`
`4,056,689 11/1977 Freimanis 4,499,532 2/1985 Hudson et a1. _.
`
`4,661,896 4/1987 Kobayashietal 4,679,132 7/1987 Jirka
`
`4,697,229 9/1987 Davy et a1.
`4,704,670 11/1987 Gradl et a1.
`4,761,812 8/1988 Hollis et a1.
`4,813,066 3/1989 Hohz et a1_
`
`..
`
`Primary Examiner—William H. Beha, Jr.
`Attorney, Agent, or F1'rm-—Sughrue, Mion, Zinn
`Macpeak & Seas
`[57]
`ABSTRACT
`A power feed system for telephone and/or information
`technology terminals (1) is connected to a transmission
`and remote power feed link (4) of the terminal and
`comprises a switch mode power supply unit (7) con
`nected to the wires of the link and a regulator (8) at the
`output of the switch mode power supply unit which
`supplies at least part of the power required by the termi
`nal and which includes a circuit to ensure progressive
`starting of the switch mode power supply unit when the
`terminal is powered up via the link.
`
`4 Claims, 1 Drawing Sheet
`
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`United States Patent 1191
`Jenneve et a1.
`
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`5,144,544
`Sep. 1, 1992
`
`US005144544A
`Patent Number:
`Date of Patent:
`
`[11]
`[45]
`
`
`
`
`
`[54] POWER FEED SYSTEM FOR TELEPHONE AND/0R INFORMATION TECHNQLOGY TERMINALS
`
`[75] Inventors: Dany Jenneve; Gilles Misslin, both of
`Strasbourg, France
`[73] Assignee: Alcatel Business Systems, Paris,
`France
`[21] Appl. No.: 574,726
`[22] Filed:
`Aug. 30, 1990
`Foreign Application Priority Data
`[30]
`or
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`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`3,733,540 5/1973 Hawkins
`3,818,306 6/1974 Marini
`
`.1 323/901
`363/89
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`Sep. 1, 1992
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`1
`
`5,144,544
`
`POWER FEED SYSTEM FOR TELEPHONE
`AND/ OR INFORMATION TECHNOLOGY
`TERMINALS
`
`BACKGROUND OF THE INVENTION
`The invention concerns power feed systems incorpo
`rated in telephone and/or information technology ter
`minals connected to transmission lines which addition
`ally feed them remotely with electrical power, for ex
`ample S interface terminals connected by a passive bus
`to an integrated services digital network.
`The conventional objective of such power feed sys
`tems is to limit to predetermined reasonable values the
`current that is likely to be drawn by a terminal from the
`transmission and power feed link to which it is con
`nected. The addition of a switch mode power supply
`unit to a current limiter power feed system makes it
`possible to achieve greater ?exibility in the use of the
`electrical power received by a terminal. However, a
`state in which the power feed system is disabled may
`arise if the power demand of the switch mode power
`supply unit exceeds what the power feed link can sup
`ply given the presence of the current limiter.
`The existence of terminals ?tted with standard con
`nectors enables simple connection of a telephone and
`/or information technology installation according to
`the immediate and possibly temporary requirements of
`users, for example by simply plugging in at various
`points duly equipped with one or more connectors. It
`also implies that the terminals and in particular their
`power feed systems do not disrupt the operation of the
`remote power source, especially during connection
`operations, which can cause the power feed system to
`short-circuit the power source if the system comprises
`capacitors which are charged directly from the termi
`nals of the remote power source via the transmission
`and power feed link to which the device is being con
`nected.
`_
`It is also necessary to be able to connect a terminal to
`a transmission and power feed link already serving
`other terminals without interrupting their operation and
`any interchange of information that may be in progress.
`Failing perfect simultaneity of the connection of the
`various conductors of a terminal connector when mak
`ing a connection to a multi-wire transmission and active
`power feed link, transient imbalance is likely to disrupt
`transmissions in progress on the link to an unacceptable
`degree.
`
`10
`
`20
`
`25
`
`45
`
`50
`
`SUMMARY OF THE INVENTION
`The present invention therefore proposes a power
`feed system for telephone and/or information technol
`ogy terminals adapted to be connected to a transmission
`link simultaneously supplying it with at least some of its
`required electrical power via a current limiter.
`According to one characteristic of the invention, the
`power feed system comprises a switch mode power
`60
`supply unit of the power converter type adapted to be
`connected to the wires of the link and a regulator which
`is connected to the output of the switch mode power
`supply unit and which includes the current limiter, said
`regulator supplying at least some of the power required
`by the terminal and comprising means for progressively
`starting up the switch mode power supply unit when
`said terminal is powered up via the link.
`
`65
`
`2
`BRIEF DESCRIPTION OF THE DRAWINGS
`The invention, its characteristics and its advantages
`are explained in the following description given with
`reference to the ?gures mentioned below.
`FIG. 1 is a theoretical circuit diagram showing a
`power feed system of a telephone and/or information
`technology terminal using a source in a remote line
`termination unit to which the terminal is connected by
`a transmission link which also provides the power feed.
`FIG. 2 is a schematic of a power feed system in accor
`dance with the invention for a telephone and/or infor
`mation technology terminal adapted to be connected to
`a transmission and power feed link.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`The known system shown in FIG. 1 feeds electrical
`power to one or more telephone and/or information
`technology terminals 1 from a remote source 2 usually
`located in a line termination unit 3 (hereinafter desig
`nated ‘termination’) to which a transmission and power
`feed link 4 from the terminal(s) 1 is connected.
`The terminals considered here are, for example, sub
`scriber terminals of an integrated services digital net
`work (ISDN) which have a standard S interface
`through which they are connected to a bus transmission
`and power feed link 4. Further information on the com
`ponents mentioned above, which will not be explained
`in more detail here, and in particular on the terminals
`and the terminations, can be found in an article entitled
`“Les installations terminales d’abonnés” (“Subscriber
`terminal installations”) published in 1987 in the third
`issue of the French journal “Commutation et transmis
`sion” and in the book “Le RNIS" ("The IDSN”) pub
`lished in Paris in 1987 under the pseudonym G. DI
`CENET as part of the “Collection Technique des
`Télécommuncations”.
`Each terminal 1 includes a telephone and/or informa~
`tion technology device (which is not shown here be
`cause it is not directly related to the invention) and an
`auxiliary device adapted to supply at least part of its
`required electrical power from the link 4 to which the
`terminal is connected. A functional schematic of one
`example of telephone device is shown on page 189 of
`the book mentioned above. It combines an S interface
`management module with a module handling telephone
`and acoustic functions and a user-terminal dialog mod
`ule that will not be described in more detail here.
`The power feed auxiliary device 5 includes a switch
`mode power supply unit 7 of the usual power converter
`type supplied by the link 4 and a regulator 8 on the input
`side of the switch mode power supply unit relative to
`the link 4 and through which the terminal comprising it
`is at least partly fed with power.
`In the example under discussion where the link 4 is of
`the ISDN bus type, the link comprises two pairs of
`wires 9 and 10 for transmitting separately signals in each
`of two transmission directions between the telephone
`and/or information technology device of the terminal
`and the corresponding device (not shown) in the termi
`nation 3. The pair 9 connects two transformers 11, 12
`respectively located in the terminal 1 and in the termi
`nation 3. The pair 10 connects two other transformers
`13, lit-respectively located in the terminal 1 and in the
`termination 3.
`The phantom power feed to the terminal 1 from the
`source 2, which is in this instance located in the termina
`
`

`

`pl 0
`
`25
`
`35
`
`5,144,544
`3
`tion 3, is provided by the two pairs 9 and 10, the source
`2 being connected between center-taps of the windings
`of the transformers 12 and 14 to the end-taps of which
`the two pairs are connected, while the switch mode
`power supply unit 7 is connected to center-taps of the
`windings of the transformers 11 and 13 to the end-taps
`of which the same pairs 9 and 10 are also connected. In
`a known manner (not shown here) the windings of the
`transformers 11 through 14 shown as unconnected
`serve transmit devices (not shown) of the terminal and
`of the termination comprising them.
`The regulator 8 is connected to the link 4 through the
`switch mode power supply unit 7, the latter supplying
`to it the electrical power to be divided between the
`various circuits (not shown here) of the terminal 1. The
`regulator 8 is adapted to act on the switch mode power
`supply unit 7; which provides one or more supply volt
`ages such as VS1 and VS2 for the various circuits of the
`terminal 1.
`The embodiment of the power feed system shown in
`20
`FIG. 2 combines a regulator 8 with a switch mode
`power supply unit 7, as already described. It is con
`nected between the center taps of windings of the trans
`formers l1 and 13 to the end-taps of which the pairs 9
`and 10 are connected, a pair of power feed wires 6
`connecting the switch mode power supply unit 7 to
`these two center-taps.
`The switch mode power supply unit 7 includes a
`switch mode MOS transistor 16 controlled by a device
`15 adapted to vary the width of its control pulses as
`required; this conventional device 15 will not be de
`scribed in detail as it is not directly related to the inven
`tion. In this embodiment it is responsive to signals sup
`plied to it by the regulator 8 via a wire C in a manner to
`be explained later.
`The voltages V8] and VS2 supplied by the switch
`mode power supply unit 7, which are in this instance
`DC voltages, are produced by two recti?er circuits
`with diodes 17, 18 and capacitors 19, 20 each connected
`across one secondary winding of a transformer 21
`whose primary is supplied with power under the con
`trol of the transistor 16.
`The drain of this transistor is connected to a ?rst
`terminal of the primary winding of the transformer 21.
`Its source is connected to a grounding wire M of the
`switch mode power supply unit 7. Its grid is connected
`to a wire G through which the device 15 controls its
`switching between the turned on and turned off states.
`The transistor 16 is protected against overvoltages by
`a Zener diode 22 with its anode and its cathode respec
`tively connected to the source and the drain of the
`transistor.
`The second terminal of the primary winding of the
`transformer 21 is connected to the positive wire V of
`the power supply unit 7 via the regulator 8.
`55
`A radio frequency ?lter comprising an inductor 23
`and two capacitors 24 and 25 is connected across the
`circuit comprising the primary winding of the trans
`former 21 and the transistor 16 in series. The capacitor
`24 is connected across the combination formed by the
`winding a freewheel diode 26 and the transistor 16 in
`series. A freewheel diode 26 is conventionally associ
`ated with this inductor 23.
`An MOS second transistor 27 in the regulator 8 has
`its drain connected to the point common to the capaci
`tor 25 and the inductor 23, at the output of the switch
`mode power supply unit ?lter. It is connected on the
`input side of the inductor to the positive wire V by a
`
`4
`current limiter including a PNP transistor 28 and a
`low-value resistor 29 in series between the source of the
`transistor 27 and the wire V. The resistor 29 is con
`nected between the emitter and the base of the transistor
`28 to serve as its bias resistor, the base and collector of
`this transistor being connected to the grid of the transis
`tor 27.
`A time-delay circuit comprising a capacitor 30 and a
`resistor 31 in series is connected between the source and
`the grid of the transistor 27 in parallel with a high-value
`resistor 32. A resistor 33 is associated with the resistor
`32 to form a divider bridge between the source of the
`transistor 27 and wire M connected to the source of the
`transistor 16, the point common to the resistors 32 and
`33 being connected to the grid of the transistor 27. A
`diode 34 with its anode connected to the wire M is
`connected in parallel with the high-value resistor 33
`between the wire M and the grid of the transistor 27.
`A PNP transistor 35 is connected on the input side of
`a resistor divider bridge 36, 37 to send a control signal
`to the switch mode power supply unit 7 dependent on
`the voltage between the drain and the source of the
`transistor 27. To this end the base of the transistor 35 is
`connected to the drain of the transistor 27 via a resistor
`38, its emitter is connected to the grid of the transistor
`27 and its collector is connected to one end of the resis
`tor divider bridge 36, 37 whose other end is connected
`to the wire M, a capacitor 39 shunting this bridge. The
`control wire C connected to the point common to the
`resistors 36 and 37 transmits the control signal to the
`switch mode power supply unit.
`A diode 40 with its anode connected to the drain of
`the transistor 27 and its cathode connected to the emit
`ter of the transistor 28 completes the circuit.
`The regulator 8 limits the current drawn from the
`remote source 2 when the terminal 1 is powered up and
`if the terminal 1 is short circuited. For a terminal with a
`maximum consumption of l W, for example, the theo
`retical current at 40 V is 25 mA while that at 25 V is 40
`mA. Additionally, it is necessary to allow for the inrush
`current and the energy to be stored on power up. To
`this end the transistor 28 is prevented from turning on
`until the current in the resistor 29 reaches a suf?cient
`value. In one embodiment where the voltage normally
`present on the wire V is 40 V and where the resistor 29
`has a value of approximately 10 ohms the transistor 28
`turns on only when the current in the resistor 29 ex
`ceeds 70 mA.
`In normal operation the transistor 28 is turned off and
`the grid of the transistor 27 is biased by the resistor
`divider bridge 32, 33 to a value such that the transistor
`27 is turned fully on, its source and its drain being virtu
`ally short-circuited; the power feed to the terminal 1 is
`then normally under the control of the switch mode
`power supply unit.
`The inductor 23 protects the MOS transistors against
`excessively sudden variations in current and the diode
`26 is a freewheel diode, as already mentioned.
`If excessive current is drawn, in this instance more
`than 70 mA., the transistor 28 turns on, the grid and the
`source of the transistor 27 are at the same potential and
`the transistor 27 turns off, so that power is no longer fed
`to the primary winding of the transformer 21.
`The transistor 35 operates in its linear range accord
`ing to the voltage between the source and the drain of
`the transistor 27. It controls the power operating ranges
`of the switch mode power supply unit 7 via the wire C
`
`40
`
`45
`
`60
`
`65
`
`

`

`5,144,544
`5
`and by means of the variable voltage across the resistor
`37.
`Here this voltage is positive and varies upwards from
`0 V. It is used to vary the switching duty cycle imposed
`by the device 15 by means of the transistor 16.
`If the terminal 1 is designed so that it can be con
`nected to the link 4 when the latter is in service and
`consequently live it is important that the terminal
`should not begin to draw electrical power over the link
`until it is connected to all four wires of the link, for the
`reasons explained in the preamble.
`To this end when the terminal 1 is powered up via the
`link 4 the time-delay circuit comprising the capacitor 30
`and the resistor 31 delays the increase in voltage be
`tween the grid and the source of the transistor 27 while
`the capacitor 30 is charging, the transistor 35 turns on
`and enables the capacitor 39 to charge and turn off the
`transistor 16.
`The power transmitted by the link 4 then reaches
`only as far as the transformer 21 and the circuits on the
`output side of this transformer are not fed with power.
`When the capacitors have charged the transistor 27 is
`turned on and this turns off the transistor 35 so that the
`capacitor 39 discharges slowly through the resistors 36
`25
`and 37 to ensure progressive starting of switch mode
`operation by the circuit 7.
`The transistor 35 prevents switch mode operation
`when current limiting is applied.
`The diode 40 protects the transistors 27 and 28
`against reverse currents from the capacitors 24 and 25
`under any conditions likely to lead to the rapid dis
`charging of these.
`We claim:
`1. A power feed system for a terminal which is at least
`partly fed by a telephone transmission and power sup’
`ply link, said system comprising:
`a power converter type switch mode power supply
`unit connected to said link;
`a regulator connected to an input of said power sup
`ply unit and including a current limiter through
`which said terminal is at least partly fed by said
`link;
`means for progressively starting up said power sup
`ply unit when said terminal is powered up via said
`45
`link, by temporarily delaying the supply of power
`
`6
`to the terminal by the switch mode power supply
`unit.
`2. Power feed system according to claim 1, characteri
`ized in that the temporary delaying of the supply of
`power is provided by a means for temporarily delaying
`the supply of power comprising said current limiter and
`a time-delay circuit comprising a capacitor and a resis
`tor in series between the grid and the source of said
`MOS transistor, and a second capacitor connected be
`tween the source of the MOS transistor and a ground
`wire via a further transistor, said time-delay circuit
`turning off a switch mode transistor of the switch mode
`power supply unit during charging of the second capac
`itor when the terminal is powered up via the link.
`3. A power feed system for a terminal which is at least
`partly fed by a telephone transmission and power sup
`ply link, said system comprising:
`a power converter type switch mode power supply
`unit connected to said link;
`a regulator connected to an input of said power sup
`ply unit, said regulator comprising
`an MOS transistor having a grid and having a
`source connected to a positive power feed wire
`of the terminal, said MOS transistor monitoring
`the continuity of said positive power feed wire
`according to the signal applied to its grid,
`a resistor divider bridge for biasing said grid of said
`MOS transistor, said bridge comprising plural
`resistors connected between the positive power
`feed wire and a ground wire and having an inter
`mediate point to which said grid is connected,
`and
`a current limiter through which said terminal is at
`least partly fed by said link, said current limiter
`comprising a PNP transistor having a base, a
`collector connected to said grid, and an emitter
`connected via a low-value resistor to said base
`and to said source of said MOS transistor; and
`means for progressively starting up said power sup
`ply unit when said terminal is powered up via said
`link.
`4. A power feed system according to claim 3, wherein
`said base of said PNP transistor is connected to said
`positive power feed wire upstream of said MOS transis
`tOI'.
`
`ttttt
`
`15
`
`20
`
`35
`
`40
`
`55
`
`65
`
`