unable to accurately maintain the preset value.

[0003] Therefore, a constant current source with stronger anti-interference ability is urgently needed. Summary of the invention

[0004] In order to overcome the above defects, the present invention is proposed to solve or at least partially solve the problem of poor anti-interference ability of the constant current source in the prior art.

[0005] In the first aspect, an embodiment of the present application provides a constant current source, which includes: an isolated power supply module, an isolated CAN communication module, a single-chip microcomputer control module, a sampling module and a constant current control module; wherein the isolated power supply module includes a power conversion module and an optocoupler controller, the input end of the power conversion module is the input end of the isolated power supply module, the output end of the power conversion module is the output end of the isolated power supply module, and the power conversion module electrically isolates the input end and the output end of the power conversion module; the input end of the power conversion module is connected to the output end of the power supply device, the output end of the power conversion module is connected to the constant current control module, and the control end of the power conversion module is connected to the single-chip microcomputer control module through the optocoupler controller. , so that the opening and closing of the power conversion module is controlled by the single-chip control module; the isolated CAN communication module includes an isolated CAN transceiver and a CAN bus protection circuit: wherein the isolated CAN transceiver isolates the primary side and the secondary side of the isolated CAN transceiver, the primary side is connected to the single-chip control module, and the secondary side is connected to the host computer through the CAN bus protection circuit and the CAN bus; the constant current control module is connected to the isolated power supply module and outputs based on a preset value; the sampling module is arranged at the output end of the constant current control module, and is used to obtain the current value of the output end of the constant current control module, and the single-chip control module adjusts the output of the constant current control module to a preset value by feedback at least based on the current value.

[0006] As an alternative or supplement to the above scheme, in a method according to an embodiment of the present invention, the isolated CAN transceiver includes a transformer driver, a rectifier module, a signal isolation module and a signal conversion module; wherein the transformer driver obtains a DC signal and converts the DC signal into a high-frequency signal and inputs it into the primary winding of the transformer, and the secondary winding of the transformer is connected to the rectifier module. The rectifier module obtains the output voltage of the secondary winding of the transformer and outputs a DC voltage through the rectifier module, wherein the DC voltage is used to power the signal isolation module and the signal conversion module; one end of the signal isolation module is connected to the single-chip control module as the primary side of the isolated CAN transceiver, and the other end is connected to the first end of the signal conversion module, and the second end of the signal conversion module is used as the secondary side of the isolated CAN transceiver, wherein the signal isolation module is used to electrically isolate the received and transmitted signals, and the signal conversion module converts the CAN signal on the CAN bus into a logic level signal, wherein the logic level signal is a signal that the single-chip control module can directly understand.

[0007] As an alternative or supplement to the above scheme, in a method according to an embodiment of the present invention, the CAN bus protection circuit includes: a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a TVS tube, a common mode inductor and a terminal resistor; the common mode inductor includes: port 1, port 2, port 3 and port 4, wherein port 1 and port 2 are connected to the CAN bus as the output end of the common mode inductor, port 3 and port 4 are connected to the output end of the isolated CAN transceiver as the input end of the common mode inductor, and the output end of the isolated CAN transceiver outputs a differential signal; the first capacitor The first capacitor and the second capacitor are connected in series, and the first capacitor and the second capacitor connected in series are connected in parallel between the output end of the isolated CAN transceiver and the input end of the common-mode inductor, and the midpoint of the first capacitor and the second capacitor is connected to the ground; the third capacitor and the fourth capacitor are connected in series, and the third capacitor and the fourth capacitor connected in series are connected in parallel to the output end of the common-mode inductor, and the midpoint of the third capacitor and the fourth capacitor is connected to the ground; the TVS tube is connected in parallel to the output end of the common-mode inductor, and the terminal resistor is connected in parallel to the output end of the common-mode inductor.

[0008] As an alternative or supplement to the above scheme, in a method according to an embodiment of the present invention, the single-chip control module adjusts the output of the constant current control module to a preset value by feedback at least based on the current value, including: the single-chip control module obtains the voltage value at the output end of the constant current control module, and adjusts the output of the constant current control module to a preset value based on the current value and the voltage value.

[0009] As an alternative or supplement to the above scheme, in a method according to an embodiment of the present invention, the constant current control module includes: a core constant current module, a relay and a relay drive circuit, wherein the relay is connected to the output end of the core constant current module, and when the relay is in different gears, the output end of the core constant current module is connected to different loops: the core constant current module also includes a first control end and a second control end, the first control end is used to receive a voltage control signal from the single-chip control module, and the second control end is used to receive a current control signal from the single-chip control module, the voltage control signal and the current control signal are respectively used to control the output current and output current of the core constant current module; the relay drive circuit is used to receive a control signal from the single-chip control module to drive the relay to switch gears, and the relay drive circuit also includes a freewheeling diode connected in parallel with the relay coil side.

[0010] As an alternative or supplement to the above scheme, in a method according to an embodiment of the present invention, the isolated power supply module also includes: a first power supply module and a second power supply module, the first power supply module converts the input voltage into a first preset voltage, and the second power supply module converts the first preset voltage into a second preset voltage, wherein the first preset voltage is used to provide voltage to the isolated CAN communication module and the constant current source control module, and the second preset voltage is used to provide voltage to the isolated CAN communication module, the single-chip microcomputer control module and the sampling module, and the first power supply module is an isolation element, which isolates the input voltage received by the first power supply module from the preset voltage output by the first power supply module and the second power supply module.

[0011] As an alternative or supplement to the above scheme, in a method according to an embodiment of the present invention, the isolated CAN communication module also includes: the fifth capacitor and the sixth capacitor, wherein the capacitance value of the sixth capacitor is greater than the capacitance value of the fifth capacitor; wherein one end of the fifth capacitor is connected to the output end of the first power supply module, and the other end is connected to the ground; one end of the sixth capacitor is connected to the output end of the second power supply module, and the other end is connected to the ground.

[0012] In the second aspect, an embodiment of the present application provides a constant current source circuit board, which includes: a first layer, a wiring layer, a ground layer and a second layer arranged in sequence from top to bottom; an isolated power supply module, an isolated CAN communication module and a constant current control module are located on the side of the first layer away from the second layer, and a single-chip computer control module and a sampling module are located on the side of the second layer away from the first layer; the output end of the power supply device is connected in the first layer, and the power supply device is used to supply power to the isolated power supply module.

[0013] As an alternative or supplement to the above scheme, in a method according to an embodiment of the present invention, the ground layer includes a signal ground and a power ground, wherein the signal ground and the power ground are separately arranged and the signal ground and the power ground are connected at a single point.

[0014] As an alternative or supplement to the above scheme, in a method according to an embodiment of the present invention, the sampling module includes: a sampling resistor and a differential operational amplifier, wherein the input end wire of the differential operational amplifier is connected to the two ends of the sampling resistor and collects the voltage signal of the sampling resistor, and the end points of the input end wire are respectively located on the two welding points of the sampling resistor.

[0015] The above one or more technical solutions of the present invention have at least one or more of the following beneficial effects:

[0016] In the technical solution of the present invention, the electrical isolation design of the isolated power supply module is used to effectively improve the anti-interference ability of the constant current source in a complex electromagnetic environment and ensure the stability of the output current; the high reliability and data integrity of the signal transmission are achieved by isolating the CAN communication module, and the anti-interference performance of communication is enhanced; the feedback linkage between the sampling module and the single-chip microcomputer control module is used to achieve high-precision regulation of the output current and ensure that the current is consistent with the preset value; the design of the above modules improves the stability and reliability of the constant current source as a whole. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic diagram of an internal module of a constant current source provided in an embodiment of the present application;

[0018] Figure 2 It is a structural schematic diagram of an isolated power supply module provided in an embodiment of the present application;

[0019] Figure 3 This is a schematic diagram of the internal circuit of an isolated CAN communication module provided in an embodiment of the present application;

[0020] Figure 4 is a schematic diagram of the internal structure of an isolated CAN transceiver provided in an embodiment of the present application;

[0021] Figure 5 It is a schematic diagram of the internal structure of a single-chip control module provided in an embodiment of the present application;

[0022] Figure 6 is a circuit diagram of a constant current control module provided in an embodiment of the present application;

[0023] Figure 7 is a circuit structure diagram of a sampling module provided in an embodiment of the present application;

[0024] Figure 8a is a structural schematic diagram of a first power supply module provided in an embodiment of the present application;

[0025] Figure 8b is a structural schematic diagram of a second power supply module provided in an embodiment of the present application;

[0026] Fig. 9 It is a structural schematic diagram of a constant current source circuit board provided in an embodiment of the present application;

[0027] Fig.10 is a schematic diagram of a stratum provided in an embodiment of the present application;

[0028] Fig.11 is a schematic diagram of a partial structure of a sampling module provided in an embodiment of the present application;

[0029] List of reference numerals:

[0030] 1. First layer; 2. Wiring layer; 3. Ground layer; 4. Second layer; 5. Signal ground; 6. Power ground; 7. Short bridge; 8. Sampling resistor; 9. Wire; 10. Solder joint; 11. Input wire. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0032] The terms used in the following embodiments are only for the purpose of describing specific embodiments, and are not intended to be used as limitations on the present application. As used in the specification and the appended claims of the present application, the singular expressions "one", "a kind of", "said", "above", "the" and "this" are intended to also include expressions such as "one or more", unless there is a clear contrary indication in the context. It should also be understood that in the following embodiments of the present application, "at least one", "one or more" refer to one or more (including two). The term "and / or" is used to describe the association relationship of associated objects, indicating that three relationships may exist; for example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone, where A and B can be singular or plural. The character " / " generally indicates that the associated objects before and after are in an "or" relationship.

[0033] References to "one embodiment" or "some embodiments" etc. described in this specification mean that one or more embodiments of the present application include specific features, structures or characteristics described in conjunction with the embodiment. Thus, the statements "in one embodiment", "in some embodiments", "in some other embodiments", "in some other embodiments", etc. that appear in different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways. The term "connected" includes direct and indirect connections, unless otherwise stated.

[0034] In the following, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features.

[0035] In the embodiments of the present application, the words "exemplarily" or "for example" are used to indicate examples, illustrations or explanations. Any embodiment or design described as "exemplarily" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplarily" or "for example" is intended to present related concepts in a specific way.

[0036] like Figure 1 As shown, Figure 1 The figure is a schematic diagram of the internal modules of a constant current source of the present invention, wherein the constant current source is composed of five modules, namely, an isolated power supply module, an isolated CAN communication module, a single chip control module, a sampling module and a constant current control module.

[0037] exist Figure 1 In the example, the power supply device is used to provide power to the isolated power module. The power supply device can be a bus inside a device. When the device also has complex electrical devices such as servo motors and electromagnetic pulse generators, the current in the bus (power supply device) will be interfered with. This interference causes the originally relatively pure current to become a current containing noise such as high peak pulse current. This current with interference will destroy the output of the existing constant current source and make the output of the constant current source unstable.

[0038] The isolated power supply module in the constant current source is used to electrically isolate the power supply device from other modules in the constant current source. The isolated CAN communication module is used to make the communication between the constant current source and the host computer more stable. The single-chip control module is used to receive instructions from the host computer, control the operation of the isolated power supply module and the output of the constant current control module. The constant current control module is used to receive the output of the isolated power supply module and convert it into a preset value specified by the host computer for output. The sampling module is used to obtain the output current of the power conversion module and return it to the single-chip control module. The single-chip control module adjusts the current output of the constant current control module to the preset value through feedback through the returned sampling current.

[0039] exist Figure 1 The solid arrow in the figure indicates that an analog signal is transmitted, that is, the starting module of the arrow supplies power to the terminating module of the arrow. Figure 1 The dotted arrow in the figure represents the transmission of the signal, indicating that the signal is transmitted from the starting module of the arrow to the ending module of the arrow.

[0040] Then the multiple modules in the constant current source are described in detail as follows:

[0041] Isolated power module:

[0042] In the above constant current source circuit, the isolation power module is used to separate the power supply device from the subsequent modules. There are complex noises in the power supply device, which will affect the normal operation of each module in this constant current source, so the isolation power module is used to separate the power supply device from the subsequent modules.

[0043] For example, Figure 2 As shown, Figure 2 This is a schematic diagram of the structure of an isolated power module. The isolated power module includes a power conversion module, which is used to convert the voltage output by the power supply device and output a stable voltage. The power conversion module has an input end (pin 1 and pin 3), an output end (pin 4 and pin 8) and a control end (pin 2). Among them, the input end of the power conversion module is the input end of the isolated power module, and the output end of the power conversion module is the output end of the isolated power module.

[0044] The input end of the power conversion module is connected to the output end of the power supply device, the output end of the power conversion module is connected to the constant current control module, and the control end of the power conversion module is connected to the single-chip control module. The single-chip control module is used to control the level of the control end of the power conversion module, and then control the switching of the power conversion module between the working state and the disconnected state. When the power conversion module is in the working state, the output end of the power conversion module converts the voltage of the input end and outputs it at the output end. When the power conversion module is in the disconnected state, there is no voltage output at the output end of the power conversion module.

[0045] Further, such as Figure 2 As shown, the isolated power supply module also includes an optocoupler controller and a filter module. One end of the optocoupler controller is connected to the control end (pin 2) of the power conversion module, and the other end of the optocoupler controller is used for the single-chip microcomputer control module ( Figure 2 SYS-CON is connected to the pin of the microcontroller control module). The optocoupler controller also has a working state and a disconnected state. When the microcontroller control module sends a high-level signal to the optocoupler controller, the optocoupler controller works. Specifically, the high-level signal of the microcontroller control module passes through the light-emitting diode in the optocoupler controller, activating the light-emitting diode to start emitting light. After the light-emitting diode emits light, it activates the photodetector (such as a phototransistor) in the optocoupler controller, and the photodetector changes from disconnected to closed. Since the photodetector is connected to the control end of the power conversion module, the closure of the photodetector directly causes the change of the potential at the control end of the power conversion module.

[0046] exist Figure 2 In the example, the third terminal of the optocoupler controller is connected to the ground, and the fourth terminal of the optocoupler controller is connected to the control terminal of the power conversion device. There is a photodetector between the third and fourth terminals of the optocoupler controller. When the power conversion device detects that the potential is 0, the power conversion device enters the working state. When the photodetector is closed, the control terminal of the power conversion module will be directly connected to the ground. Figure 2 In the example, it is connected to the negative electrode MP- of the output terminal of the power supply device. Generally speaking, the voltage of the neutral line is 0 V, so the potential of the control end of the power conversion module is 0 V. This potential conversion will be sensed by the power conversion module (U1), so that the power conversion module switches from the disconnected state to the working state.

[0047] Further, such as Figure 2 As shown, the optocoupler controller also has a corresponding optocoupler filter module, which includes capacitor C1 and capacitor C6, wherein capacitor C1 is connected in parallel to the input end of the optocoupler controller (i.e., the light emitting diode), and capacitor C6 is connected in parallel to the output end of the optocoupler controller (i.e., the photodetector). Capacitor C1 is used to suppress low-frequency ripples, and capacitor C6 is used to filter high-frequency noise. Capacitor C1 and capacitor C6 together ensure the stability of the signal transmitted by the single-chip control module.

[0048] In the present technology, the power supply device is isolated from the constant current source circuit by setting a power conversion module, so that the noise of the power supply device will not affect the output of the subsequent constant current source. In addition, the single-chip control module can be isolated from the power conversion module by connecting the control end of the power conversion module through an optocoupler controller. Since the power conversion module is directly connected to the power supply device, and there is a risk of noise at the negative pole of the power supply device, the presence of the optocoupler controller can block the voltage input by the power supply device in the power control module, and prevent this voltage from affecting the single-chip control module.

[0049] The filter module includes an input filter module and an output filter module. The input filter module includes capacitor C2, capacitor C3, capacitor C4, and capacitor C5. The output filter module includes capacitor C7 and capacitor C8. The capacitor C2 is connected between the positive electrode MP+ of the output end of the power supply device and the ground, and the capacitor C3 is connected between the negative electrode MP- of the output end of the power supply device and the ground. The capacitor C2 and the capacitor C3 can remove the high-frequency signal output by the power supply device and suppress the noise output by it. The capacitance of the capacitor C4 is greater than that of the capacitor C5, and the capacitor C4 is connected in parallel with the capacitor C5. Similarly, the capacitance of the capacitor C7 is less than that of the capacitor C8, and the capacitor C7 is connected in parallel with the capacitor C8. Further, the capacitor C8 is a polar capacitor, wherein the positive electrode of the capacitor C8 is connected to the positive electrode of the output end of the power conversion module, and the negative electrode of the capacitor C8 is connected to the negative electrode of the output end of the power conversion module. The combination of the capacitor C4-capacitor C5 is similar to the combination of the capacitor C7-capacitor C8, both of which are a large capacitor and a small capacitor in parallel. The function of the large capacitor is to remove high-frequency noise. The function of the small capacitor is to remove low-frequency noise. The two can be connected in parallel to achieve dual filtering and can cover a wider filtering range.

[0050] Through the design of each circuit in the above-mentioned isolation power module, the isolation power module can isolate the input and provide a pure voltage output for the subsequent circuit ( Figure 2 28V voltage output in).

[0051] Isolation CAN communication module:

[0052] The isolated CAN communication module includes an isolated CAN transceiver, a decoupling circuit and a CAN bus protection circuit.

[0053] 1) Isolated CAN transceiver

[0054] The isolated CAN transceiver is used to realize the signal transmission between the microcontroller control module and the CAN bus, and provides isolation function at the same time. The isolated CAN transceiver can enhance the anti-interference ability of the isolated CAN communication module and protect the CAN bus from bus noise, ground loop or transient voltage interference.

[0055] like Figure 3 As shown, Figure 3 This is a schematic diagram of the internal circuit of an isolated CAN communication module. The isolated CAN transceiver U3 is connected to the microcontroller control module through its pins 4 and 5. CTX and CRX in the figure are the sending pin (PA12-33) and receiving pin (PA11-32) of the microcontroller control module. Therefore, the isolated CAN communication module is controlled by the microcontroller control module, and is used to communicate with the host computer where the constant current source circuit is located, receive the control instructions of the constant current source circuit, and output signals to the host computer.

[0056] Then, a scenario is taken as an example to explain the operation of the isolated CAN communication module, as follows: In one scenario, the user controls the host computer to issue a control instruction to make the constant current source circuit work. Then the host computer transmits the control instruction to the isolated CAN transceiver in the isolated CAN communication module through the CAN bus. After receiving the control instruction, the isolated CAN transceiver sends it to the single-chip control module, and then the single-chip control module controls the constant current source circuit to work. At this time, the isolated power supply module switches to the working state, and the constant current control module and the sampling module are both in the working state.

[0057] In addition, during the operation of the constant current source circuit, the constant current source circuit will generate some operating parameters, such as output current, etc. These operating parameters will be collected by the single-chip control module and sent to the isolated CAN communication module, which will be sent to the host computer through the CAN bus. At this time, the user observes the data received by the host computer to obtain the operating status of the constant current source circuit.

[0058] In the isolated CAN communication module, the CAN protocol may be used for communication, or a derivative protocol of the CAN protocol (such as the CAN-FD protocol) may be used for communication, which is not limited here.

[0059] The isolated CAN transceiver achieves signal transmission and electrical isolation between the MCU and the CAN bus through isolation, thereby improving communication reliability and anti-interference capabilities.

[0060] like Figure 4 As shown, Figure 4 Schematic diagram of the internal structure of an isolated CAN transceiver. In some embodiments, the isolated CAN transceiver includes a transformer driver, a rectifier module, a signal isolation module, and a signal conversion module.

[0061] The transformer driver is used to obtain a DC signal and convert the DC signal into a high-frequency signal and input it into the primary winding of the transformer T1. The secondary winding of the transformer is connected to the rectifier module.

[0062] Rectifier module: It is composed of a rectifier diode D1. The secondary winding of the transformer T1 receives energy from the primary winding through electromagnetic coupling, and outputs a stable DC voltage after passing through the rectifier diode D1. The DC voltage is used to power the signal isolation module and the signal conversion module. Furthermore, the DC voltage is further smoothed by a filter capacitor to form a stable isolated power supply (VISOIN and VISOOUT).

[0063] Signal isolation module: The signal isolation module can achieve signal isolation of data transmission through optical coupling, magnetic coupling or capacitive coupling. Its main function is to transmit the logic level signal sent by the microcontroller control module to the signal conversion module after isolation, and return the received logic level signal to the microcontroller control module through the opposite isolation path.

[0064] Signal conversion module: The signal conversion module is directly connected to CANH and CANL. The signal conversion module completes the conversion between standard CAN differential signals and single-ended logic level signals. Through the internal differential amplifier, the differential signal (CAN signal) of the CAN bus is demodulated into a single-ended signal (logic level signal), or the single-ended logic signal is modulated into a differential signal and output to the bus.

[0065] The remaining pins such as VIO and GND1 are used to connect the logic level interface of the isolated CAN transceiver. VIO determines the logic level voltage when the signal isolation module communicates with the microcontroller control module. CANH and CANL are responsible for connecting to the external bus to transmit CAN signals.

[0066] The isolated CAN transceiver achieves complete electrical isolation between the microcontroller control module and the CAN bus through isolated power supply and signal isolation modules, effectively improving the anti-interference ability, preventing ground loop interference and electromagnetic interference, and enhancing the reliability and safety of the system. It can resist transient high voltage, surge interference and electrostatic discharge, and ultimately enable the constant current source circuit of this technology to adapt to complex electromagnetic environments.

[0067] In this embodiment, the isolated power supply module and the isolated CAN communication module work together to isolate the power supply input by the power supply device and the communication line 9, so that the constant current source circuit can work stably in a complex electromagnetic environment.

[0068] 2) Decoupling circuit

[0069] The decoupling circuit includes: a capacitor C11 and a capacitor C12, wherein the capacitance value of the capacitor C12 is greater than the capacitance value of the capacitor C11. One end of the capacitor C11 is connected to the output end (3V3) of the first power supply module, and the other end is connected to the ground. One end of the capacitor C12 is connected to the output end (5V) of the second power supply module, and the other end is connected to the ground. The output end of the first power supply module and the output end of the second power supply module are both connected to the isolated CAN transceiver. The output end of the first power supply module is powered by the logic level in the isolated CAN transceiver and is connected to the VIO pin (pin 7) of the isolated CAN transceiver. The output end of the second power supply module is powered by the internal isolated power supply in the isolated CAN transceiver and is connected to the VCC pin (pin 8) of the isolated CAN transceiver. The capacitor C11 and the capacitor C12 are used to decouple the isolated CAN transceiver.

[0070] 3) CAN bus protection circuit

[0071] The CAN bus protection circuit includes: capacitor C13, capacitor C14, capacitor C15, capacitor C16, capacitor C17, capacitor C18, TVS tube D4 and common mode inductor L1. The isolation and protection mechanism of the CAN bus protection circuit improves the anti-interference ability and operation stability of the CAN bus. The CAN bus is a differential signal transmission method, which includes two main signal lines: CANH (high level) and CANL (low level). Noise suppression, signal matching and circuit protection are achieved through filter capacitors, common mode inductors, terminal matching resistors and transient suppressors (TVS tubes).

[0072] Capacitor C13 and capacitor C14 are connected across pin 11 (GND2) and pin 19 (VISOIN) of the isolated CAN transceiver. Capacitor C14 is connected in parallel with capacitor C13, and the capacitance value of capacitor C13 is greater than the capacitance value of capacitor C14. The function of pin 19 (VISOIN) is to provide the operating voltage input for the subsequent CAN bus, where capacitors C13 and C14 are used for filtering.

[0073] The common mode inductor L1 is used to receive the differential signal sent by the isolated CAN transceiver and suppress the common mode noise therein. The output of the common mode inductor L1 is connected to the CAN bus, and the signal after noise suppression is input into the CAN bus.

[0074] The common mode inductor L1 has four ports, namely port 1, port 2, port 3 and port 4. Port 1 and port 2 are connected to the CAN bus as the output end of the common mode inductor. Port 3 and port 4 are respectively connected to the 15th pin (CANL) and the 17th pin (CANH) of the isolated CAN transceiver, wherein the 15th pin (CANL) and the 17th pin (CANH) of the isolated CAN transceiver send the high level part and the low level part of the differential signal respectively.

[0075] Furthermore, there are capacitors C17 and C18, which are connected in series, and the two capacitors connected in series are connected between the 15th pin (CANL) and the 17th pin (CANH) of the isolated CAN transceiver, and the midpoints of capacitors C17 and C18 are connected to the ground. Capacitors C17 and C18 jointly suppress common-mode noise. In addition, at the output end of the common-mode inductor L1, the TVS tube D4 is connected between the 1st port and the 2nd port of the common-mode inductor L1. In other words, the TVS tube D4 is connected in parallel with the output of the common-mode inductor L1, wherein the TVS tube D4 can suppress transient peak current and surge current, thereby protecting the circuit.

[0076] Furthermore, the CAN bus protection circuit also includes a terminal resistor R6 connected between port 1 and port 2 of the common mode inductor L1, wherein the resistance of the terminal resistor R6 is greater than 100 ohms. The terminal resistor R6 is used for terminal matching of the CAN bus to avoid signal reflection and improve signal integrity.

[0077] Through the isolated CAN transceiver, decoupling circuit and CAN bus protection circuit, the data transmission of the CAN bus can be sufficiently resistant to complex electromagnetic environments, and the differential bus method can suppress common-mode interference. The design of common-mode inductance, filter capacitors, and TVS in the CAN bus protection circuit can respond to instantaneous peak currents and clamp the voltage on the CAN bus within a certain range, thereby protecting the circuit. Through the design of the above circuits, the isolated CAN communication module can still send accurate signals under extremely complex conditions.

[0078] Microcontroller control module:

[0079] The single-chip control module receives the control instructions from the host computer through the isolated CAN communication module, where the control instructions are parameters that instruct the constant current control module to generate current, such as waveform, pulse width, current peak value, etc. Then the single-chip control module controls the constant current control module to output the same current as the control instruction, and replies to the host computer through the CAN bus with an ACK signal, where the ACK signal may include: the working status of the constant current source, the operating time, and other parameters.

[0080] like Figure 5 As shown, Figure 5 This is a schematic diagram of the single-chip microcomputer control module. Figure 5 It is divided into 4 parts, where part (a) is the schematic diagram of the microprocessor, part (b) is the schematic diagram of the reset module, part (c) is the schematic diagram of the indicator light module, and part (d) is the schematic diagram of the debug interface module.

[0081] The single-chip control module includes a microprocessor, a reset module, an indicator light module, and a debug interface module. The functions of these modules are to provide system reset function, status indication function, and debug interface function, respectively, to ensure the stable operation and convenient debugging of the entire system.

[0082] like Figure 5 As shown in part (b), the core of the reset module is the reset chip U7, which is used to control the microprocessor to reset when the power supply voltage is abnormal. Reset means restoring the microprocessor to its initial state. The input end (pin 3) of the reset chip U7 is connected to the 3.3v power supply, and the 3.3V power supply is also the power supply for the microprocessor. The reset chip U7 monitors the voltage of the 3.3V power supply. When the voltage of the 3.3V power supply is lower than the preset voltage threshold (such as 1.5V), the reset chip U7 controls the microprocessor to reset. The output end (pin 2) of the reset chip U7 is connected to the ground through capacitor C27 to form a buffer for the reset signal to prevent the reset signal from being affected by high-frequency interference. In addition, the reset chip U7 will also reset the microprocessor during the power-on and power-off process of the microprocessor.

[0083] The reset module also includes a filter capacitor C28, which is used to eliminate interference noise on the reset signal line and ensure the stability of the reset signal. Through the design of the reset module, it can be ensured that the microcontroller can reliably enter the normal working state when the power is started or the system is abnormal.

[0084] like Figure 5 As shown in part (c), the indicator light module consists of two LED lights (LED1 and LED2) and their current limiting resistors (R8 and R9), which are used to indicate the operating status and debugging process of the system. The positive poles of LED1 and LED2 are connected to the 3.3V power supply through resistors R8 and R9 respectively, while the negative poles are directly connected to the ground (DGND). When the system is working, the control circuit will light up or turn off the corresponding indicator light to prompt the user of the current operating status of the system. For example, LED1 may be used to indicate that the system power supply is normal, and LED2 may be used to indicate whether a specific function is activated. Through this simple and intuitive indication method, users can quickly understand the status of the isolated power supply module, which facilitates operation and debugging.

[0085] like Figure 5As shown in part (d) of the figure, the debug interface module includes a set of 4-pin sockets J1 and voltage divider resistors (R6 and R7) connected to it, which are used to provide a standard SWD (Serial Wi re Debug) debug interface for the system. The SWDIO and SWCLK pins of socket J1 are connected to the main control chip through resistors R6 and R7 respectively to form data and clock channels. The debug interface module allows developers to communicate with the main control chip through the SWD interface to upload programs or debug the system. Socket J1 also provides reference power and ground for the debugging device through pins connected to the ground (DGND) and power supply (3.3V). Through the design of the debug interface module, the system can be easily debugged, tested and firmware updated, improving development efficiency.

[0086] Further, in Figure 5 The external clock composed of filter capacitors (C25 and C26) and crystal oscillator X1 is also included to provide time indication function for the 8-IN and 8-OUT signal interfaces of the microprocessor. Through the external clock, the time timing of the microprocessor can be made more accurate.

[0087] Constant current control module:

[0088] like Figure 6 As shown, Figure 6 It is a circuit diagram of a constant current control module.

[0089] The constant current control module includes: a core constant current module, a relay K1 and a relay drive circuit.

[0090] The core constant current module has an input terminal (pin 1 and pin 3 of U2) and an output terminal (pin 4 and pin 6 of U2), wherein the input terminal is connected to the output terminal of the isolation power module, and the output terminal outputs the voltage. A ninth capacitor C9 is connected across the input terminals of the core constant current module to smooth the voltage and suppress high-frequency noise on the input side.

[0091] In addition, the core constant current module also includes a control end, which can be divided into a first control end and a second control end. The single-chip control module is connected to the first control end (pin 6, VSET) of the core constant current module through its pin 14 (DACO), and the first control end of the core constant current module is used to receive a control signal from the single-chip control module, thereby regulating the voltage output by the core constant current module. The single-chip control module is connected to the second control end (pin 5, ISET) of the core constant current module through its pin 15 (DAC1), and the second control end is used to receive a control signal, thereby regulating the current output by the core constant current module.

[0092] In the circuit connecting the microcontroller control module and the core constant current module, there are also voltage zener diodes (D3 and D6) and voltage divider resistors (R5 and R14). Two of the voltage zener diodes are used to provide reference voltage protection for DAC0 (voltage setting) and DAC1 (current setting) to prevent damage to the core constant current module due to accidental overvoltage. The two voltage divider resistors are used for voltage setting of DAC0 and DAC1, respectively, to play a role in signal regulation and voltage division, ensuring that the voltage input received by the core constant current module is within a reasonable range.

[0093] In addition, the single-chip control module can also send out another control signal, which controls the relay drive circuit and then controls the relay to switch the output of the core constant current module to a different loop.

[0094] The relay drive circuit includes at least one transistor Q1. The transistor Q1 is used to amplify the control signal of the single-chip control module, because the current that the single-chip control module can release is not enough to drive the relay K1 to work. When the transistor Q1 receives the control signal of the single-chip control module, the transistor Q1 amplifies the driving current and drives the relay K1 to work according to the amplified driving current. When the relay K1 is working, its pin 5 will be introduced into different loops, so that the constant current control module discharges the circuits of different loops.

[0095] Furthermore, when the relay K1 is driven by a coil, the coil in the relay K1 can be regarded as an inductor. At this time, the relay driving circuit also includes: a freewheeling diode D2. The freewheeling diode D2 is connected in parallel with the control port of the relay K1 to absorb the reverse electromotive force generated by the coil in the relay K1 to prevent the reverse electromotive force from damaging the single-chip control module.

[0096] Sampling module:

[0097] As the constant current control module works, the heat of the constant current control module will gradually accumulate. When the heat of the constant current control module accumulates to a certain value, the constant current control module can no longer output current and voltage in a high-precision manner. The sampling module corrects the output of the constant current control module when there is a deviation in the current and voltage output by the constant current control module itself.

[0098] like Figure 7 As shown, Figure 7 This is a schematic diagram of the circuit structure of a sampling module. Figure 7 There are two circuit structure diagrams, namely part (a) and part (b). The sampling resistor 8 is R14. Part (a) is the voltage sampling circuit. Part (a) is the voltage output of the constant current control module ( Figure 6Part (b) is the current sampling circuit, which collects the current passing through the sampling resistor 8. In order to minimize the impact on the output of the constant current control module, the sampling resistor 8 should be as small as possible, for example, the resistance of the material resistor is 20mΩ. Figure 7 The two circuits (a) and (b) are described separately as follows:

[0099] (a) Voltage sampling circuit:

[0100] The voltage sampling circuit directly measures the voltage VO+ at the output end of the constant current control module, and the collected signal is amplified by the first operational amplifier U11. Figure 7 In part (a), resistors R16 and R17 are used for voltage division and reduce the voltage at the output end of the constant current control module. The reduced voltage can be transmitted to the ADC (analog-to-digital converter) through the ADC1 port for processing. Capacitor C32 is also used for filtering.

[0101] (b) Current sampling circuit:

[0102] The current sampling circuit measures the sampling resistor 8 (i.e. Figure 7 The voltage of the resistor R14 in the sampling resistor 8 is used to calculate the current at the output end of the constant current control module. Specifically, one end of the sampling resistor 8 is connected to one end of the load, and the other end of the sampling resistor 8 is connected to the ground, wherein the other end of the load is connected to the output end of the constant current control module. In addition, one end of the sampling resistor 8 can also be connected to the output end of the constant current control module, and the other end is connected to the load.

[0103] exist Figure 7 In part (b), the differential operational amplifier U12 is used to amplify the voltage signal of the sampling resistor 8. The gain resistor R15, the gain resistor R18 and the gain resistor R20 form a gain network to amplify the voltage of the sampling resistor 8. The filter capacitor C33 is used to filter out the high-frequency noise in the sampling signal. Finally, the current signal collected by the current sampling circuit is input into the ADC2 pin and transmitted to the corresponding ADC for analog-to-digital conversion.

[0104] The ADC will collect the voltage signal and current signal at the output end of the constant current control module, and input the voltage signal and current signal into the single-chip control module, so that the single-chip control module can obtain the voltage value and current value at the output end of the constant current control module. The single-chip control module performs feedback adjustment on the constant current control module according to the voltage value and current value transmitted by the ADC. Specifically, the single-chip control module adjusts the output of the constant current control module by feedback.

[0105] In some embodiments, the single-chip control module directly changes the output of the core constant current module through the first control terminal and / or the second control terminal. It has been explained above that the first control terminal and the second control terminal are respectively used to control the output voltage and output current of the core constant current module. Therefore, the PID algorithm can be used to control the output of the core constant current module until the output of the core constant current module reaches a preset value.

[0106] In other embodiments, the microcontroller control module converts the digital signal of the microcontroller into an analog signal through a DAC (digital-to-analog converter), and directly inputs the analog signal into the output of the core constant current module, thereby controlling the output of the constant current source so that the output of the constant current source is a preset value.

[0107] In addition, further, the constant current source also includes a chip power supply module, wherein the chip power supply module is used to convert the input voltage into one or more preset voltages. The preset voltage provides voltage for the isolated CAN communication module, the single-chip control module, the sampling module and the constant current source control module. The input voltage can be the voltage provided by the output end of the power supply device, or it can be the voltage provided by another voltage providing device. In other words, the voltage received by the chip power supply module can be the same as or different from the voltage received by the isolated power supply module.

[0108] Furthermore, the chip power supply module includes a first power supply module and a second power supply module, wherein the first power supply module converts the input voltage into a first preset voltage, and the second power supply module converts the first preset voltage into a second preset voltage, wherein the first preset voltage is used to provide voltage to the isolated CAN communication module and the constant current source control module, and the second preset voltage is used to provide voltage to the isolated CAN communication module, the single-chip control module and the sampling module. The first power supply module is an isolation element, which isolates the input voltage received by the chip power supply module from the preset voltage output by the chip power supply module.

[0109] like Figure 8a and Figure 8b As shown, Figure 8a is a structural diagram of the first power supply module, Figure 8b It is a structural schematic diagram of the second power supply module.

[0110] like Figure 8aAs shown, the first power supply module includes a power conversion chip U3, the input end of the power conversion chip U3 is connected to the input voltage received by the chip power supply module, and its input end (pin 1 and pin 2) is connected to the 12V input voltage, and the high-frequency noise of the input end is suppressed by the filter capacitor. The output end (pin 5 and pin 7) generates a first preset voltage of 5V, and the first preset voltage is further provided to the second power supply module. The internal isolation structure of the power conversion chip U3 ensures the electrical isolation between the input and the output, and provides a stable and pure voltage output for the subsequent modules.

[0111] like Figure 8b As shown, the function of the second power supply module is to further convert the 5V voltage in the first preset voltage into a second preset voltage of 3.3V, which is used to power the isolated CAN communication module, the single-chip control module and the sampling module. The second power supply module implements this function through a voltage regulator chip (such as HT7833), whose input end is connected to the 5V output of the first power supply module, and the output end generates a stable 3.3V voltage. The interior of the voltage regulator chip uses a high-precision voltage regulation circuit and an output filter module to ensure that the output voltage meets the accuracy requirements of the low-voltage equipment. The second preset voltage directly powers the single-chip control module, the isolated CAN communication module and the sampling module, providing good power support.

[0112] Through the coordinated work of the first power supply module and the second power supply module, the chip power supply module not only realizes the conversion of the input voltage to multiple preset voltages, but also effectively isolates the noise at the input end, providing a basic guarantee for the stable operation of the constant current source system. In particular, the isolation element in the first power supply module and the voltage stabilization design in the second power supply module make the power output purer to meet the power supply requirements of different modules.

[0113] like Fig. 9 As shown, Fig. 9 It is a structural diagram of a constant current source circuit board.

[0114] The present invention also provides a constant current source circuit board, which includes: a first layer 1, a wiring layer 2, a ground layer 3 and a second layer 4 arranged in sequence from top to bottom, an isolated power supply module, an isolated CAN communication module and a constant current control module are located on a side of the first layer 1 away from the second layer 4, and a single-chip computer control module and a sampling module are located on a side of the second layer 4 away from the first layer 1; the output end of the power supply device is connected to the first layer 1, and the power supply device is used to supply power to the isolated power supply module.

[0115] like Fig. 9 As shown, the circuit board includes a four-layer structure. The wiring layer 2 is used to meet the internal routing. The ground layer 3 is used to provide grounding for each component on the circuit board. Fig. 9The upper surface of the circuit board (the upper direction of the first layer 1) has an isolated power module, an isolated CAN communication module and a constant current control module, and the lower surface of the circuit board (the lower direction of the second layer 4) has a single-chip control module and a sampling module. The four-layer structure is used because the single-chip control module and the sampling module are both precision devices, and a little interference will have a great impact on the output of the entire constant current source circuit.

[0116] The above design concentrates the isolation power module, the isolation CAN communication module and the constant current control module on the upper surface of the circuit board, and concentrates the single-chip control module and the sampling module on the lower surface of the circuit board, so that the distance between the devices on these two surfaces in space is as far as possible. And by setting the middle stratum 3, the high-power and high-noise devices are concentrated on the upper surface of the circuit board, and the stratum 3 provides protection for the lower surface of the second circuit board, blocking the electromagnetic pulses emitted from the devices on the upper surface of the circuit board. This design can provide a good electromagnetic shielding effect, reduce ground loops and noise interference, and is conducive to the stable operation of the single-chip control module and the sampling module in a complex electromagnetic environment. In addition, the isolation power module, the isolation CAN communication module and the constant current control module are located on the upper surface of the circuit board, which can make the heat dissipation of the constant current source circuit easier to design, and the heat dissipation devices can be centrally arranged, so that the final heat dissipation effect is better.

[0117] Further, such as Fig.10 As shown, Fig.10 The diagram is a schematic diagram of a ground layer. The ground layer 3 includes a signal ground 5 and a power ground 6, wherein the signal ground 5 and the power ground 6 are separated and connected at a single point. Fig.10 In the embodiment, a short bridge 7 is used to connect the signal ground 5 and the power ground 6. The material used in the short bridge 7 is copper.

[0118] Specifically, Figures 2 to 8b As shown, each GND port is connected to the power ground 6, and each DGND port is connected to the signal ground 5. Then, the power ground 6 and the signal ground 5 are connected through a very small copper sheet (short bridge 7) to avoid interference between the two grounds.

[0119] Furthermore, the sampling module includes: a sampling resistor 8 and a differential operational amplifier, wherein an input wire 11 of the differential operational amplifier is connected to two ends of the sampling resistor 8 and collects a voltage signal of the sampling resistor 8, and the endpoints of the input wire 11 are respectively located on two welding points 10 of the sampling resistor 8.

[0120] like Fig.11 As shown, Fig.11It is a schematic diagram of a part of the structure in a sampling module. The sampling resistor 8 is connected to the line 9 through the solder joint 10. The line 9 is the output circuit of the constant current control module. In the prior art, since the line 9 is regarded as zero resistance, the input wire 11 of the differential operational amplifier will be connected to the line 9. However, in the present technology, the input wire 11 is directly connected to the solder joint 10 of the sampling resistor 8.

[0121] In order to reduce the influence of the sampling resistor 8 on the output end of the constant current control module, the resistance value of the sampling resistor 8 itself is very low, about a few milliohms to tens of milliohms. At this time, the resistance of the line 9 itself is likely to affect the final calculation accuracy. Therefore, directly connecting the input end wire 11 to the solder joint 10 of the sampling resistor 8 helps to more accurately obtain the current flowing through the sampling resistor 8, so that the single-chip control module can more accurately control the constant current control module.

[0122] It is understandable that in order to implement the above functions, the electronic device includes hardware structures and / or software modules corresponding to the execution of each function. Those skilled in the art should easily realize that, in combination with the algorithm steps of each example described in the embodiments disclosed herein, the present invention can be implemented in the form of hardware or a combination of hardware and computer software. Whether a function is executed in the form of hardware or computer software driving hardware depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0123] The embodiment of the present invention can divide the electronic device into functional modules according to the above method example. For example, each functional module can be divided according to each function, or two or more functions can be integrated into one processing module. The above integrated module can be implemented in the form of hardware or in the form of software functional modules. It should be noted that the division of modules in the embodiment of the present invention is schematic and is only a logical function division. There may be other division methods in actual implementation.

[0124] It is understandable that the processor in the embodiments of the present application may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field programmable gate arrays (FPGA) or other programmable logic devices, transistor logic devices, hardware components or any combination thereof. The general-purpose processor may be a microprocessor or any conventional processor.

[0125] The method steps in the embodiments of the present application can be implemented by hardware, or by a processor executing software instructions. The software instructions can be composed of corresponding software modules, and the software modules can be stored in random access memory (RAM), flash memory, read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), registers, hard disks, mobile hard disks, CD-ROMs, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor so that the processor can read information from the storage medium and write information to the storage medium. Of course, the storage medium can also be a component of the processor. The processor and the storage medium can be located in an ASIC.

[0126] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When implemented using software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the process or function described in the embodiment of the present application is generated in whole or in part. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions may be stored in a computer-readable storage medium or transmitted through the computer-readable storage medium. The computer instructions may be transmitted from a website site, a computer, a server or a data center to another website site, a computer, a server or a data center by wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium may be any available medium that a computer can access or a data storage device such as a server or a data center that includes one or more available media integrated. The available medium may be a magnetic medium, (e.g., a floppy disk, a hard disk, a tape), an optical medium (e.g., a DVD), or a semiconductor medium (e.g., a solid-state drive (SSD)), etc.

[0127] It should be understood that the various numerical numbers involved in the embodiments of the present application are only used for the convenience of description and are not used to limit the scope of the embodiments of the present application.

Claims

1. A constant current source, characterized in that: include: Isolation power module, isolation CAN communication module, single chip control module, sampling module and constant current control module; among them, The isolated power supply module includes a power conversion module and an optical coupling controller, the input end of the power conversion module is the input end of the isolated power supply module, the output end of the power conversion module is the output end of the isolated power supply module, and the power conversion module electrically isolates the input end and the output end of the power conversion module; The input end of the power conversion module is connected to the output end of the power supply device, the output end of the power conversion module is connected to the constant current control module, and the control end of the power conversion module is connected to the single-chip control module through an optical coupling controller, so that the single-chip control module controls the opening and closing of the power conversion module; The isolated CAN communication module includes an isolated CAN transceiver and a CAN bus protection circuit: wherein the isolated CAN transceiver isolates the primary side and the secondary side of the isolated CAN transceiver, the primary side is connected to the single-chip control module, and the secondary side is connected to the host computer through the CAN bus protection circuit and the CAN bus; The constant current control module is connected to the isolation power supply module and outputs based on a preset value; The sampling module is arranged at the output end of the constant current control module, and is used to obtain the current value of the output end of the constant current control module. The single chip control module adjusts the output of the constant current control module to a preset value by feedback at least based on the current value.

2. The constant current source according to claim 1, characterized in that: The CAN bus protection circuit includes: a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a TVS tube, a common mode inductor and a terminal resistor; The common-mode inductor comprises: port 1, port 2, port 3 and port 4, wherein port 1 and port 2 are connected to the CAN bus as output ends of the common-mode inductor, port 3 and port 4 are connected to the output end of the isolated CAN transceiver as input ends of the common-mode inductor, and the output end of the isolated CAN transceiver outputs a differential signal; The first capacitor and the second capacitor are connected in series, and the first capacitor and the second capacitor connected in series are connected in parallel between the output end of the isolated CAN transceiver and the input end of the common-mode inductor, and the midpoint of the first capacitor and the second capacitor is connected to the ground; The third capacitor and the fourth capacitor are connected in series, and the third capacitor and the fourth capacitor connected in series are connected in parallel with the output end of the common mode inductor, and the midpoint of the third capacitor and the fourth capacitor is connected to the ground; The TVS tube is connected in parallel with the output end of the common mode inductor, and the terminal resistor is connected in parallel with the output end of the common mode inductor.

3. The constant current source according to claim 2, characterized in that: The constant current control module includes: a core constant current module, a relay and a relay driving circuit, wherein the relay is connected to the output end of the core constant current module, and when the relay is in different gears, the output end of the core constant current module is connected to different circuits; The core constant current module also includes a first control end and a second control end, the first control end is used to receive a voltage control signal from the single-chip control module, and the second control end is used to receive a current control signal from the single-chip control module, and the voltage control signal and the current control signal are used to control the output current and the output current of the core constant current module respectively; The relay drive circuit is used to receive a control signal from the single-chip control module to drive the relay to switch gears. The relay drive circuit also includes a freewheeling diode connected in parallel with the relay coil side.

4. The constant current source according to any one of claims 1 to 3, characterized in that: The isolated power supply module also includes: a first power supply module and a second power supply module, the first power supply module converts the input voltage into a first preset voltage, and the second power supply module converts the first preset voltage into a second preset voltage, wherein the first preset voltage is used to provide voltage to the isolated CAN communication module and the constant current source control module, and the second preset voltage is used to provide voltage to the isolated CAN communication module, the single-chip control module and the sampling module, and the first power supply module is an isolation element, which isolates the input voltage received by the first power supply module from the preset voltages output by the first power supply module and the second power supply module.

5. The constant current source according to claim 4, characterized in that: The isolated CAN communication module also includes: a fifth capacitor and a sixth capacitor, wherein the capacitance value of the sixth capacitor is greater than the capacitance value of the fifth capacitor; wherein one end of the fifth capacitor is connected to the output end of the first power supply module, and the other end is connected to the ground; one end of the sixth capacitor is connected to the output end of the second power supply module, and the other end is connected to the ground.

6. The constant current source according to claim 4 or 5, characterized in that: The single-chip control module adjusts the output of the constant current control module to a preset value by feedback at least based on the current value, including: The single chip control module obtains the voltage value of the output end of the constant current control module, and adjusts the output of the constant current control module to a preset value based on the current value and the voltage value.

7. The constant current source according to claim 1, characterized in that: The isolated CAN transceiver includes a transformer driver, a rectifier module, a signal isolation module and a signal conversion module; wherein, The transformer driver acquires a DC signal and converts the DC signal into a high-frequency signal and inputs it into the primary winding of the transformer, and the secondary winding of the transformer is connected to the rectifier module; The rectifier module obtains the output voltage of the secondary winding of the transformer and outputs a DC voltage through the rectifier module, wherein the DC voltage is used to power the signal isolation module and the signal conversion module; One end of the signal isolation module is connected to the single-chip control module as the primary side of the isolated CAN transceiver, and the other end is connected to the first end of the signal conversion module. The second end of the signal conversion module serves as the secondary side of the isolated CAN transceiver, wherein the signal isolation module is used to electrically convert the received and transmitted signals, and the signal conversion module converts the CAN signal on the CAN bus into a logic level signal, wherein the logic level signal is a signal that can be directly understood by the single-chip control module.

8. A constant current source circuit board, characterized in that: The circuit board comprises: a first layer, a wiring layer, a ground layer and a second layer arranged in sequence from top to bottom; The isolated power supply module, the isolated CAN communication module and the constant current control module are located on a side of the first layer away from the second layer, and the single-chip control module and the sampling module are located on a side of the second layer away from the first layer; The output terminal of the power supply device is connected in the first layer, and the power supply device is used to supply power to the isolated power supply module.

9. The constant current source circuit board according to claim 8, characterized in that: The ground layer includes a signal ground and a power ground, wherein the signal ground and the power ground are separately arranged, and the signal ground and the power ground are connected at a single point.

10. The constant current source circuit board according to claim 8, characterized in that: The sampling module includes: a sampling resistor and a differential operational amplifier, wherein the input end wire of the differential operational amplifier is connected to the two ends of the sampling resistor and collects the voltage signal of the sampling resistor, and the end points of the input end wire are respectively located on the two welding points of the sampling resistor.

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