U.S. patent application number 11/469815 was filed with the patent office on 2007-08-16 for over-voltage protection circuit.
Invention is credited to Michael Altmann, John R. Camagna, Philip John Crawley, Sajol Ghoshal.
Application Number | 20070189495 11/469815 |
Document ID | / |
Family ID | 37767262 |
Filed Date | 2007-08-16 |
United States Patent
Application |
20070189495 |
Kind Code |
A1 |
Crawley; Philip John ; et
al. |
August 16, 2007 |
OVER-VOLTAGE PROTECTION CIRCUIT
Abstract
A network device comprising an integrated circuit configured for
coupling to lines between a network connector and an Ethernet
physical layer (PHY) and comprising a diode bridge and protection
circuitry integrated onto a common integrated circuit whereby
parasitics in an energy discharge path and stress on the PHY and
the diode bridge are reduced.
Inventors: |
Crawley; Philip John;
(Folsom, CA) ; Ghoshal; Sajol; (El Dorado Hills,
CA) ; Camagna; John R.; (El Dorado Hills, CA)
; Altmann; Michael; (Folsom, CA) |
Correspondence
Address: |
KOESTNER BERTANI LLP
2192 Martin St.
Suite 150
Irvine
CA
92612
US
|
Family ID: |
37767262 |
Appl. No.: |
11/469815 |
Filed: |
September 1, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11207595 |
Aug 19, 2005 |
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11469815 |
Sep 1, 2006 |
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11207602 |
Aug 19, 2005 |
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11469815 |
Sep 1, 2006 |
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Current U.S.
Class: |
379/323 |
Current CPC
Class: |
Y02D 30/50 20200801;
H04L 12/10 20130101; Y02D 50/30 20180101 |
Class at
Publication: |
379/323 |
International
Class: |
H04M 3/00 20060101
H04M003/00 |
Claims
1. A network device comprising: a protection circuit configured for
coupling to lines between a network connector and an Ethernet
physical layer (PHY), the protection circuit comprising a diode
bridge and protection circuitry integrated onto a common integrated
circuit.
2. The network device according to claim 1 further comprising: the
protection circuit configured for coupling lines between the
network connector and the Ethernet physical layer (PHY) that carry
signal and power in a Power-over-Ethernet arrangement.
3. The network device according to claim 1 further comprising: the
protection circuit diode bridge coupled to center taps of an
Ethernet transformer coupled to the lines between the network
connector and the Ethernet physical layer (PHY).
4. The network device according to claim 1 further comprising: the
protection circuit diode bridge coupled to a T-Less Connect.TM.
solid-state transformer coupled to the lines between the network
connector and the Ethernet physical layer (PHY).
5. The network device according to claim 1 further comprising: the
protection circuit comprising: the integrated diode bridge coupled
between a supply line and a reference line; the integrated
protection circuitry coupled between the supply line and the
reference line; and a power switch coupled to the supply line and
controlled by the protection circuitry.
6. The network device according to claim 1 further comprising: the
protection circuit comprising: the integrated diode bridge coupled
between a supply line and a reference line; the integrated
protection circuitry coupled between the supply line and the
reference line; and a p-channel power switch Metal Oxide
Semiconductor Field-Effect Transistor (MOSFET) coupled to the
supply line and controlled by the protection circuitry.
7. The network device according to claim 1 further comprising: the
protection circuit comprising: the integrated diode bridge coupled
between a supply line and a reference line; the integrated
protection circuitry coupled between the supply line and the
reference line; a power switch integrated into the protection
circuit and coupled to the supply line and controlled by the
protection circuitry; and a Powered Device (PD) controller
integrated into the protection circuit and coupled between the
supply line and the reference line.
8. The network device according to claim 1 further comprising: a
power transformer coupled between a supply line and a reference
line; at least one capacitor coupled between the supply line and
the reference line; a switch coupled to the reference line; and the
protection circuit comprising: the integrated diode bridge coupled
between the supply line and the reference line; the integrated
protection circuitry coupled between the supply line and the
reference line; a power switch integrated into the protection
circuit and coupled to the supply line and controlled by the
protection circuitry; and a pulse width modulator integrated into
the protection circuit, coupled between the supply line and the
reference line, and configured to control the switch.
9. The network device according to claim 1 further comprising: a
wall jack power source; an Alternating Current (AC) charger coupled
to the wall jack power source and coupled between a supply line and
a reference line; at least one capacitor coupled between the supply
line and the reference line; a switch coupled to the reference
line; and the protection circuit comprising: the integrated diode
bridge coupled between the supply line and the reference line; the
integrated protection circuitry coupled between the supply line and
the reference line; and a power switch integrated into the
protection circuit and coupled to the supply line and controlled by
the protection circuitry.
10. A network device comprising: an integrated circuit configured
for coupling to lines between a network connector and an Ethernet
physical layer (PHY) and comprising a diode bridge and protection
circuitry integrated onto a common integrated circuit whereby
parasitics in an energy discharge path and stress on the PHY and
the diode bridge are reduced.
11. The network device according to claim 10 further comprising: at
least one capacitor coupled between a supply line and a reference
line; and the integrated circuit comprising: the integrated diode
bridge coupled between the supply line and the reference line; a
p-channel power switch Metal Oxide Semiconductor Field-Effect
Transistor (MOSFET) coupled to the supply line; and the integrated
protection circuitry coupled between the supply line and the
reference line, and having a rail clamp control line coupled to the
p-channel power switch MOSFET that turns on the p-channel power
switch MOSFET hard in a surge condition whereby charge is
redirected to a capacitor of the at least one capacitor.
12. The network device according to claim 10 further comprising: at
least one capacitor coupled between a supply line and a reference
line; and the integrated circuit comprising: the integrated diode
bridge coupled between the supply line and the reference line; a
p-channel power switch Metal Oxide Semiconductor Field-Effect
Transistor (MOSFET) coupled to the supply line; and the integrated
protection circuitry coupled between the supply line and the
reference line, the integrated circuit configured whereby a high
frequency strike short-circuits a capacitor of the at least one
capacitor and passes to ground.
13. The network device according to claim 10 further comprising: a
power transformer coupled between a supply line and a reference
line; a wall jack power source; an Alternating Current (AC) charger
coupled to the wall jack power source and coupled between a supply
line and a reference line; at least one capacitor coupled between
the supply line and the reference line; a switch coupled to the
reference line; and the integrated circuit comprising: the
integrated diode bridge coupled between the supply line and the
reference line; the integrated protection circuitry coupled between
the supply line and the reference line; a power switch integrated
into the integrated circuit and coupled to the supply line and
controlled by the protection circuitry; and a pulse width modulator
integrated into the integrated circuit, coupled between the supply
line and the reference line, and configured to control the
switch.
14. A network device comprising: an over-voltage protection
integrated circuit configured for usage in a Power-over-Ethernet
(PoE) application coupling to lines between a network connector and
an Ethernet physical layer (PHY) comprising: a diode bridge
integrated into the over-voltage protection integrated circuit
coupled between a supply line and a reference line; a integrated
protection circuitry integrated into the over-voltage protection
integrated circuit coupled between the supply line and the
reference line; and a power switch integrated into the over-voltage
protection integrated circuit coupled to the supply line and
controlled by the protection circuitry.
15. The network device according to claim 14 wherein: the power
switch is a p-channel power switch Metal Oxide Semiconductor
Field-Effect Transistor (MOSFET).
16. The network device according to claim 14 further comprising:
the over-voltage protection integrated circuit further comprising:
a Powered Device (PD) controller integrated into the over-voltage
protection circuit and coupled between the supply line and the
reference line.
17. The network device according to claim 14 further comprising:
the diode bridge coupled to center taps of an Ethernet transformer
coupled to the lines between the network connector and the Ethernet
physical layer (PHY).
18. The network device according to claim 14 further comprising:
the diode bridge coupled to a T-Less Connect.TM. solid-state
transformer coupled to the lines between the network connector and
the Ethernet physical layer (PHY).
19. A method for over-voltage protection in a network device
comprising: integrating a diode bridge and protection circuitry
into a common integrated circuit; forming a supply line and a
reference line in the integrated circuit; coupling the diode bridge
and the protection circuitry between the supply line and the
reference line; integrating a power switch into the common
integrated circuit; coupling the power switch to the supply line;
and controlling the power switch via the protection circuitry.
20. The method according to claim 19 further comprising: coupling
the common integrated circuit to lines between a network connector
and an Ethernet physical layer (PHY); and reducing parasitics in an
energy discharge path; reducing stress on the Ethernet physical
layer (PHY) and the diode bridge.
21. The method according to claim 19 further comprising: protecting
against over-voltage in a Power-over-Ethernet (PoE) configuration.
Description
BACKGROUND
[0001] Many networks such as local and wide area networks (LAN/WAN)
structures are used to carry and distribute data communication
signals between devices. Various network elements include hubs,
switches, routers, and bridges, peripheral devices, such as, but
not limited to, printers, data servers, desktop personal computers
(PCs), portable PCs and personal data assistants (PDAs) equipped
with network interface cards. Devices that connect to the network
structure use power to enable operation. Power of the devices may
be supplied by either an internal or an external power supply such
as batteries or an AC power via a connection to an electrical
outlet.
[0002] Some network solutions can distribute power over the network
in combination with data communications. Power distribution over a
network consolidates power and data communications over a single
network connection to reduce installation costs, ensures power to
network elements in the event of a traditional power failure, and
enables reduction in the number of power cables, AC to DC adapters,
and/or AC power supplies which may create fire and physical
hazards. Additionally, power distributed over a network such as an
Ethernet network may function as an uninterruptible power supply
(UPS) to components or devices that normally would be powered using
a dedicated UPS.
[0003] Additionally, network appliances, for example
voice-over-Internet-Protocol (VOIP) telephones and other devices,
are increasingly deployed and consume power. When compared to
traditional counterparts, network appliances use an additional
power feed. One drawback of VOIP telephony is that in the event of
a power failure the ability to contact emergency services via an
independently powered telephone is removed. The ability to
distribute power to network appliances or circuits enable network
appliances such as a VOIP telephone to operate in a fashion similar
to ordinary analog telephone networks currently in use.
[0004] Distribution of power over Ethernet (PoE) network
connections is in part governed by the Institute of Electrical and
Electronics Engineers (IEEE) Standard 802.3 and other relevant
standards, standards that are incorporated herein by reference.
However, power distribution schemes within a network environment
typically employ cumbersome, real estate intensive, magnetic
transformers. Additionally, power-over-Ethernet (PoE)
specifications under the IEEE 802.3 standard are stringent and
often limit allowable power.
[0005] Silicon-based electronic devices are susceptible to damage
from spurious events that exert voltage/current stresses exceeding
the normal operating limits of the devices.
[0006] Stress events can be surges on the power line originating
from causes such as lightning strikes, but can also originate from
human body discharge. If the stress event lasts sufficiently long
or the spike in voltage is sufficiently severe, momentary current
along a temporary path through the substrate can cause failure
through overheating, which causes the silicon or metal to reach the
melting point. Lighting and electro-static discharge (ESD) events
can be very fast, with time constants as short as 6 ns. The maximum
voltage overstress during an event is typically determined by the
reaction time of protection devices so that small parasitic changes
can cause large variations in the magnitude of overstress.
[0007] In Power-over-Ethernet (PoE) applications a powered device
(PD) physical interface (PHY) is particularly vulnerable. Although
the PHY will unavoidably absorb part of the resulting surge, the
function of the protection circuitry is to make the absorbed energy
as small as possible by diverting most of the energy through the
protection circuitry. Typical designs are intended to ensure that
the energy dissipated in the PHY is lower than the energy of a
strike as defined by International Electrotechnical Commission
(IEC) standard 61000-4-2.
[0008] In some cases power is not available through the Ethernet
line, so the PD is powered locally, for example through an AC
adapter. Local powering of the PD presents substantial risk because
the path to earth ground is more direct than when the device is
powered through the Ethernet line, allowing a higher current and
therefore a higher thermal energy level to dissipate.
[0009] To avoid damage, the protective circuitry must respond to a
strike within a limited time frame, forming a relatively large
current path through the protective circuits and dissipating a
significant amount of thermal energy without being destroyed during
the surge. High current has to be discharged through a low
impedance path, thereby avoiding development of voltages that
exceed component specifications. In addition, the protective
circuitry must reset sufficiently quickly to respond to subsequent
strikes as soon as the strikes are likely to occur.
SUMMARY
[0010] According to an embodiment of a network device, an
integrated circuit configured for coupling to lines between a
network connector and an Ethernet physical layer (PHY) comprises a
diode bridge and protection circuitry integrated onto a common
integrated circuit whereby parasitics in an energy discharge path
and stress on the PHY and the diode bridge are reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Embodiments of the invention relating to both structure and
method of operation may best be understood by referring to the
following description and accompanying drawings:
[0012] FIGS. 1A and 1B are schematic block diagrams that
respectively illustrate a high level example embodiments of client
devices in which power is supplied separately to network attached
client devices, and a switch that is a power supply equipment
(PSE)-capable power-over Ethernet (PoE) enabled LAN switch that
supplies both data and power signals to the client devices;
[0013] FIG. 2 is a functional block diagram illustrating a network
interface including a network powered device (PD) interface and a
network power supply equipment (PSE) interface, each implementing a
non-magnetic transformer and choke circuitry;
[0014] FIG. 3A is a schematic block diagram that shows an
embodiment of a network device comprising an integrated
rectification and protection system;
[0015] FIG. 3B is a schematic block diagram illustrating an
embodiment of a network device with an integrated rectification and
protection system adapted for usage with a T-Less Connect.TM.
solid-state transformer;
[0016] FIGS. 4A and 4B are schematic flow charts depict embodiments
of a method for rectification and surge protection in a
Power-over-Ethernet application;
[0017] FIG. 5 is a schematic block and circuit diagram illustrating
a non-integrated rectification and protection circuit;
[0018] FIGS. 6A, 6B, and 6C are graphs showing over-voltage
protection performance for a non-integrated protection circuit
embodiment; and
[0019] FIGS. 7A, 7B, and 7C are graphs showing over-voltage
protection performance for an integrated protection circuit
embodiment comprising an integrated diode bridge and protection
circuitry.
DETAILED DESCRIPTION
[0020] One aspect of performance in a Power-over-Ethernet (PoE)
system is immunity to over-voltage and surge events. The events can
be caused by inductive coupling of external lightning events or
simply by static electricity buildup on Ethernet cabling. The
discharge of energy into sub-micron semiconductor devices can
easily become destructive. Typically, expensive and ruggedized
external components such as sidactors can be added to shield
silicon-based devices from the stresses of external surge events.
The external components typically have high capacitance and tend to
degrade overall system performance in high speed communication
links.
[0021] Integrating the diodes and protection circuitry enables a
much faster response to a surge event, and hence permits the use of
smaller, cheaper, lower voltage components.
[0022] Referring to FIG. 3A, a schematic circuit and block diagram
illustrates an embodiment of a network device 300 comprising an
integrated rectification and protection system 302. The network
device 300 comprises a protection circuit 304 configured for
coupling to lines 306 between a network connector 308 and an
Ethernet physical layer (PHY) 310. The protection circuit 304
comprises a diode bridge 312 and protection circuitry 314
integrated onto a common integrated circuit 316. The word "common"
is defined herein as referring to commonality of integration of the
diode bridge 312 and the protection circuitry 314 on a single
integrated circuit chip 316, and specifically is not used to
indicate typical or conventional usage or functionality of the
integrated circuit or for any other definition.
[0023] The protection circuit 304 can be configured for coupling
lines 306 between the network connector 308 and the Ethernet PHY
310 that carry signal and power in a Power-over-Ethernet
arrangement.
[0024] In the illustrative configuration, the protection circuit
diode bridge 312 is coupled to center taps 318 of an Ethernet
transformer 320 coupled to the lines 306 between the network
connector 308 and the Ethernet PHY 310.
[0025] In the illustrative embodiment, the protection circuit 304
can comprise the integrated diode bridge 312 coupled between a
supply line 322 and a reference line 324. The integrated protection
circuitry 314 is also coupled between the supply line 322 and the
reference line 324. A power switch 326 is coupled to the supply
line 322 and controlled by the protection circuitry 314.
[0026] In the illustrative embodiment, the power switch 326 is
depicted as a p-channel power switch Metal Oxide Semiconductor
Field-Effect Transistor (MOSFET) that is coupled to the supply line
322 and controlled by the protection circuitry 314.
[0027] In some embodiments, for example as shown in FIG. 3A, a
Powered Device (PD) controller 328 can be integrated into the
protection circuit 304 and coupled between the supply line 322 and
the reference line 324.
[0028] In some embodiments, the network device 300 can operate on
power on the communication line, which is typical in a
Power-over-Ethernet (PoE) arrangement. Accordingly, the network
device 300 can further comprise a power transformer 330 coupled
between the supply line 322 and the reference line 324. One or more
capacitors 332 can also be coupled between the supply line 322 and
the reference line 324. A switch 334 can be coupled to the
reference line 324. For the network device 300 powered by the line,
the protection circuit 304 further comprises the integrated diode
bridge 312 and the integrated protection circuitry 314 coupled
between a supply line 322 and a reference line 324. A power switch
326 is coupled to the supply line 322 and controlled by the
protection circuitry 314. A pulse width modulator 336 integrated
into the protection circuit 304, coupled between the supply line
322 and the reference line 324, and configured to control the
switch 334.
[0029] In some embodiments, the network device 300 can operate on
power from a wall socket either as a sole power source or in
combination with power obtained from the lines. For the network
device 300 powered from the wall socket, the protection circuit 304
further comprises a wall jack power source 338 and an Alternating
Current (AC) charger 340 coupled to the wall jack power source 338
and coupled between the supply line 322 and the reference line 324.
One or more capacitors 342 can also be coupled between the supply
line 322 and the reference line 324. A switch 334 can be coupled to
the reference line 324. For the network device 300 powered by the
wall socket, the protection circuit 304 further comprises the
integrated diode bridge 312 and the integrated protection circuitry
314 coupled between a supply line 322 and a reference line 324. A
power switch 326 is coupled to the supply line 322 and controlled
by the protection circuitry 314.
[0030] Referring to FIG. 3B, a schematic circuit and block diagram
shows an embodiment of a network device 350 with an integrated
rectification and protection system 352 adapted for usage with a
T-Less Connect.TM. solid-state transformer 354. The network device
350 comprises a protection circuit diode bridge 312 coupled to a
T-Less Connect.TM. solid-state transformer 354 coupled to the lines
306 between the network connector 308 and the Ethernet PHY 310. The
T-Less Connect.TM. solid-state transformer 354 functions as a
non-magnetic transformer and choke circuit that separates Ethernet
signals from power signals, for example by floating ground
potential of the Ethernet PHY relative to earth ground.
[0031] Referring again to FIG. 3A, in accordance with another
embodiment of a network device 300, an integrated circuit 316
configured for coupling to lines 306 between a network connector
308 and an Ethernet physical layer (PHY) 310 comprising a diode
bridge 312 and protection circuitry 314 integrated onto a common
integrated circuit 316 whereby parasitics in an energy discharge
path and stress on the PHY 310 and the diode bridge 312 are
reduced.
[0032] The network device 300 can further comprise one or more
capacitors 342 coupled between the supply line 322 and the
reference line 324. The integrated circuit 316 comprises the
integrated diode bridge 312 coupled between the supply line 322 and
the reference line 324, a p-channel power switch Metal Oxide
Semiconductor Field-Effect Transistor (MOSFET) 326 coupled to the
supply line 322, and the integrated protection circuitry 314
coupled between the supply line 322 and the reference line 324. The
integrated protection circuitry 314 has a rail clamp control line
344 coupled to the p-channel power switch MOSFET 326 that turns on
the p-channel power switch MOSFET 326 hard in a surge condition
whereby charge is redirected to a capacitor of the one or more
capacitors 342.
[0033] The protection integrated circuit 316 further includes a
driver 346 with an output terminal coupled to the rail clamp
control line 344 that drives the gate of the power switch 326. A
voltage surge that passes through the diode stack builds a voltage,
the driver 346 controls the power switch 326 so that the protection
circuitry 314 takes the extra energy and drives the diode bridge
312 harder to reduce the resistance for a short period of time on
the power switch 326. For an illustrative example, the power switch
may be a 60V or 80V device whereby the voltage between the drain
and source is 60V or 80V. The power switch 326 turns on with a
voltage of 3-5 volts applied to the gate. In response to an
over-voltage surge, the driver 346 can drive the power switch 326
with a voltage applied to the gate of 8-10 volts, turning the power
switch 326 on very hard and reducing the on-resistance of the power
switch 326, thereby pushing the current through the capacitor 342.
In the illustrative embodiment, the power switch 326 is positioned
on the positive or source side of the power lines, contrary to more
usual positioning of power switches on the ground or negative path.
Placement of the power switch 326 on the positive or source path
presents a relative size cost since p-channel devices tend to be
about 60% slower than n-channel devices. Therefore, in the
illustrative embodiment the power switch 326 can be relatively
large, for example on the order of twice as large as switches used
for similar purposes.
[0034] Positioning of the power switch 326 in the positive pathway
enables the network device 300 to be grounded at a common earth
ground, which can improve performance since an over-voltage surge
strikes to ground. Referring to FIG. 3A, the modeled strike path
includes a 330.OMEGA. resistor that is the strike resistance and a
150 pF capacitor connected to earth ground. The protection
integrated circuit 316 couples to the taps of Ethernet transformer
320, connected to the RJ45 connector 308 where the strike
passes.
[0035] In some embodiments, the network device 300 can comprise one
or more capacitors 342 coupled between the supply line 322 and the
reference line 324. The integrated circuit 316 comprises the
integrated diode bridge 312 and the integrated protection circuitry
314 coupled between the supply line 322 and the reference line 324.
A p-channel power switch MOSFET 326 coupled to the supply line. The
integrated circuit 316 is configured whereby a high frequency
strike short-circuits a capacitor of the capacitor or capacitors
342 and passes to ground.
[0036] A current resulting from a surge condition passes through a
diode in the integrated diode bridge 312, causing the diode to
ring. The current passes out to the tip and through to the power
switch 326 to the capacitor 342, for example an 80 nF or 100 nF
capacitor. High frequency oscillations applied to the capacitor 342
short-circuit the integrated circuit 304 and drive the high voltage
to ground. Accordingly, a high frequency strike is canceled through
the capacitor 342 not though any electromagnetic or MOS-based
devices, which would be too slow to turn on to address the surge.
In comparison to an active device, the capacitor 342 is always
active with functionality simply dependent on frequency of applied
signals. For example, at DC, the capacitor 342 forms a completely
open circuit. At highest frequencies, the capacitor 342 is
short-circuited.
[0037] In some embodiments, the network device 300 can operate on
power either from an Ethernet line or a wall socket. Accordingly,
the network device 300 can comprise both a power transformer 330
and a wall jack power source 338 coupled between the supply line
322 and the reference line 324. An AC charger 340 can be coupled to
the wall jack power source 338 and coupled between the supply line
322 and the reference line 324. One or more capacitors 342 can also
be coupled between the supply line 322 and the reference line 324.
A switch 334 can be coupled to the reference line 324. For the
network device 300 powered by either the Ethernet line or the wall
socket, the integrated circuit 316 further comprises the integrated
diode bridge 312 and the integrated protection circuitry 314
coupled between a supply line 322 and a reference line 324. A power
switch 326 is integrated into the integrated circuit 316 and
coupled to the supply line 322. The power switch 326 is controlled
by the protection circuitry 314. A pulse width modulator 336 can be
integrated into the integrated circuit 316 and coupled between the
supply line 322 and the reference line 324. The pulse width
modulator 33 configured to control the switch 334.
[0038] Thus, the network device 300, as a Power-over-Ethernet (PoE)
device, can operate on power received from the communication lines
or from a wall socket. If power is received from the lines, then
the entire network device 300 is floating so when hit with a hard
ESD discharge or lightning strike the housing holding the device
300 jumps in voltage but has no connection to ground other than a
very high impedance path from insulation of the housing to ground.
In contrast, when the network device 300 is connected to a wall
jack 338, a reference voltage powers the device 300 from a typical
AC charger, such as can be used to power a laptop computer. The AC
charger has an internal transformer that transforms 110 volts down
to 12, 24, or 48 volts and rectifies the voltage. The AC charger
also connects a capacitor, for example a 3 nF capacitor, between
the output terminal of the charger to ground.
[0039] For the network device 300 inside the housing with the AC
charger connected to the housing, upon occurrence of a lightning
strike a surge passes through a capacitor, for example 300 pF, and
a resistor, such as 330.OMEGA., and the capacitor is connected to
earth ground. The moment the power switch 326 is turned on to
discharge the capacitor, the switch 326 drives the surge through an
earth ground capacitor, depicted as 3 nF, which is technically a
hard short circuit since the capacitor is very large at 3 nF. Thus,
the power switch 326 enables formation of a hard short-circuit to
ground without any intervening devices.
[0040] When the external AC power adapter is coupled to the device
300, power can also be obtained from another source, such as the
communication line. Therefore, a diode 348 is coupled in series
with the positive path so that the supply cannot be reversed.
Positioning of the n-channel MOSFET power switch 326 and the diode
348 on the positive pathway is contrary to more common switch
arrangements which place a switch and diode on the ground pathway.
In the event of a lightning strike, the discharge passes through
the p-channel power switch 326 and the capacitor 342, then through
the ground pathway, through the large 3 nF capacitor 342 and to
ground.
[0041] Referring again to FIG. 3A, an embodiment of a network
device 300 comprises an over-voltage protection integrated circuit
316 that is configured for usage in a Power-over-Ethernet (PoE)
application coupling to lines 306 between a network connector 308
and an Ethernet physical layer (PHY) 310. The over-voltage
protection integrated circuit 316 comprises a diode bridge 312 and
an integrated protection circuitry 314, both integrated into the
over-voltage protection integrated circuit 316 and coupled between
the supply line 322 and the reference line 324. A power switch 326
is integrated into the over-voltage protection integrated circuit
316 coupled to the supply line 322 and is controlled by the
protection circuitry 314. In some embodiments, the power switch 326
can be a p-channel power switch MOSFET.
[0042] In some embodiments, the over-voltage protection integrated
circuit 316 can further comprise a Powered Device (PD) controller
328 integrated into the over-voltage protection circuit 316 and
coupled between the supply line 322 and the reference line 324.
[0043] In the illustrative embodiment, the diode bridge 312 coupled
to center taps 318 of an Ethernet transformer 320 coupled to the
lines between the network connector 308 and the Ethernet PHY
310.
[0044] In some embodiments, for example as depicted in FIG. 3B, the
diode bridge 312 can be coupled to a T-Less Connect.TM. solid-state
transformer coupled to the lines 306 between the network connector
308 and the Ethernet PHY 354.
[0045] Referring to FIGS. 4A and 4B, several schematic flow charts
depict embodiments of a method 400 for rectification and surge
protection in a Power-over-Ethernet application. As shown in FIG.
4A, the method 400 for over-voltage protection in a network device
comprises integrating 402 a diode bridge and protection circuitry
into a single or common integrated circuit. A supply line and a
reference line are formed 404 in the integrated circuit. The diode
bridge and the protection circuitry are coupled 406 between the
supply line and the reference line. A power switch is integrated
408 into the common integrated circuit and coupled 410 to the
supply line. The power switch is controlled 412 via the protection
circuitry.
[0046] Referring to FIG. 4B, a method 420 may further comprise
actions of coupling 422 the single or common integrated circuit to
lines between a network connector and an Ethernet PHY whereby
parasitics are reduced 424 in an energy discharge path, reducing
426 stresses on the Ethernet PHY and the diode bridge.
[0047] In a typical embodiment, the method can be used to protect
against over-voltage in a Power-over-Ethernet (PoE)
configuration.
[0048] Referring to FIG. 5, a schematic block and circuit diagram
illustrates a non-integrated rectification and protection circuit
500. The typical circuit 500 has a discrete breakdown device 514
outside a PD control circuit 528 to clamp the surge voltage and
form a large current path for the surge to ground. The discrete
breakdown device 514 can be a typical standalone protection
circuit. The surge path is around the PD Controller 528, having the
disadvantage that key protective components are dependant on board
parasitic and layouts which can vary, making consistent performance
difficult. In contrast, the network devices 300 and 350 have the
diode bridge 312 and protection circuitry 314 integrated along with
the PD controller 328 and power switch 326, all of which play a
critical role in determining how the high current due to a surge
event is discharged.
[0049] Lighting strike and large voltage surges are generally
modeled as a capacitor charged to a high voltage and then
discharged through a resistor. The values of the capacitor (C) and
resistor (R) determine the type of energy burst that will occur on
the device under test (DUT). If the RC time is small, the currents
are generally high and last for a short time frame. If the If the
RC time is larger, the currents are generally lower, but last for a
longer time frame.
[0050] In an illustrative example such as the case of contact
discharge, a 150 pf capacitor can be charged to 8000V relative to
earth ground and is connected to one of the RJ45 pins via a 330 ohm
resistor. Peak discharge currents can be as large as 25 A. In a
positive strike on RJ1, Diode 2 (D2) will forward bias and
discharge into the clamping circuit through the return path into
earth ground. Any parasitic resistance due to the bond wire, skin
effect, or board traces significantly increase the voltage spike
across the terminals of the protection circuitry. The parasitic
resistances Rp1-4 on the contact and board trace, board trace
inductances Lp1-2 and the packaged diode bond inductances are
modeled in FIG. 5. A wave front time constant of the surge event is
typically 6 ns, so that small changes in device reaction time can
cause large changes in voltage events.
[0051] Referring again to FIG. 5, the protection circuitry 514 and
PD controller 528 are typically implemented in ruggedized high
voltage circuitry and are less susceptible to over-voltage than the
Ethernet PHY 510, which is typically implemented in sensitive,
sub-micron process. Hence, the protection circuitry 514 is
constructed to absorb most of the charge while developing a small
voltage across the PHY terminals and ensuring that the bridge
diodes are not subjected to large voltage excursions that exceed
specified ratings. Since Power-over-Ethernet operates from a
typical 48V supply, voltage excursions are added to the 48V supply,
making challenging to remain below the diode reverse bias voltage
rating.
[0052] As shown in the voltage waveforms depicted in FIG. 6C, after
the switch is closed discharging the 8 kV charge into the circuit,
a severe ringing in the voltage results across the external bridge
diodes than can reach voltages in excess of 120V. Parasitic
resistance and inductances largely contribute to the ringing. If
board parasitics are higher, a likely possibility since the
selected model shown is somewhat optimistic, voltages on the
external diodes can rise even higher than 120V. With 25 A surging
through the board at high frequencies, for example in a 1
nanosecond wave front, and the combined influence of skin effects,
an additional 1.OMEGA. resistance can add 25V to the diode
voltage.
[0053] Referring to FIG. 6A, a graph depicts Voltage Stress
waveforms resulting for over-voltage on the discrete circuit shown
in FIG. 5. The PHY voltage is approximately 11.5V with some
ringing. The internal supplies VDD48 rise up from 48V nominal value
to about 54V, voltage at which most external sidactors/surge
suppressors are not turned on since the turn-on voltage is
approximately 70V. Accordingly, the sidactors/surge suppressors do
not supply any protection.
[0054] A sidactor becomes operational to protect a circuit at a
particular voltage, for example 60 to 72 volts but is susceptible
to high frequency strikes in a very fast event lasting about a
nanosecond. For example, contact discharge strike of 15000 volts
can be so fast that sidactor protection fails, whereby the sidactor
does not turn on fast enough and the voltage can shoot high above
the specified level, resulting in passage of up to hundreds of
volts before sidactor activation. In contrast, a sidactor is
effective for protecting against a surge or lightning strike which
is much slower and lasts longer than a contact discharge, for
example lasting 20 to 40 nanoseconds, due to higher energy, for
example imposing a surge in the range of thousands of volts. In
response to a surge such as a lightning strike, the sidactors turn
on and clamp the voltage to a set maximum such as 72 volts, drawing
and dissipating energy from the current path.
[0055] Referring to FIG. 6B, a graph depicts Current Stress
waveforms in an over-voltage condition on the discrete circuit
shown in FIG. 5. In the current waveforms in FIG. 6B, the contact
discharge current of approximately 25 A is the strike current
surging through the 330.OMEGA. resistor once the switch is closed.
About 12 Amps flows though the external 80 nF capacitor wherein the
total capacitance is 100 nF, with a capacitor C2, for example 20
nF, internal to the PD controller. Approximately 2 Amps flow into
the PHY clamp circuit and the power switch M1 which is presumed to
be enabled takes 5 Amps.
[0056] FIG. 6C, a graph shows Voltage Stress waveforms in an
over-voltage condition on the discrete circuit depicted in FIG. 5
including positive and negative strikes. Waveforms indicate
positive and negative strikes that place a large stress on the
external bridge diodes. Negative strikes are shunted to the ground
return path through the diode path D5.
[0057] Referring again to FIGS. 3A and 3B in combination with
graphs in FIGS. 7A, 7B, and 7C, over-voltage protection performance
is shown for the integrated diode bridge 312 and protection
circuitry 314 system for comparison to the non-integrated system
depicted in FIG. 5 and associated graphs in FIGS. 6A through 6C. As
shown in FIGS. 7A, 7B, and 7C, integrating the diode bridge 312 and
protection circuitry 314 significantly reduces parasitics in the
energy discharge path and reduces stress applied to the PHY 310 and
the diode bride 312. The integrated combination enables a lower
impedance path for the surge current, thus reducing the voltage
build-up with high currents. A 62V rail clamp can also be used turn
on the P-Channel Power Switch MOSFET 326 hard thus adding an
alternate path for the charge to go through the 4.7 uF capacitor, a
path that is more useful in lighting strikes, where the time
constants are longer.
[0058] The integrated circuit 316 is configured to constrain the
maximum possible voltage that can be imposed across the diodes,
enabling usage of reasonably-sized diodes while avoiding damage or
destruction under conditions of a large voltage surge. Integration
of the diode bridge 312 and the protection circuitry 314
substantially eliminates circuit board and bonding package
parasitics of the diodes and other components in a non-integrated
implementation that is susceptible to very fast transients and
contact discharge into a voltage pulse that can cause high
frequency ringing at voltages as large as 120 or 150 volts or more,
or even 180 to 200 volts for implementations with too close spacing
of components.
[0059] Integration of the diode bridge 312 and the protection
circuitry 314 also can substantially eliminate parasitic
oscillations that result from dynamic current changes on circuit
traces in a non-integrated implementation and the voltage which
rapidly can arise on the traces. The voltage resulting from
resistance on the traces can add substantially to the voltage on
the line, for example increasing voltage by up to half or more of
the line signal, not including ringing or overshoots that can occur
due to the inductive nature of the circuit.
[0060] FIG. 7A is a graph illustrating Voltage Stress waveforms in
an over-voltage condition during operation of the protection
circuit 304 including the integrated diode bridge 312 and
protection circuitry 314. The integrated design reduces the
over-voltage strike stress across input terminals to the diodes by
as much as 50%, to about 55V.
[0061] FIG. 7B is a graph illustrating Current Stress waveforms in
an over-voltage condition during operation of the protection
circuit 304 including the integrated diode bridge 312 and
protection circuitry 314. As shown in the current waveforms in FIG.
7B, about 13 Amps of the strike current flows though the external
capacitor C1, for example an 80 nF capacitor. In the illustrative
configuration, the total capacitance is 100 nf with 20 nF internal
to the PD controller 328. Approximately 2 Amps flow into the PHY
clamp circuit and the power switch M1 takes 5.5 Amps, improving
reliability of the PHY 310 under ESD and surge stress events.
[0062] FIG. 7C is a graph illustrating Voltage Stress waveforms in
an over-voltage condition for positive and negative strikes during
operation of the protection circuit 304 including the integrated
diode bridge 312 and protection circuitry 314.
[0063] In summary, comparing the waveforms in FIGS. 7A through 7C
for the integrated protection circuit 304 to waveforms in FIGS. 6A
through 6C for a non-integrated system, integrating the diode
bridge 312 and protection circuitry 314 significantly increases the
reaction time of protection devices and increases PHY immunity to
over-voltage stress events. Integrating the components also
substantially reduces board-to-board variation and increases
overall manufacturability.
[0064] As shown in the examples depicted by the graphs, the
integrated diode configuration has lower peak diode voltages, for
example 57V as compared to 120V. The integrated diode arrangement
has lower peak electrostatic discharge (ESD) clamp voltages, shown
as 10V in comparison to 11.5V. The integrated diode system has
lower ESD clamp currents of 1.8 A compared to 2.6 A. The integrated
diode configuration more effectively uses the switch to control
excursions, an Iswitch of 5.22 A in comparison to 4.03 A.
[0065] The protection circuit 304 with integration of the diode
bridge 312 and the protection circuitry 314 is configured whereby
high frequency ringing is reduced or eliminated.
[0066] Diodes in the diode bridge 512 in the non-integrated
implementation propagate high frequency ringing as the
non-integrated diodes set up a current through the diodes that
tends to be capacitive in behavior. A very high frequency pulse
passing through the diode tends to have an inductive behavior,
creating even more ringing on the diode. Thus in addition to
external parasitic oscillations, inductance also aggravates the
ringing. The diodes become inductive and, when inductive, create an
even higher ringing. The integrated protection circuit 304 avoids
the high frequency ringing of non-integrated diodes which are
highly sensitive to surges.
[0067] Performance shown in the illustrative examples is expected
to be improved even further by implementation of switch gate
controls from the Rail clamp.
[0068] The illustrative network device 300, the diode bridge 312
and protection circuitry 314 are integrated into the protection
circuit 304 at least partly in recognition that for high frequency
events, the sidactor used in non-integrated designs does not turn
on with sufficient quickness to address various types of
over-voltage. The integrated protection circuit 304 is formed to
pass current through the circuit as quickly as possible. One aspect
of integrated circuit operation is that a high frequency
oscillation resulting from an over-voltage condition is canceled by
passing through a capacitor. Another aspect of integrated circuit
operation is usage of a power switch 326 on the positive or supply
side of the integrated circuit 316 that is a relatively large
active device.
[0069] The IEEE 802.3 Ethernet Standard, which is incorporated
herein by reference, addresses loop powering of remote Ethernet
devices (802.3af). Power over Ethernet (PoE) standard and other
similar standards support standardization of power delivery over
Ethernet network cables to power remote client devices through the
network connection. The side of link that supplies power is called
Powered Supply Equipment (PSE). The side of link that receives
power is the Powered device (PD). Other implementations may supply
power to network attached devices over alternative networks such
as, for example, Home Phoneline Networking alliance (HomePNA) local
area networks and other similar networks. HomePNA uses existing
telephone wires to share a single network connection within a home
or building. In other examples, devices may support communication
of network data signals over power lines.
[0070] In various configurations described herein, a magnetic
transformer of conventional systems may be eliminated while
transformer functionality is maintained. Techniques enabling
replacement of the transformer may be implemented in the form of
integrated circuits (ICs) or discrete components.
[0071] FIG. 1A is a schematic block diagram that illustrates a high
level example embodiment of devices in which power is supplied
separately to network attached client devices 112 through 116 that
may benefit from receiving power and data via the network
connection. The devices are serviced by a local area network (LAN)
switch 110 for data. Individual client devices 112 through 116 have
separate power connections 118 to electrical outlets 120. FIG. 1B
is a schematic block diagram that depicts a high level example
embodiment of devices wherein a switch 110 is a power supply
equipment (PSE)-capable power-over Ethernet (PoE) enabled LAN
switch that supplies both data and power signals to client devices
112 through 116. Network attached devices may include a Voice Over
Internet Protocol (VOIP) telephone 112, access points, routers,
gateways 114 and/or security cameras 116, as well as other known
network appliances. Network supplied power enables client devices
112 through 116 to eliminate power connections 118 to electrical
outlets 120 as shown in FIG. 1A. Eliminating the second connection
enables the network attached device to have greater reliability
when attached to the network with reduced cost and facilitated
deployment.
[0072] Although the description herein may focus and describe a
system and method for coupling high bandwidth data signals and
power distribution between the integrated circuit and cable that
uses transformer-less ICs with particular detail to the IEEE
802.3af Ethernet standard, the concepts may be applied in
non-Ethernet applications and non-IEEE 802.3af applications. Also,
the concepts may be applied in subsequent standards that supersede
or complement the IEEE 802.3af standard.
[0073] Various embodiments of the depicted system may support solid
state, and thus non-magnetic, transformer circuits operable to
couple high bandwidth data signals and power signals with new
mixed-signal IC technology, enabling elimination of cumbersome,
real-estate intensive magnetic-based transformers.
[0074] Typical conventional communication systems use transformers
to perform common mode signal blocking, 1500 volt isolation, and AC
coupling of a differential signature as well as residual lightning
or electromagnetic shock protection. The functions are replaced by
a solid state or other similar circuits in accordance with
embodiments of circuits and systems described herein whereby the
circuit may couple directly to the line and provide high
differential impedance and low common mode impedance. High
differential impedance enables separation of the physical layer
(PHY) signal from the power signal. Low common mode impedance
enables elimination of a choke, allowing power to be tapped from
the line. The local ground plane may float to eliminate a
requirement for 1500 volt isolation. Additionally, through a
combination of circuit techniques and lightning protection
circuitry, voltage spike or lightning protection can be supplied to
the network attached device, eliminating another function performed
by transformers in traditional systems or arrangements. The
disclosed technology may be applied anywhere transformers are used
and is not limited to Ethernet applications.
[0075] Specific embodiments of the circuits and systems disclosed
herein may be applied to various powered network attached devices
or Ethernet network appliances. Such appliances include, but are
not limited to VoIP telephones, routers, printers, and other
similar devices.
[0076] Referring to FIG. 2, a functional block diagram depicts an
embodiment of a network device 200 including a T-Less Connect.TM.
solid-state transformer. The illustrative network device comprises
a power potential rectifier 202 adapted to conductively couple a
network connector 232 to an integrated circuit 270, 272 that
rectifies and passes a power signal and data signal received from
the network connector 232. The power potential rectifier 202
regulates a received power and/or data signal to ensure proper
signal polarity is applied to the integrated circuit 270, 272.
[0077] The network device 200 is shown with the power sourcing
switch 270 sourcing power through lines 1 and 2 of the network
connector 232 in combination with lines 3 and 6.
[0078] In some embodiments, the power potential rectifier 202 is
configured to couple directly to lines of the network connector 232
and regulate the power signal whereby the power potential rectifier
202 passes the data signal with substantially no degradation.
[0079] In some configuration embodiments, the network connector 232
receives multiple twisted pair conductors 204, for example twisted
22-26 gauge wire. Any one of a subset of the twisted pair
conductors 204 can forward bias to deliver current and the power
potential rectifier 202 can forward bias a return current path via
a remaining conductor of the subset.
[0080] FIG. 2 illustrates the network interface 200 including a
network powered device (PD) interface and a network power supply
equipment (PSE) interface, each implementing a non-magnetic
transformer and choke circuitry. A powered end station 272 is a
network interface that includes a network connector 232,
non-magnetic transformer and choke power feed circuitry 262, a
network physical layer 236, and a power converter 238.
Functionality of a magnetic transformer is replaced by circuitry
262. In the context of an Ethernet network interface, network
connector 232 may be a RJ45 connector that is operable to receive
multiple twisted wire pairs. Protection and conditioning circuitry
may be located between network connector 232 and non-magnetic
transformer and choke power feed circuitry 262 to attain surge
protection in the form of voltage spike protection, lighting
protection, external shock protection or other similar active
functions. Conditioning circuitry may be a diode bridge or other
rectifying component or device. A bridge or rectifier may couple to
individual conductive lines 1-8 contained within the RJ45
connector. The circuits may be discrete components or an integrated
circuit within non-magnetic transformer and choke power feed
circuitry 262.
[0081] In an Ethernet application, the IEEE 802.3af standard (PoE
standard) enables delivery of power over Ethernet cables to
remotely power devices. The portion of the connection that receives
the power may be referred to as the powered device (PD). The side
of the link that supplies power is called the power sourcing
equipment (PSE).
[0082] In the powered end station 272, conductors 1 through 8 of
the network connector 232 couple to non-magnetic transformer and
choke power feed circuitry 262. Non-magnetic transformer and choke
power feed circuitry 262 may use the power feed circuit and
separate the data signal portion from the power signal portion. The
data signal portion may then be passed to the network physical
layer (PHY) 236 while the power signal passes to power converter
238.
[0083] If the powered end station 272 is used to couple the network
attached device or PD to an Ethernet network, network physical
layer 236 may be operable to implement the 10 Mbps, 100 Mbps,
and/or 1 Gbps physical layer functions as well as other Ethernet
data protocols that may arise. The Ethernet PHY 236 may
additionally couple to an Ethernet media access controller (MAC).
The Ethernet PHY 236 and Ethernet MAC when coupled are operable to
implement the hardware layers of an Ethernet protocol stack. The
architecture may also be applied to other networks. If a power
signal is not received but a traditional, non-power Ethernet signal
is received the nonmagnetic power feed circuitry 262 still passes
the data signal to the network PHY.
[0084] The power signal separated from the network signal within
non-magnetic transformer and choke power feed circuit 262 by the
power feed circuit is supplied to power converter 238. Typically
the power signal received does not exceed 57 volts SELV (Safety
Extra Low Voltage). Typical voltage in an Ethernet application is
48-volt power. Power converter 238 may then further transform the
power as a DC to DC converter to provide 1.8 to 3.3 volts, or other
voltages specified by many Ethernet network attached devices.
[0085] Power-sourcing switch 270 includes a network connector 232,
Ethernet or network physical layer 254, PSE controller 256,
non-magnetic transformer and choke power supply circuitry 266, and
possibly a multiple-port switch. Transformer functionality is
supplied by non-magnetic transformer and choke power supply
circuitry 266. Power-sourcing switch 270 may be used to supply
power to network attached devices. Powered end station 272 and
power sourcing switch 270 may be applied to an Ethernet application
or other network-based applications such as, but not limited to, a
vehicle-based network such as those found in an automobile,
aircraft, mass transit system, or other like vehicle. Examples of
specific vehicle-based networks may include a local interconnect
network (LIN), a controller area network (CAN), or a flex ray
network. All may be applied specifically to automotive networks for
the distribution of power and data within the automobile to various
monitoring circuits or for the distribution and powering of
entertainment devices, such as entertainment systems, video and
audio entertainment systems often found in today's vehicles. Other
networks may include a high speed data network, low speed data
network, time-triggered communication on CAN (TTCAN) network, a
J1939-compliant network, ISO11898-compliant network, an
ISO11519-2-compliant network, as well as other similar networks.
Other embodiments may supply power to network attached devices over
alternative networks such as but not limited to a HomePNA local
area network and other similar networks. HomePNA uses existing
telephone wires to share a single network connection within a home
or building. Alternatively, embodiments may be applied where
network data signals are provided over power lines.
[0086] Non-magnetic transformer and choke power feed circuitry 262
and 266 enable elimination of magnetic transformers with integrated
system solutions that enable an increase in system density by
replacing magnetic transformers with solid state power feed
circuitry in the form of an integrated circuit or discreet
component.
[0087] In some embodiments, non-magnetic transformer and choke
power feed circuitry 262, network physical layer 236, power
distribution management circuitry 254, and power converter 238 may
be integrated into a single integrated circuit rather than discrete
components at the printed circuit board level. Optional protection
and power conditioning circuitry may be used to interface the
integrated circuit to the network connector 232.
[0088] The Ethernet PHY may support the 10/100/1000 Mbps data rate
and other future data networks such as a 10000 Mbps Ethernet
network. Non-magnetic transformer and choke power feed circuitry
262 supplies line power minus the insertion loss directly to power
converter 238, converting power first to a 12V supply then
subsequently to lower supply levels. The circuit may be implemented
in any appropriate process, for example a 0.18 or 0.13 micron
process or any suitable size process.
[0089] Non-magnetic transformer and choke power feed circuitry 262
may implement functions including IEEE 802.3.af signaling and load
compliance, local unregulated supply generation with surge current
protection, and signal transfer between the line and integrated
Ethernet PHY. Since devices are directly connected to the line, the
circuit may be implemented to withstand a secondary lightning
surge.
[0090] For the power over Ethernet (PoE) to be IEEE 802.3af
standard compliant, the PoE may be configured to accept power with
various power feeding schemes and handle power polarity reversal. A
rectifier, such as a diode bridge, a switching network, or other
circuit, may be implemented to ensure power signals having an
appropriate polarity are delivered to nodes of the power feed
circuit. Any one of the conductors 1, 4, 7 or 3 of the network RJ45
connection can forward bias to deliver current and any one of the
return diodes connected can forward bias to form a return current
path via one of the remaining conductors. Conductors 2, 5, 8 and 4
are connected similarly.
[0091] Non-magnetic transformer and choke power feed circuitry 262
applied to PSE may take the form of a single or multiple port
switch to supply power to single or multiple devices attached to
the network. Power sourcing switch 270 may be operable to receive
power and data signals and combine to communicate power signals
which are then distributed via an attached network. If power
sourcing switch 270 is a gateway or router, a high-speed uplink
couples to a network such as an Ethernet network or other network.
The data signal is relayed via network PHY 254 and supplied to
non-magnetic transformer and choke power feed circuitry 266. PSE
switch 270 may be attached to an AC power supply or other internal
or external power supply to supply a power signal to be distributed
to network-attached devices that couple to power sourcing switch
270. Power controller 256 within or coupled to non-magnetic
transformer and choke power feed circuitry 266 may determine, in
accordance with IEEE standard 802.3af, whether a network-attached
device in the case of an Ethernet network-attached device is a
device operable to receive power from power supply equipment. When
determined that an IEEE 802.3af compliant powered device (PD) is
attached to the network, power controller 256 may supply power from
power supply to non-magnetic transformer and choke power feed
circuitry 266, which is sent to the downstream network-attached
device through network connectors, which in the case of the
Ethernet network may be an RJ45 receptacle and cable.
[0092] IEEE 802.3af Standard is to fully comply with existing
non-line powered Ethernet network systems. Accordingly, PSE detects
via a well-defined procedure whether the far end is PoE compliant
and classify sufficient power prior to applying power to the
system. Maximum allowed voltage is 57 volts for compliance with
SELV (Safety Extra Low Voltage) limits.
[0093] For backward compatibility with non-powered systems, applied
DC voltage begins at a very low voltage and only begins to deliver
power after confirmation that a PoE device is present. In the
classification phase, the PSE applies a voltage between 14.5V and
20.5V, measures the current and determines the power class of the
device. In one embodiment the current signature is applied for
voltages above 12.5V and below 23 Volts. Current signature range is
0-44 mA.
[0094] The normal powering mode is switched on when the PSE voltage
crosses 42 Volts where power MOSFETs are enabled and the large
bypass capacitor begins to charge.
[0095] A maintain power signature is applied in the PoE signature
block--a minimum of 10 mA and a maximum of 23.5 kohms may be
applied for the PSE to continue to feed power. The maximum current
allowed is limited by the power class of the device (class 0-3 are
defined). For class 0, 12.95 W is the maximum power dissipation
allowed and 400 ma is the maximum peak current. Once activated, the
PoE will shut down if the applied voltage falls below 30V and
disconnect the power MOSFETs from the line.
[0096] Power feed devices in normal power mode provide a
differential open circuit at the Ethernet signal frequencies and a
differential short at lower frequencies. The common mode circuit
presents the capacitive and power management load at frequencies
determined by the gate control circuit.
[0097] Terms "substantially", "essentially", or "approximately",
that may be used herein, relate to an industry-accepted tolerance
to the corresponding term. Such an industry-accepted tolerance
ranges from less than one percent to twenty percent and corresponds
to, but is not limited to, component values, integrated circuit
process variations, temperature variations, rise and fall times,
and/or thermal noise. The term "coupled", as may be used herein,
includes direct coupling and indirect coupling via another
component, element, circuit, or module where, for indirect
coupling, the intervening component, element, circuit, or module
does not modify the information of a signal but may adjust its
current level, voltage level, and/or power level. Inferred
coupling, for example where one element is coupled to another
element by inference, includes direct and indirect coupling between
two elements in the same manner as "coupled".
[0098] While the present disclosure describes various embodiments,
these embodiments are to be understood as illustrative and do not
limit the claim scope. Many variations, modifications, additions
and improvements of the described embodiments are possible. For
example, those having ordinary skill in the art will readily
implement the steps necessary to provide the structures and methods
disclosed herein, and will understand that the process parameters,
materials, and dimensions are given by way of example only. The
parameters, materials, and dimensions can be varied to achieve the
desired structure as well as modifications, which are within the
scope of the claims. Variations and modifications of the
embodiments disclosed herein may also be made while remaining
within the scope of the following claims. For example, various
aspects or portions of a network interface are described including
several optional implementations for particular portions. Any
suitable combination or permutation of the disclosed designs may be
implemented.
* * * * *