Active Ethernet drive circuit

Abstract

The embodiment of the invention provides an active Ethernet drive circuit, which comprises a constant current source module, a control module and a switch module which are connected in sequence, the switch module is arranged between a first voltage source and a first node, and the first node is used for accessing a load; wherein the constant current source module is used for outputting constant current to the control module when the load is connected to the first node and the resistance value of the load is smaller than a preset maximum resistance value; the control module is used for outputting a corresponding level signal to the switch module according to the magnitude relationship between the resistance value of the load and the preset minimum resistance value when the constant current is received; and the switch module is used for controlling whether the first voltage source supplies power to the load or not according to the received level signal. Whether the resistance value of the load is in a normal range can be detected, and the power supply is provided when the resistance value is in the normal range.

Description

Technical Field

[0001] The present invention relates to the technical field of active Ethernet, and in particular to an active Ethernet driving circuit. Background Art

[0002] Servo systems often require active Ethernet ports, which provide both Ethernet communication and power to the load. For power supply, after inserting a load into an active Ethernet port, the port must be tested to see if the load is within the specified range. Only after this test confirms that the load meets these requirements can power be supplied to the load. Summary of the Invention

[0003] An embodiment of the present invention provides an active Ethernet driving circuit, which can detect whether the resistance of a load is within a normal range and provide power when the resistance is within the normal range.

[0004] An active Ethernet driver circuit provided by one embodiment of the present invention includes a constant current source module, a control module, and a switch module connected in sequence, wherein the switch module is arranged between a first voltage source and a first node, and the first node is used to connect to a load; wherein:

[0005] The constant current source module is configured to output a constant current to the control module when the first node is connected to the load and the resistance of the load is less than a preset maximum resistance;

[0006] The control module is configured to: upon receiving the constant current, output a corresponding level signal to the switch module according to a magnitude relationship between the resistance of the load and a preset minimum resistance;

[0007] The switch module is configured to control whether the first voltage source supplies power to the load according to the received level signal.

[0008] The active Ethernet driver circuits provided in the embodiments of the present invention each have at least the following technical effects individually or in combination:

[0009] (1) When the first node is connected to the load and the resistance of the load is less than the preset maximum resistance, the constant current source module will output a constant current to the control module. Therefore, when the control module receives the constant current, it indicates that the resistance of the connected load is less than the preset maximum resistance. When the control module receives the constant current, the control module only needs to compare the magnitude relationship between the load resistance and the preset minimum resistance, and then generate a corresponding level signal based on the magnitude relationship and send the level signal to the switch module. After receiving the level signal, the switch module will control whether the first voltage source supplies power to the load based on the level signal. It can be seen that the active Ethernet driver circuit provided in the embodiment of the present invention can detect whether the resistance of the load is within the normal range and provide power when it is within the normal range.

[0010] (2) In one embodiment, the control module includes a comparison unit, and the comparison unit includes a first comparator. The voltage value of the negative input terminal of the first comparator is the product of the constant current and the preset minimum resistance value, and the voltage value of the positive input terminal of the first comparator is the product of the constant current and the resistance value of the load. Therefore, by comparing the voltage values, the magnitude relationship between the load resistance value and the preset minimum resistance value can be obtained. It can be seen that by comparing the voltages, it is possible to determine whether the load exceeds the preset minimum resistance value. In one embodiment, the voltage value of the third voltage source is equal to the product of the constant current and the preset maximum resistance value. Therefore, by determining whether there is current in the loop, it is possible to determine whether the connected load is disconnected and whether the load resistance value exceeds the preset maximum resistance value. It can be seen that the logic of determining whether the load resistance value is within the normal range and supplying power to the load when it is within the normal range can be realized only by hardware circuits, without involving software logic, and without requiring high-cost devices with software logic capabilities such as processors and controllers, thereby reducing costs.

[0011] (3) In one embodiment, the control module includes a comparison unit and an optical coupling unit, and the output signal of the optical coupling unit and the level signal output by the comparison unit are used for joint judgment, thereby reducing misjudgment and improving accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0013] Figure 1 is a structural block diagram of an active Ethernet driver circuit in one embodiment of the present invention;

[0014] Figure 2 1 is a circuit diagram of an active Ethernet driver circuit when connected to a load in one embodiment of the present invention;

[0015] Reference numerals:

[0016] DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0018] An embodiment of the present invention provides an active Ethernet driving circuit.

[0019] See also Figure 1 The active Ethernet driving circuit 100 includes a constant current source module 10, a control module 20 and a switch module 30 connected in sequence. The switch module 30 is arranged between a first voltage source Vcc1 and a first node P, and the first node P is used to connect to a load; wherein:

[0020] The constant current source module 10 is configured to output a constant current to the control module when the first node is connected to the load and the resistance of the load is less than a preset maximum resistance;

[0021] The control module 20 is configured to: upon receiving the constant current, output a corresponding level signal to the switch module according to a magnitude relationship between the load resistance and a preset minimum resistance;

[0022] The switch module 30 is configured to control whether the first voltage source supplies power to the load according to the received level signal.

[0023] Among them, active Ethernet is POE, which is spelled as Power Over Ethernet in English.

[0024] The first node is used to connect to the load. The first node is the POE-P node. Specifically, the load is connected between the POE-P node and the POE-M node. The POE-M node is a grounded node, so it can be considered that the load is connected between the POE-P node and the ground terminal.

[0025] The preset maximum resistance is set based on customer needs, and the preset minimum resistance mentioned below is also set based on customer needs. The first voltage source only supplies power to the connected load when the load resistance is between the preset maximum and minimum resistances. When the load resistance is less than or equal to the preset minimum resistance or greater than or equal to the preset maximum resistance, the first voltage source does not supply power to the load. This is the goal of the active Ethernet driver circuit in embodiments of the present invention. To achieve this goal, embodiments of the present invention provide an active Ethernet driver circuit with the aforementioned structure.

[0026] In the active Ethernet driver circuit of the above structure, when the first node is connected to the load and the load's resistance is less than a preset maximum resistance, the constant current source module outputs a constant current to the control module. Therefore, when the control module receives the constant current, it indicates that the resistance of the connected load is less than the preset maximum resistance. When the control module receives the constant current, it simply compares the load's resistance with the preset minimum resistance, generates a corresponding level signal based on this relationship, and transmits the level signal to the switch module. Upon receiving the level signal, the switch module controls whether the first voltage source supplies power to the load based on the level signal.

[0027] For example, when the load resistance is greater than a preset minimum resistance, the control module generates a high level signal. When the load resistance is less than or equal to the preset minimum resistance, the control module generates a low level signal. A high level signal causes the switch module to control the first voltage source to supply power to the load. A low level signal causes the switch module to control the first voltage source not to supply power to the load, thereby achieving the above-mentioned objective.

[0028] In one embodiment, the constant current source module can also be used to: when the resistance of the load is greater than or equal to the preset maximum resistance, no output current is sent to the control module; the control module can also be used to: when the constant current is not received, no output level signal is sent; the switch module can also be used to: when the level signal is not received, control the first voltage source to not supply power to the load.

[0029] That is, when the load resistance is greater than or equal to the preset maximum resistance, the constant current source module will not output current to the control module. When the control module does not receive the constant current, it will not output the level signal. When the switch module does not receive the level signal, it will not cause the first voltage source to supply power to the load. This section clearly explains how to handle the situation where the load resistance is greater than or equal to the preset maximum resistance, thereby further ensuring the achievement of the above objectives.

[0030] In one embodiment, see Figure 2The control module includes a comparison unit 21, and the comparison unit 21 includes a first comparator U1, wherein: the positive input terminal of the first comparator U1 is connected to the output terminal of the constant current source module and the first node P, and the load Rx is connected between the first node P and the ground terminal; the voltage value Vin2 of the negative input terminal of the first comparator U1 is the product of the constant current Iout and the preset minimum resistance; the output terminal of the first comparator is connected to the switch module; when the control module receives the constant current, the voltage value Vd of the positive input terminal of the first comparator is the product of the constant current Iout and the resistance of the load Rx; the first comparator U1 is specifically used to: upon receiving the constant current When the constant current is received, if the resistance of the load Rx is greater than the preset minimum resistance, the voltage value Vd of the positive input terminal of the first comparator is greater than the voltage value Vin2 of the negative input terminal of the first comparator, and the level signal output by the first comparator is a first level, so that the switch module controls the first voltage source Vcc1 not to supply power to the load Rx; when the constant current is received, if the resistance of the load Rx is greater than the preset minimum resistance, the voltage value Vd of the positive input terminal of the first comparator is greater than the voltage value Vin2 of the negative input terminal of the first comparator, and the level signal output by the first comparator is a second level, so that the switch module controls the first voltage source Vcc1 to supply power to the load Rx.

[0031] That is, when the load is connected between the first node and the ground, the output of the constant current source module, the positive input of the first comparator, the first node, the load, and the ground are connected in sequence, thus forming a loop. When there is current in this loop, the magnitude of the current is the constant current, and the voltage value of the positive input of the first comparator is the product of the constant current and the resistance of the load. It can be seen that the voltage value of the positive input of the first comparator is related to the resistance of the load, and the voltage value of the positive input of the first comparator reflects the resistance of the load. The voltage value of the negative input of the first comparator is the product of the constant current and the preset minimum resistance, that is, the voltage value of the negative input of the first comparator is a constant voltage value, and this constant voltage value reflects the magnitude of the preset minimum resistance.

[0032] It is understood that when the positive input terminal of the first comparator receives a constant current, if the resistance of the load is less than or equal to the preset minimum resistance, then the voltage value at the positive input terminal of the first comparator is less than or equal to the voltage value at the negative input terminal of the first comparator, and the first comparator outputs a first voltage level, which causes the switch module to control the first voltage source to not supply power to the load. When the positive input terminal of the first comparator receives the constant current, if the resistance of the load is greater than the preset minimum resistance, then the voltage value at the positive input terminal of the first comparator is greater than the voltage value at the negative input terminal of the first comparator, and the first comparator outputs a second voltage level, which causes the switch module to control the first voltage source to supply power to the load.

[0033] For example, when the resistance of the connected load is greater than a preset minimum resistance, the voltage at the positive input of the first comparator is greater than the voltage at the negative input of the first comparator. At this time, the level signal output by the first comparator is a high level, which can cause the switch module to control the first voltage source to supply power to the load. When the resistance of the connected load is less than or equal to the preset minimum resistance, the voltage at the positive input of the first comparator is less than or equal to the voltage at the negative input of the first comparator. At this time, the level signal output by the first comparator is a low level, which can cause the switch module to control the first voltage source not to supply power to the load.

[0034] It can be seen that the above-mentioned first comparator can output a corresponding level signal to the switch module according to the size relationship between the resistance of the connected load and the preset minimum resistance, so that the switch module controls whether the first voltage source supplies power to the load.

[0035] In one embodiment, see Figure 2 The comparison unit may further include a first diode D1, which is arranged between the positive input terminal of the first comparator and the output terminal of the constant current source module, and the anode of the first diode D1 is connected to the output terminal of the constant current source module, and the cathode of the first diode D1 is connected to the positive input terminal of the first comparator.

[0036] That is to say, a first diode is added between the positive input terminal of the first comparator and the output terminal of the constant current source module. Due to the existence of the first diode, the direction of the current in the loop formed by the output terminal of the constant current source module, the positive input terminal of the first comparator, the first node, the load and the ground terminal is only one. Therefore, when the voltage value of the positive input terminal of the first comparator is higher than the third voltage source inside the constant current source module, there is no current output from the output terminal of the constant current source module, that is, there is no current in the above-mentioned loop at this time, the first comparator has no output level signal, and the switch module will not enable the first voltage source to power the load.

[0037] It can be seen that due to the presence of the first diode and the third voltage source inside the constant current source module, the constant current source module outputs a constant current to the control module only when the first node is connected to the load and the resistance of the load is less than the preset maximum resistance.

[0038] For further information, see Figure 2 The control module may further include: an optical coupling unit 22, which is arranged between the output end of the constant current source module and the positive electrode of the first diode D1, and the optical coupling unit 22 is also connected to the switch module; the optical coupling unit 22 is used to: output the second level when receiving the constant current output by the constant current source module; when not receiving the constant current output by the constant current source module, the optical coupling unit has no output signal; wherein, when the optical coupling unit 22 outputs the second level and the comparison unit 21 outputs the first level, the second level output by the optical coupling unit 22 is pulled to the first level, so that the switch module controls the first voltage source Vcc1 not to supply power to the load Rx; when the optical coupling unit 22 outputs the second level and the comparison unit 21 outputs the second level, the switch module can control the first voltage source Vcc1 to supply power to the load Rx.

[0039] As can be seen, in the above circuit, an optocoupler unit is further provided between the output end of the constant current source module and the anode of the first diode, and the optocoupler unit and the comparison unit are both connected to the switch module. When the optocoupler unit receives the constant current output by the constant current source module, it outputs a second level, for example, a high level. When the optocoupler unit outputs the second level, the comparison unit may output the second level or the first level, depending on the relationship between the resistance of the load and the preset minimum resistance.

[0040] For example, when the load resistance is less than or equal to the preset minimum resistance, the first comparator outputs a low level. Since the optocoupler unit outputs a high level, the high level output by the optocoupler unit is pulled down to a low level, so that the level signal received by the switch module is a low level. When the load resistance is greater than the preset minimum resistance and less than the preset maximum resistance, the first comparator outputs a high level. Since the optocoupler unit outputs a high level, the level signal received by the switch module is a high level.

[0041] That is, if the load resistance is between a preset maximum resistance and a preset minimum resistance, the optocoupler unit outputs a high level, and the first comparator outputs a high level. Only when both outputs are high levels will the switch module control the first voltage source to supply power to the load. If either the first comparator or the optocoupler unit outputs a low level, the level signal received by the switch module is also a low level. Therefore, through the combined judgment of the two, false positives can be reduced.

[0042] For further information, see Figure 2 The optical coupling unit 22 may include a photocoupler, a first input terminal I1 of the photocoupler is connected to the output terminal of the constant current source, a first output terminal O1 of the photocoupler is connected to the anode of the first diode D1, and the first input terminal I1 corresponds to the first output terminal O1; a second input terminal I2 of the photocoupler is connected to the second voltage source Vcc2 through a pull-up resistor Rf, a second output terminal O2 of the photocoupler is connected to the switch module, and the second output terminal O2 corresponds to the second input terminal I2, and the constant current is less than the driving current of the photocoupler.

[0043] That is, the optocoupler has four terminals: a first input terminal, a first output terminal, a second input terminal, and a second output terminal. The first input terminal and the first output terminal form a pair of terminals, and the second input terminal and the second output terminal form a pair of terminals. That is, current entering the first input terminal will be output from the first output terminal, and current entering the second input terminal will be output from the second output terminal. The first input terminal is connected to the output terminal of a constant current source. Therefore, when the first input terminal of the optocoupler receives a constant current, the constant current will flow out of the first output terminal and reach the anode of the first diode. The second input terminal of the optocoupler is connected to one end of a pull-up resistor, and the other end of the pull-up resistor is connected to a second voltage source. When the first input terminal receives a constant current, the second voltage source generates a driving current through the pull-up resistor, which in turn drives the current from the second input terminal to the optocoupler, causing the second output terminal to output a second voltage level. The constant current is less than the driving current of the optocoupler. Therefore, as long as the constant current flows into the first input terminal, the second output terminal of the optocoupler will output a second voltage level.

[0044] In one embodiment, the constant current source module can also be used to: when the connection between the load and the ground terminal or the first node is disconnected, no output current is output to the control module, so that the second output terminal of the photoelectric coupler has no output signal and the output terminal of the first comparator has no output signal; the switch module is used to: when the photoelectric coupler has no output signal and the first comparator has no output signal, control the first voltage source not to supply power to the load.

[0045] That is to say, when the connection between the load and the ground terminal is disconnected or the connection between the load and the first node is disconnected, the loop between the output terminal of the constant current source module, the optocoupler unit, the first diode, the positive input terminal of the first comparator, the first node, and the ground terminal is disconnected, that is, the circuit is broken, so there is no constant current in the loop, and then the second output terminal of the optocoupler will not have an output signal, and the output terminal of the first comparator will not have an output signal, so the switch module controls the first voltage source not to power the load.

[0046] In one embodiment, see Figure 2 The constant current source module may include a second comparator U2, a third voltage source Vcc3, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4 and a fifth resistor R5, wherein:

[0047] The first resistor R1 is connected between the positive input terminal of the second comparator U2 and the first input voltage Vin1; the second resistor R2 is connected between the negative input terminal of the second comparator U2 and the output terminal of the constant current source module; the third resistor R3 is connected between the output terminal of the second comparator and the output terminal of the constant current source module, and the resistance of the third resistor is equal to the resistance of the second resistor; the fourth resistor R4 is connected between the negative input terminal of the second comparator and the ground terminal; the fifth resistor R5 is connected between the negative input terminal of the second comparator U2 and the output terminal of the second comparator U2, and the resistance of the fifth resistor R5 is equal to the resistance of the fourth resistor R4; the second comparator U2 is connected to the third voltage source Vcc3, and the voltage value of the third voltage source Vcc3 is equal to the product of the constant current Iout and the preset maximum resistance.

[0048] Wherein, the third resistor is equal to the second resistance, and the fifth resistor is equal to the fourth resistance. These two conditions are to ensure that the constant current source module can output a constant current. The voltage value of the third voltage source is equal to the product between the constant current and the preset maximum resistance, that is, the third voltage source is a constant voltage value, and this voltage value is the product between the constant current and the preset maximum resistance. Therefore, when the resistance of the load is less than the preset maximum resistance, the voltage value of the positive input terminal of the first comparator is less than the voltage value of the third voltage source, and the constant current source module will output a constant current at this time. When the resistance of the load is greater than or equal to the preset maximum resistance, the voltage value of the positive input terminal of the first comparator is greater than or equal to the voltage value of the third voltage source, and the constant current source module will not output a constant current at this time. The voltage value of the third voltage source ensures that the constant current source module outputs a constant current to the control module when the first node is connected to the load and the resistance of the load is less than the preset maximum resistance.

[0049] The magnitude of the constant current is determined by the relationship between the first input voltage and each resistor.

[0050] In one embodiment, see Figure 2 The switch module may include a MOS transistor, the source of the MOS transistor is the input end of the switch module, the gate of the MOS transistor is connected to the first voltage source, the drain of the MOS transistor is connected to the first node, and a second diode D2 is connected in parallel between the gate and drain of the MOS transistor.

[0051] The MOS transistor is, for example, an NMOS transistor. When the source of the NMOS transistor receives a high level, conduction occurs between the gate and drain, and the first voltage source supplies power to the load. When the source of the NMOS transistor receives a low level, conduction occurs between the gate and drain, and the first voltage source does not supply power to the load. It can be seen that using a MOS transistor as a switch module to control whether the first voltage source supplies power to the load is very simple and easy to implement.

[0052] In one embodiment, see Figure 2 A capacitor C1 is connected between the output terminal of the first comparator U1 and the ground terminal.

[0053] It is understandable that a capacitor is provided between the output terminal of the first comparator and the ground terminal to achieve a filtering effect.

[0054] For example, when the load resistance is less than or equal to a preset minimum resistance, the voltage at the positive input of the first comparator is less than or equal to the voltage at the negative input of the first comparator, resulting in the first comparator outputting a low level. At this point, the optocoupler is in the on state, and the second output outputs a high level. However, this high level is pulled down by the low level output of the first comparator, preventing the NMOS transistor from turning on, resulting in a cutoff state between the gate and drain. When the load resistance is greater than or equal to a preset maximum resistance, the voltage at the positive input of the first comparator is greater than the supply voltage of the second comparator in the constant current source module, i.e., the voltage of the third voltage source. Consequently, no current flows in the loop formed by the output of the constant current source module, the first input and output of the optocoupler, the first diode, the positive input of the first comparator, the first node, the load, and the ground. This means the loop is open, resulting in no output signal from the second output of the optocoupler or the output of the first comparator. Consequently, the gate and drain of the NMOS transistor are cutoff. Therefore, in both of the above situations, the first voltage source does not power the load. When the resistance of the load is less than the preset maximum resistance and greater than the preset minimum resistance, the voltage value at the positive input of the first comparator is less than the third voltage source, so there is a constant current in the circuit and the photoelectric coupler outputs a high level. Moreover, the voltage value at the positive input of the first comparator is greater than the voltage value at the negative input of the first comparator, so the first comparator outputs a high level. Therefore, the gate and drain of the NMOS tube are in the on state, and the first voltage source supplies power to the load. After a period of normal power supply, when the user unplugs the load, the circuit where the load is located is disconnected, that is, the circuit is broken. At this time, there is no current in the above-mentioned circuit, and then the photoelectric coupler will not have an output signal, and the first comparator will not have an output signal. Therefore, the gate and drain of the NMOS tube are in the cut-off state, and the first voltage source stops supplying power to the load.

[0055] It can be seen that based on the above active Ethernet driver circuit, it is possible to detect whether the resistance of the load is within the normal range, and to power the load if it is within the normal range, and not to power the load if it is not within the normal range. When the load is unplugged from the active Ethernet port, power supply to the load is stopped.

[0056] As can be seen, the active Ethernet driver circuit provided in the embodiments of the present invention determines whether the connected load is disconnected and whether the load resistance exceeds a preset maximum resistance by determining the current. It also determines whether the load resistance exceeds a preset minimum resistance by comparing the voltage. The embodiments of the present invention implement the logic for determining whether the load resistance is within the normal range and for powering the load when it is within the normal range solely through hardware circuitry, without involving software logic. This eliminates the need for high-cost components with software logic capabilities, such as processors and controllers, thereby reducing costs.

[0057] The various embodiments of the present invention are described in a progressive manner. Similar portions between the various embodiments can be referred to in conjunction with each other. Each embodiment focuses on the differences between the other embodiments. In particular, the device embodiments are generally similar to the method embodiments, so their description is relatively simple. For relevant portions, refer to the description of the method embodiments.

[0058] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent replacements, improvements, etc. made on the basis of the technical solution of the present invention should be included in the scope of protection of the present invention.

Claims

1. An active Ethernet driver circuit, characterized in that: It includes a constant current source module, a control module and a switch module connected in sequence, wherein the switch module is arranged between a first voltage source and a first node, and the first node is used to connect to a load; wherein: The constant current source module is configured to output a constant current to the control module when the first node is connected to the load and the resistance of the load is less than a preset maximum resistance; The control module is configured to: upon receiving the constant current, output a corresponding level signal to the switch module according to a magnitude relationship between the resistance of the load and a preset minimum resistance; The switch module is configured to control whether the first voltage source supplies power to the load according to the received level signal.

2. The active Ethernet driving circuit according to claim 1, characterized in that: The constant current source module is further configured to: output no current to the control module when the resistance of the load is greater than or equal to the preset maximum resistance; The control module is further configured to: not output a level signal when the constant current is not received; The switch module is further configured to control the first voltage source to not supply power to the load when the level signal is not received.

3. The active Ethernet driving circuit according to claim 1, wherein: The control module includes a comparison unit, and the comparison unit includes a first comparator, wherein: The positive input terminal of the first comparator is connected to the output terminal of the constant current source module and the first node, and the load is connected between the first node and the ground terminal; the voltage value of the negative input terminal of the first comparator is the product of the constant current and the preset minimum resistance; the output terminal of the first comparator is connected to the switch module; when the control module receives the constant current, the voltage value of the positive input terminal of the first comparator is the product of the constant current and the resistance of the load; The first comparator is specifically used to: when receiving the constant current, if the resistance of the load is less than or equal to the preset minimum resistance, then the voltage value of the positive input terminal of the first comparator is less than or equal to the voltage value of the negative input terminal of the first comparator, and the level signal output by the first comparator is a first level, so that the switch module controls the first voltage source not to supply power to the load; when receiving the constant current, if the resistance of the load is greater than the preset minimum resistance, then the voltage value of the positive input terminal of the first comparator is greater than the voltage value of the negative input terminal of the first comparator, and the level signal output by the first comparator is a second level, so that the switch module controls the first voltage source to supply power to the load.

4. The active Ethernet driving circuit according to claim 3, characterized in that: The comparison unit also includes a first diode, which is arranged between the positive input terminal of the first comparator and the output terminal of the constant current source module, and the anode of the first diode is connected to the output terminal of the constant current source module, and the cathode of the first diode is connected to the positive input terminal of the first comparator.

5. The active Ethernet driving circuit according to claim 4, characterized in that: The control module further includes: an optical coupling unit, which is arranged between the output end of the constant current source module and the anode of the first diode, and is also connected to the switch module; the optical coupling unit is configured to: output the second level when receiving the constant current output by the constant current source module; and output no signal when not receiving the constant current output by the constant current source module; When the optocoupler unit outputs the second level and the comparison unit outputs the first level, the second level output by the optocoupler unit is pulled to the first level, so that the switch module controls the first voltage source not to supply power to the load; when the optocoupler unit outputs the second level and the comparison unit outputs the second level, the switch module can control the first voltage source to supply power to the load.

6. The active Ethernet driving circuit according to claim 5, characterized in that: The optocoupler unit includes a photocoupler, a first input end of the photocoupler is connected to the output end of the constant current source, a first output end of the photocoupler is connected to the anode of the first diode, and the first input end and the first output end correspond to each other; a second input end of the photocoupler is connected to a second voltage source through a pull-up resistor, a second output end of the photocoupler is connected to the switch module, and the second output end corresponds to the second input end, and the constant current is less than the driving current of the photocoupler.

7. The active Ethernet driving circuit according to claim 6, characterized in that: The constant current source module is further configured to: when the connection between the load and the ground terminal or the first node is disconnected, output no current to the control module, so that the second output terminal of the photoelectric coupler has no output signal and the output terminal of the first comparator has no output signal; the switch module is configured to: when the photoelectric coupler has no output signal and the first comparator has no output signal, control the first voltage source to not supply power to the load.

8. The active Ethernet driving circuit according to claim 1, characterized in that: The constant current source module includes a second comparator, a third voltage source, a first resistor, a second resistor, a third resistor, a fourth resistor and a fifth resistor, wherein: The first resistor is connected between the positive input terminal of the second comparator and the first input voltage; The second resistor is connected between the negative input terminal of the second comparator and the output terminal of the constant current source module; The third resistor is connected between the output terminal of the second comparator and the output terminal of the constant current source module, and the resistance of the third resistor is equal to the resistance of the second resistor; The fourth resistor is connected between the negative input terminal of the second comparator and the ground terminal; The fifth resistor is connected between the negative input terminal of the second comparator and the output terminal of the second comparator, and the resistance of the fifth resistor is equal to the resistance of the fourth resistor; The second comparator is connected to the third voltage source, and a voltage value of the third voltage source is equal to a product of the constant current and the preset maximum resistance value.

9. The active Ethernet driving circuit according to claim 1, characterized in that: The switch module includes a MOS transistor, a source of the MOS transistor being the input end of the switch module, a gate of the MOS transistor being connected to the first voltage source, a drain of the MOS transistor being connected to the first node, and a second diode being connected in parallel between the gate and drain of the MOS transistor.

10. The active Ethernet driving circuit according to claim 3, characterized in that: A capacitor is connected between the output terminal of the first comparator and the ground terminal.

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