TWI427963B - Protection circuit and powered device in ethernet - Google Patents

Description

Protection circuit and Ethernet equipment

The present invention relates to a Power over Ethernet (PoE) system, and more particularly to a protection circuit for an Ethernet power supply system and an Ethernet power supply device having the protection circuit.

Generally, Ethernet devices, routers, hubs, and other Ethernet devices (Power Devices, PD) can directly access the local power supply to obtain stable and continuous power supply. However, in general, to prevent communication interruption due to local power interruption, PoE technology can also be used to power the PD.

PoE technology is a technology with broad practical prospects. It is based on the IEEE 802.3af standard proposed by the Institute of Electrical and Electronics Engineers (IEEE), allowing Power Sourcing Equipment (PSE) to pass the same The root Ethernet cable simultaneously transmits data to the PD and directly supplies power. Specifically, the PSE includes a backup power source such as a battery, an Ethernet switch, and a PoE hub. Thus, if the local power supply is interrupted, the battery can sequentially supply power to the PD through the Ethernet switch and the PoE hub.

Specifically, when the PD is simultaneously connected to the local power supply and the PSE, if the local power supply is normally powered, the PSE is selected or the PSE and the local power supply are used to supply power to the PD. The PSE is easily exhausted and needs to be charged to the backup power supply of the PSE at regular intervals. Otherwise, the PSE may not be able to power the PD as a backup power source when the local power supply is interrupted. Therefore, the PoE system automatically selects the local power source as the main power source and cuts off the load of the backup power supply of the PSE, so that the PSE enters the idle mode (Idle State). According to the IEEE 802.3af standard, in idle mode, the PSE checks the characteristic resistance of the load every 2 seconds to determine if there is a valid PD. If a valid PD is detected, the PSE will rank the PD's power. After successful detection and grading, the PSE will enter the normal power supply mode. In actual operation, the PSE needs to go through at least 3.8 seconds to enter the normal power supply mode from the idle mode. Therefore, at the moment of local power interruption, the PD will shut down and restart, causing communication interruption.

In view of this, it is necessary to provide a protection circuit that prevents an instantaneous communication interruption of a local power supply interruption.

A protection circuit for an Ethernet power device, the Ethernet power device comprising a first conversion circuit, a first diode and a second diode. The first conversion circuit includes a first input terminal for converting a voltage input by the first input terminal into a rated operating voltage of the Ethernet power device. The anode of the first diode is connected to a local power source, and the cathode of the first diode is connected to the first input. The anode of the second diode is connected to an Ethernet power supply device, and the cathode is connected to the first input. The voltage supplied by the local power source to the first diode is higher than the voltage supplied by the Ethernet power supply device to the second diode. The protection circuit includes a constant current source for continuously drawing currents of more than 10 mA of the Ethernet power supply during the normal power supply of the local power source.

In addition, the present invention also provides an electrical device for an Ethernet network.

An Ethernet power device includes a first conversion circuit, a first diode, and a second diode. The first conversion circuit includes a first input terminal for converting a voltage input by the first input terminal into a rated operating voltage of the Ethernet power device. The anode of the first diode is connected to a local power source, and the cathode of the first diode is connected to the first input. The anode of the second diode is connected to an Ethernet power supply device, and the cathode is connected to the first input. The voltage supplied by the local power source to the first diode is higher than the voltage supplied by the Ethernet power supply device to the second diode. The Ethernet power device further includes a constant current source for continuously drawing current of 10 mA or more of the Ethernet power supply device during normal power supply of the local power source.

When the local power source is normally powered, the first diode is forward biased because the voltage supplied by the local power source to the first diode is higher than the voltage supplied by the Ethernet power supply device to the second diode. The second diode is reverse biased, the local power source is in communication with the path between the first input terminal, and the path between the second output terminal and the first input terminal is disconnected. The network power device captures the power of the local power source and cannot extract the power of the Ethernet power supply device. At the same time, the constant current source continuously draws current of more than 10 mA of the Ethernet power supply device, and according to the IEEE 802.3af standard, as long as the Ethernet power supply device detects that the current flowing to the Ethernet power device is greater than 10 mA, The Ethernet power supply equipment will remain in the normal power supply mode. In this way, when the local power supply is interrupted, the Ethernet power supply device can immediately supply power to the Ethernet power device, thereby avoiding the interruption of the communication interruption of the local power supply.

100‧‧‧PoE system

10‧‧‧PSE

20‧‧‧Local power supply

30‧‧‧PD

310‧‧‧First conversion circuit

312‧‧‧ first input

314‧‧‧ first output

320‧‧‧Second conversion circuit

322‧‧‧second input

324‧‧‧second output

330‧‧‧Power switch control circuit

332‧‧‧Power terminal

334‧‧‧Control terminal

340‧‧‧Power switch

342‧‧‧Connected end

344‧‧‧Controlled

350‧‧‧ constant current source

FIG. 1 is a circuit block diagram of an Ethernet power device applied to an Ethernet power supply system according to a preferred embodiment of the present invention.

2 is a circuit diagram of a protection circuit in accordance with a preferred embodiment of the present invention.

Referring to FIG. 1, a PoE system 100 in accordance with a preferred embodiment of the present invention includes a PSE 10, a local power source 20, and a PD 30. The PD 30 includes a first conversion circuit 310, a first diode D1, a second conversion circuit 320, a second diode D2, a power switch control circuit 330, a power switch 340, and a constant current source ( Current sink) 350.

The first conversion circuit 310 includes a first input terminal 312 and a first output terminal 314 for converting the voltage input by the first input terminal 312 into the rated operating voltage Vr of the PD 30 and outputted by the first output terminal 314 to The PD 30 itself is powered. The anode of the first diode D1 is connected to the local power source 20, and the cathode thereof is connected to the first input terminal 312. The local power source 20 is for supplying a power having a first input voltage Vin1 to the anode of the first diode D1.

The second conversion circuit 320 includes a second input terminal 322 and a second output terminal 324 for converting the voltage input by the second input terminal 322 into a second input voltage Vin2 and outputted by the second output terminal 324. A second input 322 is coupled to the PSE 10 for providing a first input 312 with a power input having a predetermined voltage Vp. Specifically, the PSE 10 supplies power to the second conversion circuit 320 through a Media Dependent Interface (MDI) and an RJ45 connector. The anode P2 and the second output end 324 of the second diode D2 Connected, the negative pole N2 is connected to the first input terminal 312.

The first input voltage Vin1 is greater than the second input voltage Vin2. Thus, when the local power source 20 is normally powered, the first diode D1 is forward biased, the second diode D2 is reverse biased, the local power source 20 is in communication with the first input terminal 312, and the second The path between the output 324 and the first input 312 is disconnected, and the PD 30 draws power from the local power source 20 and cannot draw power from the PSE 10. In the present embodiment, the rated operating voltage Vr of the PD 30 is 3.3V, the first input voltage Vin1 is 12V, the second input voltage Vin2 is 10V, and the predetermined voltage Vp is 48V.

The power switch control circuit 330 includes a power terminal 332 connected to the local power source 20 and a control terminal 334 for outputting a close control signal from the control terminal 334 and a low potential at the power terminal 332 when the power terminal 332 obtains a high potential input. A disconnection control signal is output by the control terminal 334 at the time of input.

The power switch 340 includes two connection ends 342 and one controlled end 344. The two connecting ends 342 are respectively connected to the second output end 324 and the constant current source 350, and the controlled end 344 is connected to the control end 334. The power switch 340 is configured to connect the two connection ends 342 when the controlled terminal 344 receives the closing control signal of the control terminal 334, so that the constant current source 350 draws the power of the PSE 10; and the control terminal 344 receives the control terminal 334. When the control signal is disconnected, the two connection terminals 342 are disconnected, so that the constant current source 350 cannot capture the power of the PSE 10.

According to the IEEE 802.3af standard, in order to maintain the PSE 10 in the normal power supply mode, the PD 30 should release a Maintain Power Signature (MPS). The DC power supply flowing through the PD 30 can be made larger than 10 mA. For MPS. Therefore, as long as the constant current source 350 is set so that its inflow current is greater than 10 mA, the PSE 10 can always be in the normal power supply mode.

Thus, at the moment when the local power source 20 is interrupted, the first diode D1 becomes reverse biased, the second diode D2 becomes forward biased, and the path between the local power source 20 and the first input terminal 312 is instantaneously disconnected. The path between the second output terminal 324 and the first input terminal 312 is instantaneously connected, and the PSE 10 can immediately supply power to the PD 30 to prevent the local power source 20 from interrupting the instantaneous communication interruption.

In order to reduce the power consumption of the PSE 10, the constant current source 350 should be set so that its inflow current is as small as possible. The inflow current of the constant current source 350 used in the present embodiment is slightly larger than 10 mA.

In addition, after the local power source 20 is interrupted, the power terminal 332 of the power switch control circuit 330 obtains a low potential input, and the two connection terminals 342 of the power switch 340 are disconnected, and the constant current source 350 no longer draws the power of the PSE 10, and also reduces the PSE. 10 power consumption. Of course, in order to reduce the complexity of the circuit and the manufacturing cost, in other embodiments, the power switch control circuit 330 and the power switch 340 may not be used, only the constant current source 350 is used, and the constant current source 350 directly and the second output end 324 connections.

Referring to FIG. 2, the power switch control circuit 330 of the preferred embodiment of the present invention includes a voltage stabilizing chip U (such as 78D05L). The voltage stabilizing chip U includes an input terminal Vin connected to the local power source 20 (ie, the input is Vin1), an output terminal Vout, and a ground terminal GND. The input terminal Vin of the voltage stabilizing chip U constitutes the power terminal 332 of the power switch control circuit 330. The output terminal Vout constitutes the control terminal 334 of the power switch control circuit 330. The regulator chip U is used to input the first input from the input terminal Vin The input voltage Vin1 is converted into an enable signal Vsw and outputted by the output terminal Vout. In the present embodiment, when the enable signal Vsw is at a high potential (for example, 5 V), the control signal is closed, and when the enable signal Vsw is at a low potential (0 V), the control signal is off. Specifically, the power switch control circuit 330 may further include two bypass capacitors C. The input terminal Vin and the output terminal Vout of the voltage stabilizing chip U are respectively grounded through a bypass capacitor C for filtering.

The power switch 340 includes a first NPN transistor Q1, a third resistor R3, a fourth resistor R4, a bypass capacitor C, a second NPN transistor Q2, a fifth resistor R5 and a third NPN transistor Q3. The base of the first NPN transistor Q1 is connected as the controlled terminal 344 of the power switch 340 to the output terminal Vout of the voltage stabilizing chip U, and the collector thereof is connected to the PSE 10 through the third resistor R3 (ie, the input is Vin2), and the emitter is emitted. Extremely grounded. The collector of the first NPN transistor Q1 is connected to the base of the second NPN transistor Q2 via the fourth resistor R4, and the base of the second NPN transistor Q2 is simultaneously grounded via the bypass capacitor C. The collector of the second NPN transistor Q2 is connected to the base of the third NPN transistor Q3, and its emitter is grounded. The collector of the third NPN transistor Q3 is connected to the PSE 10 as a connection terminal 342 of the power switch 340 (i.e., the input is Vin2), and its emitter is connected to the constant current source 350 as the other connection terminal 342 of the power switch 340. Thus, when the enable signal Vsw is at a high potential (closed control signal), the first NPN transistor Q1 is turned on, the second NPN transistor Q2 is turned off, the third NPN transistor Q3 is turned on, and the two connection ends 342 of the power switch 340 are connected. When the enable signal Vsw is low (open control signal), the first NPN transistor Q1 of the power switch 340 is turned off, the second NPN transistor Q2 is turned on, the third NPN transistor Q3 is turned off, and two of the power switches 340 are turned off. The connection end 342 is disconnected.

The constant current source 350 is a current negative feedback circuit including a sixth resistor R6, a fourth NPN transistor Q4, a fifth NPN transistor Q5 and a seventh resistor R7. A connection end 342 of the power switch 340 is connected to the collector of the fourth NPN transistor Q4, and is connected to the base of the fourth NPN transistor Q4 and the collector of the fifth NPN transistor Q5 through the sixth resistor R6. The emitter of the fourth NPN transistor Q4 is connected to the base of the fifth NPN transistor Q5 and grounded through the seventh resistor R7. The emitter of the fifth NPN transistor Q5 is grounded. Thus, when the current flowing through the seventh resistor R7 increases, the base voltage of the fifth NPN transistor Q5 increases, and under the current amplification of the fifth NPN transistor Q5, the current flowing through the sixth resistor R6 increases. The base voltage of the fourth NPN transistor Q4 is made smaller, and the current flowing through the base of the fourth NPN transistor Q4 becomes smaller. Under the amplification of the fourth NPN transistor Q4, the current flowing through the collector of the fourth NPN transistor Q4 is reduced. Small, which reduces the current flowing through the seventh resistor R7. When the current flowing through the seventh resistor R7 increases, the opposite is true. That is, the current flowing through the seventh resistor R7 is stabilized.

In summary, the present invention has indeed met the requirements of the invention patent, and has filed a patent application according to law. However, the above description is only a preferred embodiment of the present invention, and it is not possible to limit the scope of the patent application of the present invention. Equivalent modifications or variations made by those skilled in the art in light of the spirit of the present invention, for example, the scattering portion may include a lattice pattern surrounded by a plurality of first strip-shaped grooves and distributed along the optical axis of the lens. A spiral pattern composed of a plurality of second strip-shaped grooves in a radial spiral shape, etc., should be included in the following patent application.

100‧‧‧PoE system

10‧‧‧PSE

20‧‧‧Local power supply

30‧‧‧PD

310‧‧‧First conversion circuit

312‧‧‧ first input

314‧‧‧ first output

320‧‧‧Second conversion circuit

322‧‧‧second input

324‧‧‧second output

330‧‧‧Power switch control circuit

332‧‧‧Power terminal

334‧‧‧Control terminal

340‧‧‧Power switch

342‧‧‧Connected end

344‧‧‧Controlled

350‧‧‧ constant current source

Claims (8)

A protection circuit for an Ethernet power device, the Ethernet power device includes a first conversion circuit, a first diode and a second diode; the first conversion circuit includes a first The input end is configured to convert the voltage input by the first input terminal into a rated working voltage of the electrical device of the Ethernet; the positive pole of the first diode is connected to a local power source, and the negative pole thereof and the first input end Connecting, the positive pole of the second diode is connected to an Ethernet power supply device, and the negative pole is connected to the first input end; the voltage supplied by the local power source to the first diode is higher than the power supply device of the Ethernet network a voltage supplied to the second diode; the protection circuit includes a constant current source for continuously drawing current of 10 mA or more of the Ethernet power supply during normal power supply of the local power source; the protection circuit further includes a power switch a control circuit and a power switch; the power switch control circuit includes a power terminal connected to the local power source and a control terminal for obtaining a high potential input of the local power source at the power terminal When the incoming terminal outputs a closing control signal, when the local power interruption causes the power terminal to receive a low potential input, the control terminal outputs a disconnection control signal; the power switch includes two power supplies respectively connected to the Ethernet network. a connecting end of the device and the constant current source and a controlled end connected to the control end; the two connecting ends are connected when the controlled end obtains the closing control signal, and the disconnecting control is obtained at the controlled end The signal is disconnected. The protection circuit of claim 1, wherein the constant current source comprises a sixth resistor, a fourth NPN transistor, and a fifth NPN three. a pole tube and a seventh resistor; a connection end of the power switch is connected to the collector of the fourth NPN transistor, and passes through the sixth resistor and the base of the fourth NPN transistor and the collector of the fifth NPN transistor The emitter of the fourth NPN transistor is connected to the base of the fifth NPN transistor and grounded through the seventh resistor; the emitter of the fifth NPN transistor is grounded. The protection circuit of claim 1, wherein the power switch control circuit comprises a voltage regulator chip and two bypass capacitors; the voltage regulator chip includes an input terminal connected to the local power source as the power source terminal. An output terminal connected to the controlled terminal and a grounded ground terminal; the input terminal and the output terminal are respectively grounded through a bypass capacitor. The protection circuit of claim 1, wherein the power switch comprises a first NPN transistor, a third resistor, a fourth resistor, a bypass capacitor, a second NPN transistor, and a fifth resistor. And a third NPN transistor; the base of the first NPN transistor is connected to the control terminal as the controlled terminal, and the collector is connected to the Ethernet power supply device through the third resistor, and the emitter is grounded; The collector of an NPN transistor is connected to the base of the second NPN transistor via the fourth resistor, and the base of the second NPN transistor is simultaneously grounded via the bypass capacitor; the collector of the second NPN transistor passes through the a fifth resistor is connected to a base of the third NPN transistor, and an emitter thereof is grounded; a collector of the third NPN transistor is connected as a connection end to the Ethernet power supply device, and an emitter thereof serves as another connection terminal and the constant Stream source connection. An Ethernet power device includes a first conversion circuit, a first diode and a second diode; the first conversion circuit includes a first input The input end is configured to convert the voltage input by the first input terminal into a rated working voltage of the electrical device of the Ethernet; the positive pole of the first diode is connected to a local power source, and the negative pole and the first input end Connecting, the positive pole of the second diode is connected to an Ethernet power supply device, and the negative pole is connected to the first input end; the voltage supplied by the local power source to the first diode is higher than the power supply device of the Ethernet network a voltage supplied to the second diode; the Ethernet power device further includes a constant current source for continuously drawing current of 10 mA or more of the Ethernet power supply device during normal power supply of the local power source; The network power device further includes a power switch control circuit and a power switch; the power switch control circuit includes a power terminal connected to the local power source and a control terminal for obtaining a high potential input of the local power source at the power source end When the control terminal outputs a closing control signal, the control terminal outputs a disconnection control signal when the local power supply is interrupted so that the power terminal receives a low potential input; The switch includes two connecting ends respectively connected to the Ethernet power supply device and the constant current source, and a controlled end connected to the control end; the two connecting ends are connected when the controlled end obtains the closing control signal And disconnected when the controlled terminal obtains the disconnection control signal. The electrical power device of the Ethernet according to claim 5, wherein the constant current source comprises a sixth resistor, a fourth NPN transistor, a fifth NPN transistor and a seventh resistor; the power switch One connection end is connected to the collector of the fourth NPN transistor, and is connected to the base of the fourth NPN transistor and the collector of the fifth NPN transistor through the sixth resistor; the emitter of the fourth NPN transistor The base of the fifth NPN transistor is connected to the ground through the seventh resistor; the emitter of the fifth NPN transistor is grounded. The power-on device of the Ethernet device of claim 6, wherein the power switch control circuit comprises a voltage regulator chip and two bypass capacitors; the voltage regulator chip includes a power supply terminal and the local power source The input end of the connection, an output terminal connected to the controlled end as the control end, and a grounded ground end; the input end and the output end are respectively grounded through a bypass capacitor. The electrical power device of the Ethernet according to claim 6, wherein the power switch comprises a first NPN transistor, a third resistor, a fourth resistor, a bypass capacitor, and a second NPN transistor. a fifth resistor and a third NPN transistor; the base of the first NPN transistor is connected to the control terminal as the controlled terminal, and the collector is connected to the Ethernet power supply device through the third resistor, and the emitter thereof Grounding; the collector of the first NPN transistor is connected to the base of the second NPN transistor via the fourth resistor, and the base of the second NPN transistor is simultaneously grounded via the bypass capacitor; the set of the second NPN transistor The electrode is connected to the base of the third NPN transistor via the fifth resistor, and the emitter thereof is grounded; the collector of the third NPN transistor is connected as a connection end to the Ethernet power supply device, and the emitter is used as another connection The end is connected to the constant current source.