Circuit and power supply method for power receiving equipment based on power over Ethernet
By designing a circuit for powered-over-Ethernet powered equipment, using the combination of comparator and switch, the problem of auxiliary power affecting the POE power-on logic is solved, and the simultaneous existence and normal operation of auxiliary power and POE power supply are achieved.
Patent Information
- Application Number
- CN202411547664.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-01
- Publication Date
- 2025-02-11
AI Technical Summary
In powered devices powered over Ethernet, the presence of auxiliary power supplies will affect the POE power-on logic and even cause the POE power-on logic to fail.
A circuit is designed, including a first power supply terminal, a second power supply terminal, a power output terminal, a switch and a comparator. By comparing the first voltage at the first power supply terminal with a predetermined threshold value and outputting a conduction signal, the switch is turned on based on the conduction signal, thereby supporting the simultaneous existence of auxiliary power supply and POE power supply.
On the premise that the POE that supports the power-on logic of the power-on device normally performs the power-on logic, it can support both auxiliary power supply and POE power supply, avoiding the failure of the POE power-on logic.
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Figure CN119420588A_ABST
Abstract
Description
Technical Field
[0001] Embodiments of the present disclosure generally relate to Power Over Ethernet (POE), and more particularly to a circuit, a power supply system, and a power supply method for a powered device based on POE. Background Art
[0002] In Ethernet networks, Power over Ethernet (POE) is widely used in Ethernet network devices, such as voice IP phones, routers (such as wireless routers), monitoring and security equipment, etc. In many POE applications, the powered device (PD) also uses an auxiliary power supply to ensure that the powered device can continue to be powered even if the POE power supply is disconnected.
[0003] To support the auxiliary power solution, the control chip installed on the powered device is generally equipped with an auxiliary power pin to provide the auxiliary power requirement. However, the existence of the auxiliary power will affect the POE power-on logic executed by the powered device, and even cause the POE power-on logic to fail. Summary of the invention
[0004] Embodiments of the present disclosure provide a circuit, a power supply system, and a power supply method for a powered device based on Power over Ethernet, aiming to solve one or more of the above-mentioned problems and other potential problems.
[0005] According to a first aspect of the present disclosure, a circuit for a powered device based on Ethernet power supply is provided. The circuit comprises: a first power supply terminal; a second power supply terminal, adapted to be connected to an Ethernet power supply terminal; a power output terminal, adapted to be connected to a load of the powered device; a switch, arranged in series between the ground and the power output terminal; and a first comparator, configured to compare a first voltage at the first power supply terminal with a first predetermined threshold value and output a conduction signal based on the first voltage being greater than the first predetermined threshold value, wherein the switch is turned on based on the conduction signal.
[0006] According to the present disclosure, on the premise of supporting the normal execution of the power-on logic of the POE of the powered device, the auxiliary power supply and the POE power supply can also be supported simultaneously.
[0007] In some embodiments, the circuit also includes a constant current source, wherein, when the first power supply terminal is connected to the capacitor, the constant current source is connected to the first power supply terminal and is configured to charge the capacitor; the positive electrode of the capacitor is connected to the first power supply terminal, and the negative electrode of the capacitor is grounded.
[0008] In some embodiments, the circuit also includes a control unit, which is configured to obtain a second voltage at the second power supply terminal and execute power-on logic based on the Ethernet protocol and the second voltage; wherein the control unit is also connected to the output terminal of the first comparator and to the control terminal of the switch, and is configured to control the conduction of the switch based on the conduction signal.
[0009] In some embodiments, the circuit also includes a second comparator configured to compare the first voltage at the first power supply terminal with a second predetermined threshold greater than the first predetermined threshold, and output a disable signal based on the first voltage being greater than the second predetermined threshold, wherein the switch is turned off based on the disable signal.
[0010] In some embodiments, the Ethernet power supply includes a first pair of power lines and a second pair of power lines, the positive line of the first pair of power lines is connected to the positive terminal of the load, the positive line of the second pair of power lines is connected to the second power terminal, and the negative line of the first pair of power lines is connected to the negative line of the second pair of power lines.
[0011] In some embodiments, the second power terminal is further configured to be suitable for being connected to a positive terminal of an auxiliary power source for providing auxiliary power to the powered device.
[0012] In some embodiments, the first power terminal is further configured to be suitable for being connected to a positive terminal of an auxiliary power source for providing auxiliary power to the powered device.
[0013] In some embodiments, the circuit further comprises a second switch connected in parallel with the switch.
[0014] In some embodiments, the switch includes at least one of a triode, a field effect transistor and a thyristor, and / or the second switch includes a diode.
[0015] According to a second aspect of the present disclosure, a powered device based on Power over Ethernet is provided, comprising the circuit according to any one of the first aspects.
[0016] According to a third aspect of the present disclosure, a power supply system based on Power over Ethernet is provided, comprising: a Power over Ethernet device; and a powered device interconnected with the Power over Ethernet device via a network cable, wherein the powered device comprises a circuit according to any one of the first aspects.
[0017] According to a fourth aspect of the present disclosure, a power supply method is provided. The power supply method includes: connecting the positive electrode of a capacitor to a first power supply terminal; connecting the first positive line in a first pair of power supply terminals in an Ethernet power supply terminal to the positive terminal of a load of a powered device based on Ethernet power supply; connecting the second positive line in a second pair of power supply terminals in the Ethernet power supply terminal to the second power supply terminal; connecting the first negative line in the first pair of power supply terminals in the Ethernet power supply terminal and the second negative line in the second pair of power supply terminals together and connecting to the negative electrode of the capacitor; connecting the positive electrode of an auxiliary power supply to the second power supply terminal and the positive terminal of the load; comparing a first voltage at the first power supply terminal with a first predetermined threshold; and outputting a conduction signal to turn on a switch based on the first voltage being greater than the first predetermined threshold, wherein the switch is set between the negative electrode of the capacitor and the negative terminal of the powered device and is turned on based on the conduction signal.
[0018] According to a fourth aspect of the present disclosure, a power supply method is provided. The power supply method includes: connecting the positive electrode of a capacitor to a first power supply terminal; connecting the first positive line of a first pair of power supply terminals in an Ethernet power supply terminal to the positive terminal of a load of a powered device based on Ethernet power supply; connecting the second positive line of a second pair of power supply terminals in the Ethernet power supply terminal to the second power supply terminal; connecting the first negative line of the first pair of power supply terminals in the Ethernet power supply terminal and the second negative line of the second pair of power supply terminals together and connecting to the negative electrode of the capacitor; connecting the negative electrode of the capacitor to the negative terminal of the load via a second switch; connecting the positive electrode of an auxiliary power supply to the first power supply terminal and the positive terminal of the load; comparing a first voltage at the first power supply terminal with a first predetermined threshold; outputting a conduction signal to turn on a switch based on the first voltage being greater than the first predetermined threshold, wherein the switch is arranged in parallel with the second switch between the negative electrode of the capacitor and the negative terminal of the load and is configured to be turned on based on the conduction signal; comparing the first voltage at the first power supply terminal with a second predetermined threshold greater than the first predetermined threshold; and outputting a deactivation signal based on the second voltage being greater than a predetermined second threshold, wherein the switch is configured to be turned off based on the deactivation signal. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The above and other objects, features and advantages of the embodiments of the present disclosure will become readily understood by referring to the accompanying drawings and reading the following detailed description. In the accompanying drawings, several embodiments of the present disclosure are shown by way of example and not limitation.
[0020] Figure 1 A schematic diagram of an Ethernet network system according to the present disclosure is shown.
[0021] Figure 2A circuit diagram of a controller of a powered device according to an embodiment of the present disclosure is shown.
[0022] Figure 3 A circuit diagram showing the simultaneous powering of POE power supply and auxiliary power supply according to the first embodiment of the present disclosure is shown.
[0023] Figure 4 A circuit diagram showing the simultaneous powering of POE power supply and auxiliary power supply according to the second embodiment of the present disclosure is shown.
[0024] In the various drawings, the same or corresponding reference numerals represent the same or corresponding parts. DETAILED DESCRIPTION
[0025] The preferred embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the preferred embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present disclosure more thorough and complete, and to fully convey the scope of the present disclosure to those skilled in the art.
[0026] Figure 1 FIG. 1 is a schematic diagram of an Ethernet network system 1 according to the present disclosure. Figure 1 As shown, the Ethernet network 1 includes one or more power sourcing equipment (PSE) 200 and one or more powered devices PD 100a, 100b, 100c, 100d connected via cables supporting the Ethernet protocol. It should be understood that only one PSE 200 and four PDs are shown in the illustrated embodiment, and it should be understood that the number of PSEs and PDs is merely exemplary.
[0027] In applications of Power over Ethernet (POE), the cable usually includes two pairs of power terminals, each pair of power terminals can be rectified into direct current through a rectifier bridge of a power supply equipment (PSE), and power is supplied to the powered device (PD) through each pair of power terminals. However, there are risks in using POE cable power supply, and some powered devices (PD) are usually powered by an additional auxiliary power supply to ensure that the powered device can continue to be powered even if the POE cable is powered off. Traditional powered devices (such as their controllers or control chips) are usually equipped with auxiliary power pins to provide auxiliary power requirements. However, when auxiliary power and POE power supply exist at the same time, the traditional powered device cannot support the POE power-on logic, which exposes the powered device to dangers such as overcurrent. According to the present disclosure, a circuit is provided that can simultaneously support auxiliary power and POE power supply while supporting the normal execution of the power-on logic of the POE of the powered device.
[0028] Figure 2FIG. 1 is a circuit diagram of a controller 110 of a powered device according to an embodiment of the present disclosure. Figure 2 As shown, the controller 110 includes a control unit 40, a first power supply terminal ADP, a second power supply terminal VDD, a power output terminal OUT, and a switch 20. In some embodiments, the control unit 40 can be configured to execute POE power-on logic, for example, configured to detect, classify, mark, and start a series of standard power-ons related to the protocol, such as current limiting. In particular, the control unit 40 can be configured to obtain a second voltage of the second power supply terminal VDD, and execute the power-on logic based on the Ethernet protocol and the second voltage.
[0029] The first power supply terminal ADP may be connected to a capacitor C ADP In some embodiments, the capacitor C ADP The positive electrode is connected to the first power supply terminal ADP, the capacitor C ADP The negative pole can be grounded. The second power supply terminal VDD can be connected to the Ethernet power supply terminal, and the second power supply terminal VDD can indicate the voltage at the Ethernet power supply terminal. The power output terminal OUT can be connected to the load of the powered device. In some embodiments, the power output terminal OUT can be connected to a DC-DC converter provided at the load, and the load is powered via the DC-DC converter. The switch 20 is connected to the power output terminal OUT. The on and off of the load power supply circuit can be controlled by the on and off of the switch 20. In some embodiments, the control unit 40 is connected to the control terminal of the switch 20 and is configured to control the on-state of the switch 20 based on the on signal. In some embodiments, the switch 20 may include at least one of a triode, a field effect transistor and a thyristor. In some embodiments, the switch 20 may also be other circuit modules with overcurrent protection and surge current limiting protection functions.
[0030] The controller 110 further includes a first comparator 10. The first comparator 10 is configured to compare the first voltage at the first power supply terminal ADP with a first predetermined threshold and output a conduction signal based on the first voltage being greater than the first predetermined threshold. The conduction signal may be output to the control unit 40, and the control unit 40 may control the switch 20 to conduct based on the conduction signal.
[0031] In some embodiments, the controller 110 may further include a constant current source 50. The constant current source 50 is connected to the first power supply terminal ADP and is configured to supply a current to the capacitor C before the switch 20 is turned on. ADP Charge. On capacitor C ADP When the first power supply terminal ADP is connected to the first power supply terminal ADP and the first power supply terminal ADP is connected to the constant current source 50, once the controller 110 is started, the controller 110 will automatically supply C ADP In some embodiments, the constant current source may be connected to a power supply of the controller 110, for example.
[0032] In some embodiments, the controller 110 may further include a second comparator 30. The second comparator 30 is configured to compare the first voltage at the first power supply terminal ADP with a second predetermined threshold value, and output a deactivation signal based on the first voltage being greater than the predetermined second threshold value. The control unit 40 may be connected to the output terminal of the second comparator 30, and is configured to turn off the switch 20 based on the deactivation signal.
[0033] In some embodiments, the circuit of the controller 110 may be implemented as an integrated circuit. In other embodiments, the circuit of the controller 110 may be implemented in the form of a circuit board. In the illustrated embodiment, the capacitor C ADP It is illustrated as being separate from the controller 110. It should be understood that this is merely exemplary. ADP May be implemented as part of the controller 110 .
[0034] The controller according to the present disclosure executes the power-on logic according to the Ethernet protocol. When the input voltage VDD exceeds a predetermined voltage, such as 11.6V, this corresponds to the end of the POE detection function. The controller outputs a fixed current to the ADP pin. The fixed current is applied to the capacitor C disposed outside the controller. ADP When the ADP voltage exceeds the predetermined threshold value Vref1, the controller 110 directly turns on the switch 20, allowing the subsequent load to start and start to provide power to the load. According to the present disclosure, the POE power supply and the auxiliary power supply can be allowed to exist at the same time, and the power is still powered on according to the main POE power supply protocol, without affecting a series of standard power-on related to the protocol such as detection, classification, marking and current limiting startup.
[0035] In some embodiments, by selecting an appropriate capacitor C ADP The capacitance and the fixed current are used to achieve synchronization with the standard power-on process. In some embodiments, the protocol power-on is generally required to be completed within a specified time (e.g., <200ms), which can be achieved by properly designing the ADP charging current value and the capacitance C ADP The capacitance value ensures that the ADP voltage does not exceed the threshold Vref1 during the protocol power-on process, thereby not affecting the POE power-on. In some embodiments, after the Ethernet power-on classification stage is completed, a conduction signal is output.
[0036] In some embodiments, if the voltage of VDD is still lower than the predetermined start-up voltage value of the protocol power-on, such as 37.5V, after the power-on exceeds the specified time (e.g., 200ms), this will be considered as auxiliary power supply. In this case, the switch 20 can be controlled to close to supply power to the subsequent load through the auxiliary power supply. This auxiliary power supply mode is suitable for the situation where the voltage of the auxiliary power supply is low, such as less than 30V.
[0037] In some embodiments, when the auxiliary power supply voltage is high, for example, greater than 30V, the switch 20 will limit the maximum current flowing through, resulting in failure to provide full power to the load. In this case, a second comparator can be set to compare the ADP pin voltage with a predetermined threshold value Vref2, and the predetermined threshold value Vref2 can be set to be greater than Vref1. When the ADP pin voltage exceeds Vref2, the power supply path of the switch 20 will be directly disconnected, so that the load power supply is not limited by the maximum current of the switch 20, thereby providing full power to the subsequent load.
[0038] Combine the following Figure 3 and Figure 4 Different application scenarios of the controller according to the embodiments of the present disclosure are further described. Figure 3 A circuit diagram showing the simultaneous powering of POE power supply and auxiliary power supply according to the first embodiment of the present disclosure is shown. Figure 3 It is particularly suitable for the situation where POE power supply and auxiliary power supply exist at the same time and the voltage of the auxiliary power supply 300 is relatively low.
[0039] In some embodiments, Figure 3 As shown, the power supply device 200 may include a power supply 210 and rectifier bridges 220a and 220b. In the illustrated embodiment, the Ethernet power supply includes two pairs of power lines, namely a first pair of power lines and a second pair of power lines. The power supply device 200 can power the powered device 100 through the first pair of power lines and the second pair of power lines. The powered device 100 may include a controller 110, a load 130, and a capacitor C connected to the ADP terminal of the controller. ADP The controller 110 can be connected with Figure 2 The controllers of the illustrated embodiments are the same and detailed description thereof is omitted.
[0040] In some embodiments, Figure 3 As shown, the positive line of the first pair of power supply lines can be connected to the positive terminal of the load 130, and the positive line of the second pair of power supply lines can be connected to the second power supply terminal VDD of the controller 110; the negative line of the first pair of power supply lines is connected to the negative line of the second pair of power supply lines, and can be connected in series with the switch 20 in the controller 110 and connected to the negative electrode of the load 130. The negative line of the first pair of power supply lines and the negative line of the second pair of power supply lines can be connected to the capacitor C ADP In some embodiments, the negative electrode line of the first pair of power supply lines, the negative electrode line of the second pair of power supply lines, the capacitor C ADP The negative pole can be grounded.
[0041] In some embodiments, Figure 3As shown, an auxiliary power supply 300 is also provided, and the auxiliary power supply 300 is configured to provide auxiliary power to the powered device 110. This has benefits when the power supply line of the power supply device 200 fails and / or the load 130 needs a higher power supply. The auxiliary power supply 300 can be a battery and / or a power adapter. The positive pole of the auxiliary power supply 300 can be connected to the VDD terminal and the positive pole line of the second pair of power supply lines. In some embodiments, the auxiliary power supply 300 can be connected to the positive pole line of the VDD terminal and the second pair of power supply lines through a diode 310. The negative pole of the auxiliary power supply 300 can be connected to the negative pole line of the first pair of power supply lines and / or the negative pole line of the second pair of power supply lines.
[0042] In some embodiments, the POE power supply voltage is generally above 38V; when the auxiliary power supply output is less than 38V, it is, for example, 24V. When the powered device 100 is operating, the constant current source 50 is connected to the capacitor C ADP During charging, the ADP voltage rises from 0. When the comparator 10 determines that the ADP voltage is less than the Vref1 threshold, the protocol power-on of the controller 110 of the powered device 100 is not affected. After the comparator 10 determines that the ADP voltage exceeds the threshold Vref1, the control unit 40 turns on the switch 20, thereby supplying power to the subsequent load 130. In this case, even if the POE power supply is disconnected, the auxiliary power supply can provide electrical power to the load alone.
[0043] According to the present disclosure, a power supply method is also provided. The power supply method comprises: connecting a capacitor C ADP The positive electrode of the first pair of power supply terminals in the Ethernet power supply terminal is connected to the first power supply terminal ADP; the first positive line in the first pair of power supply terminals in the Ethernet power supply terminal is connected to the positive terminal of the load 130 based on Ethernet power supply; the second positive line in the second pair of power supply terminals in the Ethernet power supply terminal is connected to the first power supply terminal ADP; the first negative line in the first pair of power supply terminals in the Ethernet power supply terminal and the second negative line in the second pair of power supply terminals are connected together and connected to the capacitor C ADP the negative electrode of the auxiliary power supply 300; connecting the positive electrode of the auxiliary power supply 300 to the second power supply terminal VDD and the positive terminal of the load 130; comparing the first voltage at the first power supply terminal ADP with the first predetermined threshold; and outputting a conduction signal to turn on the switch 20 based on the first voltage being greater than the first predetermined threshold, wherein the switch 20 is set at the capacitor C ADP and the negative terminal of the load 130 and is turned on based on the turn-on signal
[0044] Figure 4 A circuit diagram showing the simultaneous powering of POE power supply and auxiliary power supply according to the second embodiment of the present disclosure is shown. Figure 4 It is particularly suitable for the situation where POE power supply and auxiliary power supply exist at the same time and the voltage of the auxiliary power supply 300 is relatively large. Figure 4 The embodiment shown is Figure 3 The embodiment shown is similar, except that a second switch 60 may also be provided in parallel with the switch 20. In some embodiments, the second switch 60 may be a diode.
[0045] When the auxiliary power supply output is greater than 38 V, for example, 48 V. When the powered device 100 is operating, the constant current source 50 is connected to the capacitor C ADP Charging, the ADP voltage rises from 0. When the comparator 10 determines that the ADP voltage is less than the Vref1 threshold, the protocol power-on of the controller 110 of the powered device 100 is not affected. After the comparator 10 determines that the ADP voltage exceeds the threshold Vref1, the control unit 40 turns on the switch 20, thereby supplying power to the subsequent load 130. When the comparator 30 determines that the ADP voltage exceeds the threshold Vref2, the control unit 40 turns off the switch 20, so that the switch 20 does not work, and the load can be powered by the auxiliary power supply through the second switch 60. In this case, the power supply power of the load will not be limited by power, and in particular, the full output of the auxiliary power supply can be achieved.
[0046] According to the present disclosure, a power supply system based on Power over Ethernet is also provided. The power supply system includes an Ethernet power supply device 200 and a powered device 100 interconnected with the Ethernet power supply device via a network cable, and the powered device 100 includes the controller 110 according to the above aspects.
[0047] According to the present disclosure, a power supply method is also provided. The power supply method comprises: connecting a capacitor C ADP The positive electrode of the first pair of power supply terminals in the Ethernet power supply terminal is connected to the first power supply terminal ADP; the first positive line in the first pair of power supply terminals in the Ethernet power supply terminal is connected to the positive terminal of the load 130 based on Ethernet power supply; the second positive line in the second pair of power supply terminals in the Ethernet power supply terminal is connected to the first power supply terminal ADP; the first negative line in the first pair of power supply terminals in the Ethernet power supply terminal and the second negative line in the second pair of power supply terminals are connected together and connected to the capacitor C ADP The negative pole of capacitor C ADP The negative electrode of the auxiliary power supply 300 is connected to the negative terminal of the load 130 via the second switch 60; the positive electrode of the auxiliary power supply 300 is connected to the first power supply terminal ADP and the positive terminal of the load 130; the first voltage at the first power supply terminal ADP is compared with the first predetermined threshold value; based on the first voltage being greater than the first predetermined threshold value, a conduction signal for turning on the switch 20 is output, wherein the switch 20 and the second switch 60 are arranged in parallel on the capacitor C ADPbetween the negative electrode of and the negative terminal of the load 130, and is configured to be turned on based on the turn-on signal; compares the second voltage at the second power supply terminal VDD with a second predetermined threshold value greater than the first predetermined threshold value; and outputs a disable signal based on that the second voltage is greater than the predetermined second threshold value, and the switch 20 is configured to be turned off based on the disable signal.
[0048] In addition, although each operation is described in a specific order, this should be understood as requiring such operation to be performed in the specific order shown or in a sequential order, or requiring that all illustrated operations should be performed to obtain desired results. Under certain circumstances, multitasking and parallel processing may be advantageous. Similarly, although some specific implementation details are included in the above discussion, these should not be interpreted as limiting the scope of the present disclosure. Some features described in the context of a separate embodiment can also be implemented in a single implementation in combination. On the contrary, the various features described in the context of a single implementation can also be implemented in multiple implementations individually or in any suitable sub-combination mode.
[0049] Although the subject matter has been described in language specific to structural features and / or methodological logical actions, it should be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or actions described above. On the contrary, the specific features and actions described above are merely example forms of implementing the claims.
[0050] The embodiments of the present disclosure have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or technical improvements in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.
Claims
1. A circuit for a powered device based on Power over Ethernet, comprising: A first power supply terminal (ADP); A second power supply terminal (VDD), adapted to be connected to an Ethernet power supply terminal; A power output terminal (OUT), adapted to be connected to a load of the powered device; A switch (20) is arranged in series between the ground and the power output terminal (OUT); as well as The first comparator (10) is configured to compare the first voltage at the first power supply terminal (ADP) with a first predetermined threshold and output a conduction signal based on the first voltage being greater than the first predetermined threshold, wherein the switch (20) is turned on based on the conduction signal.
2. The circuit according to claim 1 further comprises a constant current source (50), wherein: When the first power supply terminal (ADP) is connected to the capacitor (C ADP ), the constant current source (50) is connected to the first power supply terminal (ADP) and is configured to supply the capacitor (C ADP ) is charged; the capacitor (C ADP ) is connected to the first power supply terminal (ADP), the capacitor (C ADP )’s negative terminal is grounded.
3. The circuit according to claim 1, further comprising a control unit (40), the control unit (40) being configured to obtain a second voltage of the second power supply terminal (VDD), and to execute a power-on logic based on the Ethernet protocol and the second voltage; The control unit (40) is also connected to the output terminal of the first comparator (10) and to the control terminal of the switch (20), and is configured to control the conduction of the switch (20) based on the conduction signal.
4. The circuit according to claim 1, further comprising a second comparator (30) configured to compare the first voltage at the first power supply terminal (ADP) with a second predetermined threshold value greater than the first predetermined threshold value, and output a disable signal based on the first voltage being greater than the second predetermined threshold value, The switch (20) is turned off based on the deactivation signal.
5. The circuit according to claim 1, wherein the Ethernet power supply includes a first pair of power lines and a second pair of power lines, the positive line of the first pair of power lines is connected to the positive terminal of the load (130), the positive line of the second pair of power lines is connected to the second power supply terminal (VDD), and the negative line of the first pair of power lines is connected to the negative line of the second pair of power lines.
6. The circuit according to any one of claims 1 to 5, wherein the second power supply terminal (VDD) is further configured to be suitable for being connected to a positive terminal of an auxiliary power supply (300) for providing auxiliary power supply to the powered device.
7. The circuit according to any one of claims 1 to 5, wherein the first power terminal (ADP) is further configured to be suitable for being connected to a positive terminal of an auxiliary power supply (300) for providing auxiliary power to the powered device.
8. The circuit of claim 7, further comprising a second switch (60) connected in parallel with the switch (20).
9. The circuit according to claim 8, wherein the switch (20) comprises at least one of a triode, a field effect transistor and a thyristor, and / or the second switch (60) comprises a diode.
10. A powered device based on Power over Ethernet, comprising the circuit according to any one of claims 1 to 9.
11. A power supply system based on Power over Ethernet, comprising: Power over Ethernet device (200); as well as A powered device (100) interconnected with the Ethernet power supply device via a network cable, wherein the powered device comprises a circuit according to any one of claims 1 to 9.
12. A power supply method, comprising: The capacitor (C ADP ) has a positive electrode connected to a first power supply terminal (ADP); Connecting a first positive line of a first pair of power supply terminals in the Ethernet power supply terminals to a positive terminal of a load of a powered device based on Ethernet power; Connecting a second positive line in a second pair of power supply terminals in the Ethernet power supply terminal to the second power supply terminal (VDD); Connect the first negative line in the first pair of power supply terminals in the Ethernet power supply terminals and the second negative line in the second pair of power supply terminals together and connect to the capacitor (C ADP ) of the negative electrode; Connecting the positive electrode of the auxiliary power supply (300) to the second power supply terminal (VDD) and the positive terminal of the load (130); comparing a first voltage at a first power supply terminal (ADP) to a first predetermined threshold; as well as Based on the first voltage being greater than a first predetermined threshold, a conduction signal for turning on a switch (20) is output, wherein the switch (20) is arranged on the capacitor (C ADP ) and the negative terminal of the power receiving device and is conducted based on the conduction signal.
13. A power supply method, comprising: The capacitor (C ADP ) has a positive electrode connected to a first power supply terminal (ADP); Connecting a first positive line of a first pair of power supply terminals in the Ethernet power supply terminals to a positive terminal of a load of a powered device based on Ethernet power; Connecting a second positive line in a second pair of power supply terminals in the Ethernet power supply terminal to the second power supply terminal (VDD); Connect the first negative line in the first pair of power supply terminals in the Ethernet power supply terminals and the second negative line in the second pair of power supply terminals together and connect to the capacitor (C ADP ) of the negative electrode; The capacitor (C ADP ) is connected to the negative terminal of the load (130) via a second switch (60); Connecting a positive electrode of an auxiliary power source (300) to the first power source terminal (ADP) and a positive electrode terminal of the load (130); comparing a first voltage at a first power supply terminal (ADP) to a first predetermined threshold; Based on the first voltage being greater than a first predetermined threshold, a conduction signal for turning on the switch (20) is output, wherein the switch (20) and the second switch (60) are arranged in parallel on the capacitor (C ADP ) and a negative terminal of the load (130), and is configured to be turned on based on the turn-on signal; comparing a first voltage at the first power supply terminal (ADP) to a second predetermined threshold value greater than the first predetermined threshold value; as well as A disable signal is output based on the second voltage being greater than a predetermined second threshold, and the switch (20) is configured to be turned off based on the disable signal.